TY - JOUR A1 - Kannan, Krishna A1 - Kanabar, Pinal A1 - Schryer, David A1 - Florin, Tanja A1 - Oh, Eugene A1 - Bahroos, Neil A1 - Tenson, Tanel A1 - Weissman, Jonathan S. A1 - Mankin, Alexander S. T1 - The general mode of translation inhibition by macrolide antibiotics JF - Proceedings of the National Academy of Sciences of the United States of America KW - ribosome KW - antibiotics KW - macrolides KW - translation KW - peptidyl transferase Y1 - 2014 U6 - https://doi.org/10.1073/pnas.1417334111 SN - 0027-8424 VL - 111 IS - 45 SP - 15958 EP - 15963 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Scheiner, Ricarda A1 - Kulikovskaja, Leonora A1 - Thamm, Markus T1 - The honey bee tyramine receptor AmTYR1 and division of foraging labour JF - The journal of experimental biology N2 - Honey bees display a fascinating division of labour among foragers. While some bees solely collect pollen, others only collect nectar. It is assumed that individual differences in sensory response thresholds are at the basis of this division of labour. Biogenic amines and their receptors are important candidates for regulating the division of labour, because they can modulate sensory response thresholds. Here, we investigated the role of the honey bee tyramine receptor AmTYR1 in regulating the division of foraging labour. We report differential splicing of the Amtyr1 gene and show differential gene expression of one isoform in the suboesophageal ganglion of pollen and nectar foragers. This ganglion mediates gustatory inputs. These findings imply a role for the honey bee tyramine receptor in regulating the division of foraging labour, possibly through the suboesophageal ganglion. KW - Splicing KW - Tyramine KW - Gene expression KW - Pollen KW - Nectar KW - Biogenic amines Y1 - 2014 U6 - https://doi.org/10.1242/jeb.098475 SN - 0022-0949 SN - 1477-9145 VL - 217 IS - 8 SP - 1215 EP - 1217 PB - Company of Biologists Limited CY - Cambridge ER - TY - JOUR A1 - Hermanussen, Michael A1 - Alt, Christoph A1 - Staub, Kaspar A1 - Aßmann, Christian A1 - Groth, Detlef T1 - The impact of physical connectedness on body height in Swiss conscripts JF - Journal of biological and clinical anthropology : Anthropologischer Anzeiger ; Mitteilungsorgan der Gesellschaft für Anthropologie N2 - Background: Human populations differ in height. Recent evidence suggests that social networks play an important role in the regulation of adolescent growth and adult height. We further investigated the effect of physical connectedness on height. Material and methods: We considered Switzerland as a geographic network with 169 nodes (district capitals) and 335 edges (connecting roads) and studied effects of connectedness on height in Swiss conscript from 1884-1891, 1908-1910, and 2004-2009. We also created exponential-family random graph models to separate possible unspecific effects of geographic vicinity. Results: In 1884-1891, in 1908-1910, and in 2004-2009, 1st, 2nd and 3rd order neighboring districts significantly correlate in height (p<0.01). The correlations depend on the order of connectedness, they decline with increasing distance. Short stature districts tend to have short, tall stature districts tend to have tall neighbors. Random network analyses suggest direct road effects on height. Whereas in 1884-1891, direct road effects were only visible between 1st order neighbors, direct road effects extended to 2nd and 3rd in 1908-1910, and in 2004-2009, also to 4th order neighbors, and might reflect historic improvements in transportation. The spatial correlations did not significantly change when height was controlled for goiter (1884-1889) and for median per capita income (2006), suggesting direct road effects also in goiter-allowed-for height and income-allowed-for height. Conclusion: Height in a district depends on height of physically connected neighboring districts. The association decreases with increasing distance in the net. The present data suggest that people can be short because their neighbors are short; or tall because their neighbors are tall (community effect on growth). Psycho-biological effects seem to control growth and development within communities that go far beyond our current understanding of growth regulation. KW - body height KW - connectedness KW - community effect KW - conscripts KW - Switzerland Y1 - 2014 U6 - https://doi.org/10.1127/0003-5548/2014/0466 SN - 0003-5548 VL - 71 IS - 4 SP - 313 EP - 327 PB - Schweizerbart CY - Stuttgart ER - TY - JOUR A1 - Eccard, Jana A1 - Liesenjohann, Thilo T1 - The importance of predation risk and missed opportunity costs for context-dependent foraging patterns JF - PLoS one N2 - Correct assessment of risks and costs of foraging is vital for the fitness of foragers. Foragers should avoid predation risk and balance missed opportunities. In risk-heterogeneous landscapes animals prefer safer locations over riskier, constituting a landscape of fear. Risk-uniform landscapes do not offer this choice, all locations are equally risky. Here we investigate the effects of predation risk in patches, travelling risk between patches, and missed social opportunities on foraging decisions in risk-uniform and risk-heterogeous landscapes. We investigated patch leaving decisions of 20 common voles (M. arvalis) in three experimental landscapes: safe risk-uniform, risky risk-uniform and risk-heterogeneous. We varied both the predation risk level and the predation risk distribution between two patches experimentally and in steps, assuming that our manipulation consequently yield different distributions and levels of risk while foraging, risk while travelling, and costs of missed, social opportunities (MSOCs). We measured mean GUDs (giving-up density of food left in the patch) for both patches as a measure of foraging gain, and delta GUD, the differences among patches, as a measure of the spatial distribution of foraging effort over a period of six hours. Distribution of foraging effort was most even in the safe risk-uniform landscapes and least even in the risk-heterogeneous landscape, with risky risk-uniform landscapes in between. Foraging gain was higher in the safe than in the two riskier landscapes (both uniform and heterogeneous). Results supported predictions for the effects of risk in foraging patches and while travelling between patches, however predictions for the effects of missed social opportunities were not met in this short term experiment. Thus, both travelling and foraging risk contribute to distinct patterns observable high risk, risk-uniform landscapes. Y1 - 2014 U6 - https://doi.org/10.1371/journal.pone.0094107 SN - 1932-6203 VL - 9 IS - 5 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Svenning, Jens-Christian A1 - Gravel, Dominique A1 - Holt, Robert D. A1 - Schurr, Frank Martin A1 - Thuiller, Wilfried A1 - Muenkemueller, Tamara A1 - Schiffers, Katja H. A1 - Dullinger, Stefan A1 - Edwards, Thomas C. A1 - Hickler, Thomas A1 - Higgins, Steven I. A1 - Nabel, Julia E. M. S. A1 - Pagel, Jörn A1 - Normand, Signe T1 - The influence of interspecific interactions on species range expansion rates JF - Ecography : pattern and diversity in ecology ; research papers forum Y1 - 2014 U6 - https://doi.org/10.1111/j.1600-0587.2013.00574.x SN - 0906-7590 SN - 1600-0587 VL - 37 IS - 12 SP - 1198 EP - 1209 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Hall, James A1 - Reschke, Stefan A1 - Cao, Hongnan A1 - Leimkühler, Silke A1 - Hille, Russ T1 - The reductive half-reaction of xanthine dehydrogenase from rhodobacter capsulatus the role of GLU(232) in catalysis JF - The journal of biological chemistry N2 - Background: Kinetic characterization of wild-type xanthine dehydrogenase and variants. Results: Comparison of the pH dependence of both k(red) and k(red)/K-d, as well as k(cat) and k(cat)/K-m. Conclusion: Ionized Glu(232) of wild-type enzyme plays an important role in catalysis by discriminating against the monoanionic form of xanthine. Significance: Examining the contributions of Glu(232) to catalysis is essential for understanding the mechanism of xanthine dehydrogenase. The kinetic properties of an E232Q variant of the xanthine dehydrogenase from Rhodobacter capsulatus have been examined to ascertain whether Glu(232) in wild-type enzyme is protonated or unprotonated in the course of catalysis at neutral pH. We find that k(red), the limiting rate constant for reduction at high [xanthine], is significantly compromised in the variant, a result that is inconsistent with Glu(232) being neutral in the active site of the wild-type enzyme. A comparison of the pH dependence of both k(red) and k(red)/K-d from reductive half-reaction experiments between wild-type and enzyme and the E232Q variant suggests that the ionized Glu(232) of wild-type enzyme plays an important role in catalysis by discriminating against the monoanionic form of substrate, effectively increasing the pK(a) of substrate by two pH units and ensuring that at physiological pH the neutral form of substrate predominates in the Michaelis complex. A kinetic isotope study of the wild-type R. capsulatus enzyme indicates that, as previously determined for the bovine and chicken enzymes, product release is principally rate-limiting in catalysis. The disparity in rate constants for the chemical step of the reaction and product release, however, is not as great in the bacterial enzyme as compared with the vertebrate forms. The results indicate that the bacterial and bovine enzymes catalyze the chemical step of the reaction to the same degree and that the faster turnover observed with the bacterial enzyme is due to a faster rate constant for product release than is seen with the vertebrate enzyme. KW - Enzyme Kinetics KW - Glutamate KW - Glutamine KW - Isotope Effect KW - Ultraviolet-visible Spectroscopy (UV-visible Spectroscopy) KW - Xanthine KW - Xanthine Dehydrogenase KW - Xanthine Oxidase KW - pH Dependence Y1 - 2014 U6 - https://doi.org/10.1074/jbc.M114.603456 SN - 0021-9258 SN - 1083-351X VL - 289 IS - 46 SP - 32121 EP - 32130 PB - American Society for Biochemistry and Molecular Biology CY - Bethesda ER - TY - JOUR A1 - Lin, Yue A1 - Huth, Franka A1 - Berger, Uta A1 - Grimm, Volker T1 - The role of belowground competition and plastic biomass allocation in altering plant mass-density relationships JF - Oikos Y1 - 2014 U6 - https://doi.org/10.1111/j.1600-0706.2013.00921.x SN - 0030-1299 SN - 1600-0706 VL - 123 IS - 2 SP - 248 EP - 256 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - French, Alice S. A1 - Simcock, Kerry L. A1 - Rolke, Daniel A1 - Gartside, Sarah E. A1 - Blenau, Wolfgang A1 - Wright, Geraldine A. T1 - The role of serotonin in feeding and gut contractions in the honeybee JF - Journal of insect physiology KW - Honeybee KW - Apis mellifera KW - Serotonin KW - 5-HT KW - 5-HT receptor KW - Gut contractions Y1 - 2014 U6 - https://doi.org/10.1016/j.jinsphys.2013.12.005 SN - 0022-1910 SN - 1879-1611 VL - 61 SP - 8 EP - 15 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Yarman, Aysu A1 - Schulz, Christopher A1 - Sygmund, Cristoph A1 - Ludwig, Roland A1 - Gorton, Lo A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Third generation ATP sensor with enzymatic analyte recycling JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - For the first time the direct electron transfer of an enzyme - cellobiose dehydrogenase, CDH - has been coupled with the hexokinase catalyzed competition for glucose in a sensor for ATP. To enhance the signal output for ATP, pyruvate kinase was coimmobilized to recycle ADP by the phosphoenolpyruvate driven reaction. The new sensor overcomes the limit of 1:1 stoichiometry of the sequential or competitive conversion of ATP by effective enzymatic recycling of the analyte. The anodic oxidation of the glucose converting CDH proceeds at electrode potentials below 0 mV vs. Ag vertical bar AgCl thus potentially interfering substances like ascorbic acid or catecholamines do not influence the measuring signal. The combination of direct electron transfer of CDH with the enzymatic recycling results in an interference-free and oxygen-independent measurement of ATP in the lower mu molar concentration range with a lower limit of detection of 63.3 nM (S/N=3). KW - ATP KW - Third generation sensor KW - Enzymatic recycling KW - Cellobiose dehydrogenase KW - Hexokinase KW - Pyruvate kinase Y1 - 2014 U6 - https://doi.org/10.1002/elan.201400231 SN - 1040-0397 SN - 1521-4109 VL - 26 IS - 9 SP - 2043 EP - 2048 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Martin-Creuzburg, Dominik A1 - Oexle, Sarah A1 - Wacker, Alexander T1 - Thresholds for sterol-limited growth of Daphnia magna: A comparative approach using 10 different sterols JF - Journal of chemical ecology N2 - Arthropods are incapable of synthesizing sterols de novo and thus require a dietary source to cover their physiological demands. The most prominent sterol in animal tissues is cholesterol, which is an indispensable structural component of cell membranes and serves as precursor for steroid hormones. Instead of cholesterol, plants and algae contain a variety of different phytosterols. Consequently, herbivorous arthropods have to metabolize dietary phytosterols to cholesterol to meet their requirements for growth and reproduction. Here, we investigated sterol-limited growth responses of the freshwater herbivore Daphnia magna by supplementing a sterol-free diet with increasing amounts of 10 different phytosterols and comparing thresholds for sterol-limited growth. In addition, we analyzed the sterol composition of D. magna to explore sterol metabolic constraints and bioconversion capacities. We show that dietary phytosterols strongly differ in their potential to support somatic growth of D. magna. The dietary threshold concentrations obtained by supplementing the different sterols cover a wide range (3.5-34.4 mu g mg C-1) and encompass the one for cholesterol (8.9 mu g mg C-1), indicating that certain phytosterols are more efficient in supporting somatic growth than cholesterol (e.g., fucosterol, brassicasterol) while others are less efficient (e.g., dihydrocholesterol, lathosterol). The dietary sterol concentration gradients revealed that the poor quality of particular sterols can be alleviated partially by increasing dietary concentrations, and that qualitative differences among sterols are most pronounced at low to moderate dietary concentrations. We infer that the dietary sterol composition has to be considered in zooplankton nutritional ecology to accurately assess potential sterol limitations under field conditions. KW - Cholesterol KW - Daphnia KW - Food quality KW - Nutrition KW - Phytosterols KW - Sterols Y1 - 2014 U6 - https://doi.org/10.1007/s10886-014-0486-1 SN - 0098-0331 SN - 1573-1561 VL - 40 IS - 9 SP - 1039 EP - 1050 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Sutton, Christopher A1 - Körzdörfer, Thomas A1 - Coropceanu, Veaceslav A1 - Bredas, Jean-Luc T1 - Toward a robust quantum-chemical description of organic mixed-valence systems JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - The electronic coupling between redox sites in mixed-valence systems has attracted the interest of the chemistry community for a long time. Many computational studies have focused on trying to determine its magnitude as a function of the nature of the redox sites and of the bridge(s) between them. However, in most instances, the quantum-chemical methodologies that have been employed suffer from intrinsic errors that lead to either an overlocalized or an overdelocalized character of the electronic structure. These deficiencies prevent an accurate depiction of the degree of charge (de)localization in the system and, as a result, of the extent of electronic coupling. Here we use nonempirically tuned long-range corrected density functional theory and show that it provides a robust, efficient approach to characterize organic mixed-valence systems. We first demonstrate the performance of this approach via a study of representative Robin-Day class-II (localized) and class-III (delocalized) complexes. We then examine a borderline class-II/class-III complex, which had proven difficult to describe accurately with standard density functional theory and Hartree-Fock methods. Y1 - 2014 U6 - https://doi.org/10.1021/jp410461v SN - 1932-7447 VL - 118 IS - 8 SP - 3925 EP - 3934 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmitz-Hertzberg, Sebastian-Tim A1 - Liese, Rick A1 - Terjung, Carsten A1 - Bier, Frank Fabian T1 - Towards a smart encapsulation system for small-sized electronic devices: a new approach JF - International journal of polymer science N2 - Miniaturized analytical chip devices like biosensors nowadays provide assistance in highly diverse fields of application such as point-of-care diagnostics and industrial bioprocess engineering. However, upon contact with fluids, the sensor requires a protective shell for its electrical components that simultaneously offers controlled access for the target analytes to the measuring units. We therefore developed a capsule that comprises a permeable and a sealed compartment consisting of variable polymers such as biocompatible and biodegradable polylactic acid (PLA) for medical applications or more economical polyvinyl chloride (PVC) and polystyrene (PS) polymers for bioengineering applications. Production of the sealed capsule compartments was performed by heat pressing of polymer pellets placed in individually designable molds. Controlled permeability of the opposite compartments was achieved by inclusion of NaCl inside the polymer matrix during heat pressing, followed by its subsequent release in aqueous solution. Correlating diffusion rates through the so made permeable capsule compartments were quantified for preselected model analytes: glucose, peroxidase, and polystyrene beads of three different diameters (1.4 mu m, 4.2 mu m, and 20.0 mu m). In summary, the presented capsule system turned out to provide sufficient shelter for small-sized electronic devices and gives insight into its potential permeability for defined substances of analytical interest. Y1 - 2014 U6 - https://doi.org/10.1155/2014/713603 SN - 1687-9422 SN - 1687-9430 PB - Hindawi Publishing Corp. CY - New York ER - TY - JOUR A1 - Grimm, Volker A1 - Augusiak, Jacqueline A1 - Focks, Andreas A1 - Frank, Beatrice M. A1 - Gabsi, Faten A1 - Johnston, Alice S. A. A1 - Liu, Chun A1 - Martin, Benjamin T. A1 - Meli, Mattia A1 - Radchuk, Viktoriia A1 - Thorbek, Pernille A1 - Railsback, Steven Floyd T1 - Towards better modelling and decision support: Documenting model development, testing, and analysis using TRACE JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - The potential of ecological models for supporting environmental decision making is increasingly acknowledged. However, it often remains unclear whether a model is realistic and reliable enough. Good practice for developing and testing ecological models has not yet been established. Therefore, TRACE, a general framework for documenting a model's rationale, design, and testing was recently suggested. Originally TRACE was aimed at documenting good modelling practice. However, the word 'documentation' does not convey TRACE's urgency. Therefore, we re-define TRACE as a tool for planning, performing, and documenting good modelling practice. TRACE documents should provide convincing evidence that a model was thoughtfully designed, correctly implemented, thoroughly tested, well understood, and appropriately used for its intended purpose. TRACE documents link the science underlying a model to its application, thereby also linking modellers and model users, for example stakeholders, decision makers, and developers of policies. We report on first experiences in producing TRACE documents. We found that the original idea underlying TRACE was valid, but to make its use more coherent and efficient, an update of its structure and more specific guidance for its use are needed. The updated TRACE format follows the recently developed framework of model 'evaludation': the entire process of establishing model quality and credibility throughout all stages of model development, analysis, and application. TRACE thus becomes a tool for planning, documenting, and assessing model evaludation, which includes understanding the rationale behind a model and its envisaged use. We introduce the new structure and revised terminology of TRACE and provide examples. (C) 2014 Elsevier B.V. All rights reserved. KW - Standardization KW - Good modelling practice KW - Risk assessment KW - Decision support Y1 - 2014 U6 - https://doi.org/10.1016/j.ecolmodel.2014.01.018 SN - 0304-3800 SN - 1872-7026 VL - 280 SP - 129 EP - 139 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Lu, Dandan A1 - Wang, Ting A1 - Persson, Staffan A1 - Müller-Röber, Bernd A1 - Schippers, Jos H. M. T1 - Transcriptional control of ROS homeostasis by KUODA1 regulates cell expansion during leaf development JF - Nature Communications N2 - The final size of an organism, or of single organs within an organism, depends on an intricate coordination of cell proliferation and cell expansion. Although organism size is of fundamental importance, the molecular and genetic mechanisms that control it remain far from understood. Here we identify a transcription factor, KUODA1 (KUA1), which specifically controls cell expansion during leaf development in Arabidopsis thaliana. We show that KUA1 expression is circadian regulated and depends on an intact clock. Furthermore, KUA1 directly represses the expression of a set of genes encoding for peroxidases that control reactive oxygen species (ROS) homeostasis in the apoplast. Disruption of KUA1 results in increased peroxidase activity and smaller leaf cells. Chemical or genetic interference with the ROS balance or peroxidase activity affects cell size in a manner consistent with the identified KUA1 function. Thus, KUA1 modulates leaf cell expansion and final organ size by controlling ROS homeostasis. Y1 - 2014 U6 - https://doi.org/10.1038/ncomms4767 SN - 2041-1723 VL - 5 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Gracceva, Giulia A1 - Herde, Antje A1 - Groothuis, Ton G. G. A1 - Koolhaas, Jaap M. A1 - Palme, Rupert A1 - Eccard, Jana T1 - Turning shy on a winter's day: Effects of season on personality and stress response in Microtus arvalis JF - Ethology N2 - Animal personalities are by definition stable over time, but to what extent they may change during development and in adulthood to adjust to environmental change is unclear. Animals of temperate environments have evolved physiological and behavioural adaptations to cope with the cyclic seasonal changes. This may also result in changes in personality: suites of behavioural and physiological traits that vary consistently among individuals. Winter, typically the adverse season challenging survival, may require individuals to have shy/cautious personality, whereas during summer, energetically favourable to reproduction, individuals may benefit from a bold/risk-taking personality. To test the effects of seasonal changes in early life and in adulthood on behaviours (activity, exploration and anxiety), body mass and stress response, we manipulated the photoperiod and quality of food in two experiments to simulate the conditions of winter and summer. We used the common voles (Microtus arvalis) as they have been shown to display personality based on behavioural consistency over time and contexts. Summer-born voles allocated to winter conditions at weaning had lower body mass, a higher corticosterone increase after stress and a less active, more cautious behavioural phenotype in adulthood compared to voles born in and allocated to summer conditions. In contrast, adult females only showed plasticity in stress-induced corticosterone levels, which were higher in the animals that were transferred to the winter conditions than to those staying in summer conditions. These results suggest a sensitive period for season-related behavioural plasticity in which juveniles shift over the bold-shy axis. KW - animal personality KW - seasonal environment KW - photoperiod KW - juvenile plasticity KW - corticosterone Y1 - 2014 U6 - https://doi.org/10.1111/eth.12246 SN - 0179-1613 SN - 1439-0310 VL - 120 IS - 8 SP - 753 EP - 767 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Schatz, J. A1 - Ohlendorf, B. A1 - Busse, P. A1 - Pelz, G. A1 - Dolch, D. A1 - Teubner, J. A1 - Encarnacao, Jorge A. A1 - Muehle, Ralf -Udo A1 - Fischer, M. A1 - Hoffmann, B. A1 - Kwasnitschka, L. A1 - Balkema-Buschmann, Anne A1 - Mettenleiter, Thomas Christoph A1 - Mueller, T. A1 - Freuling, C. M. T1 - Twenty years of active bat rabies surveillance in Germany BT - a detailed analysis and future perspectives JF - Epidemiology and infection N2 - In Germany, active bat rabies surveillance was conducted between 1993 and 2012. A total of 4546 oropharyngeal swab samples from 18 bat species were screened for the presence of EBLV-1- , EBLV-2- and BBLV-specific RNA. Overall, 0 center dot 15% of oropharyngeal swab samples tested EBLV-1 positive, with the majority originating from Eptesicus serotinus. Interestingly, out of seven RT-PCR-positive oropharyngeal swabs subjected to virus isolation, viable virus was isolated from a single serotine bat (E. serotinus). Additionally, about 1226 blood samples were tested serologically, and varying virus neutralizing antibody titres were found in at least eight different bat species. The detection of viral RNA and seroconversion in repeatedly sampled serotine bats indicates long-term circulation of the virus in a particular bat colony. The limitations of random-based active bat rabies surveillance over passive bat rabies surveillance and its possible application of targeted approaches for future research activities on bat lyssavirus dynamics and maintenance are discussed. KW - surveillance KW - epidemiology KW - Bat rabies KW - lyssavirus Y1 - 2014 U6 - https://doi.org/10.1017/S0950268813002185 SN - 0950-2688 SN - 1469-4409 VL - 142 IS - 6 SP - 1155 EP - 1166 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Meli, Mattia A1 - Palmqvist, Annemette A1 - Forbes, Valery E. A1 - Groeneveld, Jürgen A1 - Grimm, Volker T1 - Two pairs of eyes are better than one: Combining individual-based and matrix models for ecological risk assessment of chemicals JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Current chemical risk assessment procedures may result in imprecise estimates of risk due to sometimes arbitrary simplifying assumptions. As a way to incorporate ecological complexity and improve risk estimates, mechanistic effect models have been recommended. However, effect modeling has not yet been extensively used for regulatory purposes, one of the main reasons being uncertainty about which model type to use to answer specific regulatory questions. We took an individual-based model (IBM), which was developed for risk assessment of soil invertebrates and includes avoidance of highly contaminated areas, and contrasted it with a simpler, more standardized model, based on the generic metapopulation matrix model RAMAS. In the latter the individuals within a sub-population are not treated as separate entities anymore and the spatial resolution is lower. We explored consequences of model aggregation in terms of assessing population-level effects for different spatial distributions of a toxic chemical. For homogeneous contamination of the soil, we found good agreement between the two models, whereas for heterogeneous contamination, at different concentrations and percentages of contaminated area, RAMAS results were alternatively similar to IBM results with and without avoidance, and different food levels. This inconsistency is explained on the basis of behavioral responses that are included in the IBM but not in RAMAS. Overall, RAMAS was less sensitive than the IBM in detecting population-level effects of different spatial patterns of exposure. We conclude that choosing the right model type for risk assessment of chemicals depends on whether or not population-level effects of small-scale heterogeneity in exposure need to be detected. We recommend that if in doubt, both model types should be used and compared. Describing both models following the same standard format, the ODD protocol, makes them equally transparent and understandable. The simpler model helps to build up trust for the more complex model and can be used for more homogeneous exposure patterns. The more complex model helps detecting and understanding the limitations of the simpler model and is needed to ensure ecological realism for more complex exposure scenarios. (C) 2013 Elsevier B.V. All rights reserved. KW - Ecotoxicology KW - Folsomia candida KW - Mechanistic effect models KW - Soil invertebrates Y1 - 2014 U6 - https://doi.org/10.1016/j.ecolmodel.2013.07.027 SN - 0304-3800 SN - 1872-7026 VL - 280 SP - 40 EP - 52 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rajasundaram, Dhivyaa A1 - Runavot, Jean-Luc A1 - Guo, Xiaoyuan A1 - Willats, William G. T. A1 - Meulewaeter, Frank A1 - Selbig, Joachim T1 - Understanding the relationship between cotton fiber properties and non-cellulosic cell wall polysaccharides JF - PLoS one N2 - A detailed knowledge of cell wall heterogeneity and complexity is crucial for understanding plant growth and development. One key challenge is to establish links between polysaccharide-rich cell walls and their phenotypic characteristics. It is of particular interest for some plant material, like cotton fibers, which are of both biological and industrial importance. To this end, we attempted to study cotton fiber characteristics together with glycan arrays using regression based approaches. Taking advantage of the comprehensive microarray polymer profiling technique (CoMPP), 32 cotton lines from different cotton species were studied. The glycan array was generated by sequential extraction of cell wall polysaccharides from mature cotton fibers and screening samples against eleven extensively characterized cell wall probes. Also, phenotypic characteristics of cotton fibers such as length, strength, elongation and micronaire were measured. The relationship between the two datasets was established in an integrative manner using linear regression methods. In the conducted analysis, we demonstrated the usefulness of regression based approaches in establishing a relationship between glycan measurements and phenotypic traits. In addition, the analysis also identified specific polysaccharides which may play a major role during fiber development for the final fiber characteristics. Three different regression methods identified a negative correlation between micronaire and the xyloglucan and homogalacturonan probes. Moreover, homogalacturonan and callose were shown to be significant predictors for fiber length. The role of these polysaccharides was already pointed out in previous cell wall elongation studies. Additional relationships were predicted for fiber strength and elongation which will need further experimental validation. Y1 - 2014 U6 - https://doi.org/10.1371/journal.pone.0112168 SN - 1932-6203 VL - 9 IS - 11 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Köhler, Yvonne A1 - Luther, Eva Maria A1 - Meyer, Sören A1 - Schwerdtle, Tanja A1 - Dringen, Ralf T1 - Uptake and toxicity of arsenite and arsenate in cultured brain astrocytes JF - Journal of trace elements in medicine and biology N2 - Inorganic arsenicals are environmental toxins that have been connected with neuropathies and impaired cognitive functions. To investigate whether such substances accumulate in brain astrocytes and affect their viability and glutathione metabolism, we have exposed cultured primary astrocytes to arsenite or arsenate. Both arsenicals compromised the cell viability of astrocytes in a time- and concentration-dependent manner. However, the early onset of cell toxicity in arsenite-treated astrocytes revealed the higher toxic potential of arsenite compared with arsenate. The concentrations of arsenite and arsenate that caused within 24 h half-maximal release of the cytosolic enzyme lactate dehydrogenase were around 0.3 mM and 10 mM, respectively. The cellular arsenic contents of astrocytes increased rapidly upon exposure to arsenite or arsenate and reached after 4 h of incubation almost constant steady state levels. These levels were about 3-times higher in astrocytes that had been exposed to a given concentration of arsenite compared with the respective arsenate condition. Analysis of the intracellular arsenic species revealed that almost exclusively arsenite was present in viable astrocytes that had been exposed to either arsenate or arsenite. The emerging toxicity of arsenite 4 h after exposure was accompanied by a loss in cellular total glutathione and by an increase in the cellular glutathione disulfide content. These data suggest that the high arsenite content of astrocytes that had been exposed to inorganic arsenicals causes an increase in the ratio of glutathione disulfide to glutathione which contributes to the toxic potential of these substances. KW - Arsenic KW - Astrocytes KW - GSH KW - Metabolism KW - Toxicity Y1 - 2014 U6 - https://doi.org/10.1016/j.jtemb.2014.04.007 SN - 0946-672X VL - 28 IS - 3 SP - 328 EP - 337 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Reinecke, Jennifer A1 - Klemm, Gunther A1 - Heinken, Thilo T1 - Vegetation change and homogenization of species composition in temperate nutrient deficient scots pine forests after 45 yr JF - Journal of vegetation science N2 - QuestionDoes eutrophication drive vegetation change in pine forests on nutrient deficient sites and thus lead to the homogenization of understorey species composition? LocationForest area (1600ha) in the Lower Spreewald, Brandenburg, Germany. MethodsResurvey of 77 semi-permanent plots after 45yr, including vascular plants, bryophytes and ground lichens. We applied multidimensional ordination of species composition, dissimilarity indices, mean Ellenberg indicator values and the concept of winner/loser species to identify vegetation change between years. Differential responses along a gradient of nutrient availability were analysed on the basis of initial vegetation type, reflecting topsoil N availability of plots. ResultsSpecies composition changed strongly and overall shifted towards higher N and slightly lower light availability. Differences in vegetation change were related to initial vegetation type, with strongest compositional changes in the oligotrophic forest type, but strongest increase of nitrophilous species in the mesotrophic forest type. Despite an overall increase in species number, species composition was homogenized between study years due to the loss of species (mainly ground lichens) on the most oligotrophic sites. ConclusionsThe response to N enrichment is confounded by canopy closure on the N-richest sites and probably by water limitation on N-poorest sites. The relative importance of atmospheric N deposition in the eutrophication effect is difficult to disentangle from natural humus accumulation after historical litter raking. However, the profound differences in species composition between study years across all forest types suggest that atmospheric N deposition contributes to the eutrophication, which drives understorey vegetation change and biotic homogenization in Central European Scots pine forests on nutrient deficient sites. KW - Eutrophication KW - Litter raking KW - Canopy closure KW - Cryptogams KW - Species diversity Y1 - 2014 U6 - https://doi.org/10.1111/jvs.12069 SN - 1100-9233 SN - 1654-1103 VL - 25 IS - 1 SP - 113 EP - 121 PB - Wiley-Blackwell CY - Hoboken ER -