Comparison of uptake and elimination kinetics of metallic oxide nanomaterials on the freshwater microcrustacean Daphnia magna

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Comparison Between Twelve Nanomaterial's Accumulation and Elimination Behavior on Microcrustaceans (Daphnia magna)

International audienceNanomaterials (NMs) production and usage have been raising concerns for the last decades. Since such substances are particulate contaminants, their first contact with organisms is a physical encounter ruled by physicochemical processes that can determinate the potential NMs accumulation, toxicity, and trophic transfer. There is still a lack of understanding on the main NMs properties that drive the accumulation and epuration processes. This work aims at studying and comparing the accumulation and epuration profiles of a set of twelve well characterized NMs with the microcrustacean Daphnia magna in equal conditions and to investigate the NMs properties that influence this phenomenon. The NMs set is constituted by 6 TiO2, 3 SiO2, 2 CeO2 and 1 ZnO NMs. The accumulation phase of the study was carried out during 24h of waterborne exposure to 1mg/L NMs suspension. Then, the organisms passed to the elimination phase of 120h in clean media. Samples were taken during the whole accumulation and elimination phases and were analyzed by ICP-OES. Using the biodynamic metal bioaccumulation model, the influx and loss rate constants have been found and compared. Differences have been determined on the accumulation and epuration kinetics of the NMs. These differences appeared to be linked to the NMs physicochemical properties as zeta potential measures can be correlated to the elimination rate constants. Similar observations were made concerning the same NMs and another type of organisms as microalgae, which highlights the importance of the physicochemical properties’ role on the nano-bio interaction. These findings open the possibility of grouping the NMs based on their relationship with organisms for risk assessment purposes

Plastic additives: challenges in ecotox hazard assessment

International audienceThe risk of plastic debris, and specifically micro(nano)plastic particles, to ecosystems remains to be fully characterized. One particular issue that warrants further characterization is the hazards associated with chemical additives within micro (nano)plastic as they are not chemically bound within the polymers and can be persistent and biologically active. Most plastics contain additives and are therefore potential vectors for the introduction of these chemicals into the environment as they leach from plastic, a process that can be accelerated through degradation and weathering processes. There are knowledge gaps on the ecotoxicological effects of plastic additives and how they are released from parent plastic materials as they progressively fragment from the meso to micro and nano scale. This review summarizes the current state of knowledge of the ecotoxicity of plastic additives and identifies research needs to characterize the hazard they present to exposed biota. The potential ecological risk of chemical additives is of international concern so key differences in governance between the European Union and New Zealand to appropriately characterize their risk are highlighted

Characterization of tyramine -hydroxylase, an enzyme upregulated by stress in Periplaneta americana

International audienceOctopamine (OA) is an important neuroactive substance that modulates several physiological functions and behaviors of various invertebrate species. This biogenic monoamine, structurally related to noradrenaline, acts as a neurotransmitter, a neuromodulator, or a neurohormone in insects. The tyramine β-hydroxylase (TBH) catalyzes the last step in OA biosynthesis and thus plays a key role in the regulation of synthesis and secretion of OA in neurons. The aim of this study was to characterize TBH in the cockroach Periplaneta americana and to get a better understanding of its regulation under stress conditions in this insect. First of all, five full-length cDNAs encoding TBH isoforms were cloned from the nerve cord of the physiological model P. americana. PaTBH transcripts were found mainly expressed in nervous tissues and in octopaminergic dorsal unpaired median neurons. In addition, a new ELISA assay was developed so as to allow determination of both OA level and TBH activity in stressed cockroaches. Mechanical stressful stimulation led to a significant increase in TBH activity after 1 and 24 h, with a higher induction after 1 h than after 24 h. Thus, TBH could be considered as a promising biomarker of stress in insects rather than OA

Cross effects of salinity and ceria nanoparticles on two endobenthic bivalves Corbicula fluminea and Scrobicularia plana: multibiomarker assess

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