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  • tau  (2)
  • Al3+  (1)
  • Springer  (3)
  • American Geophysical Union (AGU)
  • American Institute of Physics
  • 1995-1999  (2)
  • 1990-1994  (1)
  • 1905-1909
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Publisher
  • Springer  (3)
  • American Geophysical Union (AGU)
  • American Institute of Physics
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  • 1995-1999  (2)
  • 1990-1994  (1)
  • 1905-1909
  • 2000-2004  (1)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 134 (1991), S. 167-178 
    ISSN: 1573-5036
    Keywords: Al3+ ; aluminium ; hydroxy-aluminium ; phytotoxicity ; polynuclear aluminium ; rhizotoxicity ; roots ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aluminium (III) released from soil minerals to the soil solution under acid conditions may appear as hexaaquaaluminium (Al(H2O)6 3+, or Al3+ for convenience) or may react with available ligands to form additional chemical species. That one or more of these species is rhizotoxic (inhibitory to root elongation) has been known for many decades, but the identity of the toxic species remains problematical for the following reasons. 1. Several Al species coexist in solution so individual species cannot be investigated in isolation, even in artificial culture media. 2. The activities of individual species must be calculated from equilibrium data that may be uncertain. 3. The unexpected or undetected appearance of the extremely toxic triskaidekaaluminium (AlO4Al12(OH)24(H2O)12 7+ or Al13) may cause misatribution of toxicity to other species, especially to mononuclear hydroxy-Al. 4. If H+ ameliorates Al3+ toxicity, or vice versa, then mononuclear hydroxy-Al may appear to be toxic when it is not. 5. The identity and activities of the Al species contacting the cell surfaces are uncertain because of the H+ currents through the root surface and because of surface charges. This article considers the implications of these problems for good experimental designs and critically evaluates current information regarding the relative toxicities of selected Al species. It is concluded that polycationic Al (charge 〉2) is rhizotoxic as are other polyvalent cations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 223-233 
    ISSN: 1573-6830
    Keywords: tau ; kinases ; signal transduction ; Alzheimer's disease ; phosphorylation ; paired helical filaments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The individual and sequential influence of protein kinase C (PKC), protein kinase A (PKA) and mitogen-activated protein kinase (MAP kinase) on human brain tau was examined. 2. A range of PKC concentrations generated certain phosphoepitopes common with paired helical filaments. These epitopes were masked by higher PKC concentrations, suggesting the presence of multiple tau phosphorylation sites for which PKC exhibited differing affinities and/or conformational alterations in tau induced by sequential PKC-mediated phosphorylation. 3. Prior phosphorylation by PKC enhanced the nature and extent of AD-like tau antigenicity generated by subsequent incubation with MAP kinase yet inhibited that generated by subsequent incubation with PKA. 4. Dephosphorylation of tau prior to incubation with kinases significantly altered the influence of individual and multiple kinase incubation on tau antigenicity in a site-specific manner, indicating that prior in situ phosphorylation events markedly influenced subsequent cell-free phosphorylation. 5. In addition to considerations of the potential impact of tau phosphorylation by individual kinases, these findings extend previous studies which indicate that tau antigenicity, and, presumably, its behavior in situ, is influenced by the sequential and convergent influences of multiple kinases.
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  • 3
    ISSN: 1573-6830
    Keywords: MAP kinase ; tau ; protein kinase C ; wortmannin ; PD98059 ; neuroblastoma ; Alzheimer's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitogen-activated protein (MAP) kinase phosphorylates tau in cell-free analyses, but whether or not it does so within intact cells remains controversial. In the present study, microinjection of MAP kinase into SH-SY-5Y human neuroblastoma cells increased tau immunoreactivity toward the phosphodependent antibodies PHF-1 and AT-8. In contrast, treatment with a specific inhibitor of MAP kinase (PD98059) did not diminish “basal” levels of these immunoreactivities in otherwise untreated cells. These findings indicate that hyperactivation of MAP kinase increases phospho-tau levels within cells, despite that MAP kinase apparently does not substantially influence intracellular tau phosphorylation under normal conditions. These findings underscore that results obtained following inhibition of kinase activities do not necessarily provide an indication of the consequences accompanying hyperactivation of that same kinase. Several studies conducted in cell-free systems indicate that exposure of tau to multiple kinases can have synergistic effects on the nature and extent of tau phosphorylation. We therefore examined whether or not such effects could be demonstrated within these cells. Site-specific phospho-tau immunoreactivity was increased in additive and synergistic manners by treatment of injected cells with TPA (which activates PKC), calcium ionophore (which activates calcium-dependent kinases), and wortmannin (which inhibits PIP3 kinase). Alteration in total tau levels was insufficient to account for the full extent of the increase in phospho-tau immunoreactivity. These additional results indicate that multiple kinase activities modulate the influence of MAP kinase on tau within intact cells.
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