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A method for the simultaneous determination of monomethylmercury (MeHg(+)) and monoethylmercury (EtHg(+)) in soil/sediment samples was developed. The method involves eluting mercury species from the soil/sediment samples using 5M HCl containing 5mM Pd(2+) and 0.1M Cu(2+) and then extracting MeHg(+) and EtHg(+) into toluene as chlorides. These alkylmercury chlorides are then back-extracted into an aqueous EDTA solution, creating EDTA complexes. Finally, an emetine-dithiocarbamate (emetineCS2) solution is added to the EDTA solution to form emetineCS2-alkylmercury complexes. EmetineCS2-MeHg and emetineCS2-EtHg were separated using reverse-phase HPLC and then detected by the chemiluminescence reaction with tris(2,2'-bipyridine)ruthenium(III). The MeHg(+) and EtHg(+) calibration curves, using the peak height, were linear from 0.5 to 20ng (as Hg). The detection limit was 0.16ng/g (analyzing 1g soil or sediment). The procedure was validated by analyzing a certified reference material (ERM CC580, estuarine sediment). The MeHg(+) concentration determined using the proposed method was in good agreement with the certified value, and EtHg(+) was detected in the reference material. A preliminary study of the relationship between environmental mercury concentrations and MeHg(+) production was performed.

A simple and sensitive method with a fast sample preparation procedure is proposed for the determination of mercury species in plasma/serum. The method combines online high-performance liquid chromatography separation, Hg cold-vapor formation and inductively coupled plasma mass spectrometry detection. Prior to analysis, plasma (250 μL) was accurately pipetted into 15 mL conical tubes. Then, an extractant solution containing mercaptoethanol, L-cysteine and HCl was added to the samples following sonication for 10 min. Quantitative mercury extraction was achieved with the proposed procedure. Separation of mercury species was accomplished in less than 8 min on a C8 reverse phase column with a mobile phase containing 3% v/v methanol + 97% v/v (0.5% v/v 2-mercaptoethanol + 0.05% v/v formic acid). The method detection limits were found to be 12 ng L −1 , 5 ng L −1 and 4 ng L −1 for inorganic mercury, ethylmercury and methylmercury, respectively. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from NIST. Additional validation was provided by the analysis of a secondary reference serum sample from the INSQ-Canada. Finally, the method was successfully applied for the speciation of mercury in plasma samples collected from volunteers exposed to methylmercury through fish consumption. For the first time to our knowledge, levels of different species of Hg in plasma samples from riverside populations exposed to MeHg were determined.

Neurodevelopment as Gesell development scores (GDSs) in relation to mercury exposure in infants (3.95±1.8 ppm) were statistically (P=0.0001) different from those of infants from Porto Velho (3.84±5.5 ppm) and Bom Futuro (1.85±0.9 ppm). Differences in vaccine coverage among these populations resulted in significantly higher (P=0.0001) mean ethylmercury (EtHg) exposure in urban infants (150 μg) than in infants from either village (41.67 μg, Itapuã; 42.39 μg, Bom Futuro). There was an inverse significant (Spearmanr=−0.2300;P=0.0376) correlation between HHg and GDS for infants from Porto Velho, but not for the rural infants from Bom Futuro (Spearmanr=0.1336;P=0.0862) and Itapuã (Spearmanr=0.1666;P=0.5182). Logistic regression applied to variables above or below the median GDS showed that EtHg exposure (estimatedprobability=−0.0157;P=0.0070) and breastfeeding score (estimatedprobability=−0.0066;P=0.0536) score were significantly associated with GDS.Conclusion. In nurslings whose mothers are exposed to different levels of fish-MeHg (HHg), a higher score of neurological development at six months was negatively associated with exposure to additional TCV-EtHg. Results should be interpreted with caution because of unaccounted variables.

The 2008 EU regulation, which prohibits conventional incandescent light bulbs, is to be implemented in phases, completing in 2012. One of the possible substitutes is the compact fluorescent lamp (CFL), which, however, does contain up to 5 mg of mercury in its elemental or amalgamated form. The question arises as to the possible exposure of individuals to mercury as a result of lamp breakage during operation or when disconnected from the power supply. Therefore, an apparatus was built to shatter CFLs and drop the shards onto glycol-modified polyethylene terephthalate, a carpeted floor, or laminate floor under defined climatic parameters and operating conditions. Six CFLs of different types and mercury content were studied. After the breakage of a common CFL containing liquid mercury, concentrations up to 8000 ng/m(3) were reached in the chamber. Much lower peak values were obtained with amalgam-type lamps (414 ng/m(3)) or with lamps with a shatter-proof coating (60 ng/m(3)). It was found that ventilation can considerably reduce the indoor air concentration within 20 min. Acute health effects would only be expected if the mercury is not removed immediately. Careful collection and disposal of the lamp fragments would also prevent dwellers from the risk of long-term exposure.After accidental breakage of a compact fluorescent lamp (CFL) indoors, dwellers could be exposed to high mercury concentrations. From the results of our studies in test chambers and real rooms using different lamp types and scenarios, it was possible to estimate the possible human uptake of mercury by inhalation. Immediate action is important to reduce indoor mercury concentrations to a minimum level. The first step is to maximize ventilation followed by careful collection of spilled mercury.

In Poland, administered childhood vaccines still contain thimerosal as a preservative. Despite the access to mercury free formulas, the most of children are still vaccinated by thimerosal-containing vaccines (TCV) owing to economical reasons. That circumstances caused the rising discussion on potential harmful influence of TCVs on children health. The objective of this analysis was to determine an association of TCVs exposure with the risk of autism. Study population included 96 cases diagnosed with childhood or atypical autism and 192 controls matched individually by year of birth, gender, and physician's practice. Data on autism diagnose and vaccination history were from GPs. Data on the other possible autism risk factors were collected from mothers. Conditional logistic regression was used to assess the risk of autism due to TCVs exposure. No significant association was found between TCVs exposure and autism. After adjusting to potential confounders, odds ratios of the risk of autism developing for infants vaccinated with TCVs were 1.52 (95% CI: 0.29-11.11) for doses 12.5-87.5 microg, 2.78 (95% CI: 0.29-11.11) for 100-137.5 microg and 1.97 (95% CI: 0.37-18.95) for these exposedor = 150 microg. Our study revealed no evidence of an association between TCVs and autism.

The methylation of inorganic Hg by anaerobic bacteria in aquatic environments is considered to be the major pathway for methylmercury (MeHg) production. However, recent research has suggested that abiotic or chemical methylation by humic substances and other low-molecular-weight organic compounds in natural environments is also possible. Here, the aqueous photo-transformation of Hg(2+) to organomercurials was investigated in the presence of ketones, aldehydes and low molecular weight organic acids under UV irradiation. MeHg and/or ethylmercury (EtHg) were identified as the main organomercurial products by multiple analytical techniques, including chromatography-atomic spectrometry and molecular mass spectrometry and further confirmed by stable isotope tracer experiments. The yield of organomercurials was markedly influenced by pH, NaCl concentration, alkylation donor concentration and the presence of chelating ligands in the aqueous solution. Electron paramagnetic resonance spectrometry demonstrated that the radical reaction was not the predominating alkylation pathway, although methyl radicals were detected in the photo-alkylation procedure. A mechanism based on intra-molecular alkyl transfer in the Hg(2+)-low-molecular-weight organic compound complex is proposed. The present work helps us better understand of MeHg and EtHg photo-generation in natural environments.

Photodegradation of methyl mercury (MeHg) and ethyl Hg (EtHg) in sea water was studied by sunlight or ultraviolet (UV) light exposure, and by determining inorganic Hg produced by degradation. Sea water containing 1 microM MeHg or EtHg was exposed to sunlight or UV light. N-Acetyl-L-cysteine was added to the solution for preventing Hg loss during the light exposure. MeHg and EtHg in sea water were degraded by sunlight (280 nm), UV light A (320-400 nm) and UV light B (280-320 nm), though the amounts of inorganic Hg produced from MeHg were 1/6th to 1/12th those from EtHg. Inorganic Hg production was greater with increasing concentration of sea water. Degradation of MeHg and EtHg by the UV light A exposure was inhibited by singlet oxygen (1O2) trappers such as NaN3, 1,4-diazabicyclo[2,2,2]octane, histidine, methionine and 2,5-dimethylfuran. On the other hand, inhibitors or scavengers of superoxide anion, hydrogen peroxide or hydroxyl radical did not inhibit the photodegradation of alkyl Hg. These results suggested that 1O2 generated from sea water exposed to sunlight, UV light A or UV light B was the reactive oxygen species mainly responsible for the degradation of MeHg and EtHg.

OBJECTIVE: Exposure to thimerosal, a mercury-containing preservative that is used in vaccines and immunoglobulin preparations, has been hypothesized to be associated with increased risk of autism spectrum disorder (ASD). This study was designed to examine relationships between prenatal and infant ethylmercury exposure from thimerosal-containing vaccines and/or immunoglobulin preparations and ASD and 2 ASD subcategories: autistic disorder (AD) and ASD with regression. METHODS: A case-control study was conducted in 3 managed care organizations (MCOs) of 256 children with ASD and 752 controls matched by birth year, gender, and MCO. ASD diagnoses were validated through standardized in-person evaluations. Exposure to thimerosal in vaccines and immunoglobulin preparations was determined from electronic immunization registries, medical charts, and parent interviews. Information on potential confounding factors was obtained from the interviews and medical charts. We used conditional logistic regression to assess associations between ASD, AD, and ASD with regression and exposure to ethylmercury during prenatal, birth-to-1 month, birth-to-7-month, and birth-to-20-month periods. RESULTS: There were no findings of increased risk for any of the 3 ASD outcomes. The adjusted odds ratios (95% confidence intervals) for ASD associated with a 2-SD increase in ethylmercury exposure were 1.12 (0.83–1.51) for prenatal exposure, 0.88 (0.62–1.26) for exposure from birth to 1 month, 0.60 (0.36–0.99) for exposure from birth to 7 months, and 0.60 (0.32–0.97) for exposure from birth to 20 months. CONCLUSIONS: In our study of MCO members, prenatal and early-life exposure to ethylmercury from thimerosal-containing vaccines and immunoglobulin preparations was not related to increased risk of ASDs.

A novel solution cathode glow discharge (SCGD) induced vapor generation was developed as interface to on-line couple high-performance liquid chromatography (HPLC) with atomic fluorescence spectrometry (AFS) for the speciation of inorganic mercury (Hg(2+)), methyl-mercury (MeHg) and ethyl-mercury (EtHg). The decomposition of organic mercury species and the reduction of Hg(2+) could be completed in one step with this proposed SCGD induced vapor generation system. The vapor generation is extremely rapid and therefore is easy to couple with flow injection (FI) and HPLC. Compared with the conventional HPLC-CV-AFS hyphenated systems, the proposed HPLC-SCGD-AFS system is very simple in operation and eliminates auxiliary redox reagents. Parameters influencing mercury determination were optimized, such as concentration of formic acid, discharge current and argon flow rate. The method detection limits for HPLC-SCGD-AFS system were 0.67 μg L(-1) for Hg(2+), 0.55 μg L(-1) for MeHg and 1.19 μg L(-1) for EtHg, respectively. The developed method was validated by determination of certified reference material (GBW 10029, tuna fish) and was further applied for the determination of mercury in biological samples.

To establish a method for the detection of mercury species in aquatic products by liquid chromatography online coupled with cold vapor atomic fluorescence spectrometry(LC-CV-AFS) and to participate in the international proficiency tests to verify the method.Mercury species were extracted from aquatic samples by using ultrasonication-assisted acid extraction, separated by reversed phase liquid chromatography, decomposed into inorganic mercury ion with on line UV digestion system, and then determined by cold vapor atomic fluorescence spectrometry.Methylmercury, ethylmercury and inorganic mercury were baseline separated within 20 minutes. The linear range was 1-20 microg/L for the three species and the correlation coefficient ror = 0.999. The detection limits for methylmercury, ethylmercury and inorganic mercury were 1 microg/kg, 2 microg/kg and 1 microg/kg respectively. The recovery of samples for three spiked levels (10, 50 and 500 microg/kg) was in the range of 89%-106%. The relative standard deviations (RSDs) were less than 10%. The determined methylmercury contents of certified reference materials (CRMs) were agreed well with the certified values. The results of determined methylmercury values were satisfied (Z2) in two international proficiency tests, i.e., Food Analysis Performance Assessment Scheme (FAPAS, UK)-07115 test and International Atomic Energy Agency (IAEA)-452 test.The LC-CV-AFS method is simple, sensitive and accurate and could meet the demand for mercury speciation in aquatic products.

In connection with the dealkylation of methyl mercury (MeHg) and ethyl Hg (EtHg) with reactive oxygen-producing systems, we examined the ability of phagocytic cells to degrade MeHg or EtHg into inorganic mercury in vitro by collecting them from blood or peritoneal cavity of several species of animal. EtHg was readily degraded by human polymorphonuclear leukocytes (PMN), rat PMN, guinea-pig PMN, rabbit PMN, guinea-pig macrophages (M phi), human monocytes and guinea-pig eosinophils. In contrast, rat hepatocytes and the M phi hybridoma clone 39 cells were weaker in their degrading ability. Degradation of MeHg by these cells was always much weaker than EtHg, under identical conditions; however, by increasing the cell numbers, MeHg was appreciably degraded by human PMN, rat PMN and rabbit PMN. The reactive oxygen species mainly responsible for alkyl Hg degradation seemed to be hydroxyl radicals produced by M phi, and hypochlorous acid produced by PMN, monocytes and eosinophils. It was also suggested that the degradation of alkyl Hg by these cells might be an intraphagosomal event.

Retinol dehydratase is a sulfotransferase which is presumed to catalyze the dehydration of its substrate via a transient retinyl sulfate intermediate. Crystals (space group P2(1), unit-cell parameters a = 82.05, b = 66.61, c = 84.90 A, beta = 111.29 degrees ) are significantly improved by covalent modification of the protein with ethylmercury.

A simplified thiourea-based chromatography method, originally developed for methyl and inorganic mercury, was adapted to separate methylmercury (MeHg), ethylmercury (EtHg), and inorganic mercury (Hg(II)) in infants' hair. Samples were weighed and leached with an acidic thiourea solution. Leachates were concentrated on a polymeric resin prior to analysis by Hg-thiourea liquid chromatography/cold vapor atomic fluorescence spectrometry. All but one sample showed small amounts of EtHg, and four of the six analyzed samples had proportionally higher Hg(II) as a percent of total Hg. Breastfed infants from riverine Amazonian communities are exposed to mercury in breast milk (from high levels of maternal sources that include both fish consumption and dental amalgam) and to EtHg in vaccines (from thimerosal). The method proved sensitive enough to detect and quantify acute EtHg exposure after shots of thimerosal-containing vaccines. Based on work with MeHg and Hg(II), estimated detection limits for this method are 0.050, 0.10, and 0.10 ng g⁻¹ for MeHg, Hg(II), and EtHg, respectively, for a 20-mg sample. Specific limits depend on the amount of sample extracted and the amount of extract injected.

A method for trace level determination of organomercury species in different biota matrixes by using aqueous-phase propylation followed by headspace solid-phase microextraction (HS-SPME) and gas chromatography (GC) coupled to pyrolysis-atomic fluorescence spectrometry (Py-AFS) detection has been optimized. To maximize peak area and symmetry factors of methylmercury (MeHg) and ethylmercury (EtHg) analyzed as propyl derivatives, carrier and make-up flow rates were optimized by a user-defined experimental design. A multiple response simultaneous optimization was applied using the desirability function to achieve global optimal operating conditions. They were attained at 2 and 6 mL min(-1) as carrier and make-up gas flow rates, respectively. In addition, pyrolyser temperature was also optimized, yielding the best value at 750 degrees C. Limits of detection and quantification at the optimum conditions were 0.04 ng g(-1) and 0.13 ng g(-1) for both, MeHg and EtHg. The developed analytical procedure was validated with a certified reference material (DORM-2) and applied to the determination of organomercury incurred in waterfowl egg and fish samples.

Despite the necessity to differentiate chemical species of mercury in clinical specimens, there are a limited number of methods for this purpose. Then, this paper describes a simple method for the determination of methylmercury and inorganic mercury in blood by using liquid chromatography with inductively coupled mass spectrometry (LC-ICP-MS) and a fast sample preparation procedure. Prior to analysis, blood (250microL) is accurately weighed into 15-mL conical tubes. Then, an extractant solution containing mercaptoethanol, l-cysteine and HCl was added to the samples following sonication for 15min. Quantitative mercury extraction was achieved with the proposed procedure. Separation of mercury species was accomplished in less than 5min on a C18 reverse-phase column with a mobile phase containing 0.05% (v/v) mercaptoethanol, 0.4% (m/v) l-cysteine, 0.06molL(-1) ammonium acetate and 5% (v/v) methanol. The method detection limits were found to be 0.25microgL(-1) and 0.1microgL(-1) for inorganic mercury and methylmercury, respectively. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from the National Institute of Standards and Technology (NIST). The proposed method was also applied to the speciation of mercury in blood samples collected from fish-eating communities and from rats exposed to thimerosal. With the proposed method there is a considerable reduction of the time of sample preparation prior to speciation of Hg by LC-ICP-MS. Finally, after the application of the proposed method, we demonstrated an interesting in vivo ethylmercury conversion to inorganic mercury.

Isotope ratio measurements characterizing (202)Hg/(200)Hg in NIST SRM 3133 Mercury Standard Solution were undertaken by multicollector inductively coupled plasma mass spectrometry employing NIST SRM 997 Tl for mass bias correction by use of the slope and the intercept obtained from a natural logarithmic plot of each session of measurements of (202)Hg/(200)Hg against (205)Tl/(203)Tl. The calculated value of 1.285333 +/- 0.000192 (mean and one standard deviation, n = 40) for the mass bias corrected (202)Hg/(200)Hg was then used for mass bias correction of other Hg isotope pairs. Ratios of 0.015337 +/- 0.000011, 1.68770 +/- 0.00054, 2.3056 +/- 0.0015, 1.3129 +/- 0.0013, 2.9634 +/- 0.0038, and 0.67937 +/- 0.0013 (expanded uncertainty, k = 2) were obtained for (196)Hg/(198)Hg, (199)Hg/(198)Hg, (200)Hg/(198)Hg, (201)Hg/(198)Hg, (202)Hg/(198)Hg, and (204)Hg/(198)Hg, respectively. Reduction of Hg(II) to Hg(0) in solutions of SRM 3133 was then undertaken using SnCl(2), NaBH(4), UV photolysis in the presence of formic acid, and ethylation of Hg(II) using NaBEt(4.) These reactions induced significant isotope fractionation with maximum values of 1.17 +/- 0.07, 1.08 +/- 0.09, 1.34 +/- 0.07, and 3.59 +/- 0.09 per thousand (one standard deviation, 1SD, n = 5) for delta (202/198)Hg relative to the initial isotopic composition in the solution following 85-90% reduction of the Hg by SnCl(2), NaBH(4), UV photolysis, and ethylation with NaBEt(4), respectively. Mass-dependent fractionation was found to be dominant for all reduction processes.

Autism has been characterized as a behavioral disorder since it was first described by Leo Kanner in 1943. The number of autistic children has increased over the last decade. The incidence of autism was 1 in 10000 before the 1970s and has steadily increased to 1 in 150 in 2008 with a male:female predominance of 4:1. The cause of this epidemic has remained unknown, but several hypotheses have been studied. Many of these suggest an environmental trigger, such as the ethyl mercury contained in the preservative thimerosal, which has been used in vaccines since 1931. Other possible triggers associated with vaccinations are chemical toxins and live viruses. James has published studies suggesting a genetic predisposition in the families of autistic children, exposing them to a deficiency in glutathione and an inability to detoxify heavy metals. Vargas has shown autism to encompass ongoing inflammation in the brains of autistic children. The Hannah Poling vaccine decision was a landmark case. Poling's family was awarded funds for ongoing medical care of an autistic child who was found to have mitochondrial dysfunction exacerbated by vaccines that left her with autistic behavior and seizures. Several studies have emerged supporting the fact that a significant number of autistic children do have mitochondrial dysfunction. The impact that the Poling case will have on the ability of parents of autistic children to gain access to funds to enable them to properly care for their children remains to be seen.

Room temperature ionic liquids can be considered as environmentally benign solvents with unique physicochemical properties. Ionic liquids can be used as extractant phases in SDME, being compatible with chromatographic systems. A single-drop microextraction method was developed for separation and preconcentration of mercury species (MeHg(+), EtHg(+), PhHg(+) and Hg(2+)), which relies on the formation of the corresponding dithizonates and microextraction of these neutral chelates onto a microdrop of an ionic liquid. Afterwards, the separation and determination were carried out by high-performance liquid chromatography with a photodiode array detector. Variables affecting the formation and extraction of mercury dithizonates were optimized. The optimum conditions found were: microextraction time, 20 min; stirring rate, 900 rpm; pH, 11; ionic liquid type, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C(6)MIM][PF(6)]); drop volume, 4 microL; and no sodium chloride addition. Limits of detection were between 1.0 and 22.8 microg L(-1) for the four species of mercury, while the repeatability of the method, expressed as relative standard deviation, was between 3.7 and 11.6% (n=8). The method was finally applied to the determination of mercury species in different water samples.

Using synchrotron x-ray fluorescence mapping, we have examined the uptake and localization of organic mercury in zebrafish larvae. Strikingly, the greatest accumulation of methyl and ethyl mercury compounds was highly localized in the rapidly dividing lens epithelium, with lower levels going to brain, optic nerve, and various other organs. The data suggest that the reported impairment of visual processes by mercury may arise not only from previously reported neurological effects, but also from direct effects on the ocular tissue. This novel approach is a powerful tool for directly investigating the molecular toxicology of heavy metals, and should be equally applicable to the study of a wide range of elements in developing embryos.

The cloud point extraction (CPE) preconcentration of ultra-trace amount of mercury species prior to reverse-phase high performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) detection was studied. Mercury species including methyl-, ethyl-, phenyl- and inorganic mercury were transformed into hydrophobic chelates by reaction with sodium diethyldithiocarbamate, and the hydrophobic chelates were extracted into a surfactant-rich phase of Triton X-114 upon heating in a water bath at 40 degrees C. Ethylmercury was found partially decomposed during the CPE process, and was not included in the developed method. Various experimental conditions affecting the CPE preconcentration, HPLC separation, and ICP-MS determination were optimized. Under the optimized conditions, detection limits of 13, 8 and 6 ng l(-1) (as Hg) were achieved for MeHg(+), PhHg(+) and Hg(2+), respectively. Seven determinations of a standard solution containing the three mercury species each at 0.5 ng ml(-1) level produced relative standard deviations of 5.3, 2.3 and 4.4% for MeHg(+), PhHg(+) and Hg(2+), respectively. The developed method was successfully applied for the determination of the three mercury species in environmental water samples and biological samples of human hair and ocean fish.

BACKGROUND It has been hypothesized that early exposure to thimerosal, a mercury-containing preservative used in vaccines and immune globulin preparations, is associated with neuropsychological deficits in children. METHODS We enrolled 1047 children between the ages of 7 and 10 years and administered standardized tests assessing 42 neuropsychological outcomes. (We did not assess autism-spectrum disorders.) Exposure to mercury from thimerosal was determined from computerized immunization records, medical records, personal immunization records, and parent interviews. Information on potential confounding factors was obtained from the interviews and medical charts. We assessed the association between current neuropsychological performance and exposure to mercury during the prenatal period, the neonatal period (birth to 28 days), and the first 7 months of life. RESULTS Among the 42 neuropsychological outcomes, we detected only a few significant associations with exposure to mercury from thimerosal. The detected associations were small and almost equally divided between positive and negative effects. Higher prenatal mercury exposure was associated with better performance on one measure of language and poorer performance on one measure of attention and executive functioning. Increasing levels of mercury exposure from birth to 7 months were associated with better performance on one measure of fine motor coordination and on one measure of attention and executive functioning. Increasing mercury exposure from birth to 28 days was associated with poorer performance on one measure of speech articulation and better performance on one measure of fine motor coordination. CONCLUSIONS Our study does not support a causal association between early exposure to mercury from thimerosal-containing vaccines and immune globulins and deficits in neuropsychological functioning at the age of 7 to 10 years.

Objectives: To determine if thimerosal administration in amounts equivalent to vaccines content produces neurotoxic effects on the encephalon in postnatal hamsters and on experimentation animals' development. Design: Experimental, prospective, bietapic study. Setting: San Fernando Faculty of Medicine, Universidad Nacional Mayor de San Marcos. Biologic material: Seven-day old hamsters. Material: We divided 45 postnatal hamsters in three groups: group A (n = 15), group B (n = 15) and group C (n = 15). We administered three intramuscular equivalent doses of sucrose and thimerosal in 20 μL of physiological serum respectively to groups B and C on birth-days 7 (0,227 μg), 9 (0,216 μg) and 11 (0,220 μg). Group A received only 20 μL of saline solution. Main outcome measures: Body weight, encephalon weight, hamster's stature and encephalon histopathological alterations. Results: Anova and student t tests showed statistical significance in favor of low body weight, low encephalon weight and smaller stature in group C with respect to groups A and B hamsters (p

Objetivos: Determinar si la administración de timerosal, en cantidades equivalentes al contenido en las vacunas, produce efectos neurotóxicos a nivel encefálico en hámsteres de 7 días de nacidos y evaluar las influencias sobre el desarrollo de los animales de experimentación. Diseño: Estudio experimental, prospectivo y bietápico. Lugar: Bioterio de la Facultad de Medicina de San Fernando, Universidad Nacional Mayor de San Marcos. Material biológico: Hámsteres de 7 días de nacidos. Métodos: Se estudió 45 hámsteres divididos en tres grupos: grupo A (n = 15), grupo B (n = 15) y grupo C (n = 15). Se administró a los grupos B y C, por vía intramuscular, 3 dosis equivalentes de sucrosa y timerosal, respectivamente, los días 7 (0,227 μg), 9 (0,216 μg) y 11 (0,220 μg) de nacimiento, en un volumen de 20 μL de suero fisiológico. El grupo A solo recibió igual cantidad de suero fisiológico en los mismos días. Principales medidas de resultados: Peso corporal, peso encefálico, talla de los hámsteres y alteraciones histopatólógicas encefálicas. Resultados: Las pruebas Anova y t de student fueron significativas en favor al menor peso corporal, menor peso encefálico y menor talla del grupo C con respecto a los grupos A y B (p, Objectives: To determine if thimerosal administration in amounts equivalent to vaccines content produces neurotoxic effects on the encephalon in postnatal hamsters and on experimentation animals' development. Design: Experimental, prospective, bietapic study. Setting: San Fernando Faculty of Medicine, Universidad Nacional Mayor de San Marcos. Biologic material: Seven-day old hamsters. Material: We divided 45 postnatal hamsters in three groups: group A (n = 15), group B (n = 15) and group C (n = 15). We administered three intramuscular equivalent doses of sucrose and thimerosal in 20 μL of physiological serum respectively to groups B and C on birth-days 7 (0,227 μg), 9 (0,216 μg) and 11 (0,220 μg). Group A received only 20 μL of saline solution. Main outcome measures: Body weight, encephalon weight, hamster's stature and encephalon histopathological alterations. Results: Anova and student t tests showed statistical significance in favor of low body weight, low encephalon weight and smaller stature in group C with respect to groups A and B hamsters (p

Breastfeeding is the best natural protection infants have against morbidity and mortality, and the development of safe and effective vaccines has made it possible to immunize children against infectious disease. Both of these mechanisms for ensuring good health in children may be compromised by contact with mercury (Hg). Maternal exposure to environmental Hg during pregnancy can predispose nursing children to neurodevelopmental disorders. Despite the World Health Organization assurance that thimerosal-preserved vaccines are safe to use in infants, the United States, the European Union, and dozens of other countries have eliminated thimerosal as a vaccine preservative and stopped the immunization of children with such vaccines. Because of the increase in environmental pollution and the need to produce cheap and safe vaccines, there is a need to address the uncertainty of vaccine-ethylmercury risk of toxicity and Hg exposure during breastfeeding.

Today the most widespread human exposures to mercury are to mercury vapor emitted from amalgam tooth fillings, to ethylmercury as a preservative in vaccines, and to methylmercury in edible tissues of fish. This review will focus on the mechanisms of transport of these three species of mercury. All three species are freely moveable throughout the body. Inhaled vapor in view of its physical properties as an uncharged atomic gas is believed to be transported by passive diffusion. Methylmercury and ethylmercury also move freely in the body. Methylmercury, and presumably its closely related chemical cousin ethylmercury, cross cell membranes as complexes with small molecular weight thiol compounds, entering the cell in part as a cysteine complex on the large neutral amino acid carriers and exiting the cell in part as a complex with reduced glutathione on endogenous carriers. The implications of these mechanisms with regard to biological monitoring are discussed.

Brazilian newborns immunized with hepatitis-B (thimerosal containing vaccine, TCV) receive the first dose within 24 h if delivered in public hospitals, but at a later time if born in private hospitals. We compared neurodevelopment (ND) in infants born in a state hospital (immunized within 24 h) and in privately run hospitals (immunized 2-4 days postnatally).We used the Gesell Developmental Schedules in 82 healthy exclusively breastfed infants at 6 months to assess motor skills, language development, comprehension capacity and social skills.Compared to the group immunized 2-4 days after hospital discharge, the group immunized within 24 h showed no significant difference in ND delays. Despite the variation in gestational age (range 36-42 weeks) and TCV-ethylmercury (EtHg) dose (5.7-11.3 microg Hg/kg b.w.) at birth, time of exposure to TCV showed no significant association with ND. Gesell Developmental Score was not significantly correlated with total parenteral EtHg/unit of body mass neither with the relative increase in hair-Hg (as an additional challenge to prenatal Hg exposure).In breastfed infants, differences in early exposure to TCV-EtHg cannot portend clinical neurodevelopment delays at 6 months. We speculate that breastfeeding remains a significant strategy to improve central nervous system protection of infants facing early exposure challenges.

Because of increasing awareness of the potential neurotoxicity of even low levels of organomercury compounds, analytical techniques are required for determination of low concentrations of ethylmercury (EtHg) and methylmercury (MeHg) in biological samples. An accurate and sensitive method has been developed for simultaneous determination of methylmercury and ethylmercury in vaccines and biological samples. MeHg and EtHg were isolated by acid leaching (H2SO4–KBr–CuSO4), extraction of MeHg and EtHg bromides into an organic solvent (CH2Cl2), then back-extraction into Milli-Q water. MeHg and EtHg bromides were derivatized with sodium tetrapropylborate (NaBPr4), collected at room temperature on Tenax, separated by isothermal gas chromatography (GC), pyrolysed, and detected by cold-vapour atomic fluorescence spectrometry (CV AFS). The repeatability of results from the method was approximately 5–10% for EtHg and 5–15% for MeHg. Detection limits achieved were 0.01 ng g−1 for EtHg and MeHg in blood, saliva, and vaccines and 5 ng g−1 for EtHg and MeHg in hair. The method presented has been shown to be suitable for determination of background levels of these contaminants in biological samples and can be used in studies related to the health effects of mercury and its species in man. This work illustrates the possibility of using hair and blood as potential biomarkers of exposure to thiomersal.

Because of uncertainties associated with a possible rise in neuro-developmental deficits among vaccinated children, thimerosal-preserved vaccines have not been used since 2004 in the USA (with the exception of thimerosal-containing influenza vaccines which are routinely recommended for administration to pregnant women and children), and the EU but are widely produced and used in other countries. We investigated the impact of thimerosal on the total Hg in hair of 82 breast-fed infants during the first 6 months of life. The infants received three doses of the hepatitis-B vaccine (at birth, 1 and 6 months) and three DTP (diphtheria, tetanus, and pertussis) doses at 2, 4 and 6 months, according to the immunization schedule recommended by the Ministry of Health of Brazil. The thimerosal in vaccines provided an ethylmercury (EtHg) exposure of 25 microgHg at birth, 30, 60 and 120 days, and 50 microgHg at 180 days. The exposure to vaccine-EtHg represents 80% of that expected from total breast milk-Hg in the first month but only 40% of the expected exposure integrated in the 6 months of breastfeeding. However, the Hg exposure corrected for body weight at the day of immunization was much higher from thimerosal- EtHg (5.7 to 11.3 microgHg/kg b.w.) than from breastfeeding (0.266 microgHg/kg b.w.). While mothers showed a relative decrease (-57%) in total hair-Hg during the 6 months lactation there was substantial increase in the infant's hair-Hg (446%). We speculate that dose and parenteral mode of thimerosal-EtHg exposure modulated the relative increase in hair-Hg of breast-fed infants at 6 months of age.

A comprehensive method for simultaneous determination of methylmercury (MeHg) and ethylmercury (EtHg) in rice by capillary gas chromatography (GC) coupled on-line with atomic fluorescence spectrometry was developed. The experimental conditions, including the pyrolyzer temperature and flow rates of the make-up gas and sheath gas, were optimized in detail. The absolute detection limits (3sigma) were 0.005 ng as Hg for both MeHg and EtHg. The relative standard deviation values (n=5) for 10 ng Hg/mL of MeHg and EtHg were 2.5 and 1.3%, respectively. The method was evaluated by analyzing 2 certified reference materials (DORM-2 and GBW08508), and the determined values of MeHg and total mercury concentrations were in good agreement with the certified values. In addition, the recoveries of MeHg and EtHg spiked into a rice sample collected from Jiangsu province in China were 86 and 77%, respectively. The proposed method was applied to analysis of MeHg and EtHg in 25 rice samples cultivated in 15 provinces of China. In all samples, MeHg was detectable and no EtHg was found. The MeHg contents in rice samples ranged from 1.9 to 10.5 ng/g, accounting for 7-44% of the total mercury measured.

A novel, straightforward solid-phase extraction system for the determination of inorganic mercury and organomercury compounds in water is proposed. The analytes, in a buffer medium at pH 4.5, are sorbed as diethyldithiocarbamate complexes on a C 60 fullerene column an subsequently eluted and derivatized with sodium tetra- n -propylborate in ethyl acetate. Following elution, 1 μl of extract is injected into a gas chromatograph–mass spectrometer system. The proposed gas chromatography–mass spectrometry speciation method exhibits a linear range of 4–1 ng/ml, and a detection limit of 1.5 ng/l (sample volume, 50 ml). Its repeatibility, as relative standard deviation (RSD) (from 11 standards containing 50 ng/l for each analyte), is ca. 7%. No interferences from metals ions, such as Zn 2+ , Fe 3+ , Sb 3+ , As 3+ , Pb 2+ , Ni 2+ , Cu 2+ , Sn 2+ , Co 2+ , Mn 2+ and Cd 2+ were encountered at concentrations 1000 times higher than those of the mercury compounds. The method was used for the speciation of inorganic mercury, methylmercury and ethylmercury in various types of water including sea and waste water.

Thimerosal, also known as thimersal, Merthrolate, or sodiumethyl-mercurithiosalicylate, is an organic mercurial compound that is used in a variety of commercial as well as biomedical applications. As a preservative, it is used in a number of vaccines and pharmaceutical products. Its active ingredient is ethylmercury. Both inorganic and organic mercurials are known to interfere with glutamate homeostasis. Brain glutamate is removed mainly by astrocytes from the extracellular fluid via high-affinity astroglial Na+-dependent excitatory amino acid transporters, glutamate/ aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1). The effects of thimerosal on glutamate homeostasis have yet to be determined. As a first step in this process, we examined the effects of thimerosal on the transport of [3H]-d-aspartate, a nonmetabolizable glutamate analog, in Chinese hamster ovary (CHO) cells transfected with two glutamate transporter subtypes, GLAST (EAAT1) and GLT-1 (EAAT2). Additionally, studies were undertaken to determine the effects of thimerosal on mRNA and protein levels of these transporters. The results indicate that thimerosal treatment caused significant but selective changes in both glutamate transporter mRNA and protein expression in CHO cells. Thimerosal-mediated inhibition of glutamate transport in the CHO-K1 cell line DdB7 was more pronounced in the GLT-1-transfected cells compared with the GLAST- transfected cells. These studies suggest that thimerosal accumulation in the central nervous system might contribute to dysregulation of glutamate homeostasis.

Isotopically enriched HgO standards were used to synthesize CH3(200)Hg+ and C2H5(199)Hg+ using Grignard reagents. These species were employed for isotope dilution GC-ICPMS to study uptake and biotransformation of ethylmercury in mice treated with thimerosal, (sodium ethylmercurithiosalicylate) 10 mg L(-1) in drinking water ad libitum for 1, 2.5, 6, or 14 days. Prior to analysis, samples were spiked with aqueous solutions of CH3(200)Hg+, C2H5(199)Hg+, and 201Hg2+ and then digested in 20% tetramethylammonium hydroxide and extracted at pH 9 with DDTC/toluene. Extracted mercury species were reacted with butylmagnesium chloride to form butylated derivatives. Absolute detection limits for CH3Hg+, C2H5Hg+, and Hg2+ were 0.4, 0.2, and 0.6 pg on the basis of 3sigma of five separate blanks. Up to 9% of the C2H5Hg+ was decomposed to Hg2+ during sample preparation, and it is therefore crucial to use a species-specific internal standard when determining ethylmercury. No demethylation, methylation, or ethylation during sample preparation was detected. The ethylmercury component of thimerosal was rapidly taken up in the organs of the mice (kidney, liver, and mesenterial lymph nodes), and concentrations of C2H5Hg+ as well as Hg2+ increased over the 14 days of thimerosal treatment. This shows that C2H5Hg+ in mice to a large degree is degraded to Hg2+. Increased concentrations of CH3Hg+ were also observed, which was found to be due to impurities in the thimerosal.

ContextMercuric compounds are nephrotoxic and neurotoxic at high doses. Thimerosal, a preservative used widely in vaccine formulations, contains ethylmercury. Thus it has been suggested that childhood vaccination with thimerosal-containing vaccine could be causally related to neurodevelopmental disorders such as autism.ObjectiveTo determine whether vaccination with a thimerosal-containing vaccine is associated with development of autism.Design, Setting, and ParticipantsPopulation-based cohort study of all children born in Denmark from January 1, 1990, until December 31, 1996 (N = 467 450) comparing children vaccinated with a thimerosal-containing vaccine with children vaccinated with a thimerosal-free formulation of the same vaccine.Main Outcome MeasuresRate ratio (RR) for autism and other autistic-spectrum disorders, including trend with dose of ethylmercury.ResultsDuring 2 986 654 person-years, we identified 440 autism cases and 787 cases of other autistic-spectrum disorders. The risk of autism and other autistic-spectrum disorders did not differ significantly between children vaccinated with thimerosal-containing vaccine and children vaccinated with thimerosal-free vaccine (RR, 0.85 [95% confidence interval {CI}, 0.60-1.20] for autism; RR, 1.12 [95% CI, 0.88-1.43] for other autistic-spectrum disorders). Furthermore, we found no evidence of a dose-response association (increase in RR per 25 µg of ethylmercury, 0.98 [95% CI, 0.90-1.06] for autism and 1.03 [95% CI, 0.98-1.09] for other autistic-spectrum disorders).ConclusionThe results do not support a causal relationship between childhood vaccination with thimerosal-containing vaccines and development of autistic-spectrum disorders.

It was considered appropriate to update of the significance and use of the different mercury exposure indicators.The aim of the this paper was to correctly select biological media and sampling time and to understand the toxic kinetics of mercury for assessment of accurate biological monitoring.It was confirmed that mercury in blood (B-Hg) is a good indicator of recent exposure, while urinary mercury (U-Hg) indicates current exposure when mercury reaches the renal steady state. B-Hg values are greatly influenced by fish consumption, while the variables influencing U-Hg values are amalgam fillings, commercial gamma-globulin preparations, vaccines, topical remedies, environmental pollution and hobbies, occupational exposure and, partly, fish consumption. The speciation of mercury (Hg0, Hg++, methylmercury and ethylmercury) in biological media, should provide additional and important information in evaluating mercury toxicity.It was stressed that the appropriate choice of exposure indicators has to take account of the different variability factors and the characteristics of the toxic kinetics of mercury. The results of biological monitoring must be compared with references values, which are generally in the order of several micrograms/g creatinine, and limit values such as ACGIH BEI (U-Hg 35 micrograms/g creatinine and B-Hg 15 micrograms/l) or the DFG BAT (U-Hg 100 micrograms/l and B-Hg 25 micrograms/l).

While a number of studies remain to be completed, evidence is mounting that there is no demonstrable risk for infants immunized with vaccines containing thiomersal. Epidemiological studies in the US have shown no developmental or other central nervous system abnormalities resulting from exposure to vaccines containing thiomersal. During the initial evaluation of thiomersal in vaccines during 1999, the toxicological profile of ethyl mercury was unknown and presumed to be the same as that of methyl mercury. Enough evidence has accumulated since then to indicate the profiles of the two compounds are different in crucial aspects. To date, one study has measured blood levels of total mercury in vaccinated infants and reports only a brief low-level exposure with rapid excretion of mercury. It is not yet known for sure how much (if any) vaccine-derived ethyl mercury in the blood crosses the blood-brain barrier. For the most part, the use of thiomersal as a vaccine preservative has been convincingly shown to be safe. The scientific evidence is not yet sufficiently strong to provide the same level of assurance for thiomersal-containing vaccines for use in pregnant women or the premature or low birth weight infant. There is an increased sensitivity of the fetal brain to mercury whether it is ethyl or methyl mercury. While there is no evidence to support the contention, it is at least theoretically possible that very low birth weight premature infants may be at increased risk from thiomersal-containing vaccines. Until such time as the scientific evidence is to hand, thiomersal-free presentations of hepatitis B are to be preferred for the birth dose. Given the same levels of exposure, adults are at much lower levels of risk because of increased body mass. It is not possible to prove that thiomersal is completely safe-epidemiology can only quantify a risk, not prove its absence.

Gas chromatography/atomic absorption spectroscopy(GC/AAS) is a good method for the species analysis of organometallic compounds. But the traditional atomizers are not very suitable for this technology and all of them response only to one kind of signal--the concentration of the metallic atoms of the ground state. They can not give any information about the organic group of organometallic compounds and organic compounds which coexist with the former. For GC/AAS we want to design and manufacture a new kind of detector which is much more sensitive and has a much smaller dead volume and will sensitively and synchronously response to the atomization signal of organometallic compound and ionization signal of organic compound. The authors have noticed that the atomization of organometallic compound and ionization of organic compound have been existing in the same hydrogen flame. The question is how to gain and exchange and output the two signals which are completely different in characters. For this purpose we designed and manufactured a new type of horizontal pipe mini-flame atomization and ionization synchronous detector. The key part is a T type glass tube (80 mm x 13 mm x 10 mm i.d.) which covers horizontally on the jet of the mini-flame atomizer and a long pipe stainless steel collector (70 mm x 9.5 mm o.d. x 9 mm i.d.) is tightly inserted in the tube. The light beam of the hollow cathode lamp passes through the hydrogen flame along the axial center of the glass tube and the ground state metallic atoms in the flame diffuses to both ends of the tube along the axial center of the glass tube too. This process enriches the depth of the light absorption and then increases the sensitivity of atomization. At the same time the long pipe collector can enrich the collection efficiency of the ionization and increases the sensitivity and widens the linear range. So the detector can synchronously and sensitively detect the organometallic and organic compounds. The detection limit for atomization of the organometallic compound(diethylmercury) is 2.5 x 10(-11) g.s-1 and for ionization of the organic compound (benzene) is 1.0 x 10(-11) g.s-1. The linear range is 7.0 x 10(2) for atomization of diethylmercury (r = 0.9989) and 2.5 x 10(5) for ionization of benzene (r = 0.9992). The selectivity of the detector to the organic solvent under the optimum operating condition of atomization is 10(4)-10(7). The relative standard deviation (RSD, n = 11) of the peak area in the optimum operating conditions of atomization for the organometallic compound (diethylmercury) and of ionization for the organic compound (benzene) is 1.8% and 1.5% respectively. Under the same operating condition, the atomization and the ionization can not reach the optimum performance at the same time. If the atomization is in the optimum performance state, the performance for ionization is like a chromatographic thermal conductivity detector (TCD). The optimum performance of the atomization and ionization can be quickly adjusted by changing the flow rates of the corresponding gases such as H2, N2 and air.

In 1958, Minamata Disease was suggested to be organic mercury compounds intoxication. This suggestion was based on Hunter and Russel's report on occupational exposure to methylmercury. This report is known to have established the typical symptoms of methyl mercury intoxication. However, it has been widely believed since the official recognition of Minamata Disease (1956) that, at the moment of outbreak, no reports were available on organic mercury formation from inorganic mercury in acetaldehyde production from acetylene, or on organic mercury intoxication among workers in acetaldehyde production from acetylene. However, this was not the case. The formation of organic mercury from inorganic mercury used as a catalyst was reported by Vogt and Nieuwland in 1921. In 1930, Zangger reported several cases of organic mercury intoxication among workers in acetaldehyde production from acetylene. Soon after, Koelsch reported that the cases were methyl- and/or ethylmercury intoxication, and that such cases had been common since 1916. These reports were already available at the time of the Minamata Disease outbreak. However, Zangger's report, the most important of these three was not referred to until 1987, notwithstanding its listing in the references of Kurland et al.. Zangger's report was not referred to not by investigators, but by a lawyer. If these reports had been referred to at the outbreak of Minamata Disease, the number of victims in Minamata would have been minimized, and Minamata Disease in Niigata would have been prevented.

Chemicals/CAS: Biological Products; Ethylmercury Compounds; Food Additives; Pharmaceutical Preparations; Preservatives, Pharmaceutical; Thimerosal, 54-64-8

The route of formation and identification of the principal degradation products of thimerosal (thiomersal) has been undertaken. The initial oxidation to dithiosalicylic acid is followed by cleavage of the disulphide bond of the dithiosalicylic acid by the ethylmercuric ion to reform 1.5 mol of thimerosal with concurrent oxidation to form 0.5 mol of 2-sulfinobenzoic acid for each mole of dithiosalicylic acid. In the presence of copper ions 2-sulfobenzoic acid was also formed. A mechanism has been proposed which accounts for the stoichiometry of the cleavage reaction observed and the significance of the reaction is discussed.

The purpose of this work was to study possible hematological changes in carp (Cyprinus carpio L.) which might be induced by the experimental poisoning with metoxyethylmercury acetate which is used as fungicide. The experimental group of fishes was exposed to the named substance which was mixed with the feed during three weeks. The total lymphocytes number decreased in experimental group already at 7th day (p0.01), and remained almost at the same level, but considerably lower than the experimental group, until the end of the experiment. The number of small lymphocytes in the experimental group decreased also at the 7th day of the experiment (p0.01), and the decreasing tendency continued up to the end of the experiment. The number of large lymphocytes increased at the day 7th of the experiment (p0.01), and the increasing tendency continued until the end of the experiment. The population of large lymphocytes showed the cytopathological changes in the form of cytoplasmic vacuoles and cytoplasmic shoots. The frequency of these changes increased through the experiments.

Mercury compounds are among the most serious environmental pollutants. In this communication, the potentiating effects of organic and inorganic mercuries on clastogen-induced chromosome aberrations were studied in Chinese hamster CHO K1 cells. Post-treatment with monoalkylated mercuries--methyl mercuric chloride (MeHgCl) and ethyl mercuric chloride (EtHgCl)--increased the number of breakage- and exchange-type aberrations induced by 4-nitroquinoline 1-oxide (4NQO) and methyl methanesulfonate. With the DNA crosslinking agents mitomycin C (MMC) and cisplatin, MeHgCl enhanced both types of aberrations while EtHgCl enhanced breakage-type aberrations only. Since these monoalkylated mercuries did not show clastogenic effects by themselves under the present experimental conditions, the increases in chromosome aberrations were not additive. Dialkylated mercuries (dimethyl mercury and diethyl mercury) and inorganic mercuries (HgCl and HgCl2) did not show any potentiating effects. When MMC- or 4NQO-treated cells were post-treated with MeHgCl during the G1 phase, both breakage- and exchange-type aberrations were enhanced. Treatment with EtHgCl during the G1 phase also enhanced both types of aberrations induced by 4NQO. With MMC, however, G1 treatment with EtHgCl did not show any potentiating effect. MeHgCl and EtHgCl treatments during the G2 phase enhanced breakage-type aberrations only. Based on these results, the following possible mechanisms for potentiation of clastogenicity by monoalkylated mercuries were suggested; (1) they interfere with repair of base lesions induced by 4NQO and MMS during the pre-replicational stage, thereby increasing unrepaired DNA lesions which convert into DNA double-strand breaks in S phase, (2) MeHgCl (but not EtHgCl) also inhibits repair of crosslinking lesions during the pre-replicational stage, and (3) their G2 effects enhance breakage-type aberrations only.

Diffuse exanthema with fever followed by superficial nonfollicular aseptic pustules was observed in an 11-year old boy after conducting a thiomersal epicutaneous test and manipulation of a broken medical thermometer. The patient healed within two days without any treatment. The initial responsibility of mercury and its derivatives, and the primary sensitization and relevance of the epicutaneous tests are discussed. Mercury and its derivatives should be limited as much as possible in medicine and cosmetology.

Degradation of methyl mercury (MeHg) and ethyl Hg (EtHg) with reactive oxygens was studied in vitro by using peroxidase-hydrogen peroxide (H2O2)-halide and rose bengal-ultraviolet light A systems. For this purpose, the direct determination method for inorganic Hg was employed. Both systems could effectively degrade EtHg, and MeHg to some extent. Degradation of MeHg and EtHg with the myeloperoxidase (MPO)-H2O2-chloride system was inhibited by MPO inhibitors (cyanide and azide), catalase, hypochlorous acid (HOCI) scavengers (glycine, alanine, serine and taurine), 1,4-diazabicyclo[2,2,2]octane and 2,5-dimethylfuran, but not by hydroxyl radical scavengers (ethanol and mannitol). Iodide was more effective than chloride as the halide component. Lactoperoxidase (LPO) could substitute for MPO in the iodide, but not the chloride system. With MPO-H2O2-chloride, MPO-H2O2-iodide and LPO-H2O2-iodide systems, we observed the increased degradation of EtHg in deuterium oxide (D2O) medium better than that in H2O medium. The D2O effect upon MeHg degradation was extremely weak. These results suggested that HOCl (or HOI) might be also capable of degrading MeHg and EtHg, besides the hydroxyl radical already reported by us. Singlet oxygen could degrade EtHg but not MeHg.

Degradation of methyl mercury (MeHg) and ethyl Hg (EtHg) with oxygen free radicals was studied in vitro by using three well-known hydroxyl radical (•OH)-producing systems, namely Cu2+-ascorbate, xanthine oxidase (XOD)-hypoxanthine (HPX)-Fe(III)EDTA and hydrogen peroxide (H2O2)-ultraviolet light B. For this purpose, the direct determination method for inorganic Hg was employed. MeHg and EtHg were readily degraded by these three systems, though the amounts of inorganic Hg generated from MeHg were one half to one third those from EtHg. Degradation activity of XOD-HPX-Fe(III)EDTA system was inhibited by Superoxide dismutase, catalase and the •OH scavengers and stimulated by H2O2. Deletion of the •OH formation promoter Fe(III)EDTA from XOD-HPX-Fe(III)EDTA system resulted in the decreased degradation of MeHg and EtHg, which was enhanced by further addition of the iron chelator diethylenetriamine pentaacetic acid. In all these cases, a good correlation was observed between alkyl Hg degradation and deoxyribose oxidation determining •OH. By contrast, their degradation appeared to be unrelated to either Superoxide anion\((O_{2^ - } )\) production or H2O2 production alone. We further confirmed that H2O2 (below 2 mM) itself did not cause significant degradation of MeHg and EtHg. These results suggested that •OH, but not\(O_{2^ - } \) and H2O2, might be the oxygen free radical mainly responsible for the degradation of MeHg and EtHg.

Anti-thymocyte globulin (ATG), a horse antiserum to human thymus tissue, has been shown to induce granulocytic differentiation of the HL-60 human leukemia cell line. In this paper we describe the effect of ATG on leukemic blasts and its effect on other human leukemia cell lines in vitro. The in vitro differentiation effect of ATG was observed in blasts from two patients with leukemia and the human leukemia cell line K562. The differentiation effect of ATG was attributable to its preservative, thimerosal, separable from ATG by high pressure liquid chromatography or dialysis. Subsequent studies with thimerosal alone showed it to induce differentiation in leukemic blasts from three patients and the human leukemia cell lines U937, K562, and KG-1. The differentiation effect of thimerosal is blocked by a sulfhydryl-protective agent, dithiothreitol, suggesting that the mechanism of differentiation may be mediated via a sulfhydryl group-dependent process.

Recent studies have demonstrated a limited bactericidal activity of Cialit in the preservation of otologic transplants. The authors therefore performed several tests following routine treatment of the grafts. First, the contamination of allogenic ossicles was studied; afterwards, the bactericidal activity of Cialit was tested against standardized germs and clinical isolates. At the highly toxic concentration of 1:2000, Cialit is bactericidal. For clinical purposes, however, the less toxic solution of 1:5000 is generally used, which is not sufficiently safe against certain resistant clinical isolates. The fact that the activity of Cialit depends on its concentration explains the controversial findings in the literature. Furthermore, it is doubtful whether a weaker solution would prevent transmission of an HIV or hepatitis infection. Therefore, the authors recommend the autoclaving of otologic allografts. This also has forensic reasons; for example if the serologic status of the donor is unknown. As ossicles become brittle under this procedure, the authors now use sculptured parts of teeth, in which the hydroxyl-apatite is much more compact. The preformed prostheses can be autoclaved without problem. More than 150 reconstructions have proved the acceptance of this cheap implant material. Furthermore, forensic problems with ossicles from corpses do not arise.