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Published byStanley Sims Modified over 8 years ago
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Tissue Maintenance Cell turnover by division/death –Division of fully differentiated cells –Division of stem cells Turnover components within cell
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Turnover In Photoreceptor Cells Permanent cells; renewal of membrane discs and proteins Membrane proteins synthesized, placed in new discs at base Old discs at tip are phagocytosed
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Division of Differentiated Cells Hepatocytes in liver; beta cells of pancreas Balance of cell division and cell death Endothelial cells during angiogenesis
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Angiogenesis Division of differentiated endothelial cells Endothelial tip cells lead angiogenesis
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Regulation of Angiogenesis Secreted by many cells in response to need for oxygen Stimulates endothelial cells VEGF is key regulator
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Basal layer contains stem cells Some daughter cells commit to terminal differentiation Multiple steps in differentiation as cells move outward Cells In Epidermis
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Can divide without limit Each daughter either remains as stem cell or commits to terminal differentiation Stem Cells
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Limited divisions following commitment to terminal differentiation Regulation at multiple steps in response to conditions Differentiation Of Daughter Cells
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Hemopoiesis From Multipotent Stem Cells Many cell types derived from common stem cell Terminal differentiation involves series of progressive restrictions Committed progenitor cells undergo limited division
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Regulation By Colony- Stimulating Factors Act on particular hemopoietic cells Promote division, survival, and differentiation Erythropoietin targets erythrocyte colony forming cells Multiple CSFs act on common progenitor for neutrophils and macrophages
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Stem Cell Engineering –Hemopoietic stem cells –Epidermal stem cells –Neural stem cells Stem cells from adult- restricted to forming specific cell types ES cells- pluripotent
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Pluripotent cells can differentiate into any cell type given appropriate combination of signals Generate various progenitors in culture ES Cells
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Sources of ES Cells Early embryo- not patient specific Personalized ES cells –Somatic cell nuclear transplantation –Induced pluripotent stem cells
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Somatic Cell Nuclear Transplantation Nucleus removed from unfertilized egg and replaced with nucleus from diploid cell Develops into early embryo to derive ES cells
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Induced Pluripotent Stem Cells Reprogramming of adult somatic cells to early embryonic-type state Induced by four specific transcription factors
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