this hypothesis including the claims that: (1) variation in species life span is correlated with metabolic rate and
protective antioxidant activity; (2) enhanced expression of antioxidative enzymes in experimental animals can produce
a significant increase in longevity; (3) cellular levels of free radical damage increases with age; and (4) reduced calorie
intake leads to a decline in the production of reactive oxygen species and an increase in life span. The free radical
theory may also be used to explain many of the structural features that develop with ageing including the lipid
peroxidation of membranes, formation of age pigments, cross-linkage of proteins, DNA damage and decline of
mitochondrial function. Despite this, many uncertainties concerning the role of oxidative damage in ageing remain
and alternative explanations cannot be ruled out. Free radicals only occur in trace quantities in biological tissues,
their cellular levels and actions cannot be measured in vivo, and definitive proof that oxidised molecules are the
primary cause of ageing is lacking. Moreover, ageing is also likely to be a multifactorial process and not reducible to
any one single cause. Thus, despite its positive features, the evidence for the free radical theory is either correlative
this hypothesis including the claims that: (1) variation in species life span is correlated with metabolic rate andprotective antioxidant activity; (2) enhanced expression of antioxidative enzymes in experimental animals can producea significant increase in longevity; (3) cellular levels of free radical damage increases with age; and (4) reduced calorieintake leads to a decline in the production of reactive oxygen species and an increase in life span. The free radicaltheory may also be used to explain many of the structural features that develop with ageing including the lipidperoxidation of membranes, formation of age pigments, cross-linkage of proteins, DNA damage and decline ofmitochondrial function. Despite this, many uncertainties concerning the role of oxidative damage in ageing remainand alternative explanations cannot be ruled out. Free radicals only occur in trace quantities in biological tissues,their cellular levels and actions cannot be measured in vivo, and definitive proof that oxidised molecules are theprimary cause of ageing is lacking. Moreover, ageing is also likely to be a multifactorial process and not reducible toany one single cause. Thus, despite its positive features, the evidence for the free radical theory is either correlative
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