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tissue culture,the propagation of plants through the placement of small amounts of undifferentiated tissue or single cells in an artificial environment. The tissue is placed in a nutrient medium that favors the production of roots and shoots, and is later planted normally. By using tissue culture, the favorable qualities of plants can be precisely controlled, so that each plant is identical for the particular quality being sought, whether it be disease resistance or plant chemical production. In 2012 the technique was reported to have been used by Russian scientists to grow plants from Siberian campion fruits dated at 31,800 years old.
explantation, in biology, a method of keeping cells, tissues, or small organs (or parts thereof) alive after being isolated from the body (human, animal, or plant).
The first successful attempts at tissue culture were made in 1907 by the American scientist R. Harrison, who placed a piece of the rudimentary nervous system of a frog embryo in a drop of lymph. The cells survived several weeks and developed nerve fibers. The method was perfected by the French scientist A. Carrel, the American M. Burrows, and the Russian scientist A. A. Maksimov, who used blood plasma or extract from embryonic tissue as the medium.
The main prerequisite for successful tissue culture is the strict maintenance of sterility. The cultivation of pieces of organs has clarified a number of questions of histogenesis and the genetic relations between tissues (N. G. Khlopin, 1940) and the sensitivity of tissues to various factors.
The development of the method of tissue culture took an important new turn with the discovery that a cell suspension could be cultivated when obtained from any tissue under the influence of the proteolytic enzyme trypsin, which dissolves intercellular substance. A synthetic liquid nutrient medium containing physiological solution, 12 amino acids, vitamins, glucose, and (as a rule) blood serum (2-10 percent) is used for such cell cultures. Penicillin and streptomycin must be added to the medium.
A variety of vessels can be used for tissue culture, depending on the purpose. These include depression slides (for hanging-drop cultures), bottles, test tubes, separating flasks, and fermentation tubes. The cells of the suspension cling to the vessel walls (stationary monolayer cultures) or remain suspended in spinning vessels (suspension cultures).
A medium consisting of agar or gelatin and physiological saline (with the additives mentioned) is used for organ cultures. Organs are sometimes cultured on the surface of the vitelline membrane of a hen’s egg or on a porous plastic filter called a float.
Cell cultures are divided into three categories, according to the extent to which they adapt to existence outside the organism: (1) primary cultures, which can be obtained from almost any organ but survive only 20–30 days, even with a systematic change of medium (passage); (2) diploid strains, obtained under special conditions from human and animal embryonic tissues, characterized by stability of biological properties (specifically, constancy of the diploid chromosomal set), and surviving unchanged for ten or 12 months (50 passages); and (3) transplantable (stable) strains, completely adapted to existence outside the organism, obtained from normal and malignant tissues, and reproducing indefinitely. Cells of different cultures differ morphologically. In primary cultures, a distinction is made, according to origin, between fibroblastlike and epithelioid cells.
Cell cultures are excellent for studying the effects of physical, chemical, and biological factors on the cell, and they are particularly important in virology. Since certain groups of viruses cause specific harm in cell cultures, the cultures can be used to identify the viruses. Cell cultures can also be used as a substrate for live antiviral vaccines. A number of general biological problems can be studied in tissue culture: the interrelations between cells and tissues, cellular differentiation, the laws of mitosis, and the transformation of normal cells into malignant ones. Organ culture is widely used to study the patterns of embryonic development under normal and experimentally altered conditions. Organs from animals of different ages and sexes can be cultured together.
REFERENCESPaul, J. Kul’tura kletok i tkani. Moscow, 1963. (Translated from English.)
Zalkind, S. la. Zhizn’ ν probirke. Moscow, 1967.
Cells and Tissues in Culture, vol. 1. Edited by E. N. Willmer. London-New York, 1965.
S. IA. ZALKIND