Search

Poly(amidoamine) (PAMAM) dendrimers hold great promises for biomedicine. This study sought to examine the toxicity of generation 4 (G4) cationic PAMAM dendrimer to the green microalga, Chlamydomonas reinhardtii, using physiological and molecular biomarkers. Results revealed that the G4 dendrimer at 15 and 25 nM stimulated the photosynthetic process and the production of reactive oxygen species (ROS) in algae. However, the over-production of ROS did not induce the expression of antioxidant enzyme genes, catalase and glutathione peroxidase. In addition, genes encoding light-harvesting proteins ( lhca and lhcb), a ferredoxin ( fdx) and an oxygen-evolving enhancer protein ( psb) involved in photosynthesis were repressed after treatment. Nevertheless, the expression of the lhcbm9 gene, encoding a major light harvesting polypeptide, was increased. These results suggest that the strong modulation of photosynthesis induced by the dendrimer could lead to elevated ROS levels in microalgae. [ABSTRACT FROM AUTHOR]

Pesticides are being detected in water bodies on an increasingly frequent basis. The present study focused on toxicity and phytoremediation potential of aquatic plants to remove phytosanitary products from contaminated water. We investigated the capacity of Lemna minor (L. minor) to eliminate two herbicides isoproturon and glyphosate from their medium. Since phytoremediation relies on healthy plants, pesticide toxicity was evaluated by exposing plants to 5 concentrations (0–20 μg L−1 for isoproturon and 0–120 μg L−1 for glyphosate) in culture media for 4 d using growth rate and chlorophyll a fluorescence as endpoints. At exposure concentrations of 10 μg.L−1 for isoproturon and 80 μg.L−1 for glyphosate, effects on growth rate and chlorophyll fluorescence were minor (< 25%), so that this initial concentration was selected to study herbicide removal. After a 4-d incubation, removal yields were 25% and 8% for isoproturon and glyphosate, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In recent decades, a new class of polymeric materials, PAMAM dendrimers, has attracted marked interest owing to their unique nanoscopic architecture and their hopeful perspectives in nanomedicine and therapeutics. However, the potential release of dendrimers into the aquatic environment raises the issue about their toxicity on aquatic organisms. Our investigation sought to estimate the toxicity of cationic PAMAM dendrimers on the green alga, Chlamydomonas reinhardtii. Algal cultures were exposed to different concentrations (0.3–10mgL−1) of low dendrimer generations (G2, G4 and G5) for 72h. Potential adverse effects on Chlamydomonas were assessed using esterase activity (cell viability), photosynthetic O2 evolution, pigments content and chlorophyll a fluorescence transient. According to the median inhibitory concentration (IC50) appraised from esterase activity, toxicity on cell viability decreased with dendrimer generation number (2, 3 and 5mgL−1 for G2, G4 and G5 dendrimers, respectively). Moreover, the three generations of dendrimers did not induce the same changes in the photosynthetic metabolism of the green alga. O2 evolution was stimulated in cultures exposed to the lowest generations tested (i.e. G2 and G4) whereas no significant effects were observed with G5. In addition, total chlorophyll content was increased after G2 treatment at 2.5mgL−1. Finally, G2 and G4 had positive effects on photosystem II (PSII): the amount of active PSII reaction centers, the primary charge separation and the electron transport between QA and QB were all increased inducing activation of the photosynthetic electron transport chain. These changes resulted in stimulation of full photosynthetic performance. [Copyright &y& Elsevier]

Abstract: The antiepileptic drug carbamazapine (CBZ) readily persists in sewage-water treatment plant wastewaters and finds its way into receiving water bodies. Our study sought to examine the bioaccumulation and toxicity of CBZ using an experimental aquatic trophic chain composed of the green alga, Pseudokirchneriella subcapitata, the crustacean, Thamnocephalus platyurus, and the cnidarian, Hydra attenuata. Bioaccumulation of CBZ was estimated by liquid chromatography–tandem mass spectrometry and revealed bioaccumulation factors of 2.2 and 12.6, respectively, in algae and crustaceans. No significant bioaccumulation was observed in H. attenuata. In T. platyurus, a strong stimulation of global heme oxidase (HO) (76%), and glutathione-S-transferase activity (130%) but a drastic inhibition of cytochrome P450 3A-like activity was found which suggests alteration of enzyme activity by CBZ. However, in the hydranth H. attenuata, an increase in both global cytochrome and cytochrome P450 3A-like activity was found, while GST activity was inhibited. Lipid peroxidation was reduced in T. platyurus and H. attenuata suggesting that redox activity of the lipophilic CBZ was at play. This study highlighted the processes of carbamazepine toxicity transfer between trophic levels in aquatic organisms. [ABSTRACT FROM AUTHOR]

The rate of removal of two fungicides (dimethomorph and pyrimethanil) from water by five macrophyte species (L. minor, S. polyrhiza, C. aquatica, C. palustris and E. canadensis) was assessed in laboratory tests. In order to assure that these studies were performed with healthy plants the effects of the fungicides on chlorophyll fluorescence were studied as well. At exposure concentrations of 600μgL−1 the effects of the fungicides on chlorophyll fluorescence were minor, so that this initial concentration level was selected for the fungicide removal rate tests. The removal yields during the 4-d test periods varied from 10% to 18% and 7% to 12% for dimethomorph and pyrimethanil, respectively. The maximum removal rate during the 4-d test period was 48μgg−1 fresh weight (FW) for dimethomorph and 33μgg−1 FW for pyrimethanil. L. minor and S. polyrhiza showed the highest removal efficiency for the two fungicides. [Copyright &y& Elsevier]

Abstract: Analysis of fast chlorophyll fluorescence rise OJIP was carried out to assess the impact of diuron, paraquat and flazasulfuron on energy fluxes and driving forces for photosynthesis in Lemna minor. Results showed that diuron and paraquat treatment produced major changes in electron transport in active reaction centres (RCs). However, diuron had a more pronounced effect on the yield of electron transport per trapped exciton (ψ 0) than on the yield of primary electron transport showing that dark reactions are more sensitive to diuron than light-dependent reactions. In contrast, paraquat treatment effects were not due to a target-specific action on those dark and light reactions. Paraquat also induced a marked surge in the total absorption of photosystem II (PSII) antenna chlorophyll per active RC displaying a large increase of the dissipation of excess energy through non-photochemical pathways (thermal dissipation processes). Flazasulfuron induced a slight decrease of both the total driving force for photosynthesis and the quantum yield of electron transport beyond Q A − combined to a small but significant increase of the non-photochemical energy dissipation per RC (DI0/RC). We conclude that energy fluxes and driving force for photosynthesis generate useful information about the behaviour of aquatic plant photosystems helping to localize different target sites and to distinguish heterogeneities inside the PSII complexes. Regardless of the active molecule tested, the DFABS, , DI0/RC and/or ET0/RC parameters indicated a significant variation compared to control while (F V/F M) showed no significant inhibition suggesting that those parameters are more sensitive for identifying a plant’s energy-use efficiency than the maximum quantum yield of primary PS II photochemistry alone. [Copyright &y& Elsevier]

This study sought to develop a convenient and sensitive method to measure carbamazepine in biological tissues. Levels of carbamazepine were quantified with a competitive enzymatic immunoassay using a peroxidase label with fluorescence detection. The assay is sensitive with a detection limit of 0.7 pg per well. The 96-well format of the assay permits rapid analysis of more than 100 samples per day. Testing with freshwater mussel (Elliptio cornplanata) soft tissue homogenate extracts revealed no significant matrix interferences at dilutions of at least 10-fold with good recovery of the compound. This cost-effective multi-well method allows studying the bioavailability and accumulation of this persistent xenobiotic in aquatic organisms. [ABSTRACT FROM AUTHOR]

The sensitivity of different physiological parameters in Scenedesmus obliquus and Lemna minor exposed to herbicide (flumioxazin) was investigated to indicate the most convenient and sensitive parameter. To assess toxicity of flumioxazin, we used a panel of biomarkers: pigment contents, chlorophyll fluorescence parameters and antioxidative enzyme activities. Algae and duckweed were exposed to 48-h IC50 for growth rate. In L. minor, the sensitivity of the parameters was as follows: QN>Oxygen emission>ΦsPSII>QP>ΦPSII>CAT, GR>Pigment>APO>Growth. For S. obliquus, this ranking was as follows: CAT>Oxygen emission>QP>APO>GR>Pigment>ΦsPSII>Growth>ΦPSII>QN (from the greatest to the least sensitive). The results demonstrated that the observed toxicity is related not only to interspecific variations but also to the selected parameter. [Copyright &y& Elsevier]

Investigates the effects of diuron and its derivatives on Lemma gibba duckweed using a fluorescence toxicity index. Fluorescence toxicity index; Contributor to water pollution; Evaluation of water quality polluted with herbicides.

In etiolated leaves, saturating flash of 200 ms induces phototransformation of protochlorophyllide (Pchlide) F655 into chlorophyllide (Chlide), then into Chi through reactions which do not need light sensibilisation. The synthesis of Chi is known to be slowed down in etiolated leaves exposed to desiccation stress. In order to analyse the intensity and time-course of Chlide transformation into Chi, we used the fluorescence emission of etiolated leaves previously exposed to a 200 ms saturating flash. We used lowtemperature fluorescence spectroscopy to reveal the inhibition site of Chi synthesis in etiolated barley leaves exposed to water stress. Shibata shift appears as the main target point of the water deficit. It was found that water deficit inhibits partially active Pchlide F655 regeneration. Also, esterification of Chlide into Chi is impaired. It appears that these inhibitory effects alter the appearance of PSII active reaction centres. [ABSTRACT FROM AUTHOR]

Abstract: Aquatic plants take up, transform and sequester organic contaminants and may therefore be used in phytoremediation for the removal of pollutants from wastewaters. A better understanding of factors affecting the rate of contaminant uptake by aquatic plants is needed to improve engineered systems for removal of pollutants from wastewaters. This work focused on the influence of initial concentrations of pesticide and population density of plants on toxicity and uptake of the fungicide dimethomorph by two duckweed species. An increased sensitivity to dimethomorph was observed with increasing duckweed population density. Less light, due to crowding, may explain this higher sensitivity and reduced removal rate. A positive relationship was also found between toxicity or contaminant uptake and initial pesticide concentration with a maximal removal of 41 and 26µgg−1 fresh weight of dimethomorph (at 600µgL−1 of dimethomorph and an initial density of 0.10g E-flask−1) by Lemna minor and Spirodela polyrhiza, respectively. This research also indicated that these aquatic plants can efficiently eliminate organic contaminants and may ultimately serve as phytoremediation agents in the natural environment. [Copyright &y& Elsevier]

Abstract: Remediation capacities of two freshwater microalgae, Scenedesmus obliquus and Scenedesmus quadricauda, were assessed for the removal of two fungicides (dimethomorph and pyrimethanil) and one herbicide (isoproturon) from their medium. To ensure these studies were performed with healthy algae, pesticide effects where first apprehended on chlorophyll a fluorescence emission and growth rate. After a 4d-exposure to 600μgL−1 of dimethomorph or pyrimethanil, or to 10μgL−1 of isoproturon, algal growth rate and some of their photosynthetic processes were weakly affected (<30% variation). The pesticide removal percentage of Scenedesmus cells reached a maximum of 10%, 24% and 58% for pyrimethanil, dimethomorph and isoproturon, respectively. In parallel, the maximum removal rate was 36 and 40μg×10−9 cells for dimethomorph, 17 and 26μg×10 − 9 cells for pyrimethanil, 2 and 2μg×10−9 cells for isoproturon, in the presence of Sc. obliquus and Sc. quadricauda, respectively. Results showed that Sc. quadricauda was more effective in the removal of dimethomorph and pyrimethanil compared to Sc. obliquus. [Copyright &y& Elsevier]

Abstract: Pesticides are being detected in water bodies on an increasingly frequent basis. The present study focused on the phytoremediation potential of selected aquatic plants to remove phytosanitary products from contaminated water. We investigated the uptake capacity of Lemna minor (L. minor), Elodea canadensis (E. canadensis) and Cabomba aquatica (C. aquatica) on three pesticides: copper sulphate (fungicide), flazasulfuron (herbicide) and dimethomorph (fungicide). Pesticide toxicity was evaluated by exposing plants to five concentrations (0–1mgL−1) in culture media for 7d using chlorophyll fluorescence as a biomarker. The toxicity of the contaminants was the same for all the aquatic plants studied and occurred in this descending order of toxicity: flazasulfuron>copper>dimethomorph. We found that L. minor had the most efficient uptake capacity, followed by E. canadensis and then C. aquatica. The maximum removal rate (μgg−1 fresh weightd−1) of copper, flazasulfuron and dimethomorph was 30, 27 and 11, respectively. [Copyright &y& Elsevier]

A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the determination of carbamazepine in microgram quantities of crustacean Thamnocephalus platyurus and the algae Pseudokirchneriella subcapitata at the ng L(-1) level. This fully validated method applied to a bioaccumulation study was found suitable for the detection of carbamazepine in small aquatic tissues.