Free radicals: important cause of pathologies refer to ageing

Free radical are highly reactive chemical species with an unpaired electron in an atomic or molecular orbital, In biological systems, the most importa nt free radicals are superoxide anion and hydrogen peroxide; in the presenc e of transition metals such as iron, copper and manganese both these free r adicals produce hydroxyl radicals. Free radicals attack proteins, nuclei ac ids and membranes containing large quantities of polyunsaturated fatty acid s. Because of their toxicity, the organism has developed ways to deactivate them, The superoxide dismutase enzyme (SOD) catalyzes dismutation of the s uperoxide radical into hydrogen peroxide and oxygen hydrogen peroxide is in turn reduced to water and oxygen by peroxidase glutathione and catalase en zymes, The production of radicals in the brain is due to catecholamine meta bolism such as dopamine and norepinephrine and is increased by the presence of transition metals and by a deficiency of antioxidant agents such as vit amin E, Two main groups of dementia exist in older age: the multi-infarctua l dementias, caused by cerebrovascular disorders and the primary degenerati ve disorders such as Alzheimer, where no vascular disease is evident. Free radicals play an important role in Parkinson's disease, in Alzheimer's dise ase and in stroke. The value of SOD and CAT activity following the above me ntioned degenerative diseases differ among the various studies carried out. In Alzheimer's disease, the value of SOD activity probably increases in th e neuropathologically involved areas, In stroke, the SOD value does not var y either in the ischemic area or in the peri-infarctual one during the firs t 24 hrs after lesion, while the CAT value decreases.