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Cell aging


Cell aging

  is due to genetic factors, diet, social conditions, and presence of age related disease like diabetes, atherosclerosis, osteoarthritis.

     There are progressive accumulations of sub lethal injuries that lead cell death or reduced capacity to respond to injury.

 The cell function decline progressively with age: reduction of ATP synthesis, nucleic acids, cytoskeleton and enzyme proteins, uptake of nutrients, DNA repair.

Morphology:-


 Nucleus is bilobed, mitochondria vacuolated distorted GA, ER reduced in number and accumulation of lipofucsins.


There are advanced glycosylation end products due to non enzymatic glycosylation which facilitate the cross linking of adjacent proteins and abnormal folding of the proteins.

 

The mechanism of aging centers into 2 interrelated processes:

1.  Genetic determined clock.

a)    Incomplete chromosome ends (telomere shortening.) The telomere, a short repeated sequence of the DNA that forms the linear end of the chromosome, is responsible for insuring completion of DNA replication and protects fusing of the end of the chromosome with other chromosomes.

   The length of the telomere is conserved by a telomerase (ribonucleic acid protein) by adding the segment lost in the division. The telomerase activities are expressed in germ cells, low in stem cells and usually absent in somatic cells.

b)     Gene clock: there are genes that control the rate and timing of aging.

 

2- Metabolic events.

 The increase of the oxygen radicals produce modification of the protein lipids and nucleic acids. This results from the increase of the oxidative damage in the aging manifested by the presence of lipofucsins in the aged cells.

















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