http://news.yahoo.com/s/livescience/[WORD TOO LONG]
http://tinyurl.com/2aut4gp
Mystery Explained: How Frozen Humans Are Brought Back
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When subjected to literally freezing temperatures, the embryos of yeast and garden worms do not live, researchers found. A full 99 percent of those in the experiment died after 24 hours of exposure to temperatures just above freezing.
But, when first deprived of oxygen in the manner described above, 66 percent of the yeast and 97 percent of the garden worms survived. Upon re-warming and reintroduction of oxygen, the "two widely divergent organisms" reanimated and showed normal life spans, said scientists in a statement.
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Documented cases of humans successfully revived after spending hours or days without a pulse in extremely cold conditions first inspired Roth to study the relationship between human hypothermia and his own research in forced hibernation.
In the winter of 2001, the body temperature of Canadian toddler Erica Norby plunged to 61 degrees Fahrenheit (16 degrees Celsius) as she lay for hours in below-freezing weather after wandering outside wearing only a diaper. Apparently dead, she recovered completely after being re-warmed and resuscitated.
The same curious fate befell Japanese mountain climber Mitsutaka Uchikoshi in 2006, who was discovered with a core body temperature of 71 degrees F (22 degrees C) after 23 days after falling asleep on a snowy mountain.
"We wondered if what was happening with the organisms in my laboratory was also happening in people like the toddler and the Japanese mountain climber. Before they got cold did they somehow manage to decrease their oxygen consumption? Is that what protected them?" Roth said. "Our work in nematodes and yeast suggests that this may be the case, and it may bring us a step closer to understanding what happens to people who appear to freeze to death but can be reanimated."
Oxygen deprivation's protective effect comes from the way it arrests biological processes before dangerous instabilities can develop. When reanimated, the processes continue where they left off, with no sign of disruption having occurred.
"When an organism is suspended its biological processes cannot do anything wrong," Roth said. "Under conditions of extreme cold, sometimes that is the correct thing to be doing; when you can't do it right, don't do it at all."
The ultimate goal of such research is to "buy time" for patients in physical shock, such as after heart attacks and severe blood loss, increasing their chances of survival by preserving them until they can reach medical care, researchers said in a statement. Other forms of forced hibernation include exposure to chemical agents like hydrogen sulfide.
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I remember reading about "suspended animation"-type experiments with taking a mouse and placing it a chamber in air, which is mostly nitrogen and oxygen as you know, then slowly replacing the atmosphere with hydrogen sulphide and the animal appears dead but can be resuscitated apparently without harm having occured.
OK google gives this :
http://www.physorg.com/news185337640.html
One potential explanation for this phenomenon I remember centres around the fact that H2S is employed by many bacteria to strip energy from nutrients - fermentation - as the terminal electron acceptor along an electron transport chain, whereas oxygen is used by aerobic organisms to perform respiration. So here H2S occupies a position like at the base of a hill (thermodynamic gradient) where energy is removed on descent of a bouncing ball rolling from the top.
As the mitochondria that perform this function in the cells of mice (and men) is an endosymbiont (engulfed bacterium according to Margulis' theory) then H2S may be able to replace oxygen for stripping energy from carbohydrates but at a much reduced ability so a type of ancient fermentation could replace respiration in mammalian cells. This is similar to the ability of cyanide to competively inhibit the cytochrome oxidase enzyme and cause chemical asphyxiation which is probably why high concentrations of H2S are fatal like CO inhibiting O2 binding haemaglobin. It appears to have applications now in preserving patients organs.
http://en.wikipedia.org/wiki/Hydrogen_sulfide#Induced_hypothermia
Induced hypothermia
In 2005, it was shown that mice can be put into a state of suspended animation-like hypothermia by applying a low dosage of hydrogen sulfide (81 ppm H2S) in the air. The breathing rate of the animals sank from 120 to 10 breaths per minute and their temperature fell from 37 °C to just 2 °C above ambient temperature (in effect, they had become cold-blooded). The mice survived this procedure for 6 hours and afterwards showed no negative health consequences.[30] In 2006 it was shown that the blood pressure of mice treated in this fashion with hydrogen sulfide did not significantly decrease.[31]
A similar process known as hibernation occurs naturally in many mammals and also in toads, but not in mice. (Mice can fall into a state called clinical torpor when food shortage occurs). If the H2S-induced hibernation can be made to work in humans, it could be useful in the emergency management of severely injured patients, and in the conservation of donated organs. In 2008, hypothermia induced by hydrogen sulfide for 48 hours was shown to reduce the extent of brain damage caused by experimental stroke in rats.[32]
As mentioned above, hydrogen sulfide binds to cytochrome oxidase and thereby prevents oxygen from binding, which leads to the dramatic slowdown of metabolism. Animals and humans naturally produce some hydrogen sulfide in their body; researchers have proposed that the gas is used to regulate metabolic activity and body temperature, which would explain the above findings.[33]
Two recent studies cast doubt that the effect can be achieved in larger mammals. A 2008 study failed to reproduce the effect in pigs, concluding that the effects seen in mice were not present in larger mammals.[34] Likewise a paper by Haouzi et al. noted that there is no induction of hypometabolism in sheep, either.[35]
However, at a February 2010 TED conference, Mark Roth announced that hydrogen sulfide induced hypothermia had completed Phase I clinical trials. He estimated that further trials would take 'a few years.' [36]
Humphry Davey - the man that is principally remembered for inventing the miners lamp - had laughing gas parties with his friends and never appreciated that it could be employed as a painkiller to alleviate human suffering. It took decades more before ether then chloroform and curare where routinely employed.
This incipient field of "suspended animation" strikes me as similar to the early research in anesthesia. Famously "Humbug! Humbug!" was shouted at the dentist Horace Wells when he unsuccessfully tried to demonstrate to medics at Harvard the anesthetic effects of nitrous oxide and it took his colleague the indomitable Crawford Long and the great Scot Simpson to move the field forward. Bizarrely Wells was first exposed to laughing gas after volunteering at a travelling circus show and tragically he never appeared to recover from the ridicule at the hands of the medical profession :
http://en.wikipedia.org/wiki/Horace_Wells
As a result it took a long time and a great many more deaths on the operating table before the field of anesthesiology developed allowing the sophisticated transplantation and other medical and surgical procedures that we now have. As has been mentioned, the present day problem of organ shortages would potentially be impacted upon by having a way to maintain tissues for longer. In addition, this new technology - if trials are performed and safety established - then conceivably other medical interventions might be possible where a "rapid metabolic quiescence" could be induced such as for stroke victims (another terminology than suspended animation might be required to stymie detractors). Similar again to the field of anesthetics delivery technology will have to be developed and ambulances already carry other various potentially dangerous gases safely so why not a canister with H2S as well and some kind of breathing apparatus for the patient if clinical utility is demonstrated.
One possible concern I would have with this proposed new way for preserving tissues is what epigenetic effects might occur in cells exposed to low oxygen/high hydrogen sulphide environments (that is changes in gene expression not due to underlying changes in genomic DNA : http://en.wikipedia.org/wiki/Epigenetics), not to mention possible direct mutagenic effects of the chemical. You might suspect that in an anoxic environment with the resulting decreased metabolic turnover genetic mutation might well be low - although this would need to be formally demonstrated by say ultra-deep pyrosequencing of non-treated and time points of treated tissue material. I suspect that some changes in the levels of existing proteins might indeed occur and particularly post-translational protein modification needs assessing which is more difficult to evaluate comprehensively but proteomics by GC- mass spec is one way. Perhaps these studies have been done or are being carried out, i.e. an assessment of potential proteomic and genomic alterations over time on transplant tissues and if they reveal little or no detectable changes over time in storage then I think this is indeed a viable technology and smells not so much of rotten eggs anymore but maybe more like Noble prizes.