Parkinson's disease. Coloured transmission elect- ron micrograph (TEM) of a section through a Lewy body in a nerve cell in the brain, a diagnostic feature of Parkinson's disease. Lewy bodies are largely made up of filaments of the brain protein alpha-synuclein (blue). Parkinson's disease causes degeneration of nerve cells in the brain, leading to muscle tremors, rigidity and incapacitation. It is characterised by the appearance of Lewy bodies, mainly in the substantia nigra, a part of the brain which helps regulate movements. The formation of these filaments is thought to be responsible for the degeneration of the nerve cells. Magnification: x2750 at 6x7cm size.