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PubMed2001

High frequency properties of passive materials for ultrasonic transducers.

The acoustic properties of passive materials for ultrasonic transducers have been measured at room temperature in the frequency range from 25 to 65 MHz using ultrasonic spectroscopy. These materials include alumina/EPO-TEK 301 composites and tungsten/EPO-TEK 301 composites. Experimental results showed that the acoustic impedance of the composites monotonically increased with the volume fraction of the particle filler, which is in agreement with the Denavey model. The attenuation, however, peaked between 7 and 9% volume fraction of particle filler. For comparison, several other passive materials were also fabricated and measured. The results suggest that materials that possess a higher attenuation also appear to have a larger velocity dispersion.

Aluminum Oxide↗
PubMed2006

Triple-bond reactivity of diphosphorus molecules.

We report a mild method for generating the diphosphorus molecule or its synthetic equivalent in homogeneous solution; the P2 allotrope of the element phosphorus is normally obtained only under extreme conditions (for example, from P4 at 1100 kelvin). Diphosphorus is extruded from a niobium complex designed for this purpose and can be trapped efficiently by two equivalents of an organic diene to produce an organodiphosphorus compound. Diphosphorus stabilized by coordination to tungsten pentacarbonyl can be generated similarly at 25 degrees C, and in this stabilized form it still efficiently consumes two organic diene molecules for every diphosphorus unit.

Journal Article↗
PubMed1992

Particle clearance from the canine pleural space into thoracic lymph nodes: an experimental study.

We instilled tungsten powder (CaWO4) into the pleural space of the dog and studied the kinetics and distribution of particle translocation from the pleural space to the thoracic lymph nodes over 1-7 days. We found that the transport of tungsten particles to regional lymph nodes was present at day 1, and reached its peak at day 3. In situ detection of tungsten by elemental particle analysis of lymph node sections by scanning electron microscopy complemented by light microscopy and X-ray analysis allowed precise mapping of the marker in the thoracic nodes. The first lymph nodes to become tungsten-laden was the parasternal group (day 1-3). From day 3 to 7 tungsten inclusions decreased in these parasternal nodes while moderately increasing in the remaining intrathoracic lymph nodes. Retrocardiac pleural folds containing numerous "milky spots" also accumulated prominent amounts of tungsten early after intrapleural injection of CaWO4. These data indicate that 1) particle translocation from the pleural space to regional lymph nodes is a rapid process and is first directed to the parasternal lymph nodal subgroup; 2) particle dissemination to virtually all other lymph nodes within the thorax follows thereafter; 3) retrocardiac pleural folds contribute to the clearance of particles from the pleural space.

Animals↗
PubMed1991

Inflammatory macrophages in the dog contain high amounts of intravesicular ferritin and are associated with pouches of connective tissue fibers.

We have studied the subcellular distribution of ferritin in inflammatory macrophages present in regional lymph nodes from dogs subjected to a pulmonary inflammatory reaction. The inflammatory reaction was induced by intrabronchial instillation of calcium tungstate (CaWO4), a water-insoluble powder. Ferritin was identified by electron microscopy, and its electron density was enhanced by the use of a modified Perls method. From day 14 on after the CaWO4 deposition, tungsten-positive lymph node macrophages showed a massive accumulation of ferritin. Most of the ferritin was stored in membrane-bounded vesicles that showed heterogeneous concentrations of the protein. A significant complement of ferritin was also detected in the cytoplasmic ground substance of phagocytes. The cell surface of the ferritin-rich, tungsten-positive macrophages showed deep infoldings that encompassed small pockets of connective tissue fibers. These features were not observed in control samples or in lymph nodes from dogs subjected to CaWO4-induced inflammation for periods shorter than 1 week. Our data indicate that inflammatory macrophages greatly increase their content of ferritin macrophages greatly increased their content of ferritin and that ferritin is stored predominantly by a membrane-bounded vesicular compartment. This is in contrast with suggestions that the inflammation-induced increase in macrophage iron is restricted to the labile pool of iron and it does not involve the iron bound to ferritin molecules. Our observation of nodules of connective-tissue fibers in intimate topographical association with ferritin-rich macrophages may indicate that the increase in intracellular ferritin in the macrophage is in some way related to the secretion of factors by the phagocyte that will stimulate fibrillogenesis by neighboring fibroblats.

Animals↗
PubMed2005

Laser-driven hard-x-ray generation based on ultrafast selected energy X-ray absorption spectroscopy measurements of Ni compounds.

Three Ni compounds were studied by ultrafast selected energy x-ray absorption spectroscopy using a laser-driven electron x-ray source with a tungsten target. The measured K edges of these Ni compounds using this self-referencing method were made identical to those measured with synchrotron x-ray sources. This enabled us to determine the absolute peak positions of tungsten Lalpha(1) and Lalpha(2) emitted from this source to be within 1 eV of those from the neutral tungsten atoms, which strongly suggested that the x rays were emitted from high energy electrons interacting with tungsten atoms in the solid target. This is the best evidence to date that directly supports the cold atom x-ray generation theory.

Journal Article↗
PubMed1999

Lung fibrosis induced by silica particles in NMRI mice is associated with an upregulation of the p40 subunit of interleukin-12 and Th-2 manifestations.

Interleukin (IL)-12 is a cytokine produced principally by activated macrophages which is involved in control of the T-helper 1/T-helper 2 cell (Th1/Th2) polarization of immune responses. To examine its potential involvement in the development of lung fibrosis, we examined the expression (protein, messenger RNA [mRNA]) of IL-12 (p70) and of its subunits (p40 and p35) in lung homogenates, bronchoalveolar lavage fluid (BALF), and bronchoalveolar lavage (BAL) cell cultures in mouse models of resolutive alveolitis (RA) and fibrosing alveolitis (FA) induced by inorganic particles (manganese dioxide [MnO2] and crystalline silica, respectively). The administration of tungsten carbide (WC), which behaved as an innocuous dust for the lung, served as a negative control condition. The FA was specifically accompanied by a Th2-like polarization characterized by high levels of immunoglobulin (Ig)G1 in BALF and by a protracted overproduction of both p40 protein and mRNA, but not by the biologically active form of IL-12 (p70). In the RA model, the p40 response was only transient, and a Th1-like response was reflected by increased levels of interferon (IFN)-gamma and dominant levels of IgG2a in BALF. Taken together, these findings suggest that production of the p40 subunit of IL-12 and Th2 polarization play important roles in lung inflammatory and fibrotic responses to inhaled inorganic particles.

Animals↗
PubMed1990

Time course and distribution of tungsten-laden macrophages in the hilar lymph nodes of the dog lung after experimental instillation of calcium tungstate into the left apical bronchus.

We sprayed a tungsten powder (CaWO4) into the airway of a single lobe (left apical) of the dog lung in order to study: (a) the kinetics of particle translocation from the bronchoalveolar lining to hilar lymph nodes, and (b) the sorting in lung lymph nodes of inhaled microcrystals. We found that the transport of the tungsten particles to the regional lymph node takes at least 24 hours and reaches its peak at day 7. In situ detection of tungsten by elemental particle analysis of lymph node sections by scanning electron microscopy allowed precise mapping of the marker in the node; the method was complemented by light microscopy and thin-section electron microscopy of the same nodes. Virtually all of the lymph node tungsten was located inside macrophages. The first tungsten-positive macrophages seen in the regional lymph nodes (day 1 to day 3) were restricted to the subcapsular space. This was followed by massive filling of the same sinus and of the narrow interfollicular areas by the particle-laden macrophages (day 3 to day 7). The even distribution of the tungsten-bearing phagocytes found in these anatomical regions of the node indicated that the subcapsular area in the dog was a continuous domain rather than the segmented region observed in nodes of common laboratory animals such as the rat. By day 7 after tungsten instillation, a moderate number of tungsten-positive macrophages was also detected in the paracortical region of the node. Finally, the presence of tungsten-bearing macrophages was extended to the outer lymph node medulla (day 7 to day 14); here, the macrophages were located in association with cords of plasmacytes and showed interdigitations with these lymphocytes. Only minimal amounts of tungsten were detected inside lymphoid follicles in association with dendritic cells. Some of the tungsten initially deposited in the airway of the apical left lung lobe was detected in contralateral hilar lymph nodes. We conclude that: (i) particle translocation from the alveolus to regional lymph nodes is a slow process that is mediated by pulmonary macrophages, in agreement with the findings of Harmsen et al Science 230:1277, 1985); (ii) in the lymph node, particle-bearing macrophages are sorted through narrow interfollicular sinuses into the outer medulla where they interact extensively with plasma cells; (iii) the migrating macrophages cannot penetrate the follicular domains of the node; minute quantities of exogenous particles may, nevertheless, be transferred from macrophages to follicular dendritic cells; and (iv) contralateral drainage may be a feature of the lymphatic system in the lung.

Animals↗
PubMed2004

Activated carbon and tungsten oxide supported on activated carbon catalysts for toluene catalytic combustion.

We have used activated carbon (AC) prepared from almond shells as a support for tungsten oxide to develop a series of WOx/AC catalysts for the catalytic combustion of toluene. We conducted the reaction between 300 and 350 degrees C, using a flow of 500 ppm of toluene in air and space velocity (GHSV) in the range 4000-7000 h(-1). Results show that AC used as a support is an appropriate material for removing toluene from dilute streams. By decreasing the GHSV and increasing the reaction temperature AC becomes a specific catalyst for the total toluene oxidation (SCO2 = 100%), but in less favorable conditions CO appears as reaction product and toluene-derivative compounds are retained inside the pores. WOx/AC catalysts are more selective to CO2 than AC due to the strong acidity of this oxide; this behavior improves with increased metal loading and reaction temperature and contact time. The catalytic performance depends on the nonstoichiometric tungsten oxide obtained during the pretreatment. In comparison with other supports the WOx/AC catalysts present, at low reaction temperatures, higher activity and selectivity than WO, supported on SiO2, TiO2, Al2O3, or Y zeolite. This is due to the hydrophobic character of the AC surface which prevents the adsorption of water produced from toluene combustion thus avoiding the deactivation of the active centers. However, the use of WOx/AC system is always restricted by its gasification temperature (around 400 degrees C), which limits the ability to increase the conversion values by increasing reaction temperatures.

Air Pollution↗
PubMed1996

Alveolar macrophages accumulate iron and ferritin after in vivo exposure to iron or tungsten dusts.

Extracellular iron present in alveolar structures may contribute to oxidative lung injury induced by toxic mineral dusts by enhancing dust-induced generation of hydroxyl radicals. Alveolar macrophages (AMs) can sequester iron within ferritin and limit generation of hydroxyl radicals. In the current study we sought to assess whether AMs accumulate iron and ferritin after in vivo exposure to a dust with high iron content, to iron oxide, or to an inflammatory dust, calcium tungstate. We performed lung lavage 1, 7, 14, 28, 42, and 56 days after intratracheal instillation of mineral dust in saline solution or instillation of saline solution alone and quantitated cell recovery and AM content of iron and ferritin. Instillation of iron oxide increased neutrophil recovery only on a day 1 when compared with results in controls, whereas calcium tungstate increased neutrophil recovery through day 14. AMs recovered after instillation of iron oxide contained increased amounts of iron and ferritin, beginning on day 1 and progressing through day 56 after treatment (7.57 +/- 0.38 microgram iron per 10(6) AMs vs 1.54 +/- 0.28 microgram iron per 10(6) AMs for controls, p < 0.001; and 5908 +/- 768 ng ferritin per 10(6) AMs vs 395 +/- 20 ng ferritin per 10(6) AMs, p < 0.001). AMs recovered after calcium tungstate instillation also contained increased amounts of iron and ferritin beginning 14 days after treatment, with greatest content 42 days after treatment (4.85 +/- 0.68 microgram iron per 10(6) AMs, p < 0.001, and 2274 +/- 736 ng ferritin per 10(6) AMs, p < 0.001). Tumor necrosis factor, which can enhance iron accumulation by macrophages, was spontaneously released by AMs recovered from tungsten-treated rats. These studies indicate that AMs accumulate iron and ferritin in response to both iron loading of the lungs with iron oxide exposure and lung inflammation induced by calcium tungstate exposure.

Adult↗
PubMedDate not supplied

Cellular kinetics of inflammation in the pleural space of mice in response to the injection of exogenous particles.

CD-1 mice were used to study the cellular kinetics of the inflammatory response of the pleural space to the injection of 250 micrograms of silica or of tungsten microparticles. The pleural exudates were collected by lavage of the serous cavity of mice that were sacrificed at 30 min and up to 7 days after the intrapleural instillation of the particles. The samples were studied by light and electron microscopy (transmission and scanning modes); the quantitative cellular kinetics of the inflammation was determined by leukocyte counting in exudates using cytocentrifuge preparations. The normal resident population of cells of CD-1 mice was made up of (2.47 +/- 0.37) x 10(6) cells. It consisted mostly of macrophage-like cells ((2.03 +/- 0.26) x 10(6) cells, 82% of total cells), some lymphocytes ((0.37 +/- 0.07) x 10(6) cells, 15% of total cells), a few mast cells and eosinophilic granulocytes (1-2% of total cells). The initial inflammatory reaction (30-60 min after injection) was characterized by a decrease in the number of cells harvested from the pleural space. This was followed by an intense recruitment of granulocytes and monocytes that resulted in a peak of intrapleural cells at 24 h ((16.8 +/- 4.0) x 10(6) cells induced by silica particles and (18.3 +/- 4.2) x 10(6) cells induced by tungsten particles). In tungsten-injected mice (but not in silica-treated animals) the enhancement in the number of intrapleural macrophages continued up to 72 h after particle injection. The highest percentage of macrophages with ingested tungsten (50% of total macrophages) was found early (6 h) and decreased thereafter; at day 7 it encompassed just 17% of the macrophages. Injection of any of the two particulates led to the disappearance of mast cells from the pleural space of mice. Silica particles attracted a high number of eosinophils to the pleural cavity of mice. Light and electron microscopy documented that pleural macrophages underwent striking morphological changes during the inflammatory response: the phagocytes showed marked increase in size and in number of surface processes, and their cytoplasm often contained large amounts of the injected particles and also of cellular debris. This study establishes the mouse as a reliable animal model to study the dynamics of the pleural space and it offers a precise definition of the cellular kinetics of inflammation in this serous cavity. The data indicate that the kinetics of experimental pleural inflammation induced by particulates may depend on the nature of the injected particles.

Animals↗
PubMed2002

pi-Ligands for generating transition metal-peptide complexes: coordination of amino acid derivatives to tungsten utilizing alkyne ligands.

[structure: see text] Amino acid derivatives bearing an alkyne (AA-CCH) at either the N- or C-terminus readily react with W(CO)3(S2CNMe2)2 to replace the carbon monoxides and form the novel bis-alkyne complexes W(AA-CCH)2(S2CNMe2)2; the solution behavior of these complexes shows that only the alkyne, and not the other functional groups on the amino acid, bonds to the tungsten.

Alkynes↗
PubMed1995

Roles of protein-tyrosine phosphatases in Stat1 alpha-mediated cell signaling.

Different Stat proteins are activated through phosphorylation of unique tyrosine residues in response to different cytokines and growth factors. Interferon-gamma activates Stat1 molecules that form homodimers and bind cognate DNA elements. Here we show that treatment of permeabilized cells with 200-500 microM peroxo-derivatives of vanadium, molybdenum, and tungsten results in the accumulation of constitutively phosphorylated Stat1 alpha molecules. In contrast, treatment of permeabilized cells with orthovanadate, vanadyl sulfate, molybdate, and tungstate at the same range of concentrations does not result in the accumulation of activated Stat1 alpha molecules in the absence of ligand. However, these compounds inhibit the inactivation of interferon-gamma-induced DNA-binding activity of Stat1 alpha. A 4-6-h exposure of the permeabilized cells to orthovanadate, molybdate, and tungstate, but not vanadyl sulfate, results in a ligand-independent activation of Stat1 alpha, which is blocked by the inhibition or depletion of NADPH oxidase activity in the cells, indicating that NADPH oxidase-catalyzed superoxide formation is required for the bioconversion of these metal oxides to the corresponding peroxo-compounds. Interestingly, ligand-independent Stat1 alpha activation by peroxo-derivatives of these transition metals does not require Jak1, Jak2, or Tyk2 kinase activity, suggesting that other kinases can phosphorylate Stat1 alpha on tyrosine 701.

Animals↗
PubMed2004

Liver necrosis and fulminant hepatic failure in rats: protection by oxyanionic form of tungsten.

The hepatic lesion produced as a result of oxidative stress is of wide occurrence. In the present study, the effect of tungsten on liver necrosis and fulminant hepatic failure (FHF) has been studied in rats treated with various compounds known to produce oxidative stress. Supplementation of animals with sodium tungstate for 7 weeks before the induction of liver injury by chemicals including thioacetamide (TAA), carbon tetrachloride (CCl(4)), or chloroform (CHCl(3)) could protect progression of hepatic injury. Various biochemical changes associated with liver damage and oxidative stress were measured. Hepatic malondialdehyde content, endogenous tripeptide, and reduced glutathione were measured as oxidative stress markers. The activity of xanthine oxidase, which generates reactive oxygen species (ROS) as a by-product, was also determined and found to be perturbed. Tungsten supplementation to rats caused a significant decrease in lipid peroxidation and lowered the levels of the biochemical markers of hepatic lesions produced by TAA, CCl(4) (CCl(4)), or CHCl(3). Tungsten could also cause an increase in the survival rate in rats receiving lethal doses of TAA, CCl(4), or CHCl(3). The protective effect of tungsten, however, is suggested to be limited to the conditions where the hepatic lesion is reported to be due to the generation of ROS. The progression of liver injury produced by the compounds causing oxidative stress without initiating the generation of free radicals such as bromobenzene (BB), or acetaminophen (AAP), could not be inhibited by tungsten. The possible mechanism explaining the role of oxyanionic form of tungsten in free radical-induced hepatic lesions is discussed.

Acetaminophen↗
PubMed2006

Antitumor activity of polyoxomolybdate, [NH3Pri]6[Mo7O24].3H2O, against, human gastric cancer model.

Polyoxometalates are negatively charged inorganic compounds which contain metal ions such as tungsten, molybdenum, vanadium etc. and which make clusters with the surrounding oxygen atoms. [NH3Pri]6[Mo7O24].3H2O (PM-8) was found to be a significant antitumor polyoxomolybdates. It had already been reported that the PM-8 suppressed the growth of Co-4 human colon cancer, MX-1 human breast cancer and OAT human lung cancer xenografted in nude mice. However, the mechanism of the antitumor activity has not been clarified. In this study, the antitumor activity of one of the metal oxide clusters (polyoxometalates), hexabis(isopropylammonium) heptamolybdate trihydrate, [NH3Pri]6[Mo7O24].3H2O (PM-8) were shown in an MTS assay. DNA ladder formation and detection of apoptotic bodies in nuclei were revealed that antitumor activity of PM-8 in MKN45 cells was due to apoptosis. It is concluded that the observation of significant tumor growth suppression of PM-8 in MKN45-bearing mice results from the induction of apoptosis. PM-8 shows promise as a novel anti-cancer agent.

Animals↗
PubMed2003

Investigation of the marginal adaptation of root-end filling materials in root-end cavities prepared with ultrasonic tips.

AIM: To compare the surface topography of root apices following ultrasonic root-end preparation, and again after root-end fillings submitted to three different finishing techniques. METHODOLOGY: Eighty-one root-end cavities prepared ultrasonically in human canines, were divided at random into three test groups of 27 each. The cavities were filled with Super-EBA, IRM, or ProRoot-MTA and finished by ball burnishing. Eighteen roots from each group received a final finish with either a 30-fluted tungsten carbide finishing bur, or a Zekrya carbide 28 mm bur after storage in water at 37 degrees C for 24 h. The root-end surface topographies were reproduced by means of polyvinylsiloxane impressions and epoxy resin replicas. Scanning electron micrography (SEM) images of each replica were taken prior to and after root-end filling. An image analysis system was used to compare the alteration of the marginal chipping areas and to calculate the gaps located in the dentine/root-end filling interface. RESULTS: When a bur was used to finish the set materials, a significant (P < 0.05) area of marginal chipping was eliminated. The finishing technique did not significantly (P > 0.05) affect the incidence of gaps in groups root-end filled with MTA or IRM. Super-EBA and IRM retrofillings finished with a ball burnisher or a Zekrya bur displayed a significantly (P < 0.05) larger calculated gap area than roots filled with MTA. CONCLUSION: Under this in vitro study, the marginal adaptation of MTA was good with or without finishing procedures. Applying a finishing bur over the condensed and set IRM and Super-EBA created better marginal adaptation.

Aluminum Compounds↗
PubMed1996

A New Stereoselective Synthesis of Phosphiranes.

The synthesis of phosphiranes from primary phosphines and diol ditosylates was found to be stereoselective, and chiral phosphiranes were prepared from optically pure diols. The four optical isomers of 1-mesityl-2,3-dimethylphosphirane, (2S,3S)-(+)-3, (2R,3R)-(-)-4, anti-cis-(meso)-5, and syn-cis-(meso)-6, were all synthesized from mesitylphosphine and the corresponding diol ditosylates. Compound 6 was unstable, but compounds 3, 4, and 5 were all isolated in pure form. Their structure assignments were based on the NMR coupling constants J(P-H) and J(P-C). The phosphiranes were transformed into tungsten pentacarbonyl complexes. Tungsten tetracarbonyl-triphenylphosphine complexes (22, 23, 24) of compounds 3, 4, and 5 were synthesized in high yields by the reaction of the phosphiranes and W(CO)(4)(PPh(3))(THF). The absolute stereochemistry of the phosphiranes 3, 4, and 5 was determined by X-ray crystal structure analysis of compounds 22, 23, and 24. Stereochemical effects on NMR coupling constants and mass spectra of the phosphiranes are discussed.

Journal Article↗
PubMed2000

Effect of fluorine substitution on the interaction of lipophilic ions with the plasma membrane of mammalian cells.

The effects of the anionic tungsten carbonyl complex [W(CO)(5)SC(6)H(5)](-) and its fluorinated analog [W(CO)(5)SC(6)F(5)](-) on the electrical properties of the plasma membrane of mouse myeloma cells were studied by the single-cell electrorotation technique. At micromolar concentrations, both compounds gave rise to an additional antifield peak in the rotational spectra of cells, indicating that the plasma membrane displayed a strong dielectric dispersion. This means that both tungsten derivatives act as lipophilic ions that are able to introduce large amounts of mobile charges into the plasma membrane. The analysis of the rotational spectra allowed the evaluation not only of the passive electric properties of the plasma membrane and cytoplasm, but also of the ion transport parameters, such as the surface concentration, partition coefficient, and translocation rate constant of the lipophilic anions dissolved in the plasma membrane. Comparison of the membrane transport parameters for the two anions showed that the fluorine-substituted analog was more lipophilic, but its translocation across the plasma membrane was slower by at least one order of magnitude than that of the parent hydrogenated anion.

Animals↗