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PubMed1992

Acute renal injury by tetraethyl orthosilicate in mice: ultrastructure, histochemistry and X-ray microanalysis.

Tetraethyl orthosilicate (Si(OC2H5)4, or TEOS) is a silicon-containing compound which has widespread industrial applications and which has been documented as biohazardous. The histopathological features and mechanism of TEOS toxicity in the kidney of ICR mice were investigated in a light and electron microscopy study, which included energy dispersive X-ray microanalysis. TEOS was given to mice as intraperitoneal injection of approximately 1,670 mg/kg body weight in experiments based on a 24 h time-scale. Tissues were examined after sampling either immediately on death if this occurred within 24 h or, in the case of surviving animals, after sacrifice at 24 h. Renal injury was considered to be the most probable cause of death, on the basis of the following main findings: 1) acute tubular necrosis (glomerular lesions were absent); 2) a dense deposit of silicon over the microvilli of dead tubular epithelial cells; 3) an abundant aggregation of hydroxyapatite crystals containing calcium in the cytoplasm and mitochondria of the dead tubular epithelial cells; and 4) abundant myelinosomes and some hydroxyapatite crystals in the cytoplasm of viable proximal convoluted tubule epithelial cells. It was speculated that silicon compounds may bind to the plasma membranes of the proximal convoluted tubule epithelial cell microvilli and damage or interfere with membrane calcium channels. The resulting calcium ion imbalance may play a role in the subsequent progression of acute tubular necrosis by TEOS.

Animals↗
PubMed1993

In vivo degradation of silicones.

29Si nuclear magnetic resonance (NMR) spectroscopy is applied to study the degradation of polysiloxanes (silicones) in vivo. Our results with animal models show that silicone migrates from the implant to the liver (29Si resonance at -20 ppm) and new silicon containing compounds form after the silicones are introduced into the rats. The new 29Si resonances in the chemical shift range of -40 to -85 ppm are related to hydrolyzed silicone, those at -90 to -115 ppm are indicative of the presence of silica (SiO2), and the peaks observed at -120 to -150 are related to high coordinated silicon complexes. These resonances are not present in the 29Si spectra of the silicones before implantation. Our findings demonstrate that silicones are not metabolically inert.

Animals↗
PubMed1987

Gas chromatography-mass spectrometry of monohydroxyeicosatetraenoic acids as their methyl esters trimethylsilyl, allyldimethylsilyl and tert.-butyldimethylsilyl ethers.

The gas chromatographic and mass spectrometric properties of the monohydroxy acids 5-hydroxyeicosatetraenoic acid (5-HETE), 12-hydroxyeicosatetraenoic acid (12-HETE) and 15-hydroxyeicosatetraenoic acid (15-HETE) as their methyl ester trimethylsilyl, methyl ester allyldimethylsilyl and methyl ester tert.-butyldimethylsilyl ethers were investigated. The gas chromatographic properties of the trimethylsilyl and tert.-butyldimethylsilyl derivatives were found to be excellent while the allyldimethylsilyl derivative required a well deactivated column. The mass spectra of these silyl derivatives with the exception for 12-HETE did not exhibit particularly intense ions in the upper mass region. A quantitative analysis by selected-ion monitoring of the most intense ion in the upper mass region of respective mass spectrum demonstrated that a detection limit in the low picogram range could only be obtained for 12-HETE. Since the mass spectra indicated that the double bonds exerted a strong influence on the fragmentation pattern, the trimethylsilyl, allyldimethylsilyl and tert.-butyldimethylsilyl ethers of the methyl esters of the reduced analogues of the monohydroxy acids were prepared. The saturation of the double bonds completely altered the fragmentation patterns and very intense ions carrying a high percentage of the total ion abundance were found in all of the mass spectra. The developed technique was utilized for measurements of 5-HETE in lung tissue samples from patients with lung cancer.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1985

Infrared spectroscopic studies of the effect of elevated temperature on the association of pyroglutamic acid with clay and other minerals.

Fourier transform i.r. measurements of L-pyroglutamic acid dispersed in a matrix of a clay, silica or alumina have been obtained at various temperatures between 25 and 220 degrees C. The i.r. spectrum of L-pyroglutamic acid varies in a manner dependent upon the matrix material and shows considerable change as the temperature of the mixtures is increased. The differences in the spectrum at elevated temperatures are explained in terms of a chemical reaction between hydroxyl groups in the matrix and the carboxylic acid. The i.r. spectra of trimethylsilyl derivatives of L-pyroglutamic acid and aluminum pyroglutamate were also measured to assist the understanding of spectra and interpretation of the spectral changes dependent upon increasing temperature.

Aluminum Oxide↗
PubMed2006

Utilization of starch and clay for the preparation of superabsorbent composite.

Starch and attapulgite were utilized as raw material for synthesizing starch-graft-poly(acrylic acid)/attapulgite superabsorbent composite by graft copolymerization reaction of starch and acrylic acid (AA) in the presence of attapulgite micropowder in aqueous solution. Major factors affecting on water absorbency such as weight ratio of AA to starch, initial monomer concentration, neutralization degree of AA, amount of crosslinker, initiator and attapulgite were investigated. The superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10 wt% exhibit absorption of 1077 g H(2)O/g sample and 61 g H(2)O/g sample in distilled water and in 0.9 wt% NaCl solution, respectively. This superabsorbent composite with excellent water absorbency and water retention under load, being biodegradable in nature, economical and environment-friendly, could be especially useful in agricultural and horticultural applications.

Absorption↗
PubMed2005

Formulation and characterization of a novel fluoride-releasing dental composite.

OBJECTIVES: The aims of this study were to formulate a novel fluoride-releasing dental composite and to evaluate its mechanical properties, fluoride release and recharge capabilities, water sorption and solubility. METHODS: A fluoride-releasing dimethacrylate monomer containing a ternary zirconium fluoride chelate was synthesized. Three experimental fluoride-releasing composites were fabricated with different monomer formulas (wt.%)-(1) Control A: 40 BisGMA/40 TEDMA/20 UEDMA; (2) EXPERIMENTAL: 20 F-releasing monomer/20 BisGMA/40 TEDMA/20 UEDMA; (3) Control B: the same formula as Control A except that it contained 10 wt.% (of total monomer) tetrabutylammonium fluoride (TBAF), which had a fluoride content equivalent to EXPERIMENTAL. All three materials had the same filler content: 55 wt.% silanized fluoroaluminosilicate particles (0.8 microm) and 10 wt.% silanized fumed silica (14 nm). All materials contained 0.17 wt.% camphorquinone (CQ) as a photoinitiator and 0.69 wt.% ethyl-4-dimethylaminobenzoate (4EDMAB) as an accelerator. The materials were tested for fluoride release (for 184 days), fluoride recharge, compressive and flexure strength, water sorption and solubility. The data were analyzed using ANOVA and Tukey-HSD tests, and Kruskal-Wallis test. RESULTS: The experimental composite had significantly higher fluoride release and fluoride recharge capabilities than both Control composites. It had significantly better physical and mechanical properties than Control B. SIGNIFICANCE: The combined use of the fluoride-releasing dimethacrylate monomer and fluoride-releasing filler can provide sustained high fluoride release and recharge as well as acceptable mechanical and physical properties. Simply adding organic fluoride salt in the monomer yields composites with poor mechanical and physical properties.

4-Aminobenzoic Acid↗
PubMed1987

The lung biological activity of American attapulgite.

Attapulgite is a fibrous mineral industrially consumed at the rate of over a million tons per year but the biological activity of the material is not fully known. To evaluate the in vivo toxicity of the fibrous material, we exposed the tracheal lobe of 16 sheep to a single exposure of either 100 ml saline, 100 mg UICC asbestos fibers in 100 ml saline, 100 mg short asbestos fibers in 100 ml saline, or 100 mg attapulgite in 100 ml saline. The animals were studied by bronchoalveolar lavage (BAL) at Days 2, 12, 24, 40, and 60 and by autopsy at Day 60. In the saline-exposed sheep, BAL and lung histology did not change. In the UICC asbestos-exposed animals, we reproduced the BAL changes previously reported (R. Bégin, M. Rola-Pleszczynski, S. Massé, Y. Berthiaume, and G. Drapeau, 1985, Environ. Res. 36, 389-404). In the short asbestos-exposed sheep, there were no significant BAL changes. In the attapulgite sheep, we found significant and sustained increases in total BAL cells (X2, P less than 0.05), macrophages (X2, P less than 0.05), neutrophils (X5, P less than 0.01), fibronectin (X2-3, P less than 0.05), lactate dehydrogenase (X2, P less than 0.05), beta-glucuronidase (X2, P less than 0.05), but BAL cellularity returned to control levels by Day 60 whereas in the UICC asbestos-exposed sheep, it remained significantly above control. Lung histology demonstrated the characteristic peribronchiolar fibrosing alveolitis in the UICC asbestos-exposed sheep, whereas macrophagic alveolitis with minimal airway distortion was seen in the short asbestos-exposed sheep and in all of the attapulgite-exposed sheep but three which had typical peribronchiolar alveolitis quite similar to that observed in UICC-exposed sheep, but of lower intensity. In conclusion, the study documents that attapulgite is not an inert material for lung tissue; it does produce a macrophagic and neutrophilic alveolitis in the early inflammatory phase of lung reaction with peribronchiolar involvement in some sheep. Whether or not this initial attapulgite induced alveolitis leads to lung fibrosis remains to be evaluated in a longer follow-up study of attapulgite-exposed animals.

Animals↗
PubMed1989

Gas-liquid chromatography-mass spectrometry of mono- and dithiols as their tert.-butyldimethylsilyl derivatives.

The use of gas-liquid chromatography and mass spectrometry with derivatizing agents that give stable derivatives and consistent fragmentation patterns allows for accurate identification of a variety of compounds. In this study either N-methyl-N-tert.-butyldimethylsilyltrifluoroacetamide or N-tert.-butyldimethylsilylimidazole were employed to derivatize a range of mono- and dithiols: from ethanethiol to 1-hexadecanethiol and 1,2-ethanedithiol to 1,9-nonanedithiol. When analyzed in this way, the resulting tert.-butyldimethylsilyl derivatives of the 24 thiols tested were readily distinguishable. Complete baseline separation of each derivative by capillary gas-liquid chromatography was achieved, and each produced a prominent mass minus 57 [M+. - 57] fragment ion. The tert.-butyldimethylsilyl-thioethers were colorless and were stable at room temperature for over 3 months. This method may provide a convenient approach to the analysis of thiol compounds from a wide variety of sources.

Gas Chromatography-Mass Spectrometry↗
PubMed1995

Organic molecules in the gas phase of dense interstellar clouds.

Since a previous COSPAR review on this subject, the number of molecular species identified by astronomers in dense interstellar clouds or in the envelopes expelled by evolved stars has grown from about eighty to approximately one hundred. Recent detections in stellar envelopes include the radical CP, the second phosphorus-containing astronomical molecule; SiN, the first astronomical molecule with a Si-N bond; and the HCCN radical. In the dense interstellar clouds recent detections or verifications of previous possible identifications include the H3O+ ion, which is a critical intermediary in the production of H2O and O2; the CCO radical, which is isoelectronic with HCCN; the SO+ ion, which appears to be diagnostic of shock chemistry; two new isomers of cyanoacetylene, HCCNC and CCCNH; and the two cumulenes H2C3 and H2C4. Some recent work is also described on the mapping of interstellar clouds in multiple molecular transitions in order to separate variations in chemical abundance from gradients in physical parameters.

Astronomical Phenomena↗
PubMedDate not supplied

[The interaction of Bradyrhizobium japonicum with clay minerals].

It is shown that such clay minerals as palygorskite and montmorillonite stimulate growth activity of Bradyrhizobium japonicum. The bacteria come into contact with the above minerals. Granulated preparations of rhizobia have been developed on the basis of the results obtained. These preparations are characterized by the high yield of viable cells and a possibility of long-term storage. The use of montmorillonite in production of granulated preparations provides the higher yield of viable bacteria in the preparations and stability of their composition under long-term storage.

Aluminum Silicates↗
PubMed2006

[Profiles of sediment porewater nutrient concentrations on tidal flat of turbidity maximum zone in Changjiang (Yangtze River) estuary].

Profiles of nutrients (i.e., NH4+, NO2-, NO3-, PO4(3-), and SiO3(2-)) in porewater of sediment were investigated monthly in the intertidal flat of Chongming Dongtan in Changjiang (Yangtze River) estuary during March 2005 to February 2006. The results indicate that concentrations of NH4+ and SiO3(2-) in porewater are always in the range of 200 micromol/L to 500 micromol/L and show different patterns of distribution profile among high, middle, and low marshes. Compared to high and middle marsh, low marsh, without vegetation coverage and of coarser grain size, generally contains higher NH4+ and lower SiO3(21) concentrations. SiO3(2-) concentrations are predominantly determined by seasonal temperature change, but variations of NH4+ are more complicated and prone to exhibit lower values in spring and summer when the vegetation above show relatively high growth rate. Concentrations of NO2- + NO3- and PO4(3-) in porewater are commonly much lower than NH4+ and SiO3(2-) by 2 to 3 orders of magnitude, however, due to factors such as bioturbation, the concentrations in top sediment may be higher than 10 micromol/L. The relatively high NO3- concentration in top sediment,together with the rapid transfer from oxygenic to anoxic environment, make it possible that significant denitrification happens, which may draw its remarkable influence on the biogeochemical cycles of nutrient elements in the land-sea interaction area in Changjiang (Yangtze River) estuary.

China↗
PubMed1998

Silicon exposure and vasculitis.

A combination of risk factors are involved in susceptibility to a primary or secondary form of vasculitis. Most forms of vasculitis are probably genetically based but environmentally triggered. This review discusses currently available evidence for a pathophysiologic role of one possible environmental trigger, silica. Since 1960, several patients with pulmonary silicosis have been described that developed pauci-immune necrotizing crescentic glomerulonephritis, i.e., with either completely negative immunofluorescence findings or nonspecific granular IgM or C3 deposits along the capillary wall. Recently it was reported that these patients have antineutrophil cytoplasmic antibodies (ANCAs) that are in most cases directed to myeloperoxidase. Further, patients with pulmonary silicosis may develop microscopic polyangiitis, the syndrome of lung hemorrhage and nephritis, or Wegener's granulomatosis. To further substantiate the relation between silicon exposure and renal failure or vasculitis, several case-control studies have been reported. Exposure to silicon-containing compounds was found to be related to chronic renal failure (odds ratio, 1.7:2.5) or vasculitis (odds ratio, 6.5:14.0). The mechanisms by which silica may induce ANCA-associated glomerulonephritis or vasculitis are not well known. Silicon-containing compounds have a pronounced adjuvant effect on immune responses, and silica particles are potent stimulators of lymphocytes and monocytes or macrophages. Further, silica may induce apoptosis of monocytes or macrophages and possibly neutrophils. In conclusion, at present there is ample evidence that occupational exposure to silicon-containing compounds is related to the development of ANCA-associated glomerulonephritis and vasculitis, and silica is one of the first well-documented environmental triggers in these diseases.

Adult↗