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PubMed2004

Effect of coal mine dust and clay extracts on the biological activity of the quartz surface.

Modification of the quartz surface by aluminium salts and metallic iron have been shown to reduce the biological activity of quartz. This study aimed to investigate the ability of water soluble extracts of coal mine dust (CMD), low aluminium clays (hectorite and montmorillonite) and high aluminium clays (attapulgite and kaolin) to inhibit the reactivity of the quartz surface. DQ12 induced significant haemolysis of sheep erythrocytes in vitro and inflammation in vivo as indicated by increases in the total cell numbers, neutrophil cell numbers, MIP-2 protein and albumin content of bronchoalveolar lavage (BAL) fluid. Treatment of DQ12 with CMD extract prevented both haemolysis and inflammation. Extracts of the high aluminium clays (kaolin and attapulgite) prevented inhibition of DQ12 induced haemolysis, and the kaolin extract inhibited quartz driven inflammation. DQ12 induced haemolysis by coal mine dust and kaolin extract could be prevented by pre-treatment of the extracts with a cation chellator. Extracts of the low aluminium clays (montmorillonite and hectorite) did not prevent DQ12 induced haemolysis, although the hectorite extract did prevent inflammation. These results suggest that CMD, and clays both low and rich in aluminium, all contain soluble components (possibly cations) capable of masking the reactivity of the quartz surface.

Administration, Inhalation↗
PubMed1994

Synthesis, characterization, and biological activity of a new potent class of anti-HIV agents, the peroxoniobium-substituted heteropolytungstates.

The mono- and trisubstituted peroxyniobium polyoxotungstates of formulas [(CH3)3NH]7[Si-(NbO2)3W9O37], Cs7[Si(NbO2)3W9O37], alpha-K5[Si(NbO2)W11O39] and alpha-[(CH3)3NH]5[Si(NbO2)-W11O39], have been prepared, purified, and characterized spectroscopically by 29Si NMR, 183W NMR, and IR. The presence of peroxo groups was verified by the yellow color of the product and quantified by iodometric titration. The potency of both the complexes and the precursor complexes was evaluated in human peripheral blood mononuclear cells (PBMC) acutely infected with human immunodeficiency virus type 1 (HIV-1). Hexaniobate (K7H[Nb6O19]) was the least effective with a median effective concentration (EC50) of > 100 microM, while Cs7[Si(NbO2)3W9O37] was one of the most effective compounds with an EC50 of 1.0 microM. None of the compounds were toxic to uninfected PBMC with the exception of alpha-K8[SiW11O39], which had a median inhibitory concentration (IC50) of 79 microM. The potency and selectivity of the complexes against HIV-1 reverse transcriptase was also evaluated and shown to be quite high (IC50 values from 0.03 to 0.06 microM). The trimethylammonium salts of the complexes were tested for their ability to inhibit the interaction between gp120 and CD4 using a cell-free system. The complex [(CH3)3NH]7[Si(NbO2)3W9O37] inhibited this interaction by 70% at 25 microM.

Antiviral Agents↗
PubMed1990

Determination of low-energy beta-emitter radionuclides deposited on surfaces by attapulgite treatment.

A method for the determination of surface contamination of various materials by 3H and 99Tc is reported. Both 3H and 99Tcm are widely used in chemical and clinical applications. The isotopes 99Tc, the decay product of 99Tcm, and 3H are soft beta-emitter radionuclides and the use of unsealed sources can frequently produce contamination and excessive internal dosing for workers. The removal of radionuclides from surfaces was effected with attapulgite, a clay with a high absorption capacity for many organic and inorganic substances. The determination was carried out by extracting the absorbed radionuclide from the clay and then measuring it in a beta-scintillation counter. The determination limits of the method, 20 Bq cm-2 for 3H and 100 Bq cm-2 for 99Tc, are below the "derived working limits" for these radionuclides.

Magnesium↗
PubMed2005

Extraction of selected heavy metals using modified clays.

In the present study, attapulgite, kaolinite, and montmorillonite KSF were modified using azeotropic distillation to condense 2-mercaptoethanol with the clay material. The resulting product was used as a coordinating agent to remove selected metal ions, e.g., copper(II), cadmium(II), silver(I), nickel(II), and lead(II) ions from standard aqueous solutions. Batch systems were used, and samples were shaken for two hours, and following filtration, metal content of the filtrate was measured by atomic absorption spectrometry. Without adjusting the pH, better than 90% of the metal ions could be removed.

Bentonite↗
PubMed2000

Characteristics of pharmaceutical grade phyllosilicate compacts.

The purpose of this paper was to determine the possible employment of three groups of phyllosilicates (two smectites, three palygorskites, and two sepiolites) as direct-compression tablet excipients. Compact lots of each material were obtained after application of three different compression loads and the elastic recoveries and tensile strengths of each lot were then determined. The results showed that, in comparison with laminar minerals (smectite samples), fibrous minerals (palygorskites and sepiolites) were found to have lower elastic recovery, regardless of the compression load. Almost all elastic recovery happened immediately after the ejection of the compacts. Then, and at least during the next 24 hr, smectite compacts maintained their dimensions without any significant variation, whereas fibrous compacts tended to continue increasing slightly their dimensions. On the other hand, compacts made with laminar particles had higher mechanical strength than those made with fibrous particles, except for one sepiolite sample in which the strength was similar. Both particle morphologies and the presence or absence of hydration water molecules were taken into account in order to explain these differences. According to the compact properties measured, at least two of the noncommercial samples (smectite from Gádor, Spain, and sepiolite from Vicálvaro, Spain) would be useful as direct-compression tablet excipients.

Chemistry, Pharmaceutical↗
PubMed2002

Measurements of LGS, LGN, and LGT thermal coefficients of expansion and density.

This paper will report on the measurements of the thermal coefficients of expansion and density of langasite (LGS), langanite (LGN), and langatate (LGT). The data were obtained by fabricating cubes with X, Y, and Z faces with nominal dimensions of 1 cm on a side for each material under test. The techniques used for measurement of density and thermal coefficients of expansion (TCE) of the materials are discussed. The data sets obtained and the extracted coefficients are presented.

Chemistry, Physical↗
PubMed2006

Differential adsorption of occluded and nonoccluded insect-pathogenic viruses to soil-forming minerals.

Soil represents the principal environmental reservoir of many insect-pathogenic viruses. We compared the adsorption and infectivity of one occluded and two nonoccluded viruses, Helicoverpa armigera single nucleopolyhedrovirus (HaSNPV) (Baculoviridae), Cricket paralysis virus (CrPV) (Dicistroviridae), and Invertebrate iridescent virus 6 (IIV-6) (Iridoviridae), respectively, in mixtures with a selection of soil-forming minerals. The relative infective titers of HaSNPV and CrPV were unchanged or slightly reduced in the presence of different minerals compared to their titers in the absence of the mineral. In contrast, the infective titer of IIV-6 varied according to the mineral being tested. In adsorption studies, over 98% of HaSNPV occlusion bodies were adsorbed by all the minerals, and a particularly high affinity was observed with ferric oxide, attapulgite, and kaolinite. In contrast, the adsorption of CrPV and IIV-6 differed markedly with mineral type, with low affinity to bentonites and high affinity to ferric oxide and kaolinite. We conclude that interactions between soil-forming minerals and insect viruses appear to be most important in nucleopolyhedroviruses, followed by invertebrate iridescent viruses, and least important in CrPV, which may reflect the ecology of these pathogens. Moreover, soils with a high content of iron oxides or kaolinite would likely represent highly effective reservoirs for insect-pathogenic viruses.

Adsorption↗
PubMed1978

Surface kinetic test method for determining rate of kill by an antimicrobial solid.

An antimicrobial-surface kinetic test which maximizes probability of cell-to-surface contact has been developed. The measurement of rate of kill by a nonleaching antimicrobial surface is based on the number of surviving bacterial cells at specific times of exposure to various amounts of total treated surface area of test substrate. This method gives information for direct comparison of rate of kill for a variety of antimicrobial surfaces in terms of rate of kill per square centimeter of surface area. Data obtained by this method can also give valuable dose response application information as an indication of the exponential efficiency of concentration in terms of treated surface area.

Bacteriological Techniques↗
PubMed1986

Interactions between clay minerals and siderophores affect the respiration of Histoplasma capsulatum.

The reduction in the respiration of Histoplasma capsulatum in broth culture caused by montmorillonite appeared to be the result, in part, of the interference by the clay with the iron nutrition of the fungus. This interference was apparently the result of the adsorption by the clay of the iron-transporting siderophore (deferricoprogen B) produced by the fungus, as the reduction in respiration was partially alleviated by the addition of foreign siderophores. Neither kaolinite nor attapulgite (palygorskite) appeared to adsorb significant amounts of the siderophores, probably because of the low cation exchange capacity and specific surface area of kaolinite and the inaccessibility of adsorption sites in the fibrous attapulgite. These observations, in addition to the adhesion of montmorillonite to the hyphae, suggest mechanisms that may explain the discrete geographic distribution of this fungus, which is pathogenic to humans and which has been isolated essentially only from soils that do not contain montmorillonite.

Adsorption↗
PubMed2003

Effect of surface roughness on flexural strength of veneer ceramics.

The strength of ceramic restorations depends on the occlusal surface roughness of the veneering porcelain, which is influenced by the final preparation. The hypothesis of the study was that roughnesses below a critical microscopic defect size--based only on fracture mechanics considerations--also affect flexural strength. The bending failure stress was evaluated on standard specimens of 4 veneer ceramics with 4 different surfaces of defined roughnesses, respectively. A linear correlation was found between roughness and failure stress. A "roughness-free" failure stress value was predicted for each tested material. This theoretical value can represent the "true" strength of the respective ceramic material. We conclude from our results that the final preparation of a ceramic restoration is critical to the strength of the material, and that ceramic veneering materials can be compared more objectively with respect to their strength by means of roughness-free strength values.

Air Abrasion, Dental↗
PubMed2003

[Effects of the adsorbent CAA for hemopurification on normal components of human plasma in removing methylene blue].

Virus inactivation of plasma can be achieved by phototreatment with methylene blue (MB). Subsequently, elimination of MB may reduce the adverse effects of MB. This study examined the effects of adsorbing MB with the use of cross-linked agar bead entrapped attapulgite clay (CAA) on normal ingredients in MB-treated plasma units. The biomedical characteristics of CAA were assessed by determination of partial biochemical indexes, coagulation potency and some cationic concentration in a control sample and the MB-treated plasma eluted from CAA column. The biochemistry indexes or K+, Na+ in plasma were almost unaltered before and after CAA adsorption. In contrast, the concentrations of CA2+ and Mg2+ increased and the blood ammonium decreased obviously. The activated partial thromboplastin time (APTT) was prolonged from 42 s to 53 s, and prothrombin time (PT) from 13 s to 14 s. The result indicates that CAA as an adsorbent for hemopurification retains the most important characters of human plasma. CAA can be useful for the elimination of MB in MB-treated plasma and does not bring on harmful alteration in clinical significance.

Adsorption↗
PubMed2002

[Study of unusual infrared transmittance spectrum of the KBr pellet with a large amount of alpha-SiC powders].

In the spectroscopic experiments, additionally large extinction caused by the scattering in the vicinity of inherent absorption peaks of the measured sample granules can lead to a deviation of measured absorption peak from the corresponding inherent one, then an incorrect spectrum appears. This is just the Christiansen effect that we must take cares to avoid as much as possible. One of the measures we take is to use a small amount of sample material (less than 2%) when we make the pellets, for example KBr is the matrix. In an experiment, when a large (not small as usual) amount of alpha-SiC powder is dispersed into KBr powder, the resulted pellet has an infrared transmission spectrum with a sharp peak at the position of 1,052.33 cm-1. We find that this new phenomenon is very interesting, and looks contrary to the usual Christiansen effect, but can be explained with Lorentz dispersion model accurately together, so we call it reverse-Christiansen effect. Exactly at this frequency, the refractive indices of these two materials are equal, and absorption coefficients are very small. Also, it is very useful for making a new type of band-pass filter or determining the refractive indices of some materials correctly, etc.

Absorption↗
PubMedDate not supplied

[The chemotactic properties of Bradyrhizobium japonicum in the presence of natural fine-grained minerals].

The natural argillaceous minerals montmorillonite and palygorskite were found to enhance the motility of Bradyrhizobium japonicum cells and to slow down their chemotactic motion to glucose. The latter effect of the minerals is probably due to the adsorption of mineral particles on the cell surface and the blockade of the receptors that are responsible for the chemotactic behavior of the bacterium.

Bentonite↗
PubMedDate not supplied

[The effects of several factors on the growth of pure and mixed cultures of Azotobacter chroococcum and Bacillus subtilis].

We studied the effect of a clay mineral, palygorskite, on the physiological activity of Azotobacter chroococcum and the phosphate-mobilizing bacterium Bacillus subtilis, as well as their mixed cultures, under various oxygen supply conditions during the utilization of phosphorus from readily and poorly soluble compounds (K2HPO4 x 3H2O) and (Ca3(PO4)2), respectively. During cultivation of the bacteria in a nutrient medium with Ca3(PO4)2, the number of microorganisms was higher than that observed in a medium with K2HPO4. An increase in oxygen mass transfer in the nutrient medium was followed by a rise in the number of Bacillus subtilis cells and an inhibition of Azotobacter chroococcum growth. An addition of palygorskite (5 g/l) into the nutrient medium stimulated the growth of both bacteria and stopped the decreasing growth of Azotobacter chroococcum at high values of oxygen mass transfer. The number of Bacillus and, particularly, Azotobacter cells was two to five times lower in a mixed culture than in a monoculture. These differences were less significant during the cultivation of mixed cultures in medium with palygorskite.

Azotobacter↗
PubMed1988

[Comparative study, with photoelectron spectroscopy of the adsorption of phospholipids by 3 fibrous silicate minerals (chrysotile, crocidolite, attapulgite)].

The method used in this study for preparing mineral samples has allowed us to obtain a highly reproducible surface state, which in turn means that we can better exploit the results of the XPS analysis. With high initial concentrations, the three minerals studied appeared to be covered with a bilayer of phospholipids. The greatest adsorption was obtained with initial phospholipid concentrations of 100, 150 and 300 micrograms/ml for crocidolite, chrysotile and attapulgite respectively. It would appear that these differences in surface reactivity can be related to the different levels of risk associated with the inhalation of these fibres.

1,2-Dipalmitoylphosphatidylcholine↗