 | Determining whether the cells can be subcultured after freezing, thawing, and replating.
testing whether the human embryonic stem cells are pluripotent by 1) allowing the cells to differentiate spontaneously in cell culture; 2) manipulating the cells so they will differentiate to form specific cell types; or 3) injecting the cells into an immunosuppressed mouse to test for the formation of a benign tumor called a teratoma. |
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stem cells |
Human embryonic germ cells, in contrast, are derived from a five- to ten-week-old fetus.
Adult stem cells typically generate the cell types of the tissue in which they reside. A blood-forming adult stem cell in the bone marrow, for example, normally gives rise to the many types of blood cells such as red blood cells, white blood cells and platelets. |
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The internal signals are controlled by a cell's genes, which are interspersed across long strands of DNA, and carry coded instructions for all the structures and functions of a cell. |
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Stem cells with this property are said to be pluripotent. Embryonic stem cells are one kind of pluripotent stem cell. Another cell type, embryonic germ cells are also pluripotent, but they are derived at a later stage of development. |
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stem cell research |
It has taken scientists many years of trial and error to learn to grow stem cells in the laboratory without them spontaneously differentiating into specific cell types. For example, it took 20 years to learn how to grow human embryonic stem cells in the laboratory following the development of conditions for growing mouse stem cells. Therefore, an important area of research is understanding the signals in a mature organism that cause a stem cell population to proliferate and remain unspecialized until the cells are needed for repair of a specific tissue. |
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Growing cells in the laboratory is known as cell culture. Human embryonic stem cells are isolated by transferring the inner cell mass into a plastic laboratory culture dish that contains a nutrient broth known as culture medium. |
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stem cells in biomedicine |
In a recent study, scientists directed mouse embryonic stem cells to differentiate into DA neurons by introducing the gene Nurr1. When transplanted into the brains of a rat model of PD, these stem cell-derived DA neurons reinnervated the brains of the rat Parkinson model, released dopamine and improved motor function.
Regarding human stem cell therapy, scientists are developing a number of strategies for producing dopamine neurons from human stem cells in the laboratory for transplantation into humans with Parkinson's disease. |
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The primer includes information about stem cells derived from the embryo and adult. Much of the information included here is about stem cells derived from human tissues, but some studies of animal-derived stem cells are also described.
Stem cells differ from other kinds of cells in the body. |
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Human embryonic stem cells are derived from the inner cell mass of a four- or five-day-old blastocyst. Human embryonic germ cells, in contrast, are derived from a five- to ten-week-old fetus.
Adult stem cells typically generate the cell types of the tissue in which they reside. A blood-forming adult stem cell in the bone marrow, for example, normally gives rise to the many types of blood cells such as red blood cells, white blood cells and platelets. |
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embryonic stem cells |
Embryonic stem cells that have proliferated in cell culture for six or more months without differentiating, are pluripotent, and appear genetically normal, are referred to as an embryonic stem cell line. |
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Until recently, it had been thought that a blood-forming cell in the bone marrow � which is called a hematopoietic stem cell � could not give rise to the cells of a very different tissue, such as nerve cells in the brain. |
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embryonic stem cells |
The cells divide and spread over the surface of the dish. The inner surface of the culture dish is typically coated with mouse embryonic skin cells that have been treated so they will not divide. This coating layer of cells is called a feeder layer. The reason for having the mouse cells in the bottom of the culture dish is to give the inner cell mass cells a sticky surface to which they can attach. |
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embryonic stem cells |
Embryonic stem cells, as their name suggests, are derived from embryos. Specifically, embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro � in an in vitro fertilization clinic � and then donated for research purposes with informed consent of the donors. They are not derived from eggs fertilized in a woman's body. The embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst. |
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stem cells in biomedicine |
For example, it took 20 years to learn how to grow human embryonic stem cells in the laboratory following the development of conditions for growing mouse stem cells. Therefore, an important area of research is understanding the signals in a mature organism that cause a stem cell population to proliferate and remain unspecialized until the cells are needed for repair of a specific tissue. |
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stem cells in bioethics |
If the resulting cells continue to be unspecialized, like the parent stem cells, the cells are said to be capable of long-term self-renewal.
The specific factors and conditions that allow stem cells to remain unspecialized are of great interest to scientists. |
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The successful generation of an unlimited supply of dopamine neurons could make neurotransplantation widely available for Parkinson's patients at some point in the future.
Scientists are trying to understand two fundamental properties of stem cells that relate to their long-term self-renewal: 1) why can embryonic stem cells proliferate for a year or more in the laboratory without differentiating, but most adult stem cells cannot; and 2) what are the factors in living organisms that normally regulate stem cell proliferation and self-renewal? Discovering the answers to these questions may make it possible to understand how cell proliferation is regulated during normal embryonic development or during the abnormal cell division that leads to cancer. |
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The successful generation of an unlimited supply of dopamine neurons could make neurotransplantation widely available for Parkinson's patients at some point in the future.
Scientists are trying to understand two fundamental properties of stem cells that relate to their long-term self-renewal: 1) why can embryonic stem cells proliferate for a year or more in the laboratory without differentiating, but most adult stem cells cannot; and 2) what are the factors in living organisms that normally regulate stem cell proliferation and self-renewal? Discovering the answers to these questions may make it possible to understand how cell proliferation is regulated during normal embryonic development or during the abnormal cell division that leads to cancer. |
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