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PubMed1996

[Hard metal lung with diffuse small nodular shadows].

A 32-year-old woman was admitted to Niigata University Hospital with dyspnea and a non-productive cough. She had been exposed to hard metal dust for 4 years in a metal-polishing factory. Chest X-ray and CT films showed diffuse small nodular shadows in both lung fields and pulmonary-function tests revealed severe restrictive impairment. Specimens obtained by thoracoscopic lung biopsy showed fibrosis in the centers of lobules and in peribronchiolar regions. Giant-cell interstitial pneumonia-like findings were also noted. Tungsten carbide and cobalt were detected in these specimens, with an X-ray microanalyzer. Hard metal lung was diagnosed. By 1 year after she changed her place of work and began corticosteroid treatment her symptoms and pulmonary function had improved remarkably, although shadows on chest X-ray films remained to some extent.

Adult↗
PubMedDate not supplied

Metal-induced dimerization of Cd7-metallothionein. Role of anions.

Inorganic phosphate participates in the nonoxidative Cd-dependent dimerization of Cd7-metallothionein (Cd7-MT) and is bound to the MT dimers. In order to obtain insight into the specificity of phosphate-MT interaction, an investigation has been made on the effect of a series of oxyanions and organic phosphates on Cd-induced dimerization of Cd7-MT. It has been demonstrated that from the oxyanions studied, only arsenate and tungstate can promote Cd-induced dimerization of Cd7-MT. Effect of arsenate is quantitatively similar to that of phosphate and appears at submillimolar concentrations, whereas tungstate promotes dimerization of MT at higher, millimolar concentrations. A number of other oxyanions, ie, molybdate, vanadate, and selenate as well as organic phosphates (phenyl phosphate, serine O-phosphate, D-ribose 5-phosphate, L-glycerol 3-phosphate, D-fructose 6-phosphate, D-glucose 6-phosphate, adenosine monophosphate (AMP), cyclic adenosine monophosphate (cAMP), nicotinamideadenine-dinucleotide (NADP), pyridoxal 5-phosphate) had no influence on Cd-induced dimerization of MT. Results obtained strongly indicate a highly specific role of inorganic phosphate in Cd-induced dimerization of Cd7-MT.

Animals↗
PubMed1996

Investigation of the uptake of drugs by individual cells using a scanning proton microprobe (SPM).

In this paper we demonstrate the use of micro-PIXE (proton induced X-ray emission) for measuring the quantitative uptake of anti-AIDS drugs, containing metal atoms, by individual Vero cells (African green monkey kidney cell line). Hetero-polytungstates, which are assessed to present an activity against the HIV virus, were studied using Vero cells. It was found that unlike other techniques, SPM offers both the sensitivity and the spatial resolution to carry out these programs of investigations. The use of elemental analysis in single cells of cultured cell lines has shown to have distinct advantages over peripheral blood lymphocytes.

Animals↗
PubMed1996

[Mini review: a factor enhanced the antibacterial effect of beta-lactams on methicillin-resistant Staphylococcus aureus].

We found a factor (Factor T) in aged mixtures of tungstate and phosphate which greatly enhances the antibacterial effects of beta-lactams on methicillin-resistant Staphylococcus aureus (MRSA), while Factor T alone did not strongly inhibit bacterial growth. The effect on methicillin-susceptible S.aureus was weak. There was no synergism of Factor T with other classes of antibiotics, nor with other groups of bacteria. Factor T is probably a complex of phosphate and tungstate, and reduced the expression of penicillin-binding protein-2', thus sensitizing the MRSA strains to beta-lactams.

Drug Synergism↗
PubMedDate not supplied

Surface roughness of light-activated glass-ionomer cement restorative materials after finishing.

The purpose of this study was to compare the effect of various finishing sequences on the surface roughness of four new light-activated (LAGIC) restorative materials. Restorative materials included a polyacid-modified composite resin (Variglass VLC) and three resin-modified glass-ionomer cements (Vitremer, Photac-fil, and Fuji II LC). Thirty specimens of each material were prepared in Macor dies and randomly divided into six finishing sequence groups (n = 5): (1) Mylar strip (control), (2) carbide bur/Sof-Lex XT disks, (3) ET finishing diamonds, (4) carbide bur/Enhance polishing system, (5) carbide bur/Politip rubber finishers, and (6) carbide bur alone. Average surface roughness (Ra) in micrometers was measured with a Mitutoyo Surftest 401 Surface Roughness Tester and the data compared using ANOVA, Student-Newman-Keuls Multiple Comparison tests, and Dunnett's test at P < or = 0.05. Surface topography was also assessed using the scanning electron microscope (SEM) on epoxy replicas from samples of each group. The Mylar strip produced the smoothest surface and finishing sequences; (2) and (3) were significantly smoother than (4), (5), and (6). There were no significant differences between restorative materials when all finishing sequences were combined. SEM analysis was consistent with the profilometer results. Materials with higher (Ra) values appeared to have rougher surfaces. Rubber abrasives and polishing pastes seem to preferentially remove the polysalt and resin matrix of these materials.

Acrylic Resins↗
PubMed1997

[Development of a job-exposure matrix in the heavy-metal industry in France].

A job exposure matrix (JEM) was developed by a committee of experts using the DELPHI method, in the French hard metal industry, in order to assess occupational exposures to cobalt along with tungsten carbide resulting from the industrial process. This JEM is part of a nested case-control study, carried out within the historical cohort of workers ever employed in these factories, aimed at assessing lung cancer risk. The committee included 8 experts: hygienists, chemical engineers, occupational physicians and epidemiologists. The JEM was developed in four stages: (i) visit of factories, (ii) definition of lines (job-periods) and columns (exposures) of the JEM, (iii) definition of coding procedures, (iv) coding the cells of the JEM. This last stage used a method derived from the DELPHI method. Throughout the study period 1945-1994. 320 job-periods and 21 agents were defined. A quantitative assignment (level 0 to level 9) along with a frequency code (1 to 3) was attempted for 4 agents, whereas only a qualitative assignment (non exposed/exposed, i.e. 0/l) was done for the other agents. An additional probability code (1 to 3) was assigned to all agents. This procedure led to 46 columns and 14,720 cells in the JEM. When applying the DELPHI method, the consensus of the committee was obtained for 85% of all cells after the first individual assignment of experts, 88% after the second individual assignment and 100% after the third assignment by the experts all together. In order to validate the JEM, these expert assignments will be brought together with the results of exposure measurements that were performed in some workplaces of these factories. The JEM will also be linked with the data base of the case-control study for the exposure assessment of cases and controls.

Case-Control Studies↗
PubMedDate not supplied

Surface roughness and cutting efficiency of composite finishing instruments.

Trimming composite restorations includes gross removal of excess material, contouring, and finishing. Many surfaces such as the lingual surface of anterior teeth or the occlusal surfaces of posterior teeth require the use of rigid rotating instruments. The purpose of our study was to assess the suitability of eight finishing diamonds, five tungsten carbide finishing burs, and one ceramically coated finishing instrument for trimming a small-particle hybrid composite material. A total of 70 specimens of Herculite XRV were treated with the different finishing instruments under simulated practice conditions, and surface roughness was recorded quantitatively using an optical laser pick-up. The resulting surfaces were examined qualitatively with the help of scanning electron microscopy (SEM). Cutting efficiency of the diamonds and burs was evaluated at a constant pressure of 2.5 N using 42 additional specimens of Herculite XRV. Significant differences were calculated using one-way ANOVA and pairwise contrasts by Tukey's multiple range test. The results showed that finishing diamonds were characterized by high cutting efficiency and relatively rough corresponding composite surfaces, whereas tungsten carbide finishing burs led to smooth composite surfaces but had little cutting efficiency. For gross removal and contouring of composite restorations, a 15-40 microns finishing diamond is recommended followed by a tungsten carbide bur for finishing the restoration.

Aluminum Oxide↗
PubMedDate not supplied

Enamel surface morphology after bracket debonding.

The purpose of this study was to evaluate the shear bond strength of brackets and the enamel morphology after using six methods for removal of adhesive after bracket debonding. A total of thirty-five recently extracted noncarious human premolars were used. The twin bracket Mini-Taurus was used with the Mono-Lok2 TM bonding system. Shear bond strength (MPa) was calculated. Immediately after the brackets were removed, the teeth were rinsed and dried, using an air-water syringe. The adhesive remnant index was calculated and the debonded teeth with residual adhesive material attached to the enamel surface were equally sorted in seven groups of five, as follows: Group 1. The residual adhesive was removed with a 12-blade tungsten carbide finishing bur in a high-speed handpiece, using water as the coolant. Group 2. The residual adhesive was removed with a 12-blade tungsten carbide finishing bur in a low-speed handpiece, using water as the coolant. Group 3. The residual adhesive was removed with an Arkansas stone: Dura-white stones for finishing composite in a high-speed handpiece using water as the coolant. Group 4. The residual adhesive was removed with an Arkansas stone: Dura-white stones for finishing composite in a low-speed handpiece, using water as the coolant. Group 5. The residual adhesive was removed with Sof-Lex aluminum oxide discs according to manufacturer's instructions in a low-speed handpiece, using water as the coolant. Group 6. The residual adhesive was removed with Enhance Composite Finishing Discs in a low-speed handpiece, using water as the coolant. In this group, the paste was not applied after the polishing discs. Group 7. The residual adhesive was removed with Enhance Composite Finishing Discs and Polishing Cups in a low-speed handpiece, using water as the coolant. Prisma-gloss polishing paste and ultrafine polishing paste were applied according to manufacturer's instructions. After removal of the adhesive, all teeth were evaluated with the scanning electron microscope. The results revealed a mean shear bond strength of 12.75 MPa. The higher the bond strength, the higher the percentage of ARI. The smoothest enamel surface was obtained when the Enhance system with the gloss polishing paste was used; the second smoothest enamel surface was obtained when using Sof-Lex discs. If the paste was not used with the Enhance system, the obtained surface was rougher than when using Sof-Lex discs.

Adhesives↗
PubMed2003

3,6-dioxypyridazine bridged tungsten-tungsten quadruple bonds. Comparisons of electron delocalisation with oxalate bridged compounds.

The preparation and characterisation of the tungsten-tungsten quadruply bonded, 3,6-dioxypyridazine bridged complex [((t)BuCO(2))(3)W(2)](2)([micro sign]-H(2)C(4)N(2)O(2)) and its single electron oxidised radical cation are reported and, when compared with related bridged dimolybdenum complexes, reveal a different mechanism of electronic coupling from that seen in related oxalate bridged systems.

Journal Article↗
PubMed1999

Total Synthesis of Natural Bicyclic Lactones (+)-Dihydrocanadensolide, (+/-)-Avenociolide, and (+/-)-Isoavenociolide via Tungsten-pi-Allyl Complexes.

A synthetic method using tungsten-pi-allyl compounds is developed for total syntheses of natural bislactones including (+)-dihydrocanadensaolide (2), (+/-)-avenociolide (3), and (+/-)-isoavenociolide (4). Syntheses of these natural compounds are based on a common intermediate, trans-alpha-methylene butyrolactones bearing an anti-homoallylic alcohol. The kep steps in the syntheses involve an intramolecular alkoxycarbonylation of propargyltungsten complexes to yield tungsten-pi,gamma-lactonyl species, followed by condensation of their CpW(NO)I(pi-allyl) derivatives with suitable aldehydes. This new method is very efficient for the synthesis of (+/-)-avenociolide (3) and (+/-)-isoavenociolide (4). Total syntheses of compounds 3 and 4 require only six and three steps, respectively, on the basis of chloropropargyl derivatives.

Journal Article↗
PubMed2003

Tuning the redox potentials of dinuclear tungsten oxo complexes [(Cp*W(4,4'-R,R-2,2'-bpy)(mu-O))2][PF6]2 toward photochemical water splitting.

A series of novel dinuclear tungsten(IV) oxo complexes with disubstituted 4,4'-R,R-2,2'-bipyridyl (R(2)bpy) ligands of the type [(Cp*W(R(2)bpy)(mu-O))(2)][PF(6)](2) (R=NMe(2), tBu, Me, H, Cl) was prepared by hydrolysis of the tungsten(IV) trichloro complexes [Cp*W(R(2)bpy)Cl(3)]. Cyclic voltammetry measurements for the tungsten(IV) oxo compounds provided evidence for one reversible oxidation and two reversible reductions leading to the oxidation states W(V)W(IV), W(IV)W(III) and W(III)W(III). The corresponding complexes [(Cp*W(R(2)bpy)(mu-O))(2)](n+) [PF(6)](n) (n=0 for R=Me, tBu, and 1, 3 for both R=Me) could be isolated after chemical oxidation/reduction of the tungsten(IV) oxo complexes. The crystal structures of the complexes [(Cp*W(R(2)bpy)(mu-O))(2)][BPh(4)](2) (R=NMe(2), tBu) and [(Cp*W(Me(2)bpy)(mu-O))(2)](n+)[PF(6)](n) (n=0, 1, 2, 3) show a cis geometry with a puckered W(2)O(2) four-membered ring for all compounds except [(Cp*W(Me(2)bpy)(mu-O))(2)] which displays a trans geometry with a planar W(2)O(2) ring. Examining the interaction of these novel tungsten oxo complexes with protons, we were able to show that the W(IV)W(IV) complexes [(Cp*W(R(2)bpy)(mu-O))(2)][PF(6) (-)](2) (R=NMe(2), tBu) undergo reversible protonation, while the W(III)W(III) complexes [(Cp*W(R(2)bpy)(mu-O))(2)] transfer two electrons forming the W(IV)W(IV) complex and molecular hydrogen.

Journal Article↗
PubMed2000

[Syntheses, reactions and spectroscopic properties of cluster compounds containing ME4 (M = Mo, W; E = S, Se) units].

The synthetic reactions and spectroscopic studied of molybdenum (tungsten) -copper (silver, iron) -sulphur (selenium) cluster compounds, which can be prepared by the stepwise or unit construction reactions through the successive addition ML (L = Cl, Br, Sr, R2 etc) across six edges or four faces of ME4 (M = Mo, W; E = S, Se) tetrahedra, are described. A series of Mo (W)-Cu-S cluster compounds, (Et4N)2 [MCu2E4 (S2CNR2)2], (Et4N)2 [MCu2E3O (S2CNR2)2], [MCu2E4 (dppe)2] (dppe = bis (diphenylphosphine) ethane), (Et4N)2 [MCu3E4 (S2CNR2)4] (M = Mo, E = Se, R = Et (1a), R2 = C4H8 (1b), R = PhCH2 (lc)), (Et4N)2 [MCu4E4 (S2CNR2)4] (M = Mo, E = Se, R = Me (2)) (Et4N)2 [M2Cu4S8 (S2CNEt2)2], (Et4N)2 [M2Cu4S6O2- (S2CNC4H8)2], [Mo2Cu4S8 (dppm)2], [Mo2Cu4S6O2 (dppm)2], (dppm = bis (diphenylphosphine) -methane), (Et4N)4 (ME4Cu10L12) (M = Mo, E = Se, L = PhCH2S (3)), MoFe3Se4 (mu-R2NCS2)2 (R2NCS2)4 have been prepared and characterized by UV, IR and X-ray diffraction analyses.

Copper↗
PubMed2001

Reactions of halofluorocarbons with group 6 complexes M(C(5)H(5))(2)L (M = Mo, W; L = C(2)H(4), CO). Fluoroalkylation at molybdenum and tungsten, and at cyclopentadienyl or ethylene ligands.

The molybdenum(II) and tungsten(II) complexes [MCp(2)L] (Cp = eta(5)-cyclopentadienyl; L = C(2)H(4), CO) react with perfluoroalkyl iodides to give a variety of products. The Mo(II) complex [MoCp(2)(C(2)H(4))] reacts with perfluoro-n-butyl iodide or perfluorobenzyl iodide with loss of ethylene to give the first examples of fluoroalkyl complexes of Mo(IV), MoCp(2)(CF(2)CF(2)CF(2)CF(3))I (8) and MoCp(2)(CF(2)C(6)F(5))I (9), one of which (8) has been crystallographically characterized. In contrast, the CO analogue [MoCp(2)(CO)] reacts with perfluorobenzyl iodide without loss of CO to give the crystallographically characterized salt, [MoCp(2)(CF(2)C(6)F(5))(CO)](+)I(-) (10), and the W(II) ethylene precursor [WCp(2)(C(2)H(4))] reacts with perfluorobenzyl iodide without loss of ethylene to afford the salt [WCp(2)(CF(2)C(6)F(5))(C(2)H(4))](+)I(-) (11). These observations demonstrate that the metal-carbon bond is formed first. In further contrast the tungsten precursor [WCp(2)(C(2)H(4))] reacts with perfluoro-n-butyl iodide, perfluoro-iso-propyl iodide, and pentafluorophenyl iodide to give fluoroalkyl- and fluorophenyl-substituted cyclopentadienyl complexes WCp(eta(5)-C(5)H(4)R(F))(H)I (12, R(F) = CF(2)CF(2)CF(2)CF(3); 15, R(F) = CF(CF(3))(2); 16, R(F) = C(6)F(5)); the Mo analogue MoCp(eta(5)-C(5)H(4)R(F))(H)I (14, R(F) = CF(CF(3))(2)) is obtained in similar fashion. The tungsten(IV) hydrido compounds react with iodoform to afford the corresponding diiodides WCp(eta(5)-C(5)H(4)R(F))I(2) (13, R(F) = CF(2)CF(2)CF(2)CF(3); 18, R(F) = CF(CF(3))(2); 19, R(F) = C(6)F(5)), two of which (13 and 19) have been crystallographically characterized. The carbonyl precursors [MCp(2)(CO)] each react with perfluoro-iso-propyl iodide without loss of CO, to afford the exo-fluoroalkylated cyclopentadiene M(II) complexes MCp(eta(4)-C(5)H(5)R(F))(CO)I (21, M = Mo; 22, M = W); the exo-stereochemistry for the fluoroalkyl group is confirmed by an X-ray structural study of 22. The ethylene analogues [MCp(2)(C(2)H(4))] react with perfluoro-tert-butyl iodide to yield the products MCp(2)[(CH(2)CH(2)C(CF(3))(3)]I (25, M = Mo; 26, M = W) resulting from fluoroalkylation at the ethylene ligand. Attempts to provide positive evidence for fluoroalkyl radicals as intermediates in reactions of primary and benzylic substrates were unsuccessful, but trapping experiments with CH(3)OD (to give R(F)D, not R(F)H) indicate that fluoroalkyl anions are the intermediates responsible for ring and ethylene fluoroalkylation in the reactions of secondary and tertiary fluoroalkyl substrates.

Journal Article↗
PubMed1996

Human toxicity of cobalt-containing dust and experimental studies on the mechanism of interstitial lung disease (hard metal disease).

In the industry, the potential for exposure to cobalt metal dust is particularly important during the production of cobalt powder and the processing and use of hard metals and other cobalt-containing alloys. The different adverse health effects reported in these workers are reviewed. One of the main target organs is the respiratory tract, and this article concentrates on the lung parenchymal reactions induced by cobalt-containing dust. Clinical and epidemiological data indicate that this manifestation is rarely, if ever, induced by pure cobalt metal dust alone, but requires the concomitant inhalation of other compounds such as tungsten carbide in the hard metal industry (hard metal disease). Experimental studies demonstrate that cobalt metal and metallic carbides interact to produce an elective lung toxicity. Recent work on the mechanism of this interaction, which is based on the production of activated oxygen species, is reviewed. A practical implication in industrial hygiene should be that permissible exposure levels to Co dust might have to be different when exposure is to pure Co particles or an association with carbides.

Cobalt↗
PubMed2004

Electronically-coupled tungsten-tungsten quadruple bonds: comparisons of electron delocalization in 3,6-dioxypyridazine and oxalate-bridged compounds.

The preparation of the 3,6-dioxypyridazine-bridged tungsten complex, [W(2)(O(2)C(t)Bu)(3)](2)(mu-H(2)C(4)N(2)O(2)), I, is described, along with its single-electron oxidized cation, I(+), formed in the reaction between I and Ag(+)PF(6)(-). Compound I has been structurally characterized as a PPh(3) adduct, and I(+)PF(6)(-) as a THF solvate, by single-crystal X-ray studies. The geometric parameters of these compounds compare well with those calculated for the model compounds [W(2)(O(2)CH)(3)](2)(mu-H(2)C(4)N(2)O(2)) and [W(2)(O(2)CH)(3)](2)(micro-H(2)C(4)N(2)O(2))(+) by density functional theory employing the Gaussian 98 and 03 suite of programs. The calculations indicate that the two W(2) centers are strongly coupled by M(2) delta-to-bridge pi-bonding, and further coupled by direct M(2)...M(2) bonding. Compound I is purple and shows an intense absorption in the visible region due to a metal-to-bridge charge transfer and, with excitation within this absorption, compound I exhibits pronounced resonance Raman bands associated with symmetric vibrations of the bridge and the M(4) unit. The cyclic voltammogram of I in THF, the EPR spectrum of I(+)PF(6) in 2-MeTHF and the electronic absorption spectrum of I(+)PF(6)(-) in THF are consistent with electron delocalization over both W(2) units. These new data are compared with previous data for the molybdenum analogue, related oxalate-bridged compounds and closely related cyclic polyamidato-bridged Mo(4)-containing compounds. It is proposed that, while the electronic coupling occurs principally by an electron-hopping mechanism for oxalate-bridged compounds, hole-hopping contributes significantly in the cases of the amidate bridges and that this is more important for M = Mo than for M = W. Furthermore, for Class III fully delocalized mixed-valence compounds, the magnitude of K(c), determined from electrochemical methods, is not necessarily a measure of the extent of electron delocalization.

Journal Article↗