A dynamic mass balance model for phosphorus fluxes and concentrations in coastal areas

This paper presents a general, process-based mass balance model (CoastMab) for total phosphorus (TP) in defined coastal areas (at the ecosystem scale). The model is based on ordinary differential equations and calculates inflow, outflow and internal fluxes on a monthly basis. It consists of four compartments: surface water, deep water, erosion/transportation areas for fine sediments and accumulation areas for fine sediments. The separation between surface water and deep water is not done based on water temperature, but on sedimentological criteria instead (from the theoretical wave base). There are algorithms for all major internal TP fluxes (sedimentation, resuspension, diffusion, mixing and burial). Validations were performed using data from 21 different Baltic coastal areas. The results show that the model predicts monthly TP in water and chlorophyll a very well (generally within the uncertainty bands of the empirical data). The model has also been put through sensitivity tests, which show that the most important factor regulating the predictions of the model is generally the TP concentration in the sea beyond the coast. The model is simple to apply, since all driving variables may be accessed from maps or monitoring programs. The driving variables include coastal area, section area (between the defined coastal area and the adjacent sea), mean and maximum depths, latitude (used to predict water temperatures, stratification and mixing), salinity and TP concentration in the sea. Many of the model structures are general and could be used for areas other than those included in this study, e.g., for open coasts, estuaries or tidal coasts, as well as for other substances than phosphorus.     

Effects of methotrexate on the viscoelastic properties of single cells probed by atomic force microscopy

Methotrexate is a commonly used anti-cancer chemotherapy drug. Cellular mechanical properties are fundamental parameters that reflect the physiological state of a cell. However, so far the role of cellular mechanical properties in the actions of methotrexate is still unclear. In recent years, probing the behaviors of single cells with the use of atomic force microscopy (AFM) has contributed much to the field of cell biomechanics. In this work, with the use of AFM, the effects of methotrexate on the viscoelastic properties of four types of cells were quantitatively investigated. The inhibitory and cytotoxic effects of methotrexate on the proliferation of cells were observed by optical and fluorescence microscopy. AFM indenting was used to measure the changes of cellular viscoelastic properties (Young’s modulus and relaxation time) by using both conical tip and spherical tip, quantitatively showing that the stimulation of methotrexate resulted in a significant decrease of both cellular Young’s modulus and relaxation times. The morphological changes of cells induced by methotrexate were visualized by AFM imaging. The study improves our understanding of methotrexate action and offers a novel way to quantify drug actions at the single-cell level by measuring cellular viscoelastic properties, which may have potential impacts on developing label-free methods for drug evaluation.     

Solid Phase Synthesis of Phosphopeptides Incorporating 2,2-Dimethyloxazolidine Pseudoproline Analogs: Evidence for <Emphasis Type="Italic">trans</Emphasis> Leu-Pro Peptide Bonds in Stat3 Inhibitors

To answer the question of whether the conformation of the Leu-Pro bond is cis or trans in Ac-pTyr-Leu-Pro-Gln-Thr-Val-NH₂ when complexed with the SH2 domain of Stat3, we substituted 2,2-dimethyloxazolidines derived from serine (Ser(Ψ^Me,Mepro)) and threonine (Thr(Ψ^Me,Mepro)) for proline. The 2,2-dimethyloxazolidine and 2,2-dimethylthiazolidine pseudoproline (ΨPro) analogs induce predominantly cis Xxx-ΨPro peptide bonds. As these ΨPro analogs are acid-labile, the phosphopeptides were synthesized using Fmoc-based SPPS using unprotected phosphotyrosine and 4-hydroxybenzoate as the linker that allowed release from the support by alkaline ammonolysis, conditions that kept the oxazolidine rings intact. Incorporation of Ser(Ψ^Me,Mepro) resulted in 69% cis Leu-ΨPro bond content in aqueous solution whereas that for Thr(Ψ^Me,Mepro) analog was 63%. Affinities for Stat3 were 3–5 fold lower than the lead compound and were inversely correlated with cis content. Thus we conclude that the Leu-Pro peptide bond is trans when the peptide is bound to Stat3.     

Division of labor of anthers in heterantherous plants: flexibility of bee pollen collection behavior may serve to keep plants honest

Heteranthery is thought to reflect a division of labor, with some anthers serving a pollinator-feeding function and others serving a pollinating function. Mutualism theory predicts that each participant should try to maximize the benefit it receives from its partner: plants should allocate more pollen to pollination, and pollinators should collect more pollen. Accordingly, plant and pollinator may engage in a ‘tug of war’ with respect to pollen from each anther type, resulting in incomplete division of labor. Here, we explored this idea by conducting a fully factorial manipulation of the availability of pollen in long and short anthers of staminate flowers of Solanum houstonii. We found the following: (1) Bumble bees (Bombus impatiens) preferred to sonicate (collect pollen from) short anthers over long anthers, consistent with a role as feeding and pollinating anthers, respectively; (2) Blocking short anther pores alone increased sonication of long anthers and resulted in collection of pollen from long anthers; (3) Blocking long anther pores alone did not influence sonication of short anthers; (4) The increase in sonication of long anthers, when short anther pores are blocked, was greater when pollen was available in long anthers; (5) Despite shifting sonication effort to long anthers, bees do not move their bodies closer to long anther pores where pollen could be collected more effectively; and (6) analysis of the growth of corbicular loads over time spent buzzing indicates that significant amounts of pollen are collected from long anthers as well as short anthers. We conclude that bees can flexibly increase pollen collection from pollinating anthers, but are constrained from fully exploiting this pollen. This results in checks and balances between plant and bee that may help maintain heteranthery.     

Functional expression of human pyruvate carboxylase for reduced lactic acid formation of Chinese hamster ovary cells (DG44)

To investigate the effect of human pyruvate carboxylase (hPC) on lactate formation in Chinese hamster ovary (CHO) cell lines, FLAG-tagged hPC was introduced into a dihydrofolate-deficient CHO cell line (DG44). Three clones expressing high levels of hPC, determined by Western blotting using an anti-FLAG monoclonal antibody, and a control cell line were established. Immunocytochemistry revealed that a substantial amount of expressed hPC protein was localized in the mitochondria of the cells. hPC expression did not impair cell proliferation. Rather, it improved cell viability at the end of adherent batch cultures with the serum-containing medium probably because of reduced lactate formation. Compared with control cells, specific lactate production rate of the three clones was decreased by 21–39%, which was because of a decreased specific glucose uptake rate and yield of lactate from glucose. Reduced lactate formation by hPC expression was also observed in suspension fed-batch cultures using a serum-free medium. Taken together, these results demonstrate that through the expression of the hPC enzyme, lactate formation in CHO cell culture can be efficiently reduced.     

Genetic and potential non-genetic benefits increase offspring fitness of polyandrous females in non-resource based mating system

Background  

The adaptive significance of female polyandry is currently under considerable debate. In non-resource based mating systems, indirect, i.e. genetic benefits have been proposed to be responsible for the fitness gain from polyandry. We studied the benefits of polyandry in the Arctic charr (Salvelinus alpinus) using an experimental design in which the material investments by the sires and maternal environmental effects were controlled.     

Key Elements in a Framework for Land Use Impact Assessment Within LCA (11 pp)

Background, Aim and Scope Land use by agriculture, forestry, mining, house-building or industry leads to substantial impacts, particularly on biodiversity and on soil quality as a supplier of life support functions. Unfortunately there is no widely accepted assessment method so far for land use impacts. This paper presents an attempt, within the UNEP-SETAC Life Cycle Initiative, to provide a framework for the Life Cycle Impact Assessment (LCIA) of land use. Materials and Methods: This framework builds from previous documents, particularly the SETAC book on LCIA (Lindeijer et al. 2002), developing essential issues such as the reference for occupation impacts; the impact pathways to be included in the analysis; the units of measure in the impact mechanism (land use interventions to impacts); the ways to deal with impacts in the future; and bio-geographical differentiation. Results: The paper describes the selected impact pathways, linking the land use elementary flows (occupation; transformation) and parameters (intensity) registered in the inventory (LCI) to the midpoint impact indicators and to the relevant damage categories (natural environment and natural resources). An impact occurs when the land properties are modified (transformation) and also when the current man-made properties are maintained (occupation). Discussion: The size of impact is the difference between the effect on land quality from the studied case of land use and a suitable reference land use on the same area (dynamic reference situation). The impact depends not only on the type of land use (including coverage and intensity) but is also heavily influenced by the bio-geographical conditions of the area. The time lag between the land use intervention and the impact may be large; thus land use impacts should be calculated over a reasonable time period after the actual land use finishes, at least until a new steady state in land quality is reached. Conclusions: Guidance is provided on the definition of the dynamic reference situation and on methods and time frame to assess the impacts occurring after the actual land use. Including the occupation impacts acknowledges that humans are not the sole users of land. Recommendations and Perspectives: The main damages affected by land use that should be considered by any method to assess land use impacts in LCIA are: biodiversity (existence value); biotic production potential (including soil fertility and use value of biodiversity); ecological soil quality (including life support functions of soil other than biotic production potential). Bio-geographical differentiation is required for land use impacts, because the same intervention may have different consequences depending on the sensitivity and inherent land quality of the environment where it occurs. For the moment, an indication of how such task could be done and likely bio-geographical parameters to be considered are suggested. The recommendation of indicators for the suggested impact categories is a matter of future research.     

Rebound effects of price differences

Goal, Scope and Background  Traditionally, comparative life cycle assessments (LCA) have not considered rebound effects, for instance in case of significant price differences among the compared products. No justifications have been made for this delimitation in scope. This article shows that price differences and the consequent effects of marginal consumer expenditure may influence the conclusions of comparative LCA significantly. We also show that considerations about rebound effects of price differences can be included in LCAs. Methods  The direct rebound effect of a price difference is marginal consumption. Based on statistical data on private consumption in different income groups (Statistics Denmark 2005a, 2005b), the present article provides an estimate of how an average Danish household will spend an additional 1 DKK for further consumer goods, when the household has gained money from choosing a cheaper product alternative. The approach is to use marginal income changes and the following changes in consumption patterns as an expression for marginal consumption. Secondly, the environmental impact potentials related to this marginal consumption are estimated by the use of environmental impact intensity data from an IO-LCA database (Weidema et al. 2005). Finally, it is discussed whether, and in which ways the conclusions of comparative LCAs can be affected by including the price difference between product alternatives. This is elucidated in a case study of a comparative LCA screening of two different kinds of Danish cheese products (Fricke et al. 2004). Results  Car purchase and driving, use and maintenance of dwelling, clothing purchase and insurance constitutes the largest percentages of the marginal consumption. In a case study of two cheeses, the including the impact potentials related to the price difference results in significant changes in the total impact potentials. Considering the relatively small price difference of the two products, it is likely also to have a significant influence on the results of comparative LCAs more generally. Discussion  The influence of marginal consumption in comparative LCAs is relevant to consider in situations with large differences in the price of the product alternatives being compared, and in situations with minor differences in the impact potentials related to the alternatives. However, different uncertainties are linked to determining the pattern for marginal consumption and the environmental impact potential related to this. These are first of all related to the method used, but also include inaccurate data of consumption in households, aggregation and weighting of income groups, aggregation of product groups, estimation and size of the price difference, and the general applicability of the results. Conclusion  Incorporating marginal consumption in consequential LCAs is possible in practice. In the case study used, including the rebound effects of the price difference has a significant influence on the result of the comparative LCA, as the result for the impact categories acidification and nutrient enrichment changes in favour of the expensive product. Recommendations and Perspectives  It is recommended that the rebound effects of price differences should be included more frequently in LCAs. In order to ensure this, further research in marginal consumption and investment patterns and IO data for different countries or regions is required. Furthermore, this study does not consider the economic distributional consequences of buying an expensive product instead of a cheaper product (e.g. related to how the profit is spent by those who provided the product). It should also be noted, that more expensive products not necessarily result in less consumption, as those who provided the product also will spend the money they have earned from the sale. Ideally, these consequences should also be further investigated. Likewise, the development of databases to include marginal consumption in PC-tools is needed. In general, considerations of marginal consumption would favour expensive product alternatives, depending, however, on the type of consumer. ESS-Submission Editor: Dr. David Hunkeler (david.hunkeler@aquaplustech.ch)     

Bilateral Song Convergence in a Passerine Hybrid Zone: Genetics Contribute in One Species Only

Hybridization can drive the convergence of territorial and sexual signals. However, non-genetic processes such as competition, environment matching, or cultural transmission, also generate this pattern. We investigated the effect of hybridization on song convergence between two interspecifically territorial warblers in a moving hybrid zone. We confirmed song convergence in each species. Using an AFLP-based genetic index, we detected an effect of genetics on song convergence in Hippolais polyglotta, the expanding species. Evidence was weaker for H. icterina, the receding species. In moving zones, introgression is expected to be larger in the expanding species than in the receding. Thus, the asymmetric contribution of the genetic index to convergence was consistent with expectations for genetically determined traits in moving hybrid zones, and the observed introgression pattern of AFLP markers. However, the geographical location of individuals had an effect on song variation too when genetics was accounted for, suggesting that convergence also has non-genetic explanations. We examine the possible role of alternative processes to that of hybridization and discuss their conflicting effects on reinforcement and hybrid zone dynamics.