Quantification of trypsin with a radioimmunoassay in herring larvae (Clupea harengus) compared with a highly sensitive fluorescence technique to determine tryptic enzyme activity

Enzymatic activity and quantity of the protease trypsin were measured in individual herring larvae (Clupea harengus L.). The enzymatic activity assay was done using a fluorescence technique, and a radioimmunoassay was used for quantification of trypsin. The results are compared and the differences between the techniques discussed. Both methods gave similar results, as high or low values in trypsin quantity were reflected in high or low values of tryptic activity. Quantity and activity were linearly and positively correlated, but small differences between methods were found at the lowest detection limits. Both techniques reflect high variability between individual larvae.     

Female sticklebacks Gasterosteus aculeatus use self-reference to optimize MHC allele number during mate selection

Theoretical and empirical studies suggest that an optimal resistance to pathogens and parasites requires an optimal number of MHC alleles per individual. Here we argue that three-spined sticklebacks (Gasterosteus aculeatus) achieve this goal by applying a strategy that involves a self-referential process. According to this model, females complement their own set of alleles with a more or less diverse set of male alleles such that the combined diversity reaches an optimum. In previous experiments, we have identified allele counting as a major mate-choice strategy in large populations. The self-referential allele-counting hypothesis predicts that MHC-based mate choice favors dissimilar MHC alleles in small populations facing the risk of inbreeding. Therefore, we conducted an experiment that simulated a small effective population size with low MHC class-II diversity. Our experiments are based on the analysis of MHC class-IIB alleles that explain a major part of the overall MHC diversity in sticklebacks, as determined by mathematical modeling. The results show that females preferred males with dissimilar alleles. Our present and the previous studies (which we reanalyzed with respect to our new predictions) show that irrespective of high or low population diversity faced by female sticklebacks for their mate choice, they use information about their own and their potential mate's MHC polymorphism for optimal complementation of their own set of alleles. From combining the data of the previous and the present experiment we found that female sticklebacks try to achieve an optimum number of MHC class-IIB alleles for their offspring through mate choice. The chosen MHC diversity is close to the most frequent diversity found naturally in individual fish, which in addition have the lowest parasite burden.     

Can Species Have Capabilities,and What if They Can?

In this article, I apply the environmental or expanded capabilities approach to species and examine whether species as wholes can have capabilities and what are the implications if they can. The examination provides support for the claim that species as evolutionary groups can possess capabilities. They have integrity, which refers to the functionings that enable the self-making and development (evolvement) of species, and it is conceptually possible to identify capabilities that essentially enable or contribute to species integrity. One central capability for species can be identified from conservation literature: adaptive capacity, the ability of species to react to environmental changes by self-regulative evolution. After constructing the main argument that species can have capabilities and that they possess the capability to adaptive capacity, I shortly expound on the implications of these claims. It turns out that there are at least three different ways to apply the notion, and that the claim ‘species have capabilities’ does not entail that species are necessarily recipients of justice.     

Exposing ecological and economic costs of the research‐implementation gap and compromises in decision making

The frequently discussed gap between conservation science and practice is manifest in the gap between spatial conservation prioritization plans and their implementation. We analyzed the research‐implementation gap of one zoning case by comparing results of a spatial prioritization analysis aimed at avoiding ecological impact of peat mining in a regional zoning process with the final zoning plan. We examined the relatively complex planning process to determine the gaps among research, zoning, and decision making. We quantified the ecological costs of the differing trade‐offs between ecological and socioeconomic factors included in the different zoning suggestions by comparing the landscape‐level loss of ecological features (species occurrences, habitat area, etc.) between the different solutions for spatial allocation of peat mining. We also discussed with the scientists and planners the reasons for differing zoning suggestions. The implemented plan differed from the scientists suggestion in that its focus was individual ecological features rather than all the ecological features for which there were data; planners and decision makers considered effects of peat mining on areas not included in the prioritization analysis; zoning was not truly seen as a resource‐allocation process and not emphasized in general minimizing ecological losses while satisfying economic needs (peat‐mining potential); and decision makers based their prioritization of sites on site‐level information showing high ecological value and on single legislative factors instead of finding a cost‐effective landscape‐level solution. We believe that if the zoning and decision‐making processes are very complex, then the usefulness of science‐based prioritization tools is likely to be reduced. Nevertheless, we found that high‐end tools were useful in clearly exposing trade‐offs between conservation and resource utilization.     

Good practice in testing for an association in contingency tables

The testing for an association between two categorical variables using count data is commonplace in the behavioral sciences. Here, we present evidence that influential biostatistical textbooks give contradictory and incomplete advice on good practice in the analysis of such contingency table data. We survey the statistical literature and offer guidance on such analyses. Specifically, we call for greater use of exact testing rather than tests which use an asymptotic chi-squared distribution. That is, we suggest that researchers take a conservative approach and only perform asymptotic testing where there is little doubt that it is appropriate. We recommend a specific criterion for such decision-making. Where asymptotic testing is appropriate, we recommend chi-squared over the G-test and recommend against the implementation of Yates (or any other) correction. We also provide advice on the effective use of exact testing for associations in contingency tables. Lastly, we highlight issues that need to be considered when using the commonly recommended Fisher’s exact test.     

Verhalten von Nanosilber in Kläranlagen und dessen Einfluss auf die Nitrifikationsleistung in Belebtschlamm

Background, aim and scope The application of nanosilver is increasing. Knowledge on the fate and behavior of nanosilver in wastewater and wastewater treatment plants is scarce. Studies under real world conditions are completely lacking. We studied (1) the impact of nanosilver on the nitrification of sewage sludge, (2) quantified the mass flow of nanosilver in a pilot-plant, and (3) verified the mass balance in a full-scale municipal wastewater treatment plant where nanosilver is introduced to the municipal plant by an indirect discharger. Materials and Methods The addition of four different nanosilver additives on ammonia oxidation in activated sludge has been studied in batch-reactors at two concentrations (1, 100?mg/L Ag) with two exposure times (2?h, 6?days). The pilot-plant treating 70 population equivalents of domestic wastewater is operated with a 12?day sludge age. Nanosilver was applied to the activated sludge tank within two sludge ages. The silver concentrations were measured in sludge and effluent samples during dosing and the following two sludge ages. The adsorption and speciation of silver particles has been analyzed using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Influent, effluent and sludge were sampled on a full-scale plant (60?000 equivalent inhabitants) and analyzed for silver. Results Silver nitrate, metallic nanosilver, nano-scaled silver chloride and microcomposite silver did not show any effect on ammonia oxidation after the addition of 1?mg/L Ag to the activated sludge (corresponding to 250?mg Ag per kg solids). In contrast, 100?mg/L Ag inhibited the nitrification process by 100?% after the addition of silver nitrate and 20–30?% after addition of colloidal polymer-coated nanosilver. A complete mass balance of the pilot-plant, a steady-state system with known fluxes, demonstrates significant enrichment of silver in the sewage sludge (96?%) after the addition of silver chloride to the plant and small losses of silver into the secondary effluent (4?%). The mass fluxes are similar to metallic colloidal nanosilver investigated under the same conditions. The mass balance has been consistently confirmed by the full-scale study in a municipal wastewater treatment plant. The silver fluxes correspond to the fluxes of the suspended solids in sludge and effluent. Overall, it is estimated that from public wastewater treatment plants about 4–40?mg/a Ag per inhabitant equivalent are discharged annually to the receiving water. The analysis by SEM-EDX demonstrates adsorption and incorporation of nanosilver on biological flocs. This method yields first insight into complex building and transformation of silver associated with sulfide after adding metallic nanosilver and silver chloride to wastewater. Discussion Silver ions released from nanosilver react immediately with large amounts of chloride present in wastewater to form silver chloride. Silver ions may react with organic ligands or sulfide groups additionally. Consequently, even silver nitrate added with 1?mg/L Ag (250?mg Ag/kg TS) to activated sludge did not inhibit nitrification activity. Very high amounts of nanosilver, i.?e. 100?mg/L Ag, overburdened the system and equilibrium condition between silver ion release and ligands was not reached. The mass balance reflects the excellent attachment of nanosilver to activated sludge and biological flocs. Therefore, the main elimination process of nanosilver is attachment to the activated sludge. The elimination of nanosilver is high compared to organic and inorganic micro pollutants omnipresent in wastewater. Any further reduction of suspended solids in the effluent water will reduce the silver load. Conclusions Generally, in wastewater nanosilver occurs bonded to activated sludge flocs and therefore the elimination of nanosilver is efficient under operation conditions typical for wastewater treatment plants. The major fraction of nanosilver is removed from the system by the excess sludge withdrawal. Nonetheless, the efficiency may be further improved by a tertiary filtration step. All analyses of influent, effluent and sludge confirmed that silver exists as silver sulfide. Due to a negligible water solubility of this silver species, silver ions are not subsequently released. Recommendations and perspectives Nanosilver research should be driven to the identification of transformation processes in real environmental matrices and the influence of coatings on the adsorption behavior. There is no need for action to take special measures for nanosilver removal in the area of municipal wastewater treatment plants compared to ubiquitous hazardous organic pollutants may present in wastewater. Nevertheless, source control measures following the precautionary principle should be performed.     

Temporal limitations in the use of potassium dichromate as a blood preservative for the analysis of organohalogenated contaminants including polybrominated diphenyl ethers,dioxins and PCBs

Previous studies described the use of potassium dichromate (K₂Cr₂O₇) to successfully preserve whole blood for up to 34 days at room temperature (20–22°C) for analysis of chlorinated dioxins, dibenzofurans and PCBs. Potassium dichromate has been successfully employed as a preservative for cows’ milk and in a World Health Organization study of human milk. The use of two 100?mg tablets in 40 to 100?mL of whole blood in anticoagulant was found to provide almost identical levels of dioxins, dibenzofurans, PCBs and lipids as found in frozen comparison blood at??70°C which is generally regarded as the gold standard for blood preservation. Potassium dichromate was found to be preferable to 20 and 40% ethyl alcohol for this preservation. This finding opens opportunities for preservation under field conditions in developing countries where neither electricity nor dry ice is available. Not having to use dry ice for shipping also allows more flexibility in the choice of commercial carriers for transporting blood to an analytical laboratory. It is recommended considering a number of compounds in addition to those studied in our first report and extending the time beyond 34 days in order to determine if longer storage might also be feasible. Data on polybrominated diphenyl ethers (PBDEs), as well as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and selected polychlorinated biphenyls (PCBs) are reported. For the present study 3 and 6 months were chosen in potassium dichromate at room temperature compared to freezing at ?70°C. Data indicate that these times exceed the limits of efficacy of potassium dichromate for whole blood preservation. This was attributed to degradation of the lipid component of the blood. Since dioxins and closely related structural analogues are traditionally reported as lipid normalized blood levels, this degradation of lipids provides erroneous results. Therefore, potassium dichromate is not recommended for long-term storage beyond 34 days at room temperature. It is planned to study the time period between one and three months and higher temperature preservation for shorter time periods, simulating conditions in tropical countries, to attempt to extend further the ease and convenience of chemical preservation of blood.     

Partitioning of polybrominated diphenyl ether (PBDE) congeners in human blood and milk

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants (BFRs) which have recently been detected in human blood and milk in the USA, and presently these PBDE levels are found to be the highest globally. On a population basis, individual blood and individual milk analyses show similar congener patterns and levels. Until now, there has not been a study comparing PBDE levels in milk and blood of the same individuals. This study is the first to report these levels for PBDEs, though partitioning between blood and milk has been done previously for dioxins and polychlorinated biphenyls (PCBs). Twelve congeners in 11 nursing mothers’ blood and milk were found and the data describe partitioning ratios between blood and milk. The data suggest it may be easier for smaller, less brominated congeners to move from blood to milk.