Jesús Merino

Adsorption of monovalent organic cations on sepiolite; experimental results and model calculations

Adsorption of neutral organic molecules and the monovalent organic cations methylene blue (MB) and crystal violet (CV) to sepiolite was determined experimentally and investigated by an adsorption model. The largest amounts of MB and CV adsorbed were about 4-fold of the cation exchange capacity (CEC) of sepiolite. Consequently, it was proposed that most of the above described adsorption was to neutral sites of the clay. The adsorption model considered combines the Gouy-Chapman solution and specific binding in a closed system. The model was extended by allowing cation adsorption to neutral sites of the clay, in addition to adsorption to negatively charged sites and adsorption to neutral complexes formed from 1 cation adsorbed to a negative surface site. The amount of available neutral sites was determined from the adsorption of the neutral molecule Triton-X 100 (TX100). The model could adequately simulate the adsorption of the neutral molecules TX100 and crown ether 15-crown-5 (15C5) as well as the organic cations. Due to aggregation of MB molecules in solution, their adsorption was somewhat less than that of CV at the larger added concentrations. A consideration of the molecular dimensions of TX100, MB and CV suggested that their adsorption was mostly to external sites of the clay and that their entry to the sepiolite channels was largely excluded. This interpretation is supported by infrared spectroscopy (IR) measurements, which show large perturbations of the peak corresponding to vibrations of external Si-OH groups of the clay and confirm complete occupancy of external sites by MB and CV.

Inhibition of B cell death causes the development of an IgA nephropathy in (New Zealand white x C57BL/6)F(1)-bcl-2 transgenic mice.

Little is known about the pathogenic mechanisms of IgA nephropathy, despite being the most prevalent form of glomerulonephritis in humans. We report in this study that in (New Zealand White (NZW) × C57BL/6)F1 mice predisposed to autoimmune diseases, the expression of a human bcl-2 (hbcl-2) transgene in B cells promotes a CD4-dependent lupus-like syndrome characterized by IgG and IgA hypergammaglobulinemia, autoantibody production, and the development of a fatal glomerulonephritis. Histopathological analysis of glomerular lesions reveals that the glomerulonephritis observed in these animals resembles that of human IgA nephropathy. The overexpression of Bcl-2 in B cells selectively enhances systemic IgA immune responses to T-dependent Ags. Significantly, serum IgA purified from (NZW × C57BL/6)F1-hbcl-2 transgenic mice, but not from nontransgenic littermates, shows reduced levels of galactosylation and sialylation and an increased ability to deposit in the glomeruli, as observed in human patients with IgA nephropathy. Our results indicate that defects in the regulation of B lymphocyte survival associated with aberrant IgA glycosylation may be critically involved in the pathogenesis of IgA nephropathy, and that (NZW × C57BL/6)F1-hbcl-2 Tg mice provide a new experimental model for this form of glomerulonephritis.

Sepiolite-based materials for the photo- and thermal-stabilization of pesticides

The present work is related to the use of sepiolite for the stabilization of certain photo or thermolabile herbicides by their adsorption on sepiolite-modified materials that act as organo-inorganic supports of the pesticides. The study demonstrates that formulations based on sepiolite containing a cationic dye (thioflavine-T (TFT)) are very effective in the stabilization of a photolabile herbicide (trifluralin (TF)). A modification of the hydrophilic character of the sepiolite surface by adsorption of cationic surfactants enhances the adsorption on the mineral substrate of non-polar pesticides, such as the herbicides alachlor (ACH) or metolachlor (MCH), thus contributing to the decrease of their losses by volatilization.

Exacerbation of type II collagen–induced arthritis in apolipoprotein E–deficient mice in association with the expansion of Th1 and Th17 cells

OBJECTIVE To explore the bidirectional relationship between the development of rheumatoid arthritis (RA) and atherosclerosis using bovine type II collagen (CII)-immunized B10.RIII apoE(-/-) mice, a murine model of spontaneous atherosclerosis and collagen-induced arthritis (CIA). METHODS Male B10.RIII apoE(-/-) mice and wild-type controls were immunized with 150 μg of CII emulsified in Freunds complete adjuvant (CFA). The clinical, radiologic, and histopathologic severity of CIA, the levels of circulating IgG1 and IgG2a anti-CII antibodies, the expression of proinflammatory and antiinflammatory cytokines in the joints, and the percentages of Th1, Th17, and Treg lymphocytes in the draining lymph nodes were evaluated during CIA induction. In addition, the size of atherosclerotic lesions was assessed in these mice 8 weeks after CIA induction. RESULTS B10.RIII apoE(-/-) mice that were immunized with CII and CFA developed an exacerbated CIA that was accompanied by increased joint expression of multiple proinflammatory cytokines and by the expansion in the draining lymph nodes of Th1 and Th17 cells. In contrast, the size of vascular lesions in B10.RIII apoE(-/-) mice was not affected by the development of CIA. CONCLUSION Our findings indicate that a deficiency in apolipoprotein E and/or its consequences in cholesterol metabolism act as accelerating factors in autoimmunity by promoting Th1 and Th17 inflammatory responses.

Synthesis of pillared clays assisted by microwaves

Abstract Microwave (MW) irradiation was used to synthesize aluminum-pillared clays (MW-Al-PILCs) by replacing the conventional calcination of Al-PILCs precursors (pre-Al-PILCs). X-ray diffraction (XRD) patterns and nitrogen adsorption/desorption isotherms showed that the MW-irradiated pre-Al-PILCs gave a series of MW-Al-PILC materials exhibiting some characteristics comparable to Al-PILCs obtained by conventional heating. However, differential thermal analysis (DTA), thermogravimetric analysis (TGA), impedance spectroscopy, 27 Al MAS NMR, and intercalative adsorption of methylene blue (MB), indicated that the MW-Al-PILC samples were intermediate between Al-pre-PILCs and conventional Al-PILCs. The 27 Al MAS NMR spectra showed that in MW-Al-PILCs obtained after 18 min of MW irradiation, the Al IV /Al VI ratio was 1/9, which is comparable to that in Al-pre-PILCs (8% Al IV ; 92% Al VI ) and significantly different from the typical values of conventional Al-PILCs (23% Al IV ; 77% Al VI ). It is assumed that the MW-induced calcination gives PILCs containing a fraction of residual, hydroxylated Al-polycations. The good thermal stability of the MW-Al-PILCs supports their possible use as acid catalysts.

Reactive nanocomposites based on pillared clays

This work concerns the preparation of novel nanocomposite materials deriving from pillared clays, which have been functionalised by treatment with either vanadium pentoxide or p-toluenesulfonic acid, with the aim to obtain porous materials with oxidant or strong acid character, respectively. The synthesis involves the use of montmorillonites and saponites, as starting 2:1 charged phyllosilicates to give the alumina pillared clays employed as host matrices for reagent inclusion. Characterisation of the resulting materials was provided by chemical and thermal analyses, XRD, SEM-EDX, FTIR and XPS spectroscopies, specific surface area and porosity measurements, and electrochemical impedance technique. The reactivities of the nanocomposite materials have been tested with positive results in the oxidation of alcohols to carbonyl compounds, in particular in the oxidation of benzyl alcohol to benzaldehyde, and also in the syntheses of methyl tert-butyl ether (MTBE) and bisphenol A. Good correlation between the proton conductivity obtained from electrochemical impedance and the acid catalytic activity of nanocomposites containing p-toluenesulfonic acid has been found.

CD6 modulates thymocyte selection and peripheral T cell homeostasis

Orta-Mascaró, Lozano, and collaborators provide the first analysis of CD6-deficient mice, showing that this molecule modulates T cell receptor signaling and the threshold for thymocyte and peripheral T cell subset selection.

Hereditary articular chondrocalcinosis: Clinical and genetic features in 13 pedigrees

Thirteen pedigrees with familial articular chondrocalcinosis were identified through a systematic radiologic survey of the first-degree blood relatives of 76 patients with chondrocalcinosis. Forty-one persons, 30 women and 11 men, distributed in 25 sibships were affected. Their mean age at the time of study was 65.09 +/- 11.36 years. The disease was of early onset only in four pedigrees. The clinical manifestations in these four pedigrees were similar to those found in the kindred with a late onset. In 15 persons, the process was asymptomatic. In the 26 symptomatic patients, the arthropathy was mild, with clinical and radiologic features similar to those observed in sporadic chondrocalcinosis. There was no linkage of chondrocalcinosis to the HLA-A and HLA-B antigens in the 11 pedigrees in which tissue typing was performed. The pattern of involvement in these 13 pedigrees supports an autosomal dominant mode of inheritance. These data suggest that hereditary chondrocalcinosis is not infrequent and very often is clinically indistinguishable from the sporadic form of the disease.

Proton conductivity in Al-montmorillonite pillared clays

Abstract Pillared clays (PILCs) are materials derived from smectite clay minerals (2:1 phyllosilicates) in which an interlayer formation of metal oxides, acting as pillars, produces a permanent separation between the silicate layers. It is assumed that protons are generated during the thermal treatment necessary for the pillar oxide formation, as it is the case for Al-montmorillonite PILCs. We have applied the electrochemical impedance technique with the aim of studying the proton conductivity of these pillared materials. Enhancement of electrical conductivity has been observed upon adsorption of oxyethylene compounds (crown-ethers and PEO) into the PILC galleries.

Mice deficient in CD38 develop an attenuated form of collagen type II-induced arthritis

CD38, a type II transmembrane glycoprotein expressed in many cells of the immune system, is involved in cell signaling, migration and differentiation. Studies in CD38 deficient mice (CD38 KO mice) indicate that this molecule controls inflammatory immune responses, although its involvement in these responses depends on the disease model analyzed. Here, we explored the role of CD38 in the control of autoimmune responses using chicken collagen type II (col II) immunized C57BL/6-CD38 KO mice as a model of collagen-induced arthritis (CIA). We demonstrate that CD38 KO mice develop an attenuated CIA that is accompanied by a limited joint induction of IL-1β and IL-6 expression, by the lack of induction of IFNγ expression in the joints and by a reduction in the percentages of invariant NKT (iNKT) cells in the spleen. Immunized CD38 KO mice produce high levels of circulating IgG1 and low of IgG2a anti-col II antibodies in association with reduced percentages of Th1 cells in the draining lymph nodes. Altogether, our results show that CD38 participates in the pathogenesis of CIA controlling the number of iNKT cells and promoting Th1 inflammatory responses.