SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
The trace metals represent an extremely small part of the total mass of the organism. In spite of this, these elements appear to play major roles in metabolism. At the level of the hematopoietic system, specific roles can be identified for iron, copper, zinc, and cobalt. Other trace metals appear to play less clearly defined roles in hematopoiesis but clearly are involved by virtue of a number of interactions at the level of absorption, intermediary metabolism, or modulation of toxicity. Still other trace metals, such as lithium, appear to have a therapeutic role in altering production of granulocytes, by an as yet unidentified mechanism.
Trace metals and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental co-contaminants and the trace metals could influence the carcinogenicity of the PAHs by altering their extent of induction of cytochromes P4501A1, 1A2, and 1B1 (CYP). Studies in cell lines from humans, rodents, chickens, and fish, and in cell culture generally indicate that trace metals diminish the inductive potency of PAHs for these CYPs. The extent of the effect is species-, metal-, PAH-, and metal dose-dependent. Both transcriptional and post-translational mechanisms are involved in the trace metal-mediated down regulation of the CYP1 forms. The latter mechanism incorporates induction of heme oxygenase-1 by the metals, with resultant heme catabolism. Thus, trace metals could diminish the carcinogenicity of PAHs.
Airborne particulate trace metals have important health implications. As a consequence, their concentrations are increasingly monitored in many urban locations worldwide. In this study, fine atmospheric particles (PM(2.5)) were collected in Singapore over a period of 83 consecutive days during 2000, and analysed to determine the concentration of trace elements using ICP-MS. Altogether, eighteen airborne trace metals were quantified: Al, Ag, Ba, Cd, Cr, Co, Cu, Fe, Ga, Li, Mn, Ni, Pb, Sr, Zn, V, Si, and Ti. While Li was the least abundant trace metal with a mean concentration of 0.2 ng m(-3), Zn showed the maximum mean concentration of 279.1 ng m(-3). Calculation of enrichment factors indicated that the elements Pb, Zn, Cd, V, Ni, Cr, and Cu were enriched by factors of 30 to 5000 relative to their natural abundance in crustal soil. The extent of metal pollution in the study area was assessed by comparing the measured concentrations to those reported in the literature for a selected number of urban sites in other parts of the world. Factor analysis was used to identify the major sources affecting particulate air pollution in Singapore. The sources that contribute to the loading of trace metal-bearing aerosols in the Singapore urban atmosphere include fuel oil-fired power plants, metal processing industry, land reclamation and construction activities, municipal solid waste incinerators, and traffic emissions.
In this study we investigated the effects of competing trace metals and Ca2+ on Cd(II), Pb(II), and Cu(II) complexation by humic acid extracted from groundwater in Orange County, California. Two types of titration experiments were conducted, those using a single metal and those in which the humic acid had been preequilibrated with a competing metal (either a trace metal or Ca2+). The labile metal concentration in the titration was determined by differential pulse polarography (DPP). Results show the different effects of competing trace metal ions and the effect of Ca2+. Both trace metals and Ca2+ do not compete effectively with Cd(II) complexation. While no effects of Cu(II) on Pb(II) complexation were observed, the presence of Cd(II) appeared to slightly enhance the binding between Pb(II) and humic acid. The addition of Pb(II) decreased the amount of Cu(II) complexation, but Cd(II) caused a slight increase at the lower concentrations. Calcium, however, decreased the amount of complexation for all three metals. Results indicate that the metals are not necessarily competing for the same sites. Conformational changes that occur when trace metals bind to the different sites may cause this competing or enhanced effect. Since Ca(II) is introduced at two orders of magnitude higher in concentration than the trace metals, it can outcompete the trace metal for sites where electrostatic interactions dominate. The results indicate that in groundwater situations, where more than one metal is present, the effect of other metals must be considered in predicting metal speciation.
Trace metals play important roles in biological processes, both as essential components and toxins. Monitoring body status of trace metals thus has become an important function of many clinical, industrial, and government laboratories. Deficiencies of some essential trace metals are seen occasionally, but of most importance is the area of metal toxicity resulting from environmental, occupational, accidental, or iatrogenic exposure. Major questions persist about which specimen best reflects body status, and in this regard each metal has different requirements. Blood is used most widely, urine has a few applications, and hair can be used, although external contamination is an ever-present problem. Tissue is by far the best specimen but is not easily obtained. Contamination of specimens during collection and processing must be controlled. Of the instrumental techniques available, atomic absorption spectrometry has been used most widely, particularly with electrothermal and atomization approaches.
Progress in understanding the role of trace metals in biology has been largely dependent on the development of sensitive, accurate and precise analytical methods. Atomic spectroscopic techniques, particularly atomic absorption, have made the greatest contribution. Key to the success of such analytical techniques has been the simplification of sample processing so that contamination is minimized. Electrothermal atomization has allowed sensitivity limits to be lowered sufficiently so that even ultra-trace metals can be detected. More recently, mass spectrometric detection of metal ions has added to the repertoire of available instrumentation, particularly with the use of inductively coupled plasma to introduce ions into the mass analyzer. These analyzers are suitable for multielement analysis. More conventional mass spectrometric analysis of metal chelates offer an alternate solution but require considerable specimen preparation time. Intracellular localization of trace metals necessitates complex specimen processing prior to analysis on instruments that are highly sophisticated and expensive. Metal speciation is a rapidly growing area of trace metal research, with the major advances coming from coupling of the separation process, such as capillary electrophoresis or high performance liquid chromatography, with the analytical instrument for metal detection. Inductively coupled plasma-mass spectrometry has proved to be an excellent choice for such detection purposes. Refinement of these methods as well as more widely available instruments for microanalysis will add greatly to continued advances in our knowledge of the role of trace metals in biology and medicine.
Trace metal deficiencies are now a well-documented complication of total parenteral nutrition (TPN). Zinc deficiency may present in a variety of ways including acrodermatitis skin lesions, impaired immunity, poor growth or impaired wound healing, and mental disturbances. Copper deficiency presents a more uniform picture of hematologic abnormalities, usually anemia with leukopenia and neutropenia. Chromium and selenium deficiencies occur much less frequently, but well-documented cases have been reported. We currently recommended regular monitoring and supplementation of these four trace metals during TPN administration. This article describes the clinical abnormalities that may develop when deficiencies of trace metals occur during TPN administration, and we present recommendations for trace metal supplementation during TPN administration.
Trace metals such as zinc, manganese and iron usually serve the function of metalloproteins in neurons and glial cells, while a portion of trace metals exists in the presynaptic vesicles, and may be released with neurotransmitters. Zinc released into the synaptic cleft may serve as an inhibitory neuromodulator of glutamate release in the hippocampus, while neuromodulation by other trace metals such as manganese and copper might mean both functional and toxic aspects in the synapse. Dietary zinc deficiency affects zinc homeostasis in the brain, followed by an enhanced susceptibility to excitotoxicity of glutamate in the hippocampus. The homeostasis of trace metals in the brain is important for brain function and also prevention of brain diseases.
Cu, Cd, Zn, Pb and Se concentrations were measured in the bivalve mollusc Saccostrea glomerata(Iredale and Roughly) from two uncontaminated locations, Clyde River Estuary, Batemans Bay and Moona Moona Creek, Jervis Bay, to determine natural variability of metals associated with mass, gender, age, tissue type and site within location. Trace metals were also measured in the Clyde River Estuary over an 11 year period and in five other NSW estuaries (Hastings River, Hunter River, Georges River, Tillgerry Creek and Lake Pambula) over a 13-month period to determine temporal variability and if diploid and triploid oysters accumulate trace metals differently. There were few significant relationships between trace metal concentrations and mass and no significant differences in trace metal concentrations between female and male oysters. Younger oysters (1.3 years) had significantly higher copper concentrations and higher trace metal variability than mature oysters (3 years). Different tissues have different trace metal concentrations with muscle tissues having lower concentrations. Considerable inherent variability occurs in oyster cohorts. Analysing specific tissues did not reduce variability of trace metal concentrations. Comparison of trace metal concentrations at two sites within the Clyde Estuary showed a significant difference in zinc concentrations. Cu, Cd, Zn and Se concentrations were generally higher and less variable in triploids than diploids. Pb had a variable pattern of accumulation with no consistent elevation in diploids or triploids. Inter annual variability of trace metal concentrations was considerable and trace metal concentrations also fluctuated throughout an annual cycle with no clear seasonal trends. Measurement of trace metals at known contaminated locations showed that Saccostrea glomerata accumulates metals in response to contamination. Saccostrea glomerata meet most of the requirements to be a biomonitor of trace metal contamination as they are abundant, sessile/sedentary, easy to identify, provide sufficient tissue for analysis, and accumulate trace metals in response to contamination. However, as trace metal concentrations can vary with mass, age, estuary position, ploidy type and temporally, care must be taken to collect individual organisms of similar mass, age and ploidy type to minimise variability, and from similar consistent positions and times to allow for seasonal changes in environmental conditions. Trace metal concentration variability is higher in young animals, thus to reduce variability, older mature animals could be selected. However, with immature oysters there are no complications because of the effects of spawning i.e. sudden loss of trace metals or body mass.
Barnacles have very high accumulated trace metal body concentrations that vary with local trace metal bioavailabilities and represent integrated measures of the supply of bioavailable metals. Pioneering work in Chinese waters in Hong Kong highlighted the potential value of barnacles (particularly Balanus amphitrite) as trace metal biomonitors in coastal waters, identifying differences in local trace metal bioavailabilities over space and time. Work in Hong Kong has also shown that although barnacles have very high rates of trace metal uptake from solution, they also have very high trace metal assimilation efficiencies from the diet. High assimilation efficiencies coupled with high ingestion rates ensure that trophic uptake is by far the dominant trace metal uptake route in barnacles, as verified for cadmium and zinc. Kinetic modelling has shown that low efflux rate constants and high uptake rates from the diet combine to bring about accumulated trace metal concentrations in barnacles that are amongst the highest known in marine invertebrates.
Trace metal concentrations in phytoplankton were determined in seven locations (Stations I-VII) of the Kuwait Coast, known for significant industrial and recreational activities. Trace metal concentrations in phytoplankton (20-200 microns size) occurred in the sequence of Zn > Pb > Cu > Ni at Stations I-III and VII, and Zn > Cu > Ni > Pb at Stations IV-VI. Station III showed higher concentrations of all the analyzed metals than at other stations. Toxicity tests to phytoplankton revealed a significant decrease in the rate of oxygen with increasing concentrations of trace metals. Further, such comparisons to station wise observations between the rate of oxygen evolution and trace metal levels revealed the nature of trace metal pollution in each station off the Kuwait coast.
Whole tissue trace metal concentrations of ten metals in eight common coastal Australian polychaete species collected from uncontaminated locations were measured. The mean concentration range for each trace metal was: Mn: 2.6-13 microg g(-1); Co: 0.8-4.6 microg g(-1); Cu: 3.4-26 microg g(-1); Zn: 47-225 microg g(-1); As: 18-101 microg g(-1); Se: 2.2-20.4 microg g(-1); Ag: 0.03-2.5 microg g(-1); Cd: 0.07-17 microg g(-1); Hg: 0.08-0.88 microg g(-1) and Pb: 0.09-3.2 microg g(-1)dry mass. Principal components analysis of trace metal signatures revealed that the habitat, i.e. exposed coast sand or rock, estuarine sand or estuarine mud substrate in which a polychaete species was found, had a significant influence on the bioaccumulation of six trace metals (Mn, Cu, Zn, Ag, Cd and Pb). However, there is no clear relationship between trace metal concentrations in substrates and polychaetes. The results of the current study contribute to a reference dataset of polychaete species-specific natural background trace metal concentrations for use in determining the extent of trace metal contamination by urban and industrial sources.
The effects of trace metal contaminants (lead, cadmium, and mercury) on the immunologic responses of rats infected with Trypanosoma lewisi were investigated to determine whether chronic exposures to subclinical levels of these metals have adverse effects on the host's ability to respond to an infective agent.Earlier and higher levels of parasitemia were detected in animals exposed to cadmium, lead, and mercury. The variability in length of trypanosome cells in metal-exposed animals became constant at a later time and persisted for a longer time, indicating a delay in antibody synthesis. Serum levels of IgG and IgM were increased in infected animals exposed to trace metals; however, lower levels were observed when compared with infected control animals. Animals exposed only to trace metals showed decreases in serum levels of IgG and IgM. In contact sensitivity to dinitrofluorobenzene (DNFB), animals exposed to trace metals demonstrated no significant difference in sensitization when compared with those infected and exposed to trace metals.
Air, drawn by vacuum through a jet, was impacted against the inside surface of an atomic absorption graphite electrothermal atomizer (ETA). The amounts of the particles thus collected were determined at the ng m-3 level by graphite furnace atomic absorption or at the pg m-3 level by laser excited atomic fluorescence. The overall reproducibility of two sets of measurements, made 7 months apart, was 23%, with no significant difference between the two sets of data, based on Student's "t" test at the 95% confidence level. Short-term reproducibility varied from 13% to 34% depending upon the air concentration of the metal. The method shows promise for monitoring long-term effectiveness of the filtering systems in trace metal clean rooms. It was not possible to test for accuracy, due to the low concentrations involved, but accuracy was expected to be within a factor of 2 or 3 of the actual value, based on theoretical aspects of impaction.
Monitoring trace metal concentrations in dynamic estuarine waters is not straightforward. This study demonstrated that important information could be obtained from intensive sampling of physicochemical parameters and trace metal concentrations, in the Gold Coast Broadwater, Australia. A regular pattern of variation in Cu and Ni concentrations was related to the movement of water passed point sources with tidal flows, rather than due to conventional estuarine mixing of end-member waters. However, this approach was logistically demanding and expensive. The diffusive gradients in a thin film (DGT) technique was used as an alternative method due to its continual time-integrated response to changes in trace metal concentrations. Significant correlations were found between 24 h DGT-labile measurements and 0.45-microm filterable measurements, on time-averaged composite samples (grab samples combined every 4 h for 24 h), for Cu (n = 24, r = 0.965, p < 0.001), Pb (n = 24, r = 0.799, p < 0.001), Zn (n = 17, r = 0.909, p < 0.001), and Ni (n = 23, r = 0.916, p < 0.001). DGT-labile measurements as a fraction of 0.45 microm-filterable concentrations were 21 +/- 2% for Cu, 29 +/- 11% for Pb, 28 +/- 5% for Zn, and 27 +/- 12% for Ni, demonstrating the speciation capabilities of DGT. Although DGT measurements were confirmed as being highly operationally defined, DGT was still found to be very promising as a monitoring approach, particularly for dynamic estuarine waters.
We investigated the effect of trace metals (Fe, Mn, Cu, Zn and Mo) on the denitrification unit at the Montreal Biodome. Two dosages of the five trace metals were tested on a denitrifying bacterial population which was extracted from the denitrification unit and cultured in 250 mL chemostats with artificial seawater. The low dosage showed a 20% increase in the denitrification rate whereas the high dosage had a more pronounced effect with a 250% increase. No increase in bacterial growth was observed, suggesting that the trace metals had an effect on the denitrification activity. When the trace metals were tested separately, only iron had a significant effect similar to the increase in the denitrification rate observed when the five trace metals were added. The combination of Fe and Mn caused a small but significant increase compared to the five trace metals. We then tested the effect of adding Fe, Mn and Cu to the denitrification unit at the Montreal Biodome. A high dosage of these trace metals showed a 250% increase in the denitrification rate, which went from 200 to 700 g NO(x)-N/d. Our results showed that the addition of trace metals is crucial for denitrification activities.
In seawater, several trace metals with biological significance are highly complexed with organic matter. Marine cyanobacteria are an important phytoplanktonic group, with the ability to release trace metal-binding compounds to the seawater medium, which in turn modulates their bioavailability and influences their biogeochemical cycles. Such interactions may allow cyanobacteria to more easily access less available trace metals essential for their metabolic processes, or, conversely, keep the toxic forms of the trace metals from reaching intolerable levels. In this minireview, Cu and Fe interactions with cyanobacteria received special attention, although other trace metals (Co, Pb, Zn, and Cd) are also covered. Recent research has shed light on many aspects of trace metal-cyanobacteria ecology in seawater; nevertheless, the biochemical processes behind this dynamics and the structure of the vast majority of the metal binding compounds remain unclear.