A study of the mechanism of in vitro cytotoxicity of metal oxide nanoparticles using catfish primary hepatocytes and human HepG2 cells

Nanoparticles (NPs), including nanometal oxides, are being used in diverse applications such as medicine, clothing, cosmetics and food. In order to promote the safe development of nanotechnology, it is essential to assess the potential adverse health consequences associated with human exposure. The liver is a target site for NP toxicity, due to NP accumulation within it after ingestion, inhalation or absorption. The toxicity of nano-ZnO, TiO₂, CuO and Co₃O₄ was investigated using a primary culture of channel catfish hepatocytes and human HepG2 cells as in vitro model systems for assessing the impact of metal oxide NPs on human and environmental health. Some mechanisms of nanotoxicity were determined by using phase contrast inverted microscopy, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, reactive oxygen species (ROS) assays, and flow cytometric assays. Nano-CuO and ZnO showed significant toxicity in both HepG2 cells and catfish primary hepatocytes. The results demonstrate that HepG2 cells are more sensitive than catfish primary hepatocytes to the toxicity of metal oxide NPs. The overall ranking of the toxicity of metal oxides to the test cells is as follows: TiO₂ < Co₃O₄ < ZnO < CuO. The toxicity is due not only to ROS-induced cell death, but also to damages to cell and mitochondrial membranes.     

In vitro evaluation of the cytotoxicity of iron oxide nanoparticles with different coatings and different sizes in A3 human T lymphocytes

The ever expanding use of engineered nanoscaled materials has brought about a commensurate growth in concern about their potential risks to human and environmental health. Toxicity of nanoparticles could vary with their physicochemical parameters. The dependence of cytotoxicity on particle size and surface coating of iron oxide nanoparticles was investigated in this in vitro study using the A3 human T lymphocyte as a model. Two different sizes (10 nm and 50 nm) and two different surface coatings (amine and carboxyl groups) of iron oxide (IO) nanoparticles were tested with fluorescein diacetate (FDA) assay and WST-1 assay. In the 1-h FDA assay with PBS, IO nanoparticles did not show size-dependent toxicity to A3 cells in terms of mass concentration; however, in terms of the number of particles per well and the total surface area, they did exhibit size-dependent toxicity. Fifty nanometer IO nanoparticles are more toxic than the 10 nm counterparts. The results of both the 24-h FDA and WST-1 assays in a complete growth medium indicate size- and surface coating-dependent toxicity to A3 cells in terms of mass concentration. IO nanoparticles of the smaller size are more toxic than those of the larger size. IO nanoparticles with the carboxyl group have a higher toxicity than those with the amine group. However, in the 24-h FDA assay, in terms of the number of particles per well and the resultant total surface area per well, the 50 nm IO nanoparticles are more toxic than those of size 10 nm. In terms of mass concentration, the number of particles per well and the total surface area, both of the 24-h assays showed the consistent results that IO nanoparticles with the carboxyl group have a higher toxicity than those with the amine group.     

Delineation of Pb contamination pathways in two Pectinidae: The variegated scallop Chlamys varia and the king scallop Pecten maximus

Bioaccumulation of Pb was determined in Chlamys varia and Pecten maximus exposed to ²¹⁰Pb via seawater, food and sediment. Both scallops readily concentrated dissolved Pb with whole-body 7-d concentration factors of 250 ± 40 and 170 ± 70, respectively. In both species, more than 70% of Pb taken up from seawater was strongly retained within tissues (biological half-life > 1.5 month) whereas Pb ingested with phytoplankton was poorly assimilated (< 20%). As P. maximus lives buried in the sediment, this exposure pathway was assessed and showed low bioaccumulation efficiency for sediment-bound Pb (transfer factor < 0.015). Despite the poor transfer efficiency of Pb from food and sediment, the use of a global bioaccumulation model indicated that the particulate pathway (food and/or sediment) constituted the major bioaccumulation route of Pb in both scallops. Whatever the exposure pathway, the digestive gland and kidneys always played a major role in Pb accumulation. In scallop tissues, Pb was predominantly associated with the insoluble subcellular fraction, suggesting a low bioavailability of Pb for scallop consumers.     

Phenolic compounds of Pinus laricio needles: A bioindicator of the effects of prescribed burning in function of season

Fire is a dominant ecological factor in Mediterranean-type ecosystems. Forest management includes many preventive tools, in particular for fire prevention, such as mechanical treatments and prescribed burning. Prescribed burning is a commonly used method for treating fuel loads, but fuel reduction targets for reducing wildfire hazards must be balanced against fuel retention targets in order to maintain habitat and other forest functions. This approach was used on Pinus nigra ssp laricio var. Corsicana, a pine endemic to Corsica of great ecological and economic importance. Many studies of plant phenolic compounds have been carried out concerning responses to various stresses. The aim of this study was to understand i) the effects of prescribed burning 1 to 16 months later and ii) the effects of the seasonality of burning, spring or fall, on the production of phenolic compounds in Pinus laricio. After prescribed burning conducted in spring, Pinus laricio increases the synthesis of total phenolic compounds for a period of 7 months. The increase is greater after spring-burning than fall-burning. With regard to simple phenols, only dihydroferulic acid responds about 1 year after both types of prescribed burning. The causes of these increases are discussed in this paper. Total phenolic compounds could be used as a bioindicator for the short-term response of Pinus laricio needles to prescribed burning. Simple phenols may be useful for revealing the medium-term effects of prescribed burning. The results of this study include recommending forest managers to use prescribed burning in the fall rather than spring to reduce fuel loads and have less impact on the trees.     

A seasonal study of the mecA gene and Staphylococcus aureus including methicillin-resistant S. aureus in a municipal wastewater treatment plant

The spread of methicillin-resistant Staphylococcus aureus (MRSA), in which the mecA gene mediates resistance, threatens the treatment of staphylococcal diseases. The aims were to determine the effect of wastewater treatment processes on mecA gene concentrations, and the prevalence of S. aureus and MRSA over time. To achieve this a municipal wastewater treatment plant was investigated for the mecA gene, S. aureus and MRSA, using real-time PCR assays. Water samples were collected monthly for one year, at eight sites in the plant, reflecting different aspects of the treatment process. The mecA gene and S. aureus could be detected throughout the year at all sampling sites. MRSA could also be detected, but mainly in the early treatment steps. The presence of MRSA was verified through cultivation from inlet water. The concentration of the mecA gene varied between months and sampling sites, but no obvious seasonal variation could be determined. The wastewater treatment process reduced the mecA gene concentration in most months. Taken together our results show that the mecA gene, S. aureus and MRSA occur over the year at all sites investigated.     

Determination of the optimal parameters in regression models for the prediction of chlorophyll-a: A case study of the Yeongsan Reservoir, Korea

Statistical regression models involve linear equations, which often lead to significant prediction errors due to poor statistical stability and accuracy. This concern arises from multicollinearity in the models, which may drastically affect model performance in terms of a trade-off scenario for effective water resource management logistics. In this paper, we propose a new methodology for improving the statistical stability and accuracy of regression models, and then show how to cope with pitfalls in the models and determine optimal parameters with a decreased number of predictive variables. Here, a comparison of the predictive performance was made using four types of multiple linear regression (MLR) and principal component regression (PCR) models in the prediction of chlorophyll-a (chl-a) concentration in the Yeongsan (YS) Reservoir, Korea, an estuarine reservoir that historically suffers from high levels of nutrient input. During a 3-year water quality monitoring period, results showed that PCRs could be a compact solution for improving the accuracy of the models, as in each case MLR could not accurately produce reliable predictions due to a persistent collinearity problem. Furthermore, based on R² (goodness of fit) and F-overall number (confidence of regression), and the number of explanatory variables (R-F-N) curve, it was revealed that PCR-F(7) was the best model among the four regression models in predicting chl-a, having the fewest explanatory variables (seven) and the lowest uncertainty. Seven PCs were identified as significant variables, related to eight water quality parameters: pH, 5-day biochemical oxygen demand, total coliform, fecal indicator bacteria, chemical oxygen demand, ammonia-nitrogen, total nitrogen, and dissolved oxygen. Overall, the results not only demonstrated that the models employed successfully simulated chl-a in a reservoir in both the test and validation periods, but also suggested that the optimal parameters should cautiously be considered in the design of regression models.     

Effects of wind on the transmission heat loss in duo-pitched insulated roofs: A field study

This article presents measuring results of the thermal performance of duo-pitched tiled woodframe roof designs. The roofs have been monitored in a test building, exposed to the outside climate. The experiment was part of a programme to study the hygrothermal performance of highly insulated envelope parts in situ, in order to investigate whether a good thermal quality (U = 0.2 W/(m² K)) is achievable with current residential construction practices in Belgium. The results show the effect of wind on the thermal performance of duo-pitched roofs. The measured thermal properties of the roof components are compared to the design values, and related to the wind speeds and directions registered near the test building. The established thermal effects are explained using tracer gas tests to show the pattern of wind driven air flow in the roofs.     

The conservation of historic areas in the UK: A case study of “Grainger Town”, Newcastle upon Tyne

Conservation in the UK is generally regarded as having undergone a sea-change in the late 1960s and early 1970s, as policy- and decision-makers retreated from comprehensive development and embraced conservation. Using part of the city centre of Newcastle upon Tyne as a case study, this article examines this thesis. Beneath simple measures, such as the amount of the city centre which is classified as historic, a more complex picture emerges. A framework for interventions in the historic environment is theorised and there is found to be a continuing tension between conservation approaches which seek to visually manage the city and those which place stress on historic fabric and morphology.     

Pile burning of cutting debris in stands of hazel (Corylus avellana): An experimental study of smouldering combustion towards the validation of a burning protocol

Smouldering combustion in burning piles was experimentally investigated by studying temperature changes in six piles of 2 m of diameter of cutting debris of hazel (Corylus avellana) for three days after extinction. The piles were monitored using an IR camera and K-type thermocouples. The experiment was designed in order to study how the maximum temperature of the charcoal might be influenced by the individual and interaction effects of both the quality of extinction and the elapsed time until the start of extinction of the piles. The piles that were properly extinguished (i.e. using a high-pressure, homogeneously distributed water flow of 50 l/min for 4 min) had a uniform temperature profile and did not have significant hot spots. The temperature reached equilibrium with the environment in less than 10 h after extinction. In contrast, a smouldering front moved throughout the poorly extinguished piles, which had a wide temperature distribution and hot spots of up to 700 °C. A simulation of windy conditions after three days of experiments on a poorly extinguished pile showed that the reactivation of charcoal combustion was possible. It gave a high-risk scenario to cause a wildfire, with hot smouldering embers being transported by wind flow. The results are of interest to improve pile burning protocols so that the number of wildfires caused by such practices may be reduced.     

Bioaugmentation with the nicotine-degrading bacterium Pseudomonas sp. HF-1 in a sequencing batch reactor treating tobacco wastewater: Degradation study and analysis of its mechanisms

The highly effective nicotine-degrading bacterium Pseudomonas sp. HF-1 was augmented in an SBR system that is used to treat tobacco wastewater. Compared to the non-bioaugmented (non-BA) system, the bioaugmented (BA) system exhibited considerably stronger pollution disposal abilities, with 100% nicotine degradation and more than 84% chemical oxygen demand (COD) removal within 12 h. Nicotine degradation had a significant effect on COD removal in SBRs (r = 0.928, p < 0.01). The mechanisms of bioaugmentation were systematically investigated using a combination of polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) and a toxicity assay (protein carbonyl (PC) and DNA-protein crosslinking (DPC)). DGGE fingerprint profiles showed that the number of bands and the Shannon-Wiener index decreased at a nicotine load of 250 mg/L compared to a 40-130 mg/L nicotine load in the non-BA system. However, a stepwise increase in the Shannon-Wiener index was found during all periods in the BA system. A comparison of sequences excised from DGGE gels demonstrated significant differences in the dominant microbial species between the two SBRs. This result suggested that bioaugmentation of strain HF-1 could select cooperators for treating complicated tobacco wastewater. The PC content and the DPC coefficient increased significantly at levels higher than 80 mg/L in the non-BA system; nevertheless, no increase was observed in the BA system during the stepwise nicotine load. This indicated that bioaugmentation of strain HF-1 resulted in the maintenance of high treatment activity by minimizing the nicotine toxicity for other microbes in the BA system. In conclusion, the rapid nicotine degradation of strain HF-1 performed a vital function in SBR by influencing the microbial community structure, dynamics and activity of the activated sludge system.