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  • 1
    Publication Date: 2011-06-04
    Description: The first Cenozoic ice sheets initiated in Antarctica from the Gamburtsev Subglacial Mountains and other highlands as a result of rapid global cooling approximately 34 million years ago. In the subsequent 20 million years, at a time of declining atmospheric carbon dioxide concentrations and an evolving Antarctic circumpolar current, sedimentary sequence interpretation and numerical modelling suggest that cyclical periods of ice-sheet expansion to the continental margin, followed by retreat to the subglacial highlands, occurred up to thirty times. These fluctuations were paced by orbital changes and were a major influence on global sea levels. Ice-sheet models show that the nature of such oscillations is critically dependent on the pattern and extent of Antarctic topographic lowlands. Here we show that the basal topography of the Aurora Subglacial Basin of East Antarctica, at present overlain by 2-4.5 km of ice, is characterized by a series of well-defined topographic channels within a mountain block landscape. The identification of this fjord landscape, based on new data from ice-penetrating radar, provides an improved understanding of the topography of the Aurora Subglacial Basin and its surroundings, and reveals a complex surface sculpted by a succession of ice-sheet configurations substantially different from today's. At different stages during its fluctuations, the edge of the East Antarctic Ice Sheet lay pinned along the margins of the Aurora Subglacial Basin, the upland boundaries of which are currently above sea level and the deepest parts of which are more than 1 km below sea level. Although the timing of the channel incision remains uncertain, our results suggest that the fjord landscape was carved by at least two iceflow regimes of different scales and directions, each of which would have over-deepened existing topographic depressions, reversing valley floor slopes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Young, Duncan A -- Wright, Andrew P -- Roberts, Jason L -- Warner, Roland C -- Young, Neal W -- Greenbaum, Jamin S -- Schroeder, Dustin M -- Holt, John W -- Sugden, David E -- Blankenship, Donald D -- van Ommen, Tas D -- Siegert, Martin J -- England -- Nature. 2011 Jun 2;474(7349):72-5. doi: 10.1038/nature10114.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758, USA. duncan@utig.ig.utexas.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21637255" target="_blank"〉PubMed〈/a〉
    Keywords: Antarctic Regions ; *Climate Change ; Geography ; *Ice Cover/chemistry ; Oceans and Seas ; Oxygen Isotopes/analysis
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1995-11-03
    Description: Males with X-linked severe combined immunodeficiency (XSCID) have defects in the common cytokine receptor gamma chain (gamma c) gene that encodes a shared, essential component of the receptors of interleukin-2 (IL-2), IL-4, IL-7, IL-9, and IL-15. The Janus family tyrosine kinase Jak3 is the only signaling molecule known to be associated with gamma c, so it was hypothesized that defects in Jak3 might cause an XSCID-like phenotype. A girl with immunological features indistinguishable from those of XSCID was therefore selected for analysis. An Epstein-Barr virus (EBV)-transformed cell line derived from her lymphocytes had normal gamma c expression but lacked Jak3 protein and had greatly diminished Jak3 messenger RNA. Sequencing revealed a different mutation on each allele: a single nucleotide insertion resulting in a frame shift and premature termination in the Jak3 JH4 domain and a nonsense mutation in the Jak3 JH2 domain. The lack of Jak3 expression correlated with impaired B cell signaling, as demonstrated by the inability of IL-4 to activate Stat6 in the EBV-transformed cell line from the patient. These observations indicate that the functions of gamma c are dependent on Jak3 and that Jak3 is essential for lymphoid development and signaling.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Russell, S M -- Tayebi, N -- Nakajima, H -- Riedy, M C -- Roberts, J L -- Aman, M J -- Migone, T S -- Noguchi, M -- Markert, M L -- Buckley, R H -- O'Shea, J J -- Leonard, W J -- M01-RR30/RR/NCRR NIH HHS/ -- R37AI18613-13/AI/NIAID NIH HHS/ -- T32 CA09058/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1995 Nov 3;270(5237):797-800.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health (NIH), Bethesda, MD 20892, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7481768" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; B-Lymphocytes/*immunology ; Base Sequence ; Cell Line, Transformed ; Female ; Frameshift Mutation ; Genetic Linkage ; Humans ; Infant ; Interleukin-4/pharmacology ; Janus Kinase 3 ; Molecular Sequence Data ; Phenotype ; Point Mutation ; Protein-Tyrosine Kinases/deficiency/genetics/*physiology ; RNA, Messenger/genetics/metabolism ; Receptors, Interleukin/physiology ; STAT6 Transcription Factor ; Severe Combined Immunodeficiency/*enzymology/genetics/immunology ; Signal Transduction ; T-Lymphocytes/*immunology ; Trans-Activators/metabolism ; X Chromosome
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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