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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However, unspecialized stem cells can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells.
Stem cells are capable of dividing and renewing themselves for long periods. |  |
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These tests include.
Growing and subculturing the stem cells for many months. This ensures that the cells are capable of long-term self-renewal. |
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This is a significant scientific advancement because of the risk that viruses or other macromolecules in the mouse cells may be transmitted to the human cells. |
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One of the fundamental properties of a stem cell is that it does not have any tissue-specific structures that allow it to perform specialized functions. A stem cell cannot work with its neighbors to pump blood through the body (like a heart muscle cell); it cannot carry molecules of oxygen through the bloodstream (like a red blood cell); and it cannot fire electrochemical signals to other cells that allow the body to move or speak (like a nerve cell). |
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Examples of such plasticity include blood cells becoming neurons, liver cells that can be made to produce insulin, and hematopoietic stem cells that can develop into heart muscle. Therefore, exploring the possibility of using adult stem cells for cell-based therapies has become a very active area of investigation by researchers.
Embryonic stem cells, as their name suggests, are derived from embryos. |
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Stem cells are important for living organisms for many reasons. In the 3 to 5 day old embryo, called a blastocyst, a small group of about 30 cells called the inner cell mass gives rise to the hundreds of highly specialized cells needed to make up an adult organism. In the developing fetus, stem cells in developing tissues give rise to the multiple specialized cell types that make up the heart, lung, skin, and other tissues. |
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Also, scientists acknowledge that many of the tests they do use may not be good indicators of the cells' most important biological properties and functions. Nevertheless, laboratories that grow human embryonic stem cell lines use several kinds of tests. These tests include.
Growing and subculturing the stem cells for many months. This ensures that the cells are capable of long-term self-renewal. |
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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. 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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