Proterozoic tectonostratigraphy and paleogeography of central Madagascar derived from detrital zircon U-Pb age populations

Detrital zircon U-Pb ages determined by SHRIMP distinguish two clastic sequences among Proterozoic metasedimentary rocks from central Madagascar. The Itremo Group is older: zircon data, stromatolite characteristics, and carbon isotope data all point to a depositional age around 1500-1700 Ma. The Molo Group is younger, deposited between ∼620 Ma (the age of the youngest zircon) and ∼560 Ma (the age of metamorphic overgrowths on detrital cores). Geochronologic provenance analysis of the Itremo Group points to sources in East Africa as well as local sources in central and southern Madagascar but provides no evidence for a detrital contribution from northern and eastern Madagascar nor from southern India. Detrital zircon and sedimentologic similarities between rocks of the Itremo Group and the Zambian Muva Supergroup suggest a lithostratigraphic correlation between the two. The Molo Group has a strong 1000-1100 Ma detrital signature that also indicates an east African provenance and suggests a Neoproterozoic geographic connection with Sri Lanka but shows no indication of input from the Dharwar craton and eastern Madagascar. Central Madagascar was probably juxtaposed with the Tanzanian craton in the Paleo- and Mesoproterozoic, whereas northern and eastern Madagascar were connected to India. Internal assembly of Madagascar postdates Neoproterozoic Molo Group sedimentation and is likely to have occurred at about 560 Ma. © 2004 by The University of Chicago. All rights reserved.Rónadh Cox, Drew S. Coleman, Carla B. Chokel, Stephen B. DeOreo, Joseph L. Wooden, Alan S. Collins, Bert De Waele, and Alfred Kröne

The emerging role of ADAM metalloproteinases in immunity

Proteolysis is an irreversible physiological process that can result in the termination or activation of protein function. Many transmembrane proteins that are involved in the cellular communication between immune cells and structural cells-for example, Notch, CD23, CD44, and membrane-anchored cytokines and their receptors-are cleaved by the ADAM (a disintegrin and metalloproteinase) family of enzymes. Here, we review recent insights into the molecular activation, substrate specificity and function of ADAM proteins in the development and regulation of the immune system, with a particular focus on the roles of ADAM10 and ADAM17