Medical Health Encyclopedia

Another protein, beta amyloid, also increases the build-up of synuclein. Beta amyloid is a known factor in Alzheimer's disease, and may help explain the co-existence between Alzheimer's and Parkinson's disease in many patients.

Lewy Bodies. The fibrous deposits known as Lewy bodies are the hallmark signs of Parkinson's disease. They are found in the substantia nigra, the place in the brain where dopamine is first released. It is not clear whether Lewy bodies are the major killers of the nerve cells or whether they are simply a byproduct of the degenerative process. They are found not only in the brains of patients with Parkinson's disease, but, in rare cases, may show up in cells in other parts of the body (e.g., the heart, intestine), causing severe disabling symptoms. These substances are also present in other diseases that cause dementia, such as Alzheimer's, and can occur in people without neurologic symptoms.

The Mitochondria and Oxygen-Free Radicals. Some research has observed that certain Parkinson's patients have a significantly low levels of complex I, an enzyme found in the mitochondria, sausage-like structures that are the primary source of energy within cells. Some theories suggest that low amounts of complex I may make nerve cells vulnerable to the assault of oxygen free radicals (also called oxidants). Oxidants are unstable molecules that bind to other molecules in the body. They are normally produced by the natural chemical processes in the body. If the body is subjected to environmental stresses, however, they can be over-produced. And, in excess, they can damage any cell, including nerve cells in the brain, and even interferes with their DNA.

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NMDA Receptors. Also of interest in PD are processes that occur in an area of the brain called the subthalamic nucleus. Here, receptors known as glutamatergic N-methyl-D-aspartate (NMDA) become persistently overexcited and produce high levels of calcium ions within brain cells. This in turn leads to a cascade of events that trigger oxygen-free radicals and cell damage.