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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Expression of the protooncogene bcl-2 inhibits both apoptotic and in some cases necrotic cell death in many cell types, including neural cells, and in response to a wide variety of inducers. The mechanism by which the Bcl-2 protein acts to prevent cell death remains elusive. One mechanism by which Bcl-2 has been proposed to act is by decreasing the net cellular generation of reactive oxygen species. To evaluate this proposal, we measured activities of antioxidant enzymes as well as levels of glutathione and pyridine nucleotides in control and bcl-2 transfectants in two different neural cell lines—rat pheochromocytoma PC12 and the hypothalamic GnRH cell line GT1-7. Both neural cell lines overexpressing bcl-2 had elevated total glutathione levels when compared with control transfectants. The ratios of oxidized glutathione to total glutathione in PC12 and GT1-7 cells overexpressing bcl-2 were significantly reduced. In addition, the NAD+/NADH ratio of bcl-2-expressing PC12 and GT1-7 cells was two- to threefold less than that of control cell lines. GT1-7 cells overexpressing bcl-2 had the same level of glutathione peroxidase, catalase, superoxide dismutase, and glutathione reductase activities as control cells. PC12 cells overexpressing bcl-2 had a twofold increase in superoxide dismutase and catalase activity when compared with matched control transfected cells. The levels of glutathione peroxidase and glutathione reductase in PC12 cells overexpressing bcl-2 were similar to those of control cells. These results indicate that the overexpression of bcl-2 shifts the cellular redox potential to a more reduced state, without consistently affecting the major cellular antioxidant enzymes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A mechanism is proposed for the translocation of protons through the hydrogen bonded peptide groups of a protein by means of keto-enol tautomerization. The model is discussed in relation to energy coupling in biomembranes.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0730-2312
    Keywords: serum ; mouse BC3H1 muscle cells ; cell cycle ; muscle-specific genes ; internalized insulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Upon reduction of serum in their media, mouse BC3H1 muscle cells withdraw from the cell cycle and begin to differentiate. In differentiating cells, the induction of muscle-specific genes is accompanied by a distinct morphological chance. However, differentiated BC3H1 cells do not fuse with each other; they remain mononucleated. Metalloendoprotease inhibitors selectively block the differentiation of BC3H1 cells while inhibitors of other protease types are ineffective. In these cells, the degradation of the internalized insulin is initiated by a 110 kDa, non-lysosomal protease known as the insulin-degrading enzyme. The same metalloendoprotease inhibitors that block BC3H1 differentiation also inhibit, with a similar specificity and potency, the in vitro and the in vivo degradation of insulin by the insulin-degrading enzyme. When the serum in the medium is reduced, the activity of the insulin-degrading enzyme in the cell cytoplasm increases rapidly. This increase precedes any detectable change in the differentiation state of these cells by about 12 hours. These results, together with very similar ones obtained with primary rat skeletal muscle cells, support our earlier proposal that the insulin-degrading enzyme is the metalloendoprotease involved in the initiation of the morphological and biochemical differentiation of muscle cells in culture.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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