A link between copper and dental caries in human teeth identified by X-ray fluorescence elemental mapping

Quantitative X-ray fluorescence imaging of sections of human teeth revealed an increased concentration of copper and zinc in carious regions of dentine compared with unaffected portions of the tooth. Higher-resolution images provided strong evidence that the copper was transported and localized mainly in the dentinal tubules. While similar levels of zinc were found in these areas and concentrated in the tubules, zinc was also more evident in the hydroxyapatite, and the increase in zinc levels compared with the levels in background (normal) areas was less than that for copper. These results suggest a role for copper and zinc in the formation and progression of dental caries and present a potential point of intervention for treatment. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Dedicated to the memory of the late Harold Eastgate.     

Tooth Element Levels Indicating Exposure Profiles in Diabetic and Hypertensive Subjects from Mysore,India

Element contents of teeth elucidate exposure nature, but less is known about association of tooth element concentrations of diabetics and hypertensives with exposure profile. Present study aims to estimate copper, chromium, iron, zinc, nickel, and lead concentrations in the permanent teeth of control, diabetic, and hypertensive subjects from Mysore. The results show that lead levels of teeth (Pb-T) are higher in the hypertensives and diabetics, whereas copper levels of teeth (Cu-T) are lower in the hypertensives and users of stainless steel utensils than that of controls and users of mixed utensils. The elevated Cu-T levels found in the users of mixed utensils that being made of several metals are ascribed to leaching effect of sour and spicy food of Indian cuisine. The element levels were influenced by diet (Zn-T), place of living, sex and income (Pb-T) of the subjects, but not by age, drinking water from different sources, and certain habits viz., smoking, alcohol consumption, chewing betel, and nut. Thus, it is evident that high Pb-T and low Cu-T levels may be related with diabetes and hypertension and high Pb-T and Cu-T levels, respectively, in the urbanites, and the users of mixed utensils may show different exposure profiles from environment and utensils.     

Accumulation of copper and zinc from liquid manure in agricultural soils and crop plants

In Northern Italy it is a common practice to utilise slurries and other manure from intensive animal farming to fertilise agricultural soils. Due to the relatively high copper and zinc contents of these materials, this practice could lead to contamination of soils and the crops grown on them. In this study we have evaluated the extent of copper and zinc contamination of soils subjected to different levels of fertilisation with liquid manure and the copper and zinc concentrations in the edible tissues of three crops (maize, sugar beet and lucerne) grown on the same soils. There was a direct correlation between soil copper and zinc contents and the levels of application of animal wastes and copper concentrations were high enough to represent a risk, according to current European legislation. The metal contents in the edible tissues of the three crops were relatively low and variable, but showed no clear correlations with the intensity of liquid manure applications. Overall, there was no risk of contamination of the food chain, as all concentrations were well below levels considered to be toxic to animals.     

Selective extraction of metals from zinc concentrate by association of chemolithotrophic bacteria

Ability for selective extraction of copper and zinc from zinc concentrate using association of chemolithotrophic bacteria was investigated. In the presence of bacterial association, the rate of leaching of zinc, copper, and iron was increased 3-fold, 4–5-fold, and 2-fold, respectively. The results indicate the maximum dissolution rate for zinc, then followed by copperand iron. It was revealed that addition of Fe³⁺ 2 g/l resulted in reduction of iron leaching and in 3-fold increase of leaching rate of copper at constant dissolution rate of mineral zinc. It is suggested that the intensification of copper leaching is connected with the activity of sulfur-oxidizing bacteria able to activate the mineral surface via elimination of passivation layer of elemental sulfur. It was concluded that sulfur-oxidizing bacteria play a significant role in copper leaching from zinc concentrate. A unique strain of mesophile sulfur-oxidizing bacteria was isolated from leaching pulp of zinc concentrate; in the perspective, it may serve as efficient candidate for performing of selective extraction of copper from zinc concentrate.     

Selective leaching of zinc from copper-zinc concentrate

Biooxidation of copper-zinc concentrate with the use of consortia of mesophilic and moderately thermophilic acidophilic chemolithotrophic microorganisms was studied. Pyrrhotite, sphalerite, and chalcopyrite were the main sulfide minerals of the concentrate. The possibility in principal of complete selective leaching of zinc from sulfide concentrate coupled with minimal recovery of copper (less than 20%) was demonstrated. Selective leaching of zinc could be caused by galvanic interactions between minerals of the concentrate during the biooxidation. The results can be used as the basis for the development of the technologies for production of grade copper concentrate not containing zinc from sulfide copper-zinc concentrate obtained from refractory ores.     

Effect of anions on selective solubilization of zinc and copper in bacterial leaching of sulfide ores

Bacterial leaching of sulfide ores using Thiobacillus ferrooxidans, Thiobacillus thiooxidans, or a combination of the two was studied at various concentrations of specific anions. Selective zinc and copper solubilization was obtained by inhibiting iron oxidation without affecting sulfur/sulfide oxidation. Phosphate reduced iron solubilization from a pyrite (FeS(2))-sphalerite (ZnS) mixture without significantly affecting zinc solubilization. Copper leaching from a chalcopyrite (CuFeS(2))-sphalerite mixture was stimulated by phosphate, whereas chloride accelerated zinc extraction. In a complex sulfide ore containing pyrite, chalcopyrite, and sphalerite, both phosphate and chloride reduced iron solubilization and increased copper extraction, whereas only chloride stimulated zinc extraction. Maximum leaching obtained was 100% zinc and 50% copper. Time-course studies of copper and zinc solubilization suggest the possibility of selective metal recovery following treatment with specific anions.     

Concentration of selected elements in the roots and crowns of both primary and permanent teeth with caries disease

We examined the differences between the concentrations of chemical elements in caries-changed primary teeth and permanent ones with a division into the root and the crown. The study comprised 27 children aged from 4 to 11 yr and 36 adults aged from 36 to 71 yr. We examined the elements with the total reflection X-ray fluorescence method. The lowest concentrations of calcium, manganese, strontium, lead, and copper were in the roots of primary teeth compared to the roots of permanent ones. The calcium, nickel, zinc, lead, and copper concentrations were significantly higher in the roots of primary teeth than in the roots of permanent teeth. However, the zinc concentration was higher both in the root and crown of primary teeth than in permanent teeth. On the basis of our investigations, we can conclude that the content of some elements (manganese, copper, strontium, and lead) is higher in caries permanent teeth than in primary ones. The nickel and zinc concentrations are higher in the teeth of the children than the adults. However, the content of other elements (calcium, chromium, iron) is similar in both kinds of teeth.     

A two-stage technology for bacterial and chemical leaching of copper-zinc raw materials by Fe<Superscript>3+</Superscript> ions with their subsequent regeneration by chemolithotrophic bacteria

A two-stage technology for bacterial and chemical leaching of nonferrous metals in a specifically designed laboratory unit has been proposed. At the first stage of leaching, ferric iron formed during the second stage of oxidation of Fe²⁺ ions by mesophilic chemolithotrophic microorganisms was used. The optimal parameters of the first stage of the process (flow rate, temperature, and the process duration) were 2 l/h, 75°C, and 24 h, respectively. The results of testing of the two-stage technology for leaching copper-zinc raw materials indicated that the depth of zinc and copper leaching can be increased from 70 to 93% and from 40 to 58.8%, respectively, and the process duration can be reduced from 120 to 24 h as compared to the commonly used one-stage technology.     

The metabolism of metals in rat placenta

The status and transfer of metals across the rat placenta were studied by subcellular and molecular fractionations of this organ at 2 and 24 h after iv injection of radiolabeled metals. The soluble and nuclear fractions showed higher contents of copper and zinc, whereas most of the nickel was associated with the soluble fraction. Cadmium was almost evenly distributed between the microsomal and nuclear fractions. Gel filtration of the soluble fractions showed nickel associated with an unknown low molecular weight form; zinc with high molecular weight proteins; copper with metallothionein, ceruloplasmin, and high molecular weight proteins; and cadmium with high molecular weight proteins and metallothionein.     

Leaching of nonferrous metals from copper converter slag with application of acidophilic microorganisms

The leaching process of copper and zinc from copper converter slag with ferric iron in sulfuric acid solutions obtained using the association of acidophilic chemolithotrophic microorganisms was investigated. The best parameters of chemical leaching (temperature 70°C, an initial concentration of ferric iron in the leaching solution of 10.1 g/L, and a solid phase content in the pulp of 10%) were selected. Carrying out the process under these parameters resulted in the recovery of 89.4% of copper and 39.3% of zinc into the solution. The possibility of the bioregeneration of ferric iron in the solution obtained after the chemical leaching of slag by iron-oxidizing acidophilic chemolithotrophic microorganisms without inhibiting their activity was demonstrated.     

Long-term zinc and iron supplementation in children of short stature: effect of growth and on trace element content in tissues.

We evaluated the effect of one year of supplementation with iron plus zinc (12 mg/day of Fe+++ and 12.5 mg/day of Zn++), zinc alone (12.5 mg/day of Zn++) and placebo on growth and on the iron, zinc, copper and selenium tissue contents in 30 well-selected children of short stature (16 M and 14 F; 4-11 years old). Before and after supplementation, we measured the concentrations of iron, transferrin, ferritin, zinc and copper in serum, of zinc in erythrocytes and leukocytes, and of zinc, copper and selenium in hair, as well as glutathione peroxidase activity in erythrocytes. Before supplementation, ferritin and serum, erythrocyte and hair zinc contents were significantly lower than in age-matched controls, while the other measured indices were in the normal range. Iron plus zinc supplementation caused an improvement in growth rate in all subjects, i.e., the median Z-score increased from -2.22 +/- 0.45 to -0.64 +/- 0.55; (p < 0.01). In the zinc-supplemented group, only the subjects whose ferritin levels were higher than 20 ng/L before supplementation showed a similar improvement of growth rate. Iron plus zinc supplementation could be a reasonable treatment in short, prepubertal children affected by marginal zinc and iron deficiency.     

Chelation and intercalation: complementary properties in a compound for the treatment of Alzheimer's disease

Selective application of metal chelators to homogenates of human Alzheimer's disease (AD) brain has led us to propose that the architecture of aggregated beta-amyloid peptide, whether in the form of plaques or soluble oligomers, is determined at least in part by high-affinity binding of transition metals, especially copper and zinc. Of the two metals, copper is implicated in reactive oxygen species generating reactions, while zinc appears to be associated with conformational and antioxidant activity. We tested the copper chelators trientine, penicillamine, and bathophenanthroline for their ability to mobilize brain Abeta as measured against our benchmark compound bathocuproine (BC). All of these agents were effective in solubilizing brain Abeta, although BC was the most consistent across the range of AD brain tissue samples tested. Similarly, all of the copper chelators depleted copper in the high-speed supernatants. BC alone had no significant effect upon zinc levels in the soluble fraction. BC extraction of brain tissue from C100 transgenic mice (which express human Abeta but do not develop amyloid) revealed SDS-resistant dimers as Abeta was mobilized from the sedimentable to the soluble fraction. NMR analysis showed that, in addition to its copper chelating properties, BC interacts with Abeta to form a complex independent of the presence of copper. Such hybrid copper chelating and "chain breaking" properties may form the basis of a rational design for a therapy for Alzheimer's disease.     

Microbial leaching of zinc concentrate in fresh‐water microcosms: Comparison between aerobic and oxygen‐limited conditions

Microbially mediated leaching and solubilization of zinc ore concentrate by native aquatic microbial communities incubated under aerobic and oxygen‐limited conditions were examined in static microcosms consisting of stream sediment and water. Sterile controls provided information on abiotic sulfide oxidation and leaching of zinc, lead, cadmium, and copper. The flux of these heavy metals from the sediments to the water column was greatest under biotic oxygen‐limited conditions. When calculated as the percentage of total metal available in zinc concentrate‐amended microcosms, the order of metal solubilization under oxygen‐limited conditions was lead, copper, zinc, and cadmium. Under biotic aerobic conditions, the order of solubilization was zinc, lead, cadmium, and copper. This study indicates that aquatic heterotrophs are capable of leaching and solubilizing metallic sulfides under conditions of neutral to slightly acidic pH and are effective in releasing heavy metals to the water column under oxygen‐limited conditions.     

Metallothionein in kidney and liver of the macular mouse as an animal model of Menkes' kinky hair disease

The tissue copper and metallothionein-Cu (MT-Cu) content of kidney and liver were measured in mutant (hemizygous macular male and homozygous macular female), heterozygous macular female and normal mouse. The tissue copper and MT-Cu contents in kidneys from 7-8 day mutants and heterozygotes were significantly greater than those of the normal kidney. Marked elevations in kidney copper and MT-Cu contents were also observed in the 8-9 week mutant (which achieved long-term survival with a single dose of subcutaneous copper administered at day 7) and in the heterozygote. The L-[35S]cystine incorporation experiments also revealed an abnormal synthesis of renal MT in the 8-9 week mutant and in the heterozygote. In contrast to kidney Cu levels, the tissue copper and MT-Cu contents of 7-8 day normal livers were extremely high, whereas the tissue copper and MT-Cu contents of mutant and heterozygote livers were extremely low. The tissue copper contents of livers of 8-9 week mutants and heterozygotes were slightly low compared to normal, and the MT-Cu contents of livers of the 8-9 week mouse were extremely low in all groups. In contrast to the changes in copper content, the changes in tissue zinc and MT-Zn contents in kidney and liver were slight in the 7-8 day and 8-9 week mouse.     

Changes in selenium, zinc, copper and cadmium contents in human milk during the time when selenium has been supplemented to fertilizers in Finland

Sodium selenate has been supplemented to all agricultural fertilizers used in Finland since 1984. We followed the changes in selenium, cadmium, zinc and copper content in Finnish human milk between the years 1987 and 1993-1995. A total of 257 milk samples was collected, four weeks after delivery, in two areas: In Helsinki, an urban area, and in Kuopio, a rural area, where elevated copper concentrations have been found in the bedrock. Direct atomic absorption spectrophotometric methods without digestion were used for the analyses. The dependence of trace element content on study time, living area, smoking habits, fish eating frequency, and parity of mothers was studied by analysis of covariance. Inter-element correlations and correlations with mothers' age and fat content in milk were studied by partial correlation. Significant increases were observed in mean selenium (16.4 microg/l and 18.9 microg/l, p < 0.001) and in fat contents (3.4% and 4.0%, p < 0.001), whereas significant decreases were seen in mean zinc (3.00 mg/l and 1.47 mg/l, p < 0.001), copper (0.52 mg/l and 0.43 mg/l, p < 0.001) and cadmium contents (0.095 microg/l and 0.062 microg/l, p < 0.01). In 1987, zinc had a positive correlation with copper and fat. Copper correlated inversely with the mothers' age. In 1993-1995, selenium correlated positively with copper, and zinc correlated inversely with mothers' age. Mothers living area had an effect on copper content in milk. Our results confirm that selenium supplementation to fertilizers in Finland has increased the selenium level in human maternal milk and most likely it also has an effect on the zinc and copper concentrations in maternal milk.     

Ferric Leaching of Bulk Sulfidic Concentrates with Biologically Generated Solution

Applied Biochemistry and Microbiology - The leaching of nonferrous metals from copper–zinc and copper–nickel sulfidic concentrates with a ferric sulfate solution obtained via microbial...     

An effect of zinc deficiency on dental caries.

Rat pups suckled by dams fed a zinc-deficient diet developed higher levels of dental caries following a caries-test challenge than pups suckled by dams fed a zinc-adequate diet. The zinc deficient treatment was administered during the mineralization stage of tooth development before the molars erupted. The data shows that suboptimal zinc nutriture was associated with an increase in dental caries.Fluoride, a trace element, is recognized as a factor in preventing dental caries and its use has had a significant impact on dental health in this country. However, the possible roles of other trace elements have not been closely examined. Zinc is a trace element important to bone mineralization as well as in general nutrition.The effects on dental caries produced by the addition of zinc to rat diets have been reported (1, 2, 3). In those investigations, however, zinc supplements were added to diets that were adequate in zinc. Moreover, zinc supplements were fed after the teeth had appeared in the oral cavity. Because the critical period of tooth maturation occurs before eruption (4), post-eruptive zinc supplements probably should not markedly influence the development and, specifically, the mineralization of the tooth. Therefore, we investigated the influence of pre-eruptive zinc deficiency on caries development in rats.     

Effects of copper and cadmium on heavy metal polluted waterbody restoration by duckweed (Lemna minor).

Aquatic plants have been identified as a potentially useful group for accumulating and bioconcentrating heavy metals. In the study, we investigated changes in the contents of soluble protein and photosynthetic pigments as well as the activity of antioxidant enzymes caused by copper sulfate and cadmium dichloride, respectively in duckweed (Lemna minor) during concentration-dependent exposure (0.05-20 mg l(-1)) to metal salt. The results demonstrated that exposure to high concentration heavy metals (Cu>10 mg l(-1), Cd>0.5 mg l(-1)) could result the disintegration of antioxidant system in duckweed. Also, the significant decrease of contents of soluble protein and photosynthetic pigments was observed to high-level metal stress. Additionally, cadmium was found to be more toxic than copper on plants. The outcome of this study corroborate that Lemna minor is a suitable candidate for the phytoremediation of low-level copper and cadmium contaminated waterbody.     

Reference ranges of copper and zinc and the prevalence of their deficiencies in an Arab population aged 15-80 years

Serum concentrations of copper and zinc were measured by flame atomic absorption spectrophotometry in 560 Kuwaitis aged from 15 to 80 yr who were in apparent good health to establish reference ranges and determine the prevalence of the deficiency of the trace metals. Zinc/copper ratios were derived by calculation. Because the mean +/- SD (microM) for copper in females (24.9 +/- 7) was significantly higher (p<0.0001) than in males (21.0 +/- 5.8) and vice versa for zinc (17.0 +/- 3.5 [males] vs 15.5 +/- 3.4 [females]) and zinc/copper ratios (0.87 +/- 0.28 [males] vs 0.67 +/- 0.27 [females]), gender-specific reference ranges were established in addition to reference ranges for the total population. The reference range for zinc was closer to those reported for other populations than was copper. Body mass index (BMI) and copper values were lower and the zinc/copper ratio was higher in the young (15-24 yr) compared to the older subjects. Copper concentrations were positively associated with BMI values (r=0.302, p<0.0001). Smokers had significantly lower (p=0.011) BMI than nonsmokers. The prevalence of copper and zinc deficiency, 0.36% and 0.53%, respectively, was low. Generally, the values for serum copper and zinc obtained for the Kuwaiti population studied suggest adequate dietary intake of the trace metals.     

Chemical leaching of copper-zinc concentrate with ferric iron biosolution

The process of leaching of copper-zinc concentrate with a solution containing biogenic iron, which is a product of the metabolism of iron-oxidizing microorganisms, was studied. The dependence of leaching rate of metals on temperature and pH was determined. It was shown that up to 98% of zinc and 70% of iron could be removed from the concentrate, while up to 7 and 4 g/L of zinc and copper, respectively, were accumulated in the liquid phase, which was sufficient for metal recovery. It was established that a copper concentrate with copper content up to 16% and only 0.5% of zinc could be obtained after chemical leaching for 340 min at 80°C.