Perturbation of monovalent cation composition in Ulva lactuca by cadmium, copper and zinc

Discs of thallus cut from the macroalga Ulva lactuca were incubated in filtered seawater containing cadmium, zinc, copper or cobalt (30 m). The metal uptake rates differed for each metal in the order Cu > Zn > Cd > Co. Exposure of the macroalga to metals resulted in a disruption of intracellular monovalent cation composition. Intracellular potassium was irreversibly lost and sodium was accumulated by cadmium- or copper-treated U. lactuca, which was assumed to indicate irreversible disruption of the plasmalemma. Exposure to zinc caused an increase in sodium concentrations, whereas potassium concentrations were not significantly different from the controls, suggesting that the integrity of the plasmalemma had been maintained at the zinc concentration used. Intracellular magnesium was also lost from copper-treated algae, which again indicated a loss of integrity of the cell membrane.     

A new method to detect cadmium uptake in protoplasts

The mechanism for cadmium (Cd²⁺) uptake into the cytosol of protoplasts from 5- to 7-day-old wheat seedlings (Triticum aestivum L. cv. Kadett) was investigated by a new method, using fluorescence microscopy and the heavy metal-specific fluorescent dye, 5-nitrobenzothiazole coumarin, BTC-5N. Cadmium fluorescence gradually increased in the cytosol of shoot and root protoplasts upon repeated additions of CdCl₂ to the external medium, reflecting an uptake of Cd²⁺. The uptake was inhibited by calcium and potassium chloride, as well as by Verapamil and tetraethylammonium (TEA), inhibitors of calcium and potassium channels, respectively. Calcium competitively inhibited the cadmium uptake. The metabolic inhibitors vanadate and dinitrophenol partly inhibited the uptake, suggesting it was dependent on membrane potential. The results indicate that cadmium is taken up by channels permeable to both calcium and potassium. The total uptake of cadmium into the protoplasts was also detected by unidirectional flux analyses using ¹⁰⁹Cd²⁺, and showed approximately the same maximal concentration of Cd²⁺ as the fluorescence measurements. By combining the two methods it is possible to detect both uptake into the cytosol and into the vacuole.Abbreviations BTC-5N, AM Acetoxymethyl ester of 5-nitrobenzothiazole coumarin - DNP 2,4-Dinitrophenol - TEA Tetraethylammonium     

Effects of cadmium and copper on zinc transport kinetics by isolated renal proximal cells

Zinc, cadmium, and copper are known to interact in many transport processes, but the mechanism of inhibition is widely debated, being either competitive or noncompetitive according to the experimental model employed. We investigated the mechanisms of inhibition of zinc transport by cadmium and copper using renal proximal cells isolated from rabbit kidney. Initial rates of⁶⁵Zn uptake were assessed after 0.5 min of incubation. The kinetics parameters of zinc uptake obtained at 20°C were a J_max of 208.0±8.4 pmol· min⁻¹·(mg protein)⁻¹, aK _m of 15.0±1.5 μM and an unsaturable constant of 0.259±0.104 (n=8). Cadmium at 15 μM competitively inhibited zinc uptake. In the presence of 50 μM cadmium, or copper at both 15 and 50 μM, there was evidence of noncompetitive inhibition. These data suggest that zinc and cadmium enter renal proximal cells via a common, saturable, carrier-mediated process. The mechanisms of the noncompetitive inhibition observed at higher concentrations of cadmium or with copper require further investigation, but may involve a toxic effect on the cytoskeleton.     

Coordinated cations in dipicolinato complexes of divalent metal ions

Several salts of alkali, alkaline earth metal and organic ammonium cations of a complex anion [ML₂]²⁻ {Where L = dipicolinato dianion, M = copper(II), nickel(II) and zinc(II)} are prepared. The coordination effect of [ML₂]²⁻ with the cations such as sodium, potassium, calcium, magnesium, and organic cations namely diammonium cation of 1,5-pentanediamine, diammonium cation of 1,8-octyldiamine, mono ammonium cation of 4-aminobenzylamine are studied by determining their X-ray crystal structures. Depending on the nature of cations, four different types of structures are obtained. When calcium is the cation a polymeric structure with calcium ions bridging the [ML₂]²⁻ is observed. The salts having sodium and potassium cations form polymeric chain like structures by oxo and aqua bridges. In the case of magnesium, the hydrated form of magnesium cations coordinates to [ML₂]²⁻. The organic ammonium salts of [ML₂]²⁻ have the structural features of conventional ionic complexes. These salts easily exchange cations. The organic ammonium salts of [ML₂]²⁻ decomposes to give the corresponding metal oxides at relatively low temperature range 300-450 °C.     

Thiobacillus ferrooxidans response to copper and other heavy metals: growth, protein synthesis and protein phosphorylation

Respirometric experiments demonstrated that the oxygen uptake by Thiobacillus ferrooxidans strain LR was not inhibited in the presence of 200 mM copper. Copper-treated and untreated cells from this T. ferrooxidans strain were used in growth experiments in the presence of cadmium, copper, nickel and zinc. Growth in the presence of copper was improved by the copper-treated cells. However, no growth was observed for these cells, within 190 h of culture, when cadmium, nickel and zinc were added to the media. Changes in the total protein synthesis pattern were detected by two-dimensional polyacrylamide gel electrophoresis for T. ferrooxidans LR cells grown in the presence of different heavy metals. Specific proteins were induced by copper (16, 28 and 42 kDa) and cadmium (66 kDa), whereas proteins that had their synthesis repressed were observed for all the heavy metals tested. Protein induction was also observed in the cytosolic and membrane fractions from T. ferrooxidans LR cells grown in the presence of copper. The level of protein phosphorylation was increased in the presence of this metal.     

Effects of essential divalent metals on carcinogenicity and metabolism of nickel and cadmium

Interactions between the physiologically essential metals calcium, magnesium, and zinc and the carcinogenic metals nickel and cadmium were investigated to help elucidate the mechanisms of action of the carcinogenic metals. Bioassay studies revealed several significant findings, including: (1) the ability of magnesium and calcium to inhibit nickel-induced elevation of pulmonary adenoma incidence in strain A mice; (2) the ability of magnesium, but not of calcium, to prevent cadmium-induced subcutaneous sarcoma formation; and (3) the ability of magnesium, but not of calcium, to inhibit nickel-induced muscle tumor formation. Biochemical studies indicated a direct relationship between the antitumorigenic potential of magnesium and the capacity of this metal to: (1) inhibit nickel and cadmium uptake by the target tissues in vivo; (2) inhibit nickel-induced disturbances in DNA synthesis in vivo; (3) inhibit nuclear and cytosolic uptake of nickel by the target tissue cells in vivo; and (4) inhibit nickel and cadmium binding to DNA in vitro. Calcium, which in most cases did not prevent carcinogenesis, had no consistent influence on the uptake of carcinogenic metals or their biochemical effects in the target tissues. Magnesium and zinc, but not calcium, were also found to attenuate the acute toxic effects of nickel, indicating a possible correlation between prevention of acute effects and reduction in tumorigenicity. Zinc, which antagonizes cadmium tumorigenicity in the rat testis, was found to reduce markedly cadmium uptake into isolated testicular interstitial cells. Also, zinc was found to inhibit strongly cadmium binding to DNA in vitro.     

Ammonium-stimulated,sodium-dependent uptake of glutamine in Bacillus pasteurii

The uptake of glutamine was studied in Bacillus pasteurii DSM 33. Only one uptake system was detected in the concentration range studied (between 1 and 100 M glutamine) which exhibited Michaelis-Menten saturation kinetics, with an apparent K _t of 10.7 (±3.5) M glutamine. The uptake was sodium-dependent (apparent K _t=0.2 mM Na⁺); none of several monovalent cations tested was able to replace sodium in the uptake reaction. Ionophores interfering with proton, sodium or potassium gradients across membranes strongly inhibited uptake of glutamine. Low uptake rates correlating with low potassium content and an acidic cytoplasm were measured in cells grown at high ammonium¹ concentrations. Ammonium and other permeant amines as well as potassium stimulated the uptake reaction in these cells, leading to an increase of up to 100-fold in V _max without affecting the affinity of the uptake system. In cells grown at low concentrations of ammonium, an alkaline cytoplasm and both high glutamine uptake activities and potassium content were measured; the uptake reaction was not further stimulated by permeant amines or potassium in such cells. Growth of the strain was inhibited by Tris at high concentrations; this inhibition was relieved by the addition of increasing amounts of ammonium.Abbreviations CCCP carbonylcyanide-m-chlorphenylhydrazone - DCCD dicyclohexylcarbodiimide This work is dedicated to Prof. Dr. H. Kaltwasser on the occasion of his 60th birthday     

Element Status in Different Breeds of Dogs

The serum levels of copper, zinc, iron, manganese, nickel, cadmium, cobalt, sodium, potassium, calcium, and magnesium were determined in seven different breeds of dogs: Pointer, Poodle, Setter, Labrador Retriever, Golden Retriever, German Shepherd, and Mallinois. Only slight variations were found among the different breeds, and the results presented in this study can be used for laboratory studies in veterinary science.     

Phytoremediation of heavy metals and nutrients by the Sagittaria montevidensis into an anthropogenic contaminated site at Southern of Brazil

Abstract

The evaluation of plants occurring naturally at contaminated environments are essential for applying this species in remediation techniques. In this context, the Sagittaria montevidensis with potential for phytoremediation was studied at an anthropogenic polluted stream in southern Brazil. The nutrients and heavy metal content were determined in the phytomass. The phytoremediation indexes were evaluated such as bioconcentration factor (BCF), translocation factor (TF), plant effective number (PEN), and potential phytoremoval (mg m^?2). The S. montevidensis was then detected as presenting natural phytoextraction ability for potassium and calcium elements and also demonstrated rhizofiltration potential for phosphorus, manganese, aluminum, vanadium, sulfur, iron, arsenic, copper, magnesium, zinc, sodium, lead, cadmium, nickel, chromium, considering its ability of bioaccumulating these contaminants and retain high levels in the roots. The highest potential for bioremoval (mg m^?2) of the S. montevidensis was detected for potassium and calcium (recommending thus the use for phytoextraction) and for aluminum, phosphorus, iron, magnesium, sulfur, and sodium, along with heavy metals (recommended for rhizofiltration). The S. montevidensis decontamination ability, along with its biomass production and its adaptability represents a great advance in order to the recovery of this degraded area and possible application in other contaminated watercourses in Brazil.     

Experimental Articles

Volcanic ash (Karymskii Volcano, Kamchatka) stimulated growth of the bacterium Rhodovulum sp. A-20s. The interaction between ash, water, media, and bacteria resulted in changes in the chemical composition of the solutions and ash. The ash-water interaction resulted in release of calcium to the solution, as well as in an increase in the proportions of sodium and calcium among the exchange cations of ash. As a result of the ash-medium interaction, calcium and copper were released to the solution; the exchange sodium cations were substituted by calcium and potassium. As a result of the ash-bacteria interaction, the content of copper in the solution decreased, and the exchange cations of calcium and sodium were actively substituted by potassium and magnesium. An increase in the magnesium content among the exchange cations of ash was especially apparent. The products of bacterial metabolism formed mineral-organic complexes with the ash substrate. The data obtained indicate the biogenic transformation of ash, which may lead to the initial phase of formation of clay minerals from volcanic ashes.     

Cations in Hemolymph and Alimentary Tract Tissues of Healthy and Milky Diseased European Chafer (Amphimallon majalis) Larvae

A study was made of certain cations present in hemolymph and alimentary tract tissues of healthy and diseased European chafer larvae and the spores of Bacillus popilliae collected from diseased hemolymph. The major ions found in the hemolymph, in order of decreasing abundance, were potassium, magnesium, sodium, and calcium. Hemolymph of diseased larvae contained relatively higher concentrations of sodium, potassium, magnesium, iron, and zinc than hemolymph of healthy larvae. Concomitantly, the concentrations of ions were lower in the mid-gut and anterior intestinal tissues of diseased larvae. Only sodium decreased slightly in the diseased tissues of the rectum and rectal sac; other ions remained unchanged or increased. Little or no manganese or copper was detected in the hemolymph or tissues. The major cations of spores of B. popilliae were sodium, calcium, and magnesium. Small amounts of potassium, manganese, copper, iron, and zinc were detected in the spores. Based on calcium and dipicolinic acid determinations of the spores, sufficient calcium was found to allow for the formation of calcium dipicolinate in the expected concentrations.     

The effect of ions, ion channel blockers, and ionophores on uptake of vitellogenin into cockroach follicles

Since calcium plays an important role in vitellogenin binding and uptake in Nauphoeta cinerea and because calcium channels have been described in follicles of this species, we investigated the effect of various ions, ionophores, and ion channel blockers on vitellogenin uptake in vitro. Calcium significantly stimulated vitellogenin uptake; this effect could be substituted best by barium and less well by strontium and magnesium. The stimulatory effect of calcium, and to a certain extent also that of barium, was dependent on the vitellogenin concentration, whereas the effect of strontium and magnesium was not. In the presence of calcium, vitellogenin uptake was inhibited by barium, strontium, and magnesium as well as by the transition elements nickel, cobalt, and zinc, but not by manganese which had a stimulatory effect. Valinomycin, verapamil, tetraethylammonium, and atropine reduced vitellogenin uptake, while amiloride and ouabain were ineffective. Our results indicate that calcium inward (and possibly potassium outward) fluxes play an important role in vitellogenin uptake.     

Effect of gibberellic acid on ion uptake selectivity in pea seedlings

Gibberellic acid reduced the uptake of nitrogen and phosphorus relative to the cations, a common reponse in the three pea cultivars studied. In addition, in the cv. Progress, it increased the uptake of calcium relative to magnesium and potassium. No effect in the proportion in which cations are absorbed was noticeable in the other two varieties. Ion uptake is modified by gibberellic acid through its influence on the sink strength of the shoot, the size and geometry of the root system, and the selectivity in uptake. The overall effect may result in a stimulation or an inhibition, depending on the ion considered and the pea cultivar.Abbreviation GA₃ gibberellic acid     

Characterization of the yeast ionome: a genome-wide analysis of nutrient mineral and trace element homeostasis in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Background  

Nutrient minerals are essential yet potentially toxic, and homeostatic mechanisms are required to regulate their intracellular levels. We describe here a genome-wide screen for genes involved in the homeostasis of minerals in Saccharomyces cerevisiae. Using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), we assayed 4,385 mutant strains for the accumulation of 13 elements (calcium, cobalt, copper, iron, potassium, magnesium, manganese, nickel, phosphorus, selenium, sodium, sulfur, and zinc). We refer to the resulting accumulation profile as the yeast 'ionome'.     

Sorption of Heavy Metals to the Filamentous Bacterium Thiothrix Strain A1

A study was undertaken to determine the ability of the filamentous bacterium Thiothrix strain A1 to sorb heavy metals from solution. Cells of Thiothrix strain A1 were harvested, washed, and suspended in solutions of metals. After an equilibration period, biomass was separated from solution and the metal content in acid-digested cells and/or filtrates was determined by atomic absorption spectrophotometry. Sorption of nickel and zinc was very rapid; most of the sorbed metal was bound in less than 10 min. The sorption data for copper fit the Freundlich isotherm, and nickel and zinc data fit biphasic Freundlich isotherms. Sorption of both nickel and zinc was dependent on cell age. Cells harvested 24 h after inoculation sorbed approximately one-half of the amount of metal per gram cell protein than did cells harvested after 48, 72, or 96 h. Calcium and magnesium effectively competed with zinc for binding sites, whereas potassium had only a slight effect on the capacity of cells to sorb zinc. The primary mechanism of metal sorption apparently was ion exchange, because 66 to 75% of nickel or zinc could be desorbed by placing metal-laden cells in a solution of 5 mM CaCl₂. A competition experiment with nickel and zinc indicated that both metals occupied the same sorption sites. The strong chelating agents EDTA and NTA effectively prevented metal uptake, but lactate enhanced the uptake of nickel. Thiothrix strain A1 grown in nickel-containing medium had a relatively low uptake of nickel compared with uptake by resting cells suspended in a simple buffer solution.     

Interaction of heavy metal toxicants with brain constitutive nitric oxide synthase

This study was designed to evaluate thein vitro effects of transition heavy metal cations on activity of constitutive isoform of nitric oxide synthase (cNOS) in rat brain. NOS activity was determined in the cytosolic fractions of rat cerebral hemispheres by conversion of³H-L-arginine to³H-L-citrulline. Different concentrations of mercury (Hg²⁺), nickel (Ni²⁺), manganese (Mn²⁺), zinc (Zn²⁺), cadmium (Cd²⁺), lead (Pb²⁺) and calcium (Ca²⁺) were tested on NOS activity. While all the cations caused inhibition, there were differences in the apparent inhibition constants (Ki) among the cations. With the exception of calcium ion no other cation required preincubation with the enzyme preparation. These results indicate that while calcium ion modulate cNOS activity at regulatory site(s), inhibitory influence of toxic heavy metal cations may be exerted on the catalytic site(s) either by direct binding to it or by interfering with the electron transfer during catalysis.     

The inhibition kinetics of yeast glutathione reductase by some metal ions

Glutathione reductase (GR, type IV, Baker's yeast, E.C 1.6.4.2) is a flavoprotein that catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG) to reduced glutathione (GSH). In this study some metal ions have been tested on GR; lithium, manganese, molybdate, aluminium, barium, zinc, calcium, cadmium and nickel. Cadmium, nickel and calcium showed a good to moderate inhibitory effect on yeast GR. GR is inhibited non-competitively by Zn^{2 +} (up to 2 mM) and activated above this concentration. Ca^{2 +} inhibition was non-competitive with respect to GSSG and uncompetitive with respect to NADPH. Nickel inhibition was competitive with respect to GSSG and uncompetitive with respect to NADPH. The inhibition constants for these metals on GR were determined. The chelating agent EDTA recovered 90% of the GR activity inhibited by these metals.     

Interaction between thapsigargin and ATP4− in the regulation of the intracellular calcium in rat submandibular glands

Rat submandibular glands were digested with crude collagenase, and the intracellular calcium concentration of the cellular suspension was measured using fura-2. In the absence of extracellular magnesium and calcium ([Ca²⁺]_o), ATP had no effect; the response to ATP peaked at 1–2.5 mM [Ca²⁺]_o and was inhibited at 5 mM. One millimolar (mM) extracellular ATP did not increase the leak of LDH or fura-2; 10 m?M Coomassie brilliant blue G specifically inhibited the effect of ATP on [Ca²⁺]_in. Depleting intracellular calcium pools with thapsigargin did not affect the response to ATP. Using a Ca²⁺-free/Ca²⁺ reintroduction protocol, it was shown that ATP and thapsigargin increase the uptake of extracellular calcium. The effect of the two agonists was synergistic. Removal of extracellular sodium inhibited the effect of carbachol on [Ca²⁺]_in and the calcium uptake but potentiated the response to ATP. These results suggest that, after binding to purinergic receptors, extracellular ATP^4- increases [Ca²⁺]_in. ATP^4- does not mobilize thapsigargin-sensitive intracellular calcium pools (among which is the IP₃-sensitive calcium pool) but stimulates the uptake of extracellular calcium by a mechanism inhibited by extracellular sodium, probably by opening a nonselective cation channel. © 1994 Wiley-Liss, Inc.     

Effects of Schistosoma mansoni infection on inorganic elements in the snail Biomphalaria glabrata

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to study element ions in whole bodies of uninfected Biomphalaria glabrata snails and those experimentally infected with larval Schistosoma mansoni trematodes. Infected snails were analysed 8 weeks post-infection. Cohort snails that were left uninfected were analysed at the same time as the infected snails. Sixteen elements (aluminum, boron, barium, calcium, cadmium, copper, iron, potassium, magnesium, manganese, sodium, nickel, lead, selenium, tin and zinc) were found to be present in infected and uninfected whole bodies at concentrations above the detection limit of the ICP-AES analysis. Of these, calcium, cadmium, manganese and sodium were present in significantly higher amounts (Student's t-test, P<0.05) in whole infected versus whole uninfected snails. Variations in the present results compared with other studies reflect intrinsic differences in the larval trematode-snail systems used.     

Nickel enhances telomeric silencing in Saccharomyces cerevisiae

Certain nickel compounds including crystalline nickel sulfide (NiS) and subsulfide (Ni₃S₂) are potent human and animal carcinogens. In Chinese hamster embryo cells, an X-linked senescence gene was inactivated following nickel-induced DNA methylation. Nickel also induced the inactivation of the gpt reporter gene by chromatin condensation and a DNA methylation process in a transgenic gpt+ Chinese hamster cell line (G12), which is located near a heterochromatic region. To determine if nickel can cause gene silencing independently of DNA methylation, based only on the induction of changes in chromatin structure, we measured its effect on gene silencing in Saccharomyces cerevisiae. Growth of yeast in the presence of nickel chloride repressed a telomeric marker gene (URA3) and resulted in a stable epigenetic switch. This phenomenon was dependent on the number of cell doubling prior to selection and also on the distance of the marker gene from the end of the chromosome. The level of TPE (telomeric position effect) increased linearly with elevations of nickel concentration. Addition of magnesium inhibited this effect, but magnesium did not silence the reporter gene by itself. The level of silencing was also assessed following treatment with other transition metals: cobalt, copper and cadmium. In the sublethal range, cobalt induced similar effects as nickel, while copper and cadmium did not change the basal level of gene expression. Silencing by copper and cadmium were evident only at concentrations of those metals where the viability was very low.