somatomedin and platelet-derived growth factor(PDGF) Other factors have been isolated from various tissues such as fibroblast growth factor(FGF) from brain and epidermal growth factor(EGF) from the submaxillary gland. Some prostaglandins, at least, PGE2a have been found to induce DNA Synthesis and cell division. All these agents are said to be mitogenic, i.e., mitosis-stimulating. As mentioned in previous chapters, substrata on which cells grow are also very important factors for cell growth. There are also factors that inhibit cell growth. It is possible that growth level of tissues in the body are dependent on some type of balance between stimulatory and inhibitory agents. It is believed that most, if not all, mitogenic agents bring about heir response as a result of an interaction with the cell surface receptors and subsequent signaling in plasma membrane and cytoplasm, particularly rTK pathway
somatomedin and platelet-derived growth factor (PDGF). Other factors have been isolated from various tissues, such as fibroblast growth factor (FGF) from brain and epidermal growth factor (EGF) from the submaxillary gland. Some prostaglandins, at least, PGE2 have been found to induce DNA synthesis and cell division. All these agents are said to be mitogenic, i.e., mitosis-stimulating. As mentioned in previous chapters, substrata on which cells grow are also very important factors for cell growth. There are also factors that inhibit cell growth. It is possible that growth level of tissues in the body are dependent on some type of balance between stimulatory and inhibitory agents. It is believed that most, if not all, mitogenic agents bring about their response as a result of an interaction with the cell surface receptors and subsequent signaling in plasma membrane and cytoplasm, particularly RTK pathway
14.2 The cell cycle The cell cycle or cell-division cycle is reproductive cycle of a cell: the orderly sequence of events by which a cell duplicates its contents and divides into two. The discovering and identifying a key position of DNA synthesis cycle in cell cycle is the one of the most important discoveries in the cell biology field in 1950s 1. Two major phases There are two readily observed phases of cell cycle M phase and interphase M phase: the process of mitosis, and cytokinesis. It takes about 30-60 min Interphase: the vast majority of the cell cycle is spent in this phase Interphase in cell cycle includes Gi,S, and G, phase
14.2 The cell cycle The cell cycle or cell-division cycle is reproductive cycle of a cell: the orderly sequence of events by which a cell duplicates its contents and divides into two. The discovering and identifying a key position of DNA synthesis cycle in cell cycle is the one of the most important discoveries in the cell biology field in 1950s. 1.Two major phases There are two readily observed phases of cell cycle: M phase and interphase. M phase: the process of mitosis, and cytokinesis. It takes about 30-60 min. Interphase: the vast majority of the cell cycle is spent in this phase. Interphase in cell cycle includes G1 , S, and G2 phase
The great variability in the lengths of cell cycle of different cells from less then 30 min (such as in some cleaving embryos) to several months(e.g. liver ) Rapidly growing adult cells typically divide every 12 to 36 hours. Of the three stages of interphase, G, is the most variable(even a few of cells have not G phase). Once the signal to begin DNA replication is received, the cell almost invariably completes that round of DNA synthesis and continues through mitosis G: cell grows and carries out normal metabolism organelles duplicate S: DNA replication and chromosome duplication G: cell grow and prepares for mitosis M: Prophase, metaphase, anaphase, telophase, and cytokinesis For mammal
The great variability in the lengths of cell cycle of different cells from less then 30 min.(such as in some cleaving embryos) to several months (e.g. liver). Rapidly growing adult cells typically divide every 12 to 36 hours. Of the three stages of interphase, G1 is the most variable (even a few of cells have not G1 phase). Once the signal to begin DNA replication is received, the cell almost invariably completes that round of DNA synthesis and continues through mitosis. G1 : cell grows and carries out normal metabolism; organelles duplicate. S : DNA replication and chromosome duplication G2 : cell grow and prepares for mitosis M: Prophase, metaphase, anaphase, telophase, and cytokinesis . For mammal
G,. several hrs-more than hundred hrs S:8-30hs G2:1-2h.or3-5hs M:0.5-1h Go phase cells: cells are locked in this stage unable to enter cell cycle, unless Go cells are activated 2. Cell cycle synthetic activities Relatively constant biosynthesis throughout the interphase except the histones, whose synthesis occurs almost exclusively, synchronizing with DNA replication during S phase, Once replication has been completed, the histone messengers are selectively destroyed. And marked drop in protein synthesis and virtual cessation of RNA synthesis occurs during mitosis. The analysis of DNA content by isotopic incorporation or flow cytometer or fluorescence- active cell sorter is used to estimate the phase of cell cycle
G1 : several hrs-more than hundred hrs, S: 8-30 hs , G2 : 1-2h. or 3-5hs M:0.5-1h. Go phase cells: cells are locked in this stage unable to enter cell cycle, unless Go cells are activated. 2. Cell cycle synthetic activities Relatively constant biosynthesis throughout the interphase except the histones, whose synthesis occurs almost exclusively, synchronizing with DNA replication during S phase, Once replication has been completed, the histone messengers are selectively destroyed. And marked drop in protein synthesis and virtual cessation of RNA synthesis occurs during mitosis. The analysis of DNA content by isotopic incorporation or flow cytometer or fluorescence- active cell sorter is used to estimate the phase of cell cycle
G:S: Cell grows and DNA replication carries out normal and chromosome metabolism; duplication organelles duplicate