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1.
米氏凯伦藻溶血毒素的溶血反应特征   总被引:3,自引:0,他引:3  
探讨了温度、pH值、二价阳离子等对米氏凯伦藻(Karenia mikimotoi Hasen)溶血毒素溶血活性的影响,分析了米氏凯伦藻溶血毒素的溶血反应特征.结果表明,实验室培养米氏凯伦藻的溶血活性约为64.69±6.43 HU L-1,单个藻细胞的溶血活性为6.17±0.61×10-6 HU;在实验温度(0~37℃)下,溶血活性随温度的增加而增加;pH6.0时的溶血活性最高;Cu2+、Mg2+、Mn2+、Ca2+、Co2+、Zn2+和Hg2+等对米氏凯伦藻的溶血活性的影响不同.离子浓度为5 mmol/L时,Hg2+的抑制作用最强.高浓度Hg2+对红细胞的集合效应不但阻止了Hg2+进入血细胞诱导的溶血作用,而且阻止了毒素对细胞膜的破坏,但这种抑制作用可被EDTA消除.  相似文献   

2.
Summary Sediments of the rivers Rhine and Yssel and sewage sludge samples showed high mercury contents (5–30 ppm). Usually less than 1% — in one sludge sample 5% — of the mercury was in the form of methylmercury. Incubation of these samples, under varied aerobic and anaerobic conditions, with or without HgCl2 or phenylmercuryacetate added, gave no or only very slight formation of methylmercury.Most agricultural soils have a mercury content below 0.1 ppm and methylation will be no problem.  相似文献   

3.
Cell-density-dependent sensitivity of a mer-lux bioassay.   总被引:2,自引:0,他引:2       下载免费PDF全文
The sensitivity of a previously described assay (O. Selifonova, R. Burlage, and T. Barkay, Appl. Environ. Microbiol. 59:3083-3090, 1993) for the detection of bioavailable inorganic mercury (Hg2+) by the activation of a mer-lux fusion was increased from nanomolar to picomolar concentrations by reducing biomass in the assays from 10(7) to 10(5) cells ml-1. The increase in sensitivity was due to a reduction in the number of cellular binding sites that may compete with the regulatory protein, MerR, for binding of the inducer, Hg2+. These results show that (i) the sensitivity of the mer-lux assay is sufficient for the detection of Hg2+ in most contaminated natural waters and (ii) mer-specified reactions, Hg2+ reduction and methylmercury degradation, can be induced in natural waters and may participate in the geochemical cycling of mercury.  相似文献   

4.
The objective of the present communication is to describe the role played by combinations between diethydithiocarbamate (DDC) and divalent metals in hemolysis of human RBC. RBC which had been treated with DDC (10-50 microM) were moderately hemolyzed (about 50%) upon the addition of subtoxic amounts of Cu2+ (50 microM). However, a much stronger and a faster hemolysis occurred either if mixtures of RBC-DDC were immediately treated either by Co2+ (50 microM) or by a premixture of Cu2+ and Co2+ (Cu:Co) (50 microM). While Fe2+ and Ni2+, at 50 microM, initiated 30-50% hemolysis when combined with DDC (50 microM), on a molar basis, Cd2+ was at least 50 fold more efficient than any of the other metals in the initiation of hemolysis by DDC. On the other hand, neither Mn2+ nor Zn2+, had any hemolysis-initiating effects. Co2+ was the only metal which totally blocked hemolysis if added to DDC prior to the addition of the other metals. Hemolysis by mixtures of DDC + (Cu:Co) was strongly inhibited by anaerobiosis (flushing with nitrogen gas), by the reducing agents glutathione, N-acetyl cysteine, mercaptosuccinate, ascorbate, TEMPO, and alpha-tocopherol, by the PLA2 inhibitorbromophenacylbromide (BrPACBr), by tetracycline as well as by phosphatidyl choline, cholesterol and by trypan blue. However, TEMPO, BrPACBr and PC were the only agents which inhibited hemolysis induced by DDC: Cd2+ complexes. On the other hand, none of the classical scavengers of reactive oxygen species (ROS) employed e.g dimethylthiourea, catalase, histidine, mannitol, sodium benzoate, nor the metal chelators desferal and phenanthroline, had any appreciable inhibitory effects on hemolysis induced by DDC + (Cu:Co). DDC oxidized by H2O2 lost its capacity to act in concert either with Cu2+ or with Cd2+ to hemolyze RBC. While either heating RBC to temperatures greater than 37 degrees C or exposure of the cells to glucose-oxidase-generated peroxide diminished their susceptibility to hemolysis, exposure to the peroxyl radical from AAPH, enhanced hemolysis by DDC + (Cu:Co). The cyclovoltammetry patterns of DDC were drastically changed either by Cu2+, Co2+ or by Cd2+ suggesting a strong interaction of the metals with DDC. Also, while the absorbance spectrum of DDC at 280 nm was decreased by 50% either by Co2+, Cd2+ or by H2O2, a 90% reduction in absorbance occurred if DDC + H2O2 mixtures were treated either by Cu2+ or by Co2+, but not by Cd2+. Taken together, it is suggested that DDC-metal chelates can induce hemolysis by affecting the stability and the integrity of the RBC membrane, and possibly also of the cytoskeleton and the role played by reducing agents as inhibitors might be related to their ability to deplete oxygen which is also supported by the inhibitory effects of anaeobiosis.  相似文献   

5.
To study the effects of long-term selenium supplementation on absorption, distribution, and elimination of methylmercury (MeHg) in mice, three groups of male mice (Balb/c CA) were exposed for 7 wk to 0, 0.6, and 3 ppm sodium selenite in tap water. They were then given a single oral dose of Me203Hg (2 μmol/kg) by gastric intubation, and elimination of203Hg was followed by whole-body counting for 49 d at the same Se exposure as previously. Twenty-four hours and 49 d after dosage, 6–7 animals/group were sampled for analysis of203Hg distribution in the body. Glutathione peroxidase (GSH-PX) activity in blood and selenium levels in the liver were used as measures of selenium status. Gastrointestinal absorption of Me203Hg was not influenced by the Se status of the animals. Selenium supplementation of MeHg-exposed mice caused an enhanced whole-body elimination of Hg, but selenium-supplemented animals did not have lower Hg levels in the brain and kidney than nonsupplemented animals. The effect of selenium on the accumulation, of Hg in the brain was dose-dependent, a high dose (3 ppm Se) causing a higher initial accumulation of Hg. The intracellular distribution of203Hg in the liver and kidney was not affected by Se. The results indicate that selenium treatment of MeHg-exposed mice may have a positive effection the health of the animals by decreasing the total body burden of MeHg.  相似文献   

6.
Binding capacities of membrane suspensions and dissolved compounds for mercurials were titrated by a new potentiometric method. Critical steps included a silver electrode of new design, the use of L-cysteine as a thiol buffer, a nitrogen atmosphere, and pretreatment of samples with equimolar mercurial and cysteine. Titrations had a sharp endpoint, accurate +/- 26 nmole methylmercury or +/- 8 nmole mercuric salt. Measurements of binding capacity of bovine serum albumin averaged 93% of the titer predicted for one SH group per molecule; those of human hemoglobin yielded 86-91% of the titer predicted for two SH groups per molecule. Yields dropped with exposure of protein solutions or membrane suspensions to atmospheric oxygen. Brain microsomes had significantly higher binding capacities (per milligram of protein) than red blood cell ghosts. The ratio of endpoint titers of CH3HgCl to HgCl2 averaged 2:1 in assays of cysteine, proteins, and membranes, showing that the assay was free of denaturation artifacts and protein-protein interference. Solutions of EDTA showed measurable binding of Hg2+ but not of CH3Hg+. Satisfactory titrations were also obtained with N-ethylmaleimide.  相似文献   

7.
The effect of added Cd(II), Cu(II), Cr(VI), or Hg(II) at 0.01 to 100 ppm on metabolism in anaerobic bacterial consortia which degrade 2-chlorophenol (2CP), 3-chlorobenzoate (3CB), phenol, and benzoate was examined. Three effects were observed, including extended acclimation periods (0.1 to 2.0 ppm), reduced dechlorination or biodegradation rates (0.1 to 2.0 ppm), and failure to dechlorinate or biodegrade the target compound (0.5 to 5.0 ppm). 3CB biodegradation was most sensitive to Cd(II) and Cr(VI). Biodegradation of benzoate and phenol was most sensitive to Cu(II) and Hg(II), respectively. Adding Cr(VI) at 0.01 ppm increased biodegradation rates of phenol (177%) and benzoate (169%), while Cd(II) and Cu(II) at 0.01 ppm enhanced biodegradation rates of benzoate (185%) and 2CP (168%), respectively. Interestingly, with Hg(II) at 1.0 to 2.0 ppm, 2CP and 3CB were biodegraded 133 to 154% faster than controls after an extended acclimation period, suggesting adaptation to Hg(II). Metal ions were added at inhibitory, but sublethal, concentrations to investigate effects on metabolic intermediates and end products. Phenol accumulated to concentrations higher than those in controls only in the 2CP consortium with added Cu(II) at 1.2 ppm but was subsequently degraded. There was no effect on benzoate, and little effect on acetate intermediates was observed. In most cases, methane yields were reduced by 23 to 97%. Thus, dehalogenation, aromatic degradation, and methanogenesis in these anaerobic consortia showed differential sensitivities to the heavy metal ions added. These data indicate that the presence of heavy metals can affect the outcome of anaerobic bioremediation of aromatic pollutants. In addition, a potential exists to use combinations of anaerobic bacterial species to bioremediate sites contaminated with both heavy metals and aromatic pollutants.  相似文献   

8.
In well-controlled experiments using white leghorn chickens and Japanese quail, dietary polychlorinated biphenyls (PCBs), DDT and related compounds produced no detrimental effects on eggshell quality. A drastic reduction in hatchability of chicks occurred with 10-20 ppm PCBs, but no detrimental effects on eggshell quality, egg production or hatchability were found with 0.5 and 1.0 ppm PCBs, or DDT up to 100 ppm. Dietary PCBs potentiated a vitamin E-selenium deficiency in the chick, increased exudative diathesis, and decreased plasma glutathione peroxidase levels. Dietary PCBs induced hepatic microsomal benzopyrine hydroxylase. Dietary levles of 100 or 200 ppm inorganic mercury as HgSO4 or HgCl2 had little effect on egg production, hatchability, shell quality, morbidity and mortality. Methylmercury chloride, however, at levels providing 10 or 20 mg Hg/kg of diet, severely affected all of these parameters. Even though the present experiments demonstrate that neither DDT nor PCBs has any effect on eggshell quality in chickens and Japanese quail, they may cause thinning of eggshells in other species. Controlled experiments are lacking. Eagles, ospreys and pelicans all consume fish which in many areas of the world are known to contain methyl mercury. The thinning of eggshells in the species in the wild may have been due, at least in part, to environmental contamination with methylmercury rather than DDT, DDE or PCBs, as has been claimed.  相似文献   

9.
Under the treatment of heavy metal ions Pb2+, Cd2+ and Hg2+, the interval of mitotic stage was shortened, and the time of interphase prolonged so that the cell cycle was prolonged in the root-tip cells of broadbean (Vicia faba L. ). With the increase of concentrations of Pb2+, Cd2+ and Zn2+ below 1.0, 0.01 and 10 ppm respectively, the mitosis index (IM) rose in root-tip cells, but IM decreased when the root-tips were treated with the some heavy metal ions above the above-mentioned respective concentrations. IM was inhibited in Hg2+ of any concentrations. Within the concentration of Pb2+, Cd2+, Hg2+ and Zn2+ below 1.0, 0. 50, 5.0, 100.0 ppm respectively, the frequency of micronucleus (MCNF) rose as the concentrations were increased, and lowered as the respective concentrations exceeded those stated above. Similar changes occurred in the frequency of chromosomal aberrations (CAF) when the concentration of Pb2+, Cd2+, Hg2+, Zn2+ were below or above 5.0, 5.0, 0.50, 100.0 ppm respectively. Mn2+ had no significant effects to them. By data processing with the method of gray system control and computer aided drawing to IM, MCNF and CAF, it was shown that the three parameters varied tremendously in different dose-effect ranges. All of which suggested that in order to obtain a reliable results in the environmental monitoring and hazardous material detection, genetoxicity inspection should be carried out under the optimal condition when (1) the concentration of the heavy metal to be detected does not seriously inhibit mitosis and (2) CAF and MCNF is in positive correlation.  相似文献   

10.
Effects in vivo of cadmium (Cd), mercury (Hg) and methylmercury (CH3Hg) on Na(+)-K+ ATPase and uptake of 3H-dopamine (DA) in rat brain synaptosomes were studied. These heavy metals significantly inhibited the Na(+)-K+ ATPase activity in a dose-dependent manner. Similarly, inhibition of DA uptake by synaptosomes was also observed in rats treated with these metals. Intraperitoneal route of metal administration was found to be more effective than per os treatment. Mercuric compounds compared to Cd elicited a higher inhibition of Na(+)-K+ ATPase and DA uptake in rat brain synaptosomes.  相似文献   

11.
A methylene blue-mediated enzyme biosensor has been developed for the detection of inhibitors including mercury(II), mercury(I), methylmercury, and mercury-glutathione complex. The inhibition to horseradish peroxidase was apparently reversible and noncompetitive in the presence of HgCl2 in less than 8 s and irreversibly inactivated when incubated with different concentrations of HgCl2 for 1-8 min. The binding site of horseradish peroxidase with HgCl2 probably was a cysteine residue SH. Mercury compounds can be assayed amperometrically with the detection limits 0.1 ng ml(-1) Hg for HgCl2 and methylmercury, 0.2 ng ml(-1) Hg for Hg2(NO3)2 and 1.7 ng ml(-1) Hg for mercury glutathione complex. Inactivation of the immobilized horseradish peroxidase was displayed in the AFM images of the enzyme membranes.  相似文献   

12.
The effects of three ligands for ligandin on the biliary excretion of methylmercury were investigated in male rats injected intravenously with 1.0 mg/kg Hg as Me203 HgCl. Bromosulphophthalein and indocyanine green inhibited the biliary excretion of methylmercury, while bilirubin had no such effect. None of the compounds tested which inhibited the biliary excretion of methylmercury decreased bile flow or changed the hepatic concentration of mercury of non-protein thiols. The possibility of the involvement of ligandin in the biliary excretion of methylmercury is discussed.  相似文献   

13.
The objective of the present communication is to describe the role played by combinations between diethydithiocarbamate (DDC) and divalent metals in hemolysis of human RBC. RBC which had been treated with DDC (10–50 μM) were moderately hemolyzed (about 50%) upon the addition of subtoxic amounts of Cu2+ (50 μM). However, a much stronger and a faster hemolysis occurred either if mixtures of RBC-DDC were immediately treated either by Co2+ (50 μM) or by a premixture of Cu2+ and Co2+ (Cu:Co) (50 μM).

While Fe2+ and Ni2+, at 50 μM, initiated 30–50% hemolysis when combined with DDC (50 μM), on a molar basis, Cd2+ was at least 50 fold more efficient than any of the other metals in the initiation of hemolysis by DDC. On the other hand, neither Mn2+ nor Zn2+, had any hemolysis-initiating effects. Co2+ was the only metal which totally blocked hemolysis if added to DDC prior to the addition of the other metals.

Hemolysis by mixtures of DDC + (Cu:Co) was strongly inhibited by anaerobiosis (flushing with nitrogen gas), by the reducing agents glutathione, N-acetyl cysteine, mercaptosuccinate, ascorbate, TEMPO, and α-tocopherol, by the PLA2 inhibitor bromophenacylbromide (BrPACBr), by tetracycline as well as by phosphatidyl choline, cholesterol and by trypan blue. However, TEMPO, BrPACBr and PC were the only agents which inhibited hemolysis induced by DDC:Cd2+ complexes.

On the other hand, none of the classical scavengers of reactive oxygen species (ROS) employed e.g dimethylthiourea, catalase, histidine, mannitol, sodium benzoate, nor the metal chelators desferal and phenanthroline, had any appreciable inhibitory effects on hemolysis induced by DDC + (Cu:Co).

DDC oxidized by H2O2 lost its capacity to act in concert either with Cu2+ or with Cd2+ to hemolyze RBC.

While either heating RBC to temperatures greater than 37°C or exposure of the cells to glucose-oxidase-generated peroxide diminished their susceptibility to hemolysis, exposure to the peroxyl radical from AAPH, enhanced hemolysis by DDC + (Cu:Co).

The cyclovoltammetry patterns of DDC were drastically changed either by Cu2+, Co2+ or by Cd2+ suggesting a strong interaction of the metals with DDC. Also, while the absorbance spectrum of DDC at 280 nm was decreased by 50% either by Co2+, Cd2+ or by H2O2, a 90% reduction in absorbance occurred if DDC + H2O2 mixtures were treated either by Cu2+ or by Co2+, but not by Cd2+.

Taken together, it is suggested that DDC-metal chelates can induce hemolysis by affecting the stability and the integrity of the RBC membrane, and possibly also of the cytoskeleton and the role played by reducing agents as inhibitors might be related to their ability to deplete oxygen which is also supported by the inhibitory effects of anaeobiosis.  相似文献   

14.
Inorganic mercury in contaminated soils and sediments is relatively immobile, though biological and chemical processes can transform it to more toxic and bioavailable methylmercury. Methylmercury is neurotoxic to vertebrates and is biomagnified in animal tissues as it is passed from prey to predator. Traditional remediation strategies for mercury contaminated soils are expensive and site-destructive. As an alternative we propose the use of transgenic aquatic, salt marsh, and upland plants to remove available inorganic mercury and methylmercury from contaminated soils and sediments. Plants engineered with a modified bacterial mercuric reductase gene, merA, are capable of converting Hg(II) taken up by roots to the much less toxic Hg(0), which is volatilized from the plant. Plants engineered to express the bacterial organo-mercurial lyase gene, merB, are capable of converting methylmercury taken up by plant roots into sulfhydryl-bound Hg(II). Plants expressing both genes are capable of converting ionic mercury and methylmercury to volatile Hg(0) which is released into an enormous global atmospheric Hg(0) pool. To assess the phytoremediation capability of plants containing the merA gene, a variety of assays were carried out with the model plants Arabidopsis thaliana, and tobacco (Nicotiana tabacum).  相似文献   

15.
In this work we isolated from soil and characterized several bacterial strains capable of either resisting high concentrations of heavy metals (Cd2+ or Hg2+ or Pb2+) or degrading the common soil and groundwater pollutants MTBE (methyl-tert-butyl ether) or TCE (trichloroethylene). We then used soil microcosms exposed to MTBE (50 mg/l) or TCE (50 mg/l) in the presence of one heavy metal (Cd 10 ppm or Hg 5 ppm or Pb 50 or 100 ppm) and two bacterial isolates at a time, a degrader plus a metal-resistant strain. Some of these two-membered consortia showed degradation efficiencies well higher (49–182% higher) than those expected under the conditions employed, demonstrating the occurrence of a synergetic relationship between the strains used. Our results show the efficacy of the dual augmentation strategy for MTBE and TCE bioremediation in the presence of heavy metals.  相似文献   

16.
1. The fresh-water fish, Clarias lazera, was exposed to 13 lethal and sublethal concentrations of mercury. 2. The median tolerance limit (TLm) at different exposure periods, 24, 48, 72 and 96 hr, appears to be as follows: 0.96, 0.88, 0.81 and 0.72 ppm Hg2+/l, respectively. 3. From the subacute tests, the maximum acceptable toxicant concentration (MATC) for this fish was between 0.10 and 0.22 ppm Hg2+/l. 4. Behavioural changes, tissue Hg2+ distribution and serum ionic patterns were recorded during both the acute and subacute exposure periods.  相似文献   

17.
Geochemistry of mercury in an intertidal flat of the Scheldt estuary   总被引:3,自引:0,他引:3  
Sediments were sampled on the ‘Groot Buitenschoor’, an intertidal flat located at about 60 km from the Scheldt's river mouth. Hg concentrations ranged from 30 to 1756 ng g−1. The concentrations were strongly correlated with fine grain fraction, organic matter content and sulphide concentrations. Incubation experiments were performed in order to determine the potential methylation rate of Hg as well as biotic and abiotic factors influencing this transformation. About 1 to 2% of the added inorganic Hg is converted into methylmercury. This conversion rate points to the same equilibrium ratio as was observed in natural sediments, indicating an equilibrium between methylation and demethylation reactions in the sediments. Incubation of a sterilised sediment sample significantly decreased the methylation rate, but the methylmercury concentrations observed are still ten times higher than the natural (unspiked) sediment. This result could be due to a chemical (non-enzymatic) methylation of mercury. Sulphate reducing bacteria are the main species responsible for the methylation of Hg at this site. Addition of Na2MoO4, a specific inhibitor of sulphate reducing bacteria, decreased the methylation rate to the abiotic level (sterilised sediment). High sulphate reduction rates, however, lead to lower methylation rates. Increased formation of sulphides due to microbial sulphate reduction leads to enhanced HgS formation and this reaction competes with the methylation process. HgS is in fact the major product formed by the reaction of sulphate reducing bacteria with Hg species. About 50% of the Hg spiked to the sediments is transformed into HgS during the incubation experiments, and that compound is practically unavailable for methylation in contrast to other bound forms of Hg.  相似文献   

18.
Mercury and organomercurial resistance determined by genes on ten Pseudomonas aeruginosa plasmids and one Pseudomonas putida plasmid have been studied with regard to the range of substrates and the range of inducers. The plasmidless strains were sensitive to growth inhibition by Hg(2+) and did not volatilize Hg(0) from Hg(2+). A strain with plasmid RP1 (which does not confer resistance to Hg(2+)) similarly did not volatilize mercury. All 10 plasmids determine mercury resistance by way of an inducible enzyme system. Hg(2+) was reduced to Hg(0), which is insoluble in water and rapidly volatilizes from the growth medium. Plasmids pMG1, pMG2, R26, R933, R93-1, and pVS1 in P. aeruginosa and MER in P. putida conferred resistance to and the ability to volatilize mercury from Hg(2+), but strains with these plasmids were sensitive to and could not volatilize mercury from the organomercurials methylmercury, ethylmercury, phenylmercury, and thimerosal. These plasmids, in addition, conferred resistance to the organomercurials merbromin, p-hydroxymercuribenzoate, and fluorescein mercuric acetate. The other plasmids, FP2, R38, R3108, and pVS2, determined resistance to and decomposition of a range of organomercurials, including methylmercury, ethylmercury, phenylmercury, and thimerosal. These plasmids also conferred resistance to the organomercurials merbromin, p-hydroxymercuribenzoate, and fluorescein mercuric acetate by a mechanism not involving degradation. In all cases, organomercurial decomposition and mercury volatilization were induced by exposure to Hg(2+) or organomercurials. The plasmids differed in the relative efficacy of inducers. Hg(2+) resistance with strains that are organomercurial sensitive appeared to be induced preferentially by Hg(2+) and only poorly by organomercurials to which the cells are sensitive. However, the organomercurials p-hydroxymercuribenzoate, merbromin, and fluorescein mercuric acetate were strong gratuitous inducers but not substrates for the Hg(2+) volatilization system. With strains resistant to phenylmercury and thimerosal, these organomercurials were both inducers and substrates.  相似文献   

19.
《Inorganica chimica acta》1986,111(2):171-178
The structures of solvated methylmercury(II) halides in pyridine solution were determined by a large angle X-ray scattering technique. Near-linear CH3HgX (X = Cl, Br and I) species solvated by two weakly-coordinated pyridine molecules are indirectly interpreted. Additional mercury-pyridine interactions, through van der Waals forces, are found at the sum of the van der Waals radii. The HgX bond distances in the methylmercury(II) halides are found to be 2.325(8), 2.480(3) and 2.649(3) Å for chloride, bromide and iodide, respectively. The HgC bond distances are assumed to be ∼2.08 Å. This interaction is indicated in the radial distribution functions. The bond distance between mercury and the two solvating pyridine molecules is ∼2.8 Å, e.g., 2.84(2) Å in methylmercury(II) bromide. The additional mercury interactions with roughly two pyridine molecules at the sum of van der Waals radii are revealed at around 3.15 Å. Comparison between Raman stretching vibrations and the solvated structures of methylmercury(II) complexes found in various solvents indicates a lower limit in solvent donor property for the formation of solvate bonds to mercury for the methylmercury(II) halides.  相似文献   

20.
The unicellular green algaClosterium moniliferum was sensitive to the action of divalent Ni, Cu, Hg and Cd chlorides both in CO2 fixation and in thymidine incorporation into DNA. At 0.08 ppm, Cd2+ was the most potent inhibitor (86 % inhibition of both processes), followed by Hg2+ and Cu2+, and finally by Ni2+, thymidine incorporation being generally more affected than CO2 fixation.  相似文献   

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