Aging Flashcards
Define ageing?
A process of general, irreversible, and progressive physical deterioration that occurs over time.
Define senescence?
The decline of fitness components of an individual with increasing age or owing to internal deterioration.
Define gerontology?
The scientific study of the biological, physiological and sociologocial phenomena associated with old age and ageing.
Define geriatrics?
The branch of medicine that deals with the diagnoss and treatement of diseases and problems specific to age.
How is life expectancy different to ageing?
Life expectancy has increased in the past 100 years, due to increased public health and medicine, but the rate of ageing hasn’t changed.
Give a list of organisms that don’t age?
Bacteria don’t age.
Hydra don’t appear to age.
Some rockfish live 200+ years; it’s not clear if they age.
Red sea urchin is still fertile at 200+ years.
Tortoises, amphibians, American lobster
Trees: giant Sequoia 2,000+ yrs, bristlecone pine 4,000+ yrs.
What is the current life expectancy in the UK?
81.5 years
What are supercentennaerians?
People who have lived past 120 years of age.
What was the earliest ageing theory?
Programmed Death Theory:
August Weismann 1889
First to formalise the mechanisms of Darwinian evolution. ‘Ageing is part of lifes program because the old need to remove themselves from the theatre to make room for the next generation’
Ageing of cells is genetically programmed, supported by the idea that within species, life span is fairly constant and dependent on the number of somatic regenerations.
What did the easiest theory of ageing explain?
Purpose for ageing is identified, but not a mechanism by which purpose can be achieved.
How individuals would acquire genes that make them get old and die or why ageing genes would make individuals more successful than others lacking those genes.
What are the three evolutionary theories of ageing?
Mutation accumulation, antagonistic pleiotropy and the disposable soma theory.
What are the three mechanistic theories of ageing?
The rate-of-living, Hayflick’s limit: molecular clock and the free radical theory.
Which theory was thought of by Medawar? Explain.
Mutation accumulation, 1952.
Even a population free of ageing, death will nonetheless occur, from extrinsic hazard such as disease, predators and accidents’.
Random mutation accuulte later in life so that they cannot be selected against, as offspring have already been born. Increase later life mortality, increased late onset disease (eg. Huntington’s disease).
When and by who was the antagonistic pleiotropy theory proposed? Explain.
George Williams, 1957
Refers to genes that offer benefits early in life but at the cost of a higher rate of ageing later on. More individuals will survive to express the early benefit, than will survive to suffer from the higher rate of ageing.
Early fertility would be selected, even if that come at the cost of decline and deaths. Suggest that if the benefits outweigh the negatives, the gene will be selected for (eg. Testosterone).
Which theory did Kirkwood propose? Explain.
The disposable Soma Theory, 1977
Comes from the analogy of disposable products. Organisms only have a limited amount of energy that has to be divided between reproductive activities an the maintenance of the non-reproductive aspects of the organisms (soma)
Genes survive, our bodies (soma) do not, they degrade once past peak of reproductive age.
Ageing is the result of natural degrading process that result in accumulation of damage. Damage can only be repaired by the organism at the expense of reproductive effort.
Which theory from 1928 did Pearl propose?
The rate-of-living theory- the duration of life of an organism is dependent upon exhaustion f a fixed quantify of vital substance at a rate proportional to the metabolic rate.
Describe Hayflick’s limit theory?
1961, Molecular clock.
Celsl can multiply a limited number of times.
Average cells divides 50-70 times before death.
As the cell divides, telomeres on the end of chromosome get smaller. Due to telomeres shortening through each division telomeres will no longer be present = senescence.
How did Hayflick produce this theory?
Hayflick and Moorhead mixed equal numbers of normal human male fibroblasts that had divided many times with female fibroblasts that had divided only a few times.
When the male control culture stopped dividing, the mixed culture was examined and only female cells were found. Male cells remembered they were old, even when surrounded by young cells.
Cells had stopped dividing and had become senescent based purely upon how many times the cell had divided.
These results disproved the immortality theory of Carrell, which was the dogma at the time (cells can divide an unlimited number of times).
Hayflick interpreted his findings that the limited replicative capacity of cultured normal cells was a sign oftheir aging and longevity.
He also concluded that immortal cultured cells are mostly cancer cells.
Which theory did Harman propose? Explain.
Free radical theory of ageing, 1956.
Cells continuously produce free radicals by normal metabolism and oxidation of organic compounds and these free radicals damage cellular macromolecules (DNA, proteins, lipids). Accumulation of this damge over time causes ageing.
Controversial theory.
What observations did Harman study?
He studied two observations:
- Lifespan is an inverse function of metabolic rate which in turn is proportional to oxygen consumption
- Oxygen toxicity and radiation toxicity could be explained by the same underlying phenomenon: oxygen radicals.
What is the classic genetic approach of studying ageing in model organisms?
- Isolate mutants which altered rates of ageing
- Map, clone and sequence genes concerned
- Identify lifespan-determining proteins/biochemistry
- Understand ageing…
Give the most commonly used animal models in ageing?
C.elegans (nematoden) Yeast Drosophila Rats Mice
What are beneficial requirements for animal models to study ageing in?
Short lifespans, easily maintained, inexpensive, less complex systems, easy to genetically modify.
Who first observed the effect of caloric restriction on ageing? Explain.
Clive McKay, 1930
3 groups of rats, 1 group fed normally, another group fed normally until weaning and then on a reduced calorie diet and a final group fed normally until 2-weeks post weaning.
The earliest group that was put on calorie restriction lived longer.
