10-d Experiment Research Articles

Single-atom Mo–Co catalyst with low biotoxicity for sustainable degradation of high-ionization-potential organic pollutants

Single-atom catalysts (SACs) are a promising area in environmental catalysis. We report on a bimetallic Co-Mo SAC that shows excellent performance in activating peroxymonosulfate (PMS) for sustainable degradation of organic pollutants with high ionization potential (IP > 8.5 eV). Density Functional Theory (DFT) calculations and experimental tests demonstrate that the Mo sites in Mo-Co SACs play a critical role in conducting electrons from organic pollutants to Co sites, leading to a 19.4-fold increase in the degradation rate of phenol compared to the CoCl2-PMS group. The bimetallic SACs exhibit excellent catalytic performance even under extreme conditions and show long-term activation in 10-d experiments, efficiently degrading 600 mg/L of phenol. Moreover, the catalyst has negligible toxicity toward MDA-MB-231, Hela, and MCF-7 cells, making it an environmentally friendly option for sustainable water treatment. Our findings have important implications for the design of efficient SACs for environmental remediation and other applications in biology and medicine.

Hyporheic Interactions Increase Zinc Exposure and Effects on Hyalella azteca in Sediments under Flow-Through Conditions.

Groundwater-surface water interactions in the hyporheic transition zone can influence contaminant exposure to benthic macroinvertebrates. In streams, hyporheic flows are subject to varying redox conditions, which influence biogeochemical cycling and metal speciation. Despite these relationships, little is known about how these interactions influence the ecological risk of contaminants. The present study investigated the effects of hyporheic flows and zinc (Zn)-contaminated sediments on the amphipod Hyalella azteca. Hyporheic flows were manipulated in laboratory streams during 10-d experiments. Zinc toxicity was evaluated in freshly spiked and aged sediments. Hyporheic flows altered sediment and porewater geochemistry, oxidizing the sediments and causing changes to redox-sensitive endpoints. Amphipod survival was lowest in the Zn sediment exposures with hyporheic flows. In freshly spiked sediments, porewater Zn drove mortality, whereas in aged sediments simultaneously extracted metals (SEM) in excess of acid volatile sulfides (AVS) normalized by the fraction of organic carbon (fOC) [(SEM-AVS)/fOC] influenced amphipod responses. The results highlight the important role of hyporheic flows in determining Zn bioavailability to benthic organisms, information that can be important in ecological risk assessments. Environ Toxicol Chem 2019;38:2447-2458. © 2019 SETAC.

Response of bloom-forming cyanobacterium Microcystis aeruginosa to 17β-estradiol at different nitrogen levels

Co-existence of cyanobacterial harmful algal blooms (CyanoHABs) and steroid estrogens (SEs) has been an increasing concern in eutrophic waters. The cellular responses and biodegradation of 17β-estradiol (E2) in cyanobacterium Microcystis aeruginosa were investigated at different nitrogen levels. During the 10-d experiment, the growth of M. aeruginosa was stimulated by 10–100 μg L−1 of E2 at the lowest nitrogen level of 0.5 mg L−1, whereas the presence of E2 inhibited the cyanobacterial growth at 5 mg L−1 of nitrogen. With nitrogen concentration increased to 50 mg L−1, the impact of E2 on levels of growth rate and chlorophyll a (Chla) alleviated. Exposure to E2 also promoted the superoxide dismutase activity of M. aeruginosa, coupled with cellular oxidative damage as indicated by the increasing malondialdehyde content. A sufficient nitrogen supply mitigated the oxidative stress of E2 through enhancing the synthesis of detoxification-related enzymes. Simultaneously, the secretion of tryptophan-like substances in loosely- and tightly-bound extracellular polymeric substances was triggered for adapting to an E2 addition in the short term. Moreover, significant biodegradation of E2 was observed, and the process followed a first-order kinetic reaction. The obtained half-lives decreased with nitrogen levels and ranged from 2.47 to 2.81 and 3.39–5.04 d, respectively, at 10 and 100 μg L−1 of E2. These results provide a better understanding of the potential effects of SEs on CyanoHABs formation, as well as the important role of CyanoHABs on SEs removal in aquatic ecosystems, which should be fully considered in the control of combined pollution.

Effect of Temperature on the Release of Proterometra macrostoma (Trematoda: Digenea) Cercariae from Their Snail Intermediate Host, Pleurocera semicarinata (Gastropoda: Pleuroceridae) at North Elkhorn Creek, Kentucky

The effect of temperature on cercarial release has been well documented for several digenean species; however, there have been no prior studies assessing shedding of cercariae from snails infected with the azygiid, Proterometra macrostoma. Snails, Pleurocera semicarinata, were collected at the Lemon's Mill site on North Elkhorn Creek in Scott County, Kentucky during June and July 2016. Snails shedding cercariae (n = 453) were assigned to temperature treatments (10, 13, 15, 18, 20, 25, and 30°C) that were within the range of previously reported seasonal water temperatures at North Elkhorn Creek. Snails were acclimated to experimental temperatures for 3 d. Cercarial counts were then made at 0900 h daily over the next 7 d, and the average 7-d cercarial release was calculated for each snail. The minimum emergence threshold temperature for Pr. macrostoma cercarial release was determined to be approximately 13°C, whereas the minimum development threshold temperature was between 10 and 12°C. Notably, cercarial release increased with temperature up to 25°C, but declined at 30°C. Q10 values calculated from 10°C intervals were greatest at the lowest (13–23°C) temperature interval (Q10 = 16.1), and declined at the higher (15–25 and 20–30°C) intervals (Q10 = 4.3 and Q10 = 1.8, respectively). Snail survivorship within combined replicates ranged from 87.1 to 100% over the 10-d experiment, with the lowest survivorship observed at 30°C. These results are discussed with regard to climate change and global warming.

Effects of sweetener neotame on diet preference, performance and hematological and biochemical parameters of weaned piglets

Three experiments were conducted to evaluate the effects of a sweetener, neotame (N-[N-(3,3-dimethylbutyl)-l-α-aspartyl]-l-phenylalanine 1-methyl ester) on diet preference, performance and hematological and biochemical parameters of weaned piglets. In experiment 1, 48 weaned piglets (Duroc×Landrace×Large White), with an initial body weight (BW) of 9.05±0.04kg, were used in a diet preference study. Pigs were assigned to 8 pens with 6 pigs per pen. Each pen was equipped with two feeders, containing a maize-soybean meal based diet or a similar diet supplemented with 30mg/kg neotame. The experiment lasted for 15 days, including a 5-d adaptation period and a 10-d experiment period. The diet supplemented with 30mg/kg neotame was preferred (P<0.05) by the pigs during d 7, d 10 and the entire experimental period (d 1–10). In experiment 2, 216 weaned piglets, with an initial BW of 7.35±0.06kg, blocked by gender and BW, were allocated to 1 of 6 treatments with 6 pens per treatment and 6 pigs per pen. Weaned piglets were fed the basal diet or similar diets supplemented with 10, 20, 30, 40 or 50mg/kg neotame. The experiment lasted for 35 days. Average daily feed intake (ADFI) was improved linearly (P<0.05) with increasing dietary neotame level during phase I (d 1–22) and the entire experimental period (d 1–35). A quadratic (P<0.05) effect of neotame was observed on average daily gain (ADG) and ADFI during phase I (d 1–22), phase II (d 23–35) and the entire experimental period (d 1–35). The optimal concentrations of dietary neotame to maximize ADG and ADFI during entire experimental period using a fitted quadratic plot model were 21.7 and 20.7mg/kg, respectively. Experiment 3 was conducted with 108 weaned piglets averaging an initial BW of 7.34±0.08kg to evaluate the effects of neotame on hematological and biochemical parameters of weaned piglets. Pigs were divided into 3 treatments with 6 pens per treatment and 6 pigs per pen, and fed the basal diet or similar diets supplemented with 50 or 500mg/kg neotame. There was no difference (P>0.05) in blood parameters, organ index and morphology among the three treatments. In conclusion, the optimal concentrations of dietary neotame for maximum ADFI and ADG was ranged from 18.0 to 20.4mg/kg during phase I (d 1–22), 22.0 to 22.9mg/kg during phase II (d 23–35) and 20.7 to 21.7mg/kg during entire experimental period (d 1–35), and no adverse effects on indicators of health were observed in pigs offered diets with neotame levels up to 500mg/kg.

Effects of benthic organism Tubifex tubifex on hexachlorocyclohexane isomers transfer and distribution into freshwater sediment

In this study, bioaccumulation and elimination of HCHs in tubifex, and the distribution of HCHs in overlying water and sediment, were studied during a 10-d experiment. A sensitive method was developed for the determination of HCHs in samples based on gas chromatograph (GC) equipped with a nickel-63 electron capture detector (μECD). The limit of detection (LOD) was 0.35µg/kg for α-HCH and 0.82µg/kg for β-HCH. Tubifex accumulated HCHs rapidly, and the curves were approximately M-type. The highest level was reached on the 7th day, with 0.34mg/kgwwt for α-HCH and 0.87mg/kgwwt for β-HCH in worms. The AFs of β-HCH in tubifex were higher than those of α-HCH. Moreover, the existence of tubifex significantly reduced β-HCH fluxes from the overlying water to sediment by uptake or degradation and decreased the concentrations of β-HCH in the sediment, but it had little influence on α-HCH fluxes. Moreover, enantioselectivity of α-HCH enantiomers was not observed in tubifex, whether in the bioaccumulation or elimination experiments. At the end of the elimination experiment, approximately 80% and 70% of α-HCH and β-HCH were eliminated, and the depuration half-lives were 4.43 and 5.39 days, respectively.

Inhibition of UVB-induced skin phototoxicity by a grape seed extract as modulator of nitrosative stress, ERK/NF-kB signaling pathway and apoptosis, in SKH-1 mice

Molecular mechanisms concerning the modulation of nitrosative stress, signal transduction and proliferation/apoptosis by a grape seed extract, Burgund Mare variety (BM), in SKH-1 mice exposed to UVB, were investigated. The animals were irradiated with single and multiple doses of UVB in 10 consecutive days. In each experiment were used five groups of animals: control, vehicle, UVB irradiated, vehicle+UVB, BM+UVB. The extract was applied topically, 30 min before each UVB exposure, in a dose of 4 mg total polyphenols/cm(2). BM remarkably inhibited UVB-induced activation of inducible nitric oxide synthase (iNOS) and therefore generation of nitric oxide (NO) and nitrotyrosine, in a UVB single dose regimen. BM also suppressed NF-kB activation by UVB but did not affect the activity of total ERK 1/2. In multiple UVB irradiations, BM increased NO formation and total ERK 1/2 activity and reduced iNOS activity and nitrotyrosine levels, inhibited cell proliferation, diminished p53 and caspase-3 immunoreactivities and increased the percentage of Bcl-2 positive cells. We concluded that BM modulates the apoptotic response of SKH-1 mice skin in UVB irradiation by the inhibition of p53, caspase-3, Bax/Bcl-2 and proliferating cell nuclear antigen expressions, as well as by reducing the activation of iNOS and NF-kB.

Fine-scale differences in diel activity among nocturnal freshwater planarias (Platyhelminthes: Tricladida)

BackgroundAlthough most freshwater planarias are well known photonegative organisms, their diel rhythms have never been quantified. Differences in daily activity rhythms may be particularly important for temperate-climate, freshwater planarias, which tend to overlap considerably in spatial distribution and trophic requirements.MethodsActivity of stress-free, individually tested young adults of three common planarian species was recorded at 3-h intervals in a 10-d experiment under natural sunlight and photoperiod during autumnal equinox (D:L ~12:12). Individual activity status was averaged over the 10-d experiment, each tested individual thus serving as a true replicate. Twelve individuals per species were tested. Food was provided every 36 h, resulting in alternating day- and nighttime feeding events. Activity during the first post-feeding h was recorded and analyzed separately. Statistical procedures included ANOVAs, correlations, and second-order analyses of angles.ResultsDugesia (= Girardia) tigrina Girard 1850 exhibited clear nocturnal behavior, Dugesia (= Schmidtea) polychroa Schmidt 1861 was predominantly but not exclusively nocturnal, and Polycelis tenuis Ijima 1884 was relatively more active from midnight through noon. Species-specific activity peaks were statistically similar, with peaks at dawn for P. tenuis and just before midnight for the two dugesiids; however, D. tigrina was comparatively more active in the early night hours, while D. polychroa was more active than D. tigrina during daytime. D. tigrina also responded less readily to daytime food addition. P. tenuis remained poorly active and unresponsive throughout the experiment. Individual variability in diel behavior was highest for D. polychroa and lowest for D. tigrina. P. tenuis's general low degree of activity and late activity peak in the experiment may be related to a strong reliance on external stimuli.ConclusionsThe tested species are mainly nocturnal, consistent with their photonegative characteristics. The fine-scale differences in diel behavior among these three triclad species may not be sufficient to allow coexistence in the wild, with the nonnative D. tigrina eventually displacing D. polychroa and P. tenuis in many European waters. The link between planarian diel rhythms and ecological characteristics are worth of further, detailed investigation.

Phosphorus equivalency value of an Escherichia coli phytase in the diets of White Pekin ducks

Male White Pekin ducks at 7 d posthatch were used in a 10-d experiment to determine the equivalency value of an Escherichia coli phytase (Phyzyme XP) in corn-soybean meal-based mash diets. Two hundred fifty-six ducks were grouped by weight into 8 blocks of 8 cages with 4 ducks per cage. The 8 diets consisted of a P-adequate positive control corn-soybean meal formulated to contain CP, Ca, total P, and nonphytate P at 220, 8, 6.6, and 4 g/kg, respectively; a low-P negative control (NC) corn-soybean meal basal diet formulated to contain CP, Ca, total P, and nonphytate P at 220, 6.5, 3.9, and 1.3 g/kg, respectively; NC diet plus 0.5, 1.0, or 1.5 g of inorganic P from monosodium phosphate/kg; and NC diet plus E. coli phytase at 500, 1,000, or 1,500 units/kg. Ducks were provided ad libitum access to water and experimental diets. Feeding the low-P NC diet to ducks reduced (P<0.01) BW gain, feed intake, G:F, tibia ash, ileal digestibility, and utilization of P. Supplementation of the NC diet with inorganic P or phytase linearly improved (P<0.01) final weight, BW gain, feed intake, G:F, tibia ash, and ileal P digestibility. There were linear increases (P<0.01) in the utilization of P from 33.8 to 42% or from 33.8 to 46.6% as dietary added inorganic P or phytase increased from 0 to 1.5 g/kg or 0 to 1,500 units/kg, respectively. Linear regression equations for the tibia ash as the dependent variable and supplemental intake of inorganic P and phytase or supplemental level of inorganic P and phytase as independent variables were used to generate P equivalency values of phytase. The mean P equivalency values of phytase from linear regression equations derived from ducks fed a low-P NC diet supplemented with graded levels of inorganic P or phytase from d 7 to 17 posthatch for 500, 1,000, and 1,500 phytase units/kg of diet were 0.453, 0.847, and 1.242 g/kg of diet, respectively. The results of this study showed that this phytase was efficacious in hydrolyzing phytate P for bone mineralization and growth of ducks.

Toxicity and bioaccumulation of 2, 4, 6‐trinitrotoluene in fathead minnow (Pimephales promelas)

Few studies have determined the toxicity and bioaccumulation potential of explosive compounds in freshwater fish. In the present study, fathead minnow (Pimephales promelas) were exposed to a range of 2,4,6-trinitrotoluene (TNT) concentrations (0.44-44 micromol/L [0.1-10 mg/L] and 4.4-22.0 micromol/L [1.0-5.0 mg/L] in 4- and 10-d experiments, respectively). Median lethal concentrations of 11.93 micromol/L (2.7 mg/L; 95% confidence limit [CL], 10.29-13.83 micromol/L) and 9.68 micromol/L (2.20 mg/L; 95% CL, 9.17-10.22 micromol/L) were calculated in the 4- and 10-d experiments, respectively, and median lethal body residue of 101.0 micromol/kg (95% CL, 86.0-118.7 micromol/kg) was calculated in 4-d experiments. To study bioaccumulation, fish were exposed to 4.4 micromol/L (1 mg/L) of TNT for 12 h. Rapid bioaccumulation of TNT occurred within the first 10 min of exposure (ku = 30.4 L/kg/ h). Elimination of sigmaTNT (molar sum of TNT and degradation products 2- and 4-aminodinitrotoluenes) was fast, with an elimination rate (ke) of 2.24/h and a short half-life (0.31 h). The bioconcentration factors determined using 6-h mean tissue and water concentrations of sigmaTNT were 8.40 and 4.68 L/kg for the uptake experiment and the uptake portion of the elimination experiments, respectively. To determine the target organ for TNT in fish, juvenile fathead minnow were exposed to 2.2 micromol/L (0.5 mg/L) of [14C]TNT for 10 d. Radiolabeled compounds primarily bioaccumulated in the visceral tissues and spleen in comparison to gill, brain, muscle, and remainder tissue groups. The present study demonstrates the low bioaccumulation potential and rapid uptake of TNT in the fathead minnow.

Leucine-Supplemented Meal Feeding for Ten Days Beneficially Affects Postprandial Muscle Protein Synthesis in Old Rats

Acute leucine supplementation of the diet has been shown to blunt defects in postprandial muscle protein metabolism in old rats. This study was undertaken to determine whether the effect of leucine persists in a 10-d experiment. For this purpose, adult (9 mo) and old (21 mo) rats were fed a semiliquid 18.2 g/100 g protein standard diet during the 8-h dark period for 1 mo. Then, each group was given either a leucine-supplemented meal or an alanine-supplemented meal (as the control meal) for 1 h and the standard diet the rest of the feeding period. On d 10, rats were fed either no food (postabsorptive group) or the supplemented meal for 1 h. Muscle protein synthesis was assessed in vivo 90-120 min after meal distribution using the flooding dose method (1-(13)C phenylalanine). Leucinemia was similar in rats of both ages in the postabsorptive state. Postprandial plasma leucine concentrations were one- to twofold greater after the leucine meal than after the control meal. In the postabsorptive state, leucine supplementation did not modify the muscle protein synthesis rate in old rats but enhanced it to the postprandial rate in adult rats. As expected, muscle protein synthesis was stimulated by the control meal in adult rats but not in old rats. The leucine meal restored this stimulation in old rats but did not further stimulate muscle protein synthesis in adult rats. In conclusion, the beneficial effect of leucine supplementation on postprandial muscle protein anabolism persists for at least 10 d. The long-term utilization of leucine-rich diets may therefore limit muscle protein wasting during aging.

Toxicity of sediment-associated pyrene and phenanthrene toLimnodrilus hoffmeisteri(oligochaeta: Tubificidae)

Acute and sublethal toxicities of sediment-spiked pyrene and phenanthrene to Limnodrilus hoffmeisteri Cleparede were investigated. Phenanthrene was acutely toxic at high sediment concentrations (10-d median lethal concentration of 297.5 {micro}g g{sup {minus}1}; 252.2--348.3, 95% confidence interval [Cl]). Pyrene was not acutely toxic, even at concentrations as high as 841 {micro}g g{sup {minus}1}. A significant impact of pyrene and phenanthrene on the feeding activity of L. hoffmeisteri was demonstrated through daily collection of egested fecal material during 5- and 10-d experiments. A short (5-d) exposure detected toxic effects more efficiently than a 10-d exposure, yielding IC25 values (estimated concentration causing a 25% reduction of measured endpoint in relation to the control[s]) of 58.9 {micro}g g{sup {minus}1} (32.1--89.4, 95% CI) for pyrene and 28.4 {micro}g g{sup {minus}1} (10.0--41.3, 95% CI) for phenanthrene. Effects on burrowing behavior and reproduction were assessed in a 28-d sediment exposure. Low burrowing avoidance (< 25%) was detected in high phenanthrene concentrations (143--612 {micro}g g{sup {minus}1}) but was not detected with pyrene. Offspring production was significantly reduced in dosed sediments yielding IC25 values of 59.1 {micro}g g{sup {minus}1} (38.3--112.5, 95% CI) for pyrene and 40.5 {micro}g g{sup {minus}1} (12.1--165.5, 955 CI) for phenanthrene. Decreases in egestion rates inmore » the presence of nonpolar contaminants should be quantified when investigating the effects of bioturbation by deposit feeders on the flux of contaminants from sediment into the water column.« less

Interactive Effects of Dietary Copper, Water Copper, and Eimeria spp. Infection on Growth, Water Intake, and Plasma and Liver Copper Concentrations of Poults

The effects of dietary Cu, water Cu, and coccidial infection on poult growth performance and selected tissue mineral concentrations were investigated in a 10-d experiment using 200 5-d-old Nicholas toms (five replicates of 5 poults each; initial weight = 85 g). Uninfected and coccidiosis-infected (Eimeria meleagrimitis, Eimeria dispersa, Eimeria adenoeides, and Eimeria gallopavonis; cocci) poults were assigned to two levels of dietary Cu [Basal (B) and B + 204 mg Cu/kg diet on Days 1 to 10] and two levels of water Cu (0 and 103 mg Cu/kg water on Days 6 to 10). Dietary Cu and water Cu (main effects) did not affect (P > .10) gain, feed intake, gain:feed, water intake, hemoglobin, hematocrit, or liver Fe and Zn concentrations. Dietary Cu and water Cu increased (P < .03) liver and plasma Cu concentrations. The combination of dietary Cu and water Cu increased plasma Cu more than the sum of the Cu additions (dietary Cu by water Cu, P < .08). Coccidial infection reduced (P < .07) gain, feed intake, gain:feed, water intake, and hemoglobin, and increased (P < .02) liver Zn. Water Cu reduced water intake in uninfected poults but increased water intake in coccidiosis-infected poults (water Cu by cocci, P < .07). Water Cu increased hemoglobin in uninfected poults but decreased hemoglobin in coccidiosis-infected poults (water Cu by cocci, P < .07). Water Cu increased plasma Cu and liver Cu more in coccidiosis-infected poults than in uninfected poults (water Cu by cocci, P < .02). Simultaneous supplementation of feed and water with Cu increases plasma and liver Cu concentrations in coccidiosis-infected poults.

Fecundity Characteristics of the Greenbug Biotypes C and E Cultured on Different Host Plants

Greenbug, Schizaphis graminum (Rondani), clones were collected in fields from eight localities in the central United States. Two clones collected from sorghum, Sorghum bicolor (L.) Moench, and one clone obtained from the Agronomy Greenhouse, North Dakota State University, Fargo, N. Dak. (initially isolated on barley in 1968) were identified as biotype C. Six other clones collected from sorghum fields were identified as biotype E. All clones were cultured in the laboratory on barley, Hordeum vulgare L.; oats, Avena sativa L.; ‘Piper’ sudangrass, Sorghum sudanensis Bailey; and Kentucky bluegrass, Poa pratensis L., as standard diets. All clones were tested for fecundity during 10-d experiments in two chambers with automatically controlled 14:10 (L:D) photoperiod at 24 ± 1°C and 25% relative humidity. Fecundity of biotypes C and E was determined on the same host plants and on corn, Zea mays L., susceptible sorghum, biotype-C-resistant ‘IS-809’ sorghum, and biotype-C-resistant ‘Amigo’ wheat. Clones of the same biotype from different localities did not show differences in fecundity on the same host plants after being previously cultured on the same host plants. Biotype C showed greater fecundity on Kentucky bluegrass and on ‘Piper’ sudangrass after culturing on barley. Biotype E had greater fecundity on oat and ‘Piper’ sudangrass after culturing on barley. On corn, greenbugs did not survive longer than a week. All greenbugs grew slowly on ‘Amigo’ wheat and ‘IS-809’ sorghum. Greenbugs had higher fecundity on ‘IS-809’ sorghum than on ‘Amigo’ wheat.