At least some cases of Parkinson's disease are spurred on by mitochondrial failure: "Parkinson's disease is caused by the degeneration of neurons in the midbrain. The mechanisms leading to the loss of these neurons, however, are largely unknown. Recent research revealed that about ten per cent of cases are caused by defects in so-called Parkinson-associated genes. Furthermore, mitochondria, the cellular powerhouses, seem to play a major role. New results [connect] both phenomena, showing that two Parkinson genes maintain the function of mitochondria. ... Functionally impaired mitochondria have been recognized to trigger Parkinson's disease already in the early eighties ... The relevance of mitochondria to the loss of neurons seems plausible - after all, mitochondria supply the cells with energy in form of adenosine triphosphate and play a substantial role in the regulation of cell death. ... Parkinson-associated genes PINK1 and Parkin functionally interact to maintain mitochondrial function. Loss of Parkin or PINK1 function impairs the morphology and activity of mitochondria, which then produce less adenosine triphosphate."