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David Schubert - One of the best experts on this subject based on the ideXlab platform.

  • cytotoxic amyloid peptides inhibit cellular 3 4 5 dimethylthiazol 2 yl 2 5 diphenyltetrazolium bromide mtt reduction by enhancing mtt Formazan exocytosis
    Journal of Neurochemistry, 2002
    Co-Authors: Yuanbin Liu, David Schubert
    Abstract:

    Amyloid beta peptide (A beta) neurotoxicity is believed to play a central role in the pathogenesis of Alzheimer's disease. An early indicator of A beta toxicity is the inhibition of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction to MTT Formazan, a widely used assay for measuring cell viability. In this report we show that A beta and other cytotoxic amyloid peptides such as human amylin dramatically enhance MTT Formazan exocytosis, resulting in the inhibition of cellular MTT reduction. Only the amyloid peptides that are known to be cytotoxic enhanced MTT Formazan exocytosis. Basal MTT Formazan exocytosis and amyloid peptide-enhanced MTT Formazan exocytosis are blocked by several drugs with diverse known effects. These and other data suggest that MTT Formazan exocytosis is a multistep process and that cytotoxic amyloid peptides enhance MTT Formazan exocytosis through an intracellular signal transduction pathway.

  • steroid hormones block amyloid fibril induced 3 4 5 dimethylthiazol 2 yl 2 5 diphenyltetrazolium bromide mtt Formazan exocytosis relationship to neurotoxicity
    Journal of Neurochemistry, 2002
    Co-Authors: Yuanbin Liu, David Schubert
    Abstract:

    Perhaps the most reproducible early event induced by the interaction of amyloid beta peptide (A beta) with the cell is the inhibition of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction. We recently demonstrated that cytotoxic amyloid peptides such as A beta and human amylin inhibit cellular MTT reduction by dramatically enhancing MTT Formazan exocytosis. We now show the following: (a) Insulin and glucagon, when converted to fibrils with beta-pleated sheet structure, induce MTT Formazan exocytosis that is indistinguishable from that induced by A beta. NAC35, an amyloidogenic fragment of alpha-synuclein (or NACP), also induces MTT Formazan exocytosis. (b) All protein fibrils with the beta-pleated sheet structure examined are toxic to rat hippocampal neurons. (c) Many sterol sex hormones (e.g., estradiol and progesterone) block amyloid fibril-enhanced MTT Formazan exocytosis as well as MTT Formazan exocytosis in control cells by acting at a common late step in the exocytic pathway. Steroids fail, however, to protect hippocampal neurons from acute amyloid fibril toxicity. These findings suggest that the ability to enhance MTT Formazan exocytosis and to induce neurotoxicity are common biological activities of protein fibrils with beta-pleated sheet structure but that enhanced MTT Formazan exocytosis is not sufficient for acute A beta neurotoxicity.

Yuanbin Liu - One of the best experts on this subject based on the ideXlab platform.

  • cytotoxic amyloid peptides inhibit cellular 3 4 5 dimethylthiazol 2 yl 2 5 diphenyltetrazolium bromide mtt reduction by enhancing mtt Formazan exocytosis
    Journal of Neurochemistry, 2002
    Co-Authors: Yuanbin Liu, David Schubert
    Abstract:

    Amyloid beta peptide (A beta) neurotoxicity is believed to play a central role in the pathogenesis of Alzheimer's disease. An early indicator of A beta toxicity is the inhibition of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction to MTT Formazan, a widely used assay for measuring cell viability. In this report we show that A beta and other cytotoxic amyloid peptides such as human amylin dramatically enhance MTT Formazan exocytosis, resulting in the inhibition of cellular MTT reduction. Only the amyloid peptides that are known to be cytotoxic enhanced MTT Formazan exocytosis. Basal MTT Formazan exocytosis and amyloid peptide-enhanced MTT Formazan exocytosis are blocked by several drugs with diverse known effects. These and other data suggest that MTT Formazan exocytosis is a multistep process and that cytotoxic amyloid peptides enhance MTT Formazan exocytosis through an intracellular signal transduction pathway.

  • steroid hormones block amyloid fibril induced 3 4 5 dimethylthiazol 2 yl 2 5 diphenyltetrazolium bromide mtt Formazan exocytosis relationship to neurotoxicity
    Journal of Neurochemistry, 2002
    Co-Authors: Yuanbin Liu, David Schubert
    Abstract:

    Perhaps the most reproducible early event induced by the interaction of amyloid beta peptide (A beta) with the cell is the inhibition of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction. We recently demonstrated that cytotoxic amyloid peptides such as A beta and human amylin inhibit cellular MTT reduction by dramatically enhancing MTT Formazan exocytosis. We now show the following: (a) Insulin and glucagon, when converted to fibrils with beta-pleated sheet structure, induce MTT Formazan exocytosis that is indistinguishable from that induced by A beta. NAC35, an amyloidogenic fragment of alpha-synuclein (or NACP), also induces MTT Formazan exocytosis. (b) All protein fibrils with the beta-pleated sheet structure examined are toxic to rat hippocampal neurons. (c) Many sterol sex hormones (e.g., estradiol and progesterone) block amyloid fibril-enhanced MTT Formazan exocytosis as well as MTT Formazan exocytosis in control cells by acting at a common late step in the exocytic pathway. Steroids fail, however, to protect hippocampal neurons from acute amyloid fibril toxicity. These findings suggest that the ability to enhance MTT Formazan exocytosis and to induce neurotoxicity are common biological activities of protein fibrils with beta-pleated sheet structure but that enhanced MTT Formazan exocytosis is not sufficient for acute A beta neurotoxicity.

Hairong Cheng - One of the best experts on this subject based on the ideXlab platform.

Robert M Hoffman - One of the best experts on this subject based on the ideXlab platform.

  • noncolorimetric measurement of cell activity in three dimensional histoculture using the tetrazolium dye 3 4 5 dimethylthiazol 2 yl 2 5 diphenyltetrazolium bromide the pixel image analysis of Formazan crystals
    Analytical Biochemistry, 1992
    Co-Authors: Donato Colangelo, Hui Yan Guo, Kenneth M Connors, Luigi Silvestro, Robert M Hoffman
    Abstract:

    We describe a novel system for measuring the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction in three-dimensional histoculture which is no longer dependent on colorimetric determination of extracted Formazan, but rather is based on a pixel image analysis of Formazan crystals, and which allows intratumor heterogeneity to be taken into account. The MTT test is based on the enzymatic reduction of the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-dipheniltetrazolium bromide to Formazan crystals by living, metabolically active cells, but not in dead cells. The reaction was carried out in situ in six-well plates on gel-supported histocultured human tumors. After a 24-h incubation with different drugs the tumors were incubated with a solution of MTT. Frozen sections of the tumor pieces were made and the slides were then stained with a propidium iodide solution, whose fluorescence is proportional to the number of cells present. We demonstrate here that the Formazan crystals, formed by MTT reduction, reflect polarized light and that this can be quantified by using an image analysis system based on bright-pixel quantitation directly on a frozen section of the original tissue. Combined with the use of the fluorescent dye propidium iodide, also measured by pixel analysis, we can express a ratio between the total amount of MTT reduction and the total number of cells present in the specimen that expresses the effect of drugs on the histocultured tumors. Since histology is well maintained in histoculture it is possible to take into account the heterogeneity present in the tumor with regard to drug response.(ABSTRACT TRUNCATED AT 250 WORDS)

Hengwei Wang - One of the best experts on this subject based on the ideXlab platform.