550 research outputs found
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Correlated analyses of D- and 15N-rich carbon grains from CR2 chondrite EET 92042
Extract from introduction: Insoluble organic matter (IOM) and matrix from primitive carbonaceous chondrites carry isotope enrichments (?D?20000', ?15N?3200Γ―ΒΏΒ½) that are comparable to those in interplanetary dust particles [1, this work]. Hence, primitive organics that formed in the protosolar cloud (PSC) β or maybe in the cold outer regions of the protoplanetary disk β survived accretion and planetary processing on the asteroids, the parent bodies of the chondrites
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Correlated Microscale Isotope and Scanning Transmission X-Ray Analyses of Isotopically Anomalous Organic Matter from the CR2 Chondrite EET 92042
We discuss correlated examinations of organic matter from the CR2 chondrite EET 92042, using SIMS, STXM and other methods. We found a large, isotopically highly anomalous region of probable presolar origin that is C- and 13C-poor and 15N-rich
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Secondary ion mass spectrometry and x-ray absorption near-edge structure spectroscopy of isotopically anomalous organic matter from CR1 chondrites GRO 95577
We located interstellar organics from a CR1 chondrite with NanoSIMS and analyzed FIB-extracted sections with XANES. D-rich material appears not associated with a functional group, whereas 15N-rich matter shows some affinity to nitrile functionality
A novel hybrid material with calcium and strontium release capability
The preparation of PDMSβTEOSβCaO hybrid materials by solβgel techniques has been widely described in
previous works. Calcium nitrate is the most common source of calcium used in these preparations.
However, to remove possible toxic nitrate by-products a thermal treatment is necessary at temperatures
above 500 1C, which leads to the degradation of the polymeric components of the hybrids. Strontium has
already shown some promising results in the therapeutic area, being used in cases of osteoporosis and low
bone density. In this study a new potential bioactive hybrid material was prepared, by solβgel techniques,
using calcium acetate as a novel calcium source. Also, for the first time, incorporation of strontium in a
PDMSβTEOS hybrid system was evaluated. Samples were characterized before and after immersion in
Kokuboβs Simulated Body Fluid (SBF) by SEM, EDS, ICP and FT-IR spectroscopy
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Overview of the results of the organics PET Study of the cometary samples returned from comet Wild 2 by the Stardust mission
This presenation will provide an overview of the efforts and results produced by the Organics Preliminary Examination Team during their studies of the samples returned from comet Wild 2 by the Stardust spacecraft
The <i>Rosetta</i> Mission and the Chemistry of Organic Species in Comet 67P/ChuryumovβGerasimenko
Comets are regarded as probably the most primitive of solar system objects, preserving a record of the materials from which the solar system aggregated. Key amongst their components are organic compounds β molecules that may trace their heritage to the interstellar medium from which the protosolar nebula eventually emerged. The most recent cometary space mission, Rosetta, carried instruments designed to characterize, in unprecedented detail, the organic species in comet 67P/ChuryumovβGerasimenko (67P). Rosetta was the first mission to match orbits with a comet and follow its evolution over time, and also the first mission to land scientific instruments on a comet surface. Results from the mission revealed a greater variety of molecules than previously identified and indicated that 67P contained both primitive and processed organic entities
RASSF1AβLATS1 signalling stabilizes replication forks by restricting CDK2-mediated phosphorylation ofΒ BRCA2
Genomic instability is a key hallmark of cancer leading to tumour heterogeneity and therapeutic resistance. βBRCA2 has a fundamental role in error-free DNA repair but also sustains genome integrity by promoting βRAD51 nucleofilament formation at stalled replication forks. βCDK2 phosphorylates βBRCA2 (pS3291-βBRCA2) to limit stabilizing contacts with polymerized βRAD51; however, how replication stress modulates βCDK2 activity and whether loss of pS3291-βBRCA2 regulation results in genomic instability of tumours are not known. Here we demonstrate that the Hippo pathway kinase βLATS1 interacts with βCDK2 in response to genotoxic stress to constrain pS3291-βBRCA2 and support βRAD51 nucleofilaments, thereby maintaining genomic fidelity during replication stalling. We also show that βLATS1 forms part of an βATR-mediated response to replication stress that requires the tumour suppressor βRASSF1A. Importantly, perturbation of the βATRββRASSF1AββLATS1 signalling axis leads to genomic defects associated with loss of βBRCA2 function and contributes to genomic instability and βBRCA-nessβ in lung cancers
Defending the genome from the enemy within:mechanisms of retrotransposon suppression in the mouse germline
The viability of any species requires that the genome is kept stable as it is transmitted from generation to generation by the germ cells. One of the challenges to transgenerational genome stability is the potential mutagenic activity of transposable genetic elements, particularly retrotransposons. There are many different types of retrotransposon in mammalian genomes, and these target different points in germline development to amplify and integrate into new genomic locations. Germ cells, and their pluripotent developmental precursors, have evolved a variety of genome defence mechanisms that suppress retrotransposon activity and maintain genome stability across the generations. Here, we review recent advances in understanding how retrotransposon activity is suppressed in the mammalian germline, how genes involved in germline genome defence mechanisms are regulated, and the consequences of mutating these genome defence genes for the developing germline
The Ligand Binding Domain of GCNF Is Not Required for Repression of Pluripotency Genes in Mouse Fetal Ovarian Germ Cells
In mice, successful development and reproduction require that all cells, including germ cells, transition from a pluripotent to a differentiated state. This transition is associated with silencing of the pluripotency genes Oct4 and Nanog. Interestingly, these genes are repressed at different developmental timepoints in germ and somatic cells. Ovarian germ cells maintain their expression until about embryonic day (E) 14.5, whereas somatic cells silence them much earlier, at about E8.0. In both somatic cells and embryonic stem cells, silencing of Oct4 and Nanog requires the nuclear receptor GCNF. However, expression of the Gcnf gene has not been investigated in fetal ovarian germ cells, and whether it is required for silencing Oct4 and Nanog in that context is not known. Here we demonstrate that Gcnf is expressed in fetal ovarian germ cells, peaking at E14.5, when Oct4 and Nanog are silenced. However, conditional ablation of the ligand-binding domain of Gcnf using a ubiquitous, tamoxifen-inducible Cre indicates that Gcnf is not required for the down-regulation of pluripotency genes in fetal ovarian germ cells, nor is it required for initiation of meiosis and oogenesis. These results suggest that the silencing of Oct4 and Nanog in germ cells occurs via a different mechanism from that operating in somatic cells during gastrulation.Howard Hughes Medical InstituteNational Institutes of Health (U.S.) (2R01HG00257-20)National Human Genome Research Institute (U.S.) (2R01HG00257-20
External tagging does not affect the feeding behavior of a coral reef fish, Chaetodon vagabundus (Pisces: Chaetodontidae)
Author Posting. Β© The Author(s), 2009. This is the author's version of the work. It is posted here by permission of for personal use, not for redistribution. The definitive version was published in Environmental Biology of Fishes 86 (2009): 447-450, doi:10.1007/s10641-009-9545-9.Increasingly, the ability to recognize individual fishes is important for studies of population
dynamics, ecology, and behavior. Although a variety of methods exist, external tags remain one
of the most widely applied because they are both effective and cost efficient. However, a key
assumption is that neither the tagging procedure nor the presence of a tag negatively affects the
individual. While this has been demonstrated for relatively coarse metrics such as growth and
survival, few studies have examined the impact of tags and tagging on more subtle aspects of
behavior. We tagged adult vagabond butterflyfish (Chaetodon vagabundus) occupying a 30-ha
insular reef in Kimbe Bay, Papua New Guinea, using a commonly-utilized t-bar anchor tag. We
quantified and compared feeding behavior (bite rate), which is sensitive to stress, of tagged and
untagged individuals over four separate sampling periods spanning four months post-tagging.
Bite rates did not differ between tagged and untagged individuals at each sampling period and,
combined with additional anecdotal observations of normal pairing behavior and successful
reproduction, suggest that tagging did not adversely affect individuals.The authors gratefully
acknowledge funding from the Fulbright Program, National Science Foundation and the
Australian Research Council
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