B. S. Haldane wondered why the dominant mutation that causes Huntington's disease remained in the population, and why natural selection had not eliminated it. The discovery, in 1934, that calorie restriction can extend lifespan by 50% in rats, and the existence of species having negligible senescence and potentially immortal organisms such as Hydra, have motivated research into delaying senescence and thus age-related diseases. In many organisms, there is asymmetric cell division, e.g. Rare human mutations can cause accelerated aging diseases. Thanks for using this online dictionary, we have been helping millions of people improve their use of the TAMIL language with its free online services. drive at full speed; hence, to hasten; to hurry. There is evidence that sugar damage is linked to oxidant damage in a process termed glycoxidation. The word senescence can refer either to cellular senescence or to senescence of the whole organism. Calorically restricted animals process as much, or more, calories per gram of body mass, as their ad libitum fed counterparts, yet exhibit substantially longer lifespans. People with diabetes, who have elevated blood sugar, develop senescence-associated disorders much earlier than the general population, but can delay such disorders by rigorous control of their blood sugar levels. Senescence is the inevitable fate of all multicellular organisms with germ-soma separation,[1][2] but it can be delayed. The state or process of ageing, especially in humans; old age.
Senescence occurs both on the level of the whole organism as well as on the level of its individual cells. [citation needed]. Old age; accumulated damage to macromolecules, cells, tissues and organs with the passage of time. Sufferers exhibit symptoms resembling accelerated aging, including wrinkled skin. Gene expression is imperfectly controlled, and it is possible that random fluctuations in the expression levels of many genes contribute to the aging process as suggested by a study of such genes in yeast. This report suggests that DNA damage, not oxidative stress, is the cause of this form of accelerated aging. Thanks for your vote! This article is about the aging of whole organisms including animals. Natural selection can remove damaged cells and prevent their proliferation, counterbalancing the natural tendency for damaged cells to accumulate. This can prevent highly mutated cells from becoming cancerous. of senescĕre, to grow old—senex, old. rapidly; rate of motion; dispatch; as, the speed a horse or a vessel.
These adducts can further rearrange to form reactive species, which can then cross-link the structural proteins or DNA to similar biopolymers or other biomolecules such as non-structural proteins. [23][43], It is believed that the impact of alcohol on aging can be partly explained by alcohol's activation of the HPA axis, which stimulates glucocorticoid secretion, long-term exposure to which produces symptoms of aging. ", "Clearance of p16Ink4a-positive senescent cells delays ageing-associated disorders", "Targeting senescent cells enhances adipogenesis and metabolic function in old age", "Clearing out damaged cells in mice extends lifespan by up to 35 percent", "In New Anti-Aging Strategy, Clearing Out Old Cells Increases Life Span of Mice by 25 Percent", "NANOG restores the impaired myogenic differentiation potential of skeletal myoblasts after multiple population doublings", "NANOG Restores Contractility of Mesenchymal Stem Cell-Based Senescent Microtissues", "Nanog Reverses the Effects of Organismal Aging on Mesenchymal Stem Cell Proliferation and Myogenic Differentiation Potential", "Nanog induces suppression of senescence through downregulation of p27KIP1 expression", "Happily (n)ever after: Aging in the context of oxidative stress, proteostasis loss and cellular senescence", "An Analysis of the Relationship Between Metabolism, Developmental Schedules, and Longevity Using Phylogenetic Independent Contrasts", "Living fast, dying when? [40]), With respect to specific types of chemical damage caused by metabolism, it is suggested that damage to long-lived biopolymers, such as structural proteins or DNA, caused by ubiquitous chemical agents in the body such as oxygen and sugars, are in part responsible for aging. Organisms that are thought be biologically immortal would, in one instance, be the Turritopsis dohrnii, also known as the immortal jellyfish. The Turritopsis dohrnii received such a title by having the ability to revert to its youth when it undergoes stress during adulthood. Aging has been defined as "a progressive deterioration of physiological function, an intrinsic age-related process of loss of viability and increase in vulnerability.
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