There have been nearly a century since first Alois Alzheimer fibrous plaques found infesting the brains of people with dementia but scientists still do not know with certainty, however-or even if - the plaques cause Alzheimer's disease. Now a trio of studies in the July issue of Nature Medicine opens new avenues for research on the plate with a new animal model for the formation of plaque, a diagnostic tool for identify, and a possible way to break them.
scientists have long suspected that Alzheimer's patients lose their memories and minds when the beta amyloid proteins form aggregates that needle punch holes in the brain cells and kill them. Alzheimer mostly affect the elderly, but scientists have not been able to understand why because they lacked a good animal model of the disease; in previous mouse models, the amyloid plaques formed but brain cells survived. Now neurologists Changiz Geula and Bruce Yankner of Harvard Medical School found such a model: Rhesus monkeys. They injected tiny amounts of amyloid protein in the brains of monkeys and found that the old rhesus monkeys developed symptoms, but young Alzheimer's monkeys remained healthy.
Research on plates was also hampered by the lack of a good method for diagnosing Alzheimer's disease in living patients. A new diagnostic test, created by Detlev Riesner and colleagues at Heinrich-Heine-Universitat in Dusseldorf, Germany, can help identify the plates long before brain cells die. The test, which measures levels of beta-amyloid plaque in the spinal fluid, successfully diagnosed 15 Alzheimer's patients and was not triggered by 19 people with other neurological diseases.
If the plates show a crucial link in Alzheimer's disease, a treatment that breaks down can repair the damage. Claudio Soto and colleagues at New York University Medical Center may have found a protein fragment that does exactly that. In rats and human nerve cells in tissue cultures, these "beta sheet breakers" not only prevent amyloid plaques from forming, but also dissolve existing plaques.
Taken together, the new studies create interesting new tools in the fight against Alzheimer's disease, says Robert Szarek, a pathologist at Queens University in Kingston, Ontario. early diagnosis could help doctors intervene and using a new therapy to preserve brain cells, he said. and if the beta sheet breakers are effective in monkeys and rats, they could also help treat Alzheimer's patients. But this should not be simple. for treating humans, the researchers must still find a way to deliver fragments of proteins past the blood-brain barrier, which prevents movement of proteins into the brain, and the site of the plates. Kisilevsky adds, "These are formidable problems."
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