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PubMed2001

Dispersion of Silica Fines in Water-Ethanol Suspensions.

The dispersion of silica fines in water-ethanol suspensions has been studied through the measurement of settling efficiency, wetting rate, zeta potential, and viscosity. The measurements were performed on two silica samples with mean volumetric diameters of 5.02 and 0.272 &mgr;m at different fractions of ethanol in water-ethanol suspensions. The results have demonstrated that the dispersion stability of the silica suspensions increased as the fraction of ethanol increased and reached to maximum at the fraction of 50%, followed by a decline. The stability was stronger in a pure ethanol suspension than in a pure water suspension. It was observed that the stability closely correlated with the lyophilicity of the particles, but was not predominated by the surface charge of the particles as predicted by the DLVO theory. Viscosity measurements have been used to estimate the solvation film thickness on silica particles immersed in water-ethanol suspensions, on the basis of Einstein's theory of the viscosity of dispersions. It was found that the solvation film thickness on silica fines in a water-ethanol (1 : 1) suspension is about double that in a pure water suspension and about 1.4-fold that in a pure ethanol suspension, respectively, which well explains the dispersion behaviors of the silica fines in the water-ethanol suspensions because a thicker solvation film will cause a stronger disjoining pressure to prevent the proximity of the particles. Copyright 2001 Academic Press.

Journal Article↗
PubMed2002

Role of interferon-gamma in the development of murine bronchus-associated lymphoid tissues induced by silica in vivo.

Exposure to silica is associated with the development of chronic airflow obstruction as well as pulmonary fibrosis, probably mediated in part by silica-induced small airway disease. To elucidate the mechanism of mucosal immune responses in the small airways, we analyzed the roles of interferon-gamma (IFN-gamma) using mice deficient of this cytokine in silicotic lung. IFN-gamma knockout mice (-/-) and wild-type C57BL/6 mice were treated with either a single fibrogenic dose of silica or an equivalent volume of saline and euthanized 21 days after intratracheal instillation. Total cell counts in bronchoalveolar lavage fluids increased in silica-instilled mice compared to saline-instilled mice, but there were no significant differences between IFN-gamma knockout mice and wild-type mice treated with silica. Morphometric estimation for fibrotic lesions within the lung did not show any differences between these mice. However, bronchus-associated lymphoid tissues (BALT), which are known to be involved in the mucosal immune responses, were significantly larger in the lungs of IFN-gamma knockout mice than in those of wild-type mice treated with silica. In addition, we evaluated the development of BALT in interleukin 4 (IL-4) knockout mice in order to clarify the effect of Th2 cytokine. Morphometric estimation for BALT did not show any differences between IL-4 knockout mice and wild-type mice in silicotic lung. These results suggest that IFN-gamma has an inhibitory effect on the development of BALT and may be involved in small airway disease in silicotic lung.

Animals↗
PubMed1983

Is silica involved in neuritic (senile) plaque formation?

The agent responsible for inducing neuritic (senile) plaque formation in senile dementia of the Alzheimer's type and in the ageing non-demented brain is unknown. Other workers have detected a high concentration of silicon in the rims and cores of senile neuritic plaques. We have therefore looked at whether the reaction of brain tissue to silica particles resembles a neuritic plaque. In this study both fine (10 nm) and coarse (less than 5 microns) particles of silica have been introduced into the brains of rats and mice using a wide range of doses and several methods of administration. The reaction of the brain to the presence of the silica was examined by light and electronmicroscopy up to one year after the injection. The presence of silica particles in the brain resulted in the proliferation of fibrous astrocytes and macrophages and strongly stimulated the production of collagen fibres. Degeneration of some adjacent axons and axon terminals occurred, but there was no detectable deposition of amyloid which is characteristic of senile plaques. Coarse particles of silica invariably produced a more intense reaction than fine particles. The reaction of the brain did not diminish with time within one year of injection. The possible significance of the presence of silica in the plaque as a secondary phenomenon is discussed.

Alzheimer Disease↗
PubMed1995

Attenuation of acute inflammatory effects of silica in rat lung by 21-aminosteroid, U74389G.

Chemical alteration of the glucocorticoid, methylprednisolone, has led to the introduction of a new class of compounds called the 21-aminosteroids (21-ASs). The purpose of this study was to investigate the effect of the 21-AS, U74389G, on silica-induced acute lung injury. Male Fischer 344 rats were treated intraperitoneally with saline or U74389G in a total dose of 15 mg/kg divided into three injections of 5 mg/kg separated by 4 h. Following the first treatment, animals from the two groups were intratracheally instilled with silica (10 mg/100 g body wt in 0.5 ml of saline) or saline vehicle (0.5 ml). Twenty-four hours after the instillations, bronchoalveolar lavage (BAL) was performed. In the animals not receiving U74389G, marked increases in total protein, beta-glucuronidase, and lactate dehydrogenase (LDH) activities and number of neutrophils (PMNs) were demonstrated in the BAL fluid of the silica-treated animals compared to their controls. Silica also caused dramatic increases in the luminol-dependent chemiluminescence (CL) of lung tissue and BAL cells. The CL reaction was decreased by superoxide dismutase (SOD) and N-nitro-L-arginine methyl ester hydrochloride (L-NAME), a nitric oxide (NO) synthase inhibitor. In animals treated with U74389G, there was attenuation of the silica-induced increases in biochemical, cellular, and chemiluminescent indices of damage. This study demonstrates that U74389G significantly reduces acute lung injury caused by the intratracheal instillation of silica, and this drug may be of potential value for treatment of lung diseases in which damage caused by reactive oxygen species has been implicated.

Acute Disease↗
PubMed2003

Monolithic silica columns with chemically bonded beta-cyclodextrin as a stationary phase for enantiomer separations of chiral pharmaceuticals.

An enantioselective silica rod type chiral stationary phase (CSP) is presented; a novel combination of the well known enantiomer separation properties of beta-cyclodextrin and the unique properties concerning the flow behavior of silica monoliths. Two different synthesis routes are described, and it was found that the in situ modification of a plain silica rod column turned out to be the best. The chromatographic behaviour of the beta-cyclodextrin silica rod was studied and compared with a very similar commercially available beta-cyclodextrin bonded particulate material (ChiraDex). Even if the amount of beta-cyclodextrin bound to the silica rod was only about half of the amount of beta-cyclodextrin bound to ChiraDex) particles, good resolutions were achieved for a set of chiral test components like Chromakalin, Prominal, Oxazepam, Methadone and some other drugs. By taking advantage of the unique features of the silica rods relating to their flat H/u (Van Deemter) curves, fast enantiomer separations could be demonstrated.

Chromatography↗
PubMed2004

Silica gel dessication of amniotic membrane with related epithelium cells for ocular surface reconstruction.

Cornea reparative regeneration when in various pathological states needs creating certain conditions to intensify the potential of regional stem cells mitotic activity. AIMS OF THE RESEARCH: To find out the degree of the epithelium AM preservation after preliminary processing and conservation by means of dehydration over silica gel with further sterilization; to study the effectiveness of clinical treatment of AM conserved in the surroundings with vital ability epithelium and AM dried over silica gel. MATERIALS AND METHODS: There was carried out an investigation of 18 samples of native amnion treated with antibiotics and 18 total surface amnion samples conserved by drying over silica gel and then sterilized by gamma rays. Clinical experiments were carried out on patients with severe chemical and thermal burns--18 people (21 eyes). After the burn trauma all the patients underwent the standard procedure of necrectomy, the covering of the eyeball with amniotic membrane dried over silica gel. CONCLUSION: The drying out of the amniotic membrane over silica gel on frames without being fixed on nitrocellulose paper makes the process of the amniotic membrane conservation simpler and makes it possible to preserve its unique biological qualities. The effectiveness of the regeneration of epithelium tissue of the eyeball surface with amniotic membrane dried over silica gel without the vital capacity cells of the epithelium layer is analogous to the regeneration of epithelium cells with amniotic membrane with vital capacity cells. With eye burns AM coverage hinders the formation of rough conjunctiva cicatrix, provides a favorable out-of-cell matrix substrate for epithelium migration and leads to quicker regeneration of one's own epithelium, makes further visual rehabilitation simpler.

Amnion↗
PubMed1989

Fourier transform infrared assay of membrane lipids immobilized to silica: leaching and stability of immobilized artificial membrane-bonded phases.

A nondestructive, sensitive assay to monitor the hydrocarbon content of silica-based chromatography particles has been developed. The assay requires a microscope accessory interfaced with a Fourier transform infrared (FTIR) spectrometer. For determining hydrocarbon content, undiluted alkyl-silica-bonded phases were pressed into a thin wafer. Hydrocarbon content was quantitated using the integrated hydrocarbon band intensity between 2995 and 2825 cm-1 [i.e., band area C-H] and the integrated silica oxide band intensity between 1945 and 1780 cm-1 [i.e., band area Si-O]. Plotting the [band area C-H]/[band area Si-O] ratio vs the carbon content determined by elemental analysis gave a correlation coefficient of r = 0.997. The FTIR assay was validated on 5-, 7-, and 12-microns silica particles using three different immobilized artificial membrane (IAM) silica-bonded phases. The utility of the FTIR assay in determining hydrocarbon content was demonstrated by evaluating hydrocarbon leaching from IAM phases exposed to mobile-phase solvents. The ability of organic solvents to leach hydrocarbon from IAM phases containing phosphatidylcholine (PC) as the immobilized ligand was chloroform greater than ethanol approximately methanol greater than ethyl acetate greater than methylene chloride greater than acetonitrile greater than acetone. Acetone and acetonitrile cause very little hydrocarbon leaching from HPLC-IAM.PC columns. When challenged with different mobile phases, IAM.PC columns perfused with mobile phase are more stable than IAM.PC-bonded phases stirred in mobile phases. IAM.PC contains lecithin linked to silica by amide bonds.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗
PubMed1986

Effects of silica on the composition of the pulmonary extracellular lining.

The effects of intratracheally injected silica on lung weights and on alveolar macrophages, polymorphonuclear leukocytes, phospholipid, protein, N-acetyl-beta-glucosaminidase, and alkaline phosphatase of the extracellular lining of rat lungs were studied as functions of dose and time. All of these parameters increased with time up to 12 days after a single injection of silica (200 mg/kg) and showed a dose dependence in their responses. Extracellular soluble protein increased 19.8-fold from 1.9 to 37.6 mg/pair of lungs. The composition of the extracellular soluble protein was very similar to that found in normal lungs as determined with two-dimensional-polyacrylamide gel electrophoresis. Although most of the soluble proteins in lavage effluents were similar to those found in serum, several serum proteins were absent, indicating that the selectivity of the lungs for certain serum proteins was maintained after treatment with silica. Increases in extracellular soluble proteins could not be accounted for by damage to the blood/air barrier. Extracellular phospholipid increased 12.1-fold from 1.74 to 21.1 mg/pair of lungs. The phosphatidylcholine content of this phospholipid resembled that of normal pulmonary surfactant but was different from that in free cells lavaged from the lungs of control and silica-treated rats. Increases in extracellular phospholipid were probably due to silica effects on the surfactant system and not to destruction of or release by free cells in the alveoli. N-Acetyl-beta-glucosaminidase and alkaline phosphatase increased approximately 33- and 6-fold, respectively, in response to silica. The number of alveolar macrophages and polymorphonuclear leukocytes increased 1.5- and 75-fold, respectively. Calculation of partial correlations revealed statistically significant relationships among extracellular phospholipids, soluble proteins, and the two hydrolytic enzymes, suggesting that these components were being released into the lung lining from a common source or by a common mechanism.

Acetylglucosaminidase↗
PubMed1992

Toxicity of silica-containing calcium phosphate glasses demonstrated in mice.

Suspensions of calcium phosphate glass containing various concentrations of silica (glass composition (moles): 100 Ca(PO3)2 to x SiO2,x = 0, 5, 10, 15 or 40) dispersed in normal saline were injected intraperitoneally into C57BL/6 mice to determine the mortality within 30 days. The mortality was 0/10, 3/10, 9/10, 10/10 and 10/10 at x = 0, 5, 10, 15 and 40 mol of silica, respectively. By means of inductively coupled plasma analysis, the amount of dissolved silica (Si4+) in water at 37 degrees C from the calcium phosphate glass depended on the amount of silica in the glasses. The mortality of mice was directly proportional to the silica content of the glass injected intraperitoneally. These results clearly show that the dissolved silica (Si4+) from the glass, monomeric or low molecular silicic anion, is highly toxic. The SiO2 component in biomaterials has toxic potential when dissolved in the body.

Animals↗
PubMed1994

Effects of silica on the outcome from experimental spinal cord injury: implication of macrophages in secondary tissue damage.

A model of spinal cord trauma in guinea-pigs, using lateral compression to a set thickness, produces a delayed functional loss at one to two days, followed by a partial recovery over several weeks, as measured using hindlimb motor behavior, vestibulospinal reflex testing, and mapping the receptive field of the cutaneous trunci muscle reflex. The role of inflammatory events in these secondary changes, was investigated with intraperitoneal injections of the macrophage toxin, silica. In one experiment, 11 matched pairs of animals were injured. One of each pair was selected randomly and injected with a suspension of 1.2 g of silica dust in sterile saline, immediately after injury and surgical closure. In a second experiment, involving 10 pairs of guinea-pigs, a similar dose of silica was administered to one of each pair at either one or two days before the injury. The animals survived up to three months, then were fixed by perfusion with glutaraldehyde. Histopathology of the lesion was quantified by line sampling of myelinated axons, and by measurement of blood vessels, in plastic sections through the center of the lesion. Surgery, injury, analysis of behavior and histology were all performed without knowledge of the experimental status of the animal. The secondary onset of functional loss below the lesion appeared to be delayed by one to two days in silica-treated animals with respect to controls. The number of myelinated axons at the center of the lesion, examined at two weeks to three months after injury was higher in the animals injected with silica immediately after surgery, most significantly in the dorsal quadrant of the cord. Myelin sheath thickness and axon caliber distribution were not different. Hypervascularity of the lesion was significantly reduced in animals injected with silica within one day of injury. These findings support the hypothesis that inflammatory activity plays an important role in secondary tissue damage, and that it may be responsible for some proportion of long-term neurological deficits, but do not suggest a prominent role for early macrophage activity in the mechanisms of demyelination.

Animals↗
PubMed2005

A method for the molecular imprinting of hemoglobin on silica surfaces using silanes.

A new molecular imprinting technique using covalently immobilized hemoglobin (Hb) is described for creating Hb-specific recognition cavities on silica. Two kinds of organic silane (3-aminopropyltrimethoxysilane: APTMS, and trimethoxypropylsilane: TMPS) were polymerized on a surface of porous silica after the Hb template was covalently immobilized by forming imine bonds, and their influence was analyzed. The results showed that not only the silane amount but also the relative proportions play an important role in protein imprinting. Pore size distribution on Hb imprinted silica was determined by nitrogen adsorption/desorption after removing the template Hb. The Hb-imprinted silica using covalently immobilized Hb (MIPi) as a template proved superior to silica using free Hb (MIPf) regarding displacement of template Hb, and selective re-adsorption as compared with other non-template proteins. The results suggested the capacity for selective adsorption of MIPi to be not only based on the isoelectric point (pI) and protein molecular weight, but also the characteristics of protein recognition cavities imprinted on base silica.

Adsorption↗
PubMed2004

Self-immobilization and/or thermal treatment for preparing silica-poly(methyloctylsiloxane) stationary phases.

Batches of poly(methyloctylsiloxane) (PMOS)-loaded silica were prepared by the deposition of PMOS, into the pores of HPLC silica. Portions of PMOS-loaded silica were allowed to remain at ambient temperature, without further treatment for 2, 9, 20, 31, 51, 105 and 184 days after preparation to undergo self-immobilization (irreversible adsorption of a layer of polymer on silica at ambient temperature in the absence of initiators). Other portions were subjected to a thermal treatment (100 degrees C for 4h) after 1, 2, 5, 7, 9, 15, 20, 25, 70, 111 and 184 days. Self-immobilized and thermally treated samples were characterized by % C, 29Si cross-polarization magic angle spinning (CP/MAS) NMR spectroscopy and reversed-phase column performance. The results show that thermal immobilization accelerates the distribution and rearrangement of the polymer on the silica surface. However, from the time that a monolayer has been formed by self-immobilization (approximately 100 days for PMOS on Kromasil silica), the thermal treatment does not alter this configuration and, thus, does not change the resulting chromatographic parameters.

Magnetic Resonance Spectroscopy↗
PubMed2005

Evaluation of capillary electrophoresis for determining the concentration of dissolved silica in geothermal brines.

The determination of silica concentrations in geothermal brines is widely recognized as a difficult analytical task due to its complex chemical polymerization kinetics that occurs during sample collection and chemical analysis. Capillary electrophoresis (CE) has been evaluated as a new reliable analytical method to measure silica (as silicates) in geothermal brines. Synthetic and geothermal brine samples were used to evaluate CE methodology. A capillary electrophoresis instrument, Quanta 4000 (Waters-Millipore) coupled with a Waters 820 workstation was used to carry out the experimental work. The separation of silicates was completed in approximately 5.5 min using a conventional fused-silica capillary (75 microm i.d. x 375 microm o.d. x 60 cm total length). A hydrostatic injection (10 cm for 20 s at 25 degrees C) was employed for introducing the samples. The carrier electrolyte consisted of 10 mM sodium chromate, 3 mM tetradecyltrimethyl-ammonium hydroxide (TTAOH), 2 mM sodium carbonate, and 1 mM sodium hydroxide, adjusted to a pH 11.0 +/- 0.1. Silicates were determined using an indirect UV detection at a wavelength of 254 nm with a mercury lamp and with a negative power supply (-15 kV). A good reproducibility in the migration times (%R.S.D. approximately 1.6%) based on six non-consecutive injections of synthetic brine solutions was obtained. A linear response between silica concentration and corrected peak area was observed. Ordinary (OLR) and weighted (WLR) linear regression models were used for calculating silica concentrations in all samples using the corresponding fitted calibration curves. The analytical results of CE were finally compared with the most probable values of synthetic reference standards of silica using the Student's t-test. No significant differences were found between them at P = 0.01. Similarly, the atomic absorption spectrometry (AAS) results were also compared with the most probable concentrations of the same reference standards, finding significant differences at P = 0.01.

Calibration↗
PubMed2006

Monolithic silica-based capillary column with strong chiral cation-exchange type surface modification for enantioselective non-aqueous capillary electrochromatography.

A silica-based monolithic stationary phase prepared by the sol-gel process in a 100 microm I.D. fused-silica (FS) capillary has been modified chemically with 3-mercaptopropyl trimethoxysilane followed by immobilization of a strong cation-exchange (SCX) type chiral selector, (S)-N-(4-allyloxy-3,5-dichlorobenzoyl)-2-amino-3,3-dimethylbutane phosphonic acid, by radical addition reaction onto the reactive sulfhydryl surface. After a fine-tuning of the mobile phase composition, the enantioselective capillary column was evaluated for the separation of various chiral basic drugs by enantioselective non-aqueous capillary electrochromatography (CEC), in comparison to capillary column analogs packed with 3.5 microm silica particles having attached the same selector. The performance of the monolithic silica column was further compared to corresponding polymethacrylate-based organic polymer monoliths. The study indicated that strong counter-ions such as 2-aminobutanol or N,N,N',N'-tetramethylethylenediamine are needed, although they reduce the electroosmotic flow velocity and separation factors in comparison to less efficient counter-ions, in order to allow the elution of the oppositely charged solutes in the ion-exchange retention mode within reasonable run time and as sharp zones. In contrast, weak counter-ions such as N,N-diisopropylethylamine (Huenig base) provided stronger electroosmotic flow and much better separation factors, but relatively poor peak efficiencies. Overall, with the chemically functionalized monolithic silica column the high quality separations of packed column analogs could be approximated, with regards to both separation factors and peak performances. On the other hand, the monolithic capillary column certainly outperformed the packed column in terms of system robustness under capillary electrochromatography conditions and showed excellent column longevity. The enantioselective strong cation-exchange-type monolithic silica column performed also well in comparison to the organic polymer monolith.

Cation Exchange Resins↗
PubMed2006

Effect of the cell type and cell density on the binding of living cells to a silica particle: an atomic force microscope study.

We used the atomic force microscope to study how the cell type and the density of cells adsorbed at a substrate can affect the adhesion between a living cell and a model drug delivery system (DDS) carrier nano-particle. We used three different anchorage-dependent cells, i.e., a living mouse fibroblast cell (L929), a living human colon cancer cell (Caco2), and a living mouse malignant melanoma cell (B16F10). For the DDS model nano-particle, we used a silica colloid. In order to correlate the adhesion force with the cell types, the growth curve of the cells were determined with a haemocytometer. The shapes of the cells at the different stages were monitored by light microscopy, and the morphology of their surfaces obtained by tapping mode atomic force microscopy. Force measurements showed that the Caco2 cell bound little to a silica particle, regardless of the cell density. The L929 cell bound well to a silica particle for low and high cell densities. The B16F10 cell bound little to a silica particle for low cell densities, but bound well for high cell densities. AFM images showed that the L929 cell did not contain folds. The B16F10 cells, however, displayed folds in the cell surface for low cell densities, but no folds in the cell for high cell densities. As literature also reported that the Caco2 cell contains folds, these results suggested that cells with folds showed less adhesion to a silica particle than cells without folds. The presence of folds in the cell presumably decreased the number of sites on the cell that could hydrogen bond or undergo van der Waals binding with the silanol groups of the silica particle.

Animals↗
PubMed2006

Colloidal crystallization of colloidal silica modified with ferrocenyl group-contained polymers in organic solvents.

Surface modification of colloidal silica with ferrocenyl-grafted polymer and colloidal crystallization of the particles in organic solvent were studied. Poly(methyl methacrylate-co-vinylferrocene)-grafted silica never formed colloidal crystals in polar solvent, such as acetone, acetonitrile, ethanol and N,N-dimethylformamide (DMF), while poly(methyl methacrylate-co-ferrocenyl acrylate)-grafted silica gave colloidal crystallization in DMF. The particles prepared by grafting of poly(N,N-dimethylacrylamide-co-vinylferrocene), with vinylferrocene (Vfc) mole fraction of 1/13 and 1/23, were observed to give the crystallization in ethanol and DMF over particle volume fraction of 0.058. Further, silica modified with copolymer of Vfc and N-vinyl-2-pyrrolidone, N-vinylcarbazole or N-isopropylacrylamide formed colloidal crystals in ethanol and DMF. Especially, poly(N-isopropylacrylamide-co-Vfc)-grafted silica, which was composed of the highest mole fraction of vinylferrocene, 1/3, afforded colloidal crystallization in ethanol over particle volume fraction of 0.053. Relatively high polar vinylferrocene copolymer grafting of silica resulted in colloidal polymerization in organic solvents.

Amides↗
PubMed2006

Synthesis of biocompatible hydrophobic silica-gelatin nano-hybrid by sol-gel process.

Silica-biopolymer hybrid has been synthesised using colloidal silica as the precursor for silica and gelatin as the biopolymer counterpart. The surface modification of the hybrid material has been done with methyltrimethoxysilane leading to the formation of biocompatible hydrophobic silica-gelatin hybrid. Here we are reporting hydrophobic silica-gelatin hybrid and coating precursor for the first time. The hybrid gel has been evaluated for chemical modification, thermal degradation, hydrophobicity, particle size, transparency under the UV-visible region and morphology. FTIR spectroscopy has been used to verify the presence of CH(3) groups which introduce hydrophobicity to the SiO2-MTMS-gelatin hybrids. The hydrophobic property has also been tailored by varying the concentration of methyltrimethoxysilane. Contact angle by Wilhelmy plate method of transparent hydrophobic silica-gelatin coatings has been found to be as high as approximately 95 degrees . Oxidation of the organic group which induces the hydrophobic character occurs at 530 degrees C which indicates that the surface hydrophobicity is retained up to that temperature. Optical transmittance of SiO2-MTMS-gelatin hybrid coatings on glass substrates has been found to be close to 100% which will enable the hybrid for possible optical applications and also for preparation of transparent biocompatible hydrophobic coatings on biological substrates such as leather.

Coated Materials, Biocompatible↗
PubMed2004

Signaling pathways controlling the production of inflammatory mediators in response to crystalline silica exposure: role of reactive oxygen/nitrogen species.

Occupational exposure to crystalline silica has been linked to pulmonary fibrosis and lung cancer. Surface properties of crystalline silica are critical to the production of oxidant species, chemokines, inflammatory cytokines, and proliferative factors involved in the initiation and progression of silica-induced damage, inflammation, alveolar type II cell hyperplasia, fibroblast activation, and disease. The transcription factors nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1) have been shown to play key roles in gene promotion for inflammatory mediators, oncogenes, and growth factors. This review summarizes evidence that in vitro and in vivo exposure to crystalline silica results in activation of NF-kappaB and AP-1. Signaling pathways for activation of these transcription factors are described. In addition, the role of silica-induced reactive oxygen species and nitric oxide in the activation of these signaling events is presented. Last, the generalizability of mechanisms regulating silica-induced pulmonary responses to pulmonary reactions to other occupational particles is discussed.

Animals↗