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Controlled-rate and slow freezing, also known as slow programmable freezing (SPF), [18] is a technique where cells are cooled to around -196 °C over the course of several hours. Slow programmable freezing was developed during the early 1970s, and eventually resulted in the first human frozen embryo birth in 1984. Since then, machines that ...
The ultimate objective is to freeze the specimen so rapidly (at 10 4 to 10 6 K per second) that ice crystals are unable to form, or are prevented from growing big enough to cause damage to the specimen's ultrastructure. The formation of samples containing specimens in amorphous ice is the "holy grail" of biological cryomicroscopy. [citation needed]
At least six major areas of cryobiology can be identified: 1) study of cold-adaptation of microorganisms, plants (cold hardiness), and animals, both invertebrates and vertebrates (including hibernation), 2) cryopreservation of cells, tissues, gametes, and embryos of animal and human origin for (medical) purposes of long-term storage by cooling to temperatures below the freezing point of water.
A cryoprotectant is a substance used to protect biological tissue from freezing damage (i.e. that due to ice formation). Arctic and Antarctic insects, fish and amphibians create cryoprotectants (antifreeze compounds and antifreeze proteins) in their bodies to minimize freezing damage during cold winter periods. Cryoprotectants are also used to ...
Egg-freezing may be used in this case to preserve eggs as opposed to Oocyte cryopreservation. [ clarification needed ] [ citation needed ] Those undergoing treatment with assisted reproductive technologies who do not consider embryo freezing an option often look towards Oocyte cryopreservation as an alternative option.
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The technique is used to homogenize cells and tissues, release intact organelles, prepare cell membranes, release labile biochemicals, and produce uniform and repeatable homogenates without subjecting the sample to extreme chemical or physical stress. The method is particularly well suited for treating mammalian and other membrane-bound cells. [14]
This method relies on the mechanism of freeze dehydration to pull water out of the cells and thus prevent ice formation in the cell. [9] Vitrification. By freezing at an ultra-fast rate and using osmotic dehydration, the water that is still present in the cell is unable to form crystals and will be part of a glass-like or vitrified solution. [10]