A stable and 40Ar/39Ar isotope study of a major thrust in the Helvetic nappes (Swiss Alps) - Evidence for fluid-flow and constraints on nappe kinematics

Stable isotope and Ar-40/Ar-39 measurements,were made on samples associated with a major tectonic discontinuity in the Helvetic Alps, the basal thrust of the Diablerets nappe (external zone of the Alpine Belt) in order to determine both the importance of fluids in this thrust zone and the timing of thrusting. A systematic decrease in the delta(18)O values (up to 6 parts per thousand) of calcite, quartz, and white mica exists within a 10- to 70-m-wide zone over a distance of 37 km along the thrust, and they become more pronounced toward the root of the nappe. A similar decrease in the delta(13)C values of calcite is observed only in the deepest sections (up to 3 parts per thousand). The delta D-SMOW (SMOW = standard mean ocean water) values of white mica are -54 parts per thousand +/- 8 parts per thousand (n = 22) and are independent of the distance from the thrust. These variations are interpreted to reflect syntectonic solution reprecipitation during fluid passage along the thrust. The calculated delta(18)O and delta D values (versus SMOW) for the fluid in equilibrium with the analyzed minerals is 12 parts per thousand to 16 parts per thousand and -30 parts per thousand to +5 parts per thousand, respectively, for assumed temperatures of 250 to 450 degrees C. The isotopic and structural data are consistent with fluids derived from the deep-seated roots of the Helvetic nappes where large volumes of Mesozoic sediments were metamorphosed to the amphibolite facies, It is suggested that connate and metamorphic waters, overpressured by rapid tectonic burial in a subductive system escaped by upward infiltration along moderately dipping pathways until they reached the main shear zone at the base of the moving pile, where they were channeled toward the surface, This model also explains the mechanism by which large amounts of fluid were removed from the Mesozoic sediments during Alpine metamorphism. White mica Ar-49/Ar-39 ages vary from 27 Ma far from the Diablerets thrust to 15 Ma along the thrust. An older component is observed in micas far from the thrust, interpreted as a detrital signature, and indicates that regional metamorphic temperatures were less than about 350 degrees C. The;plateau and near plateau ages nearest the thrust are consistent with either neocrystallization of white mica or argon loss by recrystallization during thrusting, which may have been enhanced in the zones of highest fluid flow. The 15 Ma Ar-40/Ar-39 age plateau measured on white mica sampled exactly on the thrust surface dates the end of both fluid flow and tectonic transport.

Two monoclonal rat antibodies with specificity for the beta-chain variable region V beta 6 of the murine T-cell receptor.

Two rat monoclonal antibodies (mAbs), 44-22-1 and 46-6B5, which recognize an alloreactive cytotoxic clone, 3F9, have been further tested on a panel of T hybridomas and cytotoxic T-cell clones for binding and functional activities. The mAbs recognized only those cells sharing the expression of the T-cell receptor beta-chain variable region gene V beta 6 with 3F9. All V beta 6+ cells were activated by these mAbs under cross-linking conditions and their antigen-specific activation was blocked by soluble mAb. Furthermore, depletion of 46-6B5+ normal lymph node T cells eliminated all cells expressing the epitope recognized by 44-22-1 and V beta 6 mRNA.

Glut9 is a major regulator of urate homeostasis and its genetic inactivation induces hyperuricosuria and urate nephropathy.

Elevated plasma urate levels are associated with metabolic, cardiovascular, and renal diseases. Urate may also form crystals, which can be deposited in joints causing gout and in kidney tubules inducing nephrolithiasis. In mice, plasma urate levels are controlled by hepatic breakdown, as well as, by incompletely understood renal processes of reabsorption and secretion. Here, we investigated the role of the recently identified urate transporter, Glut9, in the physiological control of urate homeostasis using mice with systemic or liver-specific inactivation of the Glut9 gene. We show that Glut9 is expressed in the basolateral membrane of hepatocytes and in both apical and basolateral membranes of the distal nephron. Mice with systemic knockout of Glut9 display moderate hyperuricemia, massive hyperuricosuria, and an early-onset nephropathy, characterized by obstructive lithiasis, tubulointerstitial inflammation, and progressive inflammatory fibrosis of the cortex, as well as, mild renal insufficiency. In contrast, liver-specific inactivation of the Glut9 gene in adult mice leads to severe hyperuricemia and hyperuricosuria, in the absence of urate nephropathy or any structural abnormality of the kidney. Together, our data show that Glut9 plays a major role in urate homeostasis by its dual role in urate handling in the kidney and uptake in the liver.