The study of aging has received much attention in past decades. As the cliché goes, death is as inevitable as taxes, but scientists believe they might know why. No single theory has been deemed the cause of aging; rather there are many theories from a number of disciplines that overlap. If this is the case there must be a way to delay aging, thereby increasing lifespan. Three of the more published theories are the telomere, oxidative stress and calorie restriction theories which all have supporting evidence but do not solely explain why cells senesce.
One theory embraced by many scientists is the telomere theory. Every chromosome ends in a telomere which shortens each time the cell divides; after repeated divisions and considerable telomere loss, the cell undergoes senescence (Steel, 1995). Progeria is a genetic disorder that results in accelerated ageing, Allsopp et al (1992) found that progeria patients had shortened telomeres, strengthening the argument that telomere shortening results in aging.
Cell Biology
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Studies show that telomerase, an enzyme high in egg and sperm cells, can mediate telomere synthesis thus counteracting losses from cell division (Hodes, 1998). However, there may be weaknesses associated with these results. Lahnert (2005) attempted to improve the method used to measure telomere length because various data from other studies are conflicting with some scientists even claiming that telomere shortening was barely a myth. Lahnert established that telomere shortening can be measured but admits that the method could be improved.
The oxidative stress theory proposes that "programmed" mechanisms, such as telomere shortening, are not the only avoidable causes of aging. Free radicals produced through cell metabolism disrupt cellular function causing injury (Sharma & Kaur, 2006); this is what is referred to as oxidative stress. Mostly free radicals are derived from oxygen and...