Liquid nitrogen is a more convenient cold source, because of the nature of the liquid nitrogen, has gradually attracted people's attention and recognition, get more and more widely used in animal husbandry, medical industry, food industry, and the low temperature field etc.. In electronic, metallurgical, aerospace, mechanical manufacturing and other applications continue to broaden and develop.
1 、 widely used in livestock frozen matching improvement techniques
In many domestic animals, the semen preparation and preservation technology is the most successful. Since 50s of last century, a complete set of technological process has been formed.
The cold source of frozen semen is widely used in liquid nitrogen. The granule semen is dripped on the liquid cooled fluorine plate (polytetrafluoroethylene), copper gauze and aluminum plate. To make the surface of the sperm to be maintained with the liquid nitrogen surface - set the distance (1~2 cm). In the process of freezing, the temperature of -80 ~ -120 degrees should be maintained. Prior to freezing, the balanced semen is thoroughly mixed and the motility of the sperm is checked. Drop quickly, the particles should be uniform, each diluted by 10 drops of semen is appropriate. After freezing, stay for 2~3 minutes until all the particles have been frozen and immediately put into liquid nitrogen. After sampling (2 randomly selected), the thawing rate is above 0.3, which can be placed in gauze bags and stored in liquid nitrogen after labeling. After each droplet has frozen the semen of a bull, the plate must be replaced. At present, the capacity of the tube is 0.25 ml and 0.5 ml, two by non-toxic plastic (polyvinyl chloride) made. One end of the tube filled with cotton plug and polyethylene powder, powder curing automatic sealing water, and push the piston into the insemination semen; the other end in semen after injection, can be polyethylene powder or steel (or plastic beads) seal, the seal should be paid attention to in the semen and stay between 10 ~ 13 mm space and prevent the expansion caused by tube burst due to the freezing process.
Semen storage, frozen semen of cattle is stored in liquid nitrogen as a cold source, and can be removed whenever necessary. In order to prevent the influence of temperature change on semen quality, the taking and taking action should be rapid, and the stay time in the air can be reduced as much as possible. When the frozen semen is extracted from the storage vessel, the semen should not exceed the base of the liquid nitrogen container, so as to avoid the decrease of the thawing rate of semen due to the rise of temperature. Frozen semen has been in the cattle for more than 40 years. Tests have shown that cryopreservation of frozen semen still has the ability to fertilize. But it is generally believed that the sperm viability of semen decreases with the prolongation of preservation time. The exact time limit for long-term preservation of frozen semen in cattle remains to be studied and observed.
2 、 embryo preservation was carried out in the embryo transfer of domestic animals and many animals
At present, embryo freezing apparatus is used as an intelligent freezer. The instrument adopts microcomputer control technology, and special software can control the release amount of liquid nitrogen more accurately, so as to ensure the frozen biological product to be cooled at an appropriate freezing rate.
3. Cryopreservation technology of liquid nitrogen at ultra low temperature
Long term preservation method of liquid nitrogen stored at -196 DEG C, the principle is that microorganisms can effectively preserve microorganisms under the metabolism of -130 at the end of the temperature. Fungi are an important group of fungi (fungi, large fruiting body formation in mushrooms refers to generalized mushrooms or mushroom), many species have high nutritional value and medicinal value, is a kind of fungi in the current development and application; in addition, some fungi can break down dead plants have an important role to maintain the material circulation of the natural and ecological balance, can be applied to the development of paper industry and environmental purification; some fungi can cause disease or damage to a variety of trees wood products, strengthen the understanding of the pathogenic fungi, conducive to the prevention and reduction of the danger. The standardized preservation of large fungi is of great significance for the safe, efficient preservation of microbial strain resources and for the long-term preservation of genetic resources, remote preservation and sharing of biological diversity
4. Gene conservation in agricultural organisms
Shanghai invested about 41000000 yuan to start the construction of the first comprehensive agricultural biological gene pool in china. The seed industry, which has the greatest potential for national market development, will use the gene pool as a source of breeding materials, agricultural sources say. The total construction area of over 3300 square meters of Shanghai agricultural biological gene pool, located in Shanghai Agricultural Academy of Sciences, the preservation of plant seeds, plant materials in vitro, animal germ cells, genetic engineering microorganism and plant materials five categories of agricultural biological genetic resources.
5. Preservation of liquid nitrogen vaccine
Liquid nitrogen is mid 80s seedlings gradually popularized, the first is the use of type III -FCl26 with chicken herpes virus vaccine liquid nitrogen at home and abroad, and later developed SBl, 301 / B, Z4814 type liquid vaccine, and combined into two type II+III and I+II+III price of seedlings after application of trivalent vaccine, once effective control the Marek's disease in some areas, II+III price of two Haojing seedlings is not long, in 1993, Marek's disease and the emergence of large scale epidemic in North America and the Yan state region, for the effective control of Marek's disease, some countries began to study in Holland since 1927 the use of I type CVl988 / Rispens liquid nitrogen after seedling, effective control of Marek's disease experience, United States, Canada, Brazil, Japan and Europe have from the Holland Department of agriculture and fisheries for the introduction of CVl988 / Rispens system for the production of different drugs, the use of technology in their respective countries, Paul Stored in liquid nitrogen tanks.
6, using liquid nitrogen to treat cow nipple hole outside the mouth closed, livestock skin tumor is relatively common.
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