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11.
AbstractThe roles of PM2.5-induced mitochondrial damage and oxidative stress on mast cell degranulation were examined in vitro. Mast cells were treated with suspensions of PM2.5 in Dulbecco’s modified Eagle’s medium at concentrations from 25 to 200?mg/L in the absence or presence of 10?mmol/L N-acetyl-L-cysteine. Biological effects and mitochondrial function were assessed by determining cell viability, β-hexosaminidase release, interleukin-4 secretion, reactive oxygen species generation, adenosine triphosphate production, potential alteration of mitochondrial membrane, and activities of mitochondrial electron transport chain complexes I and III. Exposure of mast cells to PM2.5 induced reduction of adenosine triphosphate production, collapse of mitochondrial membrane potential, and inhibition of the activity of complex III. Co-treatment of mast cells exposed to PM2.5 with N-acetyl-L-cysteine attenuated cytotoxicity and the production of reactive oxygen species, and decreased the release of β-hexosaminidase and interleukin-4. Evidently, PM2.5-induced oxidative stress plays an essential role in mitochondrial toxicity and mast cell activation. 相似文献
12.
针对交通荷载的作用特点设计了循环三轴试验,进而对交通荷载作用下饱和软粘土的动力特件进行厂研究.结果表明:循环荷载作用下,饱和软粘土存在临界循环应力比,采用孔压曲线所得到的临界循环应力比要小于采用应变曲线所得到的临界循环应力比.当土样不存在初始剪应力时,随着循环次数的增加,土样的应力-应变关系曲线近似原点对称,但随着初始剪应力的增大,应力-应变关系曲线逐渐表现为一系列平行曲线,峰值孔压与循环孔压幅值均逐渐减少;同时,轴应变的发展加快,但循环应变幅值逐渐减小.当循环应力比小于临界循环应力比时,对于同一初始剪应力,不同循环应力比下的孔压比-动应变曲线近似集中在同一条曲线上.通过对试验数据进行回归分析,得到了交通荷载作用下饱和软粘土残余孔压-累积塑性应变关系模型. 相似文献
13.
14.
Tim S. Nawrot Nino Kuenzli Jordi Sunyer Tingming Shi Teresa Moreno Mar Viana Joachim Heinrich Bertil Forsberg Frank J. Kelly Muhammad Sughis Benoit Nemery Paul Borm 《Atmospheric environment (Oxford, England : 1994)》2009,43(30):4595-4602
We assessed the extent to which constituents of PM2.5 (transition metals, sodium, chloride) contribute to the ability to generate hydroxyl radicals (OH) in vitro in PM2.5 sampled at 20 locations in 19 European centres participating in the European Community Respiratory Health Survey. PM2.5 samples (n = 716) were collected on filters over one year and the oxidative activity of particle suspensions obtained from these filters was then assessed by measuring their ability to generate OH in the presence of hydrogen peroxide. Associations between OH formation and the studied PM constituents were heterogeneous. The total explained variance ranged from 85% in Norwich to only 6% in Albacete. Among the 20 centres, 15 showed positive correlations between one or more of the measured transition metals (copper, iron, manganese, lead, vanadium and titanium) and OH formation. In 9 of 20 centres OH formation was negatively associated with chloride, and in 3 centres with sodium. Across 19 European cities, elements which explained the largest variations in OH formation were chloride, iron and sodium. 相似文献
15.
This study dealt with in situ removal of copper from sediments through an electrokinetic (EK) process driven by a galvanic cell. Iron (Fe) and carbon (C) were placed separately and connected with a conductive wire. Polluted sediments were put between them and water was filled above the sediments. The galvanic cell was thus formed due to the different electrode potentials of Fe and C. The cell could remove the pollutants in the sediments by electromigration and/or electroosmosis. Results showed that a weak voltage less than 1V was formed by the galvanic cell. The voltage decreased with the increase of time. A slight increase of sediment pH from the anode (Fe) to the cathode (C) was observed. The presence of supernatant water inhibited the variation of sediment pH because H(+) and OH(-) could diffuse into the water. The removal of copper was affected by the sediment pH and the distribution of electrolyte in sediment and supernatant water. Lower pH led to higher removal efficiency. More electrolyte in the sediment and/or less electrolyte in the supernatant water favored the removal of copper. The major removal mechanism was proposed on the basis of the desorption of copper from sediment to pore solution and the subsequent electromigration of copper from the anode to the cathode. The diffusion of copper from sediment to supernatant water was negligible. 相似文献
16.
Nimisha Singh 《Environmental pollution (Barking, Essex : 1987)》2009,157(2):371-376
Leaching of Cu and Zn from a composite of spent antifouling paint particles, containing about 300 mg g−1 and 110 mg g−1 of the respective metals, was studied in batch experiments. For a given set of simulated environmental conditions, release of Cu was independent of paint particle concentration due to attainment of pseudo-saturation, but Zn was less constrained by solubility effects and release increased with increasing particle concentration. Leaching of Cu increased but Zn decreased with increasing salinity, consistent with mechanisms governing the dissolution of Cu2O in the presence of chloride and Zn acrylates in the presence of seawater cations. Because of complex reaction kinetics and the presence of calcium carbonate in the paint matrix, metal leaching appeared to be greater at 4 °C than 19 °C under many conditions. These findings have important environmental and biological implications regarding the deliberate or inadvertent disposal of antifouling paint residues. 相似文献
17.
This paper develops a method for identifying and assessing long-term supply risks for mineral raw materials. The method is based on a combined evaluation of past and future supply and demand trends. By analysing raw material boom and bust cycles over the past 50 years, we have quantified indicators and defined benchmarks for identifying critical market situations. By applying the method, risks for supply shortage may be identified at an early stage. In addition, a numerical evaluation model has been developed for better comparison between various mineral raw materials. Compared to other assessment methods this method uses specific benchmarks for each raw material to better assess supply risks. The method is embedded within a systematic and comprehensive analytical approach. 相似文献
18.
六自由度气锤振动与电磁斜面振动是两种模拟产品三轴振动的振动技术。由于两种振动技术的机理不同,其对样品的振动影响也会有区别。本文研究讨论两种不同振动技术的不同特点,以及对不同产品的振动效果别,我们可以根据样品特点和测试需求,选择更合适的震动技术。 相似文献
19.
火焰原子吸收光谱法测定畜禽粪便中铜和锌 总被引:1,自引:1,他引:0
采用冻干法-全量酸消解-火焰原子吸收光谱法测定畜禽粪便中铜和锌,优化了试验条件.铜和锌分别在0 mg/L~3.00 mg/L和0 mg/L~1.00 mg/L范围内线性良好,检出限分别为6 mg/kg和2 mg/kg(按取0.5 g试样消解定容至50 mL计算),粪便试样测定的RSD分别为1.3%和3.7%,加标回收率分别为104%和107%. 相似文献
20.
Schröder P Scheer CE Diekmann F Stampfl A 《Environmental science and pollution research international》2007,14(2):114-122
Background, Aim and Scope
Numerous herbicides and xenobiotic organic pollutants are detoxified in plants to glutathione conjugates. Following this enzyme
catalyzed reaction, xenobiotic GS-conjugates are thought to be compartmentalized in the vacuole of plant cells. In the present
study, evidence is presented for long range transport of these conjugates in plants, rather than storage in the vacuole. To
our knowledge this is the first report about the unidirectional long range transport of xenobiotic conjugates in plants and
the exudation of a glutathione conjugate from the root tips. This could mean that plants possess an excretion system for unwanted
compounds which give them similar advantages as animals.
Materials and Methods:
Barley plants (Hordeum vulgare L. cv. Cherie) were grown in Petri dishes soaked with tap water in the greenhouse.
- Fluorescence Microscopy. Monobromo- and Monochlorobimane, two model xenobiotics that are conjugated rapidly in plant cells
with glutathione, hereby forming fluorescent metabolites, were used as markers for our experiments. Their transport in the
root could be followed sensitively with very good temporal and spatial resolution. Roots of barley seedlings were cut under
water and the end at which xenobiotics were applied was fixed in an aperture with a thin latex foil and transferred into a
drop of water on a cover slide. The cover slide was fixed in a measuring chamber on the stage of an inverse fluorescence microscope
(Zeiss Axiovert 100).
- Spectrometric enzyme assay. Glutathione S-transferase (GST) activity was determined in the protein extracts following established
methods. Aliquots of the enzyme extract were incubated with 1-chloro-2,4-dinitrobenzene (CDNB), or monochlorobimane. Controls
lacking enzyme or GSH were measured.
- Pitman chamber experiments. Ten days old barley plants or detached roots were inserted into special incubation chambers, either
complete with tips or decapitated, as well as 10 days old barley plants without root tips. Compartment A was filled with a
transport medium and GSH conjugate or L-cysteine conjugate. Compartments B and C contained sugar free media. Samples were
taken from the root tip containing compartment C and the amount of conjugate transported was determined spectro-photometrically.
Results:
The transport in roots is unidirectional towards the root tips and leads to exsudation of the conjugates at rates between
20 and 200 nmol min-1. The microscopic studies have been complemented by transport studies in small root chambers and spectroscopic
quantification of dinitrobenzene-conjugates. The latter experiments confirm the microscopic studies. Furthermore it was shown
that glutathione conjugates are transported at higher rates than cysteine conjugates, despite of their higher molecular weights.
This observation points to the existence of glutathione specific carriers and a specific role of glutathione in the root.
Discussion:
It can be assumed that long distance transport of glutathione conjugates within the plant proceeds like GSH or amino acid
transport in both, phloem and xylem. The high velocity of this translocation of the GS-X is indicative of an active transport.
For free glutathione, a rapid transport-system is essential because an accumulation of GSH in the root tip inhibits further
uptake of sulfur. Taking into account that all described MRP transporters and also the GSH plasmalemma ATPases have side activities
for glutathione derivatives and conjugates, co-transport of these xenobiotic metabolites seems credible.
- On the other hand, when GS-B was applied to the root tips from the outside, no significant uptake was observed. Thus it can
be concluded that only those conjugates can be transported in the xylem which are formed inside the root apex. Having left
the root once, there seems to be no return into the root vessels, probably because of a lack of inward directed transporters.
Conclusions:
Plants seem to possess the capability to store glutathione conjugates in the vacuole, but under certain conditions, these
metabolites might also undergo long range transport, predominantly into the plant root. The transport seems dependent on specific
carriers and is unidirectional, this means that xenobiotic conjugates from the rhizosphere are not taken up again. The exudation
of xenobiotic metabolites offers an opportunity to avoid the accumulation of such compounds in the plant.
Recommendations and Perspectives:
The role of glutathione and glutathione related metabolites in the rhizosphere has not been studied in any detail, and only
scattered data are available on interactions between the plant root and rhizosphere bacteria that encounter such conjugates.
The final fate of these compounds in the root zone has also not been addressed so far. It will be interesting to study effects
of the exuded metabolites on the biology of rhizosphere bacteria and fungi. 相似文献