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Thermal denaturation of RNA free coat proteins of tobacco mosaic virus (TMV) was studied for wildtype TMV (vulgare) and the temperature-sensitive mutant, Ni 118. The ability to form soluble aggregates as well as the optical properties (ORD, UV-difference spectra), and the sedimentation behavior were used as criteria for the native state.
At pH 7.5, I= 0.02 denaturation is reversible for both proteins. The ORD data indicate that the denatured proteins contain residual secondary structure. The “melting temperatures”, as defined by ORD measurements (cp = 0.02 mM), are 39.5 ± 1°C for vulgare and 27 ± 1°C for Ni 118 at pH 7.5, I= 0.02. By means of the aggregation test (cp = 0.05 mM) somewhat lower melting temperatures were found under the same solvent conditions. The difference between the primary structures of vulgare and Ni 118 proteins being a proline → leucine (pos. 20) replacement, the results suggest the cyclic structure of proline (20) to have a specific stabilizing function in the three dimensional protein structure. This conclusion is supported by preliminary experiments on a temperature-sensitive mutant with a threonine residue in pos. 20.
The genus Andromma Simon, 1893 is revised. The type species A. aethiopicum Simon, 1893 (♂♀) and the other three known species, A. anochetorum Simon, 1909 (♂), A. bouvieri Fage, 1936 (♀) and A. raffrayi Simon, 1899 (♂♀), are redescribed. The types of the subspecies A. raffrayi inhacorense Lessert, 1936 were not examined. This subspecies is considered a synonym of the nominal species. Nineteen new species are described and illustrated: A. albinovani sp. nov. (♂♀), A. alvoculatum sp. nov. (♀), A. anacardium sp. nov. (♀), A. cyamos sp. nov. (♀), A. cycnotrachelos sp. nov. (♂♀), A. delphiurum sp. nov. (♂♀), A. deogratias sp. nov. (♂♀), A. dicranobelos sp. nov. (♂), A. didrepanum sp. nov. (♂), A. divinagraciae sp. nov. (♂♀), A. elephantactes sp. nov. (♀), A. ghesquierei sp. nov. (♂♀), A. heligmos sp. nov. (♀), A. helix sp. nov. (♀), A. juakalyi sp. nov. (♂), A. katangensis sp. nov. (♀), A. ophiophagum sp. nov. (♀), A. prosopion sp. nov. (♀) and A. velum sp. nov. (♂♀). The distribution of the species and their apparent commensalism with termites are discussed.
Ist es wichtiger, welchen Namen man sich im jeweiligen kulturellen Kontext zulegt, und sagt der bei der Geburt gegebene Name weniger über die soziokulturelle Dimension aus als ein später angenommener? Für Miguel de Cervantes’ Don Quijote scheint diese Annahme formgebend zu sein: denn den Namen ‚Don Quijote‘ kennt heute fast jeder, den ursprünglichen Namen dieser fiktiven Figur dagegen, der im Roman in verschiedenen Versionen angegeben wird, weiß nicht einmal mehr der Erzähler selbst zweifelsfrei zu nennen. […] Onomastische Überlegungen und Forschungen gibt es inzwischen zu nahezu allen weltliterarisch bedeutsamen Texten […]. Interessant beim Don Quijote ist hierbei, dass eine vielschichtige Überlegung angestellt werden muss: allein bezüglich des Namens der Hauptfigur sind zum einen die Motivationen zu betrachten, die der Autor bei der Namensgebung seiner Figur hatte, und welche Rezipientenbeeinflussung ihm somit durch die Wahl des Namens ‚Don Quijote‘ vorschwebte. Zum andern ist aber auch die Motivation zu analysieren, die der Erzähler seiner Figur, welche er ja diesen und andere Namen ersinnen lässt, unterstellen möchte. Des Weiteren muss auch der ursprüngliche innerfiktive Name der Hauptfigur Beachtung finden und dabei besonders die Tatsache, dass der Erzähler sich dazu entschieden hat, diesen Namen bis zum Ende des Romans in der Schwebe zu lassen und in verschiedenen Variationen anzubieten. Hinzu kommen noch zusätzliche Beinamen, die der Ritter im Laufe des Romans annimmt.
Der Prager deutsche Schriftsteller Johannes Urzidil (1896-1970) wird seit der Wende 1989 in seiner Heimat wiederentdeckt, und auch im deutschsprachigen Raum findet er in den letzten Jahren ein größeres Interesse und wird wieder verstärkt rezipiert. Der Artikel skizziert Leben und Werk dieses bedeutenden böhmischen Autors, weist auf unlängst erschienene Publikationen hin und stellt die geplante Urzidil-Werkausgabe vor.
Endocrine disrupting compounds (EDCs) emerged as a major concern for water quality in the last decade and have been studied extensively since. Besides typical natural and synthetic estrogens also petroleum product compounds such as some PAHs have been identified as potential EDCs, revealing endocrine disruption to be a relevant mode of action for crude oil toxicity. Hence, in the context of a comprehensive retro- or prospective risk assessment of oil spills the implementation of mechanism-specific toxicity such as endocrine disruption is of high importance. To evaluate the exposure risk for the aquatic biota, research focuses on water-soluble fractions underlying an oil slick that could be simulated via water-accommodated fractions (WAF). Against this background human (ERα-CALUX®) and yeast based (A-YES®) reporter gene bioassays were successfully optimized for the application in estrogenicity evaluation of the water-accommodated fraction (WAF) from a crude oil. Combining different approaches, the estrogenicity of the WAFs from a naphthenic North Sea crude oil was tested with and without the addition of a chemical dispersant addressing specific aspects of estrogenicity including the influence of biotransformation capacities and different salinity conditions. Both the WAF free from droplets (LEWAF) as well as the chemically dispersed WAF (CEWAF) gave indications of an ER-mediated estrogenicity with much stronger ERα agonists in the CEWAF treatment. Resulting estradiol equivalents of the WAFs were above the established effect-based trigger values for both bioassays. Results indicate that the dispersant rather increased the fraction of ER-activating crude oil compounds instead of interacting with the receptor itself. Only slight changes in estrogenic responses were observed when cells capable of active metabolism (T47D) were used instead of cells without endogenous metabolism (U2-OS) in the recombinant ER transactivation CALUX assay. With the yeast cells a higher estrogenic activity was observed in the experiments under elevated salinity conditions (6‰), which was in contrast to previous expectations due to typical decrease in dissolved PAH fraction with increasing salinity (salting-out effect) but might be related to increased cell sensitivity.
Genotoxicity assessment is of high relevance for crude and refined petroleum products, since oil compounds are known to cause DNA damage with severe consequences for aquatic biota as demonstrated in long-term monitoring studies. This study aimed at the optimization and evaluation of small-scale higher-throughput assays (Ames fluctuation, micronucleus, Nrf2-CALUX®) covering different mechanistic endpoints as first screening tools for genotoxicity assessment of oils. Cells were exposed to native and chemically dispersed water-accommodated fractions (WAFs) of three oil types varying in their processing degree. Independent of an exogenous metabolic activation system, WAF compounds induced neither base exchange nor frame shift mutations in bacterial strains. However, significantly increased chromosomal aberrations in zebrafish liver (ZF-L) cells were observed. Oxidative stress was indicated for some treatments and was not correlated with observed DNA damage. Application of a chemical dispersant increased the genotoxic potential rather by the increased bioavailability of dissolved and particulate oil compounds. Nonetheless, the dispersant induced a clear oxidative stress response, indicating a relevance for general toxic stress. Results showed that the combination of different in vitro assays is important for a reliable genotoxicity assessment. Especially, the ZF-L capable of active metabolism and DNA repair seems to be a promising model for WAF testing.
In situ burning (ISB) is discussed to be one of the most suitable response strategies to combat oil spills in extreme conditions. After burning, a highly viscous and sticky residue is left and may over time pose a risk of exposing aquatic biota to toxic oil compounds. Scientific information about the impact of burn residues on the environment is scarce. In this context, a comprehensive ISB field experiment with approx. 1000L IFO 180 was conducted in a fjord in Greenland. The present study investigated the toxicity of collected ISB residues to early life stages of zebrafish (Danio rerio) as a model for potentially exposed pelagic organisms. The toxicity of ISB residues on zebrafish embryos was compared with the toxicity of the initial (unweathered) IFO 180 and chemically dispersed IFO 180. Morphological malformations, hatching success, swimming behavior, and biomarkers for exposure (CYP1A activity, AChE inhibition) were evaluated in order to cover the toxic response on different biological organization levels. Across all endpoints, ISB residues did not induce greater toxicity in zebrafish embryos compared with the initial oil. The application of a chemical dispersant increased the acute toxicity most likely due to a higher bioavailability of dissolved and particulate oil components. The results provide insight into the adverse effects of ISB residues on sensitive life stages of fish in comparison with chemical dispersant application.
Petroleum products including crude oils and refined distillates are unique environmental pollutants consisting of thousands of compounds with varying physical-chemical properties and resulting toxicity for aquatic biota. Hence, for a reliable risk assessment individual petroleum product toxicity profiles are needed. Furthermore, the influence of oil spill response strategies like the application of chemical dispersants has to be implemented. The present study addressed the toxicity of water-accommodated fractions (WAFs) of two different oil types on fish early life stages on different biological organization levels in the laboratory model species Danio rerio. Experiments with a 3rd generation dispersant used in loading rated resembling the exposure in experiments with chemically dispersed oils were included, enabling a direct comparability of results. This approach is of high importance as especially the investigation of dispersant toxicity in relevant exposure concentrations is rather scarce. Zebrafish embryos were exposed to different WAFs shortly after and up to 120 hour post fertilization (hpf). Besides phenotypic effects including edema and spine deformations, reduced responses to dark stimuli, increased CYP1A activity and marginal AChE inhibition were observed in sublethal effect concentrations. Both oil types had varying strength of toxicity, which did not correlate with corresponding chemical analysis of target PAHs. Chemically dispersed oils induced stronger acute toxicity in zebrafish embryos compared to native (initial) oil exposure, which was further reflected by very low exposure concentrations for biomarker endpoints. Based on a comparison to the dispersant alone, a higher toxicity of dispersed oils was related to a combination of dispersant toxicity and an elevated crude oil compound bioavailability, due to dispersion-related partitioning kinetics. In contrast to LEWAF and CEWAF neither typical morphological effects nor mechanism-specific toxicity were observed for the dispersant alone, indicating narcosis as the responsible cause of effects.