Testing the chondrule-rich accretion model for planetary embryos using calcium isotopes

Understanding the composition of raw materials that formed the Earth is a crucial step towards understanding the formation of terrestrial planets and their bulk composition. Calcium is the fifth most abundant element in terrestrial planets and, therefore, is a key element with which to trace planetary composition. However, in order to use Ca isotopes as a tracer of Earth's accretion history, it is first necessary to understand the isotopic behavior of Ca during the earliest stages of planetary formation. Chondrites are some of the oldest materials of the Solar System, and the study of their isotopic composition enables understanding of how and in what conditions the Solar System formed. Here we present Ca isotope data for a suite of bulk chondrites as well as Allende (CV) chondrules. We show that most groups of carbonaceous chondrites (CV, CI, CR and CM) are significantly enriched in the lighter Ca isotopes ($\delta^{44/40}Ca$ = +0.1 to +0.93 permill) compared with bulk silicate Earth ($\delta^{44/40}Ca$ = +1.05 $\pm$ 0.04 permill, Huang et al., 2010) or Mars, while enstatite chondrites are indistinguishable from Earth in Ca isotope composition ($\delta^{44/40}Ca$ = +0.91 to +1.06 permill). Chondrules from Allende are enriched in the heavier isotopes of Ca compared to the bulk and the matrix of the meteorite ($\delta^{44/40}Ca$ = +1.00 to +1.21 permill). This implies that Earth and Mars have Ca isotope compositions that are distinct from most carbonaceous chondrites but that may be like chondrules. This Ca isotopic similarity between Earth, Mars, and chondrules is permissive of recent dynamical models of planetary formation that propose a chondrule-rich accretion model for planetary embryos.Comment: 39 pages, 5 figures, 2 tables 1 supplementary material (1 table

Silicon isotopes reveal recycled altered oceanic crust in the mantle sources of ocean island basalts

EP thanks the Chateaubriand STEM fellowship program for funding. FM thanks the European Research Council under the European Community’s H2020 framework program/ERC grant agreement #637503 (Pristine) and the Agence Nationale de la Recherche for a chaire d’Excellence Sorbonne Paris Cité (IDEX13C445) and for the UnivEarthS Labex program (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02). PS thanks the support of the Marie Curie FP7-IOF fellowship “Isovolc”.The study of silicon (Si) isotopes in Ocean Island Basalts (OIB) has the potential to discern between different models for the origins of geochemical heterogeneities in the mantle. Relatively large (∼several per mil per atomic mass unit) Si isotope fractionation occurs in low-temperature environments during biochemical and geochemical precipitation of dissolved Si, where the precipitate is preferentially enriched in the lighter isotopes relative to the dissolved Si. In contrast, only a limited range (∼tenths of a per mil) of Si isotope fractionation has been observed from high-temperature igneous processes. Therefore, Si isotopes may be useful as tracers for the presence of crustal material within OIB mantle source regions that experienced relatively low-temperature surface processes in a manner similar to other stable isotope systems, such as oxygen. Characterizing the isotopic composition of the mantle is also of central importance to the use of the Si isotope system as a basis for comparisons with other planetary bodies (e.g., Moon, Mars, asteroids). Here we present the first comprehensive suite of high-precision Si isotope data obtained by MC-ICP-MS for a diverse suite of OIB. Samples originate from ocean islands in the Pacific, Atlantic, and Indian Ocean basins and include representative end-members for the EM-1, EM-2, and HIMU mantle components. On average, δ30Si values for OIB (−0.32 ± 0.09‰, 2 sd) are in general agreement with previous estimates for the δ30Si value of Bulk Silicate Earth (−0.29 ± 0.07‰, 2 sd; Savage et al., 2014). Nonetheless, some small systematic variations are present; specifically, most HIMU-type (Mangaia; Cape Verde; La Palma, Canary Islands) and Iceland OIB are enriched in the lighter isotopes of Si (δ30Si values lower than MORB), consistent with recycled altered oceanic crust and lithospheric mantle in their mantle sources.PostprintPeer reviewe

Varied effects of algal symbionts on transcription factor NF-κB in a sea anemone and a coral: possible roles in symbiosis and thermotolerance

Many cnidarians, including the reef-building corals, undergo symbiotic mutualisms with photosynthetic dinoflagellate algae of the family Symbiodiniaceae. These partnerships are sensitive to temperature extremes, which cause symbiont loss and increased coral mortality. Previous studies have implicated host immunity and specifically immunity transcription factor NF-κB as having a role in the maintenance of the cnidarian-algal symbiosis. Here we have further investigated a possible role for NF-κB in establishment and loss of symbiosis in various strains of the anemone Exaiptasia (Aiptasia) and in the coral Pocillopora damicornis. Our results show that NF-κB expression is reduced in Aiptasia larvae and adults that host certain algae strains. Treatment of Aiptasia larvae with a known symbiosis-promoting cytokine, transforming growth factor β, also led to decreased NF-κB expression. We also show that aposymbiotic Aiptasia (with high NF-κB expression) have increased survival following infection with the pathogenic bacterium Serratia marcescens as compared to symbiotic Aiptasia (low NF-κB expression). Furthermore, a P. damicornis coral colony hosting Durusdinium spp. (formerly clade D) symbionts had higher basal NF-κB expression and decreased heat-induced bleaching as compared to two individuals hosting Cladocopium spp. (formerly clade C) symbionts. Lastly, genome-wide gene expression profiling and genomic promoter analysis identified putative NF-κB target genes that may be involved in thermal bleaching, symbiont maintenance, and/or immune protection in P. damicornis. Our results provide further support for the hypothesis that modulation of NF-κB and immunity plays a role in some, but perhaps not all, cnidarian-Symbiodiniaceae partnerships as well as in resistance to pathogens and bleaching.Accepted manuscrip

Generation and analysis of transcriptomic resources for a model system on the rise: the sea anemone Aiptasia pallida and its dinoflagellate endosymbiont

<p>Abstract</p> <p>Background</p> <p>The most diverse marine ecosystems, coral reefs, depend upon a functional symbiosis between cnidarian hosts and unicellular dinoflagellate algae. The molecular mechanisms underlying the establishment, maintenance, and breakdown of the symbiotic partnership are, however, not well understood. Efforts to dissect these questions have been slow, as corals are notoriously difficult to work with. In order to expedite this field of research, we generated and analyzed a collection of expressed sequence tags (ESTs) from the sea anemone <it>Aiptasia pallida </it>and its dinoflagellate symbiont (<it>Symbiodinium </it>sp.), a system that is gaining popularity as a model to study cellular, molecular, and genomic questions related to cnidarian-dinoflagellate symbioses.</p> <p>Results</p> <p>A set of 4,925 unique sequences (UniSeqs) comprising 1,427 clusters of 2 or more ESTs (contigs) and 3,498 unclustered ESTs (singletons) was generated by analyzing 10,285 high-quality ESTs from a mixed host/symbiont cDNA library. Using a BLAST-based approach to predict which unique sequences derived from the host versus symbiont genomes, we found that the contribution of the symbiont genome to the transcriptome was surprisingly small (1.6–6.4%). This may reflect low levels of gene expression in the symbionts, low coverage of alveolate genes in the sequence databases, a small number of symbiont cells relative to the total cellular content of the anemones, or failure to adequately lyse symbiont cells. Furthermore, we were able to identify groups of genes that are known or likely to play a role in cnidarian-dinoflagellate symbioses, including oxidative stress pathways that emerged as a prominent biological feature of this transcriptome. All ESTs and UniSeqs along with annotation results and other tools have been made accessible through the implementation of a publicly accessible database named AiptasiaBase.</p> <p>Conclusion</p> <p>We have established the first large-scale transcriptomic resource for <it>Aiptasia pallida </it>and its dinoflagellate symbiont. These data provide researchers with tools to study questions related to cnidarian-dinoflagellate symbioses on a molecular, cellular, and genomic level. This groundwork represents a crucial step towards the establishment of a tractable model system that can be utilized to better understand cnidarian-dinoflagellate symbioses. With the advent of next-generation sequencing methods, the transcriptomic inventory of <it>A. pallida </it>and its symbiont, and thus the extent of AiptasiaBase, should expand dramatically in the near future.</p

Attitudes to colorectal cancer screening among ethnic minority groups in the UK

Background: Colorectal screening by Flexible Sigmoidoscopy (FS) is under evaluation in the UK. Evidence from existing cancer screening programmes indicates lower participation among minority ethnic groups than the white-British population. To ensure equality of access, it is important to understand attitudes towards screening in all ethnic groups so that barriers to screening acceptance can be addressed.Methods: Open- and closed-ended questions on knowledge about colorectal cancer and attitudes to FS screening were added to Ethnibus (TM) - a monthly, nationwide survey of the main ethnic minority communities living in the UK (Indian, Pakistani, Bangladeshi, Caribbean, African, and Chinese). Interviews (n = 875) were conducted, face-to-face, by multilingual field-workers, including 125 interviews with white-British adults.Results: All respondents showed a notable lack of knowledge about causes of colorectal cancer, which was more pronounced in ethnic minority than white-British adults. Interest in FS screening was uniformly high (> 60%), with more than 90% of those interested saying it would provide 'peace of mind'. The most frequently cited barrier to screening 'in your community' was embarrassment, particularly among ethnic minority groups.Conclusion: Educational materials should recognise that non-white groups may be less knowledgeable about colorectal cancer. The findings of the current study suggest that embarrassment may be a greater deterrent to participation to FS screening among ethnic minority groups, but this result requires exploration in further research

Two Strategies for the Delivery of IPTc in an Area of Seasonal Malaria Transmission in The Gambia: A Randomised Controlled Trial

Bojang and colleagues report a randomized trial showing that delivery of intermittent preventive treatment for malaria in children by village health workers is more effective than delivery by reproductive and child health trekking clinics

Global wealth disparities drive adherence to COVID-safe pathways in head and neck cancer surgery

Peer reviewe

Repeated nebulisation of non-viral CFTR gene therapy in patients with cystic fibrosis:a randomised, double-blind, placebo-controlled, phase 2b trial

Background: Lung delivery of plasmid DNA encoding the CFTR gene complexed with a cationic liposome is a potential treatment option for patients with cystic fibrosis. We aimed to assess the efficacy of non-viral CFTR gene therapy in patients with cystic fibrosis. Methods: We did this randomised, double-blind, placebo-controlled, phase 2b trial in two cystic fibrosis centres with patients recruited from 18 sites in the UK. Patients (aged ≥12 years) with a forced expiratory volume in 1 s (FEV1) of 50–90% predicted and any combination of CFTR mutations, were randomly assigned, via a computer-based randomisation system, to receive 5 mL of either nebulised pGM169/GL67A gene–liposome complex or 0·9% saline (placebo) every 28 days (plus or minus 5 days) for 1 year. Randomisation was stratified by % predicted FEV1 (&lt;70 vs ≥70%), age (&lt;18 vs ≥18 years), inclusion in the mechanistic substudy, and dosing site (London or Edinburgh). Participants and investigators were masked to treatment allocation. The primary endpoint was the relative change in % predicted FEV1. The primary analysis was per protocol. This trial is registered with ClinicalTrials.gov, number NCT01621867. Findings: Between June 12, 2012, and June 24, 2013, we randomly assigned 140 patients to receive placebo (n=62) or pGM169/GL67A (n=78), of whom 116 (83%) patients comprised the per-protocol population. We noted a significant, albeit modest, treatment effect in the pGM169/GL67A group versus placebo at 12 months' follow-up (3·7%, 95% CI 0·1–7·3; p=0·046). This outcome was associated with a stabilisation of lung function in the pGM169/GL67A group compared with a decline in the placebo group. We recorded no significant difference in treatment-attributable adverse events between groups. Interpretation: Monthly application of the pGM169/GL67A gene therapy formulation was associated with a significant, albeit modest, benefit in FEV1 compared with placebo at 1 year, indicating a stabilisation of lung function in the treatment group. Further improvements in efficacy and consistency of response to the current formulation are needed before gene therapy is suitable for clinical care; however, our findings should also encourage the rapid introduction of more potent gene transfer vectors into early phase trials

The origin of volatile element depletion in early solar system material: Clues from Zn isotopes in chondrules

Volatile lithophile elements are depleted in the different planetary materials to various degrees, but the origin of these depletions is still debated. Stable isotopes of moderately volatile elements such as Zn can be used to understand the origin of volatile element depletions. Samples with significant volatile element depletions, including the Moon and terrestrial tektites, display heavy Zn isotope compositions (i.e. enrichment of Zn-66 vs. Zn-64), consistent with kinetic Zn isotope fractionation during evaporation. However, Luck et al. (2005) found a negative correlation between delta Zn-66 and 1/[Zn] between CI, CM, CO, and CV chondrites, opposite to what would be expected if evaporation caused the Zn abundance variations among chondrite groups. We have analyzed the Zn isotope composition of multiple samples of the major carbonaceous chondrite classes: CI (1), CM (4), CV (2), CO (4), CB (2), CH (2), CK (4), and CK/CR (1). The bulk chondrites define a negative correlation in a plot of delta Zn-66 vs 1/[Zn], confirming earlier results that Zn abundance variations among carbonaceous chondrites cannot be explained by evaporation. Exceptions are CB and CH chondrites, which display Zn systematics consistent with a collisional formation mechanism that created enrichment in heavy Zn isotopes relative to the trend defined by CI-CK. We further report Zn isotope analyses of chondrite components, including chondrules from Allende (CV3) and Mokoia (CV3), as well as an aliquot of Allende matrix. All chondrules are enriched in light Zn isotopes (similar to 500 ppm on Zn-66/Zn-64) relative to the bulk, contrary to what would be expected if Zn were depleted during evaporation, on the other hand the matrix has a complementary heavy isotope composition. We report sequential leaching experiments in un-equilibrated ordinary chondrites, which show sulfides are isotopically heavy compared to silicates and the bulk meteorite by ca. +0.65 per mil on Zn-66/Zn-64. We suggest isotopically heavy sulfides were removed from either chondrules or their precursors, thereby producing the light Zn isotope enrichments in chondrules. (C) 2017 The Author(s). Published by Elsevier B.V