Lecture+11+Apoptosis+and+Ox - Hypotheses of Aging...

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1 Hypotheses of Aging Evolutionary Antagonistic Pleiotropy Germ line mutation accumulation Damage Theories Somatic mutations Oxidative damage Response to damage - apoptosis Aging in Mitotic vs Post-Mitotic Organs Mitotic “Gatekeeper” genes - act on cells to eliminate potential cancer cells - antagonistic pleiotropy Apoptosis, cellular senescence are key mechanisms Glial cells are still mitotic in the brain Post-Mitotic (Brain) Many mechanisms of mitotic cells are still available Apoptosis DNA damage (to mitochondrial or nuclear DNA)
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2 Mechanisms of Brain Aging Oxidative Damage Damage to DNA, proteins Largely related to free radicals A stochastic process but with systemic repair (ie, genetic coding of anti-oxidant defenses) Programmed Cell Death (Apoptosis) Neuroendocrine factors Stress, hormonal changes, reproductive senescence Waste Accumulation Neuroendocrine Profound hormonal changes occur with age Estrogen Testosterone Lifetime exposure to stress hormones Cortisol These changes have profound effects on brain structure and function - lecture 22 Decline
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3 Waste Accumulation Non-dividing cells accumulate products resulting from metabolism and damage Lipofuscin - a generic term for pigmented granules that accumulate in neurons Very non-specific: end product of many different processes, including auto-oxidation of cellular molecules Lipofuscin is non-reactive - major significance is probably the damage that produces it, not the damage it produces Lipofuscin: Common in Non-Dividing Cells Skeletal Muscle Heart Muscle Electron Micrograph Neuron
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4 Programmed Cell Death (Apoptosis) Cells in a variety of organisms and organs share a common mechanism of cell death due to chronic causes Apoptosis is “cell suicide” - caused by slowly progressive (chronic) conditions Contrast “cell homicide” caused by mechanical damage (trauma), toxins A mechanism to rid the organism of unneeded (no longer functional) or dangerous cells Genetically programmed, highly conserved External Signals Internal Signals Cell shrinkage, fragmentation of cytoplasm, DNA cleavage,
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This note was uploaded on 01/20/2010 for the course NEUROSCIEN Neuroscien taught by Professor Jagust during the Fall '09 term at École Normale Supérieure.

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Lecture+11+Apoptosis+and+Ox - Hypotheses of Aging...

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