1,720,959 research outputs found
Comet Assay on Daphnia magna in eco-genotoxicity testing
No full texttDetection of potentially hazardous compounds in water bodies is a priority in environmental risk assess-ment. For the evaluation and monitoring of water quality, a series of methodologies may be applied.Among them, the worldwide used toxicity tests with organisms of the genus Daphnia is one of the mostpowerful. In recent years, some attempts were made to utilize Daphnia magna in genotoxicity testing asmany of the new environmental contaminants are described as DNA-damaging agents in aquatic orga-nisms. The aim of this research was to develop a highly standardized protocol of the Comet Assay adaptedfor D. magna, especially regarding the isolation of cells derived from the same tissue (haemolymph) fromnewborn organisms exposed in vivo. Several methods for haemolymph extraction and different CometAssay parameters were compared. Electrophoretic conditions were adapted in order to obtain minimumDNA migration in cells derived from untreated organisms and, at the same time, maximum sensitiv-ity in specimens treated with known genotoxicants (CdCl2and H2O2). Additional tests were performedto investigate if life-history traits of the cladoceran (such as the age of adult organisms that providenewborns, the clutch size of origin, the number of generations reared in standard conditions) and thewater composition as well, might influence the response of the assay. This study confirms the poten-tial application of the Comet Assay in D. magna for assessing genotoxic loads in aqueous solution. Thenewly developed protocol could integrate the acute toxicity bioassay, thus expanding the possibility ofusing this model species in freshwater monitoring (waters, sediment and soil elutriates) and is in linewith the spirit of the EU Water Framework Directive in reducing the number of bioassays that involvemedium-sized species
Dalla valutazione dello stato qualitativo alla identificazione delle cause di alterazione negli ambienti acquatici: un obiettivo raggiungibile?
No full textToxicological (acute and chronic test), genotoxicological (Comet Assay) and toxicogenomic bioassays with Daphnia magna,
together with the analysis of macrobenthic community structure, were applied to water samples from sections of Parma
Valley water courses subjected to different levels of anthropic pressure. These results support the application of eco-genotoxicological
assays with D. magna in investigative monitoring of freshwater ecosystems
Implementazione di una strategia di indagine integrata per l’identificazione delle cause di stress negli ambienti acquatici.
No full textMetodi ecotossicogenomici nel monitoraggio degli ambienti acquatici: modulazione dell’attività trascrizionale in Daphnia magna.
No full textWithin a research aimed at the development and application of “effect-based” methods in environmental monitoring, a study based on
the toxicogenomic approach was undertaken. Specifi cally, a procedure for assessing the alteration of gene expression was developed
and applied in Daphnia magna in vivo exposed to environmental samples taken from sections of the Val Parma hydrographic network
subjected to different anthropogenic pressures. The transcriptional profi le of genes involved in reproductive activity (vitellogenin1, vtg1),
development (cuticle 12, cut12, and the carboxypeptidase A1 precursor, cpa1) and in energy resource allocation (hemoglobin, dhb1) was
analyzed. To select the most appropriate development stage and to evaluate the sensitivity of the method, the fi rst phase of the study was
devoted to the analysis of the effects of known endocrine disruptors (20-hydroxyecdysone and cadmium) on gene transcriptional profi le.
The standardized protocol was then applied to the monitoring of watercourses. A mountain section of Parma river was selected as a
possible reference station. Considering the results as a whole, a general alteration of gene expression is evident in organisms exposed to
samples from small waterways in the plain and, in the main watercourse, along a downstream gradient. Additionally, evidences obtained
from the toxicogenomic approach are in accordance with the classifi cation of the sections based on biological elements
Early and late maternal effects on hatching phenology of heterocypris incongruens (crustacea: Ostracoda)
No full textIn ephemeral ponds, the hatching asynchrony of resting eggs may be adaptive and the result of a
maternal bet-hedging strategy. A mother can influence the progeny phenology through conditions
experienced during life cycle even in early development stages. We investigated the consequences
of a hatching delay for offspring and compared early and late maternal effects in a clonal lineage
of Heterocypris incongruens. We used females from genetically identical, 40 months old, resting
eggs that hatched, asynchronically, after a first (FI) or a second (SI) inundation event. Maternal
origin (FI or SI) was considered an early effect involving the maternal response to hatching stimuli
during the embryological dormant stage. Maternal age at deposition and egg size were considered
late effects that account for maternal conditions during active stage. We compared size and
development time of eggs produced by FI and SI females under laboratory condition (24°C 12:12 L:
D photoperiod). Maternal origin affected development time to adulthood which was later in FI than
in SI females, and fecundity that was higher in FI than in SI females. SI eggs were smaller than FI
eggs: size was affected by maternal age at deposition and was directly related to the egg
development time. Development time varied from 1 to 117 days and was shorter in SI eggs than in
FI eggs. Our results showed that maternal response during embryological stage affects the
performance in successive active stages and suggested that hatching asynchrony may be
considered a risk spread strategy
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
Ecological Risk Assessment and development of innovative strategies for monitoring the quality of water bodies: application of a new integrated approach in a pilot basin.
No full textFreshwater is extremely precious; but even more precious than freshwater is clean freshwater. From the time that 2/3 of our planet is covered in water, we have contaminated our globe with chemicals that have been used by industrial activities over the last century in a unprecedented way causing harm to humans and wildlife.
We have to adopt a new scientific mindset in order to face this problem so to protect this important resource. The Water Framework Directive (European Parliament and the Council, 2000) is a milestone legislative document that transformed the way that water quality monitoring is undertaken across all Member States by introducing the Ecological and Chemical Status. A “good or higher” Ecological Status is expected to be achieved for all waterbodies in Europe by 2015. Yet, most of the European waterbodies, which are determined to be at risk, or of moderate to bad quality, further information will be required so that adequate remediation strategies can be implemented.
To date, water quality evaluation is based on five biological components (phytoplankton, macrophytes and benthic algae, macroinvertebrates and fishes) and various hydromorphological and physicochemical elements. The evaluation of the chemical status is principally based on 33 priority substances and on 12 xenobiotics, considered as dangerous for the environment. This approach takes into account only a part of the numerous xenobiotics that can be present in surface waters and could not evidence all the possible causes of ecotoxicological stress that can act in a water section. The mixtures of toxic chemicals may constitute an ecological risk not predictable on the basis of the single component concentration. To improve water quality, sources of contamination and causes of ecological alterations need to be identified. On the other hand, the analysis of the community structure, which is the result of multiple processes, including hydrological constrains and physico-chemical stress, give back only a “photograph” of the actual status of a site without revealing causes and sources of the perturbation. A multidisciplinary approach, able to integrate the information obtained by different methods, such as community structure analysis and eco-genotoxicological studies, could help overcome some of the difficulties in properly identifying the different causes of stress in risk assessment.
In synthesis, the river ecological status is the result of a combination of multiple pressures that, for management purposes and quality improvement, have to be disentangled from each other. To reduce actual uncertainty in risk assessment, methods that establish quantitative links between levels of contamination and community alterations are needed. The analysis of macrobenthic invertebrate community structure has been widely used to identify sites subjected to perturbation. Trait-based descriptors of community structure constitute a useful method in ecological risk assessment. The diagnostic capacity of freshwater biomonitoring could be improved by chronic sublethal toxicity testing of water and sediment samples. Requiring an exposure time that covers most of the species’ life cycle, chronic toxicity tests are able to reveal negative effects on life-history traits at contaminant concentrations well below the acute toxicity level. Furthermore, the responses of high-level endpoints (growth, fecundity, mortality) can be integrated in order to evaluate the impact on population’s dynamics, a highly relevant endpoint from the ecological point of view. To gain more accurate information about potential causes and consequences of environmental contamination, the evaluation of adverse effects at physiological, biochemical and genetic level is also needed. The use of different biomarkers and toxicity tests can give information about the sub-lethal and toxic load of environmental compartments. Biomarkers give essential information about the exposure to toxicants, such as endocrine disruptor compounds and genotoxic substances whose negative effects cannot be evidenced by using only high-level toxicological endpoints. The increasing presence of genotoxic pollutants in the environment has caused concern regarding the potential harmful effects of xenobiotics on human health, and interest on the development of new and more sensitive methods for the assessment of mutagenic and cancerogenic risk.
Within the WFD, biomarkers and bioassays are regarded as important tools to gain lines of evidence for cause-effect relationship in ecological quality assessment. Despite the scientific community clearly addresses the advantages and necessity of an ecotoxicological approach within the ecological quality assessment, a recent review reports that, more than one decade after the publication of the WFD, only few studies have attempted to integrate ecological water status assessment and biological methods (namely biomarkers or bioassays). None of the fifteen reviewed studies included both biomarkers and bioassays.
The integrated approach developed in this PhD Thesis comprises a set of laboratory bioassays (Daphnia magna acute and chronic toxicity tests, Comet Assay and FPG-Comet) newly-developed, modified tacking a cue from standardized existing protocols or applied for freshwater quality testing (ecotoxicological, genotoxicological and toxicogenomic assays), coupled with field investigations on macrobenthic community structures (SPEAR and EBI indexes). Together with the development of new bioassays with Daphnia magna, the feasibility of eco-genotoxicological testing of freshwater and sediment quality with Heterocypris incongruens was evaluated (Comet Assay and a protocol for chronic toxicity). However, the Comet Assay, although standardized, was not applied to freshwater samples due to the lack of sensitivity of this species observed after 24h of exposure to relatively high (and not environmentally relevant) concentrations of reference genotoxicants. Furthermore, this species demonstrated to be unsuitable also for chronic toxicity testing due to the difficult evaluation of fecundity as sub-lethal endpoint of exposure and complications due to its biology and behaviour.
The study was applied to a pilot hydrographic sub-Basin, by selecting section subjected to different levels of anthropogenic pressure: this allowed us to establish the reference conditions, to select the most significant endpoints and to evaluate the coherence of the responses of the different lines of evidence (alteration of community structure, eco-genotoxicological responses, alteration of gene expression profiles) and, finally, the diagnostic capacity of the monitoring strategy. Significant correlations were found between the genotoxicological parameter Tail Intensity % (TI%) and macrobenthic community descriptors SPEAR (p<0.001) and EBI (p<0.05), between the genotoxicological parameter describing DNA oxidative stress (ΔTI%) and mean levels of nitrates (p<0.01) and between reproductive impairment (Failed Development % from D. magna chronic bioassays) and TI% (p<0.001) as well as EBI (p<0.001). While correlation among parameters demonstrates a general coherence in the response to increasing impacts, the concomitant ability of each single endpoint to be responsive to specific sources of stress is at the basis of the diagnostic capacity of the integrated approach as demonstrated by stations presenting a mismatch among the different lines of evidence. The chosen set of bioassays, as well as the selected endpoints, are not providing redundant indications on the water quality status but, on the contrary, are contributing with complementary pieces of information about the several stressors that insist simultaneously on a waterbody section providing this monitoring strategy with a solid diagnostic capacity.
Our approach should provide opportunities for the integration of biological effects into monitoring programmes for surface water, especially in investigative monitoring. Moreover, it should provide a more realistic assessment of impact and exposure of aquatic organisms to contaminants. Finally this approach should provide an evaluation of drivers of change in biodiversity and its causalities on ecosystem function/services provision, that is the direct and indirect contributions to human well-being
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