15-Neuronal_death

15-Neuronal_death - Neuronal Survival & Cell Death Factors...

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Neuronal Survival & Cell Death
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Factors Determine Neuron Survival 20-80% neurons died due to programmed cell death 5 factors affecting survival: 1. Target-derived signal 2. Synaptic input 3. Neighboring neurons 4. Surrounding glial cells 5. Blood vessel-derived signal
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Two neurons with condensed chromatin in their nuclei (arrows). Dying Neurons An electron micrograph shows a degenerating retinal ganglion cell with a clearly pyknotic nucleus (pn). TUNEL assay is used to detect apoptotic cells: T erminal transferase U TP N ick E nd L abeling Attach labeled nucleotides to the exposed 3’- hydroxyl ends of the DNA fragments
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Apoptosis and Necrosis shrinking Osmotic imbalance swelling Injury Natural Apoptosis: Graceful cell death Not to injure neighboring healthy neurons Necrosis: Abrupt death, bursting open membrane May release harmful enzymes or factors Phagocytized Pyknosis is the irreversible condensation of chromatin in the nucleus undergoing apoptosis
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DRG neuronal death occurs mostly in the DRG with less target muscle . Cell death occurs after projection axon contacted targets. Therefore, cell death important for selective elimination of neurons with less target. Cell Death in Chick D orsal R oot G anglia More cell death Limb muscle grows fast, and less cell death in the DRG innervating limb than those DRG innervating the axial musculature, showing target effect on the innervating sensory neurons’ survival.
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Motor Neuron Death Most rapid decrease of the number of healthy cells precisely coincides with the peak of apoptotic motor neurons! Study motor neurons innervating frog hind limb muscle
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Remove limb bud, less motor neurons and DRG cells; Add limb bud, more motor neurons and DRG cells. These results suggest
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This note was uploaded on 08/26/2011 for the course BIOL 426 taught by Professor Profgongchen during the Spring '08 term at Penn State.

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15-Neuronal_death - Neuronal Survival & Cell Death Factors...

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