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Progeria is another example of a disease that may be related to cell senescence. The disease is thought to be caused by mutations in the DNA damage response, telomere shortening, or a combination of the two. [82] Progeroid syndromes are all examples of aging diseases where cell senescence appears to be implicated.
Senescence (/ s ɪ ˈ n ɛ s ə n s /) or biological aging is the gradual deterioration of functional characteristics in living organisms. Whole organism senescence involves an increase in death rates or a decrease in fecundity with increasing age, at least in the later part of an organism's life cycle.
In biogerontology, the disposable soma theory of aging states that organisms age due to an evolutionary trade-off between growth, reproduction, and DNA repair maintenance. [1] Formulated by British biologist Thomas Kirkwood , the disposable soma theory explains that an organism only has a limited amount of resources that it can allocate to its ...
While cytokinin action in vascular plants is described as pleiotropic, this class of plant hormones specifically induces the transition from apical growth to growth via a three-faced apical cell in moss protonema. This bud induction can be pinpointed to differentiation of a specific single cell, and thus is a very specific effect of cytokinin. [18]
Senescence can be induced by several factors, including telomere shortening, [37] DNA damage [38] and stress. Since the immune system is programmed to seek out and eliminate senescent cells, [39] it might be that senescence is one way for the body to rid itself of cells damaged beyond repair. The links between cell senescence and aging are several:
In higher organisms, aging is likely to be regulated in part through the insulin/IGF-1 pathway. Mutations that affect insulin-like signaling in worms, flies, and the growth hormone/IGF1 axis in mice are associated with extended lifespan. In yeast, Sir2 activity is regulated by the nicotinamidase PNC1.
During the process of aging, an organism accumulates damage to its macromolecules, cells, tissues, and organs.Specifically, aging is characterized as and thought to be caused by "genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular ...
One of the main criticisms of the free radical theory of aging is directed at the suggestion that free radicals are responsible for the damage of biomolecules, thus being a major reason for cellular senescence and organismal aging. [26]: 81 Several modifications have been proposed to integrate current research into the overall theory.