Alzheimer's disease and Fragile X syndrome both display synaptic phenotypes, and based on recent studies, likely share dendritic over expression of amyloid precursor protein (APP) and beta-amyloid ...(Abeta). In order to create a mouse model to specifically study the effects of APP and Abeta at synapses, we crossed Tg2576, which over-express human APP with the Swedish mutation (hAPPsw), with fmr-1 KO mice. The progeny, named FRAXAD, displayed increased mortality (23% by 30 days of age) compared to Tg2576 (3%) and WT and fmr-1 KO littermate controls (0%) consistent with a developmental defect. By 60 days of age, both the Tg2576 and FRAXAD mice approached a 40% mortality rate compared to 0% for WT and fmr-1 KO littermates. To understand the mechanism underlying increased mortality in APP over-expressing mice, we assessed seizure thresholds in response to pentylenetetrazol (PTZ). Both the Tg2576 and FRAXAD mice had a lower threshold to PTZ-induced seizures (average seizure score of >/=4.0) in comparison to nontransgenic littermates (average seizure score 1.9-2.9). Seizures are a major phenotype of AD, FXS, Down syndrome, autism and epilepsy, and these data suggested that developmental over-expression of dendritic APP or Abeta increased seizure susceptibility.
We present results of dehydration melting experiments 3–15 kbar, 810–950°C f(O2) ≤ QFM (quartz-fayalite-magetite) and ≥ Ni-NiO on two Fe-rich mixtures of biotite (37%), plagioclase An38 (27%), quartz ...(34%) and ilmenite (2%), which differ only in their biotite compositions (mg-number 23 and 0.4). Dehydration melting of metagreywackes of constant modal composition generates a wide range of melt fractions, melt compositions and residual assemblages, through the combined effects of pressure, Fe/Mg ratio and f(O2). Crystallization of garnet is the chief control on melting behavior, and is limited by two reactions: (1) the breakdown of garnet + quartz to orthopyroxene + plagioclase at low P, and (2) the oxidation of garnet to magnetite + anorthite + quartz (±enstatite), which is sensitive to both f(O2) and P. Because of these reactions, melting of Mg-rich metagreywackes is rather insensitive to f(O2) but strongly sensitive to P; the converse is true for Fe-rich metagreywackes. Garnet crystallization requires that plagioclase break down incongruently, liberating albite. This increases the Na2O content of the melts and enhances melt production. Thus, melting of metagreywacke in a reducing deep-crustal environment (with garnet stable) would produce more, and more sodic, melt than would garnet-absent melting of the same source material in a relatively oxidizing, shallow-crustal environment.
Models using hydration crystallization reactions (the reverse of dehydration melting reactions such as
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} ...\usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackageOT2,OT1{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{amph}\,+\mathrm{qtz}\,=\mathrm{px}\,+\mathrm{melt}\,$ \end{document}
) for the Bell Island pluton define incongruent equilibrium crystallization paths from hydrous
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackageOT2,OT1{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{melt}\,+\mathrm{pyroxene}\,+\mathrm{Fe}\,$ \end{document}
‐Ti
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackageOT2,OT1{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{oxides}\,+\mathrm{calcic}\,$ \end{document}
andesine (30%–50% solid) to a solid tonalite consisting mostly of hornblende, biotite, epidote, sodic andesine, and quartz. In essence, hydration crystallization is a way to quantify and modify the lower temperature end of Bowen’s discontinuous reaction series and apply it to natural samples. Hydration crystallization provides an alternative to crystal fractionation for explaining variations in pluton chemistry, especially the compositions of late plutonic melts. Another characteristic of hydration crystallization is that the reactions have the potential to buffer the water content of the melt during crystallization. Two closed‐system models, representing different sets of starting conditions and phases, are considered, based on least squares, mass‐balance calculations of reactions and constrained by the petrography of the rocks. Model 1 starts with an average modified Bell Island leucotonalite melt coexisting with two pyroxenes, two Fe‐Ti oxides, and plagioclase at the beginning of hydration crystallization. The starting assemblage of model 2 omits orthopyroxene and magnetite, includes amphibole, and uses a calculated melt composition. Both models generally predict, via different series of hydration crystallization reactions, the observed subsolidus mode. Model 2, however, is preferred based on petrographic observations of the Bell Island rocks, specifically the lack of magnetite and orthopyroxene, as well as certain textural features.
The primary goal of this investigation was to derive a set of expressions that can be used to calculate the amphibole-melt partitioning behavior of the rare earth elements (REE) and the high field ...strength elements (HFSE) in natural systems. To supplement the existing data set on basaltic systems, we conducted experiments on systems where amphibole was in equilibrium with dacitic, tonalitic and low Si rhyolitic melts. These experiments, doped with La, Sm, Gd, Lu, Ta, Nb, Y, Zr, and Hf, were run at pressures of 2 and 5 kbar, temperatures between 900°C and 945°C, and oxidation conditions ranging from QFM-1 to NiNiO+1.
The partitioning data obtained in this study were combined with published data to calculate two sets of expressions describing trace element partitioning. The first set models the partitioning of trace elements into amphibole using temperature, pressure and several compositional parameters, including the compositionally-compensated partition coefficients of Ti, Al, Caand SiO
2, and the exchange of Fe and Mg between the crystal and the melt (D
Mg/D
Fe). The second set of expressions are slightly less precise, but require no specific knowledge of P, T, or f
O2 and, for application to natural systems, can be constructed solely on the basis of information available from standard electron microprobe analyses. These expressions predict amphibole-melt partition coefficients for REE and HFSE within an internal precision of 14–40% (relative) for alkali basalt to low Si rhyolite, from 850°C to 1100°C, 2–20 kbar and oxygen fugacity from QFM-1 to NiNiO+1.
Partition coefficients calculated from the expressions derived in this study were used to model the partial melting and fractional crystallization of a hypothetical amphibolite and hydrous melt, respectively. Fractionation and/or melting in amphibole-bearing systems produces a magma with a convex upward REE pattern, a characteristic common to many hornblende-bearing dacites. However, the removal or addition of an amphibole component cannot produce the strong HFSE depletion relative to the REE observed in many arc magmas.
On the Iberia Abyssal Plain (Ocean Drilling Program Site 1070), gabbroic pegmatites and related rocks (127 ± 4 Ma, U–Pb zircon) intrude upper mantle that was subsequently exposed and serpentinized ...during Early Cretaceous non-volcanic rifting. The pegmatites include a 3–4 m dike or sill (the ‘main’ pegmatite), numerous dikelets of 1–5 cm thickness, and clasts within the overlying ophicalcite breccia. Exclusive of rodingitization, the main pegmatite contains 40–70% calcic andesine, 25–35% kaersutitic amphibole (Mg# 60–70), 5–25% augite (Mg# 70–80) and 1–2% ilmenite. The dikelets are more magnesian (Mg# up to 82 in kaersutite and 88 in augite). Most indications are that the high Mg#s in the dikelets reflect igneous compositions. Isotopic and elemental chemistry indicate that the pegmatite-forming melt was enriched in incompatible elements relative to normal mid-ocean ridge basalt, but not as enriched as Azores basalts. The amphibole-bearing plagioclase peridotites of the Iberia Abyssal Plain are an appropriate source for the pegmatite melts. A combination of decompression accompanying unroofing and heating from the upwelling asthenosphere beneath the developing rift caused P–T conditions in the amphibole-bearing lithosphere to exceed the dehydration-melting solidus (∼1050°C), producing small-volume, enriched, hydrous melts. Pegmatite intrusion pre-dates unroofing at Site 1070 and post-dates syn-rift sedimentation and faulting of serpentinite seen inboard on the Iberia Abyssal Plain. Thus, serpentinization and unroofing were time-transgressive and the age of the non-volcanic sea floor formed by the unroofed mantle grows younger outboard, just as is the case for normal, volcanic sea floor.
Preeclampsia affects ∼2-8% of pregnancies worldwide. It is associated with increased long-term maternal cardiovascular disease risk. This study assesses the effect of the vasoconstrictor ...N(ω)-nitro-L-arginine methyl ester (L-NAME) in modelling preeclampsia in mice, and its long-term effects on maternal cardiovascular health. In this study, we found that L-NAME administration mimicked key characteristics of preeclampsia, including elevated blood pressure, impaired fetal and placental growth, and increased circulating endothelin-1 (vasoconstrictor), soluble fms-like tyrosine kinase-1 (anti-angiogenic factor), and C-reactive protein (inflammatory marker). Post-delivery, mice that received L-NAME in pregnancy recovered, with no discernible changes in measured cardiovascular indices at 1-, 2-, and 4-wk post-delivery, compared with matched controls. At 10-wk post-delivery, arteries collected from the L-NAME mice constricted significantly more to phenylephrine than controls. In addition, these mice had increased kidney
and heart
mRNA expression, indicating increased inflammation. These findings suggest that though administration of L-NAME in mice certainly models key characteristics of preeclampsia during pregnancy, it does not appear to model the adverse increase in cardiovascular disease risk seen in individuals after preeclampsia.
A new locality for the Ba-rich trioctahedral mica, kinoshitalite Ba(Mg,Mn,Fe,Al)3Si1.9-2Al2-2.2O10(OH,F)2, has been found in a metamorphosed manganoan marble from Pittsylvania County, Virginia. ...Metamorphic grade is middle amphibolite facies, with documented P and T of 400 MPa and 575°C. The locality is along strike not far from the well known Bald Knob, North Carolina, Mn-mineral locality, and appears to represent a silica-poorer analog of Bald Knob. The kinoshitalite occurs in a single layered hand sample containing both skarn and marble layers, and it shows significant compositional contrasts between the two lithologies. Kinoshitalite is scarce and fine-grained in manganoan marble and coexists with kutnahorite, manganoan calcite, fluorian alleghanyite, fluorian sonolite, aluminous jacobsite, and alabandite. Kinoshitalite is both more abundant and coarser-grained in skarn where it coexists with kutnahorite, tephroite, fluorian manganhumite, spessartine, jacobsite, and manganoan magnetite. A-sites in kinoshitalite in skarn are about 3/4 occupied by Ba (with the remainder mostly K), whereas in marble, Ba occupancy of A-sites exceeds 90% and most of the remainder is Ca.XMg in octahedral sites is >0.6 and is higher in marble than in skarn, whereas XMn is significant (>0.2) and is higher in skarn than in marble. The VIAl is significantly higher in skarn kinoshitalite, as is total Tschermak content. The total Tschermak content of these barian micas (VIAl+Ti+Fe3+) is typical of all previously reported kinoshitalites and is significantly lower than that of clintonite and biotite. The XF of kinoshitalite in marble is significantly higher than that in skarn. The petrogenesis of kinoshitalite at the Hutter Mine locality is unclear due to the lack of context for the single mine-dump sample in which the mineral was found and the absence of textural evidence for reactions. However, the two likeliest source minerals for Ba that have been found in the deposit are barite and BaCa(CO3)2 (probably barytocalcite). One hypothetical reaction to produce kinoshitalite involves decarbonation, in which BaCa(CO3)2, rhodochrosite, Mn-garnet, and aqueous fluid react to form kinoshitalite, tephroite, (or an Mn-humite), calcite, and CO2. A second potential reaction to form kinoshitalite involves barite, Mn-garnet, tephroite, and aqueous fluid as reactants, and kinoshitalite, alabandite, jacobsite, SiO2, and O2 as products.
The Hutter Mine locality, Pittsylvania County, Virginia, is a metamorphosed magnetite deposit, with substantial development of subsidiary manganoan marble, that occurs within Latest Precambrian or ...Early Paleozoic sillimanite-grade pelitic schists. Manganese oxides and spinels at the Hutter Mine include manganosite (MnO) (coexisting with hausmannite and jacobsite) as well as spinels rich in jacobsite (FeMn2O4), magnetite (Fe3O4), and galaxite (MnAl2O4), and a variety of intermediate solid solutions between these three end-members. Several samples contain spinels that exhibit substantial miscibility along the jacobsite-galaxite and jacobsite-magnetite joins. Magnetite-galaxite solid solution is, by comparison, very limited. Coexisting manganoan spinels within the jacobsite-galaxite-magnetite ternary system include jacobsite-rich varieties with galaxite <65 (normalized to glx+mag+jac = 100) that coexist with Mg-Zn-bearing galaxite-rich spinel with galaxite >75. However, the wide range of spinel compositions at the Hutter Mine largely reflects compositional variability in the host rock. In a skarn reaction zone between Fe-rich, quartz-bearing amphibolites and Si-poor, Mn-rich marbles, the galaxite content of spinel drops from 60% to near zero as silica activity increases over a 5 mm interval. In this same reaction zone, magnetite content of spinel increases from about 10 to 95%, but over a narrower interval (about 2 mm). Total variation in spinel composition in this reaction zone is nearly the same as that seen over the entire suite of Hutter Mine samples. Both regional metamorphic geology and thermobarometry on local pelite samples indicates that Tmax at the Hutter Mine was 550-600°C. Manganosite formed by the decarbonation of Mn-rich carbonate in the presence of a CO2-poor (XCO2≥0.01) fluid having log aSiO2<-3.0. Oxygen fugacity in the manganosite-bearing sample was buffered by coexisting manganosite and hausmannite, placing fO2 within the magnetite stability field at peak T. This result is consistent with the occurrence of magnetite as the principal ore at Hutter. The extensive miscibility observed along the jacobsite-galaxite join requires reexamination of miscibility gaps proposed in previous studies. We suggest that the wide compositional gaps found in previous studies reflect a variety of chemical factors of which silica activity is the most critical. In particular, the large range of silica activities observed in Hutter Mine rocks stabilizes spinels with a wide range in galaxite content. The crests of both the jacobsite-galaxite and jacobsite-magnetite two-phase regions appear to occur at relatively low temperatures, probably below 600°C.
Closed-system partial melts of hydrated, metamorphosed arc basalts and andesites (greenstones and amphibolites), where only water structurally bound in metamorphic minerals is available for melting ...(dehydration melting), are generally water-undersaturated, coexist with plagioclase-rich, anhydrous restites, and have compositions like island arc tonalites. In contrast, water-saturated melting at water pressures of 3 kilobars yields strongly peraluminous, low iron melts that coexist with an amphibole-bearing, plagioclase-poor restite. These melt compositions are unlike those of most natural silicic rocks. Thus, dehydration melting over a range of pressures in the crust of island arcs is a plausible mechanism for the petrogenesis of islands arc tonalite, whereas water-saturated melting at pressure of 3 kilobars and above is not.
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