Wounding of Arabidopsis halleri leaves enhances cadmium accumulation that acts as a defense against herbivory.

Approximately 0.2 % of all angiosperms are classified as metal hyperaccumulators based on their extraordinarily high leaf metal contents, for example >1 % zinc, >0.1 % nickel or >0.01 % cadmium (Cd) in dry biomass. So far, metal hyperaccumulation has been considered to be a taxon-wide, constitutively expressed trait, the extent of which depends solely on available metal concentrations in the soil. Here we show that in the facultative metallophyte Arabidopsis halleri, both insect herbivory and mechanical wounding of leaves trigger an increase specifically in leaf Cd accumulation. Moreover, the Cd concentrations accumulated in leaves can serve as an elemental defense against herbivory by larvae of the Brassicaceae specialist small white (Pieris rapae), thus allowing the plant to take advantage of this non-essential trace element and toxin. Metal homeostasis genes are overrepresented in the systemic transcriptional response of roots to the wounding of leaves in A. halleri, supporting that leaf Cd accumulation is preceded by systemic signaling events. A similar, but quantitatively less pronounced transcriptional response was observed in A. thaliana, suggesting that the systemically regulated modulation of metal homeostasis in response to leaf wounding also occurs in non-hyperaccumulator plants. This is the first report of an environmental stimulus influencing metal hyperaccumulation.

Removal of Cadmium, Lead and Arsenic from Water by Lactic Acid Bacteria

A number of contaminants such as arsenic, cadmium and lead are released into the environment from natural and anthropogenic sources contaminating food and water. Chronic oral ingestion of arsenic, cadmium and lead is associated with adverse effects in the skin, internal organs and nervous system. In addition to conventional methods, biosorption using inactivated biomasses of algae, fungi and bacteria has been introduced as a novel method for decontamination of toxic metals from water. The aim of this work was to evaluate the applicability of lactic acid bacteria as tools for heavy metal removal from water and characterize their properties for further development of a biofilter. The results established that in addition to removal of mycotoxins, cyanotoxins and heterocyclic amines, lactic acid bacteria have a capacity to bind cationic heavy metals, cadmium and lead. The binding was found to be dependent on the bacterial strain and pH, and occurred rapidly on the bacterial surface, but was reduced in the presence of other cationic metals. The data demonstrates that the metals were bound by electrostatic interactions to cell wall components. Transmission electron micrographs showed the presence of lead deposits on the surface of biomass used in the lead binding studies, indicating involvement of another uptake/binding mechanism. The most efficient strains bound up to 55 mg Cd and 176 mg Pb / g dry biomass. A low removal of anionic As(V) was also observed after chemical modification of the cell wall. Full desorption of bound cadmium and lead using either dilute HNO₃ or EDTA established the reversibility of binding. Removal of both metals was significantly reduced when biomass regenerated with EDTA was used. Biomass regenerated with dilute HNO3 retained its cadmium binding capacity well, but lead binding was reduced. The results established that the cadmium and lead binding capacity of lactic acid bacteria, and factors affecting it, are similar to what has been previously observed for other biomasses used for the same purpose. However, lactic acid bacteria have a capacity to remove other aqueous contaminants such as cyanotoxins, which may give them an additional advantage over the other alternatives. Further studies focusing on immobilization of biomass and the removal of several contaminants simultaneously using immobilized bacteria are required.

Cadmium body burden of the Swiss population.

Urinary cadmium (Cd) excretion was measured within a representative Swiss collective. With a median of 0.23 µg/24 h (n = 1409) and the 95th percentile at 0.81 µg/24 h, no increased health risk for the general non-exposed population was identified. The independent variables Age, BMI and Smoking habit had a significant effect on urinary Cd excretion. No association was found with the region of residence and sex. A subsample comparison between 24-h and spot urines of the same subjects (n = 90) did not reveal an evident concentration difference for both creatinine-adjusted sample types. Dependencies on age and gender were observed for creatinine, which consequently impacts on the creatinine normalisation of urine samples.

Dietary calcium restriction enhances cadmium-induced metallothionein synthesis in rats.

Experiments were conducted with adult male rats to investigate the effects of dietary calcium (Ca) restriction upon intake and tissue distribution of cadmium (Cd), and Cd-metallothionein (Mt) synthesis. Four groups of animals were fed either a low-Ca, semisynthetic diet (0.1% Ca) or the same diet supplemented with 0.8% Ca (normal diet). The caloric intake was similar in all groups. Two groups (low-Ca and normal diet) were used as controls, and two groups (low-Ca and normal diet) received 100 mg/l Cd (as CdCl2) in drinking water. Cd levels in liver, kidney, spleen and red cells were measured in all animals after 8 weeks of treatment. Concomitantly, Mt levels in plasma, liver and kidney were evaluated by radioimmunoassay. Ca deficiency entailed marked and significant increases in accumulation of Cd and synthesis of Mt in all assayed tissues. It is concluded that dietary Ca restriction, independent of caloric intake, enhances Cd intestinal absorption and tissue accumulation, which is followed by increased tissue Mt synthesis.

Cadmium uptake and induction of metallothionein synthesis in a renal epithelial cell line (LLC-PK1).

LLC-PK1 cells, an established cell line from pig kidney with proximal tubule properties, were cultivated in vitro at confluence on plastic dishes. They were then exposed (apical side) to inorganic cadmium (CdCl2, 5 microM) for periods ranging between 1 to 24 h. Analysis of the cell supernatant after homogenisation and ultracentrifugation indicated that Cd taken up in the first 3 h was bound to cytosolic high molecular weight proteins, but was redistributed to low molecular weight proteins at later stages. Induction of Cd-metallothionein (Cd-Mt) synthesis, as judged from Cd-Mt binding to a specific anti-Cd-Mt antibody and from the rate of 35S-cys incorporation into a specific protein fraction, was apparent 3-6 h after the addition of Cd to the incubation medium.

Fate of cadmium in rat renal tubules: a micropuncture study.

Free-flow micropuncture was carried out in superficial nephrons of Munich-Wistar type rats infused acutely with Cd acetate (CdA) or Cd-DTPA (141 microM Cd). Fluid obtained from Bowman's space (BS) or end-proximal tubule sites was analyzed for Cd and inulin. The fluid/plasma Cd concentration ratio in BS averaged 0.2 and 1.0 during CdA and Cd-DTPA infusions, respectively. End-proximal tubule fractional excretion of Cd during CdA infusion averaged 0.34. Previous administration of CdA (1.0 mg/kg, 48 hr before micropuncture) increased the level of circulating Cd-metallothioneins, as measured by radioimmunoassay, but did not affect the luminal tubular uptake of Cd during CdA infusion. No net transepithelial movement of Cd-DTPA was measured. It is concluded that Cd ultrafiltered during inorganic Cd administration is taken up to a large extent by the convoluted part of proximal tubules.

Fate of cadmium in rat renal tubules: a microinjection study.

109Cd was injected into the lumen of superficial proximal or distal tubules of rat kidneys, and recovery in the pelvic urine from the ipsilateral kidney was measured. Fractional recovery of labeled inulin always exceeded 90%. About 70% of injected inorganic Cd (CdCl2) was taken up by the epithelium of proximal tubules, while more than 90% of the injected amount was recovered after distal microinjection. The proximal fractional Cd uptake of a 1:1 (molar) Cd-L-cysteine complex was 82%, but was below 60% for a 5-10:1 molar ratio of cysteine:Cd. The chelate Cd-pentetic acid was recovered in final urine nearly quantitatively after proximal or distal microinjection. Fractional uptake of 109Cd from a Cd-metallothionein (Mt) complex, following proximal microinjection, ranged between 17 (Cd-Mt 0.19 mM) and 8% (Cd-Mt 1.5 mM). It is concluded that luminal Cd uptake by the tubular epithelium depends markedly on the chemical form of Cd and, when present, occurs mostly or exclusively in proximal tubules.

Preparation and thermal decomposition of copper(II), zinc(II) and cadmium(II) chelates with 8-hydroxyquinoline

When the compounds are heated in an inert atmosphere it can be verified the consecutive partial sublimation, fusion, partial volatilization and partial thermal decomposition of the anhydrous complexes. When in an oxidating atmosphere the above process is only verified to Cu(II) chelates. Anhydrous copper(II) complexes present a monoclinic structure in the b form and the volatilized compound in a a form. Zinc(II) and cadmium(II) hydrated complexes are isomorphous and they present different cell dimensions from those reported previously.

Automated flow-injection method for cadmium determination with pre-concentration and reagent preparation on-line

The spectrophotometric determination of Cd(II) using a flow injection system provided with a solid-phase reactor for cadmium preconcentration and on-line reagent preparation, is described. It is based on the formation of a dithizone-Cd complex in basic medium. The calibration curve is linear between 6 and 300 µg L-1 Cd(II), with a detection limit of 5.4 µg L-1, an RSD of 3.7% (10 replicates in duplicate) and a sample frequency of 11.4 h-1. The proposed method was satisfactorily applied to the determination of Cd(II) in surface, well and drinking waters.

Effects of Cadmium and mercury on the upper part of skeletal muscle glycolysis in mice.

The effects of pre-incubation with mercury (Hg2+) and cadmium (Cd2+) on the activities of individual glycolytic enzymes, on the flux and on internal metabolite concentrations of the upper part of glycolysis were investigated in mouse muscle extracts. In the range of metal concentrations analysed we found that only hexokinase and phosphofructokinase, the enzymes that shared the control of the flux, were inhibited by Hg2+ and Cd2+. The concentrations of the internal metabolites glucose-6-phosphate and fructose-6-phosphate did not change significantly when Hg2+ and Cd2+ were added. A mathematical model was constructed to explore the mechanisms of inhibition of Hg2+ and Cd2+ on hexokinase and phosphofructokinase. Equations derived from detailed mechanistic models for each inhibition were fitted to the experimental data. In a concentration-dependent manner these equations describe the observed inhibition of enzyme activity. Under the conditions analysed, the integral model showed that the simultaneous inhibition of hexokinase and phosphofructokinase explains the observation that the concentrations of glucose-6-phosphate and fructose-6-phosphate did not change as the heavy metals decreased the glycolytic flux.

Dispersive liquid-liquid microextraction for the simultaneous separation of trace amounts of zinc and cadmium ions in water samples prior to flame atomic absorption spectrometry determination

In the proposed method, carbon tetrachloride and ethanol were used as extraction and dispersive solvents. Several factors that may be affected on the extraction process, such as extraction solvent, disperser solvent, the volume of extraction and disperser solvent, pH of the aqueous solution and extraction time were optimized. Under the optimal conditions, linearity was maintained between 1.0 ng mL-1 to 1.5 mg mL-1 for zinc and 1.0 ng mL-1 to 0.4 mg mL-1 for cadmium. The proposed method has been applied for determination of trace amount of zinc and cadmium in standard and water samples with satisfactory results.

Application of cloud point preconcentration and flame atomic absorption spectrometry for the determination of cadmium and zinc ions in urine, blood serum and water samples

A simple, sensitive and selective cloud point extraction procedure is described for the preconcentration and atomic absorption spectrometric determination of Zn2+ and Cd2+ ions in water and biological samples, after complexation with 3,3',3",3'"-tetraindolyl (terephthaloyl) dimethane (TTDM) in basic medium, using Triton X-114 as nonionic surfactant. Detection limits of 3.0 and 2.0 µg L-1 and quantification limits 10.0 and 7.0 µg L-1were obtained for Zn2+ and Cd2+ ions, respectively. Relative standard deviation was 2.9 and 3.3, and enrichment factors 23.9 and 25.6, for Zn2+ and Cd2+ ions, respectively. The method enabled determination of low levels of Zn2+ and Cd2+ ions in urine, blood serum and water samples.