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  • 1
    Electronic Resource
    Electronic Resource
    Natural variants of human p85α phosphoinositide 3-kinase in severe insulin resistance: a novel variant with impaired insulin-stimulated lipid kinase activity (2000)
    Springer
    Diabetologia 43 (2000), S. 321-331 
    Details
    ISSN: 1432-0428
    Keywords: Keywords Keywords Genetics, insulin signalling, phosphatidylinositol 3-kinase.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. Phosphoinositide 3-kinase (PI 3K) plays a central part in the mediation of insulin-stimulated glucose disposal. No genetic studies of this enzyme in human syndromes of severe insulin resistance have been previously reported.¶Methods. Phosphoinositide 3-kinase p85α regulatory subunit cDNA was examined in 20 subjects with syndromes of severe insulin resistance by single strand conformational polymorphism and restriction fragment length polymorphism analyses. Insulin-stimulated phosphoinositide 3-kinase activity and recruitment into phosphotyrosine complexes of variants of p85α were studied in transiently transfected HEK293 cells. Phosphopeptide binding characteristics of wild-type and mutant p85α-GST fusion proteins were examined by surface plasmon resonance.¶Results. The common p85α variant, Met326I1e, was identified in 9 of the 20 subjects. Functional studies of the Met326Ile variant showed it to have equivalent insulin-stimulated lipid kinase activity and phosphotyrosine recruitment as wild-type p85α. A novel heterozygous mutation, Arg409Gln, was detected in one subject. Within the proband's family, carriers of the mutation had a higher median fasting plasma insulin (218 pmol/l) compared with wild-type relatives (72 mol/l) (n = 8 subjects, p = 0.06). The Arg409Gln p85α subunit was associated with lower insulin-stimulated phosphoinositide 3-kinase activity compared with wild-type (mean reduction 15 %, p 〈 0.05, n = 5). The recruitment of Arg409Gln p85α into phosphotyrosine complexes was not significantly impaired. GST fusion proteins of wild-type and mutant p85α showed identical binding to phosphopeptides in surface plasmon resonance studies.¶Conclusion/interpretation. Mutations in p85α are uncommon in subjects with syndromes of severe insulin resistance. The Met326Ile p85α variant appears to have no functional effect on the insulin-stimulated phosphoinositide 3-kinase activity. The impaired phosphoinositide 3-kinase activity of the Arg409Gln mutant suggests that it could contribute to the insulin resistance seen in this family. [Diabetologia (2000) 43: 321–331]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250050050
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  • 2
    Electronic Resource
    Electronic Resource
    Holocene accumulation of organic carbon at the Laptev Sea continental margin (Arctic Ocean): sources, pathways, and sinks (2000)
    Springer
    Geo-marine letters 20 (2000), S. 27-36 
    Details
    ISSN: 1432-1157
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Composition and accumulation rates of organic carbon in Holocene sediments provided data to calculate an organic carbon budget for the Laptev Sea continental margin. Mean Holocene accumulation rates in the inner Laptev Sea vary between 0.14 and 2.7 g C cm−2 ky−1; maximum values occur close to the Lena River delta. Seawards, the mean accumulation rates decrease from 0.43 to 0.02 g C cm−2 ky−1. The organic matter is predominantly of terrigenous origin. About 0.9 × 106 t year−1 of organic carbon are buried in the Laptev Sea, and 0.25 × 106 t year−1 on the continental slope. Between about 8.5 and 9 ka, major changes in supply of terrigenous and marine organic carbon occur, related to changes in coastal erosion, Siberian river discharge, and/or Atlantic water inflow along the Eurasian continental margin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003670000028
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  • 3
    Electronic Resource
    Electronic Resource
    Variability of river discharge and Atlantic-water inflow at the Laptev Sea continental margin during the past 15,000 years: implications from maceral and biomarker records (2000)
    Springer
    International journal of earth sciences 89 (2000), S. 578-591 
    Details
    ISSN: 1437-3262
    Keywords: Organic-carbon source Organic petrology Biomarker Arctic Ocean Laptev Sea Last Glacial Holocene Termination 1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract. In order to reconstruct the depositional environment from the Laptev Sea continental slope and shelf during the past ~15,000 years BP maceral analysis was carried out on two sediment cores (PS2458-4, PS2725-5) and compared with organic-geochemical parameters. During the transition from the Last Glacial to the Holocene the environment of the Laptev Sea shelf was controlled by the post-glacial sea level rise, variations in river discharge, surface-water productivity, and Atlantic-water inflow along the Eurasian continental margin. Based on our results, we identify the following significant changes of the environment: (a) at approximately 13,500 years BP the first step of deglaciation (Termination 1a) is documented by the deposition of marine and fresh-water organic matter; (b) at approximately 10,400 years BP the first post-glacial influence of Atlantic-water inflow along the Eastern Laptev Sea continental margin is indicated by an increase in marine organic matter; (c) at the beginning of the Holocene an increased fluvial supply is documented by an increase in fresh-water alginite; and (d) since ~9500–8000 years BP modern marine conditions are established at the Laptev Sea continental margin as documented in increased amounts of marine macerals, biomarkers (dinosterol, brassicasterol, short-chain fatty acids), and dinoflagellate cysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310000111
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  • 4
    Electronic Resource
    Electronic Resource
    Modern river discharge and pathways of supplied material in the Eurasian Arctic Ocean: evidence from mineral assemblages and major and minor element distribution (2000)
    Springer
    International journal of earth sciences 89 (2000), S. 486-495 
    Details
    ISSN: 1437-3262
    Keywords: Arctic Ocean Laptev Sea Kara Sea Heavy minerals Clay minerals Chemical elements Sources of sediment Transport pathways of sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract. Clay-mineral, heavy-mineral, and elemental distributions in sediments from the Arctic Ocean and the adjacent Laptev and Kara seas can be attributed to the geology of the hinterland and the transport of terrigenous material by rivers onto the shelves. Kara Sea sediments are characterized by increased contents of smectite and elevated Ni/Al-, Ti/Al-, and Cr/Al ratios. In the western Laptev Sea sediments are enriched in smectite and clinopyroxene and increased in Ti/Al-, Cr/Al-, and Ca/Al ratios. The composition of the sediments reflects suspended matter input from the large trap basalt of the Putoran Mountains. The eastern Laptev Sea sediments display increased illite and amphibole contents as well as a chemical composition similar to average shale. This composition is due to the discharge from the Lena and Yana rivers, which drain a large catchment area consisting of sedimentary Mesozoic and Paleozoic rocks. Material from the eastern Laptev Sea is transported by ocean currents and sediment-laden sea ice along the Transpolar Drift into the central Arctic Ocean. This is indicated by similar values of Ti/Al-, Cr/Al-, Rb/Al-, and K/Al ratios as well as increased concentrations of amphibole and illite, determined in sediments from the Lomonosov Ridge. A minor input from the Beaufort Sea into the central Arctic Ocean is suggested from increased Ca/Al ratios and increased contents of opaque minerals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310000120
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  • 5
    Electronic Resource
    Electronic Resource
    Structural Development During Thermal Fractionation of Polyethylenes (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 245-255 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; metallocene ; polyethylenes ; SAXS ; synchrotron radiation ; thermal fractionation ; WAXD ; Ziegler-Natta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study, the stepwise isothermal crystallization or thermal fractionation of Ziegler—Natta and metallocene based polyethylenes (ZN-PE and m-PE) with two kinds of branch lengths (ethyl and hexyl) and branch compositions were studied using simultaneous synchrotron small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystal long period and the invariant were determined by SAXS, and the variations of crystal unit cell parameters and the degree of crystallinity were determined by WAXD. The arithmetic mean length (Ln), the weightedmean length (Lw) and the broadness index (Lw/Ln) of the studied polyethylenes were previously determined by DSC. Results from these studies were interpreted using the model of branch exclusion, which affects the ability of the chain-reentry into the crystal phase. Multiple SAXS peaks and step-change in crystallinity change (WAXD) were seen during heating, which corresponded well with the crystal thickness distribution induced by stepwise crystallization. The effects of the heterogeneity of the 1-olefin branch length and the distribution on the crystal long period and the invariant as well as the degree of crystallinity were discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010100432613
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