Fish Blood Preserves Sperm
In the Arctic and Antarctic seas the water gets cold to minus 1.9 C in winter, but somehow some fish live there. These cold-blooded creatures survive in the icy water because the blood in their veins contains antifreeze proteins and glycoproteins. High levels of the antifreeze proteins are found in the blood serum, they are present in cell cytoplasm and all body fluids except urine. Due to their structure, molecules of antifreeze glycoproteins (AFGP) prevent growth of ice crystals. Natural antifreezes draw researchers` attention as prospective stabilizers for cryobiology. Scientists from the Institute of Cell Biophysics of Russian Academy of Sciences and from the Institute of Fishery have shown that AFGP help to preserve sperm cells at low temperature.
Biologists have often need to save sperm, tissue samples or cell cultures. The preparations are kept in liquid nitrogen at a temperature of -196 degrees C. To prevent their death, the cells are put into a special cryopreserving medium, which is rather toxic. Russian scientists added AFGP to the media and it became possible to half the amount of toxic compounds. The frozen in such way sperm retained its vitality after thawing and at the right amount of antifreeze the spermatozoid activity even increases.
Liquid nitrogen suits well for long-term storage, but in some cases it is not convenient. After few days nitrogen evaporates and needs replenishment. You also have to warm up the preparations in a special way so that came to life. Not all cells stand very low temperatures, for example, donor organs are not put into liquid nitrogen and they do not have to be kept for several months. If a material should be preserved for several days, it is put into the refrigerator, where the temperature is 4 C. Still, many cells die even in these conditions. The scientists have found that AGFP help in these cases too. They have experimented with sperm of middle-Russian carp. The antifreeze was extracted from the blood serum of cod Gadus morrhua, which lives in the Barents Sea. Usually only 60% of sperm survive after one hour storage in the fridge and 5% after 5 day storage. Adding antifreezes resulted in 2.5 to 6 times increase in the cell activity (the result depended upon the time of storage and the solution composition). AGFP are active in concentration of 2-10 mg/ml.
The researchers suppose that antifreezes interact with cell membrane and do not let it destruct because of freezing. Antifreezes are a mixture of glycoproteins. They can be separated into fractions, but the fractions are ineffective when used alone. Only adding them in their natural proportions protects from freezing. Why? The answer is to be found in further studies. The scientists believe that their discovery is perspective for researches in genome cryopreservation, low temperature storage of reproductive cells of farm animals and also in medicine researches – to provide organs and tissues preservation.
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