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PubMed2005

[Amalgam risk assessment with coverage of references up to 2005].

Amalgam, which has been in use in dentistry for 150 years, consists of 50 % elemental mercury and a mixture of silver, tin, copper and zinc. Minute amounts of mercury vapour are released continuously from amalgam. Amalgam contributes substantially to human mercury load. Mercury accumulates in some organs, particularly in the brain, where it can bind to protein more tightly than other heavy metals (e. g. lead, cadmium). Therefore, the elimination half time is assumed to be up to 1 - 18 years in the brain and bones. Mercury is assumed to be one of the most toxic non-radioactive elements. There are pointers to show that mercury vapour is more neurotoxic than methyl-mercury in fish. Review of recent literature suggests that mercury from dental amalgam may lead to nephrotoxicity, neurobehavioural changes, autoimmunity, oxidative stress, autism, skin and mucosa alterations or non-specific symptoms and complaints. The development of Alzheimer's disease or multiple sclerosis has also been linked to low-dose mercury exposure. There may be individual genetical or acquired susceptibilities for negative effects from dental amalgam. Mercury levels in the blood, urine or other biomarkers do not reflect the mercury load in critical organs. Some studies regarding dental amalgam reveal substantial methodical flaws. Removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials. Summing up, available data suggests that dental amalgam is an unsuitable material for medical, occupational and ecological reasons.

Adult↗
PubMed1980

Turnover of the poly(A) moiety of mRNA in wheat-germ extract.

The synthesis and degradation of poly(A) were examined in wheat germ lysates under conditions used for protein synthesis. The lysate contained both poly(A)-polymerizing and poly(A)-hydrolytic activities. The synthetic activity was dependent on the presence of either poly(A) or polyadenylated mRNA as primer. Concurrent with the synthesis of poly(A), radioactivity was released from labeled poly(A) and from the poly(A) region of mRNA. Both poly(A) synthesis and hydrolysis were independent of Mn2+ and could proceed in the presence of Mg2+, the major divalent metal ion required for protein synthesis. The synthetic activity was favoured at high (1 mM) ATP concentration, whereas the hydrolytic activity was maximal in the absence of ATP or at low (0.1 mM) ATP concentration. These data indicate that the steady-state length of the poly(A) moeity of mRNAs in the cytoplasm may be regulated by the levels of ATP. Translation products of polyadenylated mRNAs isolated from myeloma cells before and after partial deadenylation were separated by dodecylsulfate/polyacrylamide gel electrophoresis. Shortening of the poly(A) moiety did not alter the relative amounts of the peptides synthesized, indicating that this process does not involve a preferential breakdown of certain species of mRNA.

Adenosine Triphosphate↗
PubMed2000

Survey of bottled drinking water available in Manitoba, Canada.

Forty domestic and imported brands of bottled water were purchased in Manitoba, Canada and examined for total dissolved solids (TDS), chloride, sulfate, nitrate-nitrogen, cadmium, lead, copper, and radioactivity. The samples showed great variation in quality, and some exceeded the Canadian Water Quality Guidelines for drinking water for TDS, chloride, and lead. Carbonation, ozonation, and type of packaging were not associated with differences in metal levels, although carbonated samples tended to show higher TDS values. A number of deficiencies were found with respect to product labeling.

Chlorides↗
PubMed1975

[Posterior osteosynthesis in the treatment of spinal cord tumors].

Prognosis of cancerous tumors of the spine depends above all on their neurological consequences. The authors have wondered whether osteosynthesis of the spine -- in addition to decompressive surgery -- can improve patient's survival and fonctional results. 23 patients, 20 with a metastatic tumor and 3 with a plasmocytoma were treated in this way. All of them had neurological deficits, 4 had isolated radicular symptoms, 1 a cauda equina syndrome and 18 a spinal cord compression (7 of which were complete). 20 of these patients suffered intractable pain of the spine. All the patients underwent decompressive surgical removal of tumor through laminectomy, associated with a bilateral posterior metallic osteosynthesis. The type of osteosynthesis consisted of two metallic plates placed along each articular column and screwed into the articular processes and the vertebral body through the pedicles of the adjacent normal vertebrae. Cobaltotherapy was added in 14 cases, hormonotherapy in one case and radioactive 131 1 in one another patient. Selective spinal angiography, performed in one case of thoracolumbar tumor was found useful in the location and avoidance of Adamkiedwicz's artery. With regard to the complication, there were two operative wound infections requiring reoperation. Our series -- in comparaison with others -- prove the effectiveness of the combined procedure. Patients without complete spinal deficit had a 20 months survival average. Patients with complete deficit had the same survival as in comparative group. But all the 20 patients suffering pain in the spine were substantially relieved. Such a combined procedure is indicated in cases of tumors involving the vertebrae, whether or not the epidural space is invaded especially when there are riskes of unstable fracture and only partial neurological deficits. The technique may be extended even to complete paraplegia because of its worth while antalgic effects. Thus this method -- by consolidating the spine -- relieving pain and consequently allowing kinesitherapy to be resumed earlier is able to improve the functionnal status and increase survival of the patients.

Adult↗
PubMed2004

Binding of calcium ions to an avian flight muscle troponin T.

Numerous troponin T (TnT) isoforms are generated by alternative RNA splicing primarily in its N-terminal hypervariable region, but the functions of these isoforms are not completely understood. Here for the first time, we discovered that a chicken fast TnT isoform with a unique Tx motif (HEEAH)(n) binds calcium. The metal binding behavior of this TnT isoform was first investigated using terbium as a calcium analogue due to its more readily detectable fluorescence variation upon TnT binding. Both intact TnT and TnT N-terminal fragment (TnT N47) bound terbium with high affinity indicating that the N-terminal sequence was the site of binding. Since terbium often substitutes at calcium-binding sites, radioactive calcium was tested and found to bind both intact TnT and TnT N47. Fluorescence measurements using the calcium-sensitive fluorescent dye, calcium green 5N, confirmed that calcium bound to the tertiary complex of TnT and the tropomyosin dimer with a fast on-rate (10(6)-10(7) M(-1) s(-1)) as detected in stopped-flow analysis. Consistent with these observations, computational predictions suggest that TnT N47 might fold into an elongated structure with at least one high-affinity metal ion binding pocket comprised primarily of the Tx motif sequence and several lower affinity binding sites. These results suggest that TnT may play a role in modulating the calcium-mediated regulatory process of striated muscle contraction.

Amino Acid Sequence↗
PubMed2006

Management of spent sealed radioactive sources in Turkey.

Spent radioactive sources (SRS) have been generated from industrial applications, research, and medicine in Turkey. In this study, management of SRS (Co, Cs) at Cekmece Waste Processing and Storage Facility (CWPSF) is described. Eleven Cs sources (total 851 GBq) and four Co sources (total 27.75 GBq) that had been used as levels and density gauges were conditioned. Reinforced metal drums (200 L in volume) and cement matrix were used for conditioning of these sources. In this way, greater confinement was achieved for long-term storage. Maximum dose rates at the surface of the conditioned waste package were determined. In addition to information about conditioning stages of the sources, various calculations that have been done for shielding are presented. Surface dose rates of the waste packages were 1.60 mSv h for Cs and 1.63 mSv h for Co. Measurements of the final waste packages were presented to fulfill the requirements (<2 mSv h) of transportation according to regulations for the safe transport of radioactive material.

Cesium Radioisotopes↗
PubMed1992

Occupation and risk of uveal melanoma. An exploratory study.

BACKGROUND: Little is known about the cause of uveal melanoma, the most common primary intraocular malignant lesion in adults. This population-based case-control study evaluated occupational exposures. METHODS: One hundred ninety-seven newly diagnosed cases of uveal melanoma participated. Approximately two control subjects matched for age, sex, and telephone exchange area were selected for each case by random-digit dialing. Data were collected by a structured telephone interview. Two systems of occupational coding were used: an occupation-exposure linkage system and the Bureau of Census data. Conditional logistic regression for matched studies was used to examine various occupational exposures while controlling for previously reported potential confounders and for family income. The occupation-exposure matrix was used to define clusters of cases exposed to a particular chemical group from various occupations. RESULTS: Odds ratios were elevated for agriculture and farming work for both industry and occupation; this was consistent across both classification systems. Elevated odds ratios also were found for occupations involving machine operations, fabrication, assembling, equipment cleaning, and exposure to metal industries. Exposure to alkylating agents and phenols was associated with a lower risk compared with all other exposures. Several self-reported exposures also were studied. Exposures associated with elevated odds ratios were inks, insecticides, gases, radioactive substances, polybromated biphenyls, and chemical solvents. CONCLUSIONS: This exploratory study suggests various occupational associations for uveal melanoma and areas for future research.

Adolescent↗
PubMed1992

Development of solid-phase enzyme-linked immunosorbent assays for the determination of epidermal growth factor receptor and pp60c-src tyrosine protein kinase activity.

Solid-phase ELISAs for the determination of EGF receptor (EGF-R) and pp60c-src tyrosine protein kinase activity are described. The methods were developed and optimized using purified recombinant EGF-R intracellular domain (ICD) and pp60c-src tyrosine protein kinases. A standardized assay that utilizes poly (GluNa-Tyr)4:1 as substrate and a monoclonal antiphosphotyrosine antibody for detection is described. Assay conditions for both enzymes were optimized with respect to substrate and ELISA plate-coating condition, divalent metal ion preferences, enzyme concentration, apparent kinetic constants for ATP, and reaction linearity. Following standardization, a number of reference tyrosine protein kinase inhibitors were tested in the ELISAs and compared to results obtained using solution-phase radioactive tyrosine protein kinase assays, which are based on the transfer of 32P from [gamma-32P]ATP to synthetic substrate. To enable a comprehensive comparison, IC50 values obtained in the ELISA were compared with values obtained in radioactive assays using both the holo-EGF-R and EGF-R ICD kinases. No substantial qualitative differences between these assays were seen. For many routine tyrosine protein kinase assays, semiquantitative or qualitative measurement of TPK activity is adequate. For such purposes, the ELISAs would be an attractive alternative to radioactive assays.

Enzyme-Linked Immunosorbent Assay↗
PubMed1975

Control of tissue manganese: initial absence and sudden emergence of excretion in the neonatal mouse.

All adult animals and humans tested up to this time have controlled their tissue manganese concentrations by controlling primarily the rate of the metal's excretion. In sharp contrast, neonatal mice did not excrete manganese for the first 17-18 days of life, although absorption of the natural 55Mn as well as distribution, tissue accumulation, and mitochondrial accumulation of the radioactive 54Mn were vigorous. This suggested as initially avid accumulation of this essential micronutrient, supplied in scarce traces in mouse milk (54 ng/ml) by mothers consuming very much higher dietary concentrations (55,000 ng/g). The tissue accumulation was demonstrated analytically and was particularly impressive in the brain, which can be susceptible to both manganese poisoning and deficiency.

Animals↗
PubMed1999

Biosorption of actinides from dilute waste actinide solution by egg-shell membrane.

Removal of radioactive elements from the effluent and waste aqueous solutions is an important problem. In previous laboratory batch experiments, hen egg-shell membrane (ESM) was stable as an insoluble protein and was very capable of binding heavy metal ions from aqueous solution. Batch laboratory pH profile, time dependency, and capacity experiments were performed to determine the binding of uranium (U) and thorium (Th) to ESM. Batch pH profile experiments indicated that the optimum pH for binding these actinides was approx 6.0 (U) or 3.0 (Th). The adsorption isotherms were developed at pH 5.0 (U) or 3.0 (Th) at 25 degrees C, and the adsorption equilibrium data fitted both Langmuir and Freundlich models. The maximum uptakes by the Langmuir model were about 240 mg U/g and 60 mg Th/g dry weight ESM. In addition, their adsorption capacities increased as salt concentration increased. ESM could also accumulate uranium from dilute aqueous solution by adjusting to the optimum pH. These results showed that ESM was effective for removing actinides from solution and would be useful in filtration technology to remove actinides from aqueous solution.

Actinoid Series Elements↗
PubMed1988

[Fly ash and its biological effects. I. Production, utilization and physico-chemical properties of fly ash].

The paper includes the results of Part I of the studies designed to evaluate occupational risk of power engineering workers, i.e. people employed in plants producing fly-ashes, as well as those working in lightweight concrete plants where fly-ashes are applied as raw materials. The authors have found out that fly-ashes included mainly quartz, orthoclase and mullite. In dust samples, particles of fibrous structure have been found (probably--mullite). The content of free crystalline silica came to 31.6% in total dust and 8.9% in respirable dust. Fly-ashes contained:--naturally radioactive elements K40, Ra226, Th228 (maximum values were, respectively: 1070 Bq/kg, 222 Bq/kg, 142 Bq/kg of dust),--aromatic hydrocarbons (benzene-soluble fraction) in the amount of 0.001 to 0.003 microgram/mg, as well as admixtures of heavy metals in amounts varying largely. The dust concentrations at workplaces ranged from 1 mg/m3 to 200 mg/m3, depending on the type of work (inspection, repair of boilers). The results demonstrate that in the working environment of power engineering and lightweight concrete plants there occur agents of potentially fibrogenic and cancerogenic properties.

Air Pollutants, Occupational↗
PubMed1984

[Thorotrast deposits in the RES of the liver and spleen--a rare but characteristic roentgen diagnosis].

Finely reticulated or granulated shadows of liver and spleen, as well as metal-dense shadows of abdominal lymph nodes are characteristic roentgen findings in thorotrastosis. Thorium dioxide (Thorotrast) was used as a contrast medium from 1930-1950. It yielded excellent contrast and was well tolerated, but due to its radioactivity and its long biological half-life it caused manifold late complications. The typical roentgen findings in thorotrastosis are illustrated by two cases; the importance of thorotrastosis is discussed on the basis of relevant literature.

Diagnosis, Differential↗
PubMed1982

Biosynthesis in vitro of a blood group B-active fucose-containing hexaglycosylceramide from neolactopentaosylceramide in bovine spleen.

A solubilized alpha-fucosyltransferase activity has been isolated from a bovine spleen Golgi-rich membrane fraction. The enzyme transfers fucose from GDP-beta-L-fucose to a blood group B-active pentaglycosylceramide acceptor (Gal(alpha 1-3)Gal(beta 1-4)GlcNAc(beta 1-3)Gal(beta 1-4)Glc-ceramide) isolated from rabbit erythrocytes. Treatment of the membranes with 0.2% (final concentration) sodium taurodeoxycholate detergent produced maximal recovery (90%) of activity. A cationic detergent, G-3634-A, is required for optimal activity and the enzyme does not require addition of exogenous metal ion for activation. The purified 14C-labeled product of the reaction migrated with human blood group B-active hexaglycosylceramide on Silica Gel G thin layer plates. After treatment with fig alpha-galactosidase, the radioactive pentaglycosylceramide migrated with human H-active glycosphingolipid. The 14C-labeled product inhibited the hemagglutination reaction of B-type erythrocytes with Bandeiraea simplicifolia lectin and anti-B serum and formed a precipitin line with Euonymus europeus lectin. Treatment of the 14C-labeled product with alpha-fucosidase (Venus mercenaria) or weak acid at 100 degrees C for 2 h released 80-90% of the bound radioactive fucose.

ABO Blood-Group System↗
PubMed2006

Gibbs energies of transfer of alkali metal cations between mutually saturated water-solvent systems determined from extraction experiments with radiotracer 137Cs.

Thermodynamic standard Gibbs energies of transfer of alkali metal cations related to Cs+ cation [DeltatG degrees*,(Cs+)-[DeltatG degrees*,(M+)] between several mutually saturated solvents of the type water-solvent were calculated from determined extraction exchange constants Kexch degrees,*(Cs+/M+). The used liquid-liquid extraction method with radioactive tracing by 137Cs permits attaining higher precision of the values as compared to the methods used up to now. The data for o-nitrophenyloctyl ether, 1,2-dichloroethane, and 1-octanol were compared with literature sources and recommended absolute values of DeltatG degrees,*M+) are reported. For dissociating solvents, the dependences of [DeltatG degrees,*(Cs+) - [DeltatG degrees,*(M+)] on Gibbs energy of hydration of an ion, DeltaGhydr degrees are straight lines either for four cations Cs+, Rb+, K+, and Na+ (nitrosolvents) or for three cations Cs+, Rb+, and K+ (1,2-dichloroethane and 1-octanol). The hydration of Na+ and still more of Li+ in the water-saturated organic phase is apparent from the results. This manifests for high-water-content equilibrium 1-octanol even in a reversal of the values [i.e., DeltatG degrees*,(Li+) being more negative than DeltatG degrees,*(Na+)], although for Cs+, Rb+, and K+, the general trend is conserved. Water-saturated 1-octanol is thus slightly less basic than water, but the overall selectivity is very low. For one studied nondissociating solvent, dioctyl sebacate, the trend of the dependences of log Kexch degrees,*(CsB/M+) on DeltaGhydr degrees is similar to that of Kexch degrees,*(Cs+/M+) for polar solvents, but different for different anions B, thus reflecting ion association in the organic phase.

Cations↗
PubMed1992

Characterization and cellular distribution of acidic peptide and oligosaccharide metal-binding compounds from kidneys.

Two low-molecular-mass Ni-binding fractions first isolated from human kidneys [Templeton & Sarkar (1985) Biochem. J. 230, 35-42] are further characterized. Both components are acidic and are readily separated from each other by gel chromatography on Bio-Gel P-2. After equilibration with 63Ni the largest complex constitutes about 30% of the radioactive 63Ni and is an approx. 3.5 kDa peptide and the smallest species comprise short oligosaccharides containing 70% of the radioactivity. Both of these components are found in human, bovine and porcine kidneys as well as in a porcine proximal tubule-like cell line LLC-PK1. There is a small variation in amino acid composition between species. The oligosaccharides are reducing sugars and contain sulphate, glucosamine, glucuronic acid and iduronic acid with two to four overall negative charges. The monosaccharide composition was determined by h.p.l.c. with pulsed amperometric detection of the acid hydrolysates and by gas chromatography. In the LLC-PK1 cell line the acidic peptide is both intracellular and extracellular, whereas the oligosaccharides are only intracellular. The concentration of extracellular peptide, as measured by 63Ni binding, is found to increase after exposure of the cells to low micromolar concentrations of Ni, whereas the oligosaccharide concentrations, also measured by 63Ni binding, remain constant. The oligosaccharide component is decreased by 40% in the presence of NH4Cl, suggesting that is derived from degradation of internalized heparan sulphate.

Aged↗
PubMed2001

Accumulation of metal-binding peptides in fission yeast requires hmt2+.

The fission yeast Schizosaccharomyces pombe detoxifies cadmium by synthesizing phytochelatins, peptides of the structure (gamma-GluCys)nGly, which bind cadmium and mediate its sequestration into the vacuole. The fission yeast protein HMT2, a mitochondrial enzyme that can oxidize sulphide, appears to be essential for tolerance to multiple forms of stress, including exposure to cadmium. We found that the hmt2- mutant is unable to accumulate normal levels of phytochelatins in response to cadmium, although the cells possess a phytochelatin synthase that is active in vitro. Radioactive pulse-chase experiments demonstrated that the defect lies in two steps: the synthesis of phytochelations and the upregulation of glutathione production. Phytochelatins, once formed, are stable. hmt2- cells accumulate high levels of sulphide and, when exposed to cadmium, display bright fluorescent bodies consistent with cadmium sulphide. We propose that the precipitation of free cadmium blocks phytochelatin synthesis in vivo, by preventing upregulation of glutathione production and formation of the cadmium-glutathione thiolate required as a substrate by phytochelatin synthase. Thus, although sulphide is required for phytochelatin-mediated metal tolerance, aberrantly high sulphide levels can inhibit this pathway. Precise regulation of sulphur metabolism, mediated in part by HMT2, is essential for metal tolerance in fission yeast.

Aminoacyltransferases↗