Animal tissue culture is an important tool in modern biology. It has been put into many practical uses relating to human welfare. The important uses of animal tissue cultures are:
Organ culture refers to the rearing of an organ in vitro from an appropriate tissue. The whole organ cannot be grown in vitro as it is made up of different types of cells. The parts of the organ consisting of an identical cells can be made by tissue culture. Artificial skin is example for the organ culture. To get an artificial skin a small piece of skin is excised from a man and cultured on a suitable mesh of fibres in a flask. The artificial skin is used as a skin replacement for severe burns.
For bone marrow transplantation, the bone marrow tissue is grown in vitro to get a large amount of tissue. It is helpful to treat cytokines deficiency and for genetic engineering.
Viruses can grow and multiply only in the living cells. Therefore, animal cell cultures are used to propogate viruses to make vaccines. For example, poliomyelitis virus is grown in mammalian cell cultures to make polio vaccine. The virus is allowed to infect animal cell cultures. The virus multiplies and produces numerous virus particles in the cells. The mature virus particles come out of the animal cells by breaking their cell membranes. The mature culture is treated with hypertonic solution to lyse the cells. The lysate is centrifuged to remove the cell debris. The supernatant is filtered through a high quality filter to get virus particle for vaccination.
The method of fusing two different cells types is called somatic cell fusion or somatic hybridization. The fusion product is called somatic hybrid. Polythene glycol(PEG), electric field, Japanese hemagglutination virus (JHV) and Sendi Virus(SV) are used to induce the fusion between somatic cell. A typical example for somatic hybrid is hybridoma. It is the product of fusion of lymphocyte and myeloma cells. It shares fast growth of myeloma cell. Hybridoma clones produce identical antibodies with a single type of epitope called monoclonal antibodies. They have wide applications in the field of medicine, research and industries.
In genetic engineering recombinant viruses are constructed and allowed to infect eggs or zygotes growing in the nutrient medium. After reaching certain globular stage, the embryo is implanted in to the uterus of a female. The female gives birth to transgenic individuals. The transgenic animal has the inserted gene in all its cells. Therefore, cell culture is believed to be an inevitable step in animal genetic engineering.
Sperm bank is a collection of semen from farm animals, fishes, oysters or man stored in liquid nitrogen. It supplies semen timely when and where it is in need. Semen is collected from farm animals by using artificial vagina (AV), electro-ejaculation or massage method and diluted properly by adding a proper dilutent. The diluted semen is transferred to tubes and the tubes are capped tightly with a metal foil. The closed tubes are then kept in a can fitted in a large container having liquid nitrogen. The can is preserved at-196 for indefinite time before use. The semen tube is exposed to 37ºC for a few hours. Then the semen is introduced in to the uterus of the female by mechanical means without casual mating. This method of insemination is called artificial insemination.
The process of fertilizing an egg with a sperm in a nutrient medium in the culture plate is known as in vitro fertilization(IVF). This method is practiced in farm animals women having damaged fallopian tubes. It overcomes the difficulties in fertilization in such individuals.
Unfertilized eggs are collected from the female and placed in the nutrient solution in a culture plate. Semen is collected from a male and added in the plate to fertilize the eggs. The culture plate is then incubated at 37ºC for a few days till the fertilized eggs reach 8-16 celled stage. The globular embryo is then implanted in to the womb of the female. After a suitable period of conception the female produces a young one.
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