Ethyl mercury induces Ca2+ uptake through the P2×7 receptor in a mouse cerebellar microglia cell line

Many observations are reported that organic mercury compounds are involved in increasing intracellular Ca²⁺ levels. However, the issue of which substances on the cell membrane participate in the Ca²⁺ uptake that is induced by ethyl mercury is unclear. The findings of this study suggest that the P2X receptor participates in this process. The uptake of Ca²⁺ by C8-B4 cells was induced in the presence of ethyl mercury. Ca channels in the cell membrane were not affected in this process. In contrast, pretreatment with suramin, an antagonist of the P2X receptor, inhibited the Ca²⁺ uptake induced by ethyl mercury, and also brilliant blue G, a nonselective antagonist of P2×4, P2×5, and P2×7 receptors. In addition, A438079 and A740003, selective antagonists of P2×7 receptor, reduced Ca²⁺ uptake, while 5-BDBD, a selective antagonist of P2×4 receptor, did not. Furthermore, the mRNAs of both the P2×4 and P2×7 receptors were expressed in the presence of ethyl mercury, but the P2×5 receptor mRNA was not. These findings suggest that ethyl mercury may induce Ca²⁺ uptake through the P2×7 receptor of the cell membrane.     

Distribution of metallic compounds between plants and soils∗

Distribution of metallic constituents between soil and aerial parts of wild plants has been discussed by using relative ionic impulsions, i/I, defined as functions of concentrations of metallics ions, being i = [M]^1/2M, z_M the oxidation state of considered metal and I = S i the summation of contribution of metals. For this calculation metals were divided into two groups leading to ^I macro (K, Na, Ca, Mg, and Mn, elements accumulated in aerial parts) and to I _Micro (Fe, Cu, Zn, Co and contaminants accumulated in roots). Relative ionic impulsions may be attributed to an electric potential gradient and show if an active or passive uptake is happening. For macroelements linear relationships were obtained for Mg‐K (global active uptake) and Na‐Mn‐Ca (global passive uptake) with inverse slopes. Passive ions seem to be used as counter ions for helping active assimilation. Calculated potential gradient was close to 20 mV. The same situation was found for microelements and pollutants, where Fe is taken passively helping assimilation of the rest (Cu, Zn, Co, Cd, Pb, Ni and Cr) with a potential gradient close to 13 mV. Influences of other ecological segments (rainfall, dry deposition, airborne dust and irrigation), as well as additions for amending contaminated soils are finally discussed.     

The effects of application of agricultural wastes to firing range soil on metal accumulation in Ipomoea aquatica and soil metal bioavailability

The immobilisation of heavy metals in the soil of a 25-year-old active firing range using durian (Durio zibethinus L.) tree sawdust (DTS), coconut coir (CC) and oil palm empty fruit bunch (EFB) was investigated. The immobilisation effects were evaluated in terms of metal accumulation in water spinach (Ipomoea aquatica) and soil metal bioavailability. A pot experiment was conducted by amending the firing range soil with DTS, CC and EFB at application rates of 0%, 1% and 3% (w/w), respectively. All amendments increased the biomass yield and reduced the uptake of heavy metals in the plant tissue. Zn had the highest values of Bioconcentration Factor (BCF: 0.301–0.865) and Translocation Factor (TF: 1.056–1.883). Pb was the least-accumulated and transported metal in the plant tissues, with the BCF and TF values of 0.019–0.048 and 0.038–0.116, respectively. The bioavailable fraction of heavy metals in the firing range soil decreased following the application of the three agricultural wastes studied. DTS, CC and EFB did not cause toxicity symptoms in the water spinach over the pot experiment. Therefore, DTS, CC and EFB are considered promising immobilising agents for the remediation of metal-contaminated land.     

Pollution profiles and physicochemical parameters in old uncontrolled landfills

The long-term effectiveness of the geological barrier beneath municipal-waste landfills is a critical issue for soil and groundwater protection. This study examines natural clayey soils directly in contact with the waste deposited in three landfills over 12 years old in Spain. Several physicochemical and geological parameters were measured as a function of depth. Electrical conductivity (EC), water-soluble organic carbon (WSOC), Cl⁻, NH₄⁺, Na⁺ and exchangeable NH₄⁺ and Na⁺ were used as parameters to measure the penetration of landfill leachate pollution. Mineralogy, specific surface area and cationic-exchange capacities were analyzed to characterize the materials under the landfills. A principal component analysis, combined with a Varimax rotation, was applied to the data to determine patterns of association between samples and variables not evident upon initial inspection. The main factors explaining the variation in the data are related to waste composition and local geology. Although leachates have been in contact with clays for long time periods (13-24 years), WSOC and EC fronts are attenuated at depths of 0.2-1.5 m within the clay layer. Taking into account this depth of the clayey materials, these natural substrata (>45% illite-smectite-type sheet silicates) are suitable for confining leachate pollution and for complying with European legislation. This paper outlines the relevant differences in the clayey materials of the three landfills in which a diffusive flux attenuation capacity (A_c) is defined as a function (1) of the rate of decrease of the parameters per meter of material, (2) of the age and area of the landfill and (3) of the quantity and quality of the wastes.     

沼泽红假单胞菌phbC-hupL双突变株构建及产氢测定

利用湖底淤泥分离的沼泽红假单胞菌(Rhodopseudomonas palustris)CQU01和该菌株的吸氢酶基因hupL缺失菌株CQU012作为出发菌株,分别构建聚羟基丁酸酯合成酶基因phbC单突变株及聚羟基丁酸酯合成酶基因phbC与吸氢酶基因hupL双突变株,以提高其在光照培养条件下的产氢量.以同源重组双交换方法构建含有Em抗性基因的自杀载体,通过接合转移转化R. palustris CQU01菌株,经PCR扩增以及测序验证,成功获得了沼泽红假单胞菌phbC单突变株R. palustris CQU013及phbC-hupL双突变株R. palustris CQU014.相同条件下测定突变菌株与野生菌株的生长和产氢特性,结果显示,突变菌株生长曲线与野生菌株有明显差异,两株突变菌株的产氢量分别是原始菌株的1.31和1.76倍,达到454mL/L和604mL/L.双突变菌株产氢能力较phbC基因和hupL基因单突变菌株的产氢能力有明显提高,说明phbC和hupL基因对菌株R. palustris 的产氢代谢有着显著的影响.     

7个柳树无性系在Cu/Zn污染土壤中的生长及对Cu/Zn的吸收

通过盆栽试验来评价7个柳树无性系(旱柳?杞柳和金丝柳)修复Cu/Zn污染土壤或矿砂的潜力.研究了7个无性系在2种污染介质中的生长,叶绿素含量?根系形态及其对Cu、Zn的吸收转移.结果表明,150d后,7个柳树无性系在污染介质中都能生长,其中旱柳和金丝柳生长较好,其他无性系生长受到明显抑制.各无性系叶片出现黄化现象,叶绿素相对含量降低.根系发育受到一定程度的抑制.各无性系对Cu的积累主要在地下部,而对Zn的积累主要在地上部,特别是在叶片中.7个无性系在铜土中更容易积累重金属.各无性系生物富集系数(BCF)Cu.Cu的转移系数(TF)值均<1,Zn的TF值在1.36~2.49之间.旱10?旱34和金丝柳对Cu和Zn有较强的耐性和一定积累能力,适合在尾矿区造林和修复.     

樟树对14CO2的吸收和积累

为了探明14CO2在环境中的行为,采用同位素示踪技术研究了樟树对14CO2的吸收和积累动态,并探讨了樟树作为监测大气14CO2污染指示植物的可能性和优越性.结果表明,通过叶片光合作用从空气中吸收的14CO2会在樟树叶片中积累,检测到的14C比活度数值较大,表明空气中的14CO2易于通过叶片的光合作用而进入樟树叶片组织中;在污染前期14CO2主要被新叶组织中吸收,后期主要积累在老叶中,反映出新叶对空气14CO2污染比较敏感,而老叶积累效应明显.樟树叶片的这一特性可用于监测大气14CO2污染.     

Metabolic and Environmental Control on Methane Emission from Soils: Mechanistic Studies of Mesotrophic Fen in West Siberia

The biological mechanisms regulating methane emission fromnatural wetlands are the focus of this article. A novel techniqueprovides estimates of the distribution of CH₄ sources withinan undisturbed soil profile by recording the transient gasdynamics after soil enclosure by deep (50 cm) chamber. Thecombined use of conventional surface and soil chambers across a200-m fen transect allowed us to relate the observed methaneemission to its instant generation and uptake. Surprisingly, themethane generation was relatively constant (9–12 mg CH₄-C hr^-1 m^-2) and highly variable net emission (0.2–20 mg CH₄-C hr^-1 m^-2) was closely correlated (r = –0.809)with methane uptake. In laboratory incubations, CH₄ uptakefollowed Michaelis-Menten kinetics. Added chloride and nitrateirrespective of the cation's nature suppressed uptake as a strongnoncompetitive inhibitors (K _i 0.5 mM). The methaneformation turned out to be unstable and under anaerobicincubation, the formation of CH₄, CO₂ andH₂displayed sustained weekly oscillations. We conclude that effectsof environmental factors alone are not sufficient topredict the variation in emission, which depends also on metabolic control of respective soil organisms. The multitude ofsuch controls is dependent on diversity of respective soilorganisms and could be grouped into a limited number ofcategories considerably simplifying large-scale simulations.     

轮叶黑藻和穗花狐尾藻对铜的吸收机制研究

应用室内模拟试验,通过对铜(Cu)的短期吸收动力学、各亚细胞组分吸收动力学以及Cu的释放研究,探讨了两种沉水植物轮叶黑藻[Hydrilla verticillata(L.f.)Royle]和穗花狐尾藻(Myriophyllum spicatum L.)对Cu的吸收机制.结果表明:①轮叶黑藻和穗花狐尾藻均对Cu具有较高的吸收速率,且两种植物最高吸收速率差异不显著[Vmax(DW)为2μmol·(g·min)-1,P>0.05];②在2μmol·L-1Cu溶液中暴露不同时间(0~96 h),两种沉水植物叶片和茎中各亚细胞组分的Cu含量均迅速增加并约在12 h后达到平衡.各时间处理下,两种植物叶片富集的Cu含量均显著高于茎(P<0.05),并且叶片中的Cu均主要分布在细胞壁(>60%),其次是可溶部分和细胞器;③两种植物相比,黑藻叶片细胞壁中富集的Cu含量显著高于狐尾藻,而细胞内富集的Cu含量差异不显著.轮叶黑藻对Cu的富集和释放能力均高于穗花狐尾藻.     

Alginate modifies the physiological impact of CeO2 nanoparticles in corn seedlings cultivated in soil

Alginates are naturally occurring components of organic matter in natural soil whose effects on nanoparticle （NP） toxicity to plants is not well understood. In the present study, corn plants were grown for one month in soil spiked with 400 mg/kg CeO2 NPs with various alginate concentrations. After one month of growth in the NPs impacted soil, plants were harvested and analyzed for Ce and mineral element concentrations. Chlorophyll concentration and heat shock protein 70, used as biomarkers for oxidative stress, were also evaluated. Results showed that, compared to CeO2 NPs treatment, alginate at 10, 50, and 100 mg/kg increased Ce concentration in roots by approximately 46%, 38%, and 29% and by 115%, 45%, and 56% in shoots, respectively. CeO 2 NPs without alginate increased Mn accumulation in roots by 34% compared to control. CeO2 NPs with low and medium alginate increased Mn by ca. 92% respect to NPs without alginate and by ca. 155% respect to control. CeO2 NPs without/with alginate significantly increased accumulation of Fe and Al in roots. In addition, alginate at 50 mg/kg increased Zn accumulation in roots by 52% compared to control. In shoots, K increased at all NP treatments but the accumulation of other elements was not affected. Alginate enlarged the impact of CeO2 NPs to corn plants by reducing chlorophyll a content and triggering overexpression of heat shock protein 70.