Word: amyloid
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...when I read a report in the journal Nature last week about a possible breakthrough in Alzheimer's research, I found myself once again negotiating a tightrope between real promise and false hope. One of the hallmarks of Alzheimer's is the formation of sticky clumps of protein, called amyloid plaques, in the brains of affected patients. Scientists from Elan Pharmaceuticals, a biotech company headquartered in Ireland, reported they had produced a vaccine that could prevent plaques from forming and dissolve existing ones in the brains of mice. They speculated that a similar approach might be used to treat people...
What got lost in the enthusiasm was a sense of how difficult it is to make the leap from mice to men--especially in this case. For starters, mice don't get Alzheimer's disease. The rodents in these experiments were genetically engineered to produce amyloid plaques, but they don't exhibit any of the other telltale signs of Alzheimer's. Indeed, scientists aren't sure whether plaques are a cause or an effect of the disease. A vaccine that removes plaques in mice could still fail to treat the underlying disease in people...
...answer that question, scientists must first understand what causes Alzheimer's, and right now they have only intriguing clues. The most popular hypothesis holds that the disease process starts when a protein called beta amyloid accumulates outside nerve cells, forming the deposits known as plaques. Among other things, plaques appear to impair the ability of neurons to absorb glucose from the bloodstream, generating an energy crisis inside the cell. A competing hypothesis maintains that Alzheimer's begins not with beta amyloid but with a protein called tau. Abnormal variants of this protein, say scientists, clutter the interiors of neurons with...
Which are more important, the plaques or the tangles? As researchers begin to identify the genes that contribute to formation of these lesions, they are finding evidence that supports both camps. Families that carry a defective version of a gene involved in making beta amyloid, it is well established, have high rates of Alzheimer's, which lends weight to the beta amyloid theory. But many more people, observes Duke University neurologist Dr. Allen Roses, carry an Alzheimer's-susceptibility gene known as Apo-E4, which produces a protein that appears to affect tau. Individuals who carry two copies of this...
There are two forms of Amyloid beta protein which are in the brain--one with 40 amino acid molecules per polypeptide chain and the other with...