Posted on 10/07/2005 1:53:36 PM PDT by law of conservation
Stem cells have two important characteristics that distinguish them from other types of cells. First, they are unspecialized cells that renew themselves for long periods through cell division. The second is that under certain physiologic or experimental conditions, they can be induced to become cells with special functions such as the beating cells of the heart muscle or the insulin-producing cells of the pancreas.
Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells and adult stem cells, which have different functions and characteristics that will be explained in this document. Scientists discovered ways to obtain or derive stem cells from early mouse embryos more than 20 years ago. Many years of detailed study of the biology of mouse stem cells led to the discovery, in 1998, of how to isolate stem cells from human embryos and grow the cells in the laboratory. These are called human embryonic stem cells. The embryos used in these studies were created for infertility purposes through in vitro fertilization procedures and when they were no longer needed for that purpose, they were donated for research with the informed consent of the donor.
Stem cells are important for living organisms for many reasons. In the 3- to 5-day-old embryo, called a blastocyst, stem cells in developing tissues give rise to the multiple specialized cell types that make up the heart, lung, skin, and other tissues. In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.
It has been hypothesized by scientists that stem cells may, at some point in the future, become the basis for treating diseases such as Parkinson's disease, diabetes, and heart disease.
Scientists want to study stem cells in the laboratory so they can learn about their essential properties and what makes them different from specialized cell types. As scientists learn more about stem cells, it may become possible to use the cells not just in cell-based therapies, but also for screening new drugs and toxins and understanding birth defects. However, as mentioned above, human embryonic stem cells have only been studied since 1998. Therefore, in order to develop such treatments scientists are intensively studying the fundamental properties of stem cells, which include:
determining precisely how stem cells remain unspecialized and self renewing for many years; and identifying the signals that cause stem cells to become specialized cells.
Stem cells have potential, but that doesn't mean using them is right.
But, they are worth talking about.
Pioneering work, and still virtually all known about stem cels, has been done in bone marrow cells. These are cells in adults that last throughout the entire life of a mammal and give rise to all the cells of the blood.
Interestingly, given the life long self-renewing properties of stem cells, embryonic stemm cells actually can't be considered stem cells by this criteria as they are very short lived, being present only in the early developmental stages of the organism.
law of conservation aka king of smears, master thesis, under the creator, chaos theory, et al, zotted again.
This NIH Stem Cell primer is years old.
Get lost troll.
Stupidity is defined by YOUR multiple returns to FR in the thought that somehow we won't spot you.
I.E., "Doing the same thing over and over again and expecting a different result."
He doesn't understand the law of conservation!
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