Physiological and biochemical characteristic of Miscanthus × giganteus grown in heavy metal - oil sludge co-contaminated soil.

The effect of oil sludge and zinc, present in soil both separately and as a mixture on the physiological and biochemical parameters of Miscanthus × giganteus plant was examined in a pot experiment. The opposite effect of pollutants on the accumulation of plant biomass was established: in comparison with uncontaminated control the oil sludge increased, and Zn reduced the root and shoot biomass. Oil sludge had an inhibitory effect on the plant photosynthetic apparatus, which intensified in the presence of Zn. The specific antioxidant response of M. × giganteus to the presence of both pollutants was a marked increase in the activity of superoxide dismutase (mostly owing to oil sludge) and glutathione-S-transferase (mostly owing to zinc) in the shoots. The participation of glutathione-S-transferase in the detoxification of both the organic and the inorganic pollutants was assumed. Zn inhibited the activity of laccase-like oxidase, whereas oil sludge promoted laccase and ascorbate oxidase activities. This finding suggests that these enzymes play a part in the oxidative detoxification of the organic pollutаnt. With both pollutants used jointly, Zn accumulation in the roots increased 6-fold, leading to increase in the efficiency of soil clean-up from the metal. In turn, Zn did not significantly affect the soil clean-up from oil sludge. This study shows for the first time the effect of co-contamination of soil with oil sludge and Zn on the physiological and biochemical characteristics of the bioenergetic plant M. × giganteus. The data obtained are important for understanding the mechanisms of phytoremediation with this plant.

Combined effects of cadmium and oil sludge on sorghum: growth, physiology, and contaminant removal.

The physiological and biochemical responses of Sorghum bicolor (L.) Moench. to cadmium (Cd) (30 mg kg-1) and oil sludge (OS) (16 g kg-1) present in soil both separately and as a mixture were studied in pot experiments. The addition of oil sludge as a co-contaminant decreased Cd entry into the plant by almost 80% and simultaneously decreased the stimulation of superoxide dismutase (SOD) and peroxidase. The decrease in glutathione reductase (GR) activity and the increase in glutathione-S-transferase (GST) activity under the influence of oil sludge indicated that its components were detoxified by conjugation with glutathione. Cd additionally activated the antioxidant and detoxifying potential of the plant enzymatic response to stress. This helped to enhance the degradation rate of oil sludge in the rhizosphere, in which the participation of the root-released enzymes in the degradation could be possible. Cd increased the extent of soil clean-up from oil sludge, mainly owing to the elimination of paraffins, naphthenes, and mono- and bicyclic aromatic hydrocarbons. The mutual influence of the pollutants on the biochemical responses of sorghum and on soil clean-up was evaluated. The results are important for understanding the antistress and detoxification responses of the remediating plant to combined environmental pollution.

Photodynamic opening of the blood-brain barrier and pathways of brain clearing.

A new application of the photodynamic treatment (PDT) is presented for the opening of blood-brain barrier (BBB) and the brain clearing activation that is associated with it, including the use of gold nanoparticles as emerging photosensitizer carriers in PDT. The obtained results clearly demonstrate 2 pathways for the brain clearing: (1) using PDT-opening of BBB and intravenous injection of FITC-dextran we showed a clearance of this tracer via the meningeal lymphatic system in the subdural space; (2) using optical coherence tomography and intraparenchymal injection of gold nanorods, we observed their clearance through the exit gate of cerebral spinal fluid from the brain into the deep cervical lymph node, where the gold nanorods were accumulated. These data contribute to a better understanding of the cerebrovascular effects of PDT and shed light on mechanisms, underlying brain clearing after PDT-related opening of BBB, including clearance from nanoparticles as drug carriers.

Effect of cadmium stress and inoculation with a heavy-metal-resistant bacterium on the growth and enzyme activity of Sorghum bicolor.

In this study, the influence of the heavy-metal-resistant rhizobacterial inoculant Rhodococcus ruber N7 on the growth and enzyme activity of Sorghum bicolor (L.) Moench. under cadmium stress was investigated in quartz sand pot experiments. The effect of cadmium and bacterium on the plant biomass accumulation, photosynthetic pigments, protein content, and the activities of plant-tissue enzymes such as peroxidase, laccase, and tyrosinase were estimated. It was shown that the presence of cadmium in the sand influenced the roots to a greater extent than it influenced the aerial parts of sorghum. This is manifested as increased protein content, reduced activity of peroxidase, and increased activity of laccase. Compared with cadmium stress, inoculation of plants with rhizobacterium R. ruber N7 has a stronger (and often opposite) effect on the biochemical parameters of sorghum, including a decrease in the concentration of protein in the plant, but increased the activity of peroxidase, laccase, and tyrosinase. Under cadmium contamination of sand, R. ruber N7 successfully colonizes the roots of Sorghum bicolor, survives in its root zone, and contributes to the accumulation of the metal in the plant roots, thereby reducing the concentration of the pollutant in the environment.

Diverse effects of arsenic on selected enzyme activities in soil-plant-microbe interactions.

Under the influence of pollutants, enzyme activities in plant-microbe-soil systems undergo changes of great importance in predicting soil-plant-microbe interactions, regulation of metal and nutrient uptake, and, ultimately, improvement of soil health and fertility. We evaluated the influence of As on soil enzyme activities and the effectiveness of five field crops for As phytoextraction. The initial As concentration in soil was 50mg As kg(-1) soil; planted clean soil, unplanted polluted soil, and unplanted clean soil served as controls. After 10 weeks, the growth of the plants elevated soil dehydrogenase activity relative to polluted but unplanted control soils by 2.4- and 2.5-fold for sorghum and sunflower (respectively), by 3-fold for ryegrass and sudangrass, and by 5.2-fold for spring rape. Soil peroxidase activity increased by 33% with ryegrass and rape, while soil phosphatase activity was directly correlated with residual As (correlation coefficient R(2)=0.7045). We conclude that soil enzyme activities should be taken into account when selecting plants for phytoremediation.

Toxicity of arsenic species to Lemna gibba L. and the influence of phosphate on arsenic bioavailability.

The toxicity of arsenic (As) species to Lemna gibba L. and the influence of PO(4) (3-) on As bioavailability and uptake were tested in batch culture. L. gibba were exposed to six test concentrations of NaHAsO(4). 7H(2)O and NaAsO(3), with 0, 0.0136, 13.6, and 40 mg L(-1) KH(2)PO(4). In batch culture As toxicity to L. gibba did not relate linearly to As concentration. The growth rate, related to frond number as recommended by OECD and ISO/DIN, was significantly inhibited in fronds exposed to 20-50 microg L(-1) As(III) compared with fronds exposed to As(V). The growth rate was stimulated when plants were exposed to 50-250 microg L(-1) of both As(III) and As(V). After exposure to 300-800 microg L(-1) growth inhibition was significantly higher for As(III) than for As(V), whereas above 800 microg L(-1) As(V) was inhibited the most. The bioaccumulation of As(III) and As(V) was significantly higher for P-deficient cultures (0.98 +/- 0.08 and 1.02 +/- 0.19 g kg(-1), respectively for 0.0136 mg L(-1) PO(4) (3-)) than for P-sufficient cultures (243 and 343 mg kg(-1) for 40 mg L(-1), respectively). Plants exposed to As(V) had uptake and accumulation values slightly higher than did plants exposed to As(III). No significant differences in bioaccumulation were found between plants exposed to a concentration of As(III) >1 mg L(-1) and those exposed to As(V) at the same concentration. This indicates a direct relationship to P content in the culture. Toxicity may result from the uptake of As(V) instead of PO(4) (3-) as a result of ion competition during uptake because of close thermodynamic properties, which may change the interaction among components in the media. The toxicity pattern is interpreted as a manifestation of changing speciation in the batch culture and of the oxidation of As(III) to As(V) in an oxygen-rich environment.