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  • Health Reference Center Academic (Gale)  (114)
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  • 1
    Language: English
    In: PLoS ONE, May 1, 2015, Vol.10(5)
    Description: During their aquatic life cycle, nanoparticles are subject to environmentally driven surface modifications (e.g. agglomeration or coating) associated with aging. Although the ecotoxicological potential of nanoparticles might be affected by these processes, only limited information about the potential impact of aging is available. In this context, the present study investigated acute (96 h) and chronic (21 d) implications of systematically aged titanium dioxide nanoparticles (nTiO.sub.2 ; ~90 nm) on the standard test species Daphnia magna by following the respective test guidelines. The nTiO.sub.2 were aged for 0, 1, 3 and 6 d in media with varying ionic strengths (Milli-Q water: approx. 0.00 mmol/L and ASTM: 9.25 mmol/L) in the presence or absence of natural organic matter (NOM). Irrespective of the other parameters, aging in Milli-Q did not change the acute toxicity relative to an unaged control. In contrast, 6 d aged nTiO.sub.2 in ASTM without NOM caused a fourfold decreased acute toxicity. Relative to the 0 d aged particles, nTiO.sub.2 aged for 1 and 3 d in ASTM with NOM, which is the most environmentally-relevant setup used here, significantly increased acute toxicity (by approximately 30%), while a toxicity reduction (60%) was observed for 6 d aged nTiO.sub.2 . Comparable patterns were observed during the chronic experiments. A likely explanation for this phenomenon is that the aging of nTiO.sub.2 increases the particle size at the start of the experiment or the time of the water exchange from 100 nm to approximately 500 nm, which is the optimal size range to be taken up by filter feeding D. magna. If subjected to further agglomeration, larger nTiO.sub.2 particles, however, cannot be retained by the daphnids filter apparatus ultimately reducing their ecotoxicological potential. This non-linear pattern of increasing and decreasing nTiO.sub.2 related toxicity over the aging duration, highlights the knowledge gap regarding the underlying mechanisms and processes. This understanding seems, however, fundamental to predict the risks of nanoparticles in the field.
    Keywords: Nanoparticles ; Toxicity ; Humic Acids ; Titanium Dioxide
    ISSN: 1932-6203
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: 2012, Vol.7(11), p.e48956
    Description: The nanoparticle industry is expected to become a trillion dollar business in the near future. Therefore, the unintentional introduction of nanoparticles into the environment is increasingly likely. However, currently applied risk-assessment practices require further adaptation to accommodate the intrinsic nature of engineered nanoparticles. Combining a chronic flow-through exposure system with subsequent acute toxicity tests for the standard test organism Daphnia magna , we found that juvenile offspring of adults that were previously exposed to titanium dioxide nanoparticles exhibit a significantly increased sensitivity to titanium dioxide nanoparticles compared with the offspring of unexposed adults, as displayed by lower 96 h-EC 50 values. This observation is particularly remarkable because adults exhibited no differences among treatments in terms of typically assessed endpoints, such as sensitivity, number of offspring, or energy reserves. Hence, the present study suggests that ecotoxicological research requires further development to include the assessment of the environmental risks of nanoparticles for the next and hence not directly exposed generation, which is currently not included in standard test protocols.
    Keywords: Research Article ; Agriculture ; Biology ; Materials Science ; Biotechnology ; Neuroscience
    E-ISSN: 1932-6203
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  • 3
    In: PLoS ONE, 2013, Vol.8(11)
    Description: Due to their surface characteristics, nanosized titanium dioxide particles (nTiO 2 ) tend to adhere to biological surfaces and we thus hypothesize that they may alter the swimming performance and behavior of motile aquatic organisms. However, no suitable approaches to address these impairments in swimming behavior as a result of nanoparticle exposure are available. Water fleas Daphnia magna exposed to 5 and 20 mg/L nTiO 2 (61 nm; polydispersity index: 0.157 in 17.46 mg/L stock suspension) for 96 h showed a significantly ( p 〈0.05) reduced growth rate compared to a 1-mg/L treatment and the control. Using three-dimensional video observations of swimming trajectories, we observed a treatment-dependent swarming of D. magna in the center of the test vessels during the initial phase of the exposure period. Ensemble mean swimming velocities increased with increasing body length of D. magna , but were significantly reduced in comparison to the control in all treatments after 96 h of exposure. Spectral analysis of swimming velocities revealed that high-frequency variance, which we consider as a measure of swimming activity, was significantly reduced in the 5- and 20-mg/L treatments. The results highlight the potential of detailed swimming analysis of D. magna for the evaluation of sub-lethal mechanical stress mechanisms resulting from biological surface coating and thus for evaluating the effects of nanoparticles in the aquatic environment.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 4
    Language: English
    In: Expert Review of Cardiovascular Therapy, 01 September 2011, Vol.9(9), pp.1193-1201
    Description: Cardiovascular magnetic resonance (CMR) imaging can precisely quantify cardiac size and function, but moreover depict tissue changes that are associated with various forms of myocardial inflammation. Thereby, CMR can often detect myocardial inflammation before contractility is obviously impaired....
    Keywords: Cardiovascular Magnetic Resonance Imaging ; Contrast ; Edema ; Inflammation ; Myocarditis ; Pharmacy, Therapeutics, & Pharmacology
    ISSN: 1477-9072
    E-ISSN: 1744-8344
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  • 5
    Language: English
    In: PLoS ONE, 2011, Vol.6(5), p.e20112
    Description: The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely limited to standard short-term (≤48 h) toxicity tests, which lack both NP fate characterization and an understanding of the mechanisms underlying toxicity. Employing slightly longer exposure times (72 to 96 h), we found that suspensions of nanosized (∼100 nm initial mean diameter) titanium dioxide (nTiO 2 ) led to toxicity in Daphnia magna at nominal concentrations of 3.8 (72-h EC 50 ) and 0.73 mg/L (96-h EC 50 ). However, nTiO 2 disappeared quickly from the ISO-medium water phase, resulting in toxicity levels as low as 0.24 mg/L (96-h EC 50 ) based on measured concentrations. Moreover, we showed that nTiO 2 (∼100 nm) is significantly more toxic than non-nanosized TiO 2 (∼200 nm) prepared from the same stock suspension. Most importantly, we hypothesized a mechanistic chain of events for nTiO 2 toxicity in D. magna that involves the coating of the organism surface with nTiO 2 combined with a molting disruption. Neonate D. magna (≤6 h) exposed to 2 mg/L nTiO 2 exhibited a “biological surface coating” that disappeared within 36 h, during which the first molting was successfully managed by 100% of the exposed organisms. Continued exposure up to 96 h led to a renewed formation of the surface coating and significantly reduced the molting rate to 10%, resulting in 90% mortality. Because coating of aquatic organisms by manmade NP might be ubiquitous in nature, this form of physical NP toxicity might result in widespread negative impacts on environmental health.
    Keywords: Research Article ; Biology ; Chemistry ; Earth Sciences ; Materials Science ; Medicine ; Chemistry ; Public Health And Epidemiology ; Marine And Aquatic Sciences ; Ecology ; Critical Care And Emergency Medicine ; Science Policy ; Biochemistry ; Non-clinical Medicine
    E-ISSN: 1932-6203
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  • 6
    Language: English
    In: Bulletin of Environmental Contamination and Toxicology, 2016, Vol.96(5), pp.563-564
    Description: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s00128-016-1788-5 Byline: Sebastian Stehle (1), Ralf Schulz (1) Author Affiliation: (1) Institute for Environmental Sciences, University Koblenz-Landau, Fortstra[sz]e 7, 76829, Landau, Germany Article History: Registration Date: 23/03/2016 Received Date: 08/02/2016 Accepted Date: 22/03/2016 Online Date: 28/03/2016 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s00128-016-1788-5) contains supplementary material, which is available to authorized users.
    Keywords: Water Pollution ; Water Resources ; Insecticides;
    ISSN: 0007-4861
    E-ISSN: 1432-0800
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  • 7
    Language: English
    In: Environmental Toxicology and Chemistry, June, 2013, Vol.32(6), p.1254(10)
    Description: Byline: Renja Bereswill, Martin Streloke, Ralf Schulz Abstract The European Union's directive for sustainable use of pesticides requires implementing risk mitigation measures at streams threatened by pesticide entries. The need for mitigation measures was investigated at 10 stream sites within an intensively used arable region in central Germany by characterizing pesticide exposure following edge-of-field runoff and effects on the aquatic macroinvertebrates. Moreover, the influence of riparian buffer strip width (as a mitigation measure) at the sampling sites was considered. Generally, invertebrate fauna was dominated by pesticide-tolerant species, suggesting a high pesticide exposure at almost all sites. This result is also reflected by the elevated levels of suspended particle contamination in terms of toxic units (logTU.sub.Max〉-2), corresponding to one-hundredth of the median lethal concentration (LC50) to Daphnia magna. At two sites that received high aqueous-phase entries of the pyrethroid lambda-cyhalothrin (logTU.sub.Max〉-0.6), the abundance and number of sensitive species in terms of the species at risk index decreased during the pesticide application period. In contrast, no acute significant negative effects on macroinvertebrates were observed at sites characterised by low water-phase toxicity (logTU.sub.Max〈-3.5). An influence of riparian buffer strip width on pesticide exposure was not observed, supposedly because of the presence of erosion rills and ephemeral ditches. In conclusion, results show that mitigation measures (such as the improvement of currently present riparian buffer strips) are needed in the study area. Environ Toxicol Chem 2013;32:1254-1263. A[c] 2013 SETAC Supporting information: Additional Supporting Information may be found in the online version of this article All Supplemental Data may be found in the online version of this article.
    Keywords: Pesticides -- Usage ; Runoff ; Endangered Species
    ISSN: 0730-7268
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  • 8
    Language: English
    In: PLoS ONE, 01 January 2017, Vol.12(4), p.e0174634
    Description: Traditional methods to identify aquatic hyphomycetes rely on the morphology of released conidia, which can lead to misidentifications or underestimates of species richness due to convergent morphological evolution and the presence of non-sporulating...
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 9
    Language: English
    In: Bulletin of Environmental Contamination and Toxicology, 2013, Vol.90(6), pp.640-645
    Description: Vegetated treatment systems have the ability to reduce the risk of adverse effects of nonpoint source pesticide pollution in agricultural surface waters, however, flow-through systems have rarely been evaluated. Peak concentrations of a mixture of two insecticides and two fungicides (Indoxacarb, Tebuconazole, Thiacloprid and Trifloxystrobin) were reduced by more than 90 % in 45 m experimental stream mesocosms. Plant density and solubility had the highest explanatory power for the response variable reduction of peak concentration (R² = 0.70, p  〈 0.001). Optimized vegetated streams can be highly effective in reduction of runoff related pesticide peak concentrations.
    Keywords: Risk mitigation ; Pollution ; Experimental ditch mesocosm ; Aquatic plants ; FOCUS
    ISSN: 0007-4861
    E-ISSN: 1432-0800
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  • 10
    In: PLoS ONE, 2013, Vol.8(5)
    Description: The chemokine receptor CXCR4 regulates cell migration during ontogenesis and disease states including cancer and inflammation. Upon stimulation by the endogenous ligand CXCL12, CXCR4 becomes phosphorylated at multiple sites in its C-terminal domain. Mutations in the CXCR4 gene affecting C-terminal phosphorylation sites are a hallmark of WHIM syndrome, a genetic disorder characterized by a gain-of-CXCR4-function. To better understand how multi-site phosphorylation of CXCR4 is organized and how perturbed phosphorylation might affect CXCR4 function, we developed novel phosphosite-specific CXCR4 antibodies and studied the differential regulation and interaction of three C-terminal phosphorylation sites in human embryonic kidney cells (HEK293). CXCL12 promoted a robust phosphorylation at S346/347 which preceded phosphorylation at S324/325 and S338/339. After CXCL12 washout, the phosphosites S338/339 and S324/325 were rapidly dephosphorylated whereas phosphorylation at S346/347 was long-lasting. CXCL12-induced phosphorylation at S346/347 was staurosporine-insensitive and mediated by GRK2/3. WHIM syndrome-associated CXCR4 truncation mutants lacking the S346/347 phosphosite and the recently identified E343K WHIM mutant displayed strongly impaired phosphorylation at S324/325 and S338/339 as well as reduced CXCL12-induced receptor internalization. Relevance of the S346-S348 site was confirmed by a S346-348A mutant showing strongly impaired CXCL12-promoted phosphorylation at S324/325 and S338/339, defective internalization, gain of calcium mobilization, and reduced desensitization. Thus, the triple serine motif S346-S348 contains a major initial CXCR4 phosphorylation site and is required for efficient subsequent multi-site phosphorylation and receptor regulation. Hierarchical organization of CXCR4 phosphorylation explains why small deletions at the extreme CXCR4 C terminus typically associated with WHIM syndrome severely alter CXCR4 function.
    Keywords: Research Article ; Biology
    E-ISSN: 1932-6203
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