Sunday, June 6, 2010

Here’s one from the Whatever-Happened-To department: Cryonics. The idea was that a life could be suspended if lowered to subzero temperatures (typically at -196 degrees F ) for an indefinite period of time. The rationale being that people who are considered dead by current legal or medical definitions may not necessarily be dead according to more stringent definitions of death. So, cryopreserved them until they can someday be recovered by using highly advanced technology that is presently not available. Because most chemical reactions slow with decreasing temperature, it stands to reason that lowering a tissue’s temperature will place it in a state of suspended life. Presently cryopreservation is can be done for sperm (for future in vitro fertilization) and other biological tissues such as blood and stem cells.

According to their website, Alcor, ( is a foundation established in 1972 in California. Their mission is to enhance the cryonics movement. In 1987 Alcor “cryopreserved” its first human.

Interesting subject. It contains all the stuff I love to mull over when thinking up plots. On the other hand, the scientist in me always asks, “Whoa, what are some of the risks, the basic problems in biology?” There are several, making the physiology complicated. When tissues are cooled slowly, water migrates out of cells and ice forms in the extracellular space. Too much extracellular ice can cause crush injury to the cell membrane. Also, moving water out of the cell can cause dehydration damage. Although some tissues can tolerate some extracellular ice, most can’t tolerate ice inside the cell. To mitigate some of these problems, tissue can be flash frozen. In 1963 Peter Mazur, at Oak Ridge National Laboratory in the USA, showed that lethal intracellular freezing could be avoided if cooling was slow enough to permit sufficient water to leave the cell during progressive freezing of the extracellular fluid. That rate differs between cells of differing size and water permeability: a typical cooling rate around 1°C/minute is appropriate for many mammalian cells after treatment with cryoprotectants such as glycerol or dimethyl sulphoxide, but the rate is not a universal optimum. Even so, problems arise when trying to thaw frozen tissue.

The issues go on and on, and to me the bottom line is the process is not ready for prime time.

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