From Big Medical Encyclopedia

FABRIC CAMBIUM (Latin cambium change, exchange) — the low-differentiated cells which are a part of fabrics and having productive capacity and a differentiation (specialization).

The terms «cambium», «cambial cells» are entered by A. A. Zavarzin in the 30th 20 century. Since connected with existence fiziol. angenesis. But, as it became clear later, regeneration (see) can occur also without reproduction of cells. Existence of a cambium does not define ability to regeneration, and indicates only the mechanism of its implementation in specific fabric. Cambial elements, according to A. A. Zavarzin, are not the simple remains of germinal leaves, and them malodifferentsirovannymp descendants. They are located or in the form of single cells among the differentiated cells, napr, in cross-striped muscular tissue, or groups — in a multilayer flat epithelium. In nek-ry cases cambial cells topographical are separated from the differentiated forms (e.g., blast cells of red marrow from blood cells).

Now the terms «cambium», «cambial cells» are used seldom, giving way to more exact definitions — «stem cells» (poliiotentny), the «semi-stem cells» (which are partially determined, or switched). At the beginning of 20 century A. A. Maximov suggested about existence in an organism of a stem hemopoietic cell. In the 00th gt. 20 century this hypothesis was supported with experimental data of Til-la and Mac-Kalloka (J. E. Till, E. A. McCulloch) about existence in blood and the hemopoietic bodies of a polipotentny cell, on morfol. to signs similar to a lymphocyte. Stem cells and for some other fabrics are identified. All of them are characterized by availability of diffusion chromatin in a kernel, the content of one or bigger quantity of kernels, poor development of organellas of cytoplasm, except for free ribosomes (see. Cell ). The form of stem cells of various systems of cellular differentiations is not identical. Contrary to other proliferating cells at division of stem cells descendants are formed, to-rye optional are exposed a further differentiation of therefore can keep the proliferative potential. An essential role in a differentiation of descendants of stem cells is played by a microenvironment. If stem cells — it is long, slowly self-sustaining population of cells, then the switched cells originating from stem cells, intensively, repeatedly breed and exposed to a slow differentiation, in the course the cut at the level of synthesis of information RNA is carried out the program of their determination (see. Histogenesis ). The determined cells cease to react to a microenvironment, but do not become other than that ooze of cells, they belonged to Krom before (e.g., a class of morphologically recognizable proliferating cells of red marrow). Repression of certain genes at the level of broadcast of a genetic code of molecule RNA on the fabric and specific molecules of protein synthesized by a cell is the cornerstone of these processes (see. Gene , Broadcasting ). For the nek-ry partially determined cells the impossibility of the return transition to stem cells is proved. Concerning other cells there are no unambiguous data that, perhaps, is caused by unequal degree of rigidity of determination (programming) of the developing cells and fabrics.

Development of the doctrine about stem cells specifies former representations about Since. Development of methods of identification of stem cells in different fabrics has not only theoretical interest, but also serves the solution of almost important problems, such as a differentiation, regeneration, etc.

See also Blood , Marrow , Muscular tissue , Nervous tissue , Connecting fabric , Epithelial fabric .

Bibliography: Tannin and E. S. Ponyatiye about a fabric kambialnost in modern histology, Usp. sovr. biol., t. 29, No. 3, page 379, 1950; it, Samoobnovleniye of fabrics and theory of a kambialnost of the academician A. A. Zavarzin, Arkh. annate., gistol., and embriol., t. 34, No. 1, page 16, 1957; 3 and - in and r z and A. A. Kurs's N of histology and microscopical anatomy, JI., 1939; it, Chosen works, t. 2, page 217, M. — L., 1953; R and y c and N and S. S. Identification of stem cells in some systems of cellular differentiations at mammals, Usp. sovr. biol., t. 90, century 1(4), page 123, 1980; Fridenstein A. Ya. and L at r and I am E. A. Cellular bases of hemopoietic microenvironment, M., 1980; Chertkov I. L. and Fridenstein A. Ya. Cellular bases of a hemopoiesis, M., 1977.

Yu. I. Afanasyev.