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At least 19 recordsLinked to original sources
PubMed1999

Thimerosal positivities: patch testing to methylmercury chloride in subjects sensitive to ethylmercury chloride.

The aim of this paper was to evaluate whether methylmercury chloride (MeHgCl) aq., when patch tested in a group of thimerosal-positive subjects reacting to ethylmercury chloride (EtHgCl), might be a reliable model for the better understanding of interactions between alkylmercury compounds and the skin. 19 out of 21 consecutive patients who previously had given positive patch-test reactions to both ethylmercury chloride 0.0165% eth.(EtHgCl, 0.615 mM) and MeHgCl 0.031% aq.(1.23 mM), and negative reactions to thiosalicylic acid 0.05% (3.24 mM) aq./eth. 50/50, were repatch tested to 8 microl of MeHgCl 0.031% aq. and to 8 microl of aq. solutions containing MeHgCl mixed with cysteine, glutathione, ZnSO4, MgSO4, MnSO4, ZnCl2, MgCl2 and MnCl2, respectively. The results showed that cysteine, glutathione and Zn(II) salts were able to abolish the positive reactions, demonstrating the rôle played by both thiol groups and Zn(II) itself. Patch tests concomitantly carried out in 16 out of 19 patients to 8 microl of aqueous MeHgCl and to 8 microl of aqueous solutions containing MeHgCl and MeHgCl mixed to fragment 56-61 of metallothionein I (MT I), MT I and MT II-Zn, respectively, revealed that all the MTs tested were able to reduce or to inhibit the reactions, demonstrating the effect of the thiol groups. Due to the close chemical similarities to EtHgCl and to its water solubility, MeHgCl seems to be a suitable model for evaluating the reactivity of alkylmercury compounds in the skin. We speculate that both EtHg- and MeHg-derivatives are xenobiotics with similar reactivity. However, the lack of clinical relevance of the reactions to both alkyl compounds lead us to conclude that, since environmental exposure does not seem to play a pivotal rôle, they probably have mostly to do with compounds included in in the standard series, and are elicited by reduced function of physiological SH chelators.

Adult↗
PubMed1985

Interaction of alkylmercuric compounds with sodium selenite. III. Biotransformation, levels of metallothioneinlike proteins and endogenous copper in some tissues of rats exposed to methyl or ethylmercuric chloride with and without sodium selenite.

The biotransformation efficiency of alkylmercurial compounds was studied in rat liver, kidneys, blood, and brain after 2-week administration of methylmercuric chloride (MeHg) and ethylmercuric chloride (EtHg) at doses of 0.25 or 2.5 mg Hg/kg, alone or in combination with sodium selenite (Se) at a level of 0.5 mg Se/kg. Simultaneously, the level of metallothioneinlike proteins (MTP) and endogenous copper (Cu) was monitored in tissues of control rats and intoxicated rats. Regardless of the dose, the highest concentrations of inorganic mercury from both the alkylmercurials was found in the rat kidneys. Sodium selenite had a variable effect on the amount of inorganic mercury liberated, depending on the organ and the molar ratio of Hg:Se administered. A statistically significant increase in the levels of MTP and endogenous Cu, compared with control group, was found only in the kidneys of intoxicated rats. This increase was dependent on the concentration of inorganic mercury liberated by biotransformation of alkylmercurials. The observed changes appeared when the level of inorganic mercury exceeded 10 micrograms Hg/g tissue and reached a plateau at about 40 micrograms Hg/g tissue. In the presence of selenium the plateau of MTP and Cu levels were no observed in the kidneys, regardless of the amount of inorganic mercury liberated.

Animals↗
PubMed1999

DNA sequence and expression of a defective mer operon from Pseudomonas K-62 plasmid pMR26.

pMRB01 cloned from Pseudomonas K-62 plasmid pMR26 conferred bacterial hypersensitivity to organomercurials. DNA sequence analysis of a 2.3-kb SacI-Aor51HI fragment encompassing the whole region required for expression of the hypersensitive phenotype, revealed three open reading frames. The DNA sequence of these frames had 82.5%, 99.2% and 97.0% homology with the pDU1358 merR, merB and merD, respectively. The pMRB01 mer operon differs from the already known mer operon by the absence of the merT, merP and merA genes in this plasmid. An inverted repeat-like sequence upstream from the predicted merR was observed suggesting that this defective mer operon could be part of a transposon-like structure. Induction experiments and maxicell analysis of the mer-polypeptide showed that the lyase enzyme encoded by pMRB01 merB gene is mercurial-inducible and regulated by the transacting product of the merR gene. These results suggest that the hypersensitivity to organomercurials resulted from the expression of lyase activity encoded by the defective mer operon in the absence of reductase activity. The lyase enzyme encoded by pMRB01 merB catalyzes the protonolysis of the C-Hg bond of both arylmercury and alkylmercury compounds.

Amino Acid Sequence↗
PubMed1997

[Determination of alkylmercuric compounds in human body fluids by gas chromatography--atomic absorption spectrophotometry].

In order to detect trace of alkylmercuric compounds in human body fluids, a highly sensitive, selective and rapid method, based on the coupling of gas chromatography with atomic absorption spectrophotometry, has been developed. The transfer-tube was made up of Teflon, with stainless steel tubes in the two sides. The atomization of alkylmercuric compounds was performed in quartz tube. The quantitative determination of alkylmercuric compounds in urine and blood samples collected from the workers exposing to metallic mercury, has been extensively carried out in this work. The optimal Westoo program was used to enrich methylmercuric chloride in samples, Extracts of methylmercuric chloride in benzene were determined by GC-AAS, with a total recovery of more than 90%. Dimethylmercury in samples was extracted once by xylene. Then the extracts were determined, with a total recovery of 65%-70%. The detectable limit for mercury was 0.01ng. The methylation of mercury was confirmed in our experiment. This method can be used for the determination of other metallic compounds.

Alkylmercury Compounds↗
PubMed1998

Thimerosal positivities: the rôle of SH groups and divalent ions.

For a better understanding of the mechanistic details of the interactions of organomercury compounds inside the skin, 32 subjects who previously had given positive patch-test reactions to thimerosal (TH) and negative reactions to thiosalicylic acid, were divided into 2 groups. 16 subjects were repatch tested to ethylmercury chloride (EtHgCl) and to solutions containing EtHgCl mixed with L-cysteine and glutathione, respectively. The remaining 16 were repatch tested to EtHgCl and to solutions containing EtHgCl mixed with chlorides of Zn, Mg, and Mn, respectively. The results showed that whilst L-cysteine, glutathione and ZnCl2 were able to abolish or to reduce the positive reactions to EtHgCl, chlorides of Mg and Mn were unable to do so. Patch tests revealed that in causing positive reactions to TH, EtHg probably interacted with thiol groups and with Zn ions, as in biological systems when causing toxic effects. The limited number of TH reactions in the general population, the constant presence of concomitant positive reactions to EtHgCl and MeHgCl, and the lack of cross-reactivity with other organic or inorganic mercury compounds, lead us to speculate that reactions to TH are due to organomercury alkyl compounds, and that positive subjects have a constitutively reduced capability to metabolize organomercury compounds, rather than to reveal previous exposure.

Alkylmercury Compounds↗
PubMed1986

Synthesis of 2,6-anhydro-S-[ethylmercury(II)]-1-thio-D-glycero-L-manno-heptitol+ ++ and bis(2,6-anhydro-1-thio-D-glycero-L-manno-heptitol)mercury(II), and the study of their interaction with beta-D-galactosidase from E. coli.

Two competitive inhibitors of beta-D-galactosidase activity, namely, 2,6-anhydro-S-[ethylmercury(II)]-1-thio-D-glycero-L-manno-heptitol (4) and bis(2,6-anhydro-1-thio-D-glycero-L-manno-heptitol)mercury(II) (6), with inhibition constants of 8.0 X 10(-4) M and 1.9 X 10(-4) M, were synthesized. Compound 6 was incorporated into the crystalline enzyme by cocrystallization. The stoichiometry of the enzyme-inhibitor complex was 1:4, corresponding to one molecule of inhibitor per active site of the enzyme. Compound 4 was found to be unstable against X-ray irradiation, whereas compound 6 was submitted to X-rays for several days without any radiation damage.

Alkylmercury Compounds↗