cells is the hierarchy of particular cells in living organisms, each of which can subsequently change (differentiate) in a special way (i.e., get the specialization and further develop as a normal cell). Stem cells can divide asymmetrically, so that when the cells are dividing, there is a cell identical to the parent cell (self-reproduction), as well as a new cell, which is able to differentiate.
The most important property of stem cells is that the genetic information contained in its core in so-called “zero point” reference. The fact is that all asexual cells in living organisms (somatic cells) are differentiated, i.e., specialized to perform some functions: bone cells form a skeleton, blood cell are responsible for immunity, and carrying oxygen, nerve cells conducted electrical impulse. A stem cell mechanisms of the differentiation that determine its specialization are not yet activated. They are at the “zero point,” when their genome has not “run” any program and, most importantly, do not started the process of growing.
Stem cells can be turn into any cell of the organism: skin, neural, or blood cells. It was believed that in the adult, no such cells exist, and they can be found only at the very early period of embryonic development. However, in the 70s, Friendenstein and his colleagues discovered stem cells in the mesenchyme (stroma) of “adult” bone marrow, later they became known as stromal cells.
There is a very small number of stem cells in our body: in embryo, it is 1 cell per 10,000, and 1 cell per 8.5 million in aged people.
Later, there became available evidence of the existence of stem cells in virtually all organs of adult animals and humans, which allowed to distinguish embryonic stem cells (isolated from embryos at the blastocyst stage – a very early stage of development, when there is no tissue or organs) from regional stem cells (isolated from adult organs or organs of embryos at more later stages), which retain the properties of embryonic stem cells, as evidenced by the detected therein embryonic protein markers.
Stem cells can be isolated and grown in tissue culture. The ability to produce a wide variety of cell types (pluripotency) makes the stem cells the most important regenerative reserve in the body, which is used to fill defects arising due to various circumstances.
For those who have read stem cells free sample research paper topic, the presence of stem cells in the central nervous system may seem particularly surprising. As you may know, the nerve cells are losing the ability to reproduce at the earliest stages of neural differentiation (neuroblast stage).
However, stem cells begin to divide with subsequent differentiation into nerve or glial cells in response to various damages to the nervous tissues.
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