1994, Number 3
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Text ExtractionIt is very important to bear in mind when cryopreserving semen, that the goal is to mantain the following sperm properties like: a) Necessary metabolism to produce energy, b) Plasmatic proteins to survive in the female reproductive tract at the time of fertilization, c) Acrosomal enzymes for the penetration to the ovum, and d) Capacity of progressive movement, in order to fertilize. The main aspect on freezing semen, is to sort the physical and chemical sperm damage that is presented during the cell going through the critic temperature between -15°C and -60°C in the freezing-as well as in the thawing processes. Due to it, in each sperm cell, several problems are produced like the formation of intra- and extracellular crystals, membrane dehydratation and distorsion. In this sense, it is important to know the effects of freezing rates. On one hand, when the freezing rate is high ( › 10-20°C/min), intracellular water cannot leave the cell, and very little crystals are formed. There is no problem, while the cell stays like this, but these crystals are thermo-dynamically unstable and in the thawing process they form bigger crystals that are lethal for sperm. On the other hand, with a low freezing rate (‹ 50°C/min), due to the water leaving the cell, while its surrounding is frozen, intra- and extracellular water cannot find its balance until there is almost no water to freeze and the cell does not freeze, but the amount of extracellular ice is so big, that it causes damage to the membrane on its external side.
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