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Regeneration, Repair, and Plasticity

Regeneration, Repair, and Plasticity. Chapters 6, 7, 8, 10 P.S. Timiras. The Theories of Aging. Decay of mitochondria Cell senescence Oxidative Stress Shortening of telomeres Evolutionary theories Disposable soma Antagonistic pleiotropy Mutation accumulation

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Regeneration, Repair, and Plasticity

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  1. Regeneration, Repair, and Plasticity Chapters 6, 7, 8, 10 P.S. Timiras

  2. The Theories of Aging • Decay of mitochondria • Cell senescence • Oxidative Stress • Shortening of telomeres • Evolutionary theories • Disposable soma • Antagonistic pleiotropy • Mutation accumulation • System theories • Neuroendocrine • Immune • Rate of living

  3. Neuroendocrine Theory The Nervous System Peripheral (whole-body innervation) Central (brain, spinal cord) Autonomic (regulation of visceral organs, tissues) The Endocrine System Pancreas: Insulin GI hormones Hypothalamus Limbic system Pituitary hormones: Gonadotropins Adrenal steroids Thyroid hormones Growth hormone Prolactin Hypophysiotropic hormones: ADH Oxytocin

  4. Brain Plasticity and CNS Regenerative Potential • From the beginning of the 20th Century until the 1990s, it was stated that neurons DID NOT proliferate. • The fact that they COULD NOT proliferate did not exclude the possibility of proliferation under “specific conditions.” • In fact, the CNS has a considerable regenerative potential depending on the special conditions of the neuronal environment.

  5. Neurons that may proliferate into adulthood include: • Progenitor “precursor” neurons lining the cerebral ventricules • Neurons in the hippocampus • Neurons usually “dormant” with potential for neuron and glia proliferation • Neuroglia (astrocytes, oligodentrocytes) and microglia (immune cells) with the ability to perpetually self renew and produce the three types of neural cells

  6. Regenerative potential depends on changes in whole body and neural microenvironment • Whole body changes: • Physical exercise • Appropriate nutrition • Good circulation • Education • Stress • others • Neural microenvironment • changes: • Brain metabolism (oxygen consumption, free radicals, circulatory changes) • Hormonal changes (estrogens, growth factors, others) • others

  7. Death Rates in 1986 among Persons 25- 64 Years Old in Selected Education and Income Groups According to Race and Sex. ________________________________________________________ GroupWhite Black Men Women Men Women deaths per 1000 Education- yr Completed School 0-11 7.6 3.4 13.4 6.2 12 4.3 2.5 8.0 3.9 College 1-3 4.3 2.1 5.0 3.2 4 2.8 1.8 6.0 2.2 Income-$ <9,000 16.0 6.5 19.5 7.6 9,000-14,999 10.2 3.4 10.8 4.5 15,000-18,999 5.7 3.3 9.8 3.7 19,000-24,999 4.6 3.0 4.7 2.8 >25,000 2.4 1.6 3.6 2.3 ______________________________________________________________________________________ Pappas, G., Queen, S., Hadden, W., and Fisher, G. The increasing disparity in mortality between socioeconomic groups in the United States, 1960 and 1986. N. Engl. J Med. 329, 103-109, 1993.

  8. Proportion of Remaining Life Expected to be Lived with a Disability in Activities of Daily Living and Death Rates ________________________________________________________ At Age At Age At Age Death Rates 65 75 85 per 1,000 White men Low education .11 .21 .45 7.6 Higher education .10 .19 .37 2.8 White women Low education .15 .24 .45 3.4 Higher education .14 .23 .40 1.8 Black men Low education .13 .22 .36 13.4 Higher education .11 .18 .31 6.0 Black women Low education .15 .22 .36 6.2 Higher education .14 .21 .31 2.2 ________________________________________________________________________ From: Guralink, J.M., et al., Educational status and active life expectancy among older blacks and whites, N Engl. J Med., July 8, 1993, Vol. 29:110-116

  9. Better access to medical care Better access to recreational activity Better nutrition Higher income Responsibility to health behaviors No alcohol intake Increased brain reserve capacity? More dendritic branching, cortical synapses?; Better cerebral blood flow?; Better neural cell efficiency, adaptability, redundancy, survival and growth Mechanisms of Education Effects No smoking

  10. Fig. 7-4: “Denudation” of the neurons. Changes in pyramidal neurons of the aging human cerebral cortex

  11. Anatomical Correlates of Educational Protective Effects* Educational Level Increasing levels from <12 to >12 grades Anatomical Correlate total dendritic length mean dendritic length dendritic segment count Location Pyramidal cells in layer 2,3 of Wernicke’s area Variable Studied Gender Hemisphere Education Personal history Hormonal Correlate Thyroid Hormones dendritic number and length Glucocorticoids reactive synaptogenesis ______________ * From Jacobs et al., J Comp. Nuerol., 327, 97, 1993

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