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PubMed1986

Modulation of activity of human alkaline phosphatases by Mg2+ and thiol compounds.

Interaction of purified human liver and placental alkaline phosphatases (orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1) with sulfhydryl groups, sulfhydryl reagents, and Mg2+ were studied. L-Cysteine (0.1 mmol/l) or Mg2+ activated the liver enzyme 4-5-fold and the placental enzyme 2-3-fold, with optimal pH 7.5-8.0; these activations were not additive. L-Cysteine (2 mmol/l) inhibited both enzymes maximally at pH greater than 9.0; phosphate protected the enzymes. S-Methylcysteine had little effect, with or without Mg2+. Inhibition by sulfur-containing compounds paralleled their ability to bind Zn2+. Fluoresceine mercury acetate (specific for sulfhydryl groups) inhibited the isoenzymes, whereas iodoacetic acid, iodoacetamide, dithionitrobenzoic acid, and p-chloromercuribenzoate had little effect. The inhibition was reversed by L-cysteine and only slightly protected by inorganic phosphate. Thus, there are two sites on human liver and placental alkaline phosphatase that interact with L-cysteine; a Mg2+-binding site, which results in activation, and a site that involves one or both of the bound Zn2+ ions and results in inactivation. Both enzymes have a protected essential thiol group.

Alkaline Phosphatase↗

PubMed1985

Reactive thiol groups in rat liver acid phosphatase.

Dimeric rat liver acid phosphatase P1 of Mr 92,000 is inactivated by p-chloromercuribenzoate and fluorescein mercuriacetate (FMA). The enzyme is protected against the mercurials by the substrate analogue Pi. The reaction with FMA is accompanied by changes in absorbance at 495 nm and in fluorescence emission at 520 nm that are characteristic of reaction of this compound with thiol groups. Titration of P1 with FMA monitored by spectrophotometry or by fluorimetry indicated that equivalence is reached at an FMA/P1 ratio of 3. Since FMA can act as a bifunctional reagent, it is likely that P1 contains either 3 or 6 reactive thiol groups per molecule. Analysis of FMA inactivation/modification data by a statistical method suggests that of 6 reactive thiol groups, 2 are essential so that there are probably 3 thiol groups per subunit, one of which is located at the active site. If the total thiol number is 3, analysis suggests 1 essential thiol per subunit.

Acid Phosphatase↗

PubMed2004

Mode of action of 2-furylmercury chloride, an anti-rhinovirus compound.

2-Furylmercury chloride (2-FMC), an organic mercury derivative, has been found to inhibit the replication of all tested human rhinovirus (HRV) serotypes belonging to the antiviral group B and a limited number of HRV serotypes belonging to the antiviral group A. The mechanism of action of 2-FMC was tested against HRV-2 (antiviral group B, minor receptor group), and compared with an antiviral compound for which the viral target was already determined (enviroxime). 2-FMC was found to bind reversibly to virus particles. However, time-dependent plaque reduction assays revealed that 2-FMC did not interfere with early events of HRV-2 replication. Using a quantitative RT-PCR ELISA assay, we were able to prove that 2-FMC inhibits the synthesis of viral RNA. However, the mode of action of 2-FMC is not identical to that of enviroxime, another inhibitor of viral RNA synthesis. Time-of-addition and time-of-withdrawal experiments demonstrated that 2-FMC acted during a broader time interval than enviroxime.

Antiviral Agents↗

PubMed1985

Hybromet: a ligand for purifying opioid receptors.

Condensation of the Grignard reagent derive from 2-[4-(allyloxy)phenyl]ethyl bromide (4b) with 7 alpha-acetyl-6,14-endo-ethenotetrahydrothebaine (5) furnished the (R) tertiary carbinol, 7, which upon methoxymercuration followed by treatment with the KBr gave the bromomercurio compound 10 (Hybromet). The corresponding N-cyclopropylmethyl analogue, 11, was prepared also. The bromomercurio compound, 1, and the mercaptobenzothiazole derivative, 3, gave allyl phenyl ether when treated with BAL at room temperature. Similar treatment of 10 with BAL gave 7 in high yield. Binding studies using rat brain homogenates indicated that 7, 13, and 14 have moderately high affinities for mu rather than delta binding sites. Although much weaker, 10 showed preferential mu binding also. These results along with the fact that 10 reacted smoothly with sulfhydryl groups suggest that Hybromet would be a suitable ligand for use in affinity chromatography.

Animals↗

PubMed1978

Neurological syndromes produced by some toxic metals encountered industrially or environmentally.

Toxic metals encountered industrially or environmentally may produce the following syndromes: 1) Peripheral neuropathy: which is mainly sensory in arsenic and entirely motor with inorganic lead, organophosphorus compounds and tallium produce a mixed form of peripheral neuropathy. 2) Encephalopathy: usually with lead poisoning where ataxia and hemiplegia or optic atrophy may occur. 3) Optic neuritis: transient or permanent impairment of vision in arsenic poisoning and blurring of vision followed by field fedects with thallium poisoning. 4) Cerebellar disturbances: in the form of ataxia in organic mercury. 5) Parkinsonism: extrapyramidal signs occurs in manganese poisoning shown as mask face and rigidity of muscles. 6) Mental changes: as acute psychosis in organic lead and erethism in organic mercury.

Adult↗

PubMed1986

Characteristics of Hg-resistant bacteria isolated from Minamata Bay sediment.

Seventy-two strains of Hg-resistant bacteria (Pseudomonas) were isolated on agar plates containing 40 micrograms/ml of HgCl2 from Minamata Bay sediment, which was heavily polluted with mercury (45.8 micrograms/g). The minimal inhibitory concentrations (MICs) of mercurial compounds were determined for the Hg-resistant pseudomonads and 65 strains (Pseudomonas sp., Bacillus sp., Vibrio sp., and Corynebacterium sp.) isolated from Sendai Bay sediment (1 microgram/g of mercury) as control. The MICs to HgCl2, CH3HgCl, C2H5HgCl, C3H7HgCl, and C6H5HgOCOCH3 for the Hg-resistant pseudomonads from Minamata Bay were significantly higher than those of strains from Sendai Bay. The volatilization from liquid culture containing 20 micrograms/ml of HgCl2 was observed in all of the Hg-resistant pseudomonads from Minamata Bay (70 strains). The mean loss of mercury from liquid culture was 60.4 +/- 17.3%. Further study is warranted to determine what role the Hg-resistant bacteria, particularly the Pseudomonas species, play in the mercury cycle in Minamata Bay.

Bacteria↗

PubMed1978

The reactions of mercurated pyrimidine nucleotides with thiols and with hydrogen sulfide.

In the presence of thiols, 5-mercuripyrimidine nucleotides are quantitatively converted to 5-thiomercuri derivatives, but these compounds are unstable and decompose at a rate dependent on the nature of the thiol. The decomposition involves three different reactions and proceeds via a symmetrical mercury derivative of the nucleotide. The end product is the unmodified nucleotide. Similar reactions occur in the presence of hydrogen sulfide. Since mercurated nucleoside triphosphates are substrates for RNA- and DNA polymerase only in the form of thiomercuri derivatives, this implies that when DNA is replicated or transcribed in vitro with a mercurated substrate, the latter is rapidly demercurated to the unmodified substrate which is incorporated as well. Hence the product of the in vitro synthesis can only be partially mercurated in any one pyrimidine. Also, formation of cross-links in the resulting polymer is possible.

Chemical Phenomena↗

PubMed1977

Changes in activity of malate dehydrogenase and glucosephosphate isomerase in serum of rats exposed chronically to inorganic mercury and its aryl and alkyl compounds.

In course of prolonged exposure [14 weeks] to various mercury compounds [MetHg - a fluid seed-dressing preparation 0,8. Phenyl and Ethyl chlorides and HgC1(2) in doses corresponding to 5% of DL(50)[3 times weekly], enhanced levels of activity of malate dehydrogenase [MDH] and glucosephosphate isomerase [PHI] in blood serum were observed. After 7 weeks of exposure about fourfold increase of MDH and 2-3-fold enhancement of PHI activities were found relative to controls. After 14 weeks of exposure in livers of rats, given MetHg and EtHg, organic mercury was found at concentrations of 28.8 and 4 microng/g tissue, respectively. Inorganic mercury in liver was found in animals given all coumpounds and concentrations were in the range of 1,2 - 4,7 microng/g tissue.

Animals↗

PubMed1992

Latent collagenase and gelatinase from human neutrophils and their activation.

Procollagenase M(r) 85,000 (SDS-PAGE) was purified from buffy coat to homogeneity and represents a stable single polypeptide chain forming the entire proenzyme. The procollagenase can be activated by various proteinases, e.g. trypsin, chymotrypsin, cathepsin G, kallikrein and stromelysin and by different mercurial compounds. Proteolytic conversion of the latent enzyme to the active form by chymotrypsin is accompanied by a molecular weight reduction to an apparent M(r) 64,000. This active enzyme lacks the first 79 N-terminal residues. Activation by trypsin leads to a latent intermediate of apparent M(r) 70,000, lacking 48 N-terminal residues. The active enzyme is therefore generated upon prolonged incubation with trypsin by further cleavage of 22 N-terminal residues. Another latent intermediate form with apparent M(r) 69,000 is generated from the proenzyme upon incubation with leukocyte elastase by N-terminal cleavage of 53 or 64 residues, respectively. However, latent collagenase cannot be activated by plasmin. Activation by different mercurial compounds finally results in the formation of active collagenase with apparent M(r) 64,000. In contrast to the proenzyme, active collagenase can autolyse to give active M(r) 57,000 and 45,000 intermediates and two M(r) 28,000 fragments. Purification of latent leukocyte gelatinase yields three final products with apparent M(r) 98,000, 125,000 and 220,000 (SDS-PAGE; non reduced). Upon reduction, only the M(r) 98,000 form can be detected. The latent gelatinase can be activated in a similar manner as collagenase. Proteolytic activation by trypsin leads after N-terminal cleavage to an active gelatinase with sequence homology to leukocyte collagenase.

Amino Acid Sequence↗

PubMed1979

Chemical induction of nondisjunction in drosophila.

Tests for chemically induced nondisjunction and loss of the sex chromosomes in Drosophila were performed. Of 31 compounds tested four gave rise only to an increase of XO exceptions, indicating the induction of chromosome loss. Six compounds, all known spindle inhibitors (colchicine, organic mercury, lead, and tin compounds) gave rise to an increase both of XXY and XO or of only XXY. The effect by metalloorganic compounds of which methylmercury was studied particularly closely, follows a peculiar pattern. In females with structurally normal X chromosomes only an increase of XX gametes is obtained, while with X chromosomes heterozygous for long inversions only O gametes are increased. The data indicates that the effect of the metal compounds occurs at first meiosis and that the process is connected with a meiotic drive, giving rise to a preferential segregation of the two X chromosomes to the functioning pole. The increase only of O gametes with structurally heterozygous X chromosomes can tentatively be explained by a loss due to crossing over within the inversion. An increase of the effect of methyl mercury was obtained where the normal pairing of the X chromosomes was interfered with by means of autosomal inversions. Likewise a synergistic increase of nondisjunction was obtained when a temperature chock of 10 degrees C was applied together with treatment with methylmercury. It is concluded that chemical induction of nondisjunction can be studied in Drosophila, but the sensitivity of the test is rather low and large amount of material is required.

Animals↗

PubMed1985

Relation between red cell anion exchange and urea transport.

The new distilbene compound, DCMBT (4,4'-dichloromercuric-2,2,2',2'-bistilbene tetrasulfonic acid) synthesized by Yoon et al. (Biochim. Biophys. Acta 778 (1984) 385-389) was used to study the relation between urea transport and anion exchange in human red cells. DCMBT, which combines properties of both the specific stilbene anion exchange inhibitor, DIDS, and the water and urea transport inhibitor, pCMBS, had previously been shown to inhibit anion transport almost completely and water transport partially. We now report that DCMBT also inhibits urea transport almost completely and that covalent DIDS treatment reverses the inhibition. These observations provide support for the view that a single protein or protein complex modulates the transport of water and urea and the exchange of anions through a common channel.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1987

Mercurated nucleic acid probes, a new principle for non-radioactive in situ hybridization.

This report describes the localization of specific nucleic acid sequences in interphase nuclei and metaphase chromosomes by a new hybridocytochemical method based on the use of mercurated nucleic acid probes. After the hybridization a sulfhydryl-hapten compound is reacted with the hybrids formed. A number of such ligands were synthesized and tested. A fluorescyl ligand could be used for the direct visualization of highly repetitive sequences. For indirect immunocytochemical visualization trinitrophenyl ligands were found to be more sensitive than biotinyl analogues. These ligands were applied for the detection of target sequences in metaphase chromosomes and interphase nuclei of somatic cell hybrids, human lymphoid cell lines and blood cell cultures. The sequences were in the range of high to low copy numbers. The lower limit of sensitivity is indicated by the visualization of two human unique DNA fragments (40 and 15.6 kb) in human metaphases. The method is rapid, gives consistent results and can be used for both RNA and DNA probes. Other potentials of the new principle are discussed.

Animals↗

PubMed2005

Organic mercury compounds and autoimmunity.

Based on in vitro studies and short-term in vivo studies, all mercurials were for a long time considered as prototypic immunosuppressive substances. Recent studies have confirmed that organic mercurials such as methyl mercury (MeHg) and ethyl mercury (EtHg) are much more potent immunosuppressors than inorganic mercury (Hg). However, Hg interacts with the immune system in the presence of a susceptible genotype to cause immunostimulation, antinucleolar antibodies targeting fibrillarin, and systemic immune-complex (IC) deposits, a syndrome called Hg-induced autoimmunity (HgIA). Recent studies in mice with a susceptible genotype has revealed that the immunosuppressive effect of MeHg and EtHg will within 1-3 weeks be superseded by immunostimulation causing an HgIA-like syndrome. At equimolar doses of Hg, MeHg has the weakest immunostimulating, autoimmunogen, and IC-inducing effect, while the effect of thimerosal is similar to that of inorganic mercury. The immunosuppression is caused by the organic mercurials per se. Since they undergo rapid transformation to inorganic Hg, studies are being undertaken to delineate the importance of the organic substances per se and the newly formed inorganic Hg for induction of autoimmunity.

Animals↗

PubMed1977

[Encephalopathy due to organomercuric compounds].

A 27 year old agricultural worker presented about one month after treating cereal seeds with an alcoxyalkyl mercurial derivative, an encephalopathy with a confusional state, a cerebellar stato-kinetic syndrome, an intention tremor and grand mal epileptic fits. Treatment with dimercaprol produced a clinical improvement on the fourth day with a fall in blood mercury from 3.5 mug to 2.2 mug whilst urinary excretion of mercury remained low. A fortnight later the patient was completely cured. Although less common than collective poisoning by ingestion, organo-mercurial encephalopathies due to occupational exposure are a real danger although it is not known whether the relative rareness of published cases is due only to lack of observance of security rules or to individual sensitivity which might be due to increased absorption of mercury through the lungs or skin. This case shows that although alkyl mercurial derivatives are reputed to be the most dangerous, alcoxyalkyl derivatives may also cause encephalopathies. Also, as long as non-toxic substances remain unavailable for use in agriculture, one should emphasise the necessity of careful observance of the security rules during manipulation of these products.

Adult↗

PubMed2001

Aquabromo(6-carboxypyridine-2-carboxylato-O,N,O')mercury(II).

The title compound, [HgBr(C7H4NO4)(H2O)], was obtained by the reaction of an aqueous solution of mercury(II) bromide and pyridine-2,6-dicarboxylic acid (picolinic acid, dipicH(2)). The shortest bond distances to Hg are Hg-Br 2.412 (1) A and Hg-N 2.208 (5) A; the corresponding N-Hg-Br angle of 169.6 (1) degrees corresponds to a slightly distorted linear coordination. There are also four longer Hg-O interactions, three from dipicH(-) [2.425 (4) and 2.599 (4) A within the asymmetric unit, and 2.837 (4) A from a symmetry-related molecule] and one from the bonded water molecule [2.634 (4) A]. The effective coordination of Hg can thus be described as 2+4. The molecules are connected to form double-layer chains parallel to the y axis by strong O-H.O hydrogen bonds between carboxylic acid groups of neighbouring molecules, and by weaker hydrogen bonds involving both H atoms of the water molecule and the O atoms of the carboxylic acid groups.

Crystallography, X-Ray↗

PubMed2006

Evidence of two-dimensional superconductivity in the single crystalline nanohybrid of organic-bismuth cuprate.

A coordination compound of HgI(2)(pyridine)(2) can be successfully intercalated into a single crystalline Bi(2)Sr(2)CaCu(2)O(y) high-T(c) superconductor through an interlayer complexation reaction between pyridine molecules and bismuth cuprate pre-intercalated with mercuric iodide. X-ray diffraction and X-ray absorption spectroscopic results clearly demonstrate that the single crystalline nature of the pristine bismuth cuprate remains unchanged even after the intercalation of organic complex as well as those of iodine and mercuric iodide. According to the angle-dependent dc magnetization measurements, the intercalation of bulky organic molecules completely blocks superconductive currents along the c-axis, whereas a superconducting transition along the in-plane direction still occurs in the organic intercalate. In the case of the iodine or mercuric iodide intercalates with smaller lattice expansions, an out-of-plane diamagnetic transition is not wholly quenched but significantly depressed by the intercalation, confirming the reduction of interlayer interaction. The present finding can provide straightforward evidence of the two-dimensionality of high temperature superconductivity in the present cuprate-based nanohybrid material.

Bismuth↗

PubMed1986

Effects of mercury (II) compounds on the activity of dUTPases from various sources.

The deoxyuridine triphosphate nucleotidohydrolases (dUTPases, EC 3.6.1.23) from Escherichia coli K-12-,Acholeplasma laidlawii B-PG9-, human KB cell-, and the herpes simplex virus (HSV) type 1- and 2-induced dUTPases were purified and used to determine the effect of various mercury (II) compounds on their activities. Mercuric acetate, 5-mercuri-dUTP (HgdUTP), and 5-mercuri-dCTP (HgdCTP) acted as irreversible active site-directed inhibitors of the dUTPases purified from eukaryotic organisms but not those from prokaryotic organisms. The inhibition constants (Ki) were estimated for the KB, HSV-1, and HSV-2 dUTPases to be 8 +/- 2, 12 +/- 3, and 9 +/- 2 microM for mercuric acetate, 204 +/- 25, 121 +/- 15, and 111 +/- 10 microM for HgdUTP, and 775 +/- 25 and 651 +/- 23 microM for HgdCTP, respectively. The conversion of HgdUTP to its mercurithio-derivative resulted in a decrease in the affinity of the derivative for the eukaryotic dUTPases. The 5-mercurithioethylene glycol derivative of dUTP did not act as a substrate for the KB dUTPase but it did act as a substrate for the HSV-1- and HSV-2-induced dUTPases with Ki values of 526 +/- 47 and 483 +/- 32 microM, respectively. These results demonstrate that the eukaryotic dUTPases can be distinguished based upon differences in their affinities for the mercurithio-derivatives of dUTP and suggest that there are differences in the steric binding properties of the nucleotide-binding site of these enzymes.

Acholeplasma laidlawii↗

PubMed1992

A new mercury-penicillin V derivative as a probe for ultrastructural localization of penicillin-binding proteins in Escherichia coli.

The precise ultrastructural localization of penicillin-binding protein (PBP)-antibiotic complexes in Escherichia coli JM101, JM101 (pBS96), and JM101(pPH116) was investigated by high-resolution electron microscopy. We used mercury-penicillin V (Hg-pen V) as a heavy-metal-labeled, electron-dense probe for accurately localizing PBPs in situ in single bacterial cells grown to exponential growth phase. Biochemical data derived from susceptibility tests and bacteriolysis experiments revealed no significant differences between Hg-pen V and the parent compound, penicillin V, or between strains. Both antibiotics revealed differences in the binding affinities for PBPs of all strains. Deacylation rates for PBPs were slow despite the relatively low binding affinities of antibiotics. Cells bound most of the Hg-pen V added to cultures, and the antibiotic-PBP complex could readily be seen by electron microscopy of unstained whole mounts as distinct, randomly situated electron-dense particles. Fifty to 60% of the antibiotic was retained by cells during processing for conventional embedding so that thin sections could also be examined. These revealed similar electron-dense particles located predominantly on the plasma membrane and less frequently in the cytoplasm. Particles positioned on the plasma membranes were occasionally shown to protrude into the periplasmic space, thereby reflecting the high resolution of the Hg-pen V probe. Moreover, some particles were observed free in the periplasm, suggesting, for the first time, that a proportion of PBPs may not be restricted to the plasma membrane but may be tightly associated with the peptidoglycan for higher efficiency of peptidoglycan assembly. All controls were devoid of the electron-dense particles. The presence of electron-dense particles in cells of the wild-type JM101, demonstrated that our probe could identify PBPs in naturally occurring strains without inducing PBP overproduction.

Anti-Bacterial Agents↗