Bitching About A Cool Thing
Via Jay, a CNN article and a video about a researcher who has managed the rather mind-boggling feat of keeping small animals in suspended animation for hours through extreme oxygen deprivation, and reviving them without apparent consequence.
Obviously, this is awesome, and both the article and the video focus on the wide-ranging and extremely positive implications this would have for medicine. A great number of emergency conditions are emergencies because they must be solved before the patient runs out of oxygen and starts losing cells en masse; if you could put someone with, say, a rupturing aorta into suspended animation, what would have been a case of rapid death turns into a fairly simple repair just because “the patient’s blood is mostly in places that are not his blood vessels” ceases to be as pressing an issue.
So yes, it’s very awesome. They’re having trouble replicating the trick with larger animals, which if I had to guess is likely due to surface-area-to-volume ratio issues with distributing his oxygen-blocker throughout tissues before the chemical cascade that leads to cell death can be triggered (which itself requires SOME oxygen), but that’s the problem: I have to guess. Because CNN won’t even begin to explain how it’s being done. Both the article and the video occasionally range into the territory of elucidating why oxygen isn’t inherently critical for life, and how the good doctor is accomplishing the trick of keeping an energy-greedy creature like a mammal in a state of suspended animation without it, but every time they start to they shy violently from the subject like startled deer and go back to the implications of the potential results.
As is glancingly mentioned but not elucidated, in a lot of biological senses oxygen isn’t so much a godsend as it is a toxin. Like other elements in its neck of the periodic table, oxygen has a habit of forcefully mugging other atoms for their electrons; in fact it is so good at it that the basic chemical reaction of electron loss is called “oxidation”, as early views of chemistry thought that the general class of effects were all caused by oxygen*. When life first evolved on the planet, oxygen was as violently toxic to it as flourine- one of the few more vigorous oxidizers than oxygen- is to us; any contact with oxygen would rip apart delicate biochemical structures like a molecular buzz saw. This is still true for the relatively few remaining obligate anaerobes of this world. When the earliest cyanobacteria stumbled across an incredibly energy-rich metabolic process for using light for energy and taking their carbon from their atmosphere (photosynthesis), it was a planetwide ecological catastrophe because the waste gas was the very toxic oxygen.
Most of the existing diversity did not survive, and most of what did only could because of a series of adaptations that created biochemical defenses against oxygen; any life form that doesn’t react to oxygen like the Wicked Witch of the West did to water has one or more enzymes to disarm it. Catalase** and superoxide dismutases are the near-universal, with a couple of unusual bacterial twists on the theme, but overall, if you want to be exposed to oxygen and live, you need some powerful anti-oxidant capabilities in your biological chemistry set. Surviving oxygen necessarily preceded using it, evolutionarily speaking.
When a doctor refers to respiration, he generally means the act of breathing- muscles, lung tissue, and all. When a microbiologist refers to respiration, he’s probably thinking on the cellular level- whatever set of reactions is used to play electron tennis and use the energy released by the rearranging chemical bonds to convert larger molecules into a form of energy storeable and usable by the cell. Since oxygen has such a pull on electrons, it makes for an extremely efficient driver of one of these processes; a respiratory pathway that uses oxygen as the final acceptor of an electron is “aerobic” respiration. One that uses some other molecule is “anaerobic”. The key point of this now-getting-way-too-extended biochemistry lecture is that the distinction is made not just because oxygen respiration is the most common pathway, but because it yields much more energy with much greater efficiency than any other; if you want to be more than one cell big and you want to breed fast, you’d better be able to perform aerobic respiration. The only places where any organism that depends on an anaerobic pathway dominates are places where there is no or very, very little oxygen, for the same basic reason as why horse-drawn buggies aren’t competitive in NASCAR.
Humans, and other animals, can perform anaerobic respiration; you do it any time you exert yourself enough to get short of breath. You develop an oxygen debt, in which you dump your stored fuel and burn it inefficiently until you either run out of storage and are forcibly stopped, or can get the chance to stop and pant for awhile. The issue here, and why I want to throw things at CNN, is that this is inherently brief and unsustainable; we just have too high an inherent demand for energy, especially as mammals, for anaerobic metabolism to sustain us without an oxygen supplement, and even with some aerobic respiration still going it’s not sustainable for very long. They did a decent job of answering why cell death due to the sudden drop in oxygen doesn’t occur (by stopping the destructive reactions that require some level of oxygen to happen in the first place), but not how the suspended-animation state is possible to maintain.
In the linked video, Dr. Gupta goes one teetering step further than the article in explaining, and says Dr. Roth uses “ketones” as the new “fuel”. This is actually MORE confusing, because ketone bodies are themselves a form of stored energy that needs to be biochemically unpacked and turned into something usable in specific tissues- it’s one of those metabolic backup tools the body squirrels away in case it runs completely out of the stored and circulating carbohydrate that is faster and easier to burn. Worse than that, even if very high amounts of ketone were administered in order to make up for the loss of the energy from oxygen, that would be a problem in and of itself- it would throw the pH of the organism’s blood completely out of whack, which is a Large Problem as many enzymes have small ranges of pH in which they’ll work. Acidosis from excess ketones is what actually causes a dangerous “diabetic coma”, not the excess of blood glucose itself.
So the questions of how Dr. Roth is keeping his subjects supplied with enough usable energy to keep their cells going even in that minimal-energy state, how he manages to get their metabolisms to shift gears so drastically in the time needed (which in itself costs energy), and how that suspended animation capacity is even retained as a response in a group of complex organisms that have been obligate oxygen-respirers for a billion years are left a mystery. I suppose I can’t complain too hard as CNN is pitching to an audience that’s mostly scientifically illiterate, but couldn’t they at least leave a few more cookie crumbs for those of us that aren’t?
*Gaining electrons is called “reduction”. And with this pair of counterintuitive terms for a very basic class of reactions, a chemistry student’s long nightmare begins.
**Ever used hydrogen peroxide to break up a bloodstain? That fizzing reaction is the remaining catalase in the blood reacting with the peroxide, which are even more aggressive oxidizers.



