Comparison of different biological indices for the assessment of river quality: application to the upper river Moselle (France)

The aim of our study was to assess the water quality of the upper Moselle river by using biological indices. Simultaneous physico-chemical surveys were also undertaken from May 1999 to April 2000. Twelve sampling sites were selected in order to provide a wide range of potential pollution. Chemical analysis did not reveal any major problem of pollution. However a lower water quality resulting from domestic pollution was established for some sampling sites. A biological monitoring combining both macroinvertebrates and macrophytes was performed. Biological indices based on plant community structure and macrophyte composition were not pertinent tools, whereas simple indices based on taxonomic richness of particular groups of macroinvertebrates were strongly correlated with several chemical parameters, showing that such simple biological variables should represent powerful indicators of ecosystem degradation.     

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.     

Biochemical and strain properties of CJD prions: complexity versus simplicity

Prions, the agents responsible for transmissible spongiform encephalopathies, are infectious proteins consisting primarily of scrapie prion protein (PrP(Sc)), a misfolded, β-sheet enriched and aggregated form of the host-encoded cellular prion protein (PrP(C)). Their propagation is based on an autocatalytic PrP conversion process. Despite the lack of a nucleic acid genome, different prion strains have been isolated from animal diseases. Increasing evidence supports the view that strain-specific properties may be enciphered within conformational variations of PrP(Sc). In humans, sporadic Creutzfeldt-Jakob disease (sCJD) is the most frequent form of prion diseases and has demonstrated a wide phenotypic and molecular spectrum. In contrast, variant Creutzfeldt-Jakob disease (vCJD), which results from oral exposure to the agent of bovine spongiform encephalopathy, is a highly stereotyped disease, that, until now, has only occurred in patients who are methionine homozygous at codon 129 of the PrP gene. Recent research has provided consistent evidence of strain diversity in sCJD and also, unexpectedly enough, in vCJD. Here, we discuss the puzzling biochemical/pathological diversity of human prion disorders and the relationship of that diversity to the biological properties of the agent as demonstrated by strain typing in experimental models.     

Immobilization and affinity purification of recombinant proteins using histidine peptide fusions

A gene fusion approach to simplify protein immobilization and purification is described. A gene encoding the protein of interest is fused to a gene fragment encoding the affinity peptide Ala-His-Gly-His-Arg-Pro. The expressed fusion proteins can be purified using immobilized metal affinity chromatography. A vector, designed to ensure obligate head-to-tail polymerization of oligonucleotide linkers was constructed by in vitro mutagenesis. A linker encoding the affinity peptide, was synthesized and polymerized to two, four and eight copies. These linkers were fused to the 3' end of a structural gene encoding a two-domain protein A molecule, ZZ, and to the 5' end of a gene encoding beta-galactosidase. Fusion proteins, of both types, with zero or two copies of the linker showed little or no binding to immobilized Zn2+, while a relatively strong interaction could be observed for the fusions based on four or eight copies of the linker. Using a pH gradient, the ZZ fusions were found to be eluted from the resin at different pHs depending on the number of the affinity peptide. These results demonstrate that genetic engineering can be used to facilitate purification and immobilization of proteins to immobilized Zn2+ and that the multiplicity of the affinity peptide is an important factor determining the binding characteristics.     

Lipid content and apoptosis of in vitro-produced bovine embryos as determinants of susceptibility to vitrification

The objective was to evaluate supplementation of fetal calf serum (FCS) and phenazine ethosulfate (PES), a metabolic regulator that inhibits fatty acid synthesis, in culture media during in vitro production (IVP) of bovine embryos. Taking oocyte fertilization (n = 4,320) as Day 0, four concentrations of FCS (0, 2.5, 5, and 10%) and three periods of exposure to PES (without addition—Control; after 60 h—PES Day 2.5 of embryo culture; and after 96 h—PES Day 4) were evaluated. Increasing FCS concentration in the culture media enhanced lipid accumulation (P < 0.05), increased apoptosis in fresh (2.5%: 19.1 ± 1.8 vs 10%: 28.4 ± 2.3, P < 0.05; mean ± SEM) and vitrified (2.5%: 42.8 ± 2.7 vs 10%: 69.2 ± 3.4, P < 0.05) blastocysts, and reduced blastocoele re-expansion after vitrification (2.5%: 81.6 ± 2.5 vs 10%: 67.3 ± 3.5, P < 0.05). The addition of PES in culture media, either from Days 2.5 or 4, reduced lipid accumulation (P < 0.05) and increased blastocoele re-expansion after vitrification (Control: 72.0 ± 3.0 vs PES Day 2.5: 79.9 ± 2.8 or PES Day 4: 86.2 ± 2.4, P < 0.05). However, just the use of PES from D4 reduced apoptosis in vitrified blastocysts (Control: 52.0 ± 3.0 vs PES Day 4: 39.2 ± 2.4, P < 0.05). Independent of FCS withdrawal or PES addition to culture media, the in vivo control group had lesser lipid accumulation, a lower apoptosis rate, and greater cryotolerance (P < 0.05). The increased lipid content was moderately correlated with apoptosis in vitrified blastocysts (r = 0.64, P = 0.01). In contrast, the increased apoptosis in fresh blastocysts was strongly correlated with apoptosis in vitrified blastocysts (r = 0.94, P < 0.0001). Therefore, using only 2.5% FCS and the addition of PES from Day 4, increased the survival of IVP embryos after vitrification. Moreover, embryo quality, represented by the fresh apoptosis rate, was better than lipid content for predicting embryo survival after vitrification.     

The secondary coordination sphere and axial ligand effects on oxygen reduction reaction by iron porphyrins: a DFT computational study

Oxygen reduction reaction (ORR) catalyzed by a bio-inspired iron porphyrin bearing a hanging carboxylic acid group over the porphyrin ring, and a tethered axial imidazole ligand was studied by DFT calculations. BP86 free energy calculations of the redox potentials and pK _a’s of reaction components involved in the proton coupled electron transfer (PCET) reactions of the ferric-hydroxo and -superoxo complexes were performed based on Born–Haber thermodynamic cycle in conjunction with a continuum solvation model. The comparison was made with iron porphyrins that lack either in the hanging acid group or axial ligand, suggesting that H-bond interaction between the carboxylic acid and iron-bound hydroxo, aquo, superoxo, and peroxo ligands (de)stabilizes the Fe–O bonding, resulting in the increase in the reduction potential of the ferric complexes. The axial ligand interaction with the imidazole raises the affinity of the iron-bound superoxo and peroxo ligands for proton. In addition, a low-spin end-on ferric-hydroperoxo intermediate, a key precursor for O–O cleavage, can be stabilized in the presence of axial ligation. Thus, selective and efficient ORR of iron porphyrin can be achieved with the aid of the secondary coordination sphere and axial ligand interactions.     

The effect of the armored scale,Rhizaspidiotus donacis (Hemiptera: Diaspididae), on shoot growth of the invasive plant Arundo donax (Poaceae: Arundinoideae)

The effect of feeding by the armored scale, Rhizaspidiotus donacis (Leonardi, 1920) (Hemiptera: Diaspididae) on the growth of the plant Arundo donax L. (Poaceae) was evaluated under field conditions in its native range. The study was designed to evaluate the impact of R. donacis, a candidate agent for biological control of A. donax which is invasive in arid riparian ecosystems of the Southwestern USA and Mexico. The study was carried out at five A. donax sites in the Province of Alicante, Spain, differing in altitude and climate. At each site, 30 infested lateral shoots were selected and 15 were randomly treated monthly with imidacloprid insecticide. Shoot lengths were measured monthly over a 1-year period in a comparative growth analysis. Shoots infested with R. donacis had an over 2-fold reduced growth rate as compared to treated shoots. Growth of shoots varied by site, and the effect of R. donacis on growth was most pronounced in the late spring, when mature females produced first instar scale crawlers. The impact of R. donacis on A. donax growth under field conditions in the native range, combined with its narrow host specificity, indicate that R. donacis is a promising candidate for biological control of A. donax in North America and other areas invaded by this weed.     

Development of a seed DNA-based genotyping system for marker-assisted selection in maize

Leaf collection from the field, labeling and tracking back to the source plants after genotyping are rate limiting steps in leaf DNA-based genotyping. In this study, an optimized genotyping method using endosperm DNA sampled from single maize seeds was developed, which can be used to replace leaf DNA-based genotyping for both genetic studies and breeding applications. A similar approach is likely to be suitable for all plants with relatively large seeds. Part of the endosperm was excised from imbibed maize seeds and DNA extracted in 96-tube plates using individuals from eight F₂ populations and seven inbreds. The quality of the resultant DNA was functionally comparable to DNA extracted from leaf tissue. Extraction from 30 mg of endosperm yields 3–10 μg DNA, which is sufficient for analysis of 200–400 agarose-gel PCR-based markers, with the potential for several million chip-based SNP marker analyses. By comparing endosperm DNA and leaf DNA for individuals from an F₂ population, genotyping errors caused by pericarp contamination and hetero-fertilization were found to average 3.8 and 0.6%, respectively. Endosperm sampling did not affect germination rates under controlled conditions, although under normal field conditions the germination rate, seedling establishment, and growth vigor were significantly lower than that of non-sampled controls for some genotypes. However, careful field management can compensate for these effects. Seed DNA-based genotyping lowered costs by 24.6% compared to leaf DNA-based genotyping due to reduced field plantings and labor costs. A substantial advantage of this approach is that it can be used to select desirable genotypes before planting. As such it provides an opportunity for dramatic improvements in the efficiency and selective gain of breeding systems based on optimum combinations of marker-assisted selection and phenotypic selection within and between generations.