X-Message-Number: 7473 From: Brian Wowk <> Date: Fri, 10 Jan 1997 00:05:46 -0600 Subject: Frogs and Mummification Henry R. Hirsch <> writes on CryoNet: >1. Has glucose been studied as a cryoprotectant in humans or > other mammals? Yes, although typically as a component in solutions containing more penetrating cryoprotectants. Its utility as monoagent is limited. > >Background: Glucose serves as the major cryoprotectant in the >freeze-tolerant frog R. Sylvatica (1). If effective, advantages to its >use in human cryonics patients would include: (a) Apart from glycosylation >reactions, it is nontoxic. (b) It crosses the blood-brain barrier. Unfortunately it doesn't penetrate cells very well (compared to other cryoprotectants), so it has osmotic toxicity at high concentrations. Like all solutes, it also has direct biochemical toxicities at high concentrations. Whenever you replace water molecules with other molecules, you will inevitably denature macromolecules beyond some threshold concentration. (Tip: Anyone who finds the magic formula for an unfreezable liquid that proteins can't distinguish from water will win Nobel Prizes for both chemistry and medicine.) The problem with extending strategies employed by overwintering amphibians like Rana Slyvatica to human organ crypreservation is that you have to replace much more water with cryoprotectant to survive cooling to -130'C than you do to survive cooling to -20'C. Amphibian organs have also evolved to survive quantities of ice and concentrations of cryoprotectant that are lethal to humans. >2. Has glucose been studied as a "dryoprotectant", i. e. a >substance which stabilizes cell membranes against dehydration? Suffice it to say that while numerous mammalian tissues and even some organs can survive cryopreservation, NONE have ever been shown to survive dessication and rehydration. (Organisms that survive complete dehydration have no doubt evolved proteins uniquely suited to the trick.) So mummification is not currently currently pursued as a promising approach to suspended animation. A good way to get up to speed on the cryobiology most relevant to suspended animation is to read the vitrification review article on the Prometheus Project Web site: http://www.prometheus-project.org/prometheus and look up some of the references at the end. Perusing back issues of the journal Cryobiology is also a useful for getting an impression of the field. *************************************************************************** Brian Wowk CryoCare Foundation 1-800-TOP-CARE President Human Cryopreservation Services http://www.cryocare.org/cryocare/ Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=7473