Aging
Microglia undergo a burst of mitotic activity during injury; this proliferation is followed by apoptosis to reduce the cell numbers back to baseline. Activation of microglia places a load on the anabolic and catabolic machinery of the cells causing activated microglia to die sooner than non-activated cells. To compensate for microglial loss over time, microglia undergo mitosis and bone marrow derived progenitor cells migrate into the brain via the meninges and vasculature.
Accumulation of minor neuronal damage that occurs during normal aging can transform microglia into enlarged and activated cells. These chronic, age-associated increases in microglial activation and IL-1 expression may contribute to increased risk of Alzheimer's disease with advancing age through favoring neuritic plaque formation in susceptible patients. DNA damage might contribute to age-associated microglial activation. Another factor might be the accumulation of advanced glycation endproducts, which accumulate with aging. These proteins are strongly resistant to proteolytic processes and promote protein cross-linking.
Research has discovered dystrophic (defective development) human microglia. "These cells are characterized by abnormalities in their cytoplasmic structure, such as deramified, atrophic, fragmented or unusually tortuous processes, frequently bearing spheroidal or bulbous swellings." The incidence of dystrophic microglia increases with aging. Microglial degeneration and death have been reported in research on Prion disease, Schizophrenia and Alzheimer's disease, indicating that microglial deterioration might be involved in neurodegenerative diseases. A complication of this theory is the fact that it is difficult to distinguish between "activated" and "dystrophic" microglia in the human brain.
Read more about this topic: Microglia
Famous quotes containing the word aging:
“Bourbon’s the only drink. You can take all that champagne stuff and pour it down the English Channel. Well, why wait 80 years before you can drink the stuff? Great vineyards, huge barrels aging forever, poor little old monks running around testing it, just so some woman in Tulsa, Oklahoma can say it tickles her nose.”
—John Michael Hayes (b.1919)
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revenge, daydream,
theater of the aging convalescent.
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—Marge Piercy (b. 1936)
“You are truly the generation in the middle! You have at once aging parents as well as maturing children to cope with, and you are not granted the deference accorded age, or the indulgence given the young.”
—Helene S. Arnstein (20th century)