细胞科学 i Science 蔡国平
细胞科学 Cell Science （14） 蔡国平
814. Cell reproduction and the cell cycle
§14. Cell reproduction and the cell cycle
8 14 Cell reproduction and the cell cycle 14.1 Cell reproduction Countless divisions of a single-celled zygote produce an organism of astonishing cellular complexity and organiza- tion. Any individual cell is bound to die, because cells are subject to wear and tear as well as to accidents. 25 million cells are undergoing division each second in an adult human and blood cells renewed at the rate of about 100 million per minute. If an organism is to continue to live, it must create new cells at rate as fast as that at which its cells die and for some cells, cell division is a special active process that is responsive for a special physiological activity, for example, the reproduction of gonial cells and apical meristem cells of plants as well as the selective proliferation of lymphocytes in immuno-response
§ 14 Cell reproduction and the cell cycle 14.1 Cell reproduction Countless divisions of a single-celled zygote produce an organism of astonishing cellular complexity and organization. Any individual cell is bound to die, because cells are subject to wear and tear as well as to accidents. 25 million cells are undergoing division each second in an adult human and blood cells renewed at the rate of about 100 million per minute. If an organism is to continue to live, it must create new cells at rate as fast as that at which its cells die and for some cells, cell division is a special active process that is responsive for a special physiological activity, for example, the reproduction of gonial cells and apical meristem cells of plants as well as the selective proliferation of lymphocytes in immuno- response
Each dividing cell is called mother cell, and its descen dants are called daughter cells, which are to become mother cells in their cell division actually, passing along the same genes they inherited from their mother to yet another new cellular generation. Therefore, cell division is often referred to as cell reproduction. Cell reproduction is a process of cell proliferation by which cell numbers or cell population become often larger continually. Cell reproduction have mainly three types: amitosis, mitosis and meiosis. Cell proliferation may be controlled normal cell reproduction but may become malignant cell proliferation losing normal controlling. Cell growth includes two meaning, one is that cell size become larger during development, another is the increase of cell numbers by cell proliferation. In most cases the meaning of cell growth is equal to cell proliferation
Each dividing cell is called mother cell, and its descen- dants are called daughter cells, which are to become mother cells in their cell division actually, passing along the same genes they inherited from their mother to yet another new cellular generation. Therefore, cell division is often referred to as cell reproduction. Cell reproduction is a process of cell proliferation by which cell numbers or cell population become often larger continually. Cell reproduction have mainly three types: amitosis, mitosis and meiosis. Cell proliferation may be controlled normal cell reproduction but may become malignant cell proliferation losing normal controlling. Cell growth includes two meaning, one is that cell size become larger during development, another is the increase of cell numbers by cell proliferation. In most cases, the meaning of cell growth is equal to cell proliferation
1. Three broad categories of cells with different division activity within multi-cellular organism Lost the ability to undergo division remaining in: extreme specialization state until they die. E. g. nerve cells, muscle cells. or red blood cells Cells that normally do not divide, but can be induced to begin DNA synthesis by some appropriate stimulus. E. g liver cells lymphocytes Cells that normally possess continually a relatively high and level of mitotic activity. Gonial cells, bone marrow stem cells, epithelial cells, and apical meristem cell of plants
1.Three broad categories of cells with different division activity within multi-cellular organism: · Lost the ability to undergo division remaining in extreme specialization state until they die. E.g. nerve cells, muscle cells, or red blood cells. · Cells that normally do not divide, but can be induced to begin DNA synthesis by some appropriate stimulus. E.g. liver cells lymphocytes. · Cells that normally possess continually a relatively high and level of mitotic activity. Gonial cells, bone marrow stem cells, epithelial cells, and apical meristem cell of plants
2. Cell culture and cell growth curve Cell culture, particularly, animal cell culture is often used in study on the cell growth and dividing, which might reveal many of the basic properties of cells whose study is more difficult within the organism 1)Density-dependent regulation of cell growth and contact inhibition of growth If the conditions in which cells are cultured are optimal the cells will grow rapidly; mammalian cells typically grow in culture with generation times (lag phase) from 12 to 24 hours. And then cells grow rapidly in an exponential (or log phase, and then gradually slow and finally reaches a point where cell growth and division have virtually stopped, even if sufficient nutrients are still present, being in quiescent or stationary phase
2. Cell culture and cell growth curve Cell culture, particularly, animal cell culture is often used in study on the cell growth and dividing, which might reveal many of the basic properties of cells whose study is more difficult within the organism. 1) Density-dependent regulation of cell growth and contact inhibition of growth. If the conditions in which cells are cultured are optimal, the cells will grow rapidly; mammalian cells typically grow in culture with generation times (lag phase) from 12 to 24 hours. And then cells grow rapidly in an exponential (or log ) phase, and then gradually slow and finally reaches a point where cell growth and division have virtually stopped, even if sufficient nutrients are still present, being in quiescent or stationary phase
The Society of Cells: Cancer and Control of Cell Proliferation 500 Stationar pnase 100 Log phase 10 Lag phas 012345678910 Figure 3.1a. Measuring proliferation rates. Schematic representation of the three stages of a proliferation curve. Time 0 indicates the time of seeding
The Experimental Evaluation of Cell Proliferation 200 Condition A Condition B Figure 3. 1b. Measuring proliferation rates. Experiment comparing the proliferationd similar inocula of a cell line in two different experimental conditions. Time 0 indicat the time of seeding. the cells were exposed to the test media one day after seedi (this is indicated by the arrow). Condition A: chemically defined medium. Conditioni chemically defined medium plus 10% serum made free of sex steroids by adsorptio ith dextran-coated charcoal
Two terms are used to explain the stationary phase of cell growth in culture. One is contact inhibition of growth, it is proposed that contact with other cells produced a response by the plasma membrane which in turn passed a signal on to the metabolic machinery of the cell signaling it not to initiate DNa synthesis or other growth-related activities Another more neutral term is density-dependent regulation of cell growth, which is now more commonly employed to indicate the fact that as cell densities increase, cell growth potential decreases. Actually, two terms are not contradic- tory. While contact inhibition should be an important factor in the control of cell growth, cells living at higher density. i.e, packed against their neighbors, seem to require a higher concentration of growth factors in particular, concentration of serum in medium than those at lower density. Therefore occurrence of contact inhibition of growth is dependent on
Two terms are used to explain the stationary phase of cell growth in culture. One is contact inhibition of growth, it is proposed that contact with other cells produced a response by the plasma membrane which in turn passed a signal on to the metabolic machinery of the cell signaling it not to initiate DNA synthesis or other growth-related activities. Another more neutral term is density-dependent regulation of cell growth, which is now more commonly employed to indicate the fact that as cell densities increase, cell growth potential decreases. Actually, two terms are not contradictory. While contact inhibition should be an important factor in the control of cell growth, cells living at higher density, i.e, packed against their neighbors, seem to require a higher concentration of growth factors in particular, concentration of serum in medium than those at lower density. Therefore, occurrence of contact inhibition of growth is dependent on
upon the concentration of growth factors related to cell densi 2)Serum and growth factors required by cell growth Analyses in recent several years have uncovered a large and growing number of factors referred to growth factor that appear to be able to promote cell growth, at least under certain conditions with certain cells. Serum. which is the fluid phase of the blood after the cells and clotting substances are removed is very complex fluid, containing several hundred different species of proteins, including many isolated or un-isolated factors, which have the ability to cause serum-starved, quiescent cells to initiate DNA synthesis and undergo division. Included among these substances are a number of steroids and non-steroids hormones, cytokines and growth factor peptides e.g. insulin
upon the concentration of growth factors related to cell density. 2) Serum and growth factors required by cell growth Analyses in recent several years have uncovered a large and growing number of factors referred to growth factor that appear to be able to promote cell growth, at least under certain conditions with certain cells. Serum, which is the fluid phase of the blood after the cells and clotting substances are removed is very complex fluid, containing several hundred different species of proteins, including many isolated or un-isolated factors, which have the ability to cause serum-starved, quiescent cells to initiate DNA synthesis and undergo division. Included among these substances are a number of steroids and non-steroids - hormones, cytokines and growth factor peptides e.g. insulin