Antioxidant responses and metal accumulation in tissues of Nile tilapia Oreochromis niloticus under Zn,Cd and Zn + Cd exposures

We investigated the effects of Zn, Cd and a Zn + Cd mixture on antioxidant parameters and metal accumulation in Oreochromis niloticus. Fish were exposed to 0.5 and 5.0 mg l^?1 Zn, 0.1 and 1.0 mg l^?1 Cd, and 0.5 mg l^?1 Zn + 0.1 mg l^?1 Cd and 5.0 mg l^?1 Zn + 1.0 mg l^?1 Cd mixtures for 7 and 28 days to determine Zn and Cd accumulation, reduced glutathione (GSH) level and glucose‐6‐phosphate dehydrogenase (G6PD) activity in gill and liver. There was increasing accumulation of the metals in the tissues with increasing concentrations of metals in the exposure medium and with increasing duration of exposure (except at the lower concentration of Zn). Concentration of metals in the tissues of fish exposed to the Zn + Cd combination were significantly lower than in fish exposed to the single metal. The highest metal accumulation was observed in the liver. Exposure to the heavy metals affected the antioxidant parameters in the tissues, with both GSH level and G6PD activity in the gill and liver being increased under Zn, Cd and Zn + Cd exposures, especially in their higher concentrations. These increases in the antioxidant responses were higher with the Cd alone, and in combination with Zn, than with Zn alone. Furthermore, GSH level and G6PD activity increased with increasing exposure period only for Cd alone, and in Cd combination with Zn. The results indicate that O. niloticus resisted oxidative stress induced by heavy metal exposure by antioxidant mechanisms. Copyright © 2008 John Wiley & Sons, Ltd.     

Chronic toxicity of parabens and their chlorinated by‐products in Ceriodaphnia dubia

The chronic toxicity of 12 compounds of parabens and their chlorinated by‐products was investigated using 7‐day Ceriodaphnia dubia test under static renewal condition in order to generate information on how to disinfect by‐products of preservatives that are discharged in aquatic systems. The mortality and inhibition of reproduction tended to increase with increasing hydrophobicity and decreased with the degree of chlorination of parabens. The EC₅₀ values for mortality, offspring number, and first brood production ranged between 0.30–3.1, 0.047–12, and 1.3–6.3 mg L^?1, respectively. For the number of neonates, the most sensitive endpoint, the no‐observed‐effect concentration (NOEC) and lowest‐observed‐effect concentration (LOEC) values ranged from 0.63 to 10 mg L^?1 and from 1.2 to 19 mg L^?1, respectively. Methylparaben (MP), benzylparaben (BnP), and dichlorinated BnP (Cl₂BnP) elicited a significant decrease in offspring numbers even at their lowest concentration tested; the NOEC for these compounds was determined to be less than the lowest test concentration (1.3, 0.04, and 0.63 mg L^?1 for MP, BnP, and Cl₂BnP, respectively). Propylparaben (PP), chlorinated PP, isopropylparaben (iPP), and chlorinated iPP exhibited nonmonotonic concentration‐dependent response; their NOEC and LOEC values could not be determined. The multivariate approach involving principal component analysis and hierarchical cluster analysis revealed four groups that corresponded to the toxicological profiles of parabens. Our results suggested that disinfection of parabens by chlorination could reduce aquatic toxicity of original compounds. The findings obtained in our study together with the data available on paraben concentrations in aquatic systems can be used to perform preliminary risk assessment by comparing the predicted environmental concentration (PEC) with the predicted no‐effect concentration (PNEC) for the marine aquatic environment. The calculated PEC/PNEC ratios ranged from 0.0012 to 0.2, with the highest value observed in MP. This suggested that there are negligible environmental risks for aquatic organisms at current use levels. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 664–673, 2015.     

Acute toxicity of 50 metals to Daphnia magna

Metals are essential for human life and physiological functions but may sometimes cause disorders. Therefore, we conducted acute toxicity testing of 50 metals in Daphnia magna: EC50s of seven elements (Be, Cu, Ag, Cd, Os, Au and Hg) were < 100 µg l^?1; EC50s of 13 elements (Al, Sc, Cr, Co, Ni, Zn, Se, Rb, Y, Rh, Pt, Tl and Pb) were between 100 and 1000 µg l^?1; EC50s of 14 elements (Li, V, Mn, Fe, Ge, As, In, Sn, Sb, Te, Cs, Ba, W and Ir) were between 1,001 and 100,000 µg l^?1; EC50s of six elements (Na, Mg, K, Ca, Sr and Mo) were > 100,000 µg l^?1; and. 7 elements (Ti, Zr, Bi, Nb, Hf, Re and Ta) did not show EC50 at the upper limit of respective aqueous solubility, and EC50s were not obtained. Ga, Ru and Pd adhered to the body of D. magna and physically retarded the movement of D. magna. These metals formed hydroxides after adjusting the pH. Therefore, here, we distinguished this physical effect from the physiological toxic effect. The acute toxicity results of 40 elements obtained in this study were not correlated with electronegativity. Similarly, the acute toxicity results of metals including the rare metals were also not correlated with first ionization energy, atomic weight, atomic number, covalent radius, atomic radius or ionic radius. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of a pre‐incubation period on the photoinduced toxicity of polycyclic aromatic hydrocarbons to the luminescent bacterium Vibrio fischeri

Irradiation of polycyclic aromatic hydrocarbons (PAHs) in aqueous solution with simulated solar radiation (SSR; a light source with a visible light : UV‐A : UV‐B ratio similar to that of sunlight) can greatly enhance their toxicity. Two microbial toxicity tests with Vibrio fischeri were used to investigate the effect of composition of the growth medium and pre‐incubation on the photoinduced toxicity of PAHs. The assays were a short‐term test (15 min) and long‐term test (18 h). Both assays were carried out in SSR and darkness to examine for photoinduced toxicity of PAHs. For the short‐term toxicity assay, inhibition of bacterial luminescence was measured. For the long‐term toxicity assay, both inhibition of bacterial luminescence and inhibition of growth were recorded. To broaden this test, V. fischeri cells were pre‐incubated with PAHs in medium without a carbon source (minimal medium) for 8 h to facilitate assimilation and photooxidation of the contaminants, and to prevent bacterial growth at the outset of the assay. V. fischeri was more sensitive in minimal medium than in complex medium in both the short‐ and long‐term toxicity assays. Moreover, in the long‐term assay, SSR greatly increased toxicity, especially if there was a pre‐incubation period in minimal medium. This indicates that both assimilation and photooxidation of PAHs are important to their toxicity to V. fischeri. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 277–286, 2001     

Toxicity evaluation of water samples collected near a hospital waste landfill through bioassays of genotoxicity piscine micronucleus test and comet assay in fish Astyanax and ecotoxicity Vibrio fischeri and Daphnia magna

In this study, we analyzed samples of water from a river and a lake located near a hospital waste landfill with respect to physico-chemical parameters and conducted bioassays of ecotoxicity using Vibrio fischeri and Daphnia magna, which are species commonly used to evaluate the water toxicity. We also evaluated damage to the genetic material of fish (Astyanax sp. B) that were exposed (96 h) to water from these two sites that were located near the tank ditch, using the alkaline comet assay and the piscine micronucleus test. Parameters including aluminum, manganese, biochemical oxygen demand, sulfide, conductivity, phenol, total coliforms and Escherichia coli counts, were above acceptable levels that have been established in environmental legislation. However, the toxicity bioassays that we carried out in Vibrio fischeri and Daphnia magna and the piscine micronucleus test in fish showed no immediate risk due to acute effects. Based on the results of the comet assay, however, it was possible to detect damage to genetic material in fish that were acutely exposed in the laboratory to water samples from the river and lake that are located near the trench septic tank. Thus, our results suggest that tests beyond those usually employed to test water toxicity, such as the comet assay we used in the fish, are required to assess the toxicity of water with greater accuracy.     

Sub-lethal effects of acetone on <Emphasis Type="Italic">Daphnia magna</Emphasis>

There is increasing concern about the sub-lethal effect of hydrophobic chemicals in the water medium. Even though acetone is a commonly used solvent in toxicity testing, few studies have focussed on its chronic toxicity to Daphnia magna and the available results are often contradictory. In this study, acetone was tested on D. magna in a 21-day exposure experiment and the effects on mortality, fertility and morphology of exposed organisms (F₀) and offspring (F₁–F₂, reared without acetone) were evaluated. No significant reduction of survival was observed with increasing concentrations, and no significant reduction in fecundity in any treatment group in terms of average number of daphnids per mother was observed. Abnormal development of second antennae was observed on F₁ from F₀ exposed to 79 mg l⁻¹ solvent. The ET50 of acetone on the number of mothers that produced deformed offspring over time was 12.5 days. Our results suggest that the acetone concentration should not exceed 7.9 mg l⁻¹, which is 10 times less than the allowed concentration as determined by OECD chronic assays on D. magna. More attention should be paid to small, water-soluble molecules usually considered of low concern for chronic toxicity because they might affect other metabolic pathways.     

Selective blockade of mGlu5 metabotropic glutamate receptors is hepatoprotective against fulminant hepatic failure induced by lipopolysaccharide and d‐galactosamine in mice

This study was designed to investigate the influence of 2‐methyl‐6‐phenylethynyl pyridine hydrochloride (MPEP), an antagonist of metabotropic glutamate receptor subtype 5, in lipopolysaccharide (LPS) and d‐ galactosamine (d‐ GalN)‐induced fulminant hepatic failure in mice. Mice were given an intraperitoneal injection of 50 µg kg^?1 LPS and 500 mg kg^?1 d‐ GalN. MPEP (1, 5 and 25 mg kg^?1) was administered intraperitoneally 1 h before LPS/d‐ GalN injection. Twenty‐four hours after administration of LPS/d‐ GalN, plasma was collected and used for biochemical assays. Mice were euthanized and histological analysis and toxicological parameters were carried out in the liver. MPEP, at all doses tested, protected against the increase in aspartate and alanine aminotransferase activities induced by LPS/d‐ GalN exposure. Ascorbic acid levels were not altered in all experimental groups. Glutathione S‐transferase activity was increased by administration of LPS/d‐ GalN and MPEP did not modify the enzyme activity in mice. MPEP, at the doses of 5 and 25 mg kg^?1, was effective in protecting against the decrease in catalase activity caused by LPS/d‐ GalN administration in mice. The histological data showed that sections of liver from LPS/d‐ GalN‐exposed mice presented extensive injuries. MPEP, at all doses tested, reduced the scores of liver damage and markedly ameliorated the degree of liver damage. The hepatoprotective effect of MPEP on fulminant hepatic failure induced by LPS and d‐ GalN in mice was demonstrated. Copyright © 2009 John Wiley & Sons, Ltd.     

Chronic toxicity of chlordane to Daphnia magna and Ceriodaphnia dubia: A comparative study

Chronic toxicity of chlordane, an organochlorine insecticide, was assessed on Ceriodaphnia dubia under standardized conditions of testing. Results were compared to Daphnia magna to determine the sensitivity of the two freshwater cladoceran species to this persistent organic pollutant (POP) and to explore the possibility of using the 7‐day C. dubia test as an alternative to the 21‐day D. magna test in chronic toxicity assessment of POPs. The NOEC‐7d value of chlordane on reproduction of C. dubia (2.9 μg/L) was much higher than the NOEC‐21d value of D. magna (0.18 μg/L), attesting that the 7‐day test on C. dubia was less sensitive than the 21‐day reproduction test on D. magna to chlordane. However, extending the period of exposure of C. dubia to chlordane from 7 to 14 days led to a NOEC‐14d value similar to the NOEC‐21d value in D. magna (0.18 μg/L). This study highlights the usefulness of prolonging the exposure time of the reproduction test in C. dubia from 7 to 14 days to increase the performances of the reproduction test on C. dubia for assessing chronic toxicity of POPs. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

Effect of culture conditions and mother’s age on the sensitivity of Daphnia magna Straus 1820 (Cladocera) neonates to hexavalent chromium

Daphnia magna is a freshwater cladoceran used worldwide as test organism in aquatic toxicity assays. In Mexico there is a test protocol for this species; nevertheless, some aspects of the controlled neonate production, as well as the possible consequences of the reproducers’ culture conditions on the response of neonates to the toxic substance, are not completely known. In the present study, we evaluated the effect of temperature and photoperiod on the acute toxicity of Cr(VI) in D. magna neonates, aimed at providing useful information on the Median Lethal Concentration (LC₅₀) to this heavy metal, which is used as reference toxicant in some laboratories. D. magna was cultured at 20 and 25°C, in combination with two photoperiod values: 16:8 and 12:12 (light:dark) during 40 days; the green microalga Ankistrodesmus falcatus (4×10⁵ cells ml⁻¹) was supplied as food. Once the reproduction began, the neonates were removed and acute toxicity bioassays at 20 and 25°C were performed, by exposing them to hexavalent chromium. We also determined changes in neonates’ size at 20 and 25°C. Chromium toxicity increased along with increasing temperatures, and LC₅₀ values were slightly lower for the first and last clutches in the observed period, but these findings are not conclusive because of the large variability recorded. The average LC₅₀’s were 0.2076±0.0164 mg l⁻¹ (at 20°C) and 0.1544±0.0175 mg l⁻¹ (at 25°C). The reproducers’ culture temperature had no effect on neonates’ sensitivity to chromium, in spite of performing the tests at temperatures either lower or higher than those at which the neonates had been obtained. The length of neonates produced during the first two clutches (<1.25 mm) was significantly lower than that measured in neonates of following reproductions (>1.3 mm), and were smaller at 25°C; however, this did not seem to affect their sensitivity to chromium.     

Acute and chronic toxicity of Betanal(®)Expert and its active ingredients on nontarget aquatic organisms from different trophic levels

As a way to improve the efficacy to target organisms, new pesticide generation is based on technologically advanced coformulations of two or more active ingredients. One example is Betanal®Expert, a postemergence herbicide composed of an Advanced Micro Droplet coformulation of phenmedipham, desmedipham, and ethofumesate. Although its composed formulation brings an increase in the pesticide performance, it can also enhance its toxicity to nontarget species. Therefore, the present study intends to contribute with relevant information on ecotoxicological effects of Betanal®Expert and its active ingredients on a battery of bioassays using aquatic species from different trophic levels: bacteria (Vibrio fischeri), microalgae (Pseudokirchneriella subcapitata, Chlorella vulgaris, and Chlamydomonas pseudocostata), macrophyte (Lemna minor), and cladocerans (Daphnia magna and Daphnia longispina) species. Across the organisms tested and endpoints measured, different responses concerning the toxicity of the active ingredients were found: (i) phenmedipham was the most toxic to V. fischeri and L. minor; (ii) desmedipham was the most toxic to P. subcapitata, D. magna, and D. longispina; (iii) and ethofumesate was the most toxic to C. pseudocostata and C. vulgaris. Furthermore, for C. pseudocostata and daphnids, the toxicity observed for some active ingredients was higher than the toxicity of the commercial formulation. In fact, in an attempt to evaluate the contribution of each active ingredient to the overall toxicity of Betanal®Expert, it was observed that, in general, the toxicity values obtained for desmedipham and phenmedipham were close or even lower to the values determined for Betanal®Expert, indicating that the ethofumesate can act as an antagonist in the three‐way coformulation. In spite of the most impaired species being the photosynthetic ones, this study also showed pernicious effects on nonphotosynthetic organisms with distinct target sites. Therefore, our results underline the importance of clarifying the mode of action and metabolic pathways of these compounds on nonphotosynthetic species. © 2011 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

Effect of astragaloside IV on the embryo‐fetal development of Sprague–Dawley rats and New Zealand White rabbits

Astragaloside IV, a natural product purified from the Chinese medicinal herb Astragalus membranaceus (Fisch) Bge, is now being developed as a cardioprotective agent for treating cardiovascular diseases. In the present study developmental toxicity of astragaloside IV in Sprague–Dawley rats and New Zealand White rabbits was evaluated by intravenously administering astragaloside IV daily to rats at 0.25, 0.5 and 1.0 mg kg^?1 on gestation days 6–15, and to rabbits at 0.5, 1.0 and 2.0 mg kg^?1 daily on gestation days 6–18. Reproductive parameters were determined and fetuses were examined for external, visceral and skeletal malformations. There was significant difference in total weight gain during and after treatment between the control group and 1.0 mg kg^?1 group in rats. The percentage of fetal deaths in 0.5 and 1.0 mg kg^?1 rat groups was significantly higher than that of the control group, and higher in all treatment groups than in the control in rabbits. These results indicated that astragaloside IV was maternally toxic at 1.0 mg kg^?1 in rats and fetotoxic at a dose higher than 0.5 mg kg^?1, but devoid of teratogenic effects in rats and rabbits. In light of these findings it is perhaps prudent to advise caution to women who might use astragaloside IV to combat cardiovascular disease during pregnancy. Copyright © 2009 John Wiley & Sons, Ltd.     

Reproduction recovery of the crustacean Daphnia magna after chronic exposure to ibuprofen

In mammals, the pharmaceutical ibuprofen (IB), a non-steroidal anti-inflammatory drug, primarily functions by reversibly inhibiting the cyclooxygenase (COX) pathway in the synthesis of eicosanoids (e.g. prostaglandins). Previous studies suggest that IB may act in a similar manner to interrupt production of eicosanoids reducing reproduction in the model crustacean Daphnia magna. On this basis withdrawal of IB should lead to the recovery of D. magna reproduction. Here we test whether the effect of IB is reversible in D. magna, as it is in mammals, by observing reproduction recovery following chronic exposure. D. magna (5-days old) were exposed to a range of IB concentrations (0, 20, 40 and 80 mg l⁻¹) for 10 days followed by a 10 day recovery period in uncontaminated water. During the exposure period, individuals exposed to higher concentrations produced significantly fewer offspring. Thereafter, IB-stressed individuals produced offspring faster during recovery, having similar average population growth rates (PGR) (1.15–1.28) to controls by the end of the test. It appears that maternal daphnids are susceptible to IB during egg maturation. This is the first recorded recovery of reproduction in aquatic invertebrates that suffered reproductive inhibition during chronic exposure to a chemical stressor. Our results suggest a possible theory behind the compensatory fecundity that we referred to as ‘catch-up reproduction’.     

Toxicity assessment of Tehran water treatment sludges using bioassay tests

The 48-, 72- and 96-h acute toxicity and 14-d chronic toxicity of the sludge of treatment plant No. 1, 3 and 5 were examined based on the survival percentage and fertility changes of Daphnia magna and Eisenia fetida. The highest percentage of D. magna death in the acute toxicity test appeared in treatment plant No. 1 sludge sample. The 48-h and 72-h LC₅₀ of treatment plant No. 1 sludge on D. magna were calculated to be 86.81 and 44.307% volume of the sludge, respectively. The release of untreated sludge into the environment could adversely affect the life of organisms.     

Toxicity and genotoxicity of organic and inorganic nanoparticles to the bacteria Vibrio fischeri and Salmonella typhimurium

The present work aimed at evaluating the toxicity and genotoxicity of two organic (vesicles composed of sodium dodecyl sulphate/didodecyl dimethylammonium bromide—SDS/DDAB and of monoolein and sodium oelate—Mo/NaO) and four inorganic (titanium oxide—TiO₂, silicon titanium—TiSiO₄, Lumidot^™-CdSe/ZnS, and gold nanorods) nanoparticles (NP), suspended in two aqueous media (Milli Q^? water and American Society for Testing and Materials (ASTM) hardwater), to the bacteria Vibrio fischeri (Microtox^? test) and Salmonella typhimurium-his ⁻ (Ames^? test with strains TA98 and TA100). Aiming a better understanding of these biological responses physical and chemical characterization of the studied NP suspensions was carried out. Results denoted a high aggregation state of the NP in the aqueous suspensions, with the exception of SDS/DDAB and Mo/NaO vesicles, and of nanogold suspended in Milli Q water. This higher aggregation was consistent with the low values of zeta potential, revealing the instability of the suspensions. Regarding toxicity data, except for nano TiO₂, the tested NP significantly inhibited bioluminescence of V. fischeri. Genotoxic effects were only induced by SDS/DDAB and TiO₂ for the strain TA98. A wide range of toxicity responses was observed for the six tested NP, differing by more than 5 orders of magnitude, and suggesting different modes of action of the tested NP.     

Ecotoxicity of pesticide formulations and their mixtures: the case of potato crops in Costa Rica

Despite their environmental implications, ecotoxicological information regarding pesticide mixtures is relatively scarce. This study aimed to determine the ecotoxicity of individual pesticide formulations and their mixtures (insecticides and fungicides), which are applied during the production cycle of potato, according to agricultural practices from a Latin American region in Costa Rica. Two benchmark organisms were employed: Daphnia magna and Lactuca sativa. First, the evaluation of individual formulations (chlorothalonil, propineb, deltamethrin+imidacloprid, ziram, thiocyclam and chlorpyrifos) revealed differences between available EC₅₀ for active ingredients (a.i.) and their respective formulations toward D. magna; on the contrary, no information could be retrieved from scientific literature for comparison in the case of L. sativa. In general, acute toxicity was higher toward D. magna than L. sativa. Moreover, interactions could not be determined on L. sativa, as the chlorothalonil formulation was not toxic at high levels and the concentration-response to propineb could not be fitted to obtain an IC₅₀ value. The commercial formulation composed of deltamethrin+imidacloprid followed the concentration addition model (when compared with parameters retrieved from individual a.i.) and the other three mixtures evaluated (I: chlorothalonil-propineb-deltamethrin+imidacloprid; II: chlorothalonil-propineb-ziram-thiocyclam; III: chlorothalonil-propineb-chlorpyrifos) produced an antagonistic effect on D. magna, thus suggesting less acute toxicity than their individual components. Subsequent chronic studies showed that one of the most toxic mixtures (II) negatively affected D. magna reproduction at sublethal concentrations indicating that this mixture poses a risk to this species if these pesticides co-exist in freshwater systems. These findings provide useful data to better estimate the impact of real agricultural practices related to the use of agrochemicals.

     

Concentration of dioxin and screening level ecotoxicity of pore water from bottom sediments in relation to organic carbon contents

The information about concentrations of dioxin in pore water, ecotoxicity and DOC and TOC content can be key factor for the prediction of the fate of dioxins in the aquatic environment as well as an ecological risk assessment. The aims of the study were to assess the concentration of PCDDs/PCDFs and ecotoxicity of pore water and to compare above results in relation to the dissolved organic carbon (DOC) and total organic carbon (TOC) content. The concentration of dioxins was assessed using an enzyme-linked immunoassay test, while the ecotoxicity of pore water was determined using a crustacean Daphnia magna and bacteria Aliivibrio fischeri. The studies were conducted on two different dammed reservoirs Rożnów (catchment basin of an agricultural character) and Rybnik (catchment basin of an industrial character) located in southern Poland. The concentration of dioxins in pore water was between 8.56 to 90.92 ng EQ/L, with a significantly higher concentration in the pore water from the Rożnów Reservoir than the Rybnik Reservoir. The DOC content in pore water was from 30.29 to 63.02 mg/L (Rożnów Reservoir) and from 35.46 to 60.53 mg/L (Rybnik Reservoir). Higher toxic responses were recorded for A. fischeri than for D. magna. Moreover a significantly higher toxicity for both tested organisms was indicated in pore water from the Rożnów Reservoir. Besides of TOC and DOC, the fine fractions of the sediments were particularly important in the concentration of dioxin in pore water. The other pore water parameters, such as pH and EC can influence the toxicity of water for organisms. The result indicate complex relationships between the PCDD/F, ecotoxicity and DOC, TOC concentration in pore water and confirms that these parameters are important in terms of water environmental contamination.

     

Acute toxicity evaluation of olive oil mill wastewaters: A comparative study of three aquatic organisms

Acute toxicity of olive mill wastewaters (traditional and continuous processes) collected from different regions of Portugal was evaluated using three test species (Vibrio fischeri formerly Photobacterium phosphoreum, Thamnocephalus platyurus, and Daphnia magna) and correlated with several physical and chemical parameters. Acute toxicity of these effluents, expressed in LC₅₀ or EC₅₀, ranged from: 0.16 to 1.24% in Microtox test, 0.73 to 12.54% in Thamnotoxkit F test, and 1.08 to 6.83% in Daphnia test. These values reflect the high toxicity of the olive mill wastewaters to all test species. Statistical analysis of the results shows a high correlation between the two microcrustacean bioassays. Microtox test did not correlate significantly with the other bioassays used. A significative correlation (p≤0.05) could also be established between L(E)C₅₀ obtained in the microcrustacean tests and some physicochemical parameters of the effluent. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 263–269, 1999     

Toxicity of pamam‐coated gold nanoparticles in different unicellular models

Polyamidoamine (PAMAM) dendrimers are used for many pharmaceutical and biomedical applications. However, the toxicological risks of several PAMAM‐based compounds are still not fully evaluated, despite evidences of PAMAM deleterious effects on biological membranes, leading to toxicity. In this report, we investigated the toxicity of generation 0 PAMAM‐coated gold nanoparticles (AuG0 NPs) in four different models to determine how different cellular systems are affected by PAMAM‐coated NPs. Toxicity was evaluated in two mammalian cell lines, Neuro 2A and Vero, in the green alga Chlamydomonas reinhardtii and the bacteria Vibrio fischeri. AuG0 NP treatments reduced cell metabolic activity in algal and bacterial cells, measured by esterase enzymatic activity (C. reinhardtii) and luminescence emission (V. fischeri). EC50 value after 30 min of treatment was similar in both organisms, with 0.114 and 0.167 mg mL^?1 for C. reinhardtii and V. fischeri, respectively. On the other hand, AuG0 NPs induced no change of mitochondrial activity in mammalian cells after 24 h of treatment to up to 0.4 mg mL^?1 AuG0 NPs. Change in the absorption spectra of AuG0 NP in the mammalian cell culture media may indicate an alteration of NP properties that contributed to the low toxicity of AuG0 NPs in mammalian cells. For a safe development of PAMAM‐based nanomaterials, the difference of sensitivity between mammalian and microbial cells, as well as the modulation of NPs toxicity by medium properties, should be taken into account when designing PAMAM NPs for applications that may lead to their introduction in the environment. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 328–336, 2014.     

Comparison of the Ceriodaphnia dubia and MicrotoxR inhibition tests for toxicity assessment of industrial and municipal wastewaters

Toxicity tests on effluents from industrial production facilities, municipal and industrial wastewater treatment plants, and stormwater runoff were conducted with the freshwater invertebrate, Ceriodaphnia dubia, and the marine luminescent bacterium, Vibrio fischeri in the Microtox^R test system (Microtox is a registered trademark of AZUR Environmental, Carlsbad, CA.). Percent mortalities of C. dubia in whole effluent, generated in 24- and 48-h exposure periods during the conductance of static-renewal acute and chronic tests were compared with percent reductions in light output by V. fischeri after 15-min exposure periods in the Microtox Inhibition test. A total of 16 effluent and stormwater samples from seven sources were used in tests conducted over a 3-month period. Results of the Microtox Inhibition tests correctly predicted the results of C. dubia tests for all eight nontoxic samples after both 24- and 48-h exposure periods. Of three samples that were toxic to C. dubia within 24 h, the Microtox test also detected toxicity in two of those samples. Results from tests on the remaining five samples showed that while the Microtox Inhibition test indicated the presence of toxic components after 15 min exposure, C. dubia required exposure to potentially toxic samples for 48 h before producing a toxic response. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 375–382, 1999     

Caloric content of Daphnia magna as reflect of propanil stress during a short-term exposure and its relationship to long-term responses

The present study investigates energy stores changes in the aquatic invertebrate Daphnia magna following a 5-d exposure to propanil. Juveniles of D. magna were exposed to sublethal propanil concentrations (0.07, 0.10, 0.21 and 0.55 mg l^?1) which were used previously to test their effect on reproduction, growth and survival (21 days test) of D. magna. Glycogen, total lipids, proteins, and dry weight were determined in control and exposed daphnids at 24, 48, 72, 96 and 120 h. Data were used to calculate caloric content as biomarker of propanil exposure. Results showed a depletion of energy reserves in D. magna exposed to the herbicide. At 120 h of exposure to the highest propanil concentration (0.5 mg l^?1), the reduction in daphnid reserves were glycogen (28%), proteins (28%) and lipids (31%), and caloric content was reduced in 27%. On the other hand, we found a positive correlation between caloric content and the chronic parameters intrinsic rate of natural increase and offspring per female when daphnids were exposed for 120 h to the herbicide.