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  • Blackwell Science Ltd.  (1)
  • Blackwell Science Pty  (1)
  • 2000-2004  (2)
  • 2000  (2)
  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Oxidative stress induced by acute complex I inhibition with 1-methyl-4-phenylpyridinium ion activated biphasically the stress-activated c-Jun N-terminal kinase (JNK) and the early transcription factor nuclear factor-κB (NF-κB) in SH-SY5Y neuroblastoma cells. Early JNK activation was dependent on mitochondrial adenine nucleotide translocator (ANT) activity, whereas late-phase JNK activation and the cleavage of signaling proteins Raf-1 and mitogen-activated protein kinase (MAPK) kinase (MEK) kinase (MEKK)-1 appeared to be ANT-independent. Early NF-κB activation depended on MEK, later activation required an intact electron transport chain (ETC), and Parkinson's disease (PD) cybrid (mitochondrial transgenic cytoplasmic hybrid) cells had increased basal NF-κB activation. Mitochondria appear capable of signaling ETC impairment through MAPK modules and inducing protective NF-κB responses, which are increased by PD mitochondrial genes amplified in cybrid cells. Irreversible commitment to apoptosis in this cell model may derive from loss of Raf-1 and cleavage/activation of MEKK-1, processes reported in other models to be caspase-mediated. Therapeutic strategies that reduce mitochondrial activation of proapoptotic MAPK modules, i.e., JNK, and enhance survival pathways, i.e., NF-κB, may offer neuroprotection in this debilitating disease.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1442-1984
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Discovering how biological diversification results in species is one of the primary challenges facing evolutionary biologists. In the ferns, evidence indicates that dissimilar speciation modes and mechanisms may differentiate some temperate and tropical groups. The Polypodium sibiricum group contains three related diploid species that all inhabit rock outcrops in temperate forests. Although differing lettle in gross leaf morphology and joined by the distinctive morphological synapomorphy of sporangiasters, these three species have an average interspecific genetic identity developed from isozymic com-parisons of only 0.460. A likely mode of speciation is that periodic glaciation pushed Po. sibiricum populations south and, with the retreat of the glaciers, southern populations persisted, evolved diagnostic traits, and ultimately erected postzygotic barriers to interbreeding. This hypothesis follows a classic allopatric speciation model and interspecific distinctions may have been reinforced through contact mediated by subsequent ice ages. In contrast, a monophyletic group of four diploid, epiphytic Pleopeltis species centered in Mexico has an isozymically-determined average interspecific genetic identity value of 0.849. In spite of this high value, these species show greater morphological discrimination than do the Polypodium species. Although the species ranges overlap, they appear to occupy ecologically discrete habitats. These Pleopeltis species may have originated through adaptation to different ecological zones and developed individual morphologies in the process. The high interspecific genetic identity values among the Pleopeltis species suggest a relatively recent and/or rapid process. These hypotheses should be tested by further biosystematic investigations and the discovery of additional monophyletic assemblages with similar patterns of speciation.
    Type of Medium: Electronic Resource
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