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The cellularity of the bone marrow does decrease with age and can be usually calculated by the formula 100-age, and this seems consistent with a stem cell theory of aging. [18] A dog study published by Zaucha J.M, Yu C. and Mathioudakis G., et al. also shows evidence against the stem cell theory. Experimental comparison of the engraftment ...
The immunological theory of aging suggests that the immune system weakens as an organism ages. This makes the organism unable to fight infections and less able to destroy old and neoplastic cells. This leads to aging and will eventually lead to death. This theory of aging was developed by Roy Walford in 1969.
The theory is based on the idea that ageing occurs over time due to the damage of the DNA. As an example, studies of mammalian brain and muscle have shown that DNA repair capability is relatively high during early development when cells are dividing mitotically, but declines substantially as cells enter the post-mitotic state. [28] [29] [30]
Cellular differentiation is the process in which a stem cell changes from one type to a differentiated one. [2] [3] Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types.
A stem cell possesses two properties: . Self-renewal is the ability to go through numerous cycles of cell division while still maintaining its undifferentiated state. Stem cells can replicate several times and can result in the formation of two stem cells, one stem cell more differentiated than the other, or two differentiated cells.
Stem cell theory of aging; Stereotype embodiment theory; T. Telomere theory of aging; V. Vital substance theory of aging; W. Waste product accumulation theory of aging;
Aging is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. The hallmarks of aging are the types of biochemical changes that occur in all organisms that experience biological aging and lead to a progressive loss of physiological integrity, impaired function and, eventually, death.
Stem cell theory of aging; T. Telomere theory of aging; V. Vital substance theory of aging; W. Waste product accumulation theory of aging; Wear and tear theory of aging