Theories of biological aging
Download
1 / 34

Theories of Biological Aging - PowerPoint PPT Presentation


Theories of Biological Aging. Dave Morgan Alzheimer Research Laboratory Dept of Pharmacology. AGING Successful Typical Unsuccessful. Is Aging Universal?. Senescence is the age when an organism’s viability is reduced dramatically due to impaired physiology Gradual Senescence

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Theories of Biological Aging ' - Sharon_Dale


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Theories of biological aging l.jpg

Theories of Biological Aging

Dave Morgan

Alzheimer Research Laboratory

Dept of Pharmacology


Aging successful typical unsuccessful l.jpg
AGINGSuccessfulTypicalUnsuccessful


Is aging universal l.jpg
Is Aging Universal?

  • Senescence is the age when an organism’s viability is reduced dramatically due to impaired physiology

  • Gradual Senescence

    • Humans, most mammals

  • Negligible Senescence

    • Redwoods, Bristlecone pines, Tortoises, Rockfish, Lobsters

  • Rapid, Obligate Senescence

    • Many insects, Annual plants, Salmon, Some mice

  • Single Celled Organisms

    • Fission produces two daughters of equal seniority


Survival curves indicate the effects of aging on mortality l.jpg
Survival Curves Indicate the Effects of Aging on Mortality

  • 100 % surviving at birth (age 0)

  • Early infant mortality

  • Age-independent mortality rate (10-50)

  • Age-dependent mortality rate (60+)

  • 50% = median (~avg)

  • 0% = maximum


Lifespan effects of slowing aging l.jpg
Lifespan Effects of Slowing Aging

  • Eliminating Disease increases median longevity; rectangularizes the survival curve (1-3).

  • Slowing Aging increases both median and maximum longevity (curve 4).


Senescence occurs rarely in the wild l.jpg
Senescence Occurs Rarely in the Wild

  • In the wild, organisms rarely reach the age of senescence.

  • Age-associated degenerative diseases are recent causes of death



Most infants do not reach puberty l.jpg
Most Infants do not Reach Puberty Fixed

  • Infant Mortality was the norm

  • Evolution operates until the age of reproductive success

  • Prehistoric gravesites contain primarily children


Longevity increased dramatically in the 20 th century l.jpg
Longevity Increased Dramatically in the 20 Fixed th Century

  • Major gain is reduced childhood mortality

  • Likely Causes

    • Sanitation

    • Nutrition

    • Medical Care



Do women outlive men because they are shorter l.jpg
Do Women Outlive Men Because They Are Shorter? Fixed

  • Height is inversely related to longevity in many populations with widely divergent overall longevities

  • Women are 8% smaller than men (on average) and live 7.9% longer).

  • The line relating height and longevity is identical for men and women



Wear and tear theories of aging l.jpg
Wear and Tear Theories of Aging Fixed

  • Extrinsic Causes

  • Stochastic (not determined)

  • Proceeds much like aging in your automobile


Biological clock theories of aging l.jpg
Biological Clock Theories of Aging Fixed

  • Aging is programmed

  • Intrinsic; generated from within

  • Determinant

  • Clocks may exist as a master clock and/or cellular clocks


Slide16 l.jpg



The hayflick limit l.jpg
The Hayflick Limit captive environments


Population doublings correlate with longevity l.jpg
Population Doublings Correlate with Longevity captive environments

  • Longer lived species have more population doublings

  • Cells from young individuals have more population doublings

  • Cells from individuals with progerias (accelerated aging syndromes) have fewer population doublings


Biological clock may be telomeres l.jpg
Biological Clock may be Telomeres captive environments

  • Caps on the ends of chromosomes get shorter each cell division

  • When telomeres get too short, cells stop dividing


Telomerase extends telomeres l.jpg
Telomerase extends telomeres captive environments

  • If telomeres disappeared each generation, the next generation may run out

  • Telomerase permits separation of a mortal somatic cell lineage and an immortal germ line lineage.

  • Multicelled creatures permitted the soma to become disposable



Limitations of the cell division hypothesis l.jpg
Limitations of the Cell Division Hypothesis captive environments

  • Tissues (bone marrow) can be serially transplanted to give lifespans far exceeding that of original donor

  • Most of your body mass is post-mitotic cells

  • Telomerase knockouts have normal offspring for several generations


Wear and tear dna mutations l.jpg
Wear and Tear: DNA Mutations captive environments

  • Damage to most molecules overcome by replacement (turnover of lipids and proteins).

  • Damage to DNA, the blueprint, if permanent, leads to accumulation of errors.

  • Causes are heat, oxygen, mutagens


Dna repair may slow aging l.jpg
DNA Repair May Slow Aging captive environments

  • Cells have multiple DNA repair systems

  • Accumulated mutations should lead to impaired cell function, even in new cells if damaged DNA is copied



Biological energy partitioning l.jpg
Biological Energy Partitioning captive environments

  • As a species, organisms may exchange energy between repair and reproduction.


Slide28 l.jpg

If too little repair, individuals die before they reproduce. Natural selection chooses enough repair to maximize reproductive effort. Theoretically, enough repair leads to negligible senescence (human median longevity of 1000 years).


Caenorhabditus elegans l.jpg
Caenorhabditus Elegans Natural selection chooses enough repair to maximize reproductive effort. Theoretically, enough repair leads to negligible senescence (human median longevity of 1000 years).

  • Microscopic nematodes

  • Hermaphroditic, easy to clone

  • About 1000 cells, developmental fate mapped

  • Easy to mutate

  • Several mutations that extend lifespan, also reduce fecundity


Radiation extends mouse lifespan l.jpg
Radiation extends mouse lifespan Natural selection chooses enough repair to maximize reproductive effort. Theoretically, enough repair leads to negligible senescence (human median longevity of 1000 years).


Humans may benefit also l.jpg
Humans may benefit also Natural selection chooses enough repair to maximize reproductive effort. Theoretically, enough repair leads to negligible senescence (human median longevity of 1000 years).

  • Survivors of atomic bomb attacks have reduced rates of cancer

  • Hormesis- small amounts of damaging agents toughens the body

  • Tanning, strength training, calluses are examples


The aristotelian mean l.jpg
The Aristotelian Mean Natural selection chooses enough repair to maximize reproductive effort. Theoretically, enough repair leads to negligible senescence (human median longevity of 1000 years).

  • “All things in moderation”

  • Longevity maximized by avoidance of excess

  • Longevity may also be maximized by avoidance of abstinence

  • Jeanne Calment. Lived to 123. Died several years ago. Smoked cigars to 110. Drank champagne until she died.


Conclusions l.jpg
Conclusions Natural selection chooses enough repair to maximize reproductive effort. Theoretically, enough repair leads to negligible senescence (human median longevity of 1000 years).

  • Aging likely results as an accident. So few organisms reached advanced age there was no evolutionary advantage to avoid aging

  • Pleiotropy. The idea that something could benefit an organism during development, but be detrimental as the organism aged

  • Both biological clock and wear and tear theories have support. Aging, like many diseases is likely to be multifactorial. Theories are not mutually exclusive.


ad
  • Login