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  • Proceedings of the National Academy of Sciences  (3)
  • 1
    Online Resource
    Online Resource
    Highly restricted near‐surface permafrost extent during the mid-Pliocene warm period
    Proceedings of the National Academy of Sciences ; 2023
    In:  Proceedings of the National Academy of Sciences Vol. 120, No. 36 ( 2023-09-05)
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 120, No. 36 ( 2023-09-05)
    Abstract: Accurate understanding of permafrost dynamics is critical for evaluating and mitigating impacts that may arise as permafrost degrades in the future; however, existing projections have large uncertainties. Studies of how permafrost responded historically during Earth’s past warm periods are helpful in exploring potential future permafrost behavior and to evaluate the uncertainty of future permafrost change projections. Here, we combine a surface frost index model with outputs from the second phase of the Pliocene Model Intercomparison Project to simulate the near‐surface (~3 to 4 m depth) permafrost state in the Northern Hemisphere during the mid-Pliocene warm period (mPWP, ~3.264 to 3.025 Ma). This period shares similarities with the projected future climate. Constrained by proxy-based surface air temperature records, our simulations demonstrate that near‐surface permafrost was highly spatially restricted during the mPWP and was 93 ± 3% smaller than the preindustrial extent. Near‐surface permafrost was present only in the eastern Siberian uplands, Canadian high Arctic Archipelago, and northernmost Greenland. The simulations are similar to near‐surface permafrost changes projected for the end of this century under the SSP5-8.5 scenario and provide a perspective on the potential permafrost behavior that may be expected in a warmer world.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.2301954120
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Implanted adipose progenitor cells as physicochemical regulators of breast cancer
    Proceedings of the National Academy of Sciences ; 2012
    In:  Proceedings of the National Academy of Sciences Vol. 109, No. 25 ( 2012-06-19), p. 9786-9791
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 109, No. 25 ( 2012-06-19), p. 9786-9791
    Abstract: Multipotent adipose-derived stem cells (ASCs) are increasingly used for regenerative purposes such as soft tissue reconstruction following mastectomy; however, the ability of tumors to commandeer ASC functions to advance tumor progression is not well understood. Through the integration of physical sciences and oncology approaches we investigated the capability of tumor-derived chemical and mechanical cues to enhance ASC-mediated contributions to tumor stroma formation. Our results indicate that soluble factors from breast cancer cells inhibit adipogenic differentiation while increasing proliferation, proangiogenic factor secretion, and myofibroblastic differentiation of ASCs. This altered ASC phenotype led to varied extracellular matrix (ECM) deposition and contraction thereby enhancing tissue stiffness, a characteristic feature of breast tumors. Increased stiffness, in turn, facilitated changes in ASC behavior similar to those observed with tumor-derived chemical cues. Orthotopic mouse studies further confirmed the pathological relevance of ASCs in tumor progression and stiffness in vivo. In summary, altered ASC behavior can promote tumorigenesis and, thus, their implementation for regenerative therapy should be carefully considered in patients previously treated for cancer.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1121160109
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2012
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Early evolutionary loss of the lipid A modifying enzyme PagP resulting in innate immune evasion in Yersinia pestis
    Proceedings of the National Academy of Sciences ; 2020
    In:  Proceedings of the National Academy of Sciences Vol. 117, No. 37 ( 2020-09-15), p. 22984-22991
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 117, No. 37 ( 2020-09-15), p. 22984-22991
    Abstract: Immune evasion through membrane remodeling is a hallmark of Yersinia pestis pathogenesis. Yersinia remodels its membrane during its life cycle as it alternates between mammalian hosts (37 °C) and ambient (21 °C to 26 °C) temperatures of the arthropod transmission vector or external environment. This shift in growth temperature induces changes in number and length of acyl groups on the lipid A portion of lipopolysaccharide (LPS) for the enteric pathogens Yersinia pseudotuberculosis ( Ypt ) and Yersinia enterocolitica ( Ye ), as well as the causative agent of plague, Yersinia pestis ( Yp ). Addition of a C16 fatty acid (palmitate) to lipid A by the outer membrane acyltransferase enzyme PagP occurs in immunostimulatory Ypt and Ye strains, but not in immune-evasive Yp . Analysis of Yp pagP gene sequences identified a single-nucleotide polymorphism that results in a premature stop in translation, yielding a truncated, nonfunctional enzyme. Upon repair of this polymorphism to the sequence present in Ypt and Ye , lipid A isolated from a Yp pagP+ strain synthesized two structures with the C16 fatty acids located in acyloxyacyl linkage at the 2′ and 3′ positions of the diglucosamine backbone. Structural modifications were confirmed by mass spectrometry and gas chromatography. With the genotypic restoration of PagP enzymatic activity in Yp , a significant increase in lipid A endotoxicity mediated through the MyD88 and TRIF/TRAM arms of the TLR4-signaling pathway was observed. Discovery and repair of an evolutionarily lost lipid A modifying enzyme provides evidence of lipid A as a crucial determinant in Yp infectivity, pathogenesis, and host innate immune evasion.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1917504117
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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