beyond reason
Abstract
Mononuclear cells generate a variety of hormone‐like proteins termed growth factors that are instrumental in the evolution and resolution of inflammatory reactions. Many of these growth regulatory molecules have multifunctional properties. For example, the mononuclear cell‐derived growth factors, platelet‐derived growth factor (PDGF), and transforming growth factor beta (TGF‐β), are potent leukocyte chemoattractants. In addition, TGF‐β, a product of platelets, T lymphocytes, and monocytes, appears to induce the transcription of other monocyte‐derived growth hormone genes.
In this regard, picomolar concentrations of TGF‐β stimulate peripheral blood monocytes to transcribe the genes for PDGF (c‐sis), basic fibroblast growth factor (FGF), interleukin 1 (IL‐1), and tumor necrosis factor (TNF).
Furthermore, levels of mRNA for TGF‐β, which is constitutively expressed in resting monocytes, are also increased by exogenous TGF‐β. Each of these monocyte products exhibits a plethora of biological activities on other cell types. T lymphocytes, in response to antigen, contribute to this network by secreting growth factors and lymphokines that regulate monocyte growth factor production.
참고) 골격근은 다핵세포
내장근육은 단핵세포
위키디피아
A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation.[1] Usually it is a secreted protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes. Growth factors typically act as signaling molecules between cells. Examples are cytokines and hormones that bind to specific receptors on the surface of their target cells. They often promote cell differentiation and maturation, which varies between growth factors. For example, epidermal growth factor (EGF) enhances osteogenic differentiation,[2] while fibroblast growth factors and vascular endothelial growth factors stimulate blood vessel differentiation (angiogenesis).
Versus cytokines
Growth factor is sometimes used interchangeably among scientists with the term cytokine.[3] Historically, cytokines were associated with hematopoietic (blood and lymph forming) cells and immune system cells (e.g., lymphocytes and tissue cells from spleen, thymus, and lymph nodes). For the circulatory system and bone marrow in which cells can occur in a liquid suspension and not bound up in solid tissue, it makes sense for them to communicate by soluble, circulating protein molecules. However, as different lines of research converged, it became clear that some of the same signaling proteins which the hematopoietic and immune systems use were also being used by all sorts of other cells and tissues, during development and in the mature organism.
While growth factor implies a positive effect on cell proliferation, cytokine is a neutral term with respect to whether a molecule affects proliferation. While some cytokines can be growth factors, such as G-CSF and GM-CSF, others have an inhibitory effect on cell growth or cell proliferation. Some cytokines, such as Fas ligand, are used as "death" signals; they cause target cells to undergo programmed cell death or apoptosis. The growth factor was first discovered by Rita Levi-Montalcini, which won her a Nobel Prize in Physiology or Medicine.
Classes[edit]
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Individual growth factor proteins tend to occur as members of larger families of structurally and evolutionarily related proteins. There are many families, some of which are listed below: