Protein/polyelectrolyte coacervation: Investigating its occurrence in the lysozyme- carboxymethylcellulose system.

The coacervation of carboxymethylcellulose (CMC) and hen egg white lysozyme (HEWL) was investigated. The work focused on the effects of pH, ionic strength, I, temperature, T, and mass fraction of the macromolecular components on the coacervation process by spectrophotometry, and on characteristics of the resulting coacervate phase by rheology in the linear and non-linear regimes. Coacervation was found to be highest at HEWL mass fraction ≈0.25 with very slight dependence on pH in the range from 5 to 9. The process was favored at I < 0.075 mol·L-1 for NaCl, KCl and NaBr. For BaCl2, the dependence was markedly distinct, reflecting differences brought about by a bivalent cation on the Debye length of the electric double layer. The coacervation process has been characterized as endothermic and entropically driven. Rheological analysis of the coacervates indicated a rather low limit of the linear viscoelastic region (0.1% strain) and the prevalence of the elastic over the viscous contribution (G´â€¯> G´´). Despite configuring rather fragile structures, the presence of a network of strong interactions has been inferred from the observed pattern of variation of the moduli with frequency. In the non-linear regime, pseudoplasticity was observed, pointing out to the capacity of these structures in complying with the flow lines of the circumventing environment. Both apparently opposed characteristics suggest a possible evolutionary advantage of such structures in the prebiotic era.

Effects of bisphosphonates on osteogenesis and osteoclastogenesis signaling during the endochondral ossification of growing rats.

Osteoclasts and chondroclasts are necessary, during endochondral ossification, for the resorption of primary bone and calcified cartilage septa, respectively. The bisphosphonates inhibit mineralized tissue resorption by various mechanisms according to the different types of this drug, which can affect bone remodeling during skeletal growth. The objective of the present study is to analyze the way that alendronate (ALN) and etidronate (ETN) can affect osteoclastogenesis and bone formation during endochondral ossification of the long bones of growing rats. Newborn Wistar rats were treated daily with ETN, ALN, or sterile saline solution (control) for 21 days. Their femur and tibiae epiphyses were radiographed and analyzed by light, scanning and transmission electron microscopy. The expression of genes related to osteogenesis and to osteoclast differentiation and activity were analyzed by real-time quantitative polymerase chain reaction. The ETN group presented reduced body weight, disorganized growth plate and an extended area of cartilage in the ossification zone with little bone matrix; in the ALN group, this area was not altered. The ALN presented latent TRAP-positive cells, whereas in the ETN group, they were activated. The expression of NFκB1 and 2, OPG, Spp1 and Runx2 in the ossification zone was reduced by both bisphosphonates. RANKL expression was reduced by ETN, whereas ALN decreased the expression of RANK. The results also indicated that, in addition to the anti-resorptive effect of the drugs, disturbances in bone deposition occurred concomitantly with the reduced expression of osteogenesis-related genes.

Severe osteomalacia associated with renal tubular acidosis in Crohn's disease.

Severe renal tubular acidosis associated with massive osteomalacia is described in a patient with Crohn's disease. To our knowledge this association has not been previously recognized. The possible role of renal tubular acidosis in this patient's osteomalacia is discussed and the factors that could be involved in renal tubular acidosis in the context of Crohn's disease are analyzed.