Upload
roger-weaver
View
216
Download
2
Embed Size (px)
Citation preview
WHAT MAKES US AGE?WHAT MAKES US AGE?
Life Cycle IILife Cycle II
JOHN TURNERJOHN TURNER
AGE 67AGE 67 AGE 77AGE 77
AGE 90AGE 90AGE 80AGE 80
ELEANOR HYNDMAN
WHY DO WE AGE?
• IS IT GENETICS?
• ENVIRONMENTAL DAMAGE?
THE BIG QUESTION
DEVELOPMENTAL—
GENETIC THEORIES• Genetic makeup
determines factors directly affecting aging
• Programmed & directed in the body
• Aging is Predetermined
ENVIRONMENTAL—
NON- GENETIC THEORIES• Due to random events that
occur over time• Aging caused by
environmental damage• Controlled extrinsically
Theories of Aging
• Finite Lifespan
• Immune System Failure
• Hormonal
• Energy/Caloric Restriction
• Error Theory
• Redundant DNA
• Transcription
• Cross-Linking
Finite Limit Theory
• Hayflick & Moorehead (1961)• Landmark Study--Cells Have Time-clock• Cells Have Limited Life Span
– Apoptosis=Programmed cell death• Cells Proliferated and Divided• Alterations & Degeneration• Cessation of Growth & Division
Neuroendocrine & Hormonal Theory
• Denckla (1974) Endocrinologist Gerontologist
• Aging Mediated in Brain• Functional Decrements in
neurons and associated hormones dictates aging rates
Immunological Theory
• Walford (1969, 1979)• Reduced T-cell function with age
– Decline in Immune System Function• Immune System unable to distinguish between self &
non-self– Age associated increase in autoimmune disorders– Lupus, Scleroderma
Free Radical Theory
• Accumulates Over Time from Oxygen Metabolism– Charged Ion with unpaired
electron– Damages membrane
proteins, mitochondria, etc.– Decreased cellular integrity
• Free radicals associated with atherosclerosis, cancer
Metabolism, Free Radicals, & Life Span
• Metabolic Rate Directly Related to Free Radical Production
• Inverse Relationship Between Metabolic Rate & Life Span
• Hypothesis--Lower metabolic rate, lower free radical production, increase life span
Caloric Restriction Theory
• Walford (1987)--”Dr In Vivo”
• Restriction of Caloric Intake
• High quality nutrient/low calorie diet increases longevity– Supplements with vitamins/minerals/moderate
exercise
• Gradually lose weight until maximal metabolic efficiency, retards aging
Error Theory
• Orgel (1963)• “Any accident or error in either the
machinery or the process of making proteins would cascade into multiple effects”
• DNA--RNA--protein synthesis• Accumulation of errors over time• “Error Crisis” result in impaired cell
function
Redundant DNA
• Medvedev (1972)
• Combination of Finite Limit & Error
• Ability to repair errors to genetic material decreases with age
• Errors in Cellular DNA
• Reserve DNA (error free) utilized
• Cell death when reserve DNA gone
Cross-Linking Theory
• Bjorksten (1942)• Proposed Chemical
reaction of Cross Linking of Macromolecules related to aging– Occurred during sun
tanning--lose elasticity– Loss of Tissue Elasticity
“Number of hypotheses is generally inversely proportional to the clarity of the problem.”
--Frolkis
WHY SO MANY THEORIES?
• Biologic Gerontology New Field
• Can One Single Theory Explain All Aging Processes?
IS THERE A RIGHT ANSWER?