Stem cell definition

Although we will stick to the IL-6 gene, it should be mentioned at the side that two other RNA polymerases exist in mammalian cells responsible for the synthesis of RNA molecules, which are not translated into proteins ribosomal (rRNA), transfer (tRNA), small nuclear (snRNA), small nucleolar (snoRNA), and some of the recently discovered microRNAs and piRNAs. These RNA molecules act in the process of translation and mRNA turnover. Micro and piRNAs are probably extremely important in the definition of stem cells and of differentiation programs. Some of them are synthesized by RNA polymerase II. 

Schmidt The liver is sort of an example, and the practical answer to the question of why it is useful to know is because sometimes we want to reconstitute livers. When you do a two-thirds partial hepatectomy all the cells divide. Suppose you push this to a limit and take out 90% of a liver, the hope is that there is something called a liver stem cell which is at something called GO, which is capable of reconstituting 90% as opposed to 67%. Is this a practical definition of GO ... 

Nasmyth I m confused by what you mean by a stem cell. What is your operational definition ... 

We have included gene therapy and stem cells to present a more comprehensive perspective on medical treatments, although they are not drugs by our conventional definitions. 

Dzierzak E (2003). Ontogenic emergence of definitive hematopoietic stem cells. Curr. Opin. Hematol. 10 229. 

Zambidis ET, Peault B, Park TS, Bunz F and Civin Cl (2005). Hematopoietic differentiation of human embryonic stem cells progresses through sequential hemato endothelial, primitive, and definitive stages resembling human yolk sac development. Blood 106 860-870. 

Acronyms and Definitions Mesenchymal Stromal Cells Somatic Stem Cell Therapy Good Manufacturing Practice Cell-Based Medicinal Products Human Platelet Lysate... 

Sometimes, the presence of a noisy symptomatology can make the initial clinical examination difficult, although the latter enables to draw up a prognosis and mostly to drive the surgical care. The condition of the cornea is the major element in the definition of the surgical behavior. It is crucial to know whether there is or is not destruction of the limbal stem cells. 

Schematic representation of the hematopoietic cascade in mice and human (hum). All the cells of the hematopoietic system are positive for antigen CD45. Based on this, the dynamics of surface antigen expression along development of different mature cells derived from the hematopoietic stem cell system can be observed. Rounded arrows indicate self-renewal potential. Smooth thinner arrows indicate directions of cellular differentiation. The identification of CDs (clusters definition) and other antigen cell markers are listed in the glossary. (LT-HSC - long term hematopoietic stem cell ST-HSC - short term hematopoietic stem cell MPP - multipotent progenitor CLP - common lymphoid precursor CMP - common myeloid precursor GMP - granulocyte-monocyte precursor MEP - megacaryocyte-erythrocyte precursor T - T lymphocyte B - B lymphocyte NK - natural killer cell DC - dendritic cell).

The value of cultured stem cells to toxicology is in their promise as a continuous source of cells that can be induced to express a chosen cell-type-specific mature phenotype. This achievement would address two current limitations in safety testing scarcity of metabolically competent human systems and use of experimental animals. Numerous culture additives and conditions have been identified that cause commitment and partial differentiation along specific lineages, such as retinoic-acid-induced neuronal commitment of mouse embryonic stem cells. However, definition of conditions that produce fully differentiated cells with cell-type-specific function quantitatively similar to that of intact tissue remains problematic and is a high-priority research area in toxicology. 

The second type of promoter polymorphism is a VNTR in the second intron composed of 17-bp repeats (Ogilvie et al., 1996). Ten and twelve sets of repeats are most common (Lesch et al., 1994). Studies with embryonic stem cells and transgenic embryos implicate the VNTR as playing a role in the regulation of transcription, although no definitive links are known between this VNTR and disease states (Torres et al., 2003a). 

Shipitsin, M., and Rolyak, K. (2008). The cancer stem cell hypothesis In search of definitions, markers, and relevance. Lab Invest 88(5), 459-463. 

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