Upper Mantle Pollution during Afar Plume-Continental Rift Interaction

International audienceNew Pb, Sr, Nd, Hf, and He isotope data for Quaternary basalts, erupted from Debre Zeyit, Butajira, and the Wonji Fault Belt of the Main Ethiopian Rift, show systematic mixing relationships involving three distinct mantle sources. The Pb, Sr, Nd, and Hf isotopic arrays converge in a specific region of isotopic multi-space where they define the composition of the Afar mantle plume (centered about (206)Pb/(204)Pb = 19 center dot 5, (87)Sr/(86)Sr = 0 center dot 7035, epsilon(Nd) = +4 center dot 6, epsilon(Hf) = +9 center dot 3, (3)He/(4)He > 15 R(A)). This plume end-member has an identical composition to that observed previously in oceanic basalts. The distinct isotopic arrays for the various volcanic areas in the Main Ethiopian Rift vary spatially in a systematic manner, and may be viewed as pseudo-binary mixing arrays. This further suggests that the Afar mantle plume interacts with the local continental lithosphere and upper mantle asthenosphere (mid-ocean ridge basalt-like source) through an ordered sequence of mixing events. Simple mixing models require that the mass proportions of continental lithosphere and upper mantle involved in magma generation must be nearly constant within each volcanic area, but that the proportion of plume material decreases regularly with distance southwestward along the Main Ethiopian Rift, away from the central axis of the plume. This systematic behavior means that continental lithosphere can become detached and mixed into the shallow mantle prior to the flow of upwelling plume material beneath the developing rift system. Detachment and mixing into the asthenosphere during continental rift evolution is an important process for producing the range of ambient upper mantle compositions sampled by mid-ocean ridge volcanism away from island hotspots

Fatty Acids Increase Neuronal Hypertrophy of Pten Knockdown Neurons

Phosphatase and tensin homolog (Pten) catalyzes the reverse reaction of PI3K by dephosphorylating PIP3 to PIP2. This negatively regulates downstream Akt/mTOR/S6 signaling resulting in decreased cellular growth and proliferation. Co-injection of a lentivirus knocking Pten down with a control lentivirus allows us to compare the effects of Pten knockdown between individual neurons within the same animal. We find that knockdown of Pten results in neuronal hypertrophy by 21 days post-injection. This neuronal hypertrophy is correlated with increased p-S6 and p-mTOR in individual neurons. We used this system to test whether an environmental factor that has been implicated in cellular hypertrophy could influence the severity of the Pten knockdown-induced hypertrophy. Implantation of mini-osmotic pumps delivering fatty acids results in increased neuronal hypertrophy and p-S6/p-mTOR staining. These hypertrophic effects were reversed in response to rapamycin treatment. However, we did not observe a similar increase in hypertrophy in response to dietary manipulations of fatty acids. Thus, we conclude that by driving growth signaling with fatty acids and knocking down a critical regulator of growth, Pten, we are able to observe an additive morphological phenotype of increased soma size mediated by the mTOR pathway

Efficient photochemical synthesis of peptide-α-phenylthioesters

Low yields and substantial epimerization of peptide-α-thioesters often compromise the overall efficiency of native chemical ligation (NCL). Peptide arylthioesters are more reactive than peptide alkylthioesters in NCL, but are also more difficult to handle due to their propensity to hydrolyze, and are therefore often generated in situ. However, pre-prepared peptide arylthioesters are required for some NCL applications. Here we present a 7-nitroindoline-based photochemical method that generates protected peptide phenylthioesters under neutral reaction conditions via their activated esters from photoreactive peptide precursors in high isolated yields, and with low levels of epimerization. This method is fully compatible with Fmoc-strategy solid-phase peptide synthesis. Global deprotection with trifluoroacetic acid furnishes peptide phenylthioesters for NCL. Photoreactive peptide precursors can also be converted into their hydrazides in two steps by this method

Lunar regolith and structure mechanics

The topics are presented in viewgraph form and include the following: modeling of regolith-structure interaction in extraterrestrial constructed facilities; densification of lunar soil simulant; and vibration assisted penetration of lunar soil simulant

Genomic Fingerprints of Palaeogeographic History: The Tempo and Mode of Rift Tectonics Across Tropical Africa Has Shaped the Diversification of the Killifish Genus Nothobranchius (Teleostei: Cyprinodontiformes)

This paper reports a phylogeny of the African killifishes (Genus Nothobranchius, Order Cyprinodontiformes) informed by five genetic markers (three nuclear, two mitochondrial) of 80 taxa (seven undescribed and 73 of the 92 recognized species). These short-lived annual fishes occupy seasonally wet habitats in central and eastern Africa, and their distribution coincides largely with the East African Rift System (EARS). The fossil dates of sister clades used to constrain a chronometric tree of all sampled Nothobranchius recovered the origin of the genus at ~13.27 Mya. It was followed by the radiations of six principal clades through the Neogene. An ancestral area estimation tested competing biogeographical hypotheses to constrain the ancestral origin of the genus to the Nilo-Sudan Ecoregion, which seeded a mid-Miocene dispersal event into the Coastal ecoregion, followed closely (~10 Mya) by dispersals southward across the Mozambique coastal plain into the Limpopo Ecoregion. Extending westwards across the Tanzanian plateau, a pulse of radiations through the Pliocene were associated with dispersals and fragmentation of wetlands across the Kalahari and Uganda Ecoregions. We interpret this congruence of drainage rearrangements with dispersals and cladogenic events of Nothobranchius to reflect congruent responses to recurrent uplift and rifting. The coevolution of these freshwater fishes and wetlands is attributed to ultimate control by tectonics, as the EARS extended southwards during the Neogene. Geobiological consilience of the combined evidence supports a tectonic hypothesis for the evolution of Nothobranchius

Negative symptoms and impaired social functioning predict later psychosis in Latino youth at clinical high risk in the North American prodromal longitudinal studies consortium

AIM: Examining ethnically related variables in evaluating those at risk for psychosis is critical. This study investigated sociodemographic and clinical characteristics of Latino versus non-Latino clinical high-risk (CHR) subjects and healthy control (HC) subjects in the first North American Prodrome Longitudinal Study. METHODS: Fifty-six Latino CHR subjects were compared to 25 Latino HC and 423 non-Latino CHR subjects across clinical and demographic variables. Thirty-nine of the 56 CHR subjects completed at least one subsequent clinical evaluation over the 2.5-year period with 39% developing a psychotic illness. Characteristics of Latino CHR subjects who later converted to psychosis (‘converters’) were compared to those who did not (‘non-converters’). RESULTS: Latino CHR subjects were younger than non-Latino CHR subjects and had less education than Latino HC subjects and non-Latino CHR counterparts. Latino CHR converters had higher scores than Latino non-converters on the Structured Interview for Prodromal Syndromes total negative symptoms that were accounted for by decreased expression of emotion and personal hygiene/social attentiveness subsections. Latino CHR converters scored lower on the global functioning:social scale, indicating worse social functioning than Latino non-converters. CONCLUSION: Based on this sample, Latino CHR subjects may seek treatment earlier and have less education than non-Latino CHR subjects. Deficits in social functioning and impaired personal hygiene/social attentiveness among Latino CHR subjects predicted later psychosis and may represent important areas for future study. Larger sample sizes are needed to more thoroughly investigate the observed ethnic differences and risk factors for psychosis in Latino youth

Functional development in clinical high risk youth: Prediction of schizophrenia versus other psychotic disorders

This study evaluates premorbid social and academic functioning in clinical high-risk individuals as predictors of transition to schizophrenia versus another psychotic disorder. Participants were 54 individuals enrolled in phase one of the North American Prodrome Longitudinal Study who over two and a half years of follow-up met criteria for schizophrenia/schizophreniform disorder (n=28) or another psychotic disorder (n=26). Social and academic functioning in childhood, early adolescence, and late adolescence was assessed at baseline using the Cannon-Spoor Premorbid Adjustment Scale. Social maladjustment in late adolescence predicted significantly higher odds of transition to schizophrenia versus another psychotic disorder independent of childhood and early adolescent adjustment (OR = 4.02) and conveyed unique risk over academic maladjustment (O R= 5.64). Premorbid academic maladjustment was not associated with psychotic disorder diagnosis. Results support diagnostic specificity of premorbid social dysfunction to schizophrenia in clinical high-risk youth and underscore an important role for social maladjustment in the developmental pathology of schizophrenia and its prediction. (C) 2013 Elsevier Ireland Ltd. All rights reserved

An Individualized Risk Calculator for Research in Prodromal Psychosis

About 20–35% of individuals aged 12–30 years who meet criteria for a prodromal risk syndrome convert to psychosis within two years. However, this estimate ignores the fact that clinical high-risk (CHR) cases vary considerably in risk. Here we sought to create a risk calculator that can ascertain the probability of conversion to psychosis in individual patients based on profiles of risk indicators. The high risk category predicted by this calculator can inform research criteria going forward