Spontaneous Magnetic Superdomain Wall Fluctuations in an Artificial Antiferromagnet.

Collective dynamics often play an important role in determining the stability of ground states for both naturally occurring materials and metamaterials. We studied the temperature dependent dynamics of antiferromagnetically ordered superdomains in a square artificial spin lattice using soft x-ray photon correlation spectroscopy. We observed an exponential slowing down of superdomain wall motion below the antiferromagnetic onset temperature, similar to the behavior of typical bulk antiferromagnets. Using a continuous time random walk model we show that these superdomain walls undergo low-temperature ballistic and high-temperature diffusive motions.

Mercury exposure from dental filling placement during pregnancy and low birth weight risk.

Several European countries have guidelines suggesting that women should not receive mercury-containing dental amalgam fillings during pregnancy. One concern raised by several studies is that mercury exposure during pregnancy may lead to decreased birth weight. A population-based, case-control study was designed to investigate whether placement of mercury-containing fillings in 1993-2000 during pregnancy increased the low-birth-weight risk. Cases and controls were sampled from enrollees of a dental insurance plan with live singleton births in Washington State; 1,117 women with low-birth-weight infants (< 2,500 g) were compared with a random sample of 4,468 women with infants weighing 2,500 g or more. The results indicated that 13% of a dentally insured population had one or more restorative procedures during pregnancy that, regardless of chemical composition, did not increase the low-birth-weight risk (odds ratio = 0.96, 95% confidence interval: 0.88, 1.05). The 4.9% of the women (n = 249) who had at least one mercury-containing amalgam filling during pregnancy were not at an increased risk for a low-birth-weight infant (odds ratio = 0.75, 95% confidence interval: 0.45, 1.26) and neither were women who had 4-11 amalgam fillings placed (odds ratio = 1.00, 95% confidence interval: 0.27, 3.68). This study found no evidence that mercury-containing dental fillings placed during pregnancy increased low-birth-weight risk.

Nuclear factor kappaB activation by muscarinic receptors in astroglial cells: effect of ethanol.

Activation of muscarinic receptors leads to proliferation of astroglial cells and this effect is inhibited by ethanol. Among the intracellular pathways involved in the mitogenic action of muscarinic agonists, activation of the atypical protein kinase C zeta (PKC zeta) appears to be of most importance, and is also affected by low ethanol concentrations. PKC zeta has been reported to activate nuclear factor kappaB (NF-kappaB), a transcription factor that has been shown to play an important role in cell proliferation. The aim of this study was, therefore, to determine whether muscarinic receptors would activate NF-kappaB in astroglial cells, whether such activation would play a role in the mitogenic action of muscarinic agonists, and whether it would represent a possible target for ethanol. Carbachol activated NF-kappaB in human 1321N1 astrocytoma cells, as evidenced by translocation of the p65 subunit of NF-kappaB to the nucleus, phosphorylation and degradation of IkappaBalpha in the cytosol, and increase NF-kappaB binding to DNA. Carbachol also induced translocation of p65 to the nucleus in primary rat astrocytes. Carbachol-induced NF-kappaB activation was mediated by the M3 subtype of muscarinic receptors and appeared to involve Ca(2+) mobilization and activation of PKC epsilon and PKC zeta, but not PI3-kinase and mitogen-activated protein kinase. The NF-kappaB peptide inhibitor SN50, but not the inactive peptide SN50M, strongly inhibited carbachol-induced astrocytoma cells proliferation and p65 translocation to the nucleus. Increased DNA synthesis was also antagonized by the IkappaBalpha kinase inhibitor BAY 11-7082. Ethanol (25-100 mM) inhibited the translocation of p65 and the binding of NF-kappaB to DNA in both 1321N1 astrocytoma cells and primary rat cortical astrocytes. Together, these results suggest that activation of NF-kappaB by muscarinic receptors in astroglial cells is important for carbachol-induced DNA synthesis and that ethanol-mediated inhibition of cell proliferation may be due in part to inhibition of NF-kappaB activation.

Genetic polymorphisms of superoxide dismutase in Parkinson's disease.

Oxidative stress reactions may contribute to the pathogenesis of Parkinson's disease (PD). The superoxide dismutases potentially play significant roles in PD by detoxifying superoxide radical. We developed genomic DNA and cDNA-based sequencing assays to identify genetic variants in the copper/zinc superoxide dismutase (SOD1) and manganese superoxide dismutase (SOD2) genes. No genetic variants were detected in the gene encoding SOD1 in DNA from 45 idiopathic PD cases and 49 controls from a population-based case-control study. However, we identified a previously described polymorphism of the mitochondrial targeting sequence consisting of a C47T in exon 2 of SOD2, which results in an alanine to valine substitution. We analyzed this SOD2 variant in DNA from 155 cases and 231 controls from the same study, using an allele-specific fluorogenic 5' nuclease assay, and found no differences in the distributions of allelic frequencies. These results indicate that SOD gene variants do not contribute to PD pathogenesis.

Mercuric ion attenuates nuclear factor-kappaB activation and DNA binding in normal rat kidney epithelial cells: implications for mercury-induced nephrotoxicity.

Mercuric ion (Hg(2+)), one of the strongest thiol-binding agents known, mediates the toxicity associated with elemental, inorganic, and organic mercurial compounds. Studies of cellular events associated with Hg(2+) toxicity have focused largely on disruption of cell membranes and impairment of mitochondrial functions. In contrast, few studies have sought to define the specific molecular mechanisms through which Hg(2+) might affect toxicity via alteration of thiol-dependent signal transduction pathways that regulate cell proliferation and survival. Of particular interest in this regard is the effect of Hg(2+) on nuclear factor-kappaB (NF-kappaB), a pleiotropic transcriptional factor that is known to require reduced cysteine moieties at critical steps of activation and DNA binding. Here, we evaluated the effects of Hg(2+) on the expression of NF-kappaB in normal rat kidney epithelial (NRK52E) cells, a principal target of Hg(2+) toxicity. The lipopolysaccharide (LPS)-inducible form of NF-kappaB was readily detected in kidney cells and has been characterized as the p50p65 heterodimer. NF-kappaB-DNA binding was prevented in a dose-related manner by Hg(2+) (0-55 microM) in vitro when added to DNA binding reactions containing the nonthiol reducing agent Tris(2-carboxyethyl)phosphine hydrochloride (TCEP). Similarly, Hg(2+) at the same concentrations prevented DNA binding of a human recombinant wild-type p50p50 homodimer in binding reactions, and this effect was attenuated using a mutant form of the p50 protein containing a cys(62)-->ser(62) mutation. The inhibition of p50-DNA binding by Hg(2+) was reversible in a dose-related manner in vitro by competitive thiols DTT, GSH, and l-cysteine in binding reactions. In contrast, competitive thiols added to nuclear binding reactions were unable to reverse attenuation of LPS-mediated NF-kappaB-DNA binding affinity when cells were pretreated in vivo with Hg(2+) at concentrations as low as 2 microM prior to LPS administration. Immunoblot analyses indicted that Hg(2+) pretreatment of kidney cells substantially diminished, in a dose-related manner, the concentration of p65 translocated into the nucleus following LPS administration. Additionally, Hg(2+) pretreatment impaired both the phosphorylation and degradation of IkappaBalpha, suggesting a specific effect on NF-kappaB activation at the level of IkappaBalpha proteolysis. Finally, Hg(2+) at concentrations as low as 5 microM significantly diminished NF-kappaB-mediated transcriptional activity when administered to kidney cells transiently transfected with an NF-kappaB-driven luciferase reporter gene (pLuc-4xNF-kappaB) prior to LPS treatment. These findings demonstrate that Hg(2+), at low cellular concentrations, attenuates NF-kappaB activation at sites associated with IkappaBalpha phosphorylation and degradation, nuclear translocation of the p50p65 heterodimer, and association of p50-cys(62) with the DNA kappaB binding site. Attenuation of NF-kappaB activation by Hg(2+) through these mechanisms may underlie apoptotic or other cytotoxic responses that are known to be associated with low level Hg(2+) exposure in kidney epithelial cells.

Effects of 2,3-dimercapto-1-propanesulfonic acid (DMPS) on tissue and urine mercury levels following prolonged methylmercury exposure in rats.

Methylmercury, a potent neurotoxicant, accumulates in the brain as well as the kidney during chronic exposure. We evaluated the capacity of 2,3-dimercapto-1-propanesulfonic acid (DMPS), a tissue-permeable metal chelator, to reduce brain, kidney, and blood Hg levels and to promote Hg elimination in urine following exposure of F-344 rats to methylmercury hydroxide (MMH) (10 ppm) in drinking water for up to 9 weeks. Inorganic (Hg2+) and organic (CH3Hg+) mercury species in urine and tissues were assayed by cold vapor atomic fluorescence spectroscopy (CVAFS). Following MMH treatment for 9 weeks, Hg2+ and CH3Hg+ concentrations were 0.28 and 4.80 microg/g in the brain and 51.5 and 42.2 microg/g in the kidney, respectively. Twenty-four hours after ip administration of a single DMPS injection (100 mg/kg), kidney Hg2+ and CH3Hg+ declined 38% and 59%, whereas brain mercury levels were slightly increased, attributable entirely to the CH3Hg+ fraction. Concomitantly, Hg2+ and CH3Hg+ in urine increased by 7.2- and 28.3-fold, respectively, compared with prechelation values. A higher dose of DMPS (200 mg/kg) was no more effective than 100 mg/kg in promoting mercury excretion. In contrast, consecutive DMPS injections (100 mg/kg) given at 72-h intervals significantly decreased total mercury concentrations in kidney, brain, and blood. However, the decrease in brain and blood mercury content was restricted entirely to the CH3Hg+ fraction, consistent with the slow dealkylation rate of MMH in these tissues. Mass balance calculations showed that the total amount of mercury excreted in the urine following successive DMPS injections corresponds quantitatively to the total amount of mercury removed from the kidney, brain, and blood of MMH-exposed rats. These findings confirm the efficacy of consecutive DMPS treatments in decreasing mercury concentrations in target tissue and in reducing overall mercury body burden. They demonstrate further that the capacity of DMPS to deplete tissue Hg2+ is highly tissue-specific and reflects the relative capacity of the tissue for methylmercury dealkylation. In light of this observation, the inability of DMPS to reduce Hg2+ levels in brain or blood may explain the inefficacy of DMPS and similar chelating agents in the remediation of neurotoxicity associated with prolonged MMH exposure.

Quantitative evaluation of urinary porphyrins as a measure of kidney mercury content and mercury body burden during prolonged methylmercury exposure in rats.

Changes in urinary porphyrin excretion patterns (porphyrin profiles) during prolonged mercury exposure are attributable to mercury accumulation in the kidney and to consequent effects of Hg2+ on renal porphyrin metabolism. In the present study, we evaluated the quantitative relationship of urinary porphyrin concentrations to mobilizable renal mercury content, using the metal chelator 2,3-dimercapto-1-propanesulfonic acid (DMPS) to modulate kidney mercury levels. Rats exposed to methylmercury hydroxide (MMH) at 10 ppm in drinking water for 6 weeks were treated with up to 3 consecutive doses of DMPS (100mg/kg, ip) at 72-h intervals. Consistent with previous findings, the concentrations of pentacarboxyl- (5-) and copro- (4-) porphyrins and of an atypical porphyrin specific to mercury exposure, precoproporphyrin, were significantly elevated in urine of MMH-exposed rats, compared with that of rats exposed to distilled water (dH2O) for the same period. Consecutive DMPS treatments of MMH-exposed rats significantly decreased kidney concentrations of total, as well as Hg2+ and CH3Hg+ species, and promoted increased urinary mercury excretion. Concomitantly, DMPS treatment decreased both kidney and urinary porphyrin concentrations, consistent with depletion of renal mercury levels. Regression analyses demonstrated a high correlation (r approximately 0.9) between prechelation urinary porphyrins and postchelation urinary mercury levels and also between prechelation urinary porphyrins and prechelation kidney mercury concentrations. These findings demonstrate that urinary porphyrin concentrations relate quantitatively to DMPS-mobilizable mercury in the kidney and, therefore, serve as a biochemical measure of renal mercury content.

Effects of ozone exposure on nuclear factor-kappaB activation and tumor necrosis factor-alpha expression in human nasal epithelial cells.

In this study we investigated a possible mechanism of the human airway inflammatory response to inhaled ozone (O(3)). Cultures of human nasal epithelial (HNE) cells, initiated from excised nasal turbinates and grown on collagen-coated Transwell tissue culture inserts, were exposed to 120, 240, or 500 ppb O(3) for 3 h. An electron spin resonance (ESR) signal that changed with time suggested free radical production in HNE cells exposed to O(3). Nuclear protein extracts were analyzed for the activated transcription factor NF-kappaB by electrophoretic mobility-shift assay (EMSA), and showed a small dose-response activation of NF-kappaB that coincided with O(3)-induced free radical production. Basal media were analyzed for the presence of tumor necrosis factor-alpha (TNF-alpha) using the enzyme-linked immunosorbent assay (ELISA). In cultures exposed to 120 ppb O(3), the mean TNF-alpha concentration was not significantly different from those exposed to air. However, exposure to 240 and 500 ppb O(3) significantly increased mean TNF-alpha expression, relative to controls, 16 h after exposure. These results support the hypothesis that the human airway epithelium plays a role in directing the inflammatory response to inhaled O(3) via free radical-mediated NF-kappaB activation.

Health effects of long-term mercury exposure among chloralkali plant workers.

BACKGROUND: Inorganic mercury is toxic to the nervous system, kidneys, and reproductive system. We studied the health effects of mercury exposure among former employees of a chloralkali plant that operated from 1955 to 1994 in Georgia. METHODS: Former plant workers and unexposed workers from nearby employers were studied. Exposure was assessed with a job-exposure matrix based on historical measurements and personnel records. Health outcomes were assessed with interviews, physical examinations, neurological and neurobehavioral testing, renal function testing, and urinary porphyrin measurements. Exposure-disease associations were assessed with multivariate modeling. RESULTS: Exposed workers reported more symptoms, and tended toward more physical examination abnormalities, than unexposed workers. Exposed workers performed worse than unexposed subjects on some quantitative tests of vibration sense, motor speed and coordination, and tremor, and on one test of cognitive function. Few findings remained significant when exposure was modeled as a continuous variable. Neither renal function nor porphyrin excretion was associated with mercury exposure. CONCLUSIONS: Mercury-exposed chloralkali plant workers reported more symptoms than unexposed controls, but no strong associations were demonstrated with neurological or renal function or with porphyrin excretion.

Examination of dietary methylmercury exposure in the Casa Pia Study of the health effects of dental amalgams in children.

This study examined methylmercury concentrations in blood of children participating in the Casa Pia Study of the Health Effects of Dental Amalgams in Children over a 1-yr period and related them to their diets in terms of fish and other seafood consumption. One hundred and fifty children between the ages of 8 and 10 yr who were residents of the Casa Pia School System of Lisbon, Portugal, participated. Parents or caregivers completed a food frequency questionnaire designed specifically for this study at baseline. Children provided urinary and blood samples for mercury determinations at baseline and at 1 yr following placement of dental tooth fillings. Mercury levels in fish samples from children's diets were also obtained. Mercury determinations in urine, blood, and fish were performed using cold vapor atomic fluorescence spectroscopy. The mean value of baseline methylmercury concentrations in blood increased as the report of seafood consumption increased, although not statistically significantly. However, blood methylmercury and total mercury concentrations were significantly lower at 1-yr follow-up than at baseline. Sixty-one percent of parents/caregivers reported that their children consumed fish on a weekly basis. The fish offered at a sample of the schools contained low levels of methylmercury (range 13.9-23.6 ng/g). Thus, children participating in the Casa Pia dental amalgam study are exposed to low dietary levels of methylmercury by way of fish consumption, and this finding was reflected in the low mean blood methylmercury concentrations observed. The present findings indicate that dietary methylmercury is not a significant source of mercury exposure and is not likely to confound the association of dental amalgam mercury with potential health effects in the present study.

HPLC methods for analysis of porphyrins in biological media.

Changes in porphyrin concentrations in biological media may serve as biological indicators of exposure and toxicity from a wide variety of drugs and chemical agents. This unit describes procedures for quantitative extraction of porphyrins from urine, feces, blood, and biological tissues as well as their separation and analysis by HAPLY spectrofluorometrc techniques.

Determination of methyl mercury in whole blood by ethylation-GC-CVAFS after alkaline digestion-solvent extraction.

A method for the determination of methyl mercury in whole blood samples based on ethylation-gas chromatography-cold vapor atomic fluorescence spectrometry after alkaline digestion-solvent extraction is described. The extraction procedure and conditions were optimized, and the matrix interference after extraction was critically investigated. The storage stability of MeHg in blood samples and a series of extracts was determined. The method detection limit was found to be approximately 0.02 ng/g for a 0.5-g blood sample with relative standard deviations of less than 10%. The accuracy and precision were evaluated by summarizing the quality-control (QC) data generated over a one and one half year period. Appropriate procedures for sample collection, transportation, and storage were adapted to the method. Using this method accompanied by explicit QC protocols and procedures, background levels of MeHg and total mercury in blood for 150 8-10-year-old Portuguese children with nonoccupational and nonamalgamal exposure were determined and reported with summarized QC data.

Inhibition of NF-kappaB-DNA binding by mercuric ion: utility of the non-thiol reductant, tris(2-carboxyethyl)phosphine hydrochloride (TCEP), on detection of impaired NF-kappaB-DNA binding by thiol-directed agents.

Mercuric ion (Hg(2+)), a potent thiol inhibitor, prevents expression of nuclear factor kappaB (NF-kappaB) by mercaptide bond formation with a critical cysteine moiety (cys(62)) on the p50 subunit required for DNA binding. NF-kappaB-DNA binding is typically measured in reaction mixtures in which dithiothreitol (DTT) or other thiol reductants are used to maintain cys(62) in the reduced state. However, the presence of thiol reductants prevents accurate assessment of the Hg(2+) concentration required to prevent NF-kappaB-DNA binding because of competitive mercaptide bond formation. In the present studies we evaluated the efficacy of tris(2-carboxyethyl)phosphine-HCl (TCEP), a non-thiol reducing agent which does not bind Hg(2+), on NF-kappaB-DNA binding in vitro, using recombinant p50 protein and a (32)P-labelled kappaB oligonucleotide. We also measured the minimal Hg(2+) concentration required to prevent this interaction in the presence of either reagent. DTT promoted NF-kappaB-DNA binding in concentrations from 0.25 to 2.6mM in binding reactions. However, in the presence of 0.25mM DTT, inhibition of NF-kappaB binding was seen only at Hg(2+) concentrations greater than 100 microM and results were highly variable. In contrast, TCEP promoted NF-kappaB-DNA binding in a dose-related manner in concentrations from 0.25 to 6mM. In the presence of even 6mM TCEP, Hg(2+) prevented NF-kappaB-DNA binding at concentrations as low as 20 microM in binding reactions. Similar findings were observed with regard to the thiol alkylating agent N-ethylmaleimide (NEM). These findings demonstrate the utility of TCEP as reductant in nuclear binding reaction assays involving the interaction of thiol constituents. They also demonstrate inhibition of NF-kappaB-DNA binding at Hg(2+) concentrations comparable to those known to initiate toxicity and apoptotic cell death in vivo.

Induction of glutamate-cysteine ligase (gamma-glutamylcysteine synthetase) in the brains of adult female mice subchronically exposed to methylmercury.

Methylmercury (MeHg) is widely known for its potent neurotoxic properties. One proposed mechanism of action of MeHg relates to its high affinity for sulfhydryl groups, especially those found on glutathione (GSH) and proteins. Previous studies have shown that acute MeHg exposure results in an increase in the mRNA for the rate-limiting enzyme in GSH synthesis, glutamate-cysteine ligase (GLCL) (also known as gamma-glutamylcysteine synthetase). In this study, we evaluated the effects of subchronic (12-week) MeHg exposure at 0, 3 or 10 ppm in the drinking water on GSH levels, GLCL catalytic (GLCLC) and regulatory subunit mRNA and protein levels, and GLCL activity in brain, liver and kidney tissue of C57B1/6 female mice. Contrary to previous findings in rats, there were no changes in GSH concentration in any of the tissues examined. However, there was an increase in GLCLC protein in the brain, which was accompanied by a 30% increase in GLCL activity. We conclude that up-regulation of GSH synthetic capacity in the brains of mice is a sensitive biomarker of subchronic MeHg exposure.

The role of glutathione in chronic adaptation to oxidative stress: studies in a normal rat kidney epithelial (NRK52E) cell model of sustained upregulation of glutathione biosynthesis.

Reduced glutathione (GSH) is considered to play a central role in protection of cells from oxidant injury. However, the question remains as to whether sustained elevation of intracellular GSH levels, as compared with the ability to rapidly upregulate GSH synthesis, is more important with respect to protection of cell constituents from oxidative stress. To address this question, we conducted studies to evaluate the direct influence of chronically increased endogenous GSH content on chemically induced intracellular free radical formation and oxidative stress using a kidney epithelial cell model adapted to sustain intracellular GSH concentrations in excess of eightfold that observed in unadapted parent kidney cells. Elevated GSH levels in adapted cells were found to be attributable, at least in part, to coordinately increased amounts of both the regulatory and catalytic subunits of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in GSH synthesis. Studies using electron spin resonance (ESR) spectroscopy and scanning laser cytometry demonstrated that cells having sustained elevation of GSH levels did not attenuate free radical formation and associated oxidative stress compared with parent cells when treated with the prooxidant chemicals, menadione or potassium dichromate. In contrast, nonadapted kidney parent cells treated 18 h after initial prooxidant challenge displayed significantly attenuated free radical signals. Additionally, cells adapted to sustain excess GSH were somewhat more sensitive than parent cells in terms of resistance to prooxidant (chromate) toxicity, as determined by cell viability assays. These findings suggest that the capacity of cells to rapidly upregulate GSH synthesis, rather the ability to chronically sustain elevated intracellular GSH levels, may play a more important role in terms of protection from cytotoxicity associated with prooxidant chemical exposures.

Activation of NF-kappaB in normal rat kidney epithelial (NRK52E) cells is mediated via a redox-insensitive, calcium-dependent pathway.

Renal tubular epithelial cells are largely resistant to oxidant-induced injury despite their capacity to accumulate relatively high concentrations of potentially damaging prooxidant and thiol-depleting agents. In the present study, we tested the hypothesis that such resistance may be attributable to a lack or deficiency of signaling transduction pathways through which reactive oxidants have been shown to promote the activation of NF-kappaB, a transcriptional factor that is known to mediate the inducible expression of a wide variety of genes that are involved in inflammatory and other cytotoxic reactions in numerous cell types. NF-kappaB was found to be readily activated following exposure of cultured normal rat kidney epithelial (NRK52E) cells to bacterial lipopolysaccharide (LPS). However, in contrast to findings with many other cell types, the activation of NF-kappaB by LPS was not substantially altered either by pretreatment of cells with the thiol antioxidant, N-acetylcysteine, or by glutathione (GSH) depletion. Moreover, reactive oxidants and oxidative stress-generating chemicals were completely without effect with respect to NF-kappaB activation in NRK52E cells, even following GSH depletion. In contrast, LPS activation of NF-kappaB was substantially attenuated by the intracellular Ca2+ chelator, Quin 2AM, and by the Ca-channel inhibitor, ruthenium red. Moreover, thapsigargin, a Ca-ATPase inhibitor, promoted NF-kappaB activation comparable to that observed by LPS. Additionally, staurosporine, a Ca-dependent protein kinase C inhibitor, substantially decreased LPS-mediated NF-kappaB activation. These results demonstrate that the LPS-inducible expression of NF-kappaB in renal epithelial cells, in contrast to many other cell types, is not responsive to oxidative stress and is regulated, at least in part, by redox-insensitive modulation of intracellular calcium levels. These findings provide a basis for the highly tissue-specific expression and function of NF-kappaB in kidney epithelial cells, which may underlie their resistance to oxidant-mediated cytotoxicity.

Behavioral effects of low-level exposure to Hg0 among dental professionals: a cross-study evaluation of psychomotor effects.

A Across-study design was used to evaluate the sensitivities of five psychomotor tasks previously used to assess preclinical effects of low-level Hg0 (urinary < or =55 microg/l). Pooling dental professional subject populations from six studies conducted over the last 6 years, a larger study population was obtained with a high degree of uniformity (N = 230). The five psychomotor tests were: Intentional Hand Steadiness Test (IHST); Finger Tapping: The One-Hole Test: NES Simple Reaction Time (SRT); and Hand Tremor. Multivariate analyses were conducted following the hierarchical analysis of multiple responses (HAMR) approach. First, multiple scores of each test were combined into a single-factor (or related summary) variable and its reliability was estimated. Second. multiple regression analyses were conducted including log-transformed [Hg0]U levels, age, gender, and alcohol consumption in each model. Computed were both B and bu, the magnitudes of the log-Hg0 standardized coefficient. respectively uncorrected and corrected for dependent variable attenuation due to unreliability. Results indicated remarkable differences in the effects of relative level of Hg0 on psychomotor performance. Significant associations were found for the IHST factor (B = 0.415, p < 10(-6)), followed by finger tapping, which was relatively meager and insignificant (B 0.141, p = 0.17). The IHST results hold the greatest occupational relevance for dental professionals who rely on manual dexterity in restorative dentistry. Further, this statistical approach is recommended in future studies for condensation of multiple scores into summary scores with enhanced reliabilities useful in correcting for attenuation relationships (B(u)s) with exposure levels.

Neurobehavioral effects from exposure to dental amalgam Hg(o): new distinctions between recent exposure and Hg body burden.

Potential toxicity from exposure to mercury vapor (Hg(o)) from dental amalgam fillings is the subject of current public health debate in many countries. We evaluated potential central nervous system (CNS) toxicity associated with handling Hg-containing amalgam materials among dental personnel with very low levels of Hg(o) exposure (i.e., urinary Hg <4 microg/l), applying a neurobehavioral test battery to evaluate CNS functions in relation to both recent exposure and Hg body burden. New distinctions between subtle preclinical effects on symptoms, mood, motor function, and cognition were found associated with Hg body burden as compared with those associated with recent exposure. The pattern of results, comparable to findings previously reported among subjects with urinary Hg >50 microg/l, presents convincing new evidence of adverse behavioral effects associated with low Hg(o) exposures within the range of that received by the general population.