Reconstituted Water Research Articles

Challenges of Antibiotic Formulations and Administration in the Treatment of Bloodstream Infections in Children Under Five Admitted to Kisantu Hospital, Democratic Republic of Congo.

Severe bacterial infections in children need prompt, appropriate antibiotic treatment. We report challenges observed within a prospective, cohort study on antibiotic efficacy in non-typhi Salmonella bloodstream infection (NCT04850677) in Kisantu district hospital (Democratic Republic of Congo). Children (aged >28 days to <5 years) admitted with suspected bloodstream infection (August 1, 2021 through July 31, 2022) were enrolled and followed until day 3 or discharge for non-typhi Salmonella patients. Antibiotics were administered to 98.4% (1,838/1,867) of children, accounting for 2,296 antibiotic regimens (95.7% intravenous, 4.3% oral). Only 78.3% and 61.8% of children were, respectively, prescribed and administered antibiotics on the admission day. At least one dose was not administered in 3.6% of children, mostly because of mismatch of the four times daily cefotaxime schedule with the twice-daily administration rounds. Inappropriate intravenous administration practices included multidose use, air-venting, and direct injection instead of perfusion. There was inaccurate aliquoting in 18.0% (32/178) of intravenous ciprofloxacin regimens, and thus administered doses were >16% below the intended dose. Dosing accuracy of oral suspensions was impaired by lack of instructions for reconstitution, volume indicators, and/or dosing devices. Adult-dose tablets were split without/beyond scoring lines in 84.4% (27/32) of tablets. Poor availability and affordability of age-appropriate oral formulations contributed to low proportions of intravenous-to-oral switch (33.3% (79/237) of non-typhi Salmonella patients). Other quality issues included poor packaging, nonhomogeneous suspensions, and unsafe water for reconstitution. In conclusion, poor antibiotic products (no age-appropriate formulations, poor quality and access), processes (delayed prescription/administration, missed doses), and practices (inaccurate doses, [bio]safety risks) must be urgently addressed to improve pediatric antibiotic treatment.

Co-exposure of iron oxide nanoparticles with glyphosate herbicides in Poecilia reticulata: Fish liver damages is reversible during iron accumulation and elimination period

Iron oxide nanoparticles (IONPs) are advanced materials for water remediation technologies. It is therefore relevant to evaluate the cellular and tissue behavior of fishes in response to IONPs and their associations with agrochemicals such as glyphosate (GLY) and glyphosate-based herbicides (GBHs). Iron accumulation, tissue integrity and lipid distribution in the hepatocytes of Poecilia reticulata (guppy) were investigated in a control group and in groups exposed to soluble iron ions, namely IFe (0.3 mgFe/L), IONPs (0.3 mgFe/L), and IONPs, associated with GLY (0.65 mg/L), GBHs 0.65 mgGLY/L (IONPs + GBH1), and 1.30 mgGLY/L (IONPs + GBH2), for 7, 14, and 21 days, followed by an equal period of postexposure in clean reconstituted water. The results showed that the accumulation of iron was greater in the subjects in the IONP treatment group when compared to that in the Ife group. In addition, the subjects in the mixtures with GBHs had a greater accumulation of iron than those in the IONP + GLY treatment group. Tissue integrity assessments demonstrated an intense accumulation of lipids, formation of necrotic zones and leukocyte infiltrates in all the treated groups, with a greater quantity of lipids in the animals treated with IONP + GLY and IFe. During postexposure, the results indicated an elimination of iron in all treated groups, reaching the same level as the control group, throughout the 21 days postexposure. Thus, the damage caused to animal livers by IONP mixtures is reversible, providing promising results for the development of safe environmental remediation practices using nanoparticles.

Influence of Test Method Variables on Sensitivity of Neocloeon Triangulifer to a Reference Toxicant in Short-Term, Effluent Style Evaluations.

Recent literature has demonstrated the sensitivity of mayflies to environmental contaminants. However, to date, there are no methods approved by the US Environmental Protection Agency for using sensitive insects like mayflies in whole-effluent toxicity or receiving water toxicity tests. The parthenogenetic mayfly Neocloeon triangulifer has been shown to be amenable to continuous culture in the laboratory, and methods have been described for its use in both acute and chronic toxicity studies. The goal of the present study was to investigate aspects of N. triangulifer testing and culturing methods that might require adjustment so that they are applicable for testing effluents and receiving waters in a short-term exposure. To this end, the influence of organism age, test duration, and test temperature on sensitivity to NaCl as a reference toxicant were tested (concentrations ranging from 182 to 2489 mg/L). Further studies were conducted to assess the utility of commercially available diets and the influence of nutrient amendment of water on organism growth and sensitivity. Seven-day NaCl tests started with less than 24-h-old larvae were similar in sensitivity to 14-day and full life chronic tests, and were much more sensitive than those started with 7-day-old organisms. Reducing test temperature from 25 °C to 22 °C had a minor influence on culture timing, and little impact on sensitivity to NaCl. In other experiments, reconstituted test water supplemented with nutrients to potentially improve in-test food quality had minimal effect on growth at 7 days and did not significantly alter acute sensitivity to NaCl relative to unamended reconstituted water. A suitable commercially available, ready-to-feed diet substitute for cultured diatoms was not found. Testing N. triangulifer in effluents or receiving waters with the methods recommended will complement similar methods for Ceriodaphnia dubia. Environ Toxicol Chem 2022;41:2758-2768. © 2022 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Chloride Toxicity to Native Freshwater Species in Natural and Reconstituted Prairie Pothole Waters.

Oil and gas extraction in the Prairie Pothole Region (PPR) of the northern USA has resulted in elevated chloride concentrations in ground and surface water due to widespread contamination with highly saline produced water, or brine. The toxicity of chloride is poorly understood in the high hardness waters characteristic of the region. We evaluated the toxicity of chloride to two endemic species, Daphnia magna (water flea) and Lemna gibba (duckweed), exposed in field-collected waters (hardness ~ 3000mg/L as CaCO3) and reconstituted waters (hardness 370mg/L as CaCO3) intended to mimic PPR background waters. We also investigated the role of chloride in the toxicity of water reconstituted to mimic legacy brine-contaminated wetlands, using two populations of native Pseudacris maculata (Boreal Chorus Frog). Chloride toxicity was similar in field-collected and reconstituted waters for both D. magna (LC50s 3070-3788mg Cl-1/L) and L. gibba (IC50s 2441-2887). Although hardness can ameliorate chloride toxicity at low to high hardness, we did not observe additional protection as hardness increased from 370 to ~ 3000mg/L. In P. maculata exposures, chloride did not fully explain toxicity. Chloride sensitivity also differed between populations, with mortality at 2000mg Cl-/L in one population but not the other, and population-specific growth responses. Overall, these results (1) document toxicity to native species at chloride concentrations occurring in the PPR, (2) indicate that very high hardness in the region's waters may not provide additional protection against chloride and (3) highlight challenges of brine investigations, including whether surrogate study populations are representative of local populations.

Chironomus columbiensis (Diptera: Chironomidae) as test organism for aquatic bioassays: Mass rearing and biological traits.

Chironomidae are aquatic insects that have become a model in laboratory tests to evaluate toxic effect of different pollutants. The use of chironomids as test organisms depends on standard protocols for the rearing under laboratory conditions and expanding knowledge on its biology. We standardize a culture of C. columbiensis and analyze its life cycle under laboratory conditions. The experiments were carried out with different treatments for water, temperature, and food. As a result, a protocol was proposed for the rearing of C. columbiensis under the following conditions: semi-soft and reconstituted water, shredded paper towels as a substrate, soft aeration, temperature of 22 ± 2°C, fed with 0.3 g TetraMin® twice a week and weekly renewal of 50% of the water. Under these conditions, the duration of the life cycle was 17-31 days, with a continuous growth of 1.16 to 14.05 mm in the larval stage and an average of 530 eggs per oviposition. In comparison with other species in the family, this study indicated that C. columbiensis is a species with a short life cycle, sensible to changing conditions (e.g., temperature and food), wide distribution, so is a good organism for being used in aquatic bioassays.

Combined impact of freezing and soaking times on different cowpea varieties' flour functionality and resultant gel strength, sensory and product yield of moi-moi

&lt;abstract&gt; &lt;p&gt;The preparation of moi-moi either from cowpea flour (processed by dry-milling) or paste (processed by wet-milling) has evolved from the indigenous processing methods. Feasibly, freezing should enhance the characteristics of the cowpea grain, and when combined with conventional processing, help to improve emergent products. In this current work, therefore, the combined impact of freezing with soaking times on different cowpea varieties' flour functionality and resultant gel strength, sensory and product yield of moi-moi were studied. Analysis of flour functionality involved the determinations of moisture content, bulk density, oil absorption capacity, swelling index and water absorption capacity, whereas those of moi-moi products involved gel strength, sensory and (product) yield. Across the cowpea flour samples, the functional attributes significantly differed (p &amp;lt; 0.05). Moi-moi products' gel strength of dry-milled appeared higher than wet-milled by specific variety and soaking times. Moi-moi products' sensory attributes of taste, color, texture and general acceptability resembled (p &amp;gt; 0.05), except for the aroma (p &amp;lt; 0.05). Moi-moi products' yield varied widely (p &amp;lt; 0.05) by different reconstituted water volumes. Overall, combining freezing with conventional processing that involved reconstituted water volumes of cowpea promises an enhanced moi-moi yield.&lt;/p&gt; &lt;/abstract&gt;

Pesticide mixture toxicity to algae in agricultural streams – Field observations and laboratory studies with in situ samples and reconstituted water

Long-term pesticide water concentrations were investigated in four agricultural streams and their mixture toxicity on algae was assessed, based on realistic (i.e. observed) concentrations in laboratory tests using (i) natural weekly water samples and (ii) reconstituted pesticide-spiked water samples representing mixtures with predicted high mixture. This approach both covered the full complexity of natural water samples and the controlled approach of reconstituted water samples. Long-term monitoring data (time-integrated, weekly samples) revealed more than 11 pesticides (range 11.0 ± 0.25–24.0 ± 0.44) in 75% or more of the almost 1600 samples collected between 2002 and 2018. ∑TUalgae exceeded 0.1 for 29 observations (or 1.8%). Despite the multitude of pesticides in a sample, ∑TUalgae was frequently set by one or a few dominating pesticides that contribute to more than 90% of the mixture’s toxicity. Algal growth inhibition tests with in situ stream water showed a high frequency of inhibition, despite the low ∑TU for most of these samples (range 0.000014–0.3858). These “false positive” results were attributed to confounding effects of turbidity, the complexation of nutrients, and toxic effects of metals and/or other unknown contaminants. Algal inhibition tests with spiked reconstituted water showed significant inhibitory effects in the range of 1–10x the ∑TUalgae observed in worst-case field samples. Although these tests disregard the chemical complexity of natural water, they show that inhibitory effects of pesticides on algae may occur at the ∑TUalgae observed in monitoring. Furthermore, considering that the ∑TUalgae of stream water are based on weekly average concentrations and likely underestimate short-term peak concentrations of pesticides, these results strongly suggest that inhibitory effects on algae may occur in the agricultural streams of southern Sweden. We conjecture, however, that the rapid recovery of algae contributes to ameliorate these short-term effects and that pesticide contamination should be seen as one of many stressors in the streams that drain agricultural landscapes.

Fluorosis and infancy feeding relationship: an epidemiological study

Background: Dental fluorosis is considered mostly as an aesthetic issue that has an adverse impact on the children’s psychological health and self-esteem. The current study aimed to assess the prevalence of dental fluorosis and the association between using bottled water in infants’ formula and dental fluorosis risk factor in infancy among school children aged between 7 and 13 years in Riyadh city. Methodology: An epidemiological questionnaire-based study was carried out among students at primary public schools in Riyadh, Saudi Arabia, using a survey that was distributed to 389 primary public schools. Almost 201 students were examined using an oral diagnosis kit and an ordinary light provided by our college. The surveys were collected, and the data were analyzed using the Statistical Package for the Social Science program. Results: Out of the 201 school children who were aged 7-13 years, 124 (61.7%) had dental fluorosis, 77 (38.3%) were without fluorosis, and the fluorosis’ prevalence increased in the central incisors for 36 children (17.9%). The number of children (72) with fluorosis who used boiled bottled water with milk formula was higher than the number of children (42) with no fluorosis and who used boiled bottled water with milk formula.Conclusion: In the present study, children aged 7-13 years showed a higher prevalence of dental fluorosis (61.7%). The prevalence of dental fluorosis increased in the central incisors (36, 17.9 %), followed by the first permanent molars (31, 15.4 %), and in both (37, 18.4%). Mothers should use distilled/deionized water for reconstitution of infant formula to reduce fluoride intake.

Responses of Aquatic Nontarget Organisms in Experiments Simulating a Scenario of Contamination by Imidacloprid in a Freshwater Environment.

Several studies have indicated the presence of the neonicotinoid insecticide imidacloprid (IMI) in aquatic ecosystems in concentrations up to 320.0µgL-1. In the present study, we evaluated the effects of the highest IMI concentration detected in surface water (320.0µgL-1) on the survival of Chironomus sancticaroli, Daphnia similis, and Danio rerio in three different scenarios of water contamination. The enzymatic activities of glutathione S-transferase (GST), catalase (CAT), and ascorbate peroxidase (APX) in D. rerio also were determined. For this evaluation, we have simulated a lotic environment using an indoor system of artificial channels developed for the present study. In this system, three scenarios of contamination by IMI (320.0µgL-1) were reproduced: one using reconstituted water (RW) and the other two using water samples collected in unpolluted (UW) and polluted (DW) areas of a river. The results indicated that the tested concentration was not able to cause mortality in D. similis and D. rerio in any proposed treatment (RW, UW, and DW). However, C.sancticaroli showed 100% of mortality in the presence of IMI in the three proposed treatments, demonstrating its potential to impact the community of aquatic nontarget insects negatively. Low IMI concentrations did not offer risks to D. rerio survival. However, we observed alterations in GST, CAT, and APX activities in treatments that used IMI and water with no evidence of pollution (i.e., RW and UW). These last results demonstrated that fish are more susceptible to the effects of IMI in unpolluted environments.

Nonspecific cleavages arising from reconstitution of trypsinunder mildly acidic conditions.

Tryptic digestion of proteins followed by liquid chromatography with tandem mass spectrometry analysis is an extensively used approach in proteomics research and biopharmaceutical product characterization, owing to the high level of cleavage fidelity produced with this technique. However, nonspecific trypsin cleavages have been frequently reported and shown to be related to a number of digestion conditions and predigestion sample treatments. In this work, we reveal that, for a number of commercial trypsins, reconstitution and storage conditions can have a significant impact on the occurrence of trypsin nonspecific cleavages. We analyzed the tryptic digestion of a variety of biotherapeutics, using trypsins reconstituted under different conditions. The results indicate that, for many commercial trypsins, commonly recommended reconstitution/storage conditions (mildly acidic, e.g., 50 mM acetic acid, 1 mM HCl) can actually promote nonspecific trypsin activities, which are time dependent and can be as high as 20% in total relative abundance. In contrast, using water for reconstitution and storage can effectively limit nonspecific cleavages to 1%. Interestingly, the performances of different commercial trypsins were found to be quite distinct in their levels of nonspecific cleavages and responses to the two reconstitution conditions. Our findings demonstrate the importance of choosing the appropriate trypsin for tryptic digestion and the necessity of assessing the impact of trypsin reconstitution and storage on nonspecific cleavages. We advocate for manufacturers of commercial trypsins to reevaluate manufacturing processes and reconstitution/storage conditions to provide good cleavage specificity.

Removal of disinfection byproduct precursors and reduction in additive toxicity of chlorinated and chloraminated waters by ozonation and up-flow biological activated carbon process

The variations of disinfection byproduct (DBP) precursors and DBPs-associated toxic potencies were evaluated by ozonation, followed by a up-flow biological activated carbon (O3/UBAC) filter treating two reconstituted water samples, featuring either high bromide (105.3 μg/L) or dissolved organic nitrogen (0.73 mg N/L) concentration, respectively. Ozonation contributed to ∼20% decrease in dissolved organic carbon (DOC) concentration at a dosage of 0.7 mg of O3/mg of DOC, but no further reduction in DOC level was observed with an increased dose of 1.0 mg of O3/mg of DOC. When chlorine or preformed monochloramine was used as a disinfectant, UBAC process led to ∼40% reduction in the sum of detected DBP formation potential (FP) due to the removal of precursors at a feasible empty bed contact time of 15 min. The integrated effect of ozonation and UBAC biofiltration decreased the sum of DBP FP by ∼50% including halonitromethanes (THNMs), N-nitrosamines (NAs), and bromate, which increased in the effluent of ozonation. Chloramination produced less DBPs by weight as well as DBPs-associated additive toxic potencies than chlorination. The reduction in additive toxic potencies was generally lower than the removal efficiency of DBP FP after chlor(am)ination of treated waters by O3/UBAC, indicating that the removal of DBPs-associated additive toxic potencies should be focused to better understand on the residual risk to public health in controlling DBP precursors.

STABILITY STUDIES ON FLUCLOXACILLIN SODIUM IN RECONSTITUTED ORAL SUSPENSIONS

Objective: Stability studies on flucloxacillin sodium in reconstituted oral suspensions were carried out. The experiment sought to investigate the effects that the different types of water for reconstitution and different storage conditions have on the stability of flucloxacillin sodium in the reconstituted suspensions.Methods: Suspensions of flucloxacillin sodium were reconstituted with tap water, commercial bottled water (Voltic brand was used), commercial sachet water (Everpure brand was used) treated tap water and distilled water and stored under refrigeration (RF) (4-6 °C), at room temperature (RT) (31-33 °C) and in a bowl of water (BW) (26-27 °C). Assay of flucloxacillin sodium was by iodimetry at predetermined time intervals for 8 d.Results: The amount of flucloxacillin sodium in all the suspensions stored under the various storage conditions reduced with time and at different rates. The percentage breakdown, a parameter of stability, was calculated for each reconstituted suspension stored at the different conditions investigated and they were as follows: commercial bottled water (RT-22.40 %, RF-9.90 % and BW-15.90 %), distilled water (RT-29.14 %, RF-18.0 %, BW-28.80 %), tap water (RT-25.0%, RF-14.60 % and BW-25.10 %) and commercial sachet water (RT-25.0 %, RF-10.17 % and BW-22.50 %).Conclusion: At the end of the study, it was found that those suspensions reconstituted with the commercial bottled water were the most stable and had the smallest breakdown of flucloxacillin sodium whereas those reconstituted with distilled water were the least stable and had the largest breakdown of flucloxacillin sodium. Commercial sachet water reconstituted more stable suspensions than tap water. Also, the suspensions stored under refrigeration were the most stable followed by those stored in a bowl of water. The formulations kept at room temperature were the least stable and thus, had the largest breakdown of flucloxacillin sodium.

Bioindication of mercury, arsenic and uranium in the apple snail Pomacea canaliculata (Caenogastropoda, Ampullariidae): Bioconcentration and depuration in tissues and symbiotic corpuscles

Pomacea canaliculata is a mollusk potentially useful as a biomonitor species of freshwater quality. This work explores the ability of snail tissues and symbiotic corpuscles to bioconcentrate and depurate mercury, arsenic, and uranium. Adult snails cultured in metal-free reconstituted water were exposed for eight weeks (bioaccumulation phase) to water with Hg (2 μgL−1), As (10 μgL−1), and U (30 μgL−1) and then returned to the reconstituted water for other additional eight weeks (depuration phase). Elemental concentrations in digestive gland, kidney, symbiotic corpuscles and particulate excreta were determined by neutron activation analysis. The glandular symbiotic occupancy was measured by morphometric analysis. After exposure, the kidney showed the highest concentration of Hg, while the digestive gland accumulated mainly As and U. The subcellular distribution in symbiotic corpuscles was ∼71%, ∼48%, and ∼11% for U, Hg, and As, respectively. Tissue depuration between weeks 8 and 16 was variable amongst elements. At week 16, the tissue depuration of U was the highest (digestive gland = 92%; kidney = 80%), while it was lower for Hg (digestive gland = 51%; kidney = 53%). At week 16, arsenic showed a differential pattern of tissue depuration (digestive gland = 23%; kidney = 88%). The symbiotic detoxification of the three elements in excreta was fast between weeks 8 and 10 and it was slower after on. At the end of the depuration, each element distributed differentially in digestive gland and symbiotic corpuscles. Our findings show that symbiotic corpuscles, digestive gland and kidney P. canaliculata are sensitive places for biomonitoring of Hg, As and U.

Burrowing behavior of Chironomus yoshimatsui larvae as an indicator of freshwater quality

A new behavioral endpoint in ecotoxicity testing, burrowing behavior of Chironomus yoshimatsui larvae that survived pre-exposure to 0, 1, 5, and 10mg/L of cadmium for 96h was evaluated in a system composed of clean reconstituted water and sand for 5h, at 30min intervals. The effective time required for 50% of the introduced larvae to burrow (ET50), the proportion of the maximum burrowing rate reached during a 5h period (BR5h), and the area under the curve at 5h (AUC5h) were calculated based on the fitted relationship between burrowing rate and elapsed time. These effect parameters were chosen because they take into account either the burrowing speed of the larvae (ET50), or the proportion of the maximum burrowing rate reached during a 5h period (BR5h), or both (AUC5h). We found that higher cadmium concentrations resulted in longer ET50 and lower AUC5h values. Additionally, field water samples were collected from streams near residential, natural, agricultural, and industrial areas in Ansan City, Korea in 2014 and 2015, and were used to validate the proposed burrowing test method. The results of the burrowing tests with field collected water samples also confirmed the sensitivity of burrowing activity as an ecotoxicity endpoint, indicated by the large differences among the ET50, BR5h, and AUC5h across the sampling sites and dates with industrial sites strongly affecting burrowing behavior. This study clearly showed that the proposed burrowing test could provide information that would not be detected with the existing acute toxicity tests, within a relatively short time, and can therefore be used as a complement to existing chemical analyses and acute toxicity tests.

Acute toxicity of chlorpyrifos and carbosulfan to glochidia of the freshwater mussel Hyriopsis bialata Simpson, 1900.

The acute toxicity of carbosulfan and chlorpyrifos in formulated pesticides to glochidia (larvae) of the freshwater mussel (Hyriopsis bialata Simpson, 1900) was evaluated under static conditions in moderately hard dechlorinated tap water. Measured pesticide concentrations were 26 to 34% lower than nominal concentrations; therefore, all results are expressed in terms of measured active ingredient. Carbosulfan was relatively non-toxic to the mussel larvae with median effective concentrations (EC50) of carbosulfan at 24 and 48h greater than 0.10mg/L. The EC50s of chlorpyrifos at 24 and 48h were 0.083 and 0.078mg/L, respectively (measured concentrations). The 48-h EC50 of a combined exposure to a mixture of chlorpyrifos and carbosulfan at a constant ratio of 2.9:1 was 0.0142:0.049mg CP:CB/L. In a separate experiment, the effect of water hardness on carbosulfan, chlorpyrifos, or a combined exposure was assessed using glochidia exposed to either soft, moderately hard, or hard reconstituted water. There was no effect of water hardness on the survival of glochidia after 24- or 48-h exposure to carbosulfan. The chlorpyrifos 48-h EC50s in soft water, moderately hard water, and hard water were 0.18, 0.11, and 0.16mg/L, respectively. The data indicate that the lowest water hardness resulted in the highest survival of glochidia, whereas an increase to moderate water hardness resulted in significantly decreased survival of glochidia (F=15.5, P<0.05). The EC50s of a combined exposure at 48h in soft water, moderately hard water, and hard water were 0.124:0.044, 0.132:0.047, and 0.064:0.022mg CP:CB/L, respectively. The data indicate that the combined toxicity was lowest at low and moderate water hardness, whereas an increase to high water hardness resulted in a significantly decreased survival of glochidia. After 48h, the toxicity of the combined chlorpyrifos and carbosulfan exposure in soft and hard water was greater than that of chlorpyrifos alone.

Toxicity of cerium and thorium on Daphnia magna

Cerium (Ce) and thorium (Th) are always thought to be chemically similar and have comparable toxic properties on living organisms. In the present study, the acute and chronic toxicity of these two elements to freshwater crustacean Daphnia magna were investigated in the modified reconstituted water (6mg/L KCl, 123mg/L MgSO4·7H2O, and 294mg/L CaCl2·2H2O in Milli-Q water, pH 7.8). It seemed that Ce and Th had comparable acute toxicity on Daphnia: 24/48h EC50 for Th and Ce were 7.3/4.7μM and 16.4/10.7μM, respectively. However, Ce was present as soluble ions while all of Th was present as particulate ThO2 in the exposure medium. Considering their different chemical forms and bioavailability, the toxic mechanisms of Ce3+ and ThO2 on Daphnia would be totally different. To our knowledge, this is the first time to investigate the aquatic toxicity of thorium and cerium based on their actual chemical speciation in the exposure medium. The results also suggest that more attention should be paid on the detrimental effect of Th in the form of particulate ThO2.

Survival and Growth of Freshwater Pulmonate and Nonpulmonate Snails in 28-Day Exposures to Copper, Ammonia, and Pentachlorophenol.

We performed toxicity tests with two species of pulmonate snails (Lymnaea stagnalis and Physa gyrina) and four taxa of nonpulmonate snails in the family Hydrobiidae (Pyrgulopsis robusta, Taylorconcha serpenticola, Fluminicola sp., and Fontigens aldrichi). Snails were maintained in static-renewal or recirculating culture systems with adults removed periodically to isolate cohorts of offspring for toxicity testing. This method successfully produced offspring for bothspecies of pulmonate snails and for two hydrobiid species, P. robusta and Fluminicola sp. Toxicity tests were performed for 28days with copper, ammonia, and pentachlorophenol in hard reconstituted water with endpoints of survival and growth. Tests were started with 1-week-old L. stagnalis, 2-week-old P. gyrina, 5- to 13-week-old P. robusta and Fluminicola sp., and older juveniles and adults of several hydrobiid species. For all three chemicals, chronic toxicity values for pulmonate snails were consistently greater than those for hydrobiid snails, and hydrobiids were among the most sensitive taxa in species sensitivity distributions for all three chemicals. These results suggest that the toxicant sensitivity of nonpulmonate snails in the family Hydrobiidae would not be adequately represented by results of toxicity testing with pulmonate snails.

Contrasting effects of chloride on growth, reproduction, and toxicant sensitivity in two genetically distinct strains of Hyalella azteca.

The strain of Hyalella azteca (Saussure: Amphipoda) commonly used for aquatic toxicity testing in the United States has been shown to perform poorly in some standardized reconstituted waters frequently used for other test species. In 10-d and 42-d experiments, the growth and reproduction of the US laboratory strain of H. azteca was shown to vary strongly with chloride concentration in the test water, with declining performance observed below 15 mg/L to 20 mg/L. In contrast to the chloride-dependent performance of the US laboratory strain of H. azteca, growth of a genetically distinct strain of H. azteca obtained from an Environment Canada laboratory in Burlington, Ontario, Canada, was not influenced by chloride concentration. In acute toxicity tests with the US laboratory strain of H. azteca, the acute toxicity of sodium nitrate increased with decreasing chloride in a pattern similar not only to that observed for control growth, but also to previous acute toxicity testing with sodium sulfate. Subsequent testing with the Burlington strain showed no significant relationship between chloride concentration and the acute toxicity of sodium nitrate or sodium sulfate. These findings suggest that the chloride-dependent toxicity shown for the US laboratory strain may be an unusual feature of that strain and perhaps not broadly representative of aquatic organisms as a whole.

High-speed AFM images of thermal motion provide stiffness map of interfacial membrane protein moieties.

The flexibilities of extracellular loops determine ligand binding and activation of membrane receptors. Arising from fluctuations in inter- and intraproteinaceous interactions, flexibility manifests in thermal motion. Here we demonstrate that quantitative flexibility values can be extracted from directly imaging the thermal motion of membrane protein moieties using high-speed atomic force microscopy (HS-AFM). Stiffness maps of the main periplasmic loops of single reconstituted water channels (AqpZ, GlpF) revealed the spatial and temporal organization of loop-stabilizing intraproteinaceous H-bonds and salt bridges.

Transcriptomic, biochemical and individual markers in transplanted Daphnia magna to characterize impacts in the field

Daphnia magna individuals were transplanted across 12 sites from three Spanish river basins (Llobregat, Ebro, Jucar) showing different sources of pollution. Gene transcription, feeding and biochemical responses in the field were assessed and compared with those obtained in re-constituted water treatments spiked with organic eluates obtained from water samples collected at the same locations and sampling periods. Up to 166 trace contaminants were detected in water and classified by their mode of action into 45 groups that included metals, pharmaceuticals, pesticides, illicit drugs, and other industrial compounds. Physicochemical water parameters differentiated the three river basins with Llobregat having the highest levels of conductivity, metals and pharmaceuticals, followed by Ebro, whereas the Jucar river had the greatest levels of illicit drugs. D. magna grazing rates and cholinesterase activity responded similarly than the diversity of riparian benthic communities. Transcription patterns of 13 different genes encoding for general stress, metabolism and energy processes, molting and xenobiotic transporters corroborate phenotypic responses differentiated sites within and across river basins. Principal Component Analysis and Partial Least Square Projections to Latent Structures regression analyses indicated that measured in situ responses of most genes and biomarkers and that of benthic macroinvertebrate diversity indexes were affected by distinct environmental factors. Conductivity, suspended solids and fungicides were negatively related with the diversity of macroinvertebrates cholinesterase, and feeding responses. Gene transcripts of heat shock protein and metallothionein were positively related with 11 classes of organic contaminants and 6 metals. Gene transcripts related with signaling paths of molting and reproduction, sugar, protein and xenobiotic metabolism responded similarly in field and lab exposures and were related with high residue concentrations of analgesics, diuretics, psychiatric drugs, β blockers, illicit drugs, trizoles, bisphenol A, caffeine and pesticides. These results indicate that application of omic technologies in the field is a promising subject in water management.