Ageing
- Created by: Uxia Lorenzo
- Created on: 04-01-13 10:41
Ageing
Longevity genes - under normal circumstances some genes maufacture proteins that limit lifespan - can be mutated
Nematode roundworm
daf 2 gene - controls stage in worms life cycle
worms can hibernate
protein produced by daf 2 drives worms development
daf 2 genes similar in humans
Caloric restriction is shown to prolong life
Cellular senescene
After a number of divisions cells can no longer proliferate
Young human fibroblasts divide about 50 times - the Haylimit limit
at least 4 genes involved
Relicative senescence, we dont die because we run out of cells
Most senscene cells are not dead or dying
They respond to hormones and stimuli
just cant proliferate
Telomeres
Telomeres- get shorter as cell divides repeated thousands of times
don't contain important genetic info
help keep chromosomes intact
During mitosis - replicates DNA can't the outer edges
each time the cell divides, the telomeres shorten
Over time the telomeres shorten so much that it leads the cell to stop proliferating
Telormer length give some indication of how many divisions cells has undergone and how many remain before it can duplicate
Telomere research
in immortal cancer cells telomeres act abnormally
no longer shrink with each division
Telomerase is inactive in most adults
swing into action in advanced cancers
if you block telomerase activity - cure cancer
Biochemistry and Ageing
Everyday metabolic processes exposed cells to biochemical substance
Oxygen radicals, heat shock, hormones
Oxygen radicals - demolish proteins and damage nucleotides
damage contributes to ageing
Free radical - highly reactive electron
by - products of normal metabolism
free radicals do not go unchecked
Antioxidents
nutrients vitamins C and E and beta carotene
enzymes can prevent some oxidative damage
damage mounts and contributes to deterioating tissue
converts oxygen radicals into hydrogen peroxide which is then converted into O2 and H2O
Glucose Cross linking
non-enzymatic glycosation or glycation, glucose molecules attach themselves
sets in motion a chain of chemical reactions that end in the proteins binding together or crosslinking
Crosslinks = Advanced Glycosation end products (AGES) = toughen tissues and cause deterioation
Stiffen tissues, harden arteries, clouded eyes, loss of nerve functions
Macrophages combat glycation
eliminated by urine
Heat Shock Proteins
produced when cells are exposed to various stress
triggered by exposure to toxic substances such as heavy metals
levels product depend on age
help the cell dissassembled dispose of damaged proteins
DNA repair
DNA can be damaged 'deletions, mutation'
ability to repair certain types of DNA damage is directly to life span
unprotected by the protein coat
Growth factors
substances such as Insulin - like growth factor
Hormones
hormone injecting reverse ageing process - lean muscle mass
Recombinant Human Growth Hormone
synthetic version of pituatry gland
Production of testerone and oestrogen falls off
Hormone replacement
Oestrogen replacement lessens bone mass from menopause
DHEA - dehydroplandrosterone - abundant in youth
low levels associated with stress and cancer
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