Tissue culture is a division of natural science in which tissue fragments of higher plants and animals are grown outside a living organism. With tissue culture techniques, tissues or cells are multiplied in artificially induced conditions that involve a solid substrate such as glass or cellophane (i.e. plastic wrap) and a complex nutrient medium for the sustenance of cells. Tissue culture is also possible in liquid suspension. Tissue culture techniques find application in the study of cell biology as well as cancer research and virus studies.
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Types of Cell Grown in Culture
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Tissue culture is a general term which is used to signify both organ culture and cell culture. Cell cultures use living cells removed from an organism and placed in a medium for tissue culture. Two types of laminar flow hoods (i.e. vertical and horizontal hoods) are used whose function is removing particulates from the air, heading toward a cultured medium. The cells are propagated in the presence of carbon dioxide because the liquid suspension is treated from time to time with sodium bicarbonate or carbonic acid so that its pH remains the same. An electronic microscope is used to visualize the cells.
Preservation
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Liquid nitrogen is used for the preservation of cultivated cells. Occasionally nitrogen vapor is used but never freezing nitrogen. Freezing nitrogen contains liquid nitrogen crystals that could be detrimental to the soundness of cultured cells because it alters the concentration of electrolytes, dehydration,and pH. To keep liquid or vaporized nitrogen from reaching freezing point, a number of precautions are taken. For example, a cryoprotective agent (i.e. glycerol or dimethyl sulfoxide) is used to protect against the deleterious effects of freezing. The temperature of the cells in a culture medium is maintained close to the melting point of nitrogen because, below -130 degrees C, the growth of nitrogen crystals is slowed down.
Safety Considerations
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Safety precautions are an integral part of tissue culture techniques because all cultures are a latent source of viruses and other harmful microorganisms. Do not venture to eat, drink or smoke at the laboratory premises because hazardous germs may get into your body, which can mean big trouble for your internal organs. Properly clean your hands after experiments and before moving out of the lab. The floors must be sterilized with disinfectants. Use laminar flow hoods whenever experimenting with hazardous substances. It will prevent microorganisms from escaping into the living spaces.
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