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Stem cell

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Embryonic stem cells differentiated to form cells with specialized roles.

A stem cell is a cell or cells found within organisms that can give rise to different or specialized types of cells. Stem cells can be categorized as embryonic, adult and cord blood stem cells. [1]

Animals typically begin life as a hollow ball of identical embryonic stem cells. Then, as dozens of hormones, sugars, growth-promoting substances, and other unknown chemical cues washed over us, we began to change. Certain cells grew long and thin, forming nerve cells. Others flattened into skin cells. Still others balled up into blood cells or bunched together to create internal organs.[2]

Types

Embryonic

Embryonic stem cells are created at the union of the sperm to the egg at the earliest stages of development. They are the only type of stem cell that are completely generic. Its gene expression is tuned so broadly that it has unlimited career potential to become any kind of cell in the body. These undifferentiated cells cease to exist a few days after conception.[2]

Embryonic Stem Cell Research is usually considered as unethical by individuals who are pro-life and believe that life begins at conception, when the sperm unites with the egg. During embryonic stem cell research, most cells are destroyed or die due to complications.

Adult

After embryonic stem cells have differentiated, we still harbor other types of multitalented cells, called adult stem cells. These cells are found throughout the body, including in bone marrow, brain, muscle, skin, and liver. They are a source of new cells that replace tissue damaged by disease, injury, or age. Researchers believe that adult stem cells lie dormant and largely undifferentiated until the body sends signals that they are needed. Then selected cells morph into just the type of cells required.[2]

Like embryonic stem cells, adult stem cells have the capacity to make identical copies of themselves, a property known as self-renewal. But they differ from embryonic stem cells in a few important ways. For one, adult stem cells are quite rare. For example, only 1 in 10,000 to 15,000 cells in bone marrow is capable of becoming a new blood cell. In addition, adult stem cells appear to be slightly more "educated" than their embryonic predecessors, and as such, they do not appear to be quite as flexible in their fate. However, adult stem cells already play a key role in therapies for certain cancers of the blood, such as lymphoma and leukemia. Doctors can isolate from a patient's blood the stem cells that will mature into immune cells and can grow these to maturity in a laboratory. After the patient undergoes high-dose chemotherapy, doctors can transplant the new infection-fighting white blood cells back into the patient, helping to replace those wiped out by the treatment.[2]

Adult stem cells are becoming more and more the focus of attention by researchers due to advances in stem cell research. The scientific community widely recognizes the concerns and advantages of adult stem cells.

  • rejection does not occur as does with embryonic stem cells
  • adult stem cell research and therapy do not require the creation and destruction of an embryo
The use of adult stem cells does not require that an embryo be sacrificed, however." [3]

Uses

Although researchers have been studying stem cells from mouse embryos for more than 20 years, only recently have they been able to isolate stem cells from human embryos and grow them in a laboratory. In 1998, James A. Thomson of the University of Wisconsin, Madison, became the first scientist to do this. He is now at the forefront of stem cell research, searching for answers to the most basic questions about what makes these remarkable cells so versatile. Although scientists envision many possible future uses of stem cells for treating Parkinson's disease, heart disease, and many other disorders affected by damaged or dying cells, Thomson predicts that the earliest fruits of stem cell research will be the development of powerful model systems for finding and testing new medicines, as well as for unlocking the deepest secrets of what keeps us healthy and makes us sick.[2]

Differentiation Potential

There are three main types of stem cell differentiations which describe how certain cells at different stages of an organisms development effect its tissues, organs and nerves.

Totipotent

There is no limitation with totipotent cells which are taken from the inner mass which consists of cells that are truly part of the fetus. The totipotent cells or the inner mass of cells are within the covering of the blastocyst. These are cells produced during the first division of the fertilized egg and their primary function is to make and truly form the various segments or structures that constitute an organism.

Pluripotent

These types of cells are descendants of totipotent cells showing up further in the development of a fetus. They can differentiate into any of the cells derived from the three germ layers of ectoderm, mesoderm, and endoderm. [4] Pluripotent cells however differ from totipotent cells in that they are not able to form a fully functioning fetus. The totipotent cells are and must be established first.

In 2007, two teams of scientists from Japan and the United States were independently altering a few genes within skin cells of humans in order to coax them into becoming pluripotent stem cells, ultimately enabling them to turn these into any of the 200 tissue types. [5] What are called induced pluripotent stem (iPS) cells were exactly like embryonic stem cells in their physical appearance and behavior in the cell culture the Japanese scientists found and published in the journal Cell. Evolutionists for years have claimed that not only the U.S. President, but Christians, specifically creationists who opposed embryonic stem cell research on the grounds of ethics were anti-science. [6]

Multipotent

Cells that can differentiate into any of the blood cell types or what are called Hematopoietic stem cells (HSC). These can be broken down and seen to consist of viable stem cells with short regeneration capacities which are multipotent, oligopotent and unipotent progenitors.[1]

References

  1. 1.0 1.1 Stem cell by Wikipedia
  2. 2.0 2.1 2.2 2.3 2.4 Inside the Cell Chapter 3 On the Job: Cellular Specialties. By Alison Davis. National Institute of General Medical Sciences
  3. Inquiry into Life, 10th edition, Mader, McGraw Hill, page 253
  4. Stem cell by Answers.com
  5. Stem Cell Breakthrough by Creation-Evolution Headlines
  6. Beyond the embryo fight: A recent stem-cell breakthrough negates the need for research using human embryos by Richard Hayes for the LA Times, November 22, 2007

External Links

See Also