Marine atmospheric corrosion of reference metals in tropical climates of Latin-America

This article presents the results obtained at 16 tropical test sites participating in the >Ibero-American Map of Atmospheric Corrosiveness> (MICAT), a project on atmospheric corrosion carried out during the period 1988-1994 at some 70 test sites distributed across 12 countries of the Latin-American region, Spain and Portugal. The tropical climate and its different climatic variants are characterized by high average air temperatures, with considerable daily thermal fluctuations, high average relative humidity, and generally high precipitation volumes. The work is structured in three main blocks: apparently unpolluted atmospheres (i), and marine atmospheres, differentiating between pure marine atmospheres (ii) and those in which both chloride (Cl) and sulfur dioxide (SO2) pollutants coexist (iii). In each block an attempt was made to determine the role of the tropical climate in the magnitude of corrosion attack shown by four typical reference metals (mild steel, zinc, copper and aluminum) exposed for one-year periods in tropical atmospheric exposure conditions.Peer Reviewe

Effects of commonly used immunosuppressants on graft-derived fibroblasts

In acute rejection of transplanted organs intragraft fibroblasts increase their production of hyaluronan. Hyaluronan has strong water binding capacity and an increased tissue content of hyaluronan thus contributes to the development of interstitial oedema. The present study examined the effects of commonly used immunosuppressants (prednisolone, cyclosporin, tacrolimus, mycophenolic acid and sirolimus) on fibroblast proliferation, hyaluronan production and cell surface receptor expression. Fibroblasts isolated from rejecting tissue and from normal, non-transplanted tissue were studied in parallel. All substances investigated, except tacrolimus, were found to affect fibroblasts in one way or another. The most striking effect was the almost total inhibition of fibroblast proliferation in the presence of mycophenolic acid. Cyclosporin reduced the proliferation by about 50% and prednisolone had an inhibiting effect on hyaluronan production (50% reduction). These effects were observed on fibroblasts isolated from rat cardiac allografts undergoing rejection as well as on fibroblasts obtained from normal heart tissue. In contrast, sirolimus was found to stimulate the proliferation of fibroblasts from rejecting tissue (100% increase), but not that of normal fibroblasts. The majority of the fibroblasts expressed the hyaluronan receptor CD44, with a more intense expression in cultures of fibroblasts derived at rejection. None of the immunosuppressants affected the staining pattern (number of positive cells or intensity). The inhibitory effects of prednisolone, cyclosporin and mycophenolic acid on fibroblasts may contribute to the overall beneficial effects of these drugs when used for prevention or treatment of rejection