Multiphoton microscope tracks plaques in mouse model

February 21, 2008 Multiphoton microscope tracks plaques in mouse model Don Rauf -------------------------------------------------------------------------------- Long considered a sentinel factor for Alzheimer's disease, beta-amyloid proteins can accumulate in the brain in aggregations called senile plaques with amazing speed, affecting neurodegeneration just as readily, according to researchers at Harvard Medical School. Using in vivo multiphoton microscopy, Dr. Bradley Hyman and coleagues tracked the deposition of beta-amyloid plaques in the brains of transgenic mice. They were surprised to find that plaques formed extraordinarily quickly over the course of 24 hours. Within one to two days, the plaques appear to cause neurodegeneration to axons, dendrites, and neuroprotective cells. Immune defense cells (microglia) activate and move to the sites of the new plaques. Because the plaque formations did not change in size over days and weeks of imaging, Hyman proposed that the brain may be taking action to limit their growth. The paper points out, however, that plaque formation is rare. After daily and weekly imaging, 26 new plaques were found in 14 animals over 238 sites, imaged a total of 1285 times. Results were published in Nature (2008;451(7179):720-724). Hyman credits the technological advancement of the multiphoton microscope for providing a precise in vivo record of the formation of amyloid plaque and its effects on the brain.

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