Role of titanium dioxide nanoparticles in the elevated uptake and retention of cadmium and zinc in Daphnia magna

Titanium dioxide nanoparticles (nano-TiO(2)) are now widely applied in consumer products, and the dispersion of nano-TiO(2) may adsorb metals and modify their behavior and bioavailability in the aquatic environment. In the present study, the aqueous uptake, dietary assimilation efficiency (AE), and efflux rate constant (k(e)) of two toxic metals (cadmium-Cd, and zinc-Zn) adsorbed on nano-TiO(2) in a freshwater zooplankton Daphnia magna were quantified. The biokinetics was then compared to daphnids that were exposed only to dissolved metals as controls. The aqueous uptake of Cd and Zn involved an initial rapid uptake and then an apparent saturation, and the uptake of metals was accompanied by an ingestion of nano-TiO(2). The AEs of Cd and Zn adsorbed on nano-TiO(2) were 24.6 ± 2.4-44.5 ± 3.7% and 30.4 ± 3.4-51.8 ± 5.0%, respectively, and decreased with increasing concentrations of nano-TiO(2). Furthermore, the difference between the AEs of Cd and Zn indicated that the desorption of Cd and Zn from nano-TiO(2) may have occurred within the gut of daphnids. With the use of algae as carrier, the AEs of Cd and Zn adsorbed on nano-TiO(2) were significantly higher than those of Cd and Zn directly from nano-TiO(2). The efflux rate constants of Cd and Zn adsorbed on nano-TiO(2) in the zooplankton were significantly lower than those of Cd and Zn not adsorbed on nano-TiO(2). Our study shows that the uptake and retention of toxic metals is enhanced when they are adsorbed on nano-TiO(2), and suggests more attention be paid to the potential influences of nano-TiO(2) on the bioavailability and toxicity of other contaminants.     

Toxicogenomic responses of nanotoxicity in Daphnia magna exposed to silver nitrate and coated silver nanoparticles

Applications for silver nanomaterials in consumer products are rapidly expanding, creating an urgent need for toxicological examination of the exposure potential and ecological effects of silver nanoparticles (AgNPs). The integration of genomic techniques into environmental toxicology has presented new avenues to develop exposure biomarkers and investigate the mode of toxicity of novel chemicals. In the present study we used a 15k oligonucleotide microarray for Daphnia magna, a freshwater crustacean and common indicator species for toxicity, to differentiate between particle specific and ionic silver toxicity and to develop exposure biomarkers for citrate-coated and PVP-coated AgNPs. Gene expression profiles revealed that AgNO(3) and AgNPs have distinct expression profiles suggesting different modes of toxicity. Major biological processes disrupted by the AgNPs include protein metabolism and signal transduction. In contrast, AgNO(3) caused a downregulation of developmental processes, particularly in sensory development. Metal responsive and DNA damage repair genes were induced by the PVP AgNPs, but not the other treatments. In addition, two specific biomarkers were developed for the environmental detection of PVP AgNPs; although further verification under different environmental conditions is needed.     

DNA exposure to buckminsterfullerene (C60): toward DNA stability, reactivity, and replication

Buckminsterfullerene (C(60)) has received great research interest due to its extraordinary properties and increasing applications in manufacturing industry and biomedical technology. We recently reported C(60) could enter bacterial cells and bind to DNA molecules. This study was to further determine how the DNA-C(60) binding affected the thermal stability and enzymatic digestion of DNA molecules, and DNA mutations. Nano-C(60) aggregates and water-soluble fullerenols were synthesized and their impact on DNA biochemical and microbial activity was investigated. Our results revealed that water-soluble fullerenols could bind to lambda DNA and improve DNA stability remarkably against thermal degradation at 70-85 °C in a dose-dependent manner. DNase I and HindIII restriction endonuclease activities were inhibited after interacting with fullerenols at a high dose. Experimental results also showed the different influence of fullerenol and nano-C(60) on their antibacterial mechanisms, where fullerenols contributed considerable impact on cell damage and mutation rate. This preliminary study indicated that the application of fullerenols results in significant changes in the physical structures and biochemical functions of DNA molecules.     

Temporal changes in Aqu/C60 physical-chemical, deposition, and transport characteristics in aqueous systems

Little is known about how temporal changes in the physical-chemical properties of C?? aggregates formed in aqueous systems (termed aqu/C??) can impact transport pathways contributing to ecological exposures. In this study three aqu/C?? suspensions of short-term (100 days), intermediate-term (300 days), and long-term (1000 days) water exposure were first characterized for particle size distribution, water/toluene phase distribution, and surface chemistry. Then, aqu/C?? deposition to a model silica surface and transport in porous media were studied by quartz crystal microbalance (QCM) and saturated sand columns. As suspension time increased, aqu/C?? particle size shifted to a larger size range as determined by asymmetric flow field-flow fractionation (AF4) and the aqu/C?? distribution to toluene was reduced, likely due to surface polarization as revealed by nuclear magnetic resonance (NMR) and UV-visible spectroscopy of the aqu/C?? suspensions. Additionally, the deposition to silica surfaces in both QCM and column studies decreased with increased water exposure time. Although a small increase in aqu/C?? aggregate size with time may partially explain the greater transport of the long-term aqu/C?? because of the decreased collector efficiency for larger submicrometer particles, the polarization of the aqu/C?? (thus a more hydrophilic surface) revealed by the toluene/water phase distribution and confirmed by NMR, is considered the determining factor.     

Weight loss and mortality of three life stages of Tribolium castaneum (Herbst) when exposed to four modified atmospheres

Larvae, pupae, and adults of Tribolium castaneum (Herbst) were exposed to atmospheres containing high nitrogen (N₂) or carbon dioxide (CO₂) concentrations at about 50% r.h. and 27°C for periods up to 72 hr. Overall, 99% N₂ caused greater mortality in adults than did 58% CO₂ while 58% CO₂ was more effective against pupae. The difference in mortality to larvae exposed to the two atmospheres was not significant, though 99% N₂ produced greater mortalities by 48 hr. Also, the differences in mortality for larvae and pupae exposed to atmospheres of 58% CO₂ and 97% CO₂ were not significant though 97% CO₂ caused a significantly greater mortality in adults than did 58% CO₂. Both mortality and weight loss of all life stages tested were small when the insects were exposed to an atmosphere of 97% N₂, but weight loss was generally small and mortality was large for those insects exposed to 97% CO₂.When overall weight loss was compared for those insects exposed to 58% CO₂ and 99% N₂, larval weight loss was greater for those exposed to the CO₂ atmosphere; pupal weight loss was not significantly different between the two atmospheres; adult weight loss was greater for those exposed to the N₂ atmosphere.     

Microbiological and physicochemical changes in minced meats under carbon dioxide, nitrogen or air at 3°C

Microbiological changes were studied in minced beef and minced dark, firm, dry (DFD) pork stored under different atmospheres (100% in carbon dioxide, nitrogen or air) at 3°C. The storage life (time for 100-fold increase in TVC) of samples flushed with carbon dioxide was increased by c . 3–4 days. Pseudomonads were the dominant organisms in samples stored in air, and lactic acid bacteria and Brochothrix thermosphacta in those stored under carbon dioxide. There was an alkaline drift in all samples, but at different rates (air > nitrogen > carbon dioxide). The rate of glucose assimilation in normal and DFD beef was slower in the samples stored under carbon dioxide than those under nitrogen or air. Lactate, gluconate, acetic acid, ethanol and diacetyl occurred in normal and DFD beef regardless of the storage atmospheres.     

Interaction of fullerene (C60) nanoparticles with humic acid and alginate coated silica surfaces: measurements, mechanisms, and environmental implications

The deposition kinetics of fullerene (C60) nanoparticles onto bare silica surfaces and surfaces precoated with humic acid and alginate are investigated over a range of monovalent (NaCI) and divalent (CaCl2) salt concentrations using a quartz crystal microbalance. Because simultaneous aggregation of the fullerene nanoparticles occurs, especially at higher electrolyte concentrations, we normalize the observed deposition rates by the corresponding favorable (transport-limited) deposition rates to obtain the attachment efficiencies, alpha. The deposition kinetics of fullerene nanoparticles onto bare silica surfaces are shown to be controlled by electrostatic interactions and van der Waals attraction, consistent with the classical particle deposition behavior where both favorable and unfavorable deposition regimes are observed. The presence of dissolved humic acid and alginate in solution leads to significantly slower deposition kinetics due to steric repulsion. Precoating the silica surfaces with humic acid and alginate exerts similar steric stabilization in the presence of NaCl. In the presence of CaCl2, the deposition kinetics of fullerene nanoparticles onto both humic acid- and alginate-coated surfaces are relatively high, even at relatively low (0.3 mM) calcium concentration. This behavior is attributed to the macromolecules undergoing complex formation with calcium ions, which reduces the charge and steric influences of the adsorbed macromolecular layers.     

Sensory, chemical and bacteriological changes in vacuum-packed pressurised squid mantle (Todaropsis eblanae) stored at 4 degrees C

Sensory, chemical and bacteriological changes were studied in vacuum-packed squid mantles (Todaropsis eblanae) that were pressurised at 150, 200, 300 and 400 megapascal (MPa) for 15 min at ambient temperature and stored at 4 degrees C. Sensory analysis showed that the higher the pressurisation the longer the shelf-life. Thus, the lot pressurised at 400 MPa was rejected after 28 days' storage compared with 7 days for the untreated lot. The chemical results generally corresponded with the sensory ones. Furthermore, ammonia (NH3) and trimethylamine (TMA) were produced in the pressurised lots after a pressure dependent delay. Urea decreased to low levels in all lots with the exception of the 400 MPa lot. Onset of production of agmatine, the dominant amine in this species, and other biogenic amines was delayed by increasing pressure, but still, high concentrations of these amines were detected in pressurised lots of acceptable sensory quality. Microbial counts conducted after 1 day of storage showed that the bacterial load was reduced by all pressures, reaching levels below the detection limit in the lots treated with 200-400 MPa. However, growth was resumed in all lots after a pressure dependent delay. Luminous bacteria predominated initially in the lots pressurised at 300 and 400 MPa, but were outnumbered by Enterobacteriaceae and lactic acid bacteria at the time of sensory rejection of these lots. All colonies isolated prior to pressurisation were identified as Photobacterium phosphoreum. This bacterium also resumed growth faster than other members of the endogenous microflora after pressurisation. All luminous colonies were identified as P. phosphoreum. Lactic acid bacteria isolated at the final sampling point of the lot pressurised at 400 MPa were identified as Carnobacterium piscicola and Carnobacterium divergens, while Serratia liquefaciens and Proteus vulgaris make up Enterobacteriaceae.     

Using nitrogen and carbon dioxide molecules to probe arsenic(V) bioaccessibility in soils

Highly specialized personnel and high cost are typically required for in vivo risk assessment of arsenic (As) exposure to humans in As-contaminated soils. Arsenic bioaccessibility in soils, as determined with the aid of in vitro tests, is quite variable, and its magnitude depends upon unidentified soil properties. Use of soil chemical properties is a common practice for construction of As(V) sorption and bioaccessibility models with relative success. We propose a novel As(V) bioaccessibility model, which was tested on 17 soils. The model includes only two parameters characterizing surface properties of soils that are readily determined from N2- and CO2-based specific surface areas (SSAs), and total organic carbon (OC) content. We found that N2 and CO2 molecules act as As(V) "surrogates", probing easily accessible and relatively difficult to access soil porosity, respectively. Three interrelated linear models were constructed using two terms (CO2/N2-based SSAs and OC) that were significant (p <0.001) in explaining 51 and 95% of the variability observed in As(V) sorption and bioaccessibility, respectively. The proposed models successfully predicted bioaccessible As concentrations for 4 out of the 5 soils that were not included in the bioaccessibility models, reaching RMSE values of < or =10%.     

Food authenticity using natural carbon isotopes (12C, 13C, 14C) in grass-fed and grain-fed beef

Natural carbon isotopes, ¹²C, ¹³C, and ¹⁴C, help to authenticate/trace foods and beverages. Levels of total carbon (TC), ¹³C (δ¹³C), and ¹⁴C in muscle and lipid tissues from grass-fed versus grain-fed steers are reported. The δ¹³C in muscle versus lipid of steaks were around 5‰ higher in grain over grass-fed (p<0.05). The δ¹³C and ¹⁴C levels were higher in muscle over lipid tissues while the opposite was true for TC (p<0.05). TC content was around 20% higher in lipid over muscle due to different elemental compositions, lipid versus muscle, not carbon isotopes discrimination.     

Investigation of the transport and deposition of fullerene (C60) nanoparticles in quartz sands under varying flow conditions

A coupled experimental and mathematical modeling investigation was undertaken to explore nanoscale fullerene aggregate (nC60) transport and deposition in water-saturated porous media. Column experiments were conducted with four different size fractions of Ottawa sand at two pore-water velocities. A mathematical model that incorporates nonequilibrium attachment kinetics and a maximum retention capacity was used to simulate experimental nC60 effluent breakthrough curves and deposition profiles. Fitted maximum retention capacities (S(max)), which ranged from 0.44 to 13.99 microg/g, are found to be correlated to normalized mass flux. The developed correlation provides a means to estimate S(max) as a function of flow velocity, nanoparticle size, and mean grain size of the porous medium. Collision efficiency factors, estimated from fitted attachment rate coefficients, are relatively constant (approximately 0.14) over the range of conditions considered. These fitted values, however, are more than 1 order of magnitude larger than the theoretical collision efficiency factor computed from Derjaguin-Landau-Verwey-Overbeek (DLVO) theory (0.009). Data analyses suggest that neither physical straining nor attraction to the secondary minimum is responsible for this discrepancy. Patch-wise surface charge heterogeneity on the sand grains is shown to be the likely contributor to the observed deviations from classical DLVO theory. These findings indicate that modifications to clean-bed filtration theory and consideration of surface heterogeneity are necessary to accurately predict nC60 transport behavior in saturated porous media.     

Quantitative changes in bacteria, amino acids and biogenic amines in sardine (Sardina pilchardus) stored at ambient temperature (25–28°C) and in ice

Freshly caught sardines contained high levels of bacteria located mainly on the skin and the gills. These bacteria invaded and grew rapidly in sardine muscle, reaching 5x10⁸ c.f.u. g^-1 and 6x10⁸ c.f.u. g^-1 respectively after 24h at ambient temperature and 8 days in ice.
Histidine, arginine, lysine, tyrosine and methionine levels decreased during storage. The other amino acids, except proline and taurine, accumulated in the fish muscle, indicating an extensive proteolysis.
Histamine, cadaverine and putrescine accumulated to levels of 2350ppm, 1050ppm and 300ppm respectively, after 24h storage at ambient temperature. Histamine and cadaverine reached similar levels after 8 days storage in ice, whereas putrescine formation was insignificant. Spermidine and spermine levels increased slightly under ambient conditions.
Salting the fish at 8% delayed bacterial and chemical changes but only in iced sardines.
The high content of free histidine found in sardines and the susceptibility of its muscle to histamine and cadaverine formation could explain its increasing implication in incidents of histamine poisoning.     

Studies on hygroscopic moisture transport in Norway spruce (Picea abies) Part 1: Sorption measurements of spruce exposed to cyclic step changes in relative humidity

Picea abies ) have been exposed to repetitive daily and weekly step changes in relative humidity with the surrounding temperature at an approximate constant level. The results show that the moisture sorption is a two-step sorption process with the major change in moisture content in the first fast initial part. The major part of the moisture change happens within a relatively short period of time. No significant phase lag has been observed for neither transverse nor longitudinal specimens up to 10 mm thickness. The moisture change in absorption is slightly different from the moisture change in desorption. Curves in absorption and desorption for specimens with both transverse and longitudinal direction are rather similar in shape.

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Picea abies) wurden im Wechselklima mit t?glichen und w?chentlichen Feuchtezyklen bei konstanter Umgebungstemperatur ausgesetzt. Der Sorptionsvorgang erwies sich als zweistufiger Proze?, wobei die haupts?chliche Feuchte?nderung in einer anf?nglichen raschen Stufe erfolgt. Eine signifikante Phasenverz?gerung konnte nicht beobachtet werden, weder für quergeschnitte noch für longitudinale Proben bis 10 mm Dicke. Die Feuchte?nderung bei der Adsorption unterscheidet sich geringfügig von der bei der Desorption. Die Sorptionskurven für Quer- und L?ngsproben haben einen sehr ?hnlichen Verlauf.

     

Biotransformation enzymes and thyroid axis disruption in juvenile rainbow trout (Oncorhynchus mykiss) exposed to hexabromocyclododecane diastereoisomers

Juvenile rainbow trout (Oncorhynchus mykiss) were fed either a reference diet or one of three diets enriched with alpha, beta, or gamma diastereoisomers of hexabromocyclododecane (HBCD, C12H18Br6) for 56 days. This exposure period was followed by 112 days during which all fish were fed the reference diet. Potential effects of HBCD on phase I and II biotransformation enzyme activities and thyroid axis disruption were examined. Disruption of the thyroid axis was most evident in the gamma-HBCD exposed group, as indicated by lower circular FT4 and higher FT3 as well as an increase in thyroid epithelial cell height. However, fish fed the alpha-HBCD enriched diet also exhibited altered glucuronyltransferase activity and thyroid epithelial cell heights and the beta-HBCD group had altered FT4 and FT3 and glucuronyltransferase activity. T4ORD activity was not affected after 14 days, but was significantly lower among all HBCD exposed fish compared to the reference fish after 56 days. Results from these experiments indicate that all isomers have the potential to disrupt thyroid homeostasis.     

Fatty acids,volatile compounds and colour changes in high-pressure-treated oysters (Crassostrea gigas)

Proximal composition, colour and levels of fatty acids and volatile compounds in oysters following high-pressure (HP) treatment at 260, 500 or 800 MPa for 3, 5 or 5 min, respectively, were investigated and compared to untreated oysters. HP-treated oysters had significantly (P < 0.05) higher pH than untreated oysters. HP treatment also modified the gross composition of oyster tissue, the moisture content of HP-treated oyster being higher than that of untreated oyster. HP treatment at 260 MPa had less negative effects on oyster tissue colour (Hunter L-, a- and b-values) than treatment at higher pressures. HP treatment of oysters resulted in no significant changes in the fatty acid profile compared to untreated oysters. HP treatment of oysters, however, changed the level of volatile components when compared to the headspace of fresh oysters; HP-treated samples had higher concentrations of dimethyl sulfide, 1-penten-3-one, phenol and 1,2,4-trimethylbenzene relative to untreated samples. On the other hand, HP-treated oysters had lower concentrations of 1-penten-3-ol, 2,3-pentanedione, (E,E,Z)-1,3,5-octatriene and 1,3-octadiene than untreated samples.Industrial relevanceHigh-pressure (HP) treatment is being increasingly employed for commercial processing of oysters. While the profiles of fatty acids and volatiles of fresh oysters have been extensively studied, no studies reporting the effects of HP on these have been reported. Compared to fresh oysters, HP treatment did not change significantly the fatty acid profile; however, differences in the headspace volatile profile of HP-treated oysters were noticed.     

Assessing soil microbial populations responding to crude-oil amendment at different temperatures using phylogenetic, functional gene (alkB) and physiological analyses

The effect of temperature as a determinant for selecting microbial populations associated with alkane-degradation was examined in crude oil-amended soil microcosms. After a 30-day incubation, >95% of n-alkane components in the crude-oil were depleted and approximately 40 and 60% of added [14C] hexadecane was converted to 14CO2 at 4-10 and 25 degrees C, respectively. Concomitant with crude-oil depletion, 16S rRNA gene sequence analysis revealed the emergence of a prominent Rhodococcus-like 16S rRNA sequence at all temperatures and a prominent Pseudomonas-like sequence at 4 and 10 degrees C. The diversity of alkane hydroxylase genes (alkB) associated with the amendments was examined using group-specific alkB-PCR primerstargeting phylogenetically distinct groups of alkane-degrading bacteria and subsequent cloning, denaturing gradient gel electrophoresis and sequencing analyses. Diverse Rhodococcus-alkB genes were detected at all temperatures, while a single prominent Pseudomonas-alkB genotype was detected only at lower temperatures. Two isolates obtained from the microcosms were shown to have 16S rRNA and alkB genes identical to those observed and were used to examine growth as a function of temperature. The Pseudomonas isolate exhibited a substantially higher growth rate at 4 and 10 degrees C than the Rhodococcus isolate, consistent with the inference that differences in adaptation to low temperature explain the observed shift in populations. High resolution analysis of alkB genes enabled the differentiation of distinct alkane-degrading populations responding to crude-oil amendment from other closely related, well-studied strains with different temperature adaptations.     

Use of perfused isolated muscle, as studied by (31)P NMR, to investigate metabolism and post-mortem changes

An experimental system was designed to study as independently as possible the effects of various in-vivo or post-mortem factors susceptible to influence muscle metabolism. This system was made up of an NMR probe, a physiological stimulator, a perfusion system and a force monitoring device. Rabbit muscles were isolated and perfused with bovine red cells, then put into the NMR probe to follow the evolution of pH and phosphorylated compounds. It was possible to keep muscle metabolism stable for 2 h. Death was simulated by stopping the perfusion which allowed post-mortem changes to be followed. The effects of adrenaline perfusion or of a 5 s tetanus on some traits of metabolism and on changes following muscle death were studied. Tetanus immediately before perfusion was stopped accelerated changes in pH and in phosphocreatine and ATP contents; adrenaline perfusion during 30 min before perfusion was stopped had little effect on these traits.