It has been suggested that in uremic bone, aluminum interferes with normal mineralization. Aluminum content and aluminum localization were studied in iliac crest biopsies of two groups of patients on regular hemodialysis; one group had histologic osteomalacia, and little or no bone resorption (group 1); the other, osteitis fibrosa and no mineralization defect (group 2). Group 1 patients had significantly higher plasma aluminum concentrations than those of group 2. No difference was found in bone aluminum content, which was above normal in both groups. In the bone samples of the osteomalacic subjects, aluminum was mainly localized at the limit between osteoid and calcified tissue, the site where the bone mineral is normally first deposited. Osteomalacia could not be related to hypocalcemia or to phosphate depletion. Active vitamin D derivatives (25-hydroxycholecalciferol and 1alpha-hydroxycholecalciferol) failed to prevent or to improve the bone disease. In the bone samples of group 2 subjects, aluminum could not be localized by the methods used, except in the two cases with greatly elevated bone aluminum, where it was mainly localized on cement lines. In group 2 subjects, immunoreactive parathyroid hormone plasma concentration, osteoclast surface, and marrow fibrosis were significantly higher than they were in group 1 subjects. It is concluded that in bone from uremic patients on regular dialysis, aluminum can induce a particular form of osteomalacia, resistant to the vitamin D active derivatives. The bone disease is only observed in the absence of severe secondary hyperparathyroidism. This suggests that parathyroid hormone may be involved in the development of the aluminum-induced mineralization defect.
Fine particulate matter present in urban areas seems to be incriminated in respiratory disorders. The aim of this study was to relate physicochemical characteristics of PM2.5 (particulate matter collected with a 50% efficiency for particles with an aerodynamic diameter of 2.5 microm) to their biological activities toward a bronchial epithelial cell line 16-HBE. Two seasonal sampling campaigns of particles were realized, respectively, in a kerbside and an urban background station in Paris. Sampled-PM2.5 mainly consist of particles with a size below 1 microm and are mainly composed of soot as assessed by analytical scanning electron microscopy. The different PM2.5 samples contrasted in their PAH content, which was the highest in the kerbside station in winter, as well as in their metal content. Kerbside station samples were characterized by the highest Fe and Cu content, which appears correlated to their hydroxyl radical generating properties measured by electron paramagnetic resonance. Particles were compared by their capacity to induce cytotoxicity, intracellular ROS production, and proinflammatory cytokine release (GM-CSF and TNF-alpha). At a concentration of 10 microg/cm2, all samples induced peroxide production and cytokine release to the similar extent in the absence of cytotoxicity. In conclusion, whereas the PM2.5 samples differ by their PAH and metal composition, they induce the same biological responses likely either due to components bioavailability and/ or interactions between PM components.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.