Metal-induced developmental toxicity in mammals: a review

Organochlorine and heavy-metal contaminants in wild mammals and birds of Urbino-Pesaro Province, Italy: an analytic overview for potential bioindicators

Tissue samples from 56 bird and 11 mammal species of different trophic levels, collected from 1994 to 1995 from the Urbino-Pesaro area in the Marche region of central Italy, were analyzed for the presence of organochlorine compounds (polychlorinated biphenyls and p,p'-DDE) and heavy metals (Pb, Cd, Cr, and Hg). Results revealed interspecies differences in pollutant residue concentrations. A clear relationship between contaminant and trophic levels emerged depending on several factors specific to the chemicals and the organisms, the importance of dietary accumulation, and metabolic capacity as it increased toward higher trophic levels. Polychlorinated biphenyls and p,p'-DDE were found in all of the bird and mammal species analyzed (bird- or fish-eating birds), and insectivore mammals showed the highest level of these contaminants. Pb and Hg residues were also widely detected and reflected trophic-level differences. The highest concentration of Pb was found in herbivorous or bird-eating aquatic invertebrates and in insectivorous mammals, particularly in the hedgehog (Erinaceus europaeus), whereas the highest Hg levels were found in fish-eating birds. All of the other heavy metals were detected at low concentrations and represented background levels for birds and mammals, with the exception of increased amounts of Cd and Cr, respectively, found in stone marten (Martes foina) and fox (Vulpes vulpes). Data from this study provided information on baseline levels of interest to monitor status and trends in chemical residue in biota in this specific area, and therefore they represent a tool to evaluate potential ecologic, wildlife, and human health exposure.

Assessment of reproductive toxicity in male rats following acute and sub-chronic exposures to diphenyl diselenide and diphenyl ditelluride

The present study was conducted to evaluate the toxicity of the exposure to diphenyl diselenide [(PhSe)2] and diphenyl ditelluride [(PhTe)2] on reproductive system in Wistar rats. Adult male rats were exposed intraperitonealy (acute) or subcutaneously (sub-chronic, during 4 or 8 weeks) to (PhSe)2 or (PhTe)2 prior to mating. A number of biochemical parameters in rat testes were examined, such as delta-aminolevulinate dehydratase (delta-ALA-D) activity, lipid peroxidation, glycogen content and components of the antioxidant defenses (superoxide dismutase (SOD) activity and ascorbic acid concentration). Furthermore, a possible effect on fertility and reproductive performance in male rats were studied. Sperm counts of caudal epididymis were also evaluated. No lethality was noted in any group. Reduction on body weight in rats which received (PhTe)2 was only evidenced in acute exposure, while (PhSe)2-exposed rats presented significant loss of body weight in acute and 4 week-exposure. Mating and fertility indexes were not affected after acute and sub-chronic exposure. Regarding other parameters studied, except for a decrease in testes glycogen content in acutely (PhSe)2-treated group, no alterations were found in treated groups. Sperm counts of rats treated acutely and sub-chronically were unaffected by drugs exposure. Histological evaluation revealed no modification on testicular tissue in rats exposed to (PhSe)2 and (PhTe)2. The results suggest the absence of the male reproductive toxicity induced by (PhSe)2 and (PhTe)2 administered intraperitonealy (acute) or subcutaneously (sub-chronical) to adult rats Wistar.

Effects of Tiron, 4,5-dihydroxy-1,3-benzene disulfonic acid, on human promyelotic HL-60 leukemia cell differentiation and death

Tiron, 4,5-dihydroxy-1,3-benzene disulfonic acid, has been known to be a widely used antioxidant to rescue ROS-evoked cell death and a non-toxic chelator to alleviate an acute metal overload. In this study, we showed that Tiron is a potent inducer of cell differentiation and apoptotic cell death in human promyelotic HL-60 leukemia cell. At a low level of concentration (<0.5mM), Tiron caused HL-60 cells to induce differentiation-related alterations such as the increase of CD11b and CD14 expression or chromatin condensation. Hypoxia inducible factor-1alpha (HIF-1alpha) was also increased at mRNA and protein level, and thus the CCAAT/enhancer-binding protein alpha, which is a downstream target of HIF-1alpha and acts as a critical factor for granulocytic differentiation was increased. High dose of Tiron (>0.5mM) induced severe DNA damage in HL-60 cells, as measured by the cytokinesis-block micronucleus test and the comet assay. Consequently, high dose of Tiron led to apoptotic cell death, which showed the DNA fragmentation, the caspase activation and the unbalance between antiapoptotic (Bcl-2) and proapoptotic proteins (Bax). However, an exogenous supplement of iron (FeCl(3)) reversed all of these effects, the cell differentiation and the apoptotic cell death. Therefore, these results suggest that Tiron-mediated differentiation and cell death result from the disturbance of iron metabolism.

Four-dimensional imaging and quantification of gene expression in early developing zebrafish (Danio rerio) embryos

Four-dimensional (4D) imaging is a powerful tool for studying three-dimensional (3D) changes in an organism through time. Different imaging systems for obtaining 3D data from in vivo specimens have been developed but usually involved large and expensive machines. We successfully used a simple inverted compound microscope and a commercially available program to study and quantify in vivo changes in sonic hedgehog (shh) expression during early development in a green fluorescence protein (GFP) transgenic zebrafish (Danio rerio) line. We applied the 4D system to study the effect of 100 microM cadmium exposure on shh expression. In control zebrafish embryos, shh:GFP expression was detected at about 9 h post-fertilization (hpf) and increased steadily in the next 7 h, peaking at about 17 hpf and decreasing in the following 4 h. In the same time period, different shh expression volumes were observed in cadmium-treated and control embryos. Embryos affected by cadmium-exposure demonstrated a down-regulation in shh expression. The number of GFP-expressing cells measured by flow cytometry decreased, and expression of neurogenin-1, a downstream target of the shh signaling pathway, was down-regulated, providing additional supporting data on the effects of cadmium on shh. In summary, we demonstrated the setup of a 4D imaging system and its application to the quantification of gene expression.

Metal levels in sugar cane (Saccharum spp.) samples from an area under the influence of a municipal landfill and a medical waste treatment system in Brazil

In July 2003, duplicated samples of roots, stems and leaves of sugar cane (Saccharum spp.) were collected in 25 points of an area under direct influence of the municipal landfill site (MLS) and medical waste treatment system (MWTS) of Ribeirao Preto, São Paulo, Brazil. Cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), lead (Pb) and zinc (Zn) were determined by atomic absorption spectrophotometry. The following concentrations (mg/kg) were found in roots: Cd, 0.22+/-0.12; Cr, 64.3+/-48.7; Cu, 140.6+/-27.7; Hg, 0.04+/-0.02; Mn, 561.6+/-283.3; Pb, 7.9+/-2.1 and Zn, 177.4+/-64.9. For some metals, these levels are higher than the concentrations previously reported for different plants, reaching, in some cases, values that might be considered toxic for vegetables. Metal levels in stems were 80-90% of those found in roots, while the concentrations detected in leaves were significantly lower than those in roots. The present results suggest that MLS and MWTS activities might have been increasing metal concentrations in edible tissues of sugar cane grown in the area under their influence. Moreover, the traditional agricultural practices in the production of sugar cane could be also another determinant factor to reach the current metal levels. The results of this study indicate that sugar cane is a crop that is able to grow in areas where metals in soils are accumulated.

Mutually exclusive subsets of BH3-only proteins are activated by the p53 and c-Jun N-terminal kinase/c-Jun signaling pathways during cortical neuron apoptosis induced by arsenite

The c-Jun N-terminal protein kinase (JNK)/c-Jun and p53 pathways form distinct death-signaling modules in neurons that culminate in Bax-dependent apoptosis. To investigate whether this signaling autonomy is due to recruitment of particular BH3-only proteins, we searched for a toxic signal that would activate both pathways in the same set of neurons. We show that arsenite activates both the JNK/c-Jun and p53 pathways in cortical neurons, which together account for >95% of apoptosis, as determined by using the mixed-lineage kinase (JNK/c-Jun) pathway inhibitor CEP11004 and p53-null mice. Despite the coexistence of both pathways in at least 30% of the population, Bim mRNA and protein expression was increased only by the JNK/c-Jun signaling pathway, whereas Noxa and Puma mRNA and Puma protein expression was entirely JNK/c-Jun independent. About 50% of Puma/Noxa expression was p53 dependent, with the remaining signal being independent of both pathways and possibly facilitated by arsenite-induced reduction in P-Akt. However, functionally, Puma was predominant in mediating Bax-dependent apoptosis, as evidenced by the fact that more than 90% of apoptosis was prevented in Puma-null neurons, although Bim was still upregulated, while Bim- and Noxa-null neurons died similarly to wild-type neurons. Thus, the p53 and JNK/c-Jun pathways can activate mutually exclusive subclasses of BH3-only proteins in the same set of neurons. However, other factors besides expression may determine which BH3-only proteins mediate apoptosis.

Teratogenic effects of diphenyl diselenide in Wistar rats

Diphenyl diselenide is an organoselenium compound with potential therapeutic use. The present study evaluates the effects of single maternal subcutaneous injection of 50 and 100mg/kg diphenyl diselenide [(PhSe)2] at gestational days (GD) 6, 10 or 17 in Wistar rats. The highest dose of (PhSe2 was also administered at GD 7-12. External and internal fetal soft-tissue examination was performed at GD 20. No mortality was observed in fetuses or dams at any (PhSe)2 treatment group. Neither did exposure to (PhSe)2 cause significant changes to fetal body weight, organ weight, or fetal size when administered at GD 6-8, 10-12 or 17. Exposure to 100mg/kg (PhSe)2 at GD 9 produced significant changes in fetal biometry (crown-rump (CR) length) and body weight. No significant increase in the proportion of fetuses with external visible abnormalities was observed in groups exposed to (PhSe)2. Skeletal anomalies were observed in fetuses in the GD 9-11 treatment groups and included incomplete ossification of cranial bones, misshapen and incomplete ossification of sternebrae, reduced sternebrae number, wavy and extra ribs, incomplete ossification of fore and hindpaw bones and incomplete ossification of sacral and caudal bones. We conclude that maternal administration of (PhSe)2 during GD 7-12 led to increased incidences of these skeletal variations or anomalies, but did not cause externally visible malformations in rat fetuses.

Case study: inorganic pollutants associated with particulate matter from an area near a petrochemical plant

The area of Gela (Sicily, Italy) contains one of the largest petroleum refineries in Europe and also has several oil fields both on land and offshore. This paper discusses how the oil refinery and traffic-related air pollution affect the chemical composition of airborne particulate matter over the town of Gela, using pine needles and urban road dust as the means of survey. Forty-one samples of pine needles from Pinus halepensis (Mill.) and two composite samples of roadway dust, each subdivided into six size fractions, were analyzed for major and trace elements. Information on the natural or anthropogenic origin of the observed heavy metals was deduced from factor analysis and element distribution maps. Factor analysis was applied to a data set of 20 element concentrations in pine needles and identified three main sources of metals: soil, vehicle traffic, and industrial emissions. The petrochemical plant appears to be associated with raised levels of As, Mo, Ni, S, Se, V, and Zn. Similarly, enhanced Cu, Pb, Pt, Pd, Sb, and partly Zn concentrations are closely associated with traffic. High correlations between Ni and V, As and Se, and Pb and Sb were observed. Element distribution maps, showing a decrease in heavy metal contents immediately farther inland, confirm that local sources play a considerable role in heavy metal pollution. Morphological alterations and accumulation of phenols were observed in sections of Pinus halepensis needles collected from sites with high traffic density and industrial emissions.

Acute toxicity bioassays of mercuric chloride and malathion on air-breathing fish Channa punctatus (Bloch)

Acute toxicity tests (96 h) were conducted in flow-through systems to determine the lethal toxicity of a heavy metal compound, mercuric chloride, and an organophosphorus pesticide, malathion, to air-breathing teleost fish, Channa punctatus (Bloch) and to study their behavior. The 96-h LC50 values were determined, as well as safe levels. The results indicate that mercuric chloride is more toxic than malathion to the fish species under study. Dose- and dose-time-dependent increases in mortality rate were also observed in response to both test chemicals.

Sensitivity of δ-ALA-D (E.C. 4.2.1.24) of rats to metals in vitro depends on the stage of postnatal growth and tissue

Heavy metals, like cadmium, lead, and mercury, are potential toxic substances. The exposure to these metals can cause renal disturbances and neurological alterations. Young rats are more sensitive to harmful agents than adult animals. Delta-ALA-D enzyme acts as a biomarker of these exposures, since it has high affinity for divalent metals. The purpose of this search was to investigate the sensitivity of delta-ALA-D from suckling rats to cadmium, lead or mercury in vitro. IC(50) for delta-ALA-D activity of brain, kidneys, and liver from rats with ages between 1 and 6, 8 and 13 or 17 and 21 days was determined using metals concentrations that range from 0 to 200 microM for CdCl(2), 0 to 600 microM for HgCl(2) and from 0 to 50 microM for lead acetate. The results demonstrated that the cerebral delta-ALA-D activity is more sensitive to lead acetate than to cadmium and mercury. Delta-ALA-D from hepatic tissue is the most resistant to presence of mercury chloride in assay medium. Lead and cadmium are more toxic to renal enzyme than mercury. To sum up, the sensitivity of delta-ALA-D enzyme of young rats to heavy metals studied depends on the phase of development and tissue.

Selenium in pregnancy: is selenium an active defective ion against environmental chemical stress?

Transportation of selenium from mother to fetus and its possible effects on mother's zinc, copper, cadmium, and mercury levels were studied together during the first trimester and at term in 216 mothers. Mothers came from three geographical places with different selenium intakes. The role of selenium as a biomarker for the vital function was estimated by studying the associations between tissue or blood selenium content and placental cytochrome P450 enzyme activities and the newborn's birth weight. Regardless of the selenium intake of the mothers, higher concentrations were found in the cord blood than in mother's blood reflecting active transportation of selenium to the fetus. Active smoking was associated with higher placental selenium concentrations like it is associated with higher placental zinc concentrations. When the cadmium concentrations were high in placenta, as in smokers, the transfer of selenium from blood to placenta was increased, decreasing the selenium levels in blood. On the other hand, the high selenium concentrations in blood were connected to lower cadmium concentrations in placenta also in nonsmokers. Selenium had correlations with copper and zinc. ECOD activity in placental tissue, mercury in mothers' hair, mothers' age, and selenium concentrations in cord blood and placental selenium all seem to have connections with xenobiotic-metabolizing enzymes linked effects among mothers. These data suggest that selenium has an active role in the mother's defense systems against the toxicity of environmental pollutants and the constituents of cigarette smoke.

Expression of metallothionein gene during embryonic and early larval development in zebrafish

Metallothionein (Mt) has been considered as a molecular marker of metal pollution in aquatic ecosystems. Less is known about the expression of mt gene during embryogenesis. Here, we report the cloning, sequencing, and the expression pattern of mt gene during developmental stages in zebrafish. The zebrafish embryogenesis when takes place in a medium containing a dosage of 1000 microM zinc resulted in high mortality, indicating the deleterious effect of zinc on development. The zebrafish mt gene consists of three exons encoding 60 amino acids with 20 conserved cysteine residues. RT-PCR result indicates the maternal contribution of Mt transcripts. Using digoxigenin (DIG)-labeled anti-sense RNA probe, whole-mount in situ hybridization was performed to observe the expression pattern of zebrafish mt gene during embryonic and early larval stages. Stronger as well as ubiquitous expression of mt gene during early embryonic stages narrowed to specific expression after hatching. The mt promoter region contains seven copies of putative metal-responsive elements (MREs), which are shown to be important for the high level activity by deletion analysis. The expression of mt gene during embryogenesis implies its significant role on development.

Metavanadate causes cellular accumulation of copper and decreased lysyl oxidase activity

Selected indices of copper metabolism in weanling rats and fibroblast cultures were progressively altered in response to increased levels of sodium metavanadate. In diets, vanadium was added in amounts ranging from 0 to 80 microg V/g of diet, that is, 0-1.6 micromol V/g of diet. In fibroblast cultures, vanadium ranged from 0 to 400 nmol V/ml. The inhibition of P-ATPase-7A activity by metavanadate, important to copper egress from cells, was a primary focus. In skin, and tendon, the copper concentration was increased in response to increased dietary levels of metavanadate, whereas lysyl oxidase activity, a secreted cuproprotein, was reduced. The reduction in lysyl oxidase activity was also accompanied by reduced redox cycling potential of isolated fractions of lysyl oxidase, presumably due to reduced lysyltyrosyl quinone (LTQ) formation at the active site of lysyl oxidase. In contrast, liver copper concentrations and plasma ceruloplasmin activity were not affected by metavanadate exposure. However, semicarbazide-sensitive benzylamine oxidase (SCBO) activity, which was taken as an indirect measure of vascular adhesive protein-1 (VAP-1), was increased. In cultured fibroblasts, cellular copper was also increased and lysyl oxidase decreased in response to metavanadate. Moreover, the steady-state levels of atp7a and lysyl oxidase mRNAs were not affected by addition of metavanadate to culture medium up to 200 nmol/ml. Taken together, these data suggest that pathways involving copper egress and lysyl oxidase activation are particularly sensitive to metavanadate exposure through processes that are predominately posttranslational.

Aerial deposition of cadmium before and after the closure of an oil-fired power station in the vicinity of two nursery roosts of Rhinolophus ferrumequinum (Chiroptera, Rhinolophidae)

Aerial deposition of cadmium has been monitored from 1994-1995 to the present by extraction of cadmium from petroleum jelly coated onto ceramic tiles placed near two nursery roosts and in the foraging area of greater horseshoe bats,

Phytoremediation of heavy metals from soils

Phytoremediation offers owners and managers of metal-contaminated sites an innovative and cost-effective option to address recalcitrant environmental contaminants. The use of plants or plant products to restore or stabilize contaminated sites, collectively known as phytoremediation, takes advantage of the natural abilities of plants to take up, accumulate, store, or degrade organic and inorganic substances. Although not a new concept, phytoremediation is currently being re-examined as an environmentally friendly, cost-effective means of reducing metal contaminated soil and other substrates throughout North America and Europe. Processes include using plants that tolerate and accumulate metals at high levels (phytoextraction) and using plants that can grow under conditions that are toxic to other plants while preventing, for example, soil erosion (phytostabilization). Governments worldwide are establishing research and demonstration programs to use this potential. Environment Canada has developed a database (PHYTOREM) of 775 plants with capabilities to accumulate or hyperaccumulate one or several of 19 key metallic elements. This chapter addresses key research, potential benefits and limitations, and the potential future needs for phytoremediation. Issues related to intellectual property law, commercialization and public acceptance are touched on.

Damage to the liver, kidney, and testis with reference to burden of heavy metals in yellow-necked mice from areas around steelworks and zinc smelters in Poland

The influence of the steelworks in Warsaw and Krakow as well as the zinc smelters in Bukowno and Miasteczko Slaskie on lead, cadmium, zinc and iron concentrations and the structure of selected tissues of yellow-necked mice were analysed. The Borecka Forest was chosen as a control area. The highest concentrations of lead, 172.36 g/g dry weight, and cadmium, 23.58 g/g, were detected in the femurs and kidneys, respectively, of rodents caught in Bukowno. Zinc and iron concentrations ranged over physiological values. No histopathological changes were observed in analysed tissues of all rodents in the control area. Damage occurred in the liver and kidneys of animals from all other sites and in the testes of rodents from Bukowno. Decreased glycogen content, interstitial fibrosis, and increased number of pyknotic nuclei as well as necrosis were seen in hepatocytes. In the kidneys hyperplasia of the tubules, atrophy of glomeruli, interstitial fibrosis and necrosis were observed. Degenerate cells were present in the lumen of seminiferous tubules of animals from the Bukowno area. Even relatively low concentrations of lead and cadmium, like those found in the liver and kidneys of rodents from the neighbourhood of the steelworks, caused histopathological changes.

Effects of ammonium metavanadate on fertility and reproductive performance of adult male and female rats

Vanadium is a ubiquitous trace metal present in most plant and animal tissues. Environmental exposure to trivalent and pentavalent inorganic vanadium compounds has been related to impaired different phases of reproduction. Therefore, the effects of a pentavalent inorganic vanadium compound on general reproductive performance and fertility were investigated in male and female rats. Sexually mature male and female rats were exposed to 200 ppm ammonium metavanadate in drinking water. Male rats were exposed for 70 days, while the female rats exposed for 14 days premating, during mating, and throughout the whole length of gestation and lactation periods till weaning. The effects on male sex organ weights and fertility were evaluated at the end of exposure period. However, the effects on female fertility as well as developmental and postnatal effects were evaluated throughout the exposure period. The fertility was significantly reduced in both treated groups, with more pronounced suppressive effects in the male treated group. The number of implantation sites and the number of viable fetuses were significantly reduced in pregnant females of both treated groups. However, the number of resorptions, dead fetuses, and pre- and postimplantation losses were significantly increased. The incidence of resorptions was significantly increased in treated female group compared with untreated female group. The behavioral responses as well as fetal survival and viability indices were decreased in both treated groups during the lactation period. The incidence of these effects was more pronounced in the treated female group. The morphological, visceral, and skeletal anomalies were recorded significantly increased in fetuses of both treated groups, with more pronounced effects on fetuses of treated females. In conclusion, the exposure of adult male and female rats to ammonium metavanadate would cause adverse effects on fertility and reproduction.

Soluble and insoluble fractions of heavy metals in wet and dry atmospheric depositions in Bologna, Italy

Atmospheric depositions were collected monthly using a modified wet and dry sampler (dry deposition was collected on a water surface) located in Bologna, a northern Italian urban area, to evaluate the impact of airborne heavy metals on the local pollution load. Wet deposition samples were filtered and heavy metal contents in soluble and insoluble fractions were determined. The same procedure was applied to the water samples which collected dry deposition. The entire procedure was tested using a certified reference material (CRM), which provided satisfying recovery results. The percentage of heavy metal soluble fraction in dry deposition was generally lower than in wet one; Cd, V, Cu and Zn showed a higher average solubility than Cr, Ni and Pb both in wet and dry deposition. Factor analysis, after a varimax rotation of principal components, suggested possible anthropogenic sources which explain different metal deposition patterns. This data analysis also allowed to distinguish different clusters formed by monthly fluxes of heavy metals.

PCDD/F and metal concentrations in soil and herbage samples collected in the vicinity of a cement plant

In May 2000, the levels of a number of metals (As, Cd, Pb, Hg, Zn, Co, Cu, Mn, Sn, Tl, Cr, Ni and V) were determined in 16 soil and herbage samples collected in the vicinity of a cement plant from Sta. Margarida i els Monjos (Catalonia, Spain). Metal concentrations were also analyzed in air filters from three sampling stations placed nearthe facility. For most metals, concentrations were similar or even lower than previously reported values for other areas from Catalonia. On the other hand, the levels of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) were also determined in four soil and 16 herbage samples. Mean values were 0.37 and 0.16 ng I-TEQ/kg for soils and herbage, respectively, values which in comparison with data from other surveys are rather low. No significant differences between metal and PCDD/F concentrations in samples collected at distances lower or greater than 3.5 km of the facility were noted. The current results show that the cement plant has a low impact on the metal and PCDD/F levels in the environment under direct influence of the facility. These results should be of interest to assess future temporal variations in the levels of metals and PCDD/Fs in this area.

Levels of metals in soils of Alcalá de Henares, Spain: human health risks

The concentrations of aluminium (Al), arsenic (As), beryllium (Be), cadmium (Cd), chromium (Cr), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), tin (Sn), thallium (Tl), vanadium (V), and zinc (Zn) were determined in soil samples collected in Alcalá de Henares (Madrid, Spain). Human health risks derived from metal inhalation and ingestion of soils were also assessed. For noncarcinogenic risks, the current levels of metals were usually lower than those considered as safe for the general population. With respect to the potentially carcinogenic elements As, Be, Cd, and Cr, the concentrations of Be, Cd, and Cr were lower than the reference values, while the average As concentration (3.4 microg/g) was higher than the safety limit for risk cancer. In general terms, the potential human health impact of ingestion/inhalation through soils of the analyzed elements seems to be rather small.

Survey of some heavy metals in sediments from vehicular service stations in Jordan and their effects on social aggression in prepubertal male mice

Vehicle services create the potential for heavy metal accumulation in the working environment. This study assessed five vehicle services, namely body repair, oil exchange, mechanical repair, tire repair, electrical repair, and washing services for three types of vehicles: airplanes, buses, and cars. The results show that there are significant increases in the total contents of Fe, Cu, Pb, Zn, Ni, Mn, and Cr in ambient dust, with Fe being the highest and Cr the lowest. The main cause of the presence of these elements is due to the metals' corrosion from vehicle sources and petroleum residue. Variations in the concentrations with the type of service and within the same service at different locations were observed. In this study, the exposure of prepubertal male mice to industrial metal salts in drinking water at a concentration of 1000 ppm for 90 days was investigated. Exposure of male mice to lead acetate significantly reduced the social aggression of the resident untreated subjects. Additionally, this treatment resulted in decreasing weights of body, testes, preputial glands, and seminal vesicles. In comparison, no such effects were seen in mice given copper chloride or manganese chloride. The results show that only lead acetate produced a pattern of responses clearly indicative of altered gonadal function.

In vivo and in vitro modulation of carp (Cyprinus carpio L.) phagocyte oxidative burst activity by gallium

Since gallium is a metal ion used in semiconductor industry, the toxicological effects were previously evaluated in mammals but the ecotoxicological impacts remain unknown. In term of ecotoxicological risk assessment, the median lethal concentration (LC50 for 96 h of gallium to carp (Cyprinus carpio L.) and the oxidative response of carp phagocytes after the fish were exposed to sublethal levels of gallium were determined. The LC50 of gallium on C. carpio at 96 h was estimated as 96.25 +/- 14.3 mg/L. To determine the effect in vivo of gallium on the phagocyte response, fish were exposed for 96 h to 5 or 50 mg Ga(3+)/L. Carp maintained for 48 or 96 h in water containing 50 mg/L gallium had a significant fall in phagocyte oxidative burst activity in comparison with controls, as well as decreased leukocyte number in blood and increased cytotoxicity. To determine the effect in vitro of gallium on the phagocyte response, isolated phagocytes were exposed for 5 or 15 min to 50 nM, 500 nM, or 5, 50, 100, or 200 microM of Ga(3+). The oxidative burst was increased after in vitro incubation of phagocytes with 50 or 500 nM gallium for 15 min or with 500 nM gallium for 5 min. Moreover, for 50, 100, or 200 microM gallium, the oxidative burst activity of carp phagocytes was significantly decreased. Results indicate that the lethal toxicity of gallium for carp of gallium is not as high as for other metal ions. However, gallium was immunosuppressive for carp at the highest concentrations used (from 50 microM) in vivo and in vitro. At low concentrations, it could be an immunostimulant as observed in vitro.

Carcinogenicity, mutagenicity and teratogenicity of manganese compounds

Manganese, an essential trace element, is one of the most used metals in the industry. Recently, several new manganese compounds have been introduced as fungicide, as antiknock agent in petrol and as contrasting agent in nuclear magnetic resonance tomography. Manganese displays a somewhat unique behaviour with regard to its toxicity. It is relatively non-toxic to the adult organism except to the brain where it causes Parkinson-like symptoms when inhaled even at moderate amounts over longer periods of time. Relatively high doses of manganese affect DNA replication and repair in bacteria and causes mutations in microorganism and mammalian cells although the Ames test does not appear to be particularly responsive to manganese. In mammalian cells, manganese causes DNA damage and chromosome aberrations. Information on organic manganese derivatives is still insufficient. Large amounts of manganese affect fertility in mammals and are toxic to the embryo and foetus. The fungicide MANEB and the contrasting agent MnDPDP also can be embryotoxic, but the latter only at doses much higher than those clinically employed. Information on the anti-knock agent MMT is inadequate. On the other hand, manganese deficiency can also affect fertility and be teratogenic. Information on cancer due to manganese is scanty but the results available do not indicate that inorganic manganese is carcinogenic. More information is desirable with regard to the organic manganese derivatives. It may surprise that an agent that causes mutations is not also carcinogenic. The experience with manganese shows that conclusions with regard to carcinogenicity of an agent based on the observation of mutations are subject to uncertainties. Altogether, it appears that, because of the very high doses at which positive effects have been found, manganese would not represent a significant carcinogenic risk to the population and workers. Care must, however, be exercised with respect to central-nervous symptoms after chronic exposure and with respect to effects on the embryo. Pregnant women should not be exposed to manganese at the work place.

Effects of prenatal exposure to manganese on postnatal development and behavior in mice: influence of maternal restraint

Manganese (Mn) is an essential trace element whose deficiency and excess have been reported to cause central nervous system (CNS) disturbances. On the other hand, during pregnancy, maternal stress has been shown to enhance the developmental toxicity of a number of metals. In this study, the maternal toxicity and developmental effects of a concurrent exposure to Mn and restraint stress were evaluated in mice. Pregnant animals were divided into three groups and received subcutaneous injections of manganese chloride tetrahydrate (MnCl2.4H2O) at 0, 1 and 2 mg/kg/day on Gestation Days 6-18. Each group was divided into two subgroups. Mice in one subgroup were subjected to restraint for 2 h/day on Days 6-18 of gestation. Pregnant mice were allowed to deliver, and pups were evaluated for physical and neuromotor maturation. Subsequently, adult mice were also evaluated for activity and learning. A significant increase in perinatal mortality was observed at 2 mg/kg/day Mn. A delay in some developmental landmarks (eye opening, testes descent) due to Mn exposure (2 mg/kg/day) was also seen in both restrained and unrestrained animals. No differences in motor resistance and coordination, or in learning at the passive avoidance test, were noted in adult mice. At the current Mn doses, combined exposure to Mn and stress during the prenatal period did not produce long-lasting effects on adult mice.

Spatial distribution and temporal variation of metals in the vicinity of a municipal solid waste incinerator after a modernization of the flue gas cleaning systems of the facility

In June 1994 and 1997, the concentrations of a number of elements were determined in soil and herbage samples collected in the vicinity of a municipal solid waste incinerator (MSWI) (Tarragona, Catalonia, Spain). In August 1997, an adaptation to the EU legislation on pollutant emissions from the stack was carried out to the incinerator. In June 1999, soil and herbage samples were collected again at the same sampling points and the levels of arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni) and vanadium (V) were measured by ICP-MS or AAS with graphite furnace. The results are compared with those obtained in the 1994 and 1997 surveys. In the period 1997-1999, the only significant changes in soil levels corresponded to Cd and Pb, with decreases of 21.0% and 53.5%, respectively. In vegetation, only Mn levels showed a significant reduction, which contrasts with the notable increases found in the concentrations of As, Hg and Ni. According to the results of this survey, it seems evident that other metal emission sources in the same area of study are masking the environmental improvements carried out in the MSWI.

Randomized placebo-controlled trial of 2,3-dimercapto-1-propanesulfonate (DMPS) in therapy of chronic arsenicosis due to drinking arsenic-contaminated water

BACKGROUND

Chronic arsenic toxicity, producing various clinical manifestations, is currently epidemic in West Bengal, India, Bangladesh, and other regions of the world. 2,3-Dimercapto-1-propanesulfonate, a chelating agent, increases excretion of arsenic in urine to several times the prechelation concentration but the therapeutic efficacy of 2,3-dimercapto-1-propanesulfonate in the management of chronic arsenic toxicity has been incompletely evaluated. We investigated the clinical use of 2,3-dmercapto-1-propanesulfonate in such patients.

METHODS

Twenty-one consecutive patients with chronic arsenicosis were individually randomized into 2 groups: 11 patients (9 males and 2 females, age 30.63+/-11.4 years) received 2,3-dimercapto-1-propanesulfonate 100-mg capsules 4 times a day for 1 week and repeated in the 3rd, 5th, and 7th week with no drug during the intervening period. The other 10 patients (5 males and 5 females, age 34.4+/-14.41 years) were given placebo capsules (resembling 2,3-dimercapto-1-propanesulfonate) in the same schedule. The consumption of arsenic-contaminated water was terminated by all 21 subjects. Initial and posttreatment urinary arsenic excretion was determined in all cases. Sequential excretion of urinary arsenic was determined during the treatment of 2 drug- and 1 placebo-treated cases. The clinical features were evaluated by an objective scoring system before and after treatment. Routine investigation including liver function test and skin biopsy were also done before and after the treatment. Drug-associated toxicity was tabulated.

RESULTS

Therapy with 2,3-dimercapto-1-propanesulfonate caused significant improvement in the clinical condition of chronic arsenicosis patients as evidenced by significant reduction of total clinical scores from 8.90+/-2.84 to 3.27+/-1.73; p < 0.0001. Exposure cessation alone with placebo treatment also reduced clinical scores (8.50+/-1.96 to 5.40+/-2.12; p < 0.003), but the posttreatment total clinical score of 2,3-dimercapto-1-propanesulfonate-treated patients (3.27+/-1.73) was significantly lower than that of placebo-treated patients (5.40+/-2.12; p < 0.01). The most significant improvement was noted in regard to the clinical scores of weakness, pigmentation, and lung disease. No difference was noted between groups in the hematological and biochemical parameters (which were normal) and skin histology before and after treatment. No 2,3-dimercapto-1-propanesulfonate-related adverse effects were noted. Total urinary excretion of arsenic in 2,3-dimercapto-1-propanesulfonate-treated cases increased significantly following drug therapy, with no increase in placebo-treated cases.

CONCLUSION

2,3-Dimercapto-1-propanesulfonate treatment caused significant improvement in the clinical score of patients suffering from chronic arsenic toxicity. Increased urinary excretion of arsenic during the period of therapy is the possible cause of this improvement.

A comparative study of the toxicity of mercury dichloride and methylmercury, assayed by the Frog Embryo Teratogenesis Assay--Xenopus (FETAX)

The Frog Embryo Teratogenesis Assay-Xenopus (FETAX) is a powerful and flexible bioassay that makes use of the embryos of the anuran amphibian Xenopus laevis. The FETAX can detect xenobiotics that affect embryonic development, when mortality, teratogenicity and growth inhibition are used as endpoints. The FETAX was used to compare the embryotoxic and teratogenic potentials of two chemical species of mercury, inorganic mercury(II) chloride (HgCl2) and organic methylmercury chloride (MeHgCl). A higher toxicity of MeHgCl (the estimated median lethal concentration [LC50] and median teratogenic concentration [TC50] were 0.313microM and 0.236microM, respectively) over HgCl2, with estimated LC50 and TC50 values of 0.601microM and 0.513microM, respectively). On the basis of these results, HgCl2 and MeHgCl can be classified as "slightly teratogenic compounds", as the ratio of LC50/TC50 is less than 1.5. There was a significant deviation from the commonly described monotonic behaviour of the concentration-response curves, suggesting a hormetic effect of both species of mercury. Uptake experiments, followed by neutron activation analysis, showed a higher incorporation of mercury in embryos exposed to MeHgCl compared with those exposed to HgCl2. Interestingly, Hg- exposed embryos showed a higher content of selenium and zinc than did control embryos.

Response of fluctuating asymmetry to arsenic toxicity: support for the developmental selection hypothesis

The effect of exposure to sodium arsenite during development was tested on adult fluctuating asymmetry (FA) in sternopleural bristle number, bristle number, body size and survivorship in Drosophila melanogaster. Three genetic strains of flies were used, CT-106, PVM and Oregon-R, and arsenite concentrations ranged from relatively mild, sub-lethal doses, to concentrations with pronounced negative effects on survivorship. At arsenite concentrations of 1.0 and 0.125 mM, mortality was on average 38% greater than in controls, and surviving flies emerged significantly smaller and had fewer bristles than controls. Neither the effect of arsenite or the genotype x environment interaction on asymmetry were significant. However, given the high mortality, any increase in FA could have been masked by the outcome of developmental selection against developmentally unstable phenotypes. We tested for this effect by contrasting FA values between (1) flies reared at the highest concentrations used previously, (2) flies reared at sub-lethal dosage, and (3) controls. Positional fluctuating asymmetry (PFA), which is expected to be a sensitive indicator of underlying developmental stability, was significantly reduced among flies reared at the highest concentration, and at which flies suffered significant mortality. Moreover, the slope of the regression relating mean PFA to emergence per bottle was significantly positive. These data support the hypothesis that developmental selection occurred in this experiment, and that the expected positive relationship between asymmetry and stress may be altered when the stressor eliminates individuals from the population. In contrast, FA of flies reared at sub-lethal dosage did not differ from that in controls, a result that fails to support the hypothesis that arsenite disrupts developmental stability. Our results call for caution in FA-based biomonitoring, especially of potentially lethal forms of stress, because in the presence of developmental selection, and under the common assumption that FA should increase under stress, erroneous conclusions may be drawn about the health and well being of a population. It is suggested that FA-based biomonitoring efforts integrate the use of FA with other bioindicators, and experimentally validate any expected FA-stress relationship before attempting to infer the presence of environmental stress.

Cadmium distribution and toxicity in tissues of small rodents

The aim of the present paper is to discuss the accumulation and distribution of cadmium (Cd) in the various tissues of animals, the interactions of cadmium with other elements, and the damage to tissues caused by this metal. Cadmium is not physiologically or biochemically essential to an organism. It is absorbed via the gastrointestinal tract and lungs and accumulated in various tissues, mainly the kidneys and liver. The distribution of cadmium between various tissues depends on many endogenous and exogenous factors. Cadmium is bound to a low-molecular-weight protein, metallothionein (MT), and to high-molecular-weight proteins. This metal has a great affinity to thiol groups. Cadmium binds also to O- and N-containing ligands. The distribution of cadmium between organs differs markedly depending on the chemical form of administered Cd and the duration of exposure. Acute exposure results in a different distribution pattern throughout the body than does chronic exposure. Long-term exposure to high doses of cadmium may cause biochemical and functional changes in some critical organs. Cadmium can influence the absorption and distribution of essential elements and can replace them in enzymes. Metallothionein and glutathione play important roles in the transport of metals and in detoxification processes. Reported findings are mainly the results of experiments on laboratory animals. The lack of data concerning the localization of cadmium in various tissues of wild species is noticeable and there is a great need for such data.

Arsenite-induced apoptosis in cortical neurons is mediated by c-Jun N-terminal protein kinase 3 and p38 mitogen-activated protein kinase

c-Jun N-terminal protein kinase (JNK) and p38 mitogen-activated protein kinase are activated by stress and are implicated in regulation of apoptosis in several tissues. However, their contribution to stress-induced apoptosis in CNS neurons is not well defined. Here we investigated the role of JNK and p38 in cortical neuron apoptosis caused by sodium arsenite treatment. Sodium arsenite is an environmental toxicant that causes developmental defects in the CNS. Treatment of cortical neurons with sodium arsenite activated p38 and JNK3 but not JNK1 or JNK2. It also induced c-Jun phosphorylation. Furthermore, sodium arsenite induced cortical neuron apoptosis. This apoptosis was attenuated by SB203580, an inhibitor of p38, and by CEP-1347, an inhibitor of JNK activation. Expression of dominant-interfering mutants of the JNK or p38 pathways inhibited apoptosis induced by arsenite, whereas expression of constitutive active mutants for either pathway induced apoptosis. Moreover, the caspase inhibitor zVAD-fluoromethylketone as well as expression of bcl-2 or bcl-xL inhibited cortical neuron apoptosis induced by arsenite or by constitutive activation of JNK or p38. These data indicate that both JNK and p38 contribute to arsenite-induced apoptosis in primary CNS neurons, and this apoptosis requires the bcl-2-caspase pathway. This is the first evidence that a specific JNK isoform is differentially activated by stress and contributes to neuronal apoptosis.

Putative peripheral neuropathy in suckling piglets

Over a period of almost 2 years, a progressive motor disturbance was found to occur in 20-50% of the litters of both primiparous and multiparous sows in a large pig herd of 1000 sows. The motor disturbance sometimes affected the entire litter; however, in most cases only a few piglets per litter were affected. The clinical signs appeared at 3-5 days of age and consisted of difficult movement followed by anteflexion or retroflexion of the tarsal joints or 'rabbit-like posture'. Subsequently, primarily after weaning, inflammatory and necrotic lesions developed on the paralysed limbs as a result of secondary infections of injuries. The tibial nerve and the common fibular nerve of recently affected (5- to 6-day-old) piglets showed degeneration, demyelination and necrosis of some of the nerve fibres, accompanied by restorative changes in more chronic cases. The central nervous system, bones, skeletal muscles, tendons and joints showed no lesions that could have accounted for the symptoms of motor disturbance. Aetiological investigations excluded the possibility of lead, copper and cadmium toxicity. Vitamin B2 administered orally at 1 day old proved to be ineffective. The disease did not develop in piglets of sows kept at another farm under the same management and fed a diet prepared according to an identical formula from the same ingredients as those used on the affected farm, but with no milk whey added. This raised the suspicion of triaryl phosphate (TAP) poisoning, but this was found not to be the cause of the disease. New boars had not been brought to the farm in the year preceding the onset of disease, and the disease could not be linked to a specific boar or boar line. The aetiology of the disease has remained unclear.

Analysis of chromosomal aberration frequencies in the peripheral blood lymphocytes of smokers exposed to uranyl compounds

One hundred fifteen smokers working in a nuclear fuel manufacturing facility were analysed for various types of chromosomal aberrations. They experienced exposure for a period of 1-25 years. Their age ranges from 23 to 52 years. A total of 94 smokers and 118 non-smokers who were not exposed to uranyl compounds or to any other known mutagens and belong to the same age group formed the control subjects. The results showed that there is a significant increase in the frequency of chromosomal aberrations in the exposed smokers when compared to the control smokers. In the control group, the smokers showed a high frequency of chromosomal aberrations when compared to non-smokers suggesting clastogenic effect of smoking. Chromosomal aberrations observed in the exposed smokers could be due to the cumulative effect of both smoking and exposure to uranyl compounds.

Identification of a murine locus conveying susceptibility to cadmium-induced forelimb malformations

The heavy metal cadmium (Cd), an environmentally ubiquitous contaminant, is a potent teratogen in mice. When administered parenterally, it induces an array of malformations that vary in scope and severity with the route, dose, time of administration, and the strain of the animal. When administered intraperitoneally on day 9.0 of gestation, 4 mg/kg cadmium chloride produces forelimb defects (predominantly ectrodactyly) in over 80% of fetuses of the C57BL/6 mouse strain, while no limb defects are observed in the identically treated SWV strain. Like other examples of strain-specific teratogenic activity, the underlying nature of the differential susceptibility remains unknown. The present study investigates the segregation of sensitivity to Cd-induced forelimb defects in crosses between C57BL/6 and SWV mice and provides evidence for the involvement of both maternal and fetal factors in the determination of defect expression. In addition, quantitative trait loci (QTL) analysis of the fetal genetic component was performed among 198 backcross progeny, utilizing a genomic linkage map of 149 informative microsatellite markers. One QTL demonstrating significant linkage to expression of the defect, designated Cadfar (cadmium-induced forelimb autopod reduction), was mapped to the distal end of chromosome 6 with a lod score of 3.1.

Monitoring metals in the vicinity of a municipal waste incinerator: temporal variation in soils and vegetation

The aim of this study was to determine the temporal variation in the concentrations of arsenic (As), beryllium (Be), cadmium (Cd), chromium (Cr), manganese (Mn), mercury (Hg), nickel (Ni), lead (Pb), tin (Sn), thallium (Tl), vanadium (V) and zinc (Zn) in soil and vegetation near an old municipal solid waste incinerator (MSWI). In October 1997, 24 soil and 24 herbage samples were collected at the same sampling points in which samples were also taken in October 1996. With the exception of an increase in the levels of Be and Ni, no significant differences in soils between both surveys were found; only Cr and V (decreases) and Hg (increase) showed significant variations in herbage samples during the last year. The concentrations of most elements in soil and vegetation samples collected near the MSWI are within the ranges previously reported for soil and vegetation in the vicinity of MSWIs.

Accumulation of cadmium in and its effect on bank vole tissues after chronic exposure

Cadmium is one of many metals that are not physiologically or biochemically essential to organisms. This element is extremely dangerous as it is easily absorbed and remains in tissues for a long time. Long exposure to high doses of cadmium may cause biochemical and functional changes in some critical organs. In this study, wheat grains contaminated with cadmium chloride were used to test the influence of cadmium on male bank voles (Clethrionomys glareolus). Doses used in the experiment were environmentally realistic: 0.25 microg g-1 (control), 15 microg g-1, and 40 microg g-1 cadmium (dry weight). The animals were given cadmium-contaminated food and clean water ad libitum for 3 and 6 months. After these exposures, the animals were killed and the kidneys, liver, and testes from each vole were collected for analyses. The concentrations of Cd, Cu, Zn, and Fe in the tissues were determined with an atomic absorption spectrophotometer. The formalin-fixed testes, kidneys, and part of the liver were embedded in paraffin and then stained with hematoxylin and eosin. Cadmium accumulation in the tissues was directly proportional to dose. The highest cadmium concentrations were found in the kidneys of animals fed the highest dose of cadmium. Histological examination of the tissues revealed some pathological changes in the structure of kidneys, liver, and testes.

Developmental toxicity of metal chelating agents

Chelation therapy is the basis for the treatment of metal poisoning. A number of chelating agents have been widely used since the 1950s. Since these agents can be potentially given to a metal-intoxicated pregnant woman, their intrinsic developmental toxicities are a matter of concern. While the embryo/fetal toxic effects of some chelators have been reported to occur at doses higher than those currently given in the medical treatment of metal poisoning, according to experimental data the potential use of other metal antidotes is controversial. In those cases, the benefits and risks of usage should be carefully weighed. The developmental toxicity of known chelators of clinical interest is presented here. Chelating agents were divided according to the following structurally related categories: polyaminocarboxylic acids, chelators with vicinal -SH groups, beta-mercapto-alpha-aminoacids, hydroxamic acids, ortho-hydroxycarboxylic acids, and miscellaneous agents. Since it has been demonstrated that the teratogenic potential of most chelators is, at least in part, due to induced trace element deficiencies, the advisability of mineral supplements during chelation treatment is also discussed.

An assessment of the developmental toxicity of inorganic arsenic

A critical analysis of the literature base regarding the reproductive and developmental toxicity of arsenic compounds, with emphasis on inorganic arsenicals, was conducted. The analysis was stimulated by the great number of papers that have purported to have shown an association between exposure of pregnant laboratory animals to arsenic compounds and the occurrence of offspring with cranial neural tube defects, particularly exencephaly. For the most part, the literature reports of arsenic developmental toxicity in experimental animals are inadequate for human risk assessment purposes. Despite the shortcomings of the experimental database, several conclusions are readily apparent when the animal studies are viewed collectively. First, cranial neural tube defects are induced in rodents only when arsenic exposure has occurred early in gestation (on Days 7 [hamster, mouse], 8 [mouse], or 9 [rat]). Second, arsenic exposures that cause cranial neural tube defects are single doses that are so high as to be lethal (or nearly so) to the pregnant animal. Third, the effective routes of exposure are by injection directly into the venous system or the peritoneal cavity; even massive oral exposures do not cause increases in the incidence of total gross malformations. Fourth, repetition of similar study designs employing exaggerated parenteral doses is the source of the large number of papers reporting neural tube defects associated with prenatal arsenic exposure. Fifth, in five repeated dose studies carried out following EPA Guidelines for assessing developmental toxicity, arsenic was not teratogenic in rats (AsIII, 101 micromol/kg/d, oral gavage; 101 micromol/m3, inhalation), mice (AsV, 338 micromol/kg/d, oral gavage; est. 402 micromol/kg/d, diet), or rabbits (AsV, 21 micromol/kg/d, oral gavage). Data regarding arsenic exposure and adverse outcomes of pregnancy in humans are limited to several ecologic epidemiology studies of drinking water, airborne dusts, and smelter environs. These studies failed to (1) obtain accurate measurements of maternal exposure during the critical period of organogenesis and (2) control for recognized confounders. The lone study that examined maternal arsenic exposure during pregnancy and the presence of neural tube defects in progeny failed to confirm a relationship between the two. It is concluded that under environmentally relevant exposure scenarios (e.g., 100 ppm in soil), inorganic arsenic is unlikely to pose a risk to pregnant women and their offspring.

Developmental and reproductive toxicity of inorganic arsenic: animal studies and human concerns

Information on the reproductive and developmental toxicity of inorganic arsenic is available primarily from studies in animals using arsenite and arsenate salts and arsenic trioxide. Inorganic arsenic has been extensively studied as a teratogen in animals. Data from animal studies demonstrate that arsenic can produce developmental toxicity, including malformation, death, and growth retardation, in four species (hamsters, mice, rats, rabbits). A characteristic pattern of malformations is produced, and the developmental toxicity effects are dependent on dose, route, and the day of gestation when exposure occurs. Studies with gavage and diet administration indicate that death and growth retardation are produced by oral arsenic exposure. Arsenic is readily transferred to the fetus and produces developmental toxicity in embryo culture. Animal studies have not identified an effect of arsenic on fertility in males or females. When females were dosed chronically for periods that included pregnancy, the primary effect of arsenic on reproduction was a dose-dependent increase in conceptus mortality and in postnatal growth retardation. Human data are limited to a few studies of populations exposed to arsenic from drinking water or from working at or living near smelters. Associations with spontaneous abortion and stillbirth have been reported in more than one of these studies, but interpretation of these studies is complicated because study populations were exposed to multiple chemicals. Thus, animal studies suggest that environmental arsenic exposures are primarily a risk to the developing fetus. In order to understand the implications for humans, attention must be given to comparative pharmacokinetics and metabolism, likely exposure scenarios, possible mechanisms of action, and the potential role of arsenic as an essential nutrient.

Embryo and fetotoxicity of hexavalent chromium: a long-term study

Ingestion of chromium(VI) (250, 500 or 750 ppm as potassium dichromate, K2Cr2O7) through drinking water by female rats for 3 months prior to gestation was toxic to embryo and fetus. There was a significant reduction in number of implantations and number of fetuses and an increase in number of resorptions and pre-implantation and post-implantation losses. No significant visceral abnormality was found. The increase in the number of subdermal hemorrhagic patches on the thorax and abdomen was significant. Skeletal abnormality in the form of reduced ossification in parietal, interparietal and caudal bones was observed in fetuses. Chromium levels in the blood of mothers, placenta and fetuses showed a significant increase. Duration of the estrous cycle was also increased significantly. The study revealed that long-term chromium exposure in rats did not cause embryo and fetotoxicity in a duration-dependent manner compared to short-term treatment as observed earlier. A possible explanation could be that, in the 90-day study, the female rats did not mate for three estrous cycles, thus giving time for clearance of a sizable amount of chromium from their bodies.

Increased sister chromatid exchange and chromosomal aberration frequencies in psychiatric patients receiving psychopharmacological therapy

Combinations of various psychotropic drugs are often used, sometimes for long periods, in the treatment of various forms of psychiatric disorders. This paper evaluates the cytogenetic consequences of daily exposure to polytherapy with antianxiety, antipsychotic and antimaniacal drugs by determining chromosomal aberrations (CA) and sister chromatid exchange (SCE) in peripheral blood samples. The study was performed with a group of 36 psychiatric patients: 18 receiving long-term treatment with lithium carbonate, combined with benzodiazepines (BD) and antipsychotic agents (Group A) and 18 treated with BD and antipsychotics (Group B). Among the latter, 7 patients had only been treated for 1 month (Group B1). The results reveal a significant increase (p<0.01) in cells with aberrations in the two groups of patients (A,B) compared to controls. Moreover, complex aberrations (dicentrics, rearrangements, chromatid exchanges) had a frequency of 0.63% in patients receiving long-term treatment compared to 0.11% in controls, corresponding to the general spontaneous rate. The mean frequency of SCE/cell and the percentage of cells with a high frequency of exchanges (HFC) also showed a highly significant difference compared to controls in both Group A and Group B. Group B1 (patients who only commenced treatment 1 month earlier) did not differ from the control group with regard to the frequency and type of chromosomal aberration or in relation to the mean frequency of SCE/cell. No significant differences were detected between Groups A and B both of which showed similar frequencies of cells with aberrations, SCE/cell and HFC. No correlations were observed in Group A between lithemia and the biological markers studied.

Toxicity assessment of 16 inorganic environmental pollutants by six bioassays

The relative toxicity of 16 environmental pollutants, such as inorganic elements (Ba, Cd, Co, Cr, Cu, Fe, Ge, Hg, Mn, Nb, Pb, Sb, Sn, Ti, V, and Zn), is evaluated on the L-929 established cell line of murine fibroblasts, with five bioassays [RNA synthesis rate assay (RNA), MTT reduction assay (MTT), neutral red incorporation assay (NRI), Coomassie blue assay, and cellular growth rate assay], and on the ciliated protozoa Tetrahymena pyriformis GL [doubling time of T. pyriformis GL population assay (DTP)]. For each inorganic substance, the six bioassays allowed the toxicological index IC50 ("inhibitory concentration 50%") to be calculated. The IC50 values are useful to rank the tested elements and to compare the features of the six bioassays. The most sensitive assays were the RNA, MTT, NRI, and DTP assays. Moreover, the in vitro IC50 values correlated with the in vivo LD50 values; these results were close to those obtained with established lines of human, murine, or fish cells. The sensitivity and the complementarity of these bioassays would be in favor of their incorporation in a "battery" of tests used for toxicological screening studies of xenobiotics.

Comparative effects of essential and nonessential metals on preimplantation mouse embryo development in vitro

It is well recognized that deficiencies of essential trace elements during early development can result in structural abnormalities and/or embryonic death. Recently, there has been increasing interest in the concept that small excesses of essential metals can also have negative effects on the developing embryo. We hypothesized that, with respect to toxicity, metals with similar physico-chemical properties would act by similar mechanisms to influence the preimplantation embryo. In the current study we investigated the influence of four essential (Cu, Mn, Fe, Zn), and eight nonessential (Cr, Hg, Pb, V, Al, Ag, Cd, As) metals on mouse preimplantation embryonic development. Two cell stage mouse embryos were cultured for 72 h in media containing varying metal concentrations (0.05 - 200 microM). Embryo cell differentiation and proliferation were respectively assessed by scoring for blastocyst formation and final embryo cell number. Both nonessential and essential metals were embryotoxic at relatively low concentrations. However, in contrast to our expectations, at similar molar concentrations, redox active essential metals were less toxic than non-redox active nonessential metals. These data suggest that direct metal binding to critical membrane sites and/or intracellular ligands, including protein and nucleic acids, may trigger abnormal development and death prior to metal-associated oxidative damage.

Long-term exposure of male and female mice to trivalent and hexavalent chromium compounds: effect on fertility

Sexually mature male and female mice at 50 days of age were exposed to trivalent (Chromium chloride) or hexavalent (potassium dichromate) chromium compounds in drinking water for 12 weeks. The effects of the direct chromium exposure on fertility was assessed at day 140 of age. Fertility was significantly reduced in males exposed to the trivalent chromium compound. The number of implantation sites and the number of viable fetuses was significantly reduced in females impregnated by males exposed to the hexavalent chromium compound. The number of resorptions and dead fetuses was increased in females impregnated by males exposed to trivalent and hexavalent chromium compounds. The exposure of female mice to trivalent and hexavalent chromium compounds significantly reduced the number of implantation sites and the number of viable fetuses. The number of females with resorptions was significantly increased in hexavalent chromium exposed females. The number of resorptions was increased in trivalent and hexavalent exposed females. Body, seminal vesicles and preputial gland weights were significantly reduced in males exposed to trivalent and hexavalent chromium, whereas testes weight was significantly increased in males exposed to these compounds. Furthermore, ovarian weight was significantly increased in females exposed to trivalent and hexavalent chromium, whereas uterine weight was significantly decreased in trivalent chromium exposed females. In conclusion, the ingestion of trivalent and hexavalent chromium compounds by adult male and female mice would cause adverse effects on fertility and reproduction.

Placental effects of lead in mice

Although a number of studies in animal models have shown embryolethal and teratogenic lead effects when this element is administered by a parenteral route, the mechanism of the embryonary changes is well not established. In this study, the embryonic effects of parenteral lead exposure on day 9 of gestation were assessed in the Swiss mouse. Lead acetate trihydrate was injected intraperitoneally at 14, 28, 56 and 112 mg/kg. There was no maternal toxicity evidenced by death, reduced body weight gain or reduced food consumption. However, absolute placental weight at 112 mg/kg and relative placental weight at 14, 56 and 112 mg/kg were diminished significantly. The number of total implants, live and dead fetuses, sex ratio and fetal body weight were unaffected by lead exposure. Most sections of placenta showed vascular congestion, an increase of intracellular spaces and deposits of hyaline material of perivascular predominance. Trophoblast hyperplasia was also observed, whereas there was a reinforcement of the fibrovascular network in the labyrinth. It is concluded that the trophoblast hyperplasia observed in the placenta of pregnant mice after parenteral lead exposure at doses that are not toxic for the dam could act as a repairing mechanism of the extraembryonary tissues.

Assessment of the protective activity of monisoamyl meso-2,3-dimercaptosuccinate against methylmercury-induced maternal and embryo/fetal toxicity in mice

The protective activity of monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS), a new monoester of 2,3-dimercaptosuccinic acid (DMSA), on methylmercury-induced maternal and developmental toxicity was assessed in mice. A series of four Mi-ADMS injections was given s.c. at 0.25, 6, 24, and 48 h after oral administration of 25 mg/kg of methylmercury chloride (MMC) given on day 10 of gestation. Mi-ADMS effectiveness was tested at 0, 23.8, 47.6 and 95 mg/kg. Cesarean sections were performed on gestation day 18. All live fetuses were examined for external, internal, and skeletal abnormalities. Oral MMC administration resulted in an increase in the number of resorptions, and a decrease in fetal body weight, whereas the incidence of cleft palate, micrognathia, and skeletal variations was also increased in the fetuses of the MMC-treated groups. Although significant amelioration of MMC-induced embryolethality by Mi-ADMS was not noted at any dose, MMC-induced fetotoxicity was reduced by administration of this agent at 23.8, 47.6, and 95 mg/kg. However, the intrinsic toxicity of Mi-ADMS would be a restrictive factor for the possible therapeutic use of this chelator in pregnant women exposed to organic mercury.

Inhibition of human DNA ligase I activity by zinc and cadmium and the fidelity of ligation

Heavy metals, including zinc (Zn) and cadmium (Cd), are potentially important genotoxic agents in our environment. Here we report that human DNA ligase I, the major form of the enzyme in replicative cells, is a target for Zn and Cd ions. ZnCl2 at 0.8 mM caused complete inhibition of DNA ligase I activity, whereas only 0.04 mM CdCl2 was required to achieve a similar effect. Both metals affected all three steps of the reaction, namely, the formation of ligase-AMP intermediate, the transfer of the AMP to DNA and the ligation reaction that succeeds the formation of the AMP-DNA complex. Unlike F-ara-ATP and the natural protein inhibitor of DNA ligase-I, these metals may affect different domains of the enzyme. Moreover, these metal ions did not increase the rate of misligation of F-ara-A-modified DNA or mismatched DNA substrates, but considerable misligation was observed for the T:C mispairing. These data support the notion of high fidelity of the human DNA ligases and that the major action of these metal ions on the enzyme is their inhibitory function.