1,721,017 research outputs found
Relationship between kinetics of benzo[a]pyrene bioaccumulation and DNA binding in the mussel Mytilus galloprovincialis.
No full textDNA adduct formation has been studied in mussel by using a mesocosm system and 13 day exposure period. Results indicate that B[a]P in feed is bioavailable for the organisms: for the dose applied, its accumulation and biotransformation in mussel resulted in the DNA binding of B[a]P metabolites. Differences in uptake and biotransformation abilities among tissues likely explain the different levels of B[a]P-DNA recorded in digestive gland compared to gills. Data obtained during depuration demonstrate the musseI ability to recover from B[a]P exposure in term of tissue dose and DNA damage. Because mussels are chronically exposed to pollutants in the marine environment, DNA adduct measurement cab be used as a cumulative index of current and recent exposure to genotoxin compounds
Benzo(a)pyrene-induced DNA damage in Mytilus galloprovincialis: Measurement of bulky DNA adducts and DNA oxidative damage in terms of 8-oxo-7,8-dihydro-2'-deoxyguanosine formation.
No full textBulky DNA adducts and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) were measured in gill DNA of benzo[a]pyrene (B[a]P)-exposed mussels (50 mg kg(-1) dw day(-1)), respectively by the P-32-post-labelling technique and high performance liquid chromatography coupled to electrochemical detection assay. A time-course study was performed for both biomarkers and their potential use for marine biomonitoring discussed for the sentinel species studied. In gills, B[a]P-related DNA adducts were positively correlated with B[ a] P concentration in whole mussel, and were produced in a time-dependent manner relative to exposure. Comparison of adduct levels recorded in this paper in gills (0.149 +/- 0.079 (standard deviation) to 0.480 +/- 0.139 adduct per 10(8) normal nucleotides) with previous measures carried out in the digestive gland of the same animals (0.010 +/- 0.005 to 0.251 +/- 0.062 adduct per 10(8) normal nucleotides) (Akcha et al. in press) showed higher levels in the former tissue (p 0.05), whereas by the chaotropic method lower 8-oxodGuo levels (0.02 p < 0.05) were measured for both tissue (8.3 +/- 2.0 and 4.8 +/- 1.1 8-oxodGuo per 10(5) dGuo respectively). Contributory factors to the lack of observed increase in gill 8-oxodGuo level by B[ a] P exposure could be due to the selected way of exposure (via the feed supply) for which gills were not the target tissue of exposure and artifactual DNA oxidation during sample processing that could have masked the possible B[a]P oxidative DNA damage
Enzymatic biomarker measurement and study of DNA adduct formation in benzo[a]pyrene-contaminated mussels, Mytilus galloprovincialis.
No full textThe aim of this study was to improve the knowledge on the metabolic pathways involved in benzo[a]pyrene (B[a]P) activation and on the relationship between adduct levels and enzymatic biomarker activities. With this purpose, a model to assess pollutant exposure via food supply has been developed for the sentinel organism, Mytilus gallolprovincialis. Mussels were fed for 4 weeks with B[a]P-contaminated feed (50 mg/kg dry weight mussel). Bioaccumulation was studied by determination of B[a]P concentration in whole mussel by GC/MS analysis. Different biomarkers of pollutant exposure were measured to assess the metabolic state of the exposed organisms. CYP1A-like immunopositive protein titration and B[a]P hydroxylase (BPH) activity were assessed as indicators of phase I biotransformation. Glutathione-S-transferase (GST) activity was measured as an indicator of the conjugation activities. Catalase (CAT) and DT-diaphorase (DTD) activities were assessed as potential biomarkers of oxidative stress, whereas acetylthiocholine esterase (AChE) activity was measured as an indication of possible neurotoxicity of B[a]P exposure. DNA adduct levels were determined in digestive gland DNA by applying the P-32-postlabeling technique with nuclease Fl enhancement. For the developed conditions of exposure, B[a]P concentration reached in whole mussel tissues was very high ( > 500 mg/kg d.w. mussel) and significant B[a]P-induced changes were recorded for each enzymatic biomarkers. BPH and CAT activities were significantly increased by B[a]P exposure, whereas GST in the gills, DTD and AChE were significantly depressed. On the other hand, no change in CYP1A-like immunopositive protein content was observed. Induction and increase with time of bulky B[a]P-related DNA adducts were demonstrated ill the digestive gland, although at low levels (0.269 +/- 0.082 adduct/10e8 dNps at maximum) by the P-32-postlabeling assay. DNA adduct level was significantly correlated with whole mussel tissue B[a]P concentration, so were all the enzymatic biomarkers measured except to GST activity in both gill and digestive gland tissues. BPH, DTD, CAT and AChE displayed a strong correlation with adduct levels. These results demonstrate the neurotoxicity and the genotoxicity of B[a]P exposure ill the mussel. The induction of bulky DNA adducts ill mussels demonstrates the existence of activation pathways already identified in vertebrates. It validates also the suitability of this model for further studies on B[a]P metabolism in mussels. Our results support the proposal of BPH, AChE, DTD and CAT activities as suitable biomarkers of PAH exposure for these sentinel species
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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