Cross-linking of Li-montmorillonite by hydroxy-aluminum oligomers was performed in a specially constructed mixing apparatus. Observations on flocculation and solution composition were carried out during and after the cross-linking reaction; the dry product was studied by scanning electron microscopy.

Flocculation was most pronounced at Al/montmorillonite ratios between 0.98 and 2.45 mM/g; below and above this range, flocculation was much less intensive. These observations can be explained by heterocoagulation and protecting colloid action. A complete neutralization of the montmorillonite charge was estimated at 1.9 mM adsorbed Al per g clay, and in order to account for the electrical charge of the hydroxy-Al, polymers with an average charge of 0.5 per Al atom must be assumed on the montmorillonite surface. Assuming that the hydroxy-aluminum form in the unreacted solution is Al6(OH)3+12, the adsorbed polymer will be Al24(OH)12+60. Alternatively, assuming Al6(OH)3+15 in the unreacted solution, this form will remain unchanged upon adsorption onto the montmorillonite surface.

Differences in the microfabric of dry Al-CLM as a function of Al/montmorillonite ratio can be explained along the lines of the interpretation of the flocculation studies.

Hydroxide and oxyhydroxide products of aluminum were formed at room temperature at an initial Al concentration of 2 × 10-3 M, pH 8.2, and at varying concentrations of organic and inorganic ligands commonly found in nature. The effectiveness of the ligands in promoting the formation of noncrystalline products over crystalline Al(OH)3 polymorphs was found to be in the following order: phthalate ≅ succinate < glutamate < aspartate < oxalate < silicate ≅ fluoride < phosphate < salicylate ≅ malate < tannate < citrate < tartrate. The lowest ligand/Al molar ratio at which the production of Al hydroxides or oxyhydroxides was inhibited ranged from 0.02 to 15. Above critical ligand/Al ratios, crystalline products were inhibited and ligands coprecipitated with noncrystalline products which remained unchanged for at least 5 months. Polydentate and large ligands generally were more inhibitive than those with fewer functional groups or of smaller size.

The perturbing ligands promoted and stabilized the formation of pseudoboehmite over crystalline Al(OH)3 polymorphs in the following sequence: chloride < sulfate < phthalate ≅ succinate < glutamate < silicate < aspartate < phosphate < salicylate ≅ malate < tannate < citrate < tartrate. The optimal range of the ligand/Al molar ratios for the formation of pseudoboehmite varied, for example, from 0.005–0.015 for tartrate to 600–1000 for chloride. Pseudoboehmite was not formed in the presence of fluoride.

Siderophores are low molecular weight organic ligands synthesized by aerobic microorganisms to acquire Fe. In addition to Fe(III), siderophores may complex other metals such as Pb and Cd. This study compared the effects of the trihydroxamate siderophores desferrioxamine-B (DFO-B), desferrioxamine-D1 (DFO-D1), desferrioxamine-E (DFO-E), and the monohydroxamate siderophore-like ligand acetohydroxamic acid (aHA) on Pb and Cd (except for DFO-E) adsorption to kaolinite (KGa-1b) at pH 4.5 to 9, in 0.1 M NaClO4, at 22°C, in the dark. At pH >6, all of the studied ligands decreased Pb adsorption to kaolinite: aHA by 5–40% and DFO-B, DFO-D1 and DFO-E by 30–75%; the greater effects were at higher pH. The studied ligands decreased Cd adsorption to kaolinite at pH >8: aHA by 5–20% and the trihydroxamates by as much as 80%. We also observed enhancement of Pb adsorption in the presence of DFO-B at pH ≈5–6.0, probably due to adsorption of the doubly positively charged H3Pb (DFO-B)2+ complex, although spectroscopic evidence is needed.

PPARγ is obligatory for fat mass generation and is thought to determine the amount of TAG stored per fat cell. We investigated whether ligand availability for PPARγ is rate limiting in fat mass generation and substrate metabolism. Twenty healthy men (20–29 years) were randomly assigned to receive the PPARγ ligand rosiglitazone (RSG) (8 mg/d) (n 10) or a placebo (n 10) during a stay of 7 d in a respiration chamber. Food intake was ad libitum, resulting in positive energy balances of 32·2 MJ (placebo) and 44·7 MJ (RSG). Fat cell size and expression of PPARγ, adipocyte fatty acid-binding protein (aP2), adipsin, adiponectin and fasting-induced adipose factor (FIAF) were determined in subcutaneous abdominal fat biopsies. The total amount of fat stored and the amount of TAG per fat cell were not different between groups. For the entire group, fat cell size was decreased after overeating (P = 0·02). FIAF mRNA levels were decreased after overeating in the RSG group (P = 0·01), with a trend towards a decrease in the placebo group. Unexpectedly, RSG treatment did not influence the expression levels of PPARγ and of the PPARγ responsive genes aP2, adiponectin and adipsin. In addition, RSG resulted in a larger increase in plasma TAG during overeating than placebo treatment. These results suggest that in healthy, non-obese males the PPARγ ligand RSG influences TAG metabolism, independent of its PPARγ transcriptional activity in the subcutaneous adipose tissue.

Infective larvae of the dog roundworm Toxocara canis survive in the tissues of their hosts for extended periods in a state of developmental arrest, successfully evading immune destruction. This survival strategy is thought to be mediated by T. canis excretory/secretory (TES) products which downregulate or divert the immune response. We purified one of the major TES products, TES-70 and gained amino acid sequence from 4 tryptic peptides. These peptides were matched to a predicted protein from a cDNA that was isolated by expression screening a T. canis cDNA library with mouse anti-TES serum. The predicted protein (Tc-CTL-4) is similar to, but larger than, Tc-CTL-1, a 32-kDa C-type lectin secreted by T. canis larvae. Tc-CTL-4 has a signal peptide, 2 Cys-rich domains and a C-terminal calcium-dependent C-type lectin domain that shares sequence similarity with host immune cell receptors such as macrophage mannose receptor and CD23. The lectin domain was expressed in bacteria and antiserum to the purified recombinant protein was used to confirm that Tc-ctl-4 did encode the native TES-70 glycoprotein. TES-70 selectively bound to ligands on the surface of Madin–Darby Canine Kidney cells in vitro in a calcium-dependent manner, inhibitable by mammalian serum, indicating that a host glycan is the native ligand for this new parasite lectin.