Biogenic ferrihydrite-humin coprecipitate as an electron donor for the enhancement of microbial denitrification by Pseudomonas stutzeri

Nitrate pollution of groundwater has become an increasingly serious environmental problem that poses a great threat to aquatic ecosystems and to human health. Previous studies have shown that solid-phase humin (HM) can act as an additional electron donor to support microbial denitrification in the bioremediation of nitrate-contaminated groundwater where electron donor is deficient. However, the electron-donating capacities of HMs vary widely. In this study, we introduced ferrihydrite and prepared ferrihydrite-humin (Fh-HM) coprecipitates via biotic means to strengthen their electron-donating capacities. The spectroscopic results showed that the crystal phase of Fh did not change after coprecipitation with HM in the presence of Shewanella oneidensis MR-1, and iron may have complexed with the organic groups of HM. The Fh-HM coprecipitate prepared with an optimal initial Fh-HM mass ratio of 14:1 enhanced the microbial denitrification of Pseudomonas stutzeri with an electron-donating capacity 2.4-fold higher than that of HM alone, and the enhancement was not caused by greater bacterial growth. The alginate bead embedding assay indicated that the oxidation pathway of Fh-HM coprecipitate was mainly through direct contact between P. stutzeri and the coprecipitate. Further analyses suggested that quinone and organic-complexed Fe were the main electron-donating fractions of the coprecipitate. The results of the column experiments demonstrated that the column filled with Fh-HM-coated quartz sand exhibited a higher denitrification rate than the one filled with quartz sand, indicating its potential for practical applications.

Measuring and modeling the influence of salinity change on the transport behaviour of Escherichia coli through quartz sand

Pathogenic bacteria can be discharged in the environment through natural as well as anthropogenic activities. Once in the environment, they may contaminate soil and sediments and migrate towards water bodies. Transient chemical conditions may occur in soil/sediments and favor mobilization of bacteria, e.g., upon the reduction of salinity (or ionic strength). However, the magnitude of this phenomenon and its relationship with particle size is not well understood, yet. In this work, we investigated the transport of Escherichia coli under variable salinity conditions (between 1 and 20 part per thousand, ppt) and for different soil grain sizes (between 150 and 710 μm). A model developed in our group was applied in this work. It couples bacteria and salinity transport equations in order to account for transient water composition in the description of bacteria migration. The model was calibrated and validated with laboratory experiments. The tests were monitored continuously with UV-Vis spectroscopy, which allowed to record highly resolved concentration fronts. The results show that salinity increases the retardation of the bacteria. Upon salinity drop, a release of bacteria occurs forming a peak whose magnitude increases with salinity change. This effect becomes more important as the grain size decreases. Simulations suggest that the dominant retention mechanism is attachment for coarse sand and straining for fine sand. The retention can be reversed as the salinity is reduced causing a sudden bacteria mobilization. Such a behaviour may have important implications on microbial contamination of water bodies when soil/sediments undergo transient chemical conditions.

Molecular Driving Forces in Peptide Adsorption to Metal Oxide Surfaces

Molecular recognition between peptides and metal oxide surfaces is a fundamental process in biomineralization, self-assembly, and biocompatibility. Yet, the underlying driving forces and dominant mechanisms remain unclear, bringing obstacles to understand and control this process. To elucidate the mechanism of peptide/surface recognition, specifically the role of serine phosphorylation, we employed molecular dynamics simulation and metadynamics-enhanced sampling to study five artificial peptides, DDD, DSS, DpSpS, DpSpSGKK, and DpSKGpSK, interacting with two surfaces: rutile TiO₂ and quartz SiO₂. On both surfaces, we observe that phosphorylation increases the binding energy. However, the interfacial peptide conformation reveals a distinct binding mechanism on each surface. We also study the impact of peptide sequence to binding free energy and interfacial conformation on both surfaces, specifically the impact on the behavior of phosphorylated serine. Finally, the results are discussed in context of prior studies investigating the role of serine phosphorylation in peptide binding to silica.

Influence of enterococcal surface protein (esp) on the transport of Enterococcus faecium within saturated quartz sands

Enterococcus was selected by US EPA as a Gram-positive indicator microorganism for groundwater fecal contamination. It was recently reported that enterococcal surface protein (esp) was more prevalent in Enterococcus from human sources than in Enterococcus from nonhuman sources and esp could potentially be used as a source tracking tool for fecal contamination (Scott et al., 2005). In this research, we performed laboratory column transport experiments to investigate the transport of Enterococcus faecium within saturated quartz sands. Particularly, we used a wild type strain (E1162) and a mutant (E1162Δesp) to examine the influence of esp on the transport behavior of E. faecium. Our results showed that esp could significantly enhance the attachment of E. faecium cells onto the surface of silica sands and thus lower the mobility of E. faecium within sand packs. Cell surface properties (e.g., zeta potential) were determined and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was applied to explain the effects of esp on the retention of E. faecium. Overall, our results suggested that E. faecium strains with esp could display lower mobility within saturated sand packs than E. faecium strains without esp. The disparity in the transport behavior of E. faecium with and without esp could limit the effectiveness of esp as a source tracking tool within the groundwater system.

Hypolithic microbial community of quartz pavement in the high-altitude tundra of central Tibet

The hypolithic microbial community associated with quartz pavement at a high-altitude tundra location in central Tibet is described. A small-scale ecological survey indicated that 36% of quartz rocks were colonized. Community profiling using terminal restriction fragment length polymorphism revealed no significant difference in community structure among a number of colonized rocks. Real-time quantitative PCR and phylogenetic analysis of environmental phylotypes obtained from clone libraries were used to elucidate community structure across all domains. The hypolithon was dominated by cyanobacterial phylotypes (73%) with relatively low frequencies of other bacterial phylotypes, largely represented by the chloroflexi, actinobacteria, and bacteriodetes. Unidentified crenarchaeal phylotypes accounted for 4% of recoverable phylotypes, while algae, fungi, and mosses were indicated by a small fraction of recoverable phylotypes.

G-protein coupled receptor array technologies: site directed immobilisation of liposomes containing the H1-histamine or M2-muscarinic receptors

This paper describes a novel strategy to create a microarray of G-protein coupled receptors (GPCRs), an important group of membrane proteins both physiologically and pharmacologically. The H(1)-histamine receptor and the M(2)-muscarinic receptor were both used as model GPCRs in this study. The receptor proteins were embedded in liposomes created from the cellular membrane extracts of Spodoptera frugiperda (Sf9) insect cell culture line with its accompanying baculovirus protein insert used for overexpression of the receptors. Once captured onto a surface these liposomes provide a favourable lipidic environment for the integral membrane proteins. Site directed immobilisation of these liposomes was achieved by introduction of cholesterol-modified oligonucleotides (oligos). These oligo/cholesterol conjugates incorporate within the lipid bilayer and were captured by the complementary oligo strand exposed on the surface. Sequence specific immobilisation was demonstrated using a quartz crystal microbalance with dissipation (QCM-D). Confirmatory results were also obtained by monitoring fluorescent ligand binding to GPCRs captured on a spotted oligo microarray using Confocal Laser Scanning Microscopy and the Zepto-READER microarray imaging system. Sequence specific immobilisation of such biologically important membrane proteins could lead to the development of a heterogeneous self-sorting liposome array of GPCRs which would underpin a variety of future novel applications.

A Quantitative In Vitro Fluorescence Imaging Method for Phospholipid Loss from Respirable Mineral Particles

Respirable quartz and kaolin particles were treated with fluorescent-labeled phospholipids to model contact of fibrogenic and nonfibrogenic particles with pulmonary surfactant in the alveolar regions of the lung. Particles were used to challenge rat pulmonary macrophages in vitro at times from 1 d to 10 d. The objective was to develop a quantitative method to track surfactant components that adsorb to respirable particles in the lung or inside cells. Confocal laser scanning microscopy was used to image and quantify surfactant remaining on particles internalized by cells. Results indicate that the fluorescent label is removed from quartz particles quickly, with the fluorescence intensity less than 15% of initial value at 3 d, and about 5% at 10 d. In contrast, the kaolin particle-associated fluorescence was still approximately 39% of initial intensity at 3 d, and 10-15% at 10 d. Unchallenged cells showed a background of approximately 5%, and noninternalized particles did not exhibit any loss of fluorescence over the 10-d exposure. The results indicate the method may be useful in label-removal rate studies of respirable particles in vitro, with some cautions and limitations. Results are discussed and compared with similar studies using nonimaging techniques.

Kinetic Analysis of Heparin and Glucan Sulfates Binding to P-Selectin and Its Impact on the General Understanding of Selectin Inhibition

P-Selectin, expressed on activated endothelial cells and platelets, is a high kinetic adhesion receptor involved in leukocyte rolling of the inflammatory response, or in tumor cell binding in the course of metastasis. Thus, P-selectin inhibition is a promising therapeutic target. The anti-inflammatory and anti-metastatic activities of heparin have partly been related to the inhibition of P-selectin binding. Here we apply a quartz crystal microbalance (QCM) biosensor to determine the kinetic constants of heparin and other sulfated polysaccharides binding to immobilized P-selectin. Binding kinetics of the derivatives were correlated with their inhibitory capacity in a P-selectin cell rolling assay. Three commercial heparins differ in cell rolling inhibition and display slightly different affinities (KD 1.21 x 10(-6) M to 5.86 x 10(-7) M). Inhibitory capacity appears to be mainly driven by a slow off-rate from the receptor (2.27 x 10(-3) s-1 to 1.23 x 10(-3) s-1). To correlate the impact of binding kinetics on inhibitory capacity structurally, we analyzed six semisynthetic glucan sulfates. They display different degrees of sulfation (DS), which has a strong influence on inhibitory activity. Kinetic data illustrate that the inhibitory capacity correlates excellently with the off-rate of these polysaccharides (R = 0.99), while the association (on-rate) affects activity to a lesser extent. In general, the consideration of binding kinetics sheds new light on the mechanism of selectin inhibition. A much slower dissociation of the inhibitors from the receptor than the physiological ligands is key for inhibitory capacity. Structurally, highly charged compounds with a slow off-rate, such as heparin or glucan sulfates, appear as potent candidates for P-selectin inhibition.

Actin plays a crucial role in the phagocytosis and biological response to respirable quartz particles in macrophages

The uptake of respirable quartz particles by alveolar macrophages (AM) is believed to cause an inflammatory response, which is discussed as a crucial step in quartz pathogenicity. However, little is known about the mechanism and the relevance of particle uptake. Therefore, the aim of this study was to analyze the role of the actin cytoskeleton in quartz particle uptake, reactive oxygen species generation (ROS) and tumour necrosis factor alpha (TNF-alpha) release. Primary rat alveolar and interstitial macrophages (IM) as well as a rat alveolar macrophage cell line (NR8383) were treated with quartz particles at various concentrations and time intervals. Particle uptake was studied using flow cytometry and light/fluorescence microscopy to analyze particle uptake and cytoskeleton recruitment. Intra- as well as extracellular ROS generation was analyzed by flow cytometry and electron spin resonance (ESR). Flow cytometric investigations demonstrated a dose- and time-dependent particle uptake. Primary AM showed a similar uptake indicating that the cell line provides a good model to investigate the mechanisms of particle uptake while primary IM had a lower uptake rate. Inhibition of actin polymerization using cytochalasin-D caused a significant reduction of particle uptake in NR8383 cells. The quartz induced dose-dependent increase of ROS generation and TNF-alpha release was also blocked by inhibition of actin polymerization. Our results demonstrate an active involvement of the cytoskeleton in uptake of quartz particles and suggest a role of the actin framework and/or the particle uptake in DQ12-induced ROS generation and cytokine release.

In vitro toxicity evaluation of single walled carbon nanotubes on human A549 lung cells

This paper describes the in vitro cytotoxicity assessment of single walled carbon nanotubes (SWCNT) on A549 cells, a human lung cell line. Cellular viability was determined using the alamar blue (AB), neutral red (NR) and MTT assays, which evaluated metabolic, lysosomal and mitochondrial activity respectively. In addition, the total protein content of the cells was measured using the coomassie brilliant (CB) blue assay. Supernatants were also assayed for Adenylate Kinase (AK) release and Interleukin 8 (IL-8) which indicated a loss of cell membrane integrity and an inflammation response respectively. To investigate the interactions between serum components in the test medium and the test materials, exposures were conducted both in serum containing (5%) and serum-free medium. Results from the cytotoxicity tests (AB, CB, MTT) revealed the SWCNT to have very low acute toxicity to the A549 cells as all but one of the reported 24h EC(50) values exceeded the top concentration tested (800 microg/ml). The SWCNT were found to interfere with a number of the dyes used in the cytotoxicity assessment and we are currently conducting a comprehensive spectroscopic study to further investigate these interactions. Of the multiple cytotoxicity assays used, the AB assay was found to be the most sensitive and reproducible. Transmission electron microscopy (TEM) studies confirmed that there was no intracellular localization of SWCNT in A549 cells following 24h exposure; however, increased numbers of surfactant storing lamellar bodies were observed in exposed cells.

Another continental pool in the terrestrial silicon cycle

Silicon is the second most abundant element on Earth. It is an important nutrient for phytoplankton and is readily absorbed by terrestrial vegetation; it also assists the removal of carbon dioxide from the atmosphere through the weathering of silicates. But the continental cycle of silicon is not well known, and only a few studies have attempted to use silicon stable isotopes (28Si, 29Si and 30Si) to quantify the continental silicon reservoirs. Dissolved silicon in sea and river waters forms a reservoir of mean isotopic value +1.1 per thousand (refs 7, 10). It is enriched in 30Si with respect to the igneous rocks reservoir, which has a mean isotopic value of -0.3 per thousand (refs 4, 9). This enrichment can only be produced by a major fractionation during weathering, and should result in the formation of a continental 30Si-depleted reservoir. Such a reservoir, however, has not been identified to date. Here we analyse silicon isotopes of in situ quartz from a sandstone series in France, using a new-generation secondary ion mass spectrometry apparatus. We show that quartz that precipitates as siliceous cements forms a strongly 30Si-depleted reservoir with isotopic values down to -5.7 per thousand, a more negative value than any previously published for terrestrial samples. Our findings suggest that quartz re-precipitation plays an important role in the biogeochemical cycle of silicon.

Serum copper levels among quartz stone crushing workers: a cross sectional study

The present cross sectional study was carried out among 134 workers of quartz stone crushing units to assess the serum Cu activity among quartz stone workers without disease. Demographic and occupational details of the subjects were recorded on the predesigned proforma. Standard diagnostic criteria were used for diagnosing silicosis and tuberculosis. The pulmonary functions of the subjects were measured using Spirovit SP-10. The mean age for male was found to be 26.63 +/- 6.28 years while that for female was 21.93 +/- 4.29 years and for the whole group was 26.13 +/- 6.26 years. In the present study only one case of silicosis and seven cases of tuberculosis were found. The mean serum Cu levels of those having respiratory disease was found to be 91.5 +/- 19.8 microg/dl while mean serum Cu level of those free from respiratory disease was 86.8 +/- 21.3 microg/dl The difference was found to be statistically non-significant (t = 0.64, df= 1, P > 0.05). Thus, in the present study, though the elevated level of serum Cu was found in solitary case of silicosis, no association could be established between the silica exposure and serum copper levels as suggested by non-significant effect of duration of exposure (P = 0.53).

A novel nanolayer biosensor principle

A method for eliminating the mass transport limitation on biosensor surfaces is introduced. The measurement of macromolecular binding kinetics on plane surfaces is the key objective of many evanescent wave (e.g. total internal reflection fluorescence (TIRF)), and surface plasmon resonance (SPR) based biosensor systems, allowing the determination of binding constants within minutes or hours. However, these methods are limited in not being rigorously applicable to large macromolecules like proteins or DNA, since the on-rates are transport limited due to a Nernst diffusion layer of 5-10 microm thickness. Thus, for the binding of fibrinogen (340 kDa) to a surface current SPR biosensors will show a mass transport coefficient of ca. 2 x 10(-6) m/s. In a novel approach with an immiscible fluid vesicle (e.g. air bubble), it has been possible to generate nanoscopic fluid films of ca. 200 nm thickness on the sensor surface of an interfacial TIRF rheometer system. The thickness of the liquid film can be can be easily probed and measured by evanescent wave technology. This nanofilm technique increases the mass transport coefficient for fibrinogen to ca. 1 x 10(-4) m/s eliminating the mass transport limitation, making the binding rates reaction-rate limited. From the resulting exponential kinetic functions, lasting only 20-30s, the kinetic constants for the binding reaction can easily be extracted and the binding constants calculated. As a possible mechanism for the air bubble effect it is suggested that the aqueous fluid flow in the rheometer cell is separated by the air bubble below the level of the Nernst boundary layer into two independent laminar fluid flows of differing velocity: (i) a slow to stationary nanostream ca. 200 nm thick strongly adhering to the surface; and (ii) the bulk fluid streaming over it at a much higher rate in the wake of the air bubble. Surprising properties of the nanofluidic film are: (i) its long persistence for at least 30-60s after the air bubble has passed (2.5s); and (ii) the absence of solute depletion. It is suggested that a new liquid-liquid interface (i.e. a "vortex sheet") between the two fluid flows plays a decisive role, lending metastability to the nanofluidic film and replenishing its protein concentration via the vortices-thus upholding exponential binding kinetics. Finally, the system relaxes via turbulent reattachment of the two fluid flows to the original velocity profile. It is concluded that this technique opens a fundamentally novel approach to the construction of macromolecular biosensors.

Role of substrate on larval development of the freshwater teleostPelvicachromis pulcher

It is known that, in an aquatic environment, the mineralogical composition of the substrate can affect the structure of settled communities. In marine environments, the presence of quartz negatively influences the formation of biofilm, as well as the selection and the colonization of the substrate by benthic organisms. Direct laboratory observation revealed that the freshwater teleost Pelivicachromis pulcher selects, when available, nonquartzitic brooding substrate. To monitor the effects of substrate on larvae development, ten lots of embryos were distributed in grid nurseries; carbonatic gravel was laid in five of the nurseries, while freshly fractured quartz gravel was used in the remaining ones. All the embryos laid in the two nurseries hatched, and 90% of the carbonate developing larvae reached adulthood, while 100% of those reared on quartz grain died 120 hr post hatching. Examination was made, both in larvae developed on carbonatic substrates and in those developed on quartz substrates, of the expression of the fetal growth factor, the insulin growth factor-II (IGF-II), of the molecular chaperone, the heat shock protein 70 (HSP70), which is involved in the folding of the nascent polypeptide chain, of the key enzyme of the glycolytic pathway, the glyceraldehyde-3-phosphate dehydrogenase (GADPH), and of the housekeeping gene, the beta-actin. All the data were normalized against 18S RNA expression. In larvae reared on quartz substrate, the genes IGF-II and the beta-actin showed a lower expression, while the GADPH was totally suppressed and the expression of HSP70 increased. In conclusion, the data presented in this article demonstrated, for the first time, that the presence of quarzitic substrates is sufficient to stop larvae development through the inhibition of gene transcription in this African cichlid, leading to its death.

Release of the self-quenching of fluorescence near silver metallic surfaces

Fluorescein is one of the most widely used fluorescent probes in microscopy, biotechnology, and clinical assays. One difficulty with fluorescein is its self-quenching, which results in decreased intensities with increasing labeling density. In this study we examined human serum albumin (HSA), which contained one to nine covalently linked fluorescein molecules per molecule of HSA. The occurrence of homo resonance energy transfer for labeling ratios greater than 1 were confirmed by decreases in the relative quantum yields, anisotropies, and lifetimes. We found that most of the self-quenching can be partially eliminated by proximity of the labeled protein to metallic silver particles. These results suggest the use of heavily labeled proteins and metallic colloids to obtain ultrabright reagents for use in immunoassays, imaging, and other applications.

Adaptive correction of depth-induced aberrations in multiphoton scanning microscopy using a deformable mirror

We demonstrate adaptive aberration correction for depth-induced spherical aberration in a multiphoton scanning microscope with a micromachined deformable mirror. Correction was made using a genetic learning algorithm with two-photon fluorescence intensity feedback to determine the desired shape for an adaptive mirror. For a 40x/0.6 NA long working distance objective, the axial scanning range was increased from 150 mm to 600 mm.

A novel piezoelectric biosensor for the detection of phytohormone beta-indole acetic acid

A novel piezoelectric immunosensor has been developed for the determination of beta-indole acetic acid (IAA) in dilute solutions. The detection is based on competitive immunoreaction between a hapten (IAA) and an antigen (IAA-BSA, hapten-protein conjugation) bound to an anti-IAA antibody, immobilized on a quartz crystal microbalance (QCM). The frequency change (y) of the sensor caused by antigen is linearly related to the logarithm of the concentration of IAA (x) in the range of 0.5 ng/ml - 5 microg/ml with a regression equation of the form y = -23x + 151 (r = 0.9937).

Role of the scavenger receptor MARCO in alveolar macrophage binding of unopsonized environmental particles

Alveolar macrophages (AMs) avidly bind and ingest unopsonized environmental particles and bacteria through scavenger-type receptors (SRs). AMs from mice with a genetic deletion of the major macrophage SR (types AI and AII; SR-/-) showed no decrease in particle binding compared with SR+/+ mice, suggesting that other SRs are involved. To identify these receptors, we generated a monoclonal antibody (mAb), PAL-1, that inhibits hamster AM binding of unopsonized particles (TiO2, Fe2O3, and latex beads; 66 +/- 5, 77 +/- 2, and 85 +/- 2% inhibition, respectively, measured by flow cytometry). This antibody identifies a protein of approximately 70 kD on the AM surface (immunoprecipitation) that is expressed by AMs and other macrophages in situ. A cDNA clone encoding the mAb PAL-1-reactive protein isolated by means of COS cell expression was found to be 84 and 77% homologous to mouse and human scavenger receptor MARCO mRNA, respectively. Transfection of COS cells with MARCO cDNA conferred mAb-inhibitable TiO2 binding. Hamster MARCO also mediates AM binding of unopsonized bacteria (67 +/- 5 and 47 +/- 4% inhibition of Escherichia coli and Staphylococcus aureus binding by mAb PAL-1). A polyclonal antibody to human MARCO identified the expected approximately 70-kD band on Western blots of lysates of normal bronchoalveolar lavage (BAL) cells (>90% AMs) and showed strong immunolabeling of human AMs in BAL cytocentrifuge preparations and within lung tissue specimens. In normal mouse AMs, the anti-MARCO mAb ED31 also showed immunoreactivity and inhibited binding of unopsonized particles (e.g., TiO2 approximately 40%) and bacteria. The novel function of binding unopsonized environmental dusts and pathogens suggests an important role for MARCO in the lungs' response to inhaled particles.

A neutron reflectivity study of polymer-modified phospholipid monolayers at the solid-solution interface: polyethylene glycol-lipids on silane-modified substrates

The structure of polymer-decorated phospholipid monolayers at the solid-solution interface was investigated using neutron reflectometry. The monolayers were composed of distearoylphosphatidylethanolamine (DSPE) matrixed with varying amounts of DSPE-PEG (DSPE with polyethylene glycol covalently grafted to its headgroup). Mixed lipid monolayers were Langmuir-Blodgett deposited onto hydrophobic quartz or silicon substrates, previously hydrophobized by chemically grafting a robust monolayer of octadecyltrichlorosilane (OTS). We show that this method results in homogeneous and continuous phospholipid monolayers on the silanated substrates and determine that the grafted PEG chains extend away from the monolayers into the solvent phase as a function of their density, as expected from scaling theories. In addition, ligands were coupled to the end of the PEG chains and selective binding was demonstrated using fluorescence microscopy. Our results demonstrate that these constructs are ideal for further characterization and studies with well-defined monomolecular films.

Lung epithelial cell (A549) interaction with unopsonized environmental particulates: quantitation of particle-specific binding and IL-8 production

The A549 cell line was used to model in vitro the interaction of alveolar epithelium with environmental particulates. Confocal and electron microscopy demonstrated A549 binding and internalization of titanium dioxide (TiO2), iron oxide (Fe2O3), concentrated ambient air particulates (CAPs), and the fibrogenic particle alpha-quartz. Flow cytometry allowed quantitation of particle binding by measuring increased right angle light scatter (RAS) (TiO2) [40 micrograms/mL], Fe2O3 [100 micrograms/mL], alpha-quartz [200 micrograms/mL], or CAPs [40 micrograms/mL] fold increase RAS: 8.1 +/- 0.9, 4.3 +/- 0.4, 2 +/- 0.1, 1.6 +/- 0.1, respectively). With this quantitative assay, binding of particle was found to be calcium-dependent for TiO2 and Fe2O3 (% inhibition, 61.0 +/- 1.9, 40.0 +/- 5.6, respectively), while alpha-quartz binding was calcium-independent. A panel of polyanionic ligands known to inhibit scavenger-type receptors was used to identify binding mechanisms for environmental particulates. Both heparin and polyinosinic acid (polyI), but not the control polyanion chondroitin sulfate, caused marked inhibition of particulate binding by A549 cells (e.g., TiO2 [40 micrograms/mL] binding; polyI, heparin, and chondroitin sulfate: 73.8 +/- 3.5, 75.5 +/- 6.0, 7.5 +/- 6.7% inhibition, respectively; mean +/- SE, n > or = 4), indicating that scavenger receptor(s), albeit those distinct from the heparin-insensitive acetylated-LDL receptor, mediate particulate binding. The particulates ability to stimulate interleukin (IL-8) production in A549 cells was also tested. alpha-quartz, but not TiO2 or CAPs, caused a dose-dependent production of IL-8 (range 1-6 ng/mL), demonstrating a particle-specific spectrum of epithelial cell cytokine (IL-8) response. The results suggest that lung epithelial cell interaction with environmental particles is mediated by distinct receptors and can lead to particle dependent cytokine responses.

Dynamic changes of constituents in bronchoalveolar lavage fluid in experimental silicotic rats

Bronchoalveolar lavage (BAL) is a useful and safe method for sampling cellular and biochemical components from the lung. Analysis of bronchoaveolar lavage fluid (BALF) constituents is useful for defining the stage of disease, and for assessing disease progression and the response to therapy in lung disorders. We studied the dynamic changes in various indices for BALF and the accompanying silicotic changes in the lungs of rats at different times after quartz instillation. Total cell counts, LDH activity, protein concentration, and lipoperoxide (LPO) in the BALF of experimental silicotic rats were significantly higher than those of control rats (P < 0.05 or 0.01). After instillation, quartz content, total cell counts, LDH activity and protein concentration in BALF tended to decrease over time. These findings suggested that in acute silicosis, quartz can induce serious inflammation and damage the lung, with acute lung proteinosis seen as the main change in this stage.

Lung macrophage uptake of unopsonized environmental particulates. Role of scavenger-type receptors

The receptors responsible for avid alveolar macrophage (AM) phagocytosis of unopsonized environmental particulates have not been well defined. This study used flow cytometry to quantitate the effects of a panel of soluble ligands for macrophage adhesion receptors on AM binding of unopsonized environmental dusts (titanium dioxide, TiO2; iron oxide, Fe2O3; alpha-quartz, SiO2; diesel engine exhaust dust) or fluorescent latex beads. Polyanionic ligands of the macrophage scavenger receptor (SR) for acetylated-LDL caused marked inhibition of AM binding of the oxide particles and latex beads (e.g., TiO2 binding; polyinosinic acid (polyl), 10 micrograms/ml: 70.2 +/- 1.5% inhibition, mean +/- SE, n = 11). In contrast, no inhibition was seen with the polyanions heparin and chondroitin sulfate (chond-S), or dextran, consistent with the known inhibitor profile of macrophage SRs for acetylated-LDL AM uptake of latex or SiO2 beads instilled into lungs of hamsters was inhibited by administration of polyl but not chondroitin sulfate (AM beads per cell: control, 6.1 +/- 0.7; polyl, 3.5 +/- 0.2; chond-S, 5.1 +/- 0.7, n > or = 4, p < 0.05 for control vs polyl) indicating macrophages SRs operate in vivo as well as in vitro. In contrast, AM binding of the carbonaceous diesel dust particles was not inhibited by any ligand tested. AM uptake of unopsonized TiO2, SR ligands or acetylated LDL caused no significant activation of AM respiratory burst or TNF production, consistent with past observations that opsonin-independent phagocytosis of inert particles by normal AMs is not accompanied by pro-inflammatory activation. These data implicate macrophage-type SRs in AM binding of charged environmental particles and indicate that distinct mechanisms mediate binding of carbonaceous dusts.

Flow cytometric assay of lung macrophage uptake of environmental particulates

We sought to establish a quantitative method using flow cytometry to study uptake of environmental particulates by alveolar macrophages (AMs). We used right angle light scatter (RAS) to measure uptake of titanium dioxide, quartz, and diesel particulates. After incubation with TiO2 in vitro, AMs showed dose-dependent increases in both cell-associated particles visualized by microscopy and RAS measured by flow cytometry (e.g., fold increase RAS at 4, 8, 16, 32, and 80 micrograms/ml, respectively, = 2 +/- 0.1, 4.0 +/- 0.5, 5.5 +/- 0.5, 9.1 +/- 2.5, 14.3 +/- 0.9; mean +/- SEM). Similar results were obtained with quartz and diesel particles. A strong correlation was observed between particle load per cell and AM RAS after uptake of fluorescent latex beads or fluorescent TiO2 (coated with BODIPY-BSA) (R2 = 0.984, 0.997, respectively). Using this technique, we found AM uptake of environmental particulates to be substantially greater than that of a panel of myelomonocytic and epithelial cell lines, consistent with their physiologic role in pulmonary defenses. RAS measurements have also identified both calcium-dependent and calcium-independent components in AM interactions with inert particles. Although this technique does not allow precise quantitation of particle number or mass per cell, flow cytometric analysis of relative increases in RAS is a useful tool to study AM interactions with a variety of environmental particulates.

The enzymatic removal of a surfactant coating from quartz and kaolin by P388D1 cells

The macrophage-like cell line, P388D1, was exposed to dipalmitoyl lecithin (DPL)-coated respirable quartz and kaolin, and the disappearance of the DPL was monitored for up to 9 days. The coating was removed rapidly at first (about 50% in the first 3 days) and then more slowly over the remaining 6 days, until about 30% remained on day 9. The rate of DPL digestion was independent of the type of dust and the amount of coated dust within the cell, indicating the existence of an extracellular phospholipase activity. This extracellular phospholipase activity was partially characterized. It was sensitive to temperatures above 56 degrees C, the presence of EDTA, the action of the proteases trypsin and proteinase K, and pH, being active at pH 7 but not at pH 5. This is consistent with reports in the literature of the existence of an extralysosomal phospholipase which is active at pH 7 and dependent on the presence of divalent metal ions. There was a dust-dependent difference in the extracellular rate of DPL digestion from quartz and kaolin. The coating was removed more slowly from the kaolin than it was from quartz. The removal of the DPL coating seen in the presence of cells was presumably due to both an intracellular and an extracellular phospholipase.

Effects of a protein kinase C inhibitor, Ro 31-7549, on the activation of human leukocytes by particulate stimuli

1. A new specific protein kinase C (PKC) inhibitor, Ro 31-7549, was used to explore the mechanisms by which particulate stimuli, quartz and chrysotile, stimulate human polymorphonuclear leukocytes (PMNL) to produce reactive oxygen metabolites (ROM). Also soluble stimuli, formyl-Methionyl-Leucyl-Phenylalanine (fMLP) and phorbol myristate acetate (PMA) were used. 2. Ro 31-7549 inhibited chrysotile-induced free intracellular calcium ([Ca2+]i) elevations but did not have an effect on quartz-induced elevations of [Ca2+]i. Both quartz and chrysotile induced production of ROM were partially inhibited by Ro 31-7549. fMLP-induced elevation of [Ca2+]i was inhibited by Ro 31-7549 whereas PMA did not affect [Ca2+]i. Ro 31-7549 strongly inhibited fMLP-induced ROM production, and completely abolished that induced by PMA. 3. These result suggest that PKC may have an important role in the activation of PMNL to produce ROM by particulate and soluble stimuli. However, the inhibition of chrysotile-, but not of quartz-induced [Ca2+]i elevations by Ro 31-7549 provides evidence that both PKC-dependent and -independent mechanisms may play a role in the activation of human leukocytes to produce ROM.

Influence of aluminum treatments on pulmonary retention of quartz in sheep silicosis

Previous experiments with the sheep model of silicosis have demonstrated a reduction of the pathological activity of quartz after treatments with aluminum lactate (Al-lac), such as Al-lac pretreatment of intratracheally injected quartz or Al-lac inhalation of quartz-exposed animals. Preliminary data also suggested a more effective alveolar clearance of quartz treated with Al-lac. The present study was undertaken to fully document the effect of Al-lac treatments on the pulmonary retention of quartz. Sheep (on average, 27 per group) received a single injection in the tracheal lobe of either 100 mg/100 mL of alpha-quartz, 100 mg/100 mL of alpha-quartz followed by Al-lac inhalations at 1-month intervals, or 100 mg/100 mL of alpha-quartz Al-lac pretreated in vitro. Samples of lung parenchyma were analyzed at 2, 6, and 10 months after the injection. The quartz concentration in each sample was measured using the X-ray diffraction method. The concentrations were expressed in micrograms of quartz per milligram of dry lung parenchyma. The geometric mean concentrations in each of the three groups at 2 months were statistically different (ANOVA of the log values; p = .016) as well as at 6 months (ANOVA of the log values; p = .001). Al-lac clearly reduced the pulmonary retention of quartz. Both modalities of Al delivery were equally effective in clearing quartz up to 2 months, which may explain the documented reduction in pathological activities after in both forms of therapy. However, quartz soaked in Al-Lac solution was more effective than inhalation of Al-lac after quartz exposure. The half-life of both native quartz and quartz Al-lactate inhaled was 5.05 and 4.99 months, respectively, while it was 3.1 months for Al-treated quartz. Al-lac inhalations after the second month of exposure do not significantly affect the rate of clearance of deposited quartz.

Effect of quartz and alumina dust on generation of superoxide radicals and hydrogen peroxide by alveolar macrophages, granulocytes, and monocytes

Phagocytosis of quartz particles by rabbit alveolar macrophages and monocytes and human granulocytes and monocytes was accompanied by stimulation of substrate free reduction of nitroblue tetrazolium to formazan. This reflects activation of an oxygen dependent bactericidal system of phagocytes and total (exogenic and endogenic) generation of active oxygen species. Low fibrogenic and cytotoxic alumina dust tended to increase formazan production by comparison with quartz dust. During phagocytosis of quartz dust by alveolar macrophages and monocytes there was no exogenic generation of superoxide radicals and hydrogen peroxide by these cells. By contrast, incubation of human granulocytes with quartz dust caused a significant increase in exogenic generation of superoxide radicals and hydrogen peroxide. Under such conditions, low fibrogenic alumina dust had no effect on hydrogen peroxide generation and substantially decreased the level of superoxide radical generation by human granulocytes. During incubation of rabbit granulocytes with quartz dust, an increase in the level of superoxide radical generation was also detected. It is considered that the differences between alveolar macrophages and granulocytes in their response to quartz dust are important from a physiological point of view. Alveolar macrophages are permanently present in pulmonary alveolae in large quantities; therefore their uncontrolled generation of superoxide radicals and hydrogen peroxide might immediately cause damage to pulmonary parenchyma. At the same time, destruction products from alveolar macrophages that died during phagocytosis of quartz particles contain a factor attracting granulocytes. Presence of a significant number of granulocytes in bronchopulmonary lavage fluid in cases of silicosis indicates development of a pathological process. This agrees well with the data obtained on exogenic generation of superoxide radicals and hydrogen peroxide by granulocytes, and on stimulation of this process due to phagocytosis of the quartz dust.

Micropatterned substratum adhesiveness: a model for morphogenetic cues controlling cell behavior

It is generally considered that tracks of cell adhesiveness are important in controlling cell migration during the development and regeneration of many tissues. In order to investigate this experimentally, a number of techniques have in the past been employed to make patterns of differential adhesiveness for in vitro studies. However, practical limitations on patterning resolution and the introduction of residual topography to the experimental substrata have restricted their usefulness. Here we describe a simplified photolithographic technique for patterning cell adhesiveness which allows a high degree of flexibility and precision. We have quantified, using adhesion and spreading characteristics of BHK cells, the differential adhesiveness that can be created on patterned surfaces, how this alters with the duration of exposure to serum proteins, and how this, in turn, relates to the persistence of cell patterning despite increases in cell density. We believe that this technique will prove extremely useful for the detailed in vitro examination of the mechanisms controlling cell behavior as it offers a degree of precision and ease of fabrication that has previously been unavailable.

Silicotic lesions of the bone marrow: histopathology and microanalysis

Silica deposition and characteristic nodular silicotic lesions of the bone marrow, virtually unknown features of silicosis, are described in a case of severe lung silicosis with silicotic granulomas of the liver and spleen. Scanning electron microscopy and X-ray microanalysis confirmed the presence of quartz and feld-spars. The bone marrow lesions included inconspicuous accumulations of silica-containing macrophages, free silica, slight lymphocyte and plasma cell infiltration, and reticulin fibre formation; and development of slightly larger partly fibrous silicotic nodules, comparable to those of the lung, liver, and spleen. Silicosis must therefore be considered in the differential diagnosis of bone marrow granulomas.

Effectiveness of animal rotation in achieving uniform dust exposures and lung dust deposition in horizontal flow chambers

An important source of variability of experimental results in inhalation toxicology originates from the nonuniformity of chamber concentrations. Two horizontal flow inhalation chambers were used in evaluating the effect of cage rotation within each chamber on the amount of alpha-quartz deposited in the lungs of male Fischer 344 rats. The alpha-quartz lung burden was determined by quantitative X-ray diffraction. A carefully designed animal rotation schedule significantly reduced the variability in the amount of alpha-quartz deposited in the animals, thereby minimizing effects of chamber nonuniformity due either to design or dust generator characteristics.

Reactions in glass ionomer cements: II. An infrared spectroscopic study

The transmission and attentuated total reflectance spectra of a dental cement formed from an aluminosilicate glass and aqueous polyacrylic acid (ASPA) are reported. Interpretation of spectra show that a siliceous hydrogel is formed together with the polyacrylate salts of calcium and aluminum. In the fully hardened cement a minor proportion of -COOH remains unconverted to — COO- groups for steric reasons.