170 research outputs found

    Nueva Cadiz Beads in the Americas: A Preliminary Compositional Comparison

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    Nueva Cadiz and associated beads are among the earliest categories of European glass beads found in the Americas. Named after the site in Venezuela where they were first identified, these tubular, square-sectioned beads occur in regions of 16th-century Spanish colonial trade. A similar style occurs around Lake Ontario in northeastern North America in areas of 17th-century Dutch and French colonial trade. We compare the chemical composition of beads from South America and Ontario, Canada, to explore their provenience and technology. Differences in key trace elements (Hf, Zr, Nd) strongly indicate separate sand origins for the two bead groups. Comparison with soda-lime glass made in Venice and Antwerp reveals chemical similarities between the South American beads and Venetian glass, and between the Ontario beads and Antwerp glass. The analysis also sheds light on beadmaking technologies

    Exosome-mediated MIR211 modulates tumor microenvironment via the DUSP6-ERK5 axis and contributes to BRAFV600E inhibitor resistance in melanoma

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    The microRNA MIR211 is an important regulator of melanoma tumor cell behavior. Previous studies suggested that in certain tumors, MIR211 acted as a tumor suppressor while in others it behaved as an oncogenic regulator. When MIR211 is expressed in BRAFV600E-mutant A375 melanoma cells in mouse xenografts, it promotes aggressive tumor growth accompanied by increased cellular proliferation and angiogenesis. We demonstrate that MIR211 is transferred to adjacent cells in the tumor micro-environment via exosomes. Cross-species genome-wide transcriptomic analysis showed that human tumor-derived MIR211 interacts with the mouse transcriptome in the tumor microenvironment, and activates ERK5 signaling in human tumor cells via the modulation of a feedback loop. Human miR211 directly inhibits human DUSP6 protein phosphatase at the post-transcriptional level. We provide support for the hypothesis that DUSP6 inhibition conferred resistance of the human tumor cells to the BRAF inhibitor vemurafenib and to the MEK inhibitor cobimetinib, with associated increases in ERK5 phosphorylation. These findings are consistent with a model in which MIR211 regulates melanoma tumor proliferation and BRAF inhibitor resistance by inducing ERK5 signaling within the complex tumor microenvironment. We propose that the MIR211-ERK5 axis represents an important and sensitive regulatory arm in melanoma with potential theranostic applications

    Exosome-mediated MIR211 modulates tumor microenvironment via the DUSP6-ERK5 axis and contributes to BRAFV600E inhibitor resistance in melanoma

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    The microRNA MIR211 is an important regulator of melanoma tumor cell behavior. Previous studies suggested that in certain tumors, MIR211 acted as a tumor suppressor while in others it behaved as an oncogenic regulator. When MIR211 is expressed in BRAFV600E-mutant A375 melanoma cells in mouse xenografts, it promotes aggressive tumor growth accompanied by increased cellular proliferation and angiogenesis. We demonstrate that MIR211 is transferred to adjacent cells in the tumor micro-environment via exosomes. Cross-species genome-wide transcriptomic analysis showed that human tumor-derived MIR211 interacts with the mouse transcriptome in the tumor microenvironment, and activates ERK5 signaling in human tumor cells via the modulation of a feedback loop. Human miR211 directly inhibits human DUSP6 protein phosphatase at the post-transcriptional level. We provide support for the hypothesis that DUSP6 inhibition conferred resistance of the human tumor cells to the BRAF inhibitor vemurafenib and to the MEK inhibitor cobimetinib, with associated increases in ERK5 phosphorylation. These findings are consistent with a model in which MIR211 regulates melanoma tumor proliferation and BRAF inhibitor resistance by inducing ERK5 signaling within the complex tumor microenvironment. We propose that the MIR211-ERK5 axis represents an important and sensitive regulatory arm in melanoma with potential theranostic applications

    Taxonomy of the family Arenaviridae and the order Bunyavirales : update 2018

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    In 2018, the family Arenaviridae was expanded by inclusion of 1 new genus and 5 novel species. At the same time, the recently established order Bunyavirales was expanded by 3 species. This article presents the updated taxonomy of the family Arenaviridae and the order Bunyavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV) and summarizes additional taxonomic proposals that may affect the order in the near future.Peer reviewe

    The influence of large bolide impacts on Earth's carbon cycle

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    Human society's rapid release of vast quantities of CO2 into the atmosphere is a significant planetary experiment. An obvious natural process capable of similar emissions over geologically short time spans are very large bolide impacts. When striking a carbon-rich target, bolides significantly, and potentially catastrophically, disrupt the global biogeochemical carbon cycle. Independent factors, such as sulfur-rich targets, redox state of the oceans or encountering ecosystems already close to a tipping point, dictated the magnitude of further consequences and determined which large bolide strikes shaped Earth's evolution. On the early Earth, where carbon-rich sedimentary targets were rare, impacts may not have been purely destructive. Instead, enclosed subaqueous impact structures may have contributed to initiating Earth's unique carbon cycle.</p

    New insights into Paleoproterozoic surficial conditions revealed by 1.85 Ga corestone-rich saprolith

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    Spheroidally weathered corestones, which are remnant pieces of bedrock surrounded by progressively weathered saprolite, preserve an ideal, small-scale natural interface for examining incipient to intermediate weathering reactions. Ancient corestones are preserved in some Precambrian paleosols but have remained surprisingly understudied. Here detailed mineral-chemical trends are examined across corestone-saprolith interfaces in ca. 1.85 Ga dolerite-hosted paleosol from the Flin Flon-Creighton area (Manitoba and Saskatchewan, Canada). The study presents the first comprehensive paleo-redox tracer suite (Fe-Mn-Mo-U-V-Cr-Ce) for the classic Flin Flon paleosol, which formed during a crucial period in the Paleoproterozoic for which marine sedimentary archives infer a return to low oxygen levels after the Great Oxidation Event (GOE). The textural and mineralogical progression across corestone-saprolith interfaces documented with petrography and scanning electron microscope-mineral liberation analysis (SEM-MLA) show many features (e.g., development of weathering rindlets and solution channels) strikingly reminiscent of modern mafic rock-hosted saprolite, despite later overprint. Albite-dominated cores preferentially preserving carbonate and sulfide (pyrite, chalcopyrite) are progressively altered outwards to a finer-grained saprolith rich in chlorite, illite, and muscovite, with embaying rindlets bearing cryptocrystalline hematite-quartz-illite. These mineral-textural observations guided sub-sampling for bulk Fe(II) and solution ICP-MS ultra-trace and major element analysis, and mineral-scale LA-ICP-MS analysis. Many high-field-strength elements (Al, Ti, Zr, Nb, Hf, Ta, and Th), remained immobile across the interface and ascertain the homogeneity of the parent dolerite. Progressive weathering from corestone to saprolith was quantified with chemical index of alteration minus K (CIA-K) values that fall into three zones (incipient (1): 45‚Äď55; modest (2): 55‚Äď65; and moderate (3): 65‚Äď75). Mass balance and spatial geochemical analysis revealed the following features: outward migration of Fe(II) and Mn from corestone to saprolith, with partial oxidation of Fe(II) to Fe(III) in rindlets; minimal REE mobility with no pronounced Ce anomalies, but well-developed, unidirectional Y/Ho fractionation; significant Cr and V mobility from corestones outwards with enrichment in saprolith; minimal dm-scale cycling and limited loss of Mo and U from saprolith; and post-depositional enrichment of K, Rb, Cs, Tl, Ba, Be, and W. Using semi-quantitative LA-ICP-MS elemental maps, it was possible to contextualize the mineralogical controls on chemical weathering reactions. Iron, Mg, and Mn are coupled within chlorite (representing former pedogenic phyllosilicates), which also scavenged Cr. The REEs are predominantly hosted by apatite and titanite. The Ti-phases ilmenite and titanite are the predominant U- and Mo-bearing hosts. Collectively, the insights from the Flin Flon paleosol converge with those from other ca. 1.90‚Äď1.85 Ga terrestrial and marine deposits in inferring an oxygen-limited atmosphere capable of efficiently oxidizing Fe and S, but not Mn, in terrestrial environments. The Cr and V distributions are most consistent with small-scale solubilization and redeposition that appears to be linked to the weatherability of protolith minerals and locally-generated acid- and/or ligand-rich conditions rather than oxidation. Although normally sensitive indicators of oxidative weathering, the inhibited release of Mo and U from the corestone was instead primarily dictated by the weathering resistance of their host minerals. Oxygen-limited weathering in saprolite supplied sulfate to the oceans, but the continental flux of redox-sensitive trace elements from this zone as well as more weathered substrates was limited, ultimately contributing to sustaining a largely redox-dynamic, weakly buffered, and nutrient-limited ocean.</p

    An Image Mapping Approach to U-Pb LA-ICP-MS Carbonate Dating and Applications to Direct Dating of Carbonate Sedimentation

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    We present a new approach to laser ablation inductively coupled plasma mass spectrometry (LA‚ÄźICP‚ÄźMS) U‚ÄźPb dating of carbonates based on selection and pooling of pixels from 2‚ÄźD elemental and isotopic ratio maps. This image mapping technique is particularly useful for targeting subdomains in samples with complex geological histories. Key major and trace elements that are sensitive to detrital components, postformational fluid ingress, mineralogical changes, or diagenetic overprinting are measured along with the Pb and U isotopic data. Laser sampling is undertaken along successive linear rasters that are compiled into maps using the Monocle add‚Äźon for Iolite, with one pixel in the map corresponding to one time slice of the time‚Äźresolved signal. These element, element ratio, and isotope ratio maps can be overlain over photomicrographs or scanning electron microscopy images to spatially link compositional data to textural and structural features. The pixels corresponding to likely homogeneous age domains can be isolated by applying appropriate selection criteria (e.g., Th < 0.3 ppm, Mg/Ca < 0.004) and pooled into pseudo‚Äźanalyses using a proxy for the parent/daughter ratio (e.g., 207Pb/235U, 238U/208Pb) to retrieve the largest possible spread of the data points on isochron diagrams. The approach is best suited for analytical setups capable of rapidly or simultaneously scanning over a large mass range and can yield a precision of ¬Ī1% or better on quadrupole instruments depending on U concentration, 238U/204Pb, and age of the sample. The sample‚Äźspecific filtering criteria for selection and rejection of data and their rationale can be reported, resulting in more transparency with regard to data processing
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