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At least 451 records · Page 25Linked to original sources
PubMed1994

Biopersistence of man-made vitreous silicate fibers in the human lung.

There is now a substantial body of experimental data on the pulmonary biopersistence of man-made vitreous silicate fibers (MMVSF), but human data are seriously lacking. Our knowledge in this field is essentially limited to a few reports of measurements of fibers retained in lung tissue samples taken at autopsy from workers manufacturing these products. Three types of exposure were studied: fibrous glass, mineral wool, and refractory ceramic fibers. Overall, the available data do not provide evidence for substantial long-term retention of fibers in the human lung after occupational exposure to MMVSF dusts. A word of caution, however; the amount of data supporting the previous statement is much greater for fibrous glass than for either mineral wool or refractory ceramic fibers. There is no human data on the key question of the kinetics of pulmonary clearance of inhaled MMVSF.

Calcium Compounds↗
PubMed1983

Interaction between erythrocyte plasma membrane and silicate dusts.

Lysis of erythrocytes in vitro leading to release of hemoglobin has often been used as a convenient test system for predictive toxicological evaluation of noxious particulates encountered as pollutants in occupational and environmental atmospheres. However, in spite of several studies with silica and silicate dusts, the exact biochemical mechanism for membrane damage is not clear. Therefore, detailed biochemical studies were conducted. Screening of a large number of fugitive dust samples indicated that the dissolution of silica under assay conditions has a qualitative relation to hemolytic potency. The strong capacity of slate mine dust to cause hemolysis was studied in detail. The kinetics of lysis indicated that on prolonged contact the adsorption of hemoglobin altered the lytic index. Coating of dust with serum, albumin or polyvinylpyrrolidone (PVP) and some lipids reduced lytic potency markedly, while EDTA was ineffective. Altering the surface chemistry of dust by heating, alkali treatment, washing with water, and acid washing reduced hemolysis in increasing order. Thus, chemical interactions between dusts and membranes are involved in hemolysis, and it may be concluded that the interaction of dust constituents with biomembranes is one of the likely mechanisms involved in the toxicity of particulate air pollutants.

Adsorption↗
PubMed2006

Adsorption and recovery of alkylphenol polyethoxylates from synthetic wastewater using hexagonal mesoporous silicate.

A large amount of alkylphenol polyethoxylate (APnEOs), one of endocrine disrupters, is disposed of directly to biological wastewater treatment plants. But microbial oxidation processes cannot completely degrade these molecules to nontoxic forms. Adsorption and recovery efficiency of APnEOs was investigated using four different types of Hexagonal Mesoporous Silicate (HMSs) and powdered activated carbon (PAC). HMSs were synthesized by surfactant-templating methods, and two of them were subsequently grafted with surface functional groups. The two types of organic functional groups grafted on the surface were n-octyldimethyl- and 3-mercaptopropyl- groups. Titanium substituted HMS was also made in the same way as HMS. Adsorption of APnEOs on synthesized HMSs was higher than that on PAC. Larger pore sizes of HMS and Ti-HMS enhanced accessibility of APnEOs to active surface sites in mesopores, which realized higher adsorption capacities and L-shape (Langmuir) adsorption isotherms. Adsorption capacities of APnEOs are influenced by water solubility of APnEOs. APnEOs adsorbed on HMSs can be completely recovered by a mixture of alcohol and water at 5:5 ratio, which is more effective than the recovery from PAC.

Adsorption↗
PubMed2006

Controlled release calcium silicate based floating granular delivery system of ranitidine hydrochloride.

The objective of the present investigation was to prepare and evaluate floating granular delivery system consisting of (i) calcium silicate (CS) as porous carrier; (ii) ranitidine hydrochloride (RH), an anti-ulcer agent; and (iii) hydroxypropyl methylcellulose K4M (HPMC) and ethylcellulose (EC) as matrix forming polymers. The effect of various formulation and process variables on the particle morphology, particle size, micromeritic properties, percent drug content, in vitro floating behavior, and in vitro drug release from the floating granules was studied. The scanning electron microscopy (SEM) of granules revealed that that more pores of CS in secondary coated granules (SCG) were covered by the polymer film than those in primary coated granules (PCG). The formulation demonstrated favorable in vitro floating and drug release characteristics. The in vivo evaluation for the determination of pharmacokinetic parameters was performed in albino rats. Higher plasma concentration was maintained throughout the study period from the floating granules of RH. The enhanced bioavailability and elimination half-life observed in the present study may be due to the floating nature of the dosage form. The results suggested that CS is a useful carrier for the development of floating and sustained release preparations.

Animals↗
PubMed2005

The effect of heating on the dissolution of alkaline earth silicate fibers in a simple amino acid solution and water.

In order to evaluate the effect of pre-heating on biosolubility and water-resistance of alkaline earth silicate (AES) fibers in MgO-SrO-SiO2 and MgO-CaO-SrO-SiO2 compositions, dissolution experiments of the heat-treated (from 110 degrees C to 1,260 degrees C) AES fibers have been carried out in a glycine solution and in distilled water at 40 degrees C for 50 h. The dissolution experiments show that the heat-treatment around 700 degrees C has made the AES fibers more soluble in the glycine solution. This is due to the phase separation of the AES fibers resulting from the heat-treatment. Probably, alkaline earth-rich glassy phases formed by the phase separation facilitate the dissolution of the heat-treated AES fibers in the glycine solution. The heat-treatment around 700 degrees C is possible to decrease the toxicity of the AES fibers further. Meanwhile, this heat-treatment around 700 degrees C has given little effect on the dissolution of the AES fibers in the distilled water. This indicates that the resistance of the AES fibers to water or humidity remains unaffected by the heat-treatment. The water-resistance is a very useful property for MMVFs. This study suggests that the heat-treatment around 700 degrees C is probably an useful treatment in order to enhance the total performance, biosolubility and water-resistance, of AES fibers.

Glycine↗
PubMed1979

Radiopaque zones in the dentin beneath silicate fillings analyzed by electron microprobe.

Seven teeth which showed radiopaque zones beneath silicate fillings were sectioned and studied by microradiography and electron microprobe analysis in order to elucidate which elements were responsible for the increased absorption of X-rays and whether the presence of carious lesions could be masked by foreign elements in the tissue. The Ca concentration was frequently found to be either slightly increased or reduced compared with radiographically unaltered dentin. Increased concentrations of F and Zn occurred in the radiopaque zones. The highest F concentrations (0.4--1%) were recorded in zones with an increased Ca content. The highest Zn concentrations (5--8%) were found in the three specimens having a reduced Ca content. The possible conditions responsible for the increased Ca, F and Zn concentrations are discussed. The results indicate that both Ca and Zn may contribute to the increased absorption of X-rays. The hypothesis that carious dentin may be obscured in intraoral radiographs by the presence of foreign elements in the tissue, was not substantiated.

Calcium↗
PubMed1976

[Epidemiologic studies. I. Secondary caries in tooth areas restored by silver-tin-amalgam, silicate cement or inlays].

On the basis of epidemiologic studies on 10 106 sugjects from the population of the town of Rostock, the authors deal with the frequency of filled tooth areas and their affection by secondary caries with special regard to filling materials (silver-tin amalgam, silicate cement, inlay). The low frequency of secondary caries in tooth areas restored by means of inlays is noteworthy. Finally, the authors give recommendations for practice.

Adolescent↗
PubMed2003

Electrokinetic characteristic and coagulation behavior flocculant polyaluminum silicate chloride (PASiC).

The electrokinetic characteristics and coagulation behaviors of polyaluminum silicate chloride (PASiC) and polyaluminum chloride (PAC) were studied and compared by streaming current (SC) measurement and jar test method. The experimental results showed that the interaction between polysilicic acid characterized negative charge and hydrolyzed aluminum species result in a decrease of the charge-neutralizing ability of PASiC, compared to PAC. The decrease has a close relationship with the basicity (B) and Al/Si molar ratio in PASiC. The less the B value and the Al/Si molar ratio, the lower the charge-neutralizing ability of PASiC is. In contrast, the preparation technique for PASiC affects the charge - neutralization of PASiC to a smaller extent. In addition, compared with PAC, PASiC may enhance aggregating efficiency and give better coagulating effects.

Aluminum Hydroxide↗
PubMed2004

[Preparation of polyaluminum silicate chloride (PASC) from tetraethylorthosilicate (TEOS) and its physicochemical characteristics].

A new type of polyaluminum silicate chloride [PASC(A)] was prepared by employing tetraethylorthosilicate (TEOS) as silicon source. By comparing PASC(A) with the conventional product [PASC(B)], the effects of B value and Si/Al molar ratio on the pH value and the Zeta potential of PASC(A) were investigated. The influence of the incorporation of silicon into PASC on the molecular structure and aluminium species was also studied by acidification method and 27Al NMR spectroscopy. The results show that the PASC(A) has higher polymerization degree, narrow distribution of molecular weight and symmetrical distribution of aluminium and silicon in PASC molecule. It is more difficult to be acidified, and moreover, it can reduce the loss of Al13 species. All the above advantages of PASC(A) are due to its special synthesis method.

Aluminum Silicates↗
PubMed2001

A clinical study of a silicate toothpaste with extract from propolis.

Propolis is bee-produced substance with pronounced anti-inflammatory effect. It is an ingredient of many drugs; it is added to toothpastes as a prophylactic component for periodontal diseases. The plaque-cleaning, plaque-inhibiting and anti-inflammatory actions of the silicate paste were studied. The study included 42 individuals in good clinical health and a minimum of 20 intact teeth - 11, 16, 24, 31, 36, 46. Control exams were performed on days 1, 7, 14, 21 and 28. The baseline values gradually decreased after each control tooth brushing with a statistically significant difference between them. The toothpaste shows very good plaque-cleaning, plaque-inhibiting and anti-inflammatory effect.

Adolescent↗
PubMedDate not supplied

[On the influence of silicate feeding on metabolism of 137Cs in rabbit].

The features of 137Cs metabolism in the rabbit's organism when feeding on silicates were investigated. By results of two experiments on rabbits radiosorption by of zeolite, saponit, humolit, vermiculite and palygorskit in the gastrointestinal tract was evaluated. It was found that vermiculite and palygorskit had the strongest influence on processes of accumulation and decorporation 137Cs, when a dose of additives was 5% of the weight of forage.

Animal Feed↗
PubMed2006

Silicate improves growth and ion absorption and distribution in aloe vera under salt stress.

Si 2.0 mmol/L in irrigation solution alleviated significantly the inhibition of NaCl stress of 100 or 200 mmol/L to aloe growth. Exogenously applied Si decreased significantly Na(+) and Cl(-) contents, increased K(+) content and K(+)/Na(+) ratio and selectivity ratio of absorption (AS(K, Na)) and of translocation (TS(K, Na)) to K(+) and Na(+) in aloe plant under both NaCl 100 and 200 mmol/L stresses for 30 d. In this way, the ion homeostasis in aloe plant under NaCl stress was maintained, as was proved by X-ray microanalysis of root tip and leaf across sections. One of the mechanisms to achieve this may be the significant enhancement of H(+)-ATPase activities by the addition of silicate in plasma membrane and tonoplast, H(+)-pyrophosphatase (H(+)-PPase) activity in tonoplast isolated from aloe root tips under NaCl stress.

Absorption↗
PubMed2006

[Research of Hg2+ sol-gel membrane made of organically modified silicates].

A photochemical sensor for the determination of Hg2+ consisting of organically modified silicates (ormosils) was developed. Hg(2+)-sensitive fluorescent sol-gel films were prepared by co-condensation of tetramethoxysilane (TMOS) and dimethyldimethoxysilane (DMOS), and the fluorescent indicator 5,10,15, 20-tetra (p-sulfonatophenyl) porphyrin sodium was embedded in sol-gel in the form of ion pairs with cetyltrimethyl ammonium bromide. The optimization condition of preparation and response performance of sol-gel membrane were investigated. The experimental results showed a linear range of Hg2+ concentrations from 1.0 x 10(-5) to 1.0 x 10(-4) mol x L(-1) in a Tris-HCl buffer at pH 8.0 with fast response and good repetition. The indicators in the sol-gel membrane did not leak out and the sensor showed good selectivity over other metal ions.

Gels↗
PubMed1985

Purification of human urinary erythropoietin on controlled-pore glass and silicic acid.

Erythropoietin (Epo) has been isolated from raw human urine of anemic patients by controlled-pore glass and silicic acid chromatography. A purification factor of not less than 100-fold and recovery of about 80% of activity was routinely achieved. The resulting Epo preparation is active both in vivo and in vitro and can be neutralized by an antibody to human Epo indicating the native state and identity of the isolated Epo molecule. The preparation is stable at near neutral pH and is amenable to further purification.

Animals↗
PubMed1984

Palliative therapy of tumor-induced pleural effusions with 90Yttrium-silicate.

In 20 patients with rapidly recurring malignant pleural effusion, 90Yttrium-silicate was intrapleurally instilled after the puncture. In all patients this treatment resulted in marked reduction, or even interruption, of exudate formation. Eleven patients died with an average survival of 166 days. Nine patients are still alive and have been followed up for a mean of 140 days without the pleural effusion recurring. Side effects were not observed, either subjectively or in relation to hematological and other laboratory findings.

Adult↗
PubMed1994

[Death from fluoro-silicate in floor polish].

A fatal case of poisoning due to ingestion of an apparently innocuous household product is described. A healthy 28-year-old man accidentally drank floor polish (Cristalizador, a Spanish import). On arrival at the emergency room a few hours later he passed large amounts of bloody stool and lost consciousness. A call to the Spanish Poison Center revealed that although not indicated on the label, the polish contained a highly poisonous salt, fluoro-silicate. Blood gas analysis revealed severe metabolic acidosis. Serum calcium was 3.8 mg/dL. The post-resuscitation ECG showed subendocardial ischemia and ST-elevation in the anteroseptal wall and prolonged QT-interval. In the intensive care unit he received large amounts of fluids, dopamine, sodium bicarbonate and calcium. Despite the treatment, his condition continued to deteriorate: VPB's appeared, there was a short run of ventricular tachycardia and then atrial fibrillation developed. Further treatment included lidocaine, verapamil, amiodarone, and electrical cardioversion. Blood pressure remained low and 11 hours after admission he died of myocardial infarction, severe arrhythmia and multi-organ failure.

Adult↗
PubMed2006

Affinity adhesion of carbohydrate particles and yeast cells to boronate-containing polymer brushes grafted onto siliceous supports.

Cross-linked agarose particles (Sepharose CL-6B) and baker's yeast cells were found to adhere to siliceous supports end-grafted with boronate-containing copolymers (BCCs) of N,N-dimethylacrylamide at pH> or =7.5, due to boronate interactions with surface carbohydrates of the particles and the cells. These interactions were registered both on macroscopic and on molecular levels: the BCCs spontaneously adsorbed on the agarose gel at pH> or =7.5, with adsorption increasing with pH. Agarose particles and yeast cells stained with Procion Red HE-3B formed stable, monolayer-like structures at pH 8.0, whereas at pH 7.0-7.8 the structures on the copolymer-grafted supports were less stable and more random. At pH 9.0, 50 % saturation of the surface with adhering cells was attained in 2 min. Stained cells formed denser and more stable layers on the copolymer-grafted supports than they did on supports modified with self-assembled organosilane layers derivatized with low-molecular-weight boronate, presumably due to a higher reactivity of the grafted BCCs. Quantitative detachment of adhered particles and cells could be achieved by addition of 20 mM fructose--a strong competitor for binding to boronates--at pH 7.0-9.0. Regeneration of the grafted supports allowed several sequential adhesion and detachment cycles with stained yeast cells. Affinity adhesion of micron-sized carbohydrate particles to boronate-containing polymer brushes fixed on solid supports is discussed as a possible model system suggesting a new approach to isolation and separation of living cells.

Acrylamides↗