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Genotoxicity of 4-nonylphenol and nonylphenol ethoxylate mixtures with the use of Saccharomyces cerevisiae D7 mutation assay and use of this text to evaluate the efficiency of biodegradation treatments.
No full textNonylphenol ethoxylates (NPnEOs, n is the number of ethoxylic units in the molecule) are non-ionic surfactants widely used in several industrial applications, such as textile and leather processing, paper industry, formulation of pesticides, paints and washing cleaners. 4-Nonylphenol (4-NP), the main product of NPnEO biodegradation, is a toxic xenobiotic compound classified as endocrine disrupter. While numerous studies reported the toxicity and estrogenic activity of nonylphenols, little is known about the mutagenicity of these compounds. In this paper, the genotoxicity of 4-NP and NPnEO mixtures was evaluated by using the D7 strain of Saccharomyces cerevisiae as experimental model. The same tests were applied to effluents deriving from laboratory scale packed-bed bioreactors, developed for the treatment of NPnEO contaminated wastewater, in order to evaluate the residual genotoxic potential with respect to the influent waste. The target compounds fed to the bioreactors were 4-NP and NPnEO mixtures possessing an average of 5 or 1.5 ethoxylic units (Igepal CO-520 and Igepal CO-210, respectively). The results showed that 4-NP induced significant cytotoxic effect on S. cerevisiae cells at 60 mg/L, as well as mutagenic effects at 15 and 30 mg/L. 4-NP was the most genotoxic compound among those assayed, followed by Igepal CO-210, whereas Igepal CO-520 did not induce genotoxicity at any of the assayed concentrations. The genotoxic effects evidenced on yeast cells treated with 4-NP disappeared after the treatment in the bioreactor. This indicates that the biological treatment is capable of removing not only the pollutant, but also the toxicity associated to the compound and its degradation metabolites. This study represents, to the best of our knowledge, the first report that evaluates the genotoxicity of both 4-NP, NPnEOs and their potential aerobic degradation products on an eukaryotic organism. The obtained results suggest that the S. cerevisiae D7 strain is a very effective model to study the induction of genotoxic damage by the compounds under study. In addition, this method is much more simpler and easier to be applied than other tests described in the literature to study genotoxic effects. Moreover, the test described in this work has also proven to be effective in evaluating the toxicity of effluents deriving from laboratory scale biotreatment processes. It would be really interesting to apply the described tests on real wastewater treatment system in order to estimate the detoxification potential of the process applied, which is often not directly correlated with the removal of the target pollutant
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Effects of cadmium, chromium and copper on symbiotic and free-living Rhizobium leguminosarum biovar trifolii.
No full textPlasmid-minus derivatives of Rhizobium leguminosarum biovar trifolii have been isolated. Cured strains lacked symbiotic properties, however they showed increased heavy metal resistance. In the presence of 70 ppm chromium the parent strain, unlike cured derivatives, is unable to grow explanta but can nevertheless nodulate clover. We propose that rhizobia can circumvent exposure to the heavy metal by entering the plant roots. Acetylene reduction tests showed that nodulated plants, grown in the presence of 10 ppm of chromium, had an increased nitrogenase activity compared to the control plants
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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