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Biomarkers in caddisfly larvae of the species Hydropsyche pellucidula (Curtis, 1834) (Trichoptera: Hydropsychidae) measured in natural populations and after short term exposure to fenitrothion
No full textA spatially explicit dynamic multimedia fate model to investigate pesticide fate in mountain river basins
No full textIncreased alanine concentration is associated with exposure to fenitrothion but not carbamates in Chironomus riparius larvae
No full textChironomus riparius Meigen were exposed to three different insecticides, the organophosphorous fenitrothion and the carbamates carbaryl and carbofuran (0, 1, 10, and 100 mu g/L) for 24h as fourth-instar larvae. Acetylcholinesterase (AChE), naphtylacetate esterase (NAE), p-nitrophenylacetate esterase (PNPAE), glutathione-S-transferase (GST), and a number of metabolites (alanine, pyruvate, lactate, trehalose, aspartate, oxalacetate) were measured to determine which was the most valuable biochemical biomarker of exposure. ACNE activity was significantly reduced by all three insecticides, PNPAE by fenitrothion, carbofuran and carbaryl, whereas NAE activity was stimulated by carbaryl and unaffected by fenitrothion and carbofuran. Metabolites analysis revealed a strong accumulation of alanine in larvae exposed to fenitrothion, but not in larvae exposed to carbamates. This accumulation was accompanied by a significant increase of lactate and a significant decrease of pyruvate and trehalose. No variations were observed with carbofuran and carbaryl. No change of aspartate concentration was detected. We conclude that the association of alanine accumulation with a significant inhibition of ACNE activity can be used as a valuable biochemical biomarker of exposure
Leucine transport in membrane vesicles from Chironomus riparius larvae displays a melange of crown-group features
No full textLeucine uptake into membrane vesicles from larvae of the midge Chironomus riparius was studied. The membrane preparation was highly enriched in typical brush border membrane enzymes and depleted of other membrane contaminants. In the absence of cations, there was a stereospecific uptake of L-leucine, which exhibited saturation kinetics. Parameters were determined both at neutral (Km 33 ± 5 μM and Vmax 22.6 ± 6.8 pmol/ 7s/mg protein) and alkaline (Km 46 ± 5 μM and Vmax 15.5 ± 2.5 pmol/7s/mg protein) pH values. At alkaline pH, external sodium increased the affinity for leucine (Km 17 ± 1 μM) and the maximal uptake rate (Vmax 74.0 ± 12.5 pmol/7s/mg protein). Stimulation of leucine uptake by external alkaline pH agreed with lumen pH measurements in vivo. Competition experiments indicated that at alkaline pH, the transport system readily accepts most L-amino acids, including branched, unbranched, and a-methylated amino acids, histidine and lysine, but has a low affinity for phenylalanine, β-amino acids, and N-methylated amino acids. At neutral pH, the transport has a decreased affinity for lysine, glycine, and α-methylleucine. Taken together, these data are consistent with the presence in midges of two distinct leucine transport systems, which combine characters of the lepidopteran amino acid transport system and of the sodium-dependent system from lower neopterans. Arch. Insect Biochem. Physiol. 48:51-62, 2001
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
Hypoxia and anoxia effects on alcohol dehydrogenase activity and hemoglobin content in Chironomus riparius Meigen, 1804
Full text linkThe metabolic effects of low oxygen content on alcohol-dehydrogenase (ADH) activity and hemoglobin (Hb) concentration were investigated in IV-instar larvae of Chironomus riparius (Diptera: Chironomidae) from an Italian stream. Two series of short-term (48 h) experiments were carried out: exposure to (1) progressive hypoxia (95 to 5% of oxygen saturation) and (2) anoxia (at <5% of oxygen saturation). In (1), Hb amount increased with increasing oxygen depletion up to a critical value of oxygenation (about 70% of oxygen saturation). Below this percentage, the Hb amount declined to values comparable with those present in the control. The respiration rate (R) remained almost constant at oxygen saturation >50% and decreased significantly only after 48 h of treatment (= <5% of oxygen saturation) reaching values <100 mmolO2 gAFDW-1 h-1. ADH activity showed two phases of growth, within the first 14 h and over 18 h of exposure. Overall, we inferred that i) Hb might function as short-term oxygen storage, enabling animals to delay the on-set of anaerobiosis; and ii) alcoholic fermentation co-occurs for a short time with aerobic respiration, becoming the prevalent metabolic pathway below 5% of oxygen saturation (<1 mg L-1). These considerations were supported also by results from anoxia exposure (2). In such condition, larvae were visibly stressed, becoming immobile after few minutes of incubation, and ADH reached higher values than in the hypoxia treatment (2.03±0.15 UADH mg prot-1). Overall, this study showed a shift from aerobic to anaerobic activity in C. riparius larvae exposed to poorly oxygenated water with an associated alteration of ADH activity and the Hb amount. Such metabolites might be valid candidate biomarkers for the environmental monitoring of running waters.</p
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
Evaluation of Enzyme Biomarkers in Freshwater Invertebrates from Taro and Ticino River, Italy
No full textBenthic macroinvertebrates are an essential component of freshwater environments. The ecotoxicological risk of benthic communities, estimated through the assay of biochemical markers, can be used as an early warning signal for environment alterations. In this work the activities of a number of enzymes, regarded as potential biomarker of exposure to pollutants (catalase, acetylcholinesterase, glutathione-S-transferase) was determined in homogenates of whole organisms. Specimens were collected in the rivers Taro and Ticino, northern Italy, in stony bottom reaches in five and three stations respectively. The orders of aquatic Insects Diptera, Plecoptera, Odonata, Ephemeroptera and Trichoptera, the Crustacea Amphipoda, and Annelida Oligochaeta were examined. Additional enzymes, such as NADP-dependent malate dehydrogenase, isocitric dehydrogenase, glucose-6-phosphate dehydrogenase, alcohol dehydrogenase, and lactate dehydrogenase were considered in the study. Results emphasize significant differences among taxa concerning the specific activity of most enzymes
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
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