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PubMed2004

Metal-responsive transcription factor (MTF-1) and heavy metal stress response in Drosophila and mammalian cells: a functional comparison.

The zinc finger transcription factor MTF-1 (metal-responsive transcription factor-1) is conserved from insects to vertebrates. Its major role in both organisms is to control the transcription of genes involved in the homeostasis and detoxification of heavy metal ions such as Cu2+, Zn2+ and Cd2+. In mammals, MTF-1 serves at least two additional roles. First, targeted disruption of the MTF-1 gene results in death at embryonic day 14 due to liver degeneration, revealing a stage-specific developmental role. Second, under hypoxic-anoxic stress, MTF-1 helps to activate the transcription of the gene placental growth factor (PIGF), an angiogenic protein. Recently we characterized dMTF-1, the Drosophila homolog of mammalian MTF-1. Here we present a series of studies to compare the metal response in mammals and insects, which reveal common features but also differences. A human MTF-1 transgene can restore to a large extent metal tolerance to flies lacking their own MTF-1 gene, both at low and high copper concentrations. Likewise, Drosophila MTF-1 can substitute for human MTF-1 in mammalian cell culture, although both the basal and the metal-induced transcript levels are lower. Finally, a clear difference was revealed in the response to mercury, a highly toxic heavy metal: metallothionein-type promoters respond poorly, if at all, to Hg2+ in mammalian cells but strongly in Drosophila, and this response is completely dependent on dMTF-1.

Animals↗

PubMed2000

Inhibitory effects of heavy metals on transcription factor Sp1.

Heavy metals are expected to affect the biological activity of various metal-containing proteins, including transcriptional regulators. We studied the effects of several heavy metal ions on the DNA-binding activity of a Zn-finger transcription factor, Sp1. With respect to both DNA elements through which Sp1 acts positively and negatively, Cd2+ inhibited DNA-binding of Sp1 at 20 microM or higher, while the toxic effect of Zn2+ was obvious only at more than 200 microM. Inhibition was also apparent for Cu2+ but less remarkable for Hg2+. The inhibition by Cd2+ was relieved by the addition of Zn2+ at much lower concentrations than that of Cd2+. These results suggest that the toxic potential of heavy metals could be largely influenced by the intracellular Zn2+ concentration.

Dose-Response Relationship, Drug↗

PubMed2002

[Interaction between microorganisms and heavy metals and its application].

Interactions between microorganisms and heavy metals were expatriated in many ways. Because of their resistance and detoxification to heavy metals, microorganisms are able to leach, absorb and transform heavy metals, which has been actively applied to extract heavy metals from low-rate ore in mine exploitation. Although heavy metals are toxic to microorganisms population and harmful to its processes, some special microorganisms have been applied to the treatment of industrial waste materials and the remediation of soils polluted by heavy metals. The application of microbiological biomass and activity to evaluating the pollution situation and ecological risk of heavy metals in environment media is also significant.

Bacteria↗

PubMed1998

The relationship between the quantity of heavy metal and PAHs in fly ash.

Heavy metal and polycyclic aromatic hydrocarbons (PAHs) in flue gas have received considerable attention in recent years due to their mutagenic or carcinogenic properties. The present study is carried out to investigate the influence of the quantity of heavy metals on PAHs formation in fly ash. A fluidized bed incinerator was used in this experiment to obtain fly ash of chemical similarity by incinerating various compositions of waste. The obtained fly ash, both with and without heavy metal, were used to adsorb the PAHs in the flue gas and to investigate the formation of PAHs in fly ash. The results indicate that carbon and heavy metals most greatly influence the formation of PAHs in the fly ash. Carbon is absorptive; heavy metals encourage not only absorption of PAHs but also catalyze PAHs formation.

Air Pollutants, Occupational↗

PubMed2006

Study on risk management of heavy metals for reuse of biosolids.

The behaviour of heavy metals was investigated at 22 wastewater treatment plants (WWTPs). In addition, the survey of heavy metal balance was conducted in detail at one WWTP. For the measurement, 22 types of heavy metals were selected from the chemical materials of pollutant release and transfer register (PRTR). There were some heavy metals, which were detected not in wastewater but in dewatered sludge. By means of the detailed survey at one WWTP, 60 to 80% of some heavy metals, such as B, Mn, Co, Ni and Mo, were discharged with treated water. According to the results of PRTR, Zn, B and Mn accounted for a large part of the discharge into the water course. To estimate the behaviour of heavy metals in the environment, leaching tests were applied to the products made of biosolids. During a series of leaching tests for building materials, it was observed that the concentration of heavy metals was very small, but the ratio of increase keeps a constant value. Therefore, it was considered that the acid extractable contents of heavy metal would be important.

Environmental Monitoring↗

PubMed2001

Development of a free beta-galactosidase in vitro test for the assessment of heavy metal toxicity.

The effect of heavy metals and organic compounds on the activity of the enzyme beta-galactosidase in a standardized bioassay has been evaluated, considering future applications in environmental monitoring. The tests were done using a commercial extract of a hydrolase from the eukaryote yeast Kluyveromyces lactis and o-nitrophenyl-beta-D-galactopyranoside (ONPG) as substrate. The enzyme was exposed to Cr(VI), Cd(II), Cu(II), Ni(II), Pb(II), Hg(II), phenol, sodium dodecyl sulfate, methanol and pentachlorophenol for 5, 15, 30, and 60 min. According to the results, a 15 min exposure time was considered optimum for the performance of the assay. Results of tests with metals showed IC50 values ranging between 9.25mg/L for Cd(II) and 0.015mg/L for Hg(II), with an order of sensitivity of: Cd(II) < Ni(II) < Cr(VI) = Pb(II) < Cu(II) < Hg(II). Sensitivity to organic compounds ranged from 200 to 4,000 mg/L, showing a higher specificity to heavy metals. The present in vitro free enzyme test showed a similar behavior to other tests based on beta-galactosidase such as the MetPlate. Furthermore, when compared to data from the literature on acute toxicity assays currently used in environmental assessment, test results show good agreement regarding the sensitivity to metals. After standardization, the proposed test could be used as a rapid and low-cost assay when evaluating biological effects of heavy metals in monitoring programs.

Environmental Monitoring↗

PubMed2005

Evaluation of electrokinetic removal of heavy metals from sewage sludge.

The presence of heavy metals is one of the main obstacles for agricultural use of million tonnes of dewatered sewage sludge produced in wastewater treatment plants. Electrokinetic (EK) treatment can be applied to remove heavy metals from sludge. The aim of this study was to increase the efficiency of electrokinetic removal of heavy metals from dewatered sewage sludge. EK experiments were carried out with and without pH adjustment in cathode chamber of acidified sewage sludge. The selective sequential extraction (SSE) was used to determine the fractionation of heavy metals in sewage sludge. The mobility of heavy metals in sludge significantly increased after its acidification at pH 2.7 and followed the order: Ni, Zn, Cu, As, Cr, Pb. Removal efficiencies of heavy metals in the experiment with acidified sewage sludge and pH adjustment at cathode chamber at 2.0 were: 95% for Zn, 96% for Cu, 90% for Ni, 68% for Cr, 31% for As and 19% for Pb. The concentrations of Zn, Cu, Ni, Cr and Pb after EK treatment were below the United States Environmental Protection Agency limits for biosolids applied to agricultural land, forest, public contact sites or reclamation sites.

Chemical Fractionation↗

PubMed2006

[Application of principal component analysis (PCA) for the estimation of source of heavy metal contamination in marine sediments].

Concentrations of heavy metals and organic matter in the bottom sediments of Jiaozhou Bay were determined and the average enrichment factors (AEFs) were used simultaneously to evaluate the extent of metal enrichment-contamination. Results show that heavy metal contamination in this bay could be divided into three groups: negligible to low contamination (AEFs < 2), which is the case of Zn (AEF = 1.11), Pb (AEF = 1.15), Cr (AEF = 1.52), Mn (AEF = 0.80) and Fe (AEF = 0.45); moderate contamination (AEFs = 2 - 3), which is the case of Cu (AEF = 2.79) and Cd (AEF = 2.52); certain to severe contamination (AEFs > 3), As (AEF = 3.03) and Hg (AEF = 8.08) being included in this group. Principal component analysis (PCA) was applied to estimate the sources of heavy metal contamination. Results that the first three components accounted for 52.61%, 17.37% and 15.60% of the total variance respectively exhibited that industrial wastewater, degradation of organic matter and erosion of rocks were the main sources of heavy metal contamination. The Q-analysis of PCA indicated that 14 stations could be divided into five groups. This result not only reflected the pollution characteristic of surface sediments, but also provided fundamental evidences for the putative analysis that industrial discharge is the main source of heavy metal contamination in Jiaozhou Bay.

Geologic Sediments↗

PubMed2002

Exploiting the genetic and biochemical capacities of bacteria for the remediation of heavy metal pollution.

The threat of heavy metal pollution to public health and wildlife has led to an increased interest in developing systems that can remove or neutralise its toxic effects in soil, sediments and wastewater. Unlike organic contaminants, which can be degraded to harmless chemical species, heavy metals cannot be destroyed. Remediating the pollution they cause can therefore only be envisioned as their immobilisation in a non-bioavailable form, or their re-speciation into less toxic forms. While these approaches do not solve the problem altogether, they do help to protect afflicted sites from noxious effects and isolate the contaminants as a contained and sometimes recyclable residue. This review outlines the most important bacterial phenotypes and properties that are (or could be) instrumental in heavy metal bioremediation, along with what is known of their genetic and biochemical background. A variety of instances are discussed in which valuable properties already present in certain strains can be combined or improved through state-of-the-art genetic engineering. In other cases, knowledge of metal-related reactions catalysed by some bacteria allows optimisation of the desired process by altering the physicochemical conditions of the contaminated area. The combination of genetic engineering of the bacterial catalysts with judicious eco-engineering of the polluted sites will be of paramount importance in future bioremediation strategies.

Bacteria↗

PubMed2006

Development of ELISA for metallothionein-II allows determination of heavy metal pollution of fresh water.

Metallothionein (MT), a metal-binding protein induced primarily by heavy metals in vertebrates, is considered a biomarker for environmental heavy-metal contamination. To investigate heavy metal pollution in the freshwater environment, MT-I and MT-II were purified from livers of crucian carp (Carassius carassius) by gel exclusion chromatography and ion exchange chromatography. To detect the purified MT-II, a specific monoclonal antibody (mAb) against crucian carp MT-II was produced from the hybridoma strains by cell-cell fusion. By using Enzyme-Linked Immunosorbent Assay (ELISA) with this mAb, the purified crucian carp MT-II was detected with a high specificity and sensitivity. There was a good correlation between the amount of MT-II in carp livers and the concentration of heavy metals in water. ELISA was then used to evaluated the degree of heavy metal pollution in two freshwater systems. The results indicate that the MT-II content in carp liver tissue can be used as an indicator of environmental heavy-metal pollution.

Animals↗

PubMed2004

Effect of high concentration of Co (II) on Enterobacter liquefaciens strain C-1: a bacterium highly resistant to heavy metals with an unknown genome.

Heavy metals are required as nutrients for essential functions in microorganisms. However, higher concentrations of these cations are generally toxic and may produce contrasting effects on living organisms. Enterobacter liquefaciens strain C-1, a bacterium isolated from the Moa mine in Cuba, is able to survive in the presence of high concentrations of heavy metals. The proteomes of Enterobacter liquefaciens strain C-1, grown under aerobic conditions in the presence and absence of Co (II) were compared using two-dimensional gel electrophoresis analysis in the isoelectric point range of 4-7 and the mass range of 15-120 kDa. Significant changes in the expression level (> two-fold) were detected for 13 spots: seven and six were up- and down-regulated, respectively. Because the genome of this bacterium is unknown, identification by peptide mass fingerprinting only succeeded in four cases and most of the cross-species identifications were supported by de novo sequencing of tryptic peptides followed by sequence alignment using the MS BLAST program. Twelve different proteins were identified, ten are involved in cellular antioxidant defence probably induced by the presence of Co (II). This is the first step towards understanding the role of proteins participating in the mechanism of resistance to heavy metals in this bacterium.

Amino Acid Sequence↗

PubMed2002

Heavy metals in organisms and sediments from Turkish Coast of the Black Sea, 1997-1998.

During the period 1997-1998, macroalgae, sea snail, mussel, fish and sediment samples were collected at different stations of the Turkish Black Sea coast in order to establish the concentration of selected heavy metals. Heavy metals analyzed were Cd, Co, Cr, Ni, Zn, Fe, Mn, Pb and Cu. The results showed that the Turkish Black Sea coast is facing heavy metal pollution. The metal concentrations in macroalgae, sea snail, mussel and sediment samples are very high. However, Cd, Pb and Cu concentrations in anchovy fish decreased, while Co, Fe, Zn, Cr, Mn and Ni contents had changed when compared previous data. The metal levels in macroalgae did not follow the same pattern as concentrations in sediments at the same station. On the other hand, concentrations of Cd, Co, Cr, Zn, Fe, Mn and Cu in sea snail, mussel and fish samples were related to sediment data in the examined stations.

Animals↗

PubMed2000

Treatment of hazardous sorbents generated from the adsorption of heavy metals during incineration.

The emission of heavy metals during waste incineration can be effectively reduced through the practice of employing non-toxic sorbents. These sorbents can react with toxic metals at high temperatures and create metal binding between them by various physical and chemical mechanisms. After the adsorption process, the used sorbents, which contain heavy metals, need to be desorbed to reduce their potential environmental hazards or provide reusable sorbents for economical aspect. The sorbent's adsorption efficiency is affected by different operating conditions and waste elemental compositions during incineration, which, in turn, affect their desorption characteristics. However, the effects of operating condition and waste elemental composition on the stability of heavy metals in the sorbents and the desorption efficiencies have been little studied. This study investigates the desorption characteristics of heavy metals (Cr, Pb, Cu, and Cd) from the hazardous sorbents with different extracting reagents (H(2)O, HCl, EDTA, and Na(2)S(2)O(5)). The hazardous sorbents were generated under different adsorption time and various input waste elemental compositions during incineration process.

Adsorption↗

PubMed2006

Factorial experimental design for recovering heavy metals from sludge with ion-exchange resin.

Wastewaters containing heavy metals are usually treated by chemical precipitation method in Taiwan. This method can remove heavy metals form wastewaters efficiently, but the resultant heavy metal sludge is classified as hazardous solid waste and becomes another environmental problem. If we can remove heavy metals from sludge, it becomes non-hazardous waste and the treatment cost can be greatly reduced. This study aims at using ion-exchange resin to remove heavy metals such as copper, zinc, cadmium, and chromium from sludge generated by a PCB manufacturing plant. Factorial experimental design methodology was used to study the heavy metal removal efficiency. The total metal concentrations in the sludge, resin, and solution phases were measured respectively after 30 min reaction with varying leaching agents (citric acid and nitric acid); ion-exchange resins (Amberlite IRC-718 and IR-120), and temperatures (50 and 70 degrees C). The experimental results and statistical analysis show that a stronger leaching acid and a higher temperature both favor lower heavy metal residues in the sludge. Two-factors and even three-factor interaction effects on the heavy metal sorption in the resin phase are not negligible. The ion-exchange resin plays an important role in the sludge extraction or metal recovery. Empirical regression models were also obtained and used to predict the heavy metal profiles with satisfactory results.

Analysis of Variance↗

PubMed1989

Inhibition of phorbol ester binding and protein kinase C activity by heavy metals.

Other laboratories have reported biphasic effects of heavy metals on protein kinase C activity: stimulation followed by inhibition at higher concentrations. We demonstrate that these earlier findings most likely resulted from a combination of the effect of the heavy metals to liberate Ca2+ from Ca2+-EGTA buffer systems and the direct inhibitory effects of the metals on protein kinase C. Simulations of such interactions substantiate this conclusion. When soluble protein kinase C is prepared without the addition of Ca2+ or chelator, heavy metals (Cd2+, Cu2+, Hg2+, Zn2+, in the 10 microM range) inhibit the activity of, and the binding of regulatory ligands to, protein kinase C. Heavy metals inhibit the extent of [3H]phorbol dibutyrate binding without affecting the affinity of the interaction, an inhibition that is not surmounted by excess phospholipid. Heavy metals also inhibit the phospholipid-dependent catalytic activity of protein kinase C in a manner that excess phosphatidylserine can overcome. The inhibition of enzyme activity by heavy metals cannot be surmounted by excess Ca2+ or Mg2+. The inhibitory effects of heavy metals are not confined to protein kinase C. Heavy metals also inhibit cyclic AMP binding to cyclic AMP-dependent protein kinase and the catalytic activity of that kinase, but in a distinctly different pattern.

Animals↗

PubMed1994

Cytotoxicity of dust constituents towards alveolar macrophages: interactions of heavy metal compounds.

The interactions between different heavy metal compounds which affect their cytotoxicity towards rabbit alveolar macrophages were investigated. The cells were exposed in vitro to combinations of As3+, Cd2+, Hg2+, Ni2+, or V5+ with different concentrations of another heavy metal compound. Toxicity was determined as the depression of zymosan-induced release of superoxide anion radicals. Significant antagonisms occurred in the combinations Cd2+/Zn2+, Hg2+/As3+, and Hg2+/Se4+, while significant synergisms were exhibited by the combinations Cd2+/Cu2+, Cd2+/Sn2+, Hg2+/Cu2+, Ni2+/Cd2+, Ni2+/Cu2+, Ni2+/Sn2+ and V5+/Cu2+. In the combinations As3+/Zn2+, Hg2+/Cd2+ and Hg2+/Zn2+, both kinds of interactions were observed depending on the concentrations of the heavy metal compounds. An interpretation of the measured heavy metal interactions with reference to the toxicity of heavy metal-containing dusts is attempted.

Animals↗

PubMed2004

Effect of metal spiking on different chemical pools and chemically extractable fractions of heavy metals in sewage sludge.

A laboratory experiment was conducted to study the effect of metal spiking and incubation on some properties and sequentially extractable chemical pools of some heavy metals (F1, two extractions with 0.1 M Sr(NO3)2; F2, one extraction with 1 M NaOAc (pH 5.0); F3, three extractions with 5% NaOCl (pH 8.5) at 90-95 degrees C; F4, three extractions with 0.2 M oxalic acid + 0.2 M ammonium oxalate + 0.1 M ascorbic acid (pH 3.0); and F5, dissolution of sample residue in HF-HClO4 (residual fraction,) and also 1 M CaCl2 and 0.005 M DTPA extractable heavy metals in sewage sludge. Metal spiking and incubation decreased pH and easily oxidizable organic C content of sludge but increased electrical conductivity. Metal spiking and incubation increased F1 fraction of all heavy metals, F2 fraction of Ni, Pb, Cu, and Cd, F3 fraction of Pb, Cu, and Cd, F4 or reducible fraction of Ni, Cu, and Cd and residual fraction of Zn and Pb, but decreased F2 fraction of Zn, F3 of Zn and Ni, F4 fraction of Zn and F5 fraction of Ni, Cu, and Cd. Metal spiking and incubation increased 1 M CaCl2 and 0.005 M DTPA extractable amounts of all heavy metals in sludge except for 0.005 M DTPA extractable Zn, which registered only very marginal decrease.

Biological Availability↗

PubMed1999

Genotoxicity biomarkers in the assessment of heavy metal effects in mussels: experimental studies.

Heavy metals are stable and persistent environmental contaminants. The range of metal concentrations is generally below acute thresholds in coastal areas, where recognition of chronic sublethal effects is more relevant. Evidence of long-term adverse effects, such as cancer, due to heavy metals in marine animals comes from a number of field and experimental studies. The mechanism of metal carcinogenicity remains largely unknown, although several lines of experimental evidence suggest that a genotoxic effect may be involved. The aim of our study was to evaluate the sensitivity of genotoxicity tests, alkaline elution and micronucleus test, as biomarkers for the detection of heavy metals in mussels as the sentinel species. Experimental studies were carried out on Mytilus galloprovincialis exposed in aquarium (5 days) to different concentrations of three selected metal salts, CuCl2 (5, 10, 20, 40, 80 micrograms/l/a), CdCl2 (1.84, 18.4, 184 micrograms/l/a), and HgCl2 (32 micrograms/l/a), and to a mixture of equimolar doses of the three metals to study the results of their joint action. Metallothionein quantitation was used as a marker of metal exposure. Lysosomal membrane stability was applied to evaluate the influence of physiological status on genotoxic damage. The ranking of genotoxic potential was in decreasing order: Hg > Cu > Cd. Cu and Hg caused an increase of DNA single-strand breaks and micronuclei frequency. Cd induced a statistical increase of DNA damage, but gave negative results with the micronucleus test. A relationship between genotoxic effects and metallothionein content was observed. Reduction in lysosomal membrane stability with the increasing concentration of heavy metals was also evident.

Animals↗