Alzheimer disease: mercury as pathogenetic factor and apolipoprotein E as a moderator

The etiology of most cases of Alzheimer's disease (AD) is as yet unknown. Epidemiological studies suggest that environmental factors may be involved beside genetic risk factors. Some studies have shown higher mercury concentrations in brains of deceased and in blood of living patients with Alzheimer's disease. Experimental studies have found that even smallest amounts of mercury but no other metals in low concentrations were able to cause all nerve cell changes, which are typical for Alzheimer's disease. The most important genetic risk factor for sporadic Alzheimer's disease is the presence of the apolipoprotein Ee4 allele whereas the apolipoprotein Ee2 allele reduces the risk of developing Alzheimer's disease. Some investigators have suggested that apolipoprotein Ee4 has a reduced ability to bind metals like mercury and therefore explain the higher risk for Alzheimer's disease. Therapeutic approaches embrace pharmaceuticals which bind metals in the brain of patients with Alzheimer's disease. In sum, both the findings from epidemiological and demographical studies, the frequency of amalgam application in industrialized countries, clinical studies, experimental studies and the dental state of AD patients in comparison to controls suggest a decisive role for inorganic mercury in the etiology of AD.     

Ecological Risk Assessment of Arsenic and Metals in Surface Sediments from Estuarine and Coastal Areas of the Southern Bohai Sea,China

Distribution and magnitude of arsenic and metals in surface sediments collected from the coastal and estuarine areas of the southern Bohai Sea, China, were investigated. Sediments from the estuarine and coastal areas of the Jie and Xiaoqing Rivers contained highest concentrations of arsenic, cadmium, copper, mercury, and zinc. Mean concentrations of Cu, Zn, Cr, Pb, and Cd were higher than background concentrations determined for the areas. The magnitude of both enrichment factors (EF) and geoaccumulation indices (I_geo) suggested that pollution with As and metals was occurring along estuarine and coastal areas of the southern Bohai Sea. Risk analysis also suggested that concentrations of As and metals were sufficiently elevated as to cause adverse biological effects in the study area. According to the ecological risk index (RI) values, the upstream of the Jie River has a very high ecological risk for the waterbody. The data provided in this study are considered crucial for controlling and remediation of As and metals’ pollution of the southern Bohai Sea.     

海洋沉积物中重金属对底栖无脊椎动物的生物有效性

海洋沉积物是重金属的重要贮库,而海洋底栖无脊椎动物主要从沉积物中摄取重金属,这些被摄取的重金属能够通过食物链进行传递,进而影响到人类健康。本文总结了近些年来在海洋沉积物中重金属对底栖无脊椎动物生物有效性方面的研究进展,包括海洋底栖无脊椎动物对重金属的吸收途径、沉积物地球化学性质和底栖无脊椎动物生理等生物因素对沉积物中重金属生物有效性的影响。在此基础上,展望了未来研究重点,主要包括近海富营养化对沉积物中重金属生物有效性的影响,海洋底栖无脊椎动物消化道中的物理消化过程对沉积物中重金属生物有效性的影响,海洋底栖无脊椎动物整个生活史过程中沉积物中重金属生物有效性的变化等。     

Bioaccumulation of trace metals by the live macroalga Gracilaria lemaneiformis

The macroalga Gracilaria lemaneiformis is an important and commercially valuable renewable resource. It is distributed widely in shallow marine waters but grows mostly on tropical or subtropical coasts. We investigated the accumulation of Cd, Cu, and Pb by live G. lemaneiformis under low concentrations. There was a positive correlation between the organisms’ metal concentrations and exposure concentrations. When exposed to both Cu and Cd, the concentrations of Cu and Cd in G. lemaneiformis were higher than those exposed to solutions of Cu and Cd alone. However, the concentrations of heavy metals in G. lemaneiformis were not markedly different (p?<?0.05) between the treatment groups and the control groups. We analyzed the results with nonlinear curve fitting and employed a two-compartment model to study the accumulation kinetics of heavy metals by G. lemaneiformis. The uptake rate constants and bioconcentration factors (BCFs) of the metals decreased with increased exposure concentration. The theoretical equilibrium concentrations increased significantly with the exposure concentrations. Our results suggested that G. lemaneiformis obviously accumulated heavy metals from seawater. As an important resource for food and pharmaceuticals, G. lemaneiformis should be cultivated in clear seawater.     

Transition metals: A double edge sward in ROS generation and signaling

Transition metals such as Iron (Fe) and Copper (Cu) are essential for plant cell development. At the same time, due their capability to generate hydroxyl radicals they can be potentially toxic to plant metabolism. Recent works on hydroxyl-radical activation of ion transporters suggest that hydroxyl radicals generated by transition metals could play an important role in plant growth and adaptation to imbalanced environments. In this mini-review, the relation between transition metals uptake and utilization and oxidative stress-activated ion transport in plant cells is analyzed, and a new model depicting both apoplastic and cytosolic mode of ROS signaling to plasma membrane transporters is suggested.     

土壤中水溶性有机质及其对重金属化学与生物行为的影响

土壤水溶性有机质是陆地生态系统和水生生态系统中一种重要的、很活跃的化学组分,已成为环境科学、土壤学和生态学等学科的研究热点．土壤DOM对重金属化学与生物行为有重要影响。但其机理尚不清楚．文中从土壤性质、环境条件、人为因素等方面阐述了土壤DOM产生及影响因素,总结评述了DOM对重金属化学行为和生物有效性的影响,将DOM对重金属的影响机制归纳为络合机制、竞争吸附机制、酸碱缓冲机制．在此基础上,提出了DOM研究存在的问题及其展望．     

Zinc regulates the function and expression of the iron transporters DMT1 and IREG1 in human intestinal Caco-2 cells.

Trace metals influence the absorption of each other from the diet and it has been suggested that the divalent metal transporter (DMT1) represents a common uptake pathway for these important micronutrients. However, compelling evidence from our laboratory suggests that DMT1 is predominantly an iron transporter, with lower affinity for other metals. Several studies have shown that increasing dietary iron downregulates DMT1. Interestingly, our current data indicate that zinc upregulates DMT1 protein and mRNA expression and also pH-dependent iron uptake. Transepithelial flux of iron was also increased and was associated with a rise in IREG1 mRNA expression.     

大型真菌对重金属的生物富集作用及生态修复

大型真菌是一类重要的环境生物资源,对人类的生存具有重要作用.与绿色植物相比,大型真菌能够积累高浓度的Pb、Cd和Hg等重金属.本文论述了大型真菌对重金属的生物富集作用以及利用大型真菌进行重金属生态修复的优势,指出大型真菌种类、生态类型、富集重金属的生物学特性及其遗传潜能、大型真菌菌丝体和子实体的形态、部位、寿命以及结实间隔和环境因子等是影响大型真菌吸收和积累重金属的主要因素.筛选富集重金属功能强大、易于人工栽培、环境适应性强、便于后处理的大型真菌是今后研究的重要方向.     

Oxidative damage in liver after perinatal intoxication with lead and/or cadmium

Lead acetate (300 mg Pb/L) and/or cadmium acetate (10mg Cd/L) in blood and liver were administrated as drinking water to pregnant Wistar rats from day 1 of pregnancy to parturition (day 0) or until weaning (day 21), to investigate the toxic effects in blood and in the liver. Both metals produced mycrocitic anaemia in the pups as well as oxidative damage in the liver, as suggested by the significant increase in TBARS production and the high catalase activity. Moreover, intense alkaline and acid phosphatase activity, used as biomarkers of liver adaptation to damaging factors, was observed. In addition, the toxikinetics are different for Pb and Cd: while Cd is a hepatotoxic from day 0, Pb is not until day 21. Finally, simultaneous perinatal administration of both metals seems to protect, at least, in the liver TBARS production against the toxicity produced by Cd or Pb separately.     

Trace metals in waters.

The topic of this paper is extremely broad, and to allow more useful discussion, emphasis is placed on trace (less than 1 mg/l) metals in fresh surface waters and in drinking waters. An attempt is made to give a broad overview of current knowledge, problems and research with particular reference to the following: (1) metals of interest, current standards of water quality relevant to health, and concentrations of metals in waters; (2) sources of, and other factors affecting, the concentrations of metals; (3) general problems in the measurement of metal concentrations; (4) important research topics.     

Phosphatase-mediated heavy metal accumulation by a Citrobacter sp. and related enterobacteria

Abstract A Citrobacter sp. was reported previously to accumulate heavy metals as cell-bound heavy metal phosphates. Metal uptake is mediated by the activity of a periplasmic acid-type phosphatase that liberates inorganic phosphate to provide the precipitant ligand for heavy metals presented to the cells. Amino acid sequencing of peptide fragments of the purified enzyme revealed significant homology to the phoN product (acid phosphatase) of some other enterobacteria. These organisms, together with Klebsiella pneumoniae , previously reported to produce acid phosphatase, were tested for their ability to remove uranium and lanthanum from challenge solutions supplemented with phosphatase substrate. The coupling of phosphate liberation to metal bioaccumulation was limited to the metal accumulating Citrobacter sp.; therefore the participation of species-specific additional factors in metal bioaccumulation was suggested.     

DnaJ—like基因在不同环境胁迫下的表达研究

ＰｖＳＲ６（Ｐｈａｓｅｏｌｕｓ ｖｕｌｇａｒｉｓ ｓｔｒｅｓｓ－ｒｅｌａｔｅｄ）基因编码一种菜豆ＤｎａＪ－ｌｉｋｅ蛋白。Ｎｏｒｔｈ－ｅｒｎ ｂｌｏｔ结果表明：ＰｖＳＲ６基因在未处理的菜豆叶片中表达较少,重金属（Ｈｇ＾２＋和Ｃｄ＾２＋）、机械损伤、ＵＶ、高温和水杨酸等环境胁迫能强烈地促进其基因的转录,推测ＤｎａＪ－ｌｉｋｅ蛋白在保护细胞膜和酶蛋白的结构和功能及提高植物的抗逆性方面有重要作用。     

The use of flocculating brewer's yeast for Cr(III) and Pb(II) removal from residual wastewaters

The use of inexpensive biosorbents to sequester heavy metals from aqueous solutions, is one of the most promising technologies being developed to remove these toxic contaminants from wastewaters. Considering this challenge, the viability of Cr(III) and Pb(II) removal from aqueous solutions using a flocculating brewer's yeast residual biomass from a Portuguese brewing industry was studied. The influence of physicochemical factors such as medium pH, biomass concentration and the presence of a co-ion was characterised. Metal uptake kinetics and equilibrium were also analysed, considering different incubation temperatures. For both metals, uptake increased with medium pH, being maximal at 5.0. Optimal biomass concentration for the biosorption process was determined to be 4.5?g dry weight/l. In chromium and lead mixture solutions, competition for yeast binding sites was observed between the two metals, this competition being pH dependent. Yeast biomass showed higher selectivity and uptake capacity to lead. Chromium uptake kinetic was characterised as having a rapid initial step, followed by a slower one. Langmuir model describes well chromium uptake equilibrium. Lead uptake kinetics suggested the presence of mechanisms other than biosorption, possibly including its precipitation.     

Effect of chronic non-lethal doses of non-metals and metals on hepatic metallothionein in Channa punctatus (Bloch).

Compared to non-metal toxicants (ammonia, 1.56 ppm; and phenol, 10 ppm), the metals (CdCl2, 30 ppm; HgCl2, 16.7 ppb; and ZnCl2, 6 ppm) significantly induced hepatic metallothionein (MT) concentrations in C. punctatus, exposed independently to non-lethal doses of these toxicants for 28 days. It is suggested that hepatic MT serves as a metal-sequestering protein and is involved in the detoxication of metals only and ensures protection from toxic chemicals in ambience.     

Temporal variations in metal enrichment in suspended particulate matter during rainfall events in a rural stream

We studied enrichment of heavy metals (V, Zn, Cr, Ni, Cu, Pb, As, Sb, and Cd) in a rural stream of the Kuji River basin in central Japan in suspended particulate matter, and associated transport flux during two rainfall events (in November 2003 and in April 2008). The concentration of heavy metals in suspended particulate matter (SPM) exhibited a distinctive temporal variation, wherein the concentrations decreased with increasing water discharge and then increased as the discharge decreased. Concentration of dissolved metal forms showed a slight increase with scatters around the flow rate peak. Enrichment factors for those metals in the SPM decreased sharply as the flow rate increased, making an obvious concave shaped curve (the November 2003 rainfall event). The metal enrichment factors under low flow conditions had a similarity to those found in atmospheric deposits at a foot of the Kuji River basin, suggesting atmospheric source would contribute to enriching the SPM with those metals in part. Mineralogical analyses and carbon content analysis (the April 2008 rainfall event) of the SPM suggests the SPM matrix became more lithological as the flow rate increased. The changes observed in the matrix are thought to be directly related to progressive changes in metal enrichment within the SPM. Concerning the transport phase of several heavy metals, a dynamic change in transport phase partitioning within a rainfall event was suggested. The present enrichment factor study and the SPM matrix characterization implied the partitioning change is due to an increase in lithologic solids during high flow conditions.     

Distribution,Fraction, and Ecological Assessment of Heavy Metals in Sediment-Plant System in Mangrove Forest,South China Sea

Overlying water, sediment, rhizosphere sediment and mangrove seedlings in the Futian mangrove forest were analyzed for heavy metals. The results showed that mangrove plant acidified sediment and increased organic matter contents. Except for chromium (Cr), nickel (Ni) and copper (Cu) in Aegiceras corniculatum sediment, heavy metals in all sediments were higher than in overlying water, rhizosphere sediment and mangrove root. Heavy metals in Avicennia marina sediments were higher than other sediments. The lower heavy metal biological concentration factors (BCFs) and translocation factors (TFs) indicated that mangrove plant adopted exclusion strategy. The geo-accumulation index, potential ecological risk index and risk assessment code (RAC) demonstrated that heavy metals have posed a considerable ecological risk, especially for cadmium (Cd). Heavy metals (Cr, Ni, Cu and Cd) mainly existed in the reducible fractions. These findings provide actual heavy metal accumulations in sediment-plant ecosystems in mangrove forest, being important in designing the long-term management and conservation policies for managers of mangrove forest.     

铜锈环棱螺对沉积物中重金属的生物积累及其与重金属赋存形态的关系

以铜锈环棱螺（Bellamya aeruginosa）为测试生物,采用28 d沉积物生物积累试验研究铜锈环棱螺对污染河流沉积物中重金属的生物积累,并探讨其与重金属赋存形态的关系.结果表明：铜锈环棱螺肝胰脏对Cd、Pb、Cu、Cr、Zn和Mn均具有较强的积累作用.不同重金属的积累量存在较大差别,Zn的积累量最多,占重金属总积累量的84.32%±4.36%,其次为Cu,占7.67%±2.84%;Pb、Cr和Mn的比例相对较少,分别为3.62%±1.84%、2.22%±1.03%和1.33%±0.15%;Cd所占比例最少,为0.83%±0.53%.肝胰脏中重金属元素之间的相关性均不显著.肝胰脏金属污染指数与沉积物污染综合指数具有显著的正相关关系,铜锈环棱螺可以作为沉积物重金属污染的监测生物.不同沉积物Cd、Cr、Zn和Mn的生物-沉积物积累因子（BSAF）具有较大的差异,Cu和Pb的BSAF比较稳定.Cd的生物积累与沉积物中Cd的可交换的与酸可溶态及可氧化态显著相关;Pb的生物积累与Pb的可还原态显著相关;Cu的生物积累与Cu的可氧化态显著相关;Mn的生物积累与Mn的可交换的与酸可溶态和可还原态显著相关;Cr和Mn的生物积累与其不同形态和总量均不相关.BSAF不宜作为衡量铜锈环棱螺对沉积物中重金属生物积累能力的指标.     

Comparisons of AM fungal spore communities with the same hosts but different soil chemistries over local and geographic scales

Arbuscular mycorrhizal (AM) fungi are ubiquitous and ecologically important microbes in grasslands. Both the host plant species and soil properties have been suggested as potentially important factors structuring AM fungal communities based on studies within local field sites. However, characterizations of the communities in relation to both host plant identity and soil properties in natural plant communities across both local and broader geographic scales are rare. We examined the AM fungal spore communities associated with the same C₄ grasses in two Eastern serpentine grasslands, where soils have elevated heavy metals, and two Iowa tallgrass prairie sites. We compared AM fungal spore communities among host plants within each site, looked for correlations between fungal communities and local soil properties, and then compared communities among sites. Spore communities did not vary with host plant species or correlate with local soil chemical properties at any site. They did not differ between the two serpentine sites or between the two prairie sites, despite geographic separation, but they did differ between serpentine and prairie. Soil characteristics are suggested as a driving force because spore communities were strongly correlated with soil properties when data from all four sites are considered, but climatic differences might also play a role.     

Source identification and availability of heavy metals in peri-urban vegetable soils: A case study from China

The purpose of this study was to investigate the total and available concentrations of Pb, Cr, Cu, Ni, and Zn in the vegetable soils from the outskirts of a heavy industry city, Northeast China, and to assess the sources of heavy metals and their availability. The average concentrations of Pb, Cu, and Zn were significantly higher than their background values of Changchun topsoil. Principal component analysis, cluster analysis, and geostatistical analysis results suggested that Pb, Cu, and Zn were consistently from anthropogenic sources, while Cr and Ni were from natural sources with low concentrations. Kriging results showed that several hotspots of high metal concentration were identified by the geochemical maps and caused by different environmental factors. Although the available (ethylene-diamine-tetraacetic acid-extractable) fractions showed much lower values than total concentrations of metals, Pb and Cu had relatively high AR^a (average availability ratio of metals) values. Our findings show that most of the studied metals had accumulated to some extent in vegetable soils and several hotspots of high metal concentration appeared at the peri-urban of Changchun. The concentrations of some metals in peri-urban vegetable soils have been largely affected by anthropogenic activities. Appropriate measures should be taken to effectively control heavy metal levels in vegetable soils and thus protect human health.     

重金属污染土壤植物修复基本原理及强化措施探讨

阐述了植物修复的基本概念及主要作用方式 ,并从土壤中重金属存在形态 ,植物对重金属吸收、排泄和积累以及植物生物学特性与植物修复的关系等方面讨论了重金属污染土壤植物修复的基本原理及局限性和限制性因素 ,从超富集植物性能强化和技术强化两方面探讨了植物修复的强化措施 ,并指出与现代化农业技术相结合是植物修复重金属污染土壤大规模商业应用的一条捷径