4 replies to this topic

[walpurg]

Suspended animation has been deliberately induced in a species of mouse which does not naturally hibernate. It is the first time such a feat has been achieved, say the procedure’s pioneers.

If a similar response could be triggered in humans, there would be major healthcare benefits and the futuristic idea of putting astronauts into suspended animation on long-haul space flights could move a step closer to reality.

The mice were induced to fall into their deep sleep after being exposed to hydrogen sulphide - the gas which gives rotten eggs and stink bombs their characteristic foul odour. The animals later revived in ordinary air.

Mark Roth, head of the team which pioneered the procedure at the Fred Hutchinson Cancer Research Center in Seattle, US, explains that hydrogen sulphide all but shuts down the body’s usual demand for the oxygen it needs to keep cells ticking over. Usually, cells denied oxygen - after a heart attack or stroke, for example - die quickly.

But hydrogen sulphide instead sends cells into a state of dormancy. “You’re shutting down the cellular hunger for oxygen,” says Roth, delaying the cells’ oxygen-starvation and buying time for medical treatment.

more here:

Blackstone E., Morrison M. & Roth M. B. /Science/, *308*. 518 (2005).

and

http://www.newscient...le.ns?id=dn7294

and

http://news.bbc.co.u...ure/4469793.stm

and

http://www.nature.co.../050418-13.html

[bgwowk]

I still have to read the original paper, but it looks to me like this is being greatly overdone by media. The most significant aspect of the discovery is that they seem to have found a simple way to control the thermostat of non-hibernating mammals. That certainly merits publication in Science. But all the rest of the claims about this being a new and unique way to reduce oxygen demand is not supported by the data in these media reports. Why? Because two ways have been known for ages to reduce oxygen demand: Anesthesia and *hypothermia*. If the primary effect of this agent is to induce hypothermia, then of course oxygen demand is going to be reduced. Duh! The key question is whether the oxygen demand is lower than it would be with ordinary anesthesia and induced hypothermia at the same temperature (already used clinically in medicine, by the way). The claimed metabolic reduction looks about the same to me.

---BrianW

[jaydfox]

What concerns me is that they only conducted the experiment for six hours at a time. How long can a non-hibernating mammal survive at these temperatures, and is their lifespan extended?

That's what we should be comparing against. More importantly, can we shut these mice down for days, weeks, months? What about if they're given a supplemental nutritional IV drip, since they're obviously not eating while they're knocked out? How long can this state be sustained, and will they waste away/atrophy severely? Are there lifespans shortened? Lengthened?

Six hours is "neat", but it's hardly a proof of concept of suspended animation of the sort that would be useful for much, other than perhaps as a substitute or supplement for anaesthesia/hypothermia for surgery.

[wraith]

Well, it'll be fun to read about when they do more studies.

I posted this on the other thread:
http://www.imminst.o...t=0

I can't find the words to describe how this story makes me feel!!!

I did my MSc on dormancy in marine copepods (Acartia spp.). I wanted to study intracellular pH and metabolic activation in dormant encysted embryos. Due to intractable methodological issues, I wound up just doing a description of developmental changes in the activated embryos.

But I had my speculations as to the environmental triggers which caused activation. Light was always thought to be the cue, but that made no sense to me, nor did temp changes since I extracted the cysts in darkroom conditions and put them in the fridge. They hatched out anyway, at 5deg C. It had to be one of two things: exposure to O2 or removal of H2S. I'm not sure my speculations (since that's all they were) even made it into my thesis, just my defense and I'm sure no one remembers...

Joy, anguish, all at once. At least someone figured it out. And that it applies to mammals, too! I'd always hoped the intracellular pH stuff would lead to something. This was more than I could ever have hoped for.

These critters can stay dormant in marine mud for years. The details of how they do it are not known. Artemia, the brine shrimp, has been studied much more extensively. Artemia's cysts are dessicated, and packed with trehalose. I was unable to determine the internal hydration state of the copepod cysts (someone with some patch-clamp equipment might be able to do so). Trehalose? I assume so, but don't know.

Edited by wraith, 24 April 2005 - 02:04 AM.

[bgwowk]

jaydfox wrote:

Six hours is "neat", but it's hardly a proof of concept of suspended animation of the sort that would be useful for much, other than perhaps as a substitute or supplement for anaesthesia/hypothermia for surgery.

Indeed. Steve Harris' first reaction on hearing this was, "20 years ago we did this to dogs for 4 hours near zero degrees."

http://www.alcor.org...y/html/tbw.html

"They did it to mice for 6 hours at +11 degC. Is that really a breakthrough?"

I've been doing it to myself at +37 degC for almost 400,000 hours now.

---BrianW