Timing in der Tierwelt

Die biologischen Uhren von Tieren sind auf Umwelteinflüsse abgestimmt. Die individuellen Reaktionen auf Klimaveränderungen fallen entsprechend sehr unterschiedlich aus. Wie sich die unterschiedlichen Reaktionsgeschwindigkeiten auf ökologische Zusammenhänge auswirken, ist eine grosse Herausforderung für die Forschung

Evaluation and in situ assessment of photodegradation of polyaromatic hydrocarbons in semipermeable membrane devices deployed in ocean water

Semipermeable membrane devices (SPMDs) were deployed in water using four different methods: a typical SPMD cage with and without a mesh cover, a bowl chamber and without any protection. In addition to routinely used performance reference compounds (PRCs), perdeuterated dibenz[a,h]anthracene was added. Due to its high sampler to water partition coefficient no measurable clearance due to diffusion was expected during the deployment period, hence any observed loss could be attributed to photodegradation. The loss of PRCs was measured and SPMD-based water concentrations determined. Results showed that a typical SPMD deployment cage covered with mesh provided the best protection from photodegradation. Samplers which had undergone the highest photodegradation underestimated PAH water concentrations by up to a factor of 5 compared to the most protected SPMDs. This study demonstrates that the potential for photodegradation needs to be addressed when samplers are deployed in water of low turbidity. Our study indicates that photodegradation of PAHs occurs from passive water samplers (SPMDs) deployed in different devices. Copyright © 2008 Elsevier Ltd All rights reserved

Monitoring of the ecotoxicological hazard potential by polar organic micropollutants in sewage treatment plants and surface waters using a mode-of-action based test battery

We propose and evaluate a mode-of-action based test battery of low-complexity and in-vitro bioassays that can be used as a routine monitoring tool for sewage treatment efficiency and water quality assessment. The test battery comprises five bioassays covering five different modes of toxic action. The bioluminescence inhibition test with Vibrio fischeri and a growth rate inhibition test with the green algae Pseudokirchneriella subcapitata are measures of non-specific integrative effects. A second endpoint in the algae test, the specific inhibition of the efficiency of photosynthesis, gives an account of the presence of herbicides. An enzymatic assay covers an important aspect of insecticidal activity, the inhibition of the acetylcholine esterase activity. Estrogenic effects are assessed with the yeast estrogen screen (YES) and genotoxicity with the umuC test. Three field studies, each lasting six to seven consecutive days, were undertaken at a sewage treatment plant (STP) in Switzerland. Samples were collected in summer and late autumn, under dry and rainy conditions. None of the bioassays gave positive results with raw water in whole effluent toxicity testing. Therefore, water samples from various sites during wastewater treatment and from surface water were enriched with solid-phase extraction. The focus was on non-volatile compounds of average to moderate hydrophobicity, a range that includes most pesticides, biocides and pharmaceuticals. Various polar solid phases were evaluated for their extraction efficiency, disturbance by matrix components and overall performance. We finally selected a mixture of a polymeric sorbent and a C18-sorbent, Lichrolut EN and RP-18 or, alternatively, Empore SDB-RPS disks. All bioassays gave clear and robust responses with the SPE extracts. With the bioassay data the treatment efficiency of the STP can be assessed with respect to different modes of toxic action and accordingly different groups of micropollutants. Furthermore, the data allowed for a comparison between the effluent and the receiving river. In all bioassays the primary effluent had a strong effect and this effect was reduced after passing the STP. Treatment efficiency was high (typically over 90%) but varied from bioassay to bioassay, which is expected because each bioassay detects different types of micropollutants and therefore we cannot expect a common answer

Genetic enhancement of microsomal epoxide hydrolase improves metabolic detoxification but impairs cerebral blood flow regulation

Microsomal epoxide hydrolase (mEH) is a detoxifying enzyme for xenobiotic compounds. Enzymatic activity of mEH can be greatly increased by a point mutation, leading to an E404D amino acid exchange in its catalytic triad. Surprisingly, this variant is not found in any vertebrate species, despite the obvious advantage of accelerated detoxification. We hypothesized that this evolutionary avoidance is due to the fact that the mEH plays a dualistic role in detoxification and control of endogenous vascular signaling molecules. To test this, we generated mEH E404D mice and assessed them for detoxification capacity and vascular dynamics. In liver microsomes from these mice, turnover of the xenobiotic compound phenanthrene-9,10-oxide was four times faster compared to WT liver microsomes, confirming accelerated detoxification. mEH E404D animals also showed faster metabolization of a specific class of endogenous eicosanoids, arachidonic acid-derived epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acids (DHETs). Significantly higher DHETs/EETs ratios were found in mEH E404D liver, urine, plasma, brain and cerebral endothelial cells compared to WT controls, suggesting a broad impact of the mEH mutant on endogenous EETs metabolism. Because EETs are strong vasodilators in cerebral vasculature, hemodynamics were assessed in mEH E404D and WT cerebral cortex and hippocampus using cerebral blood volume (CBV)-based functional magnetic resonance imaging (fMRI). Basal CBV0 levels were similar between mEH E404D and control mice in both brain areas. But vascular reactivity and vasodilation in response to the vasodilatory drug acetazolamide were reduced in mEH E404D forebrain compared to WT controls by factor 3 and 2.6, respectively. These results demonstrate a critical role for mEH E404D in vasodynamics and suggest that deregulation of endogenous signaling pathways is the undesirable gain of function associated with the E404D variant

Protein binding parameters to extrapolate from the in-vitro liver S9 metabolic assay to in-vivo rainbow trout (Oncorhynchus mykiss) bioaccumulation potential of hydrophobic organic chemicals

In vitro metabolic measurements using fish liver S9 fractions have the potential to provide rapid and cost-effective measurements of biotransformation potential by measuring intrinsic clearance rate of the parent chemical. A multi-sector team is undertaking a prevalidation study of the in vitro rainbow trout (Oncorhynchus mykiss) liver S9 metabolic assay to assess bioaccumulation potential of chemicals. However, a prerequisite for the application of in vitro assays is a prediction model that quantitatively links in vitro information to in vivo measures of bioconcentration. The first step in the extrapolation process is the estimation of liver in vivo intrinsic clearance by incorporating scaling factors relating the experimental test conditions from S9 metabolic stability evaluations to the whole liver. As a second step, this intrinsic clearance in the liver is combined with information on liver blood flow and the scaling factor fu. The term fu is the ratio of the free fraction of chemical in the blood to the free fraction of the chemical in the in vitro test system. There is currently no empirical equation for estimating the free fraction in S9 in vitro tests. Therefore, we measured S9 and blood binding for the test chemicals used in the S9 metabolism study. Since they are very hydrophobic with log Kow between 4.5 and 6, classical dialysis methods are unsuitable. We therefore developed a three-phase partitioning method using silicone as third phase to determine the binding constants. The resulting values for S9 were very similar to bovine serum albumin binding constants and binding to blood plasma was two to ten times higher than binding to S9, presumably reflecting the higher lipid content in blood as compared to S9

Klimawandel und Jahreszeiten

Der Klimawandel hat unsere Aufmerksamkeit vermehrt auf Veränderungen in unserer Umwelt gelenkt. Extreme Ereignisse wie Stürme, Überschwemmungen, Trocken- und Hitzeperioden haben direkte Auswirkungen auf unsere Lebenswelt und unseren Alltag. Weniger offensichtlich aber von grosser Tragweite sind die Einflüsse, die der Klimawandel auf die Jahreszeiten ausübt. Die Verschiebung von Blüh- und Ernteterminen, der Rückgang von Schneetagen in höheren Lagen und gar das Ausbleiben von Winterschnee im Mittelland zeigt vor allem mit Blick über mehrere Jahre und Jahrzehnte die gravierenden Folgen für die Umwelt aber auch für Landwirtschaft, Tourismus und Raumplanung. In phänologischen Beobachtungen – breit gefasst definiert als jahreszeitlich wiederkehrende Erscheinungsformen in der Umwelt – lassen sich sinnlich und alltäglich die Veränderungen erfahren, die der Klimawandel mit sich bringt. Darüber hinaus bilden die Überlieferungen dieser Beobachtungen von Generation zu Generation wichtige Brücken in Familiengeschichten und wichtigen Ortsbeschreibungen. Vor allem aber bringen uns die Beobachtungen näher, wie eng Mensch und Natur schon immer verbunden waren. Am Geographischen Institut der Universität Bern hat phänologische Forschung eine lange Tradition. Was in den späten 1960er-Jahren als Beobachtungsnetz und Datengrundlage für die Raum- und Agrareignungsplanung begann, mündete 1970 in die erste komplette Saison des Beobachtungsprogramms BernClim und bildet heute zusammen mit dem Datenschatz des Schweizer Phänologie Beobachtungsnetzes von MeteoSchweiz das Rückgrat für raum-zeitliche Beschreibungen seit Mitte des 20. Jahrhunderts. Beobachtungen seit dem Spätmittelalter bieten darüber hinaus die einmalige Möglichkeit, auch langfristige Veränderungen des Klimas zu zeigen. Zum 50-jährigen Bestehen des Beobachtungsprogramms BernClim entstand die vorliegende Broschüre. Über die Aktivitäten in Bern hinaus kommen auch Forschende zu Wort, die sich mit ebenso viel Herzblut und Ausdauer für die phänologischen Beobachtungen und Auswertungen an anderen Institutionen engagieren. Sie forschen mit Pflanzen- und Tierbeobachtungen, im Wald und auf dem Feld und ziehen Schlüsse aus Wetterdaten, Schnee- und Gewässermessungen. Die Grundlage für viele der hier präsentierten Jahreszeiten-Geschichten bilden Beobachtungen, die zum grossen Teil von Freiwilligen und oft über Jahre und Jahrzehnte gemacht wurden. Phänologie ist ohne dieses Engagement nicht möglich und bringt die Herausforderung mit sich, aus vielen individuellen Beobachtungen ein systematisches, grösseres Bild zu zeichnen. Die Publikation dieser Broschüre wurde durch die Sebastiana-Stiftung, das Oeschger-Zentrum für Klimaforschung (OCCR) und die Kommission für Phänologie und Saisonalität (KPS) der Akademie der Naturwissenschaften Schweiz (SCNAT) unterstützt. Gewidmet ist sie allen, die sich dafür einsetzen, das Zusammenspiel zwischen Mensch und Natur aus jahreszeitlicher Perspektive zu dokumentieren und besser zu verstehen

Assessment of metabolic stability using the rainbow trout (Oncorhynchus mykiss) liver S9 fraction

Standard protocols are given for assessing metabolic stability in rainbow trout using the liver S9 fraction. These protocols describe the isolation of S9 fractions from trout livers, evaluation of metabolic stability using a substrate depletion approach, and expression of the result as in vivo intrinsic clearance. Additional guidance is provided on the care and handling of test animals, design and interpretation of preliminary studies, and development of analytical methods. Although initially developed to predict metabolism impacts on chemical accumulation by fish, these procedures can be used to support a broad range of scientific and risk assessment activities including evaluation of emerging chemical contaminants and improved interpretation of toxicity testing results. These protocols have been designed for rainbow trout and can be adapted to other species as long as species-specific considerations are modified accordingly (e.g., fish maintenance and incubation mixture temperature). Rainbow trout is a cold-water species. Protocols for other species (e.g., carp, a warm-water species) can be developed based on these procedures as long as the specific considerations are taken into account

Protein and lipid binding parameters in rainbow trout (Oncorhynchus mykiss) blood and liver fractions to extrapolate from an in vitro metabolic degradation assay to in vivo bioaccumulation potential of hydrophobic organic chemicals

Binding of hydrophobic chemicals to colloids such as proteins or lipids is difficult to measure using classical microdialysis methods due to low aqueous concentrations, adsorption to dialysis membranes and test vessels, and slow kinetics of equilibration. Here, we employed a three-phase partitioning system where silicone (polydimethylsiloxane, PDMS) serves as a third phase to determine partitioning between water and colloids and acts at the same time as a dosing device for hydrophobic chemicals. The applicability of this method was demonstrated with bovine serum albumin (BSA). Measured binding constants (K(BSAw)) for chlorpyrifos, methoxychlor, nonylphenol, and pyrene were in good agreement with an established quantitative structure-activity relationship (QSAR). A fifth compound, fluoxypyr-methyl-heptyl ester, was excluded from the analysis because of apparent abiotic degradation. The PDMS depletion method was then used to determine partition coefficients for test chemicals in rainbow trout (Oncorhynchus mykiss) liver S9 fractions (K(S9w)) and blood plasma (K(bloodw)). Measured K(S9w) and K(bloodw) values were consistent with predictions obtained using a mass-balance model that employs the octanol-water partition coefficient (K(ow)) as a surrogate for lipid partitioning and K(BSAw) to represent protein binding. For each compound, K(bloodw) was substantially greater than K(S9w), primarily because blood contains more lipid than liver S9 fractions (1.84% of wet weight vs 0.051%). Measured liver S9 and blood plasma binding parameters were subsequently implemented in an in vitro to in vivo extrapolation model to link the in vitro liver S9 metabolic degradation assay to in vivo metabolism in fish. Apparent volumes of distribution (V(d)) calculated from the experimental data were similar to literature estimates. However, the calculated binding ratios (f(u)) used to relate in vitro metabolic clearance to clearance by the intact liver were 10 to 100 times lower than values used in previous modeling efforts. Bioconcentration factors (BCF) predicted using the experimental binding data were substantially higher than the predicted values obtained in earlier studies and correlated poorly with measured BCF values in fish. One possible explanation for this finding is that chemicals bound to proteins can desorb rapidly and thus contribute to metabolic turnover of the chemicals. This hypothesis remains to be investigated in future studies, ideally with chemicals of higher hydrophobicity