ZINC AND POLYMORPHONUCLEAR LEUKOCYTE FUNCTION

Intracellular zinc uptake and concentration is one of the determinants of oxygen consumption, phagocytosis and bactericidal capacity of neutrophils.     

Developmental neurotoxicology

The developing brain has a distinctive set of characteristics that make it unusually sensitive to damage by toxic agents. Mechanistic understanding of the vulnerability of the immature nervous system to various chemicals is important from a preventive perspective but has also frequently given us new insights into maturation of neural circuitry. This review examines some of the developmental consequences of contact with various exogenous agents, including metals, solvents, pharmaceuticals, and natural products. This review emphasizes how subtle suboptimal brain function rather than acute toxicity can be a consequence of chemical exposures occurring during ontogenesis. The rate of brain aging may be influenced by events taking place in embryogenesis, following a prolonged asymptomatic period. The potential for appearance of adverse effects after prolonged latent periods is underscored.     

Effects of Vitamin E pretreatment on subacute toxicity of mixture of Co, Pb, and Hg nitrate-induced nephrotoxicity in rats

The aim of the study was to prove that Vitamin E has some beneficial effects on the kidneys of rats by protecting them from the toxicity of certain heavy metals. The protective effect of Vitamin E on Co, Pb, or Hg nitrate and a mixture of them induced nephrotoxicity was tested in a 3-months-old Norway strain (inberd) rat (Raltus norvigus) weighing 100–120 g. A study was carried out, which comprised one control group and five experimental groups. In this experiment, nitrate salts of Co, Pb, or Hg were administered subcutaneously (s.c.) either alone (0.5 mg/100 g body weight) for 4 weeks or as a mixture (0.25 mg/100 g body weight); Vitamin E internal control (250 IU/100 g body weight) was administered by oral gavage for 4 weeks, Vitamin E pretreatment for 7 days was followed by concomitant administration of Co, Pb, and Hg, respectively and Vitamin E pretreatment for 7 days, followed by concomitant administration of mixture of three heavy metals for 4 weeks. Blood and kidney tissue samples were taken from the control and all the experimental groups for biochemical and histological study. Nephrotoxicity was characterized by histopathological as well as renal function data. The main pathological changes in the kidney after Co administration were shrunken and degeneration of renal tubule cells, disturbance in their position, size, shape, and staining affinity. Treatment with Hg caused desquamation, necrosis, atrophy, and loss of renal tubule cells and glomeruli. Lead intoxication had a profound effect on the structure and consequently on the function of the rat kidney. Most renal tubule cells were very dense, dehydrated with obscure cytoplasmic details. Most nuclei were shrunken and pyknotic. Also, most glomeruli revealed shrinkage and widening of capsular space. On the other hand, subacute exposure with the mixture of the three heavy metals showed marked destruction and distortion of the renal tubule cells. Marked fibrosis between the damaged tubules was also seen. On the other hand in the recovery groups, i.e., in groups II and III, the previously observed histopathological changes were still present with regression of their intensity. Four-week oral administration with Vitamin E (250 IU/100 g body weight) revealed no abnormal histological findings as compared with the normal kidney of the control animal, except for some Malpighian corpuscles which demonstrated wide capsular space, and spherical masses were seen within the glomeruli. After pretreatment with Vitamin E for 7 days, followed by treatment with (0.5 mg/100 g body weight ) Co, Pb, or Hg nitrate alone or with their mixture (0.25 mg/100 g body weight) for 4 weeks, an improvement in the histological changes were observed compared to those previously seen in groups II and III. The glomeruli showed minimal degenerated changes, the tubular arrangement and cytoplasmic basophilia more or less similar to the normal control. It was also found that the heavy metals were investigated both alone and in combination; the serum creatinine and blood urea level were significantly increased, and this elevation was diminished by Vitamin E pretreatment.

According to the present results, it is concluded that combined exposure to a mixture of Vitamin E and examined heavy metals can minimize the histological alteration and diminish the serum creatinine and blood urea level. Also, it was found that the rank order of metal cytotoxicities was Hg > Co > Pb.     

Heavy-metal and microbial depuration of the clam Ruditapes decussatus and its effect on bivalve behavior and physiology

The bivalve Ruditapes decussatus was evaluated as a possible biomonitor of heavy-metal contamination. Concentrations of copper (Cu), cobalt (Co), iron (Fe), nickel (Ni), and manganese (Mn) were measured in R. decussatus. Water and sediment samples were collected at two stations of Timsah Lake in Ismailia, Egypt, from October to November 2002, using atomic absorption spectrophotometry (AAS). Results from the heavy-metal and microbial analyses indicated that site II was less contaminated than site I. The bivalve showed accumulation of metals, with a bioaccumulation factor (BAF) greater than 4. The bioaccumulation of metals varied strongly according to the sampling site. After 48 h of depuration, Fe, Ni, Co, Cu, and Mn were reduced significantly, to 46.8% and 47.7%, 19.9% and 20.3%, 27.3% and 27.9%, 35.9% and 36.6%, and 18.2% and 26.6%, compared with the initial concentrations, in clam tissue at the two stations. In bivalves from site II the counts of total bacteria, fecal coliforms, and bacterial pathogens were reduced by more than 90%, whereas phage counts were only reduced by 56% after 4 days of depuration. The depuration of bivalves collected from the heavily polluted site (I) was not effective, as coliforms were reduced only by 85% after 4 days, whereas counts of pathogens and pathogenic indicators such as Vibrio, fecal Streptococcus, and coliphage decreased to less than 50% of the initial concentration. The time necessary to decrease contamination to 10%, 50%, and 90% for clams at both stations was consistently shorter for heavy metals than for microorganisms. Investigation of the effects of heavy-metal and microbiological depuration on valve movement and physiological rates (oxygen consumption and ammonia excretion) was carried out on R. decussatus to test the utility of physiological stress indices in assessing the health of depurated animals. Clams in the experimental tanks exhibited various states of activity, which were rated by identifying and scoring (0-4) the different parameters, including shell gap, siphon extension, and foot protrusion. Moreover, an increase in ammonia excretion was usually associated with an increase in respiration rate. The oxygen-to-nitrogen ratio provided a sensitive indicator of bivalve health. It can be concluded that shellfish monitoring and depuration data depended on the initial concentration of the pollutants. There were differences in the physiological responses of clams from the two sites during the periods of pre- and postdepuration of the contaminants. There was a significant correlation between reduction of metal concentration in clam tissue and enhancement of valve movement, as well as activity and increasing respiration rate.     

Population Genetic Structure of Earthworms (Lumbricus rubellus) in Soils Contaminated by Heavy Metals

The genetic structure of earthworm (Lumbricus rubellus) populations from plots (N=3) contaminated by sewage sludge (containing Cd, Cu, Pb, Zn) and reference plots (N=3) was compared. Earthworms (N=30–40 per plot) were collected during May 2000 and electrophoretic analyses were used to assess genetic variation at three polymorphic loci (GPI, LAP, PGM). Allele and genotype frequencies for GPI and PGM differed significantly between sludge and reference populations. Sludge populations were characterized by a reduced frequency of the most common genotype and allele at these loci, and the presence of alleles not found in the reference population. Allele and genotype frequencies did not differ significantly among individual plots within the sludge or the reference population. These results suggest that certain alleles and genotypes may be more sensitive to the effects of heavy metals. Multi-locus heterozygosity was significantly higher in the sludge population compared to the reference population; the proportion of individuals heterozygous at two or more loci was more than 15% higher in the sludge population. Results demonstrate that measures of population genetic structure in earthworms may represent useful biological indicators for the assessment of impacted terrestrial habitats.     

Heavy metals in soil, vegetables and fruits in the endemic upper gastrointestinal cancer region of Turkey

The environmental exposure to heavy metals is a well-known risk factor for cancer. We investigated levels of seven different heavy metals, (Co, Cd, Pb, Zn, Mn, Ni and Cu) in soil, fruit and vegetable samples of Van region in Eastern Turkey where upper gastrointestinal (GI) cancers are endemic. Heavy metal contents of the samples were determined by flame atomic absorption spectrometer. Four heavy metals (Cd, Pb, Cu and Co) were present in 2- to 50-fold higher concentrations whereas zinc levels were present in 40-fold lower concentrations in soil. The fruit and vegetable samples were found to contain 3.5- to 340-fold higher amounts of the six heavy metals (Co, Cd, Pb, Mn, Ni and Cu) tested. The volcanic soil, fruit and vegetable samples contain potentially carcinogenic heavy metals in such a high levels that these elements could be related to the high prevalence of upper GI cancer rates in Van region.     

Multimarker approach in transplanted mussels for evaluating water quality in Charentes, France, coast areas exposed to different anthropogenic conditions

An active biomonitoring experiment was performed using mussels collected at a clean site, Fier d'Ars, and transplanted to two locations, outside the harbor of La Rochelle and in the Baie de L'Aiguillon along the coast of Charentes (French Atlantic coast) beginning in April for several months. Mussels were collected in June and October. The cadmium, copper, and zinc concentrations of all resident and transplanted mussel samples and the polycyclic aromatic hydrocarbon and polychlorinated biphenyl concentrations in some mussel samples and in the sediment samples were determined. Mussel response was evaluated for several biochemical biomarkers: concentrations of metallothionein, activities of glutathione S-transferase and acetylcholinesterase (AChE) and levels of thiobarbituric reactive substance (TBARS). The physiological status of the animals was assessed using the condition index. A principal component analysis performed with the chemical and biochemical results of the evaluations of the resident and transplanted mussels collected in June allowed them to be separated into three groups: resident mussels from la Rochelle with high metal and TBARS levels, resident mussels from Baie de L'Aiguillon with a very high condition index, and resident mussels from Fier d'Ars and transplanted mussels at La Rochelle and Baie de L'Aiguillon with low TBARS and AChE activities. Strong seasonal variation from June to October of all parameters was noted. Mussels transplanted to La Rochelle appeared to be the most "polluted" in their pollutant concentrations and biochemical responses; moreover, the La Rochelle site had the highest concentration of organics in sediments of all the sites. The choice of Fier d'Ars as a reference site may be questionable because some of the biomarker responses of the mussels were higher than expected there, although these pollutants in mussels and sediment were present at the lowest concentrations measured.     

Association of expired nitric oxide with urinary metal concentrations in boilermakers exposed to residual oil fly ash

BACKGROUND: Exposure to metal-containing particulate matter has been associated with adverse pulmonary responses. Metals in particulate matter are soluble, hence are readily recovered in urine of exposed individuals. This study investigated the association between urinary metal concentrations and the fractional concentration of expired nitric oxide (F(E)NO) in boilermakers (N = 32) exposed to residual oil fly ash (ROFA). METHODS: Subjects were monitored at a boiler overhaul site located in the New England area, USA. F(E)NO and urine samples were collected pre- and post-workshift for 5 consecutive workdays. Metals investigated included vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), and lead (Pb). RESULTS: The median F(E)NO was 7.5 ppb (95% CI: 7.4-8.0), and the median creatinine-adjusted urinary metal concentrations (mug/g creatinine) were: vanadium, 1.37; chromium, 0.48; manganese, 0.30; nickel, 1.52; copper, 3.70; and lead, 2.32. Linear mixed-effects models indicated significant inverse exposure-response relationships between log F(E)NO and the log-transformed urinary concentrations of vanadium, manganese, nickel, copper, and lead at several lag times, after adjusting for smoking status. CONCLUSIONS: Urine samples may be utilized as a biomarker of occupational metal exposure. The inverse association between F(E)NO and urinary metal concentrations suggests that exposure to metals in particulate matter may have an adverse effect on respiratory health.     

A study of the leachate toxicity of metal-containing solid wastes using Daphnia magna

This paper examines the ecotoxicity of different actual inorganic wastes containing some potentially toxic metals commonly found in many industrial residues and the reduction in ecotoxicity obtained when the wastes are submitted to a solidification/stabilization process. The ecotoxicity was assessed as defined in the Spanish regulations on hazardous wastes, by means of the Daphnia magna Straus acute toxicity test applied to the toxicity characteristic leaching procedure (TCLP) waste leachate. On the basis of the EC50 values of the individual metals and the effect of the pH of the aqueous medium on D. magna, we have explored a method for estimating the toxicity of the TCLP waste leachate by calculating its EC50 value in the D. magna test. Although the method is only valid in cases in which a clear cause for the toxicity exists, the procedure described allows us to more completely explain the observed effects on the daphnids. The ecotoxicity of the residues after stabilization is less than that of the untreated waste, generally as a consequence of the reduction in metal leachability achieved by the immobilization treatment. The stabilization process was analyzed in terms of both the chemical and the ecotoxicological parameters, and the influence of leachate pH on the objectives of waste treatment is discussed.