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Unformatted text preview: te apoptosis by controlling the expression or activity of
proapoptotic members of the Bcl-2 family. These pathways include DNA
damage-induced activation of the tumor suppressor p53, growth factorstimulated activation of PI 3-kinase/Akt signaling, and activation of
death receptors by polypeptides that induce programmed cell death. p53, PI 3-kinase, Akt, tumor
necrosis factor (TNF) Alternative Pathways of Programmed Cell Death: Autophagy and regulated necrosis provide alternatives to apoptosis for induction of programmed cell death. autophagy STEM CELLS AND THE MAINTENANCE OF ADULT TISSUES
Proliferation of Differentiated Cells: Most cells in adult animals are
arrested in the G0 stage of the cell cycle. A few types of differentiated
cells, including skin fibroblasts, endothelial cells, smooth muscle cells,
and liver cells are able to resume proliferation as required to replace cells
that have been lost because of injury or cell death.
Stem Cells: Most differentiated cells do not themselves proliferate but
can be replaced via the proliferation of stem cells. Stem cells divide to
produce one daughter cell that remains a stem cell...
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