Crystal structure refinements and compositional control of Mn-Mg-Ca ardennites from the Belgian Ardennes, Greece, and the Western Alps

The As5+ - V5+-bearing silicate ardennite is commonly present in highly oxidized, manganiferous metasediments that were affected by low- to high-pressure metamorphism in the T range from ca. 300 to 600-degrees-C. Electron microprobe analyses of ardennite from the Belgian Ardennes, Greece, and the Western Alps combined with the results from structure refinements on four ardennite crystals from Andros, Greece; Haute-Maurienne, French Western Alps; and Lago di Cignana, Valtournanche, Italy (two specimens of different composition), suggest the general formula VI(A1)2 (VII)(A2)2 (VI)(M1-M3)6 [(IV)T4(O,OH)4/(SiO4)2/Si3O10/(OH,O)6], where Al = Mn2+, Mg; A2 = Mn2+, Ca; Ml = Al, +/- Fe3+; M2 = Al; M3 = Al, Mg, +/- Fe3+, +/- Mn3+, +/- Cu2+, +/- Ni2, ; and T4 = As5+, V5+, P5+, Si4+. Least squares refinements of the four structures (space group Pnmm, a = 8.710(6)-8.767(3) Å, b = 5.803(4)-5.846(2) Å, c = 18.542(9)-18.613(6) Å) converged with R = 0.036-0.083 and allowed to locate the hydrogen atoms in ardennite from Haute-Maurienne. Mn3+ Al-1 substitution (up to 1.1 Mn3+ per 16 total cations) principally occurs in the M3 octahedron which is larger ([M3 - O] = 2.006 - 2.018 Å) and more distorted (two long and four short cation-oxygen distances) than the M1 (1.918 - 1.941 angstrom) and the M2 octahedron (1.897-1.906 angstrom). Within the range from zero to 0.4 Mn3+ p.f.u., obtained for the refined structures, however, the degree of distortion of the M3 octahedra is unrelated to the Mn3+. content. Fe3+ (up to 0.4 atoms p.f.u. in microprobe analyses) may enter either the M1 or, in Mn3+-free ardennite, the M3 site. Mg2+ is partitioned between the M3 octahedron (0.5 - 0.95 atoms p.f.u.) and the irregular (6 + 1)-coordinated A1 polyhedron (0 - 1.6 atoms p.f.u.). Ca has a strong preference for the larger 7-coordinated A2 site, where it substitutes for up to 77 mol% of the Mn2+ in Mn3+-rich ardennites from low-grade assemblages. Besides As5+ and/or V5+, the isolated T4 tetrahedron may incorporate significant Si4+ commonly up to 40 mol%) as well as up to 28 mol% P5+ in ultrahigh-pressure metamorphic ardennites. The [T4-O] distances range from 1.688 angstrom to 1.659 angstrom and reflect the variable extent of substitution of Si4+ and P5+ for As5+ and V5+. The chemical analyses suggest that charge balance for Al3+-Mg2+ substitution in M3 and Si4+-(As, V, P)5+ substitution in T4 is maintained by variations in the overall hydrogen content. During prograde high-pressure metamorphism, Mg (in A1 sites) and P5+ gradually increases as the result of multivariant reactions of ardennite with coexisting garnet, apatite, phengite, clinochlore/talc, quartz/coesite and piemontite. Ca, Mn3+ and Fe3+ contents in ardennite vary i) with T and P by virtue of Mn3+Al-I and Mn3+Fe-13+ exchange with braunite, hematite and piemontite and ii) as a result of different mineral assemblages in closely associated rocks

A Raman investigation of the amblygonite-montebrasite series

International audienceIn order to obtain a more accurate method of identification of minerals of the amblygonite - montebrasite series, and particularly of gemstones cut from these minerals, we undertook an investigation by Raman spectroscopy..

Increased Cell Proliferation and Mucocyte Density in the Sea Anemone Aiptasia pallida Recovering from Bleaching

Recovery of coral after bleaching episodes is a critical period for the health of the reef ecosystem. While events such as symbiont (genus Symbiodinium) shifting/shuffling or tissue apoptosis have been demonstrated to occur following bleaching, little is known concerning tissue recovery or cell proliferation. Here, we studied the sea anemone Aiptasia pallida exposed to a transient elevation of water temperature combined with high illumination (33°C and 1900 μmolphotons.m.s for 30h). Following such treatment bleached anemones showed a significant reduction of their Symbiodinium density. Cell proliferation in the ectodermis and gastrodermis was determined by assessing the densities of cells labeled with a thymidine analogue (EdU). Cell proliferation significantly increased during the first day following stress in both tissue types. This increased cell proliferation returned to pre-stress values after one week. Although cell proliferation was higher in the ectodermis in absence of stress, it was relatively more pronounced in the gastrodermis of stressed anemones. In addition, the ratio of ectodermal mucocytes significantly increased three weeks after induced stress. These results suggest that thermal/photic stress coupled with the loss of the symbionts is able to enhance cell proliferation in both gastrodermis and ectodermis of cnidarians. While new cells formed in the gastrodermis are likely to host new Symbiodinium, the fate of new cells in the ectodermis was only partially revealed. Some new ectodermal cells may, in part, contribute to the increased number of mucocytes which could eventually help strengthen the heterotrophic state until restoration of the symbiosis

In vitro evaluation of the anti-apoptotic drug Z-VAD-FMK on human ovarian granulosa cell lines for further use in ovarian tissue transplantation

peer reviewedPURPOSE: Because ovarian granulosa cells are essential for oocyte survival, we examined three human granulosa cell lines as models to evaluate the ability of the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK) to prevent primordial follicle loss after ovarian tissue transplantation. METHODS: To validate the efficacy of Z-VAD-FMK, three human granulosa cell lines (GC1a, HGL5, COV434) were treated for 48 h with etoposide (50 mug/ml) and/or Z-VAD-FMK (50 muM) under normoxic conditions. To mimic the ischemic phase that occurs after ovarian fragment transplantation, cells were cultured without serum under hypoxia (1 % O2) and treated with Z-VAD-FMK. The metabolic activity of the cells was evaluated by WST-1 assay. Cell viability was determined by FACS analyses. The expression of apoptosis-related molecules was assessed by RT-qPCR and Western blot analyses. RESULTS: Our assessment of metabolic activity and FACS analyses in the normoxic experiments indicate that Z-VAD-FMK protects granulosa cells from etoposide-induced cell death. When cells are exposed to hypoxia and serum starvation, their metabolic activity is reduced. However, Z-VAD-FMK does not provide a protective effect. In the hypoxic experiments, the number of viable cells was not modulated, and we did not observe any modifications in the expressions of apoptosis-related molecules (p53, Bax, Bcl-xl, and poly (ADP-ribose) polymerase (PARP)). CONCLUSION: The death of granulosa cell lines was not induced in our ischemic model. Therefore, a protective effect of Z-VAD-FMK in vitro for further use in ovarian tissue transplantation could not be directly confirmed. It will be of interest to potentially use Z-VAD-FMK in vivo in xenograft models

Multistage growth of Fe–Mg–carpholite and Fe–Mg–chloritoid, from field evidence to thermodynamic modelling

© 2014, Springer-Verlag Berlin Heidelberg. We provide new insights into the prograde evolution of HP/LT metasedimentary rocks on the basis of detailed petrologic examination, element-partitioning analysis, and thermodynamic modelling of well-preserved Fe–Mg–carpholite- and Fe–Mg–chloritoid-bearing rocks from the Afyon Zone (Anatolia). We document continuous and discontinuous compositional (ferromagnesian substitution) zoning of carpholite (overall XMg = 0.27–0.73) and chloritoid (overall XMg = 0.07–0.30), as well as clear equilibrium and disequilibrium (i.e., reaction-related) textures involving carpholite and chloritoid, which consistently account for the consistent enrichment in Mg of both minerals through time, and the progressive replacement of carpholite by chloritoid. Mg/Fe distribution coefficients calculated between carpholite and chloritoid vary widely within samples (2.2–20.0). Among this range, only values of 7–11 correlate with equilibrium textures, in agreement with data from the literature. Equilibrium phase diagrams for metapelitic compositions are calculated using a newly modified thermodynamic dataset, including most recent data for carpholite, chloritoid, chlorite, and white mica, as well as further refinements for Fe–carpholite, and both chloritoid end-members, as required to reproduce accurately petrologic observations (phase relations, experimental constraints, Mg/Fe partitioning). Modelling reveals that Mg/Fe partitioning between carpholite and chloritoid is greatly sensitive to temperature and calls for a future evaluation of possible use as a thermometer. In addition, calculations show significant effective bulk composition changes during prograde metamorphism due to the fractionation of chloritoid formed at the expense of carpholite. We retrieve P–T conditions for several carpholite and chloritoid growth stages (1) during prograde stages using unfractionated, bulk-rock XRF analyses, and (2) at peak conditions using compositions fractionated for chloritoid. The P–T paths reconstructed for the Kütahya and Afyon areas shed light on contrasting temperature conditions for these areas during prograde and peak stages