Immuno-electron microscopy reveals that the excitotoxin quinolinate is associated with the plasma membrane in human peripheral blood monocytes/macrophages |
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Authors: | V Sung C N Venkateshan L Williamson R Ward M G Espey C J Gibbs Jr J R Moffett M A A Namboodiri |
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Institution: | (1) Department of Biology, Georgetown University, Washington DC 20057, USA, US;(2) Laboratory of Central Nervous System Studies, NINDS, NIH, Bethesda, MD 20892, USA, US;(3) Laboratory of Developmental Neurobiology, NICHD, NIH, Bethesda, MD 20892, USA, US |
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Abstract: | Quinolinate (QUIN), a tryptophan-derived excitotoxin, was localized ultrastructurally in human peripheral blood monocytes/macrophages
(M?) by immuno-electron microscopy. A combined carbodiimide/glutaraldehyde/paraformaldehyde-based fixation procedure was developed
for optimal retention of QUIN in the cell as well as minimal loss of ultrastructure; a silver-enhanced colloidal gold detection
system was used for electron-microscopic analysis. Gold particles representing QUIN immunoreactivity were associated with
the inner side of the plasma membrane in normal M?. The number of gold particles increased significantly when QUIN levels
were elevated by treatment with its precursor kynurenine, but location of the gold particles remained essentially the same
under this condition. Treatment with interferon-γ increased the number of Golgi bodies, vacuoles and pseudopodia, reflecting
the activated state of the cell. Significantly increased numbers of gold particles representing QUIN were detectable in approximately
the same location as in the case of kynurenine treatment. Combined treatment with kynurenine and interferon-γ maximally increased
the number of gold particles at the periphery of the cell. The pseudopodia were intensely stained with gold particles, while
they were not detectable in the inner part of the cytoplasm or in any other organelle even under this activated condition.
The significance of the specific location of QUIN revealed in the present study and its relation to the release and subsequent
actions of QUIN are discussed.
Received: 30 May 1996 / Accepted: 22 May 1997 |
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Keywords: | : Quinolinic acid Interferon-γ Kynurenine Electron microscopy Immunocytochemistry Excitotoxicity Human |
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