大耳猬血液、尿无机离子等指标测定及肾脏水通道蛋白1、2的表达

测定了大耳猬血清及尿中多种无机离子和尿素氮等指标,并应用免疫组织化学方法观察了AQP1、AQP2在肾脏的表达.大耳猬血清钠、氯含量较高;而尿液中以钾、钠、氯及尿素氮含量较高.尿液中主要离子浓度高于血清,较为浓缩,尿素氮、钾排泄能力较强.AQP1免疫反应阳性表达于近曲小管上皮和髓袢细段,AQP2主要表达于集合管上皮细胞.因此,AQP1、AQP2可能在大耳猬肾脏水重吸收及尿液浓缩过程中具有重要作用.     

Effects of Heavy Metal Cations and Other Sulfhydryl Reagents on Brain Dopamine D1 Receptors: Evidence for Involvement of a Thiol Group in the Conformation of the Active Site

To investigate aspects of the biochemical nature of membrane-bound dopamine D1 receptors, rat striatal homogenates were pretreated with heavy metal cations and some other chemical agents, and their effects on D1 receptors were subsequently determined using a standard [3H](R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1-N-3- benzazepine([3H]SCH 23390) binding assay. Incubation of striatal membranes with as little as 1 microM Hg2+, 10 microM Cu2+, and 10 microM Cd2+ completely prevented specific [3H]SCH 23390 binding. The effect of Cu2+, 1.5 microM, was noncompetitive in nature, whereas 3-5 microM Cu2+ afforded mixed-type inhibition. The inhibitory effect of Cu2+ was fully reversed by dithiothreitol (0.1-1 mM). Cu2+ (2 microM) did not affect the affinity of cis-flupenthixol or clozapine for remaining [3H]SCH 23390 sites. A second series of cations, Co2+ (30 microM), Ni2+ (30 microM), Mn2+ (1 mM), Ca2+ (25 mM), and Ba2+ (20 mM), inhibited specific [3H]SCH 23390 binding by 50% at the concentrations indicated. The thiol alkylating reagent N-ethylmaleimide (NEM) (0.2 mM) reduced specific binding by 70%. The effect of NEM was completely prevented by coincubation with a D1 receptor saturating concentration of SCH 23390 (20 nM) or dopamine (10 microM). The results indicated that the dopamine D1 receptor is a thiol protein and that a thiol group is essential for the ligand binding.     

Simultaneous extraction of soil phytoavailable cadmium,copper, and lead by chelating resin membrane

Cadmium, copper, and lead were extracted from suspensions of contaminated soils using metal chelating exchange resin membranes. Nine soils with widely varying properties and Cd, Cu and Pb levels were tested. Soil suspensions made up with 4 g in 40 mL deionized water were equilibrated with 5 cm² Ca-saturated Chelex exchange resin membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs. Resin membrane extractable Cd, Cu and Pb of the soils were correlated with Cd, Cu, and Pb uptake by young wheat seedlings grown in these soils and compared with soil Cd, Cu, and Pb extracted by 0.1 M HCl, 0.01 M CaCl₂, and 0.005 M Diethylenetriamine pentaacetic acid (DTPA). The amounts of Cd, Cu and Pb extracted by the Ca-saturated Chelex membrane from all tested soils correlated well with those absorbed by young wheat seedlings. The Ca-saturated Chelex membrane extractable Cd, Cu and Pb of the soil had the strongest correlation with plant uptake Cd, Cu and Pb among the extraction methods we tested. It was demonstrated that the Ca-saturated Chelex membrane extraction is an appropriate method in simultaneously estimating Cd, Cu and Pb phytoavailability of soil and is applicable to a wide range of soils.     

重金属Zn2+胁迫下麦长管蚜的取食行为

为了探索重金属锌长期胁迫对麦长管蚜(Sitobion avenae)取食行为的变化影响,在模拟自然的实验室条件下,用不同浓度Zn~(2+)溶液浇灌土壤,通过土壤-小麦-蚜虫体系连续处理麦长管蚜15代,用EPG(刺探电位技术)对第1、5、10、15代成蚜的取食行为进行了监测。结果表明,第1代和第5代时,200 mg/kg的Zn~(2+)处理后np波和C波的总持续时间和数量显著低于对照,800mg/kg的Zn~(2+)使其显著增加。到第15代,高剂量的Zn~(2+)处理后np波和C波的总持续时间和数量均显著高于对照。涉及分泌唾液的E1波持续时间及涉及被动取食营养的E2波出现次数并未受到低剂量Zn~(2+)的显著影响,但高剂量的Zn~(2+)处理后单独E1波、伴随稳定E2的E1波总持续时间及E2波的数量均显著降低。麦长管蚜的取食行为会受到重金属锌的影响并且会在高剂量Zn~(2+)的胁迫条件下产生积累效应,而低剂量的Zn~(2+)则促进麦长管蚜对小麦的取食行为。针对重金属而言,此效应发生改变的关键浓度为400 mg/kg,蚜虫取食行为发生改变的关键世代为第5代和第10代。     

Permeability of Plant Young Root Endodermis to Cu Ions and Cu-Citrate Complexes in Corn and Soybean

The non-selective apoplastic passage of Cu and Cu-citrate complexes into the root stele of monocotyledonous corn and dicotyledonous soybean was investigated using an inorganic-salt-precipitation technique. Either Cu ions or Cu-citrate complexes were drawn into root through the apoplast from the root growth medium, and K₄[Fe(CN)₆] was subsequently perfused through xylem vessels or the entire root cross section. Based on microscopic identification of the reddish-brown precipitates of copper ferrocyanide in the cell walls of the xylem of corn and soybean roots, Cu²⁺ passed through the endodermal barrier into the xylem of both species. When the solution containing 200 μM CuSO₄ and 400 μM sodium citrate (containing 199.98 μM Cu-citrate, 0.02 μM Cu²⁺) was drawn via differential pressure gradients into the root xylem while being perfused with K₄[Fe(CN)₆] through the entire root cross-section, reddish-brown precipitates were observed in the walls of the stele of soybean, but not corn root. However, when a CuSO₄ solution containing 0.02 or 0.2 μM free Cu²⁺ was used, no reddish-brown precipitates were detected in the stele of either of the two plants. Results indicated that endodermis was permeable to Cu-citrate complexes in primary roots of soybean, but not corn. The permeability of the endodermal barrier to the Cu-citrate complex may vary between dicotyledonous and monocotyledonous plants, which has considerable implications for chelant-enhanced phytoextraction.     

Influence of sodium ion on heavy metal-induced inhibition of light-regulatd proton efflux and active carbon uptake in the cyanobacterium Anabaena flos-aquae

The light-induced proton efflux and active carbon uptake are inhibited by mercury and cadmium ions in Anabaena flos-aquae. The inhibitory effects of these heavy metal ions are reversed by 40 mM concentration of sodium. Here we report that light-induced proton efflux is sodium-dependent which leads to a characteristic enhancement in the rate of photosynthetic oxygen generation and carbon fixation. A low concentration (10 M) of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) significantly inhibited the rate of oxygen generation while 10 M carbonyl cyanide-m-chlorophenylhydrazone (CCCP) completely blocked the oxygen generation activity in the organism. The chlorophyll-a fluorescence yield indicates that little fluorescence quenching occurred in the absence of sodium ion. Increasing the extracellular sodium ion accelerated both the initial rate and the extent of fluorescence quenching. These results support the assumption that metal-induced inhibition of the photosynthetic machinery may be mediated by the movement of protons.     

Hill coefficient-based stochastic switch-like signal directly governs damage-recovery dynamics in freshwater fish in response to pulse copper

Growing evidence demonstrates that fluctuating metal stressors can have profound impact on the ecophysiological responses in aquatic species. However, how environmental stochasticity affects the complex damage-recovery dynamics in organisms remains difficult to predict. The objective of this paper was to investigate the stochastic behavior in the damage-recovery dynamics in tilapia in response to pulse waterborne copper (Cu). We developed a mathematical framework that allows discrimination between damage and recovery processes in tilapia exposed to designed pulse Cu scenarios. We built deterministic nonlinear models for the damage-recovery dynamics that produce response surfaces describing killing/recovery rate–Cu-pulse interval interactions. Here we showed that the stochastic switching behavior arose from competition among killing, recovery rates, and Cu pulse frequency. This competition resulted in an ultrasensitivity appeared in whole body, gills, muscle, liver, and kidney with Hill coefficients of ≥7, 4, 7, 5, and 5, respectively, at Cu 3 mg L⁻¹, dilution rate 0.05 h⁻¹, and pulse interval 72 h, indicating that a stochastic switch-like response was generated. We argue that the role of gill-associated Hill coefficient as a direct signal of the stochastic switch-like response in the damage-recovery dynamics in response to pulse metal stressor can serve as a sensitive indicator for risk detection in fluctuating environments. Our approach constitutes a general method to identify the stochastic switch-like response for aquatic species exposed to fluctuating metal stressors, which may help to predict and, eventually, expand our understanding of the damage-recovery dynamics. Finally, we implicate that Hill coefficient-based switch-like signal and its damage with hazard response can be linked in an information theoretic framework to handle environmental stochasticity.     

The vegetation of metalliferous and non-metalliferous grasslands in two former mine regions in Central Slovakia

We investigated the composition of the vegetation in two former mining regions in Central Slovakia: Banská Štiavnica with predominant Pb-Zn contamination and Staré Hory with a very high Cu content in the soil. Old heaps rich in heavy metals are covered with specific vegetation. On the Cu-rich spoil heaps, species-poor plant communities with prevailing Agrostis stolonifera, Avenella flexuosa, Acetosella vulgaris, Arabidopsis arenosa, Silene dioica, and S. vulgaris occur. Species such as Agrostis capillaris, Acetosella vulgaris, Arabidopsis arenosa, and Thlaspi caerulescens appear frequently on Pb-Zn mine wastes. Several differences in the vegetation structure were detected between the Pb-Zn and Cu mine heaps; higher amounts of vascular plants and fewer lichen species covered the Pb-Zn mine heaps. For the Cu mine heaps, on the contrary a small number of vascular species but a high number and coverage of lichen species, especially Ceratodon purpureus and Cladonia arbuscula subsp. mitis were typical. The non-metalliferous meadows in the vicinity of the mines showed uniform structure but a higher species diversity.     

高等植物金属抗性中有机酸的作用及其机理

植物的金属抗性可通过避性和耐性途径获得。具有螯合能力的有机酸在植物的金属外部排斥(避性)机制和内部耐受(耐性)机制中均具有重要作用。在金属的外部排斥过程中,植物根系分泌有机酸,与金属离子形成稳定的复合体,降低土壤金属的移动性,达到体外解毒的目的。超积累型植物的内部耐受机制主要体现在,有机酸可与金属元素发生螯合作用,将离子态的金属转变成低毒或无毒的螯合态,从而降低细胞内金属离子的毒害效应。有机酸的种类受植物种类、金属类型等因素的影响。     

Salt sensitivity in chickpea (Cicer arietinum L.): ions in reproductive tissues and yield components in contrasting genotypes

The reproductive phase in chickpea (Cicer arietinum L.) is affected by salinity, but little is known about the underlying cause. We investigated whether high concentrations of Na⁺ and Cl^– in the reproductive structures influence reproductive processes. Chickpea genotypes contrasting in tolerance were subjected to 0, 35 or 50 mm NaCl applied to soil in pots. Flower production and abortion, pod number, percentage of empty pods, seed number and size were evaluated. The concentrations of Na⁺, K⁺ and Cl^– were measured in various plant tissues and, using X‐ray microanalysis, in specific cells of developing reproductive structures. Genotypic variation in reproductive success measured as seed yield in saline conditions was associated with better maintenance of flower production and higher numbers of filled pods (and thus seed number), whereas seed size decreased in all genotypes. Despite the variation in reproductive success, the accumulation of Na⁺ and Cl^– in the early reproductive tissues of developing pods did not differ between a tolerant (Genesis836) and a sensitive (Rupali) genotype. Similarly, salinity tolerance was not associated with the accumulation of salt ions in leaves at the time of reproduction or in seeds at maturity.