Pathology of Ageing Flashcards
How do dividing cells age?
-telomeres become shorter after each cell division -> limits the amount of cell division that can occurring
-telomere becomes so short -> chromosomes cannot divide/replicate -> no cell division
Why do cells from older people divide fewer times in culture than cells from younger people?
-shorter telomeres (cells are older therefore they have undergone more rounds of cell division)
-shorter telomeres = more limited amount of times the cell can divide
Examples of dividing cells
-skin cells
-gut lining cells
Hayflick limit
There is a limit to the number of times that a human cell can divide
Graph of time in culture against cumulative cell population
What is progeria?
-condition in which ageing is accelerated
-due to mutations in cell membrane proteins -> cell division impossible
What factors could cause damage in non-dividing cells?
-cross-linking/mutations of DNA
-loss of DNA repair mechanisms
-telomere shortening
-time-dependent activation of ageing & death genes
-cross-linking of proteins
-loss of Ca2+ influx controls
-damage to mitochondrial DNA
-peroxidation of membranes
-free radical generation
-accumulation of toxic by-products of metabolism
What reduces ageing universally across the body?
Calorie restriction -> reduces levels of metabolic products
What can slow down ageing in specific parts of the body - example?
-specific local measures can slow down ageing in specific parts of the body
-high SPF cream -> reduces UV cross-linking of proteins in the dermis -> prevents deral elastosis
Give 5 examples of ageing
-dermal elastosis (skin wrinkling)
-osteoporosis
-cataracts
-senile dementia
-sarcopenia (loss of muscle)
-deafness
Describe dermal elastosis
-wrinkling of skin
-due to accumulation of abnormal elastic in the dermis of the skin - cross-linking of proteins (especially collagen)
-result of prolonged sun exposure - photoaging
-UV-B light causes protein cross-linking
What is osteoporosis?
-disease in which bone breakdown by osteoclasts is greater than bone formation by osteoblasts
-decrease in bone mineral density
-increased risk of fractures
Describe osteoporosis
-caused by loss of coupling in bone remodelling process - increased bone resorption/decreased bone formation
-decreased bone formation due to lack of oestrogen -> women often affected after menopause
-bone matrix mineralised as normal but trabeculae are thinned -> results in fractures from minor trauma
-liberates Ca2+ -> hypercalcaemia -> renal stone formation
How can osteoporosis be prevented?
-hormone replacement therapy (oestrogen)
-Ca2+/vit D supplements
Describe cataracts
-result of formation of opaque proteins within the lens -> usually also results in loss of lens elasticity
-UV-B cross-linking of proteins in lens -> opaque proteins
-UV-B light causes cross-linking
How can cataract formation be prevented?
Sunglasses which block UV-B light
