Elucidation of lead-induced oxidative stress in Talinum triangulare roots by analysis of antioxidant responses and DNA damage at cellular level

Hydroponic experiments were performed with Talinum triangulare (Jacq.) Willd. focusing the root cellular biochemistry with special emphasis on DNA damage, structural, and elemental analyses in Pb(NO₃)₂ exposed with 0, 0.25, 0.5, 0.75, 1.0, and 1.25 mM for 7 days. Lead (Pb) increased reactive oxygen species production, lipid peroxidation, protein oxidation, cell death, and DNA damage and decreased the protein content in a dose-dependent manner. Likewise, a dose-dependent induction of antioxidative enzymes superoxide dismutase and catalase by Pb was evident. Ascorbate peroxidase on the other hand responded biphasically to Pb treatments by showing induction at low (0.25 and 0.50) and repression at high (0.75–1.25 mM) concentrations. The estimation of proline content also indicated a similar biphasic trend. Scanning electron microscope and energy-dispersive X-ray spectroscopy analysis showed that 1.25 mM Pb treatment resulted in ultrastructural modifications in roots and stem tissue that was marked by the change in the elemental profile. The findings pointed to the role of oxidative stress in the underlying Pb phytotoxicity and genotoxicity in T. triangulare.     

Health care industries: potential generators of genotoxic waste

Health care waste includes all the waste generated by health care establishments, research facilities, and laboratories. This constitutes a variety of chemical substances, such as pharmaceuticals, radionuclides, solvents, and disinfectants. Recently, scientists and environmentalists have discovered that wastewater produced by hospitals possesses toxic properties due to various toxic chemicals and pharmaceuticals capable of causing environmental impacts and even lethal effects to organisms in aquatic ecosystems. Many of these compounds resist normal wastewater treatment and end up in surface waters. Besides aquatic organisms, humans can be exposed through drinking water produced from contaminated surface water. Indeed, some of the substances found in wastewaters are genotoxic and are suspected to be potential contributors to certain cancers. The aim of this study was to evaluate the genotoxic and cytotoxic potential of wastewaters from two hospitals and three clinical diagnostic centers located in Jaipur (Rajasthan State), India using the prokaryotic Salmonella mutagenicity assay (Ames assay) and the eukaryotic Saccharomyces cerevisiae respiration inhibition assay. In the Ames assay, untreated wastewaters from both of the health care sectors resulted in significantly increased numbers of revertant colonies up to 1,000–4,050 as measured by the Salmonella typhimurium TA98 and TA100 strains (with and without metabolic activation) after exposure to undiluted samples, which indicated the highly genotoxic nature of these wastewaters. Furthermore, both hospital and diagnostic samples were found to be highly cytotoxic. Effective concentrations at which 20 % (EC₂₀) and 50 % (EC₅₀) inhibition of the respiration rate of the cells occurred ranged between ～0.00 and 0.52 % and between 0.005 and 41.30 % (calculated with the help of the MS excel software XLSTAT 2012.1.01; Addinsoft), respectively, as determined by the S. cerevisiae assay. The results indicated that hospital wastewaters contain genotoxic and cytotoxic components. In addition, diagnostic centers also represent small but significant sources of genotoxic and cytotoxic wastes.     

Hydrothermal synthesis of meso/macroporous BiVO4 hierarchical particles and their photocatalytic degradation properties under visible light irradiation

An ordered hierarchical meso/macroporous monoclinic bismuth vanadate (BiVO₄) particle was fabricated for the first time by a simple two-step melamine template hydrothermal method followed by calcination. The physiochemical parameters of as-prepared porous materials were characterized by means of X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Raman, Barrett–Emmett–Teller, and UV–vis techniques. The nitrogen adsorption–desorption measurement and pore size distribution curve suggest that meso/macropores exist in these hierarchical microarchitectures. Further, it is found that melamine plays a significant role in the formation of porous BiVO₄ particles, and when a known amount of melamine was added, the surface area and pore size of such porous BiVO₄ particles were increased. The photocatalytic activities of the as-prepared hierarchical BiVO₄ samples were measured for the photodegradation of Congo red aqueous dye solution under visible light irradiation. Surprisingly, the porous BiVO₄ particles showed outstanding photocatalytic activities than polycrystalline BiVO₄ sample. The possible enhancement of such catalytic performance has also been further discussed.     

Impact of nano-CuO stress on rice (Oryza sativa L.) seedlings

Indiscriminate release of metal oxide nanoparticles (NPs) into the environment due to anthropogenic activities has become a serious threat to the ecological system including plants. The present study assesses the toxicity of nano-CuO on rice (Oryza sativa cv. Swarna) seedlings. Three different levels of stress (0.5 mM, 1.0 mM and 1.5 mM suspensions of copper II oxide, <50 nm particle size) were imposed and seedling growth performance was studied along control at 7 and 14 d of experiment. Modulation of ascorbate–glutathione cycle, membrane damage, in vivo ROS detection, foliar H₂O₂ and proline accumulation under nano-CuO stress were investigated in detail to get an overview of nano-stress response of rice. Seed germination percentage was significantly reduced under stress. Higher uptake of Evans blue by nano-CuO stressed roots over control indicates loss of root cells viability. Presence of dark blue and deep brown spots on leaves evident after histochemical staining with NBT and DAB respectively indicate severe oxidative burst under nano-copper stress. APX activity was found to be significantly increased in 1.0 and 1.5 mM CuO treatments. Nevertheless, elevated APX activity might be insufficient to scavenge all H₂O₂ produced in excess under nano-CuO stress. That may be the reason why stressed leaves accumulated significantly higher H₂O₂ instead of having enhanced APX activity. In addition, increased GR activity coupled with isolated increase in GSH/GSSG ratio does not seem to prevent cells from oxidative damages, as evident from higher MDA level in leaves of nano-CuO stressed seedlings over control. Enhanced proline accumulation also does not give much protection against nano-CuO stress. Decline in carotenoids level might be another determining factor of meager performance of rice seedlings in combating nano-CuO stress induced oxidative damages.     

Development of a highly sensitive extractive spectrophotometric method for the determination of nickel(II) from environmental matrices using N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone

Nickel(II) reacts with N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone (ECCT) and forms a yellow colored complex, which was extracted into n-butanol from sodium acetate and acetic acid buffer at pH 6.0. The absorbance value of the Ni(II)-ECCT complex was measured at different intervals of time at 400nm, to ascertain the time stability of the complex. The extraction of the complex into the solvent was instantaneous and stable for more than 72h. The system obeyed Beer's law in the concentration range of 1.2-5.6mugml(-1) of nickel(II), with an excellent linearity and a correlation coefficient of 0.999. The molar absorptivity and Sandell's sensitivity of the extracted species were found to be 1.114x10(4)Lmol(-1)cm(-1) and 5.29x10(-3)mugcm(-2) at 400nm, respectively. Hence, a detailed study of the extraction of nickel(II) with ECCT has been undertaken with a view to developing a rapid and sensitive extractive spectrophotometric method for the determination of nickel(II) when present alone or in the presence of diverse ions which are usually associated with nickel(II) in environmental matrices like soil and industrial effluents. Various standard alloy samples (CM 247 LC, IN 718, BCS 233, 266, 253 and 251) have been tested for the determination of nickel for the purpose of validation of the present method. The results of the proposed method are comparable with those from atomic absorption spectrometry and were found to be in good agreement.     

Laccase mediated biodegradation of 2,4-dichlorophenol using response surface methodology

The effects of different environmental parameters, i.e., pH, temperature, time and enzyme concentration on the biodegradation of 2,4-dichlorophenol (2,4-DCP) in aqueous phase was evaluated with laccase from Pleurotus sp. using response surface methodology (RSM) in the present investigation. The Box-Behnken design of experiments was used to construct second order response surfaces with the investigated parameters. It was observed that the maximum degradation efficiency of approximately 98% was achieved at pH 6, temperature of 40 degrees C, time 9h and an enzyme concentration of 8IUml(-1). The adequacy of the model was confirmed by the coefficient of multiple regression, R(2) and adjusted R(2) which were adjudged to be 87.9% and 73.6%, respectively indicating a reasonably good model for practical implementation. Despite the fact that many successful attempts have been taken in the past for biodegradation of 2,4-DCP using whole cells, the present study emphasizes the fastest biodegradation of 2,4-DCP, a potent xenobiotic compound.     

Genotoxicity assessment of acute exposure of chlorpyrifos to freshwater fish Channa punctatus (Bloch) using micronucleus assay and alkaline single-cell gel electrophoresis

Chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridylphosphorothioate) is one of the organophosphate pesticides widely used in agricultural practices throughout world and irreversible inhibitor of cholinesterase in all animal species. Limited efforts have been made to study acute genotoxic effects of chlorpyrifos (CPF) in different tissues of fish using genotoxic biomarkers. Therefore, the present investigation was aimed to study the induction of DNA damage by CPF in freshwater teleost fish Channapunctatus using micronucleus assay (MN assay) and alkaline single-cell gel electrophoresis (comet assay). The value of LC(50) - 96 h of CPF was determined as 811.98 microgl(-1) for C. punctatus, in a semi-static system and on the basis of LC(50) value three acute concentrations viz., 203, 406 and 609 microgl(-1) were determined. The fishes were exposed to the different concentrations of CPF for 96 h and samplings were done at regular intervals for assessment of the MN frequencies and DNA damage. In general, significant effects (P<0.01) from both concentrations and time of exposure were observed in exposed fishes. It was found that the micronucleus induction was highest on 96 h at all concentrations in the peripheral blood. Similar trend was observed for the DNA damage measured in terms of the percentage of tail DNA in the lymphocyte and gill cells. This study explored the combined use of micronucleus assay and comet assay for in vivo laboratory studies using fresh water fish for screening the genotoxic potential of xenobiotics.     

A comparison of sediment quality guidelines for toxicity assessment in the Sunderban wetlands (Bay of Bengal, India)

The aim of this paper was to obtain the first screening ecotoxicological risk evaluation in the Sunderban wetlands, the largest prograding delta in the estuarine phase of the River Ganges. The characterization of exposure was conducted by means of an extensive survey of several persistent organic pollutants (PAHs, PCBs, DDTs, PBDEs, HCHs, HCB) measured in seven core sediments from the Sunderban wetlands, obtaining a dataset with more than 2200 analyses. The pollutant effects were assessed by the use of three different sediment quality guidelines (SQGs) previously developed in the literature to evaluate toxicity induced in sediment-dwelling organisms. The three different approaches chosen for risk assessment of the Sunderban were the consensus SQGs obtained by TEC (threshold effect concentration), PEC (probable effect concentration) and EEC (extreme effect concentration), the threshold/probable effect level (TEL/PEL) approach and, finally, the ERL-ERM guidelines, including the m-ERM-Q (mean ERM quotient). The evaluation of the toxicity induced by a mixture of the target pollutants indicated the importance of gamma-HCH contamination in the Sunderban sediments despite the very low concentrations measured in core sediments. A different sensitivity for toxicity assessment due to quality guidelines was obtained, as the consensus SQGs based on TEC were less conservative and protective than the TEL and ERL approaches, while the use of m-ERM-Q seems to be the most powerful tool to predict the toxicity related to a contaminant mixture.     

X-ray absorption and photoelectron spectroscopy investigation of selenite reduction by Fe-bearing minerals

The long-lived radionuclide ⁷⁹Se is one of the elements of concern for the safe storage of high-level nuclear waste, since clay minerals in engineered barriers and natural aquifer sediments strongly adsorb cationic species, but to lesser extent anions like selenate (Se^VIO₄²⁻) and selenite (Se^IVO₃²⁻). Previous investigations have demonstrated, however, that Se^IV and Se^VI are reduced by surface-associated Fe^II, thereby forming insoluble Se⁰ and Fe selenides. Here we show that the mixed Fe^II/^III (hydr)oxides green rust and magnetite, and the Fe^II sulfide mackinawite reduce selenite rapidly (< 1 day) to FeSe, while the slightly slower reduction by the Fe^II carbonate siderite produces elemental Se. In the case of mackinawite, both S^−II and Fe^II surface atoms are oxidized at a ratio of one to four by producing a defective mackinawite surface. Comparison of these spectroscopic results with thermodynamic equilibrium modeling provides evidence that the nature of reduction end product in these Fe^II systems is controlled by the concentration of HSe⁻; Se⁰ forms only at lower HSe⁻ concentrations related to slower HSeO₃⁻ reduction kinetics. Even under thermodynamically unstable conditions, the initially formed Se solid phases may remain stable for longer periods since their low solubility prevents the dissolution required for a phase transformation into more stable solids. The reduction by Fe²⁺-montmorillonite is generally much slower and restricted to a pH range, where selenite is adsorbed (pH < 7), stressing the importance of a heterogeneous, surface-enhanced electron transfer reaction. Although the solids precipitated by the redox reaction are nanocrystalline, their solubility remains below 6.3 × 10^− 8 M. No evidence for aqueous metal selenide colloids nor for Se sorption to colloidal phases was found. Since Fe^II phases like the ones investigated here should be ubiquitous in the near field of nuclear waste disposals as well as in the surrounding aquifers, mobility of the fission product ⁷⁹Se may be much lower than previously assumed.