by Ben Best

In cryonics we know that cooling reduces metabolism and that if we can cool enough without freezing or cracking we are able to preserve cells, tissues and organs for thousands of years in a state that looks normal even under an electron microscope. We don't need hydrogen sulfide to induce cooling in cryonics patients, but we do face a severe problem in how to prevent cold ischemic damage when shipping cryonics patients for great distances at water-ice temperature.I have been encouraging Dr. Pichugin to investigate whether hydrogen sulfide could be of benefit.

By reducing the water temperature of a fish it is possible to cut their metabolic rate by half and cause them to live twice as long. But "subjective time" for the fish would not change. Living life in slow motion (at half the speed) for twice as long would not be a real gain in lifespan, despite the doubling of elapsed time. It could matter, however, that half as much oxygen and nutrient is required for a given amount of objective time if availability of these is low.

Hibernating animals are warm-blooded creatures that are able to temporarily reduce their metabolism and temporarily become more cold-blooded. In this state

they can survive a cold winter with little food. Mammals like humans and mice are warm-blooded animals that are not normally capable of hibernation. But the Seattle experiments indicate that a hibernating, "suspended animation-like" state can be induced in mice with hydrogen sulfide. If this can be done in mice, it should be possible in dogs, monkeys and humans.

The mitochondria are the energy-producing parts of the cells of our body tissues. If mitochondria are poisoned by cyanide, cells no longer have the energy they require to survive. Although cells can temporarily produce energy without oxygen (anaerobic metabolism), the resulting acidification eventually becomes destructive. Low levels of oxygen paradoxically result in high levels of damaging reactive molecules. Cell damage is prevented when both energy production and energy requirements can be reduced in conjunction.

In the Seattle experiments reversible inhibition of mitochondrial function with hydrogen sulfide simply reduced metabolism and lowered body temperature without causing damage. How could a reduction in the energy-producing capability of mitochondria prevent excessive anaerobic metabolism and reduce energy utilization? Considering that most of the metabolic energy of the brain is used by the sodium pump in maintaining membrane potential, why wouldn't hydrogen sulfide create an energy crisis? Yet the Seattle researchers stated that "No behavioral or functional differences in the mice were detected after exposure to 80 ppm of H₂S for 6 hours. SCIENCE Could hydrogen sulfide also be reversibly inhibiting the sodium pump?

Typically a person is declared legally dead when their heart stops beating. But at that moment most of the cells of the body tissues are as alive as they were before the heart stopped. In this sense there is little difference between a living person and a "dead" in the moments after the heart has stopped. Therefore, to say that the results of the hydrogen sulfide experiments are not relevant to cryonics because the mice were alive and our patients are "dead" is to miss the entire point of preservation in cryonics. The living cells of a cryonics patient must be preserved in a potentially viable condition. If cells, tissue and organs are preserved by hydrogen sulfide in a living mouse, similar preservation is also potentially possible in a "dead" cryonics patient. Time must pass after the heart stops for the cells, tissues and organs of the body to deteriorate. At room temperature lack of oxygen and nutrient cause most cells (especially brain cells) to acidify and self-destruct within the space of a day. Considerable damage occurs within the first hours. It would be nice if hydrogen sulfide could be used to quickly slow metabolism and reduce damage, but in cryonics the most practical method to slow metabolism is by rapid cooling. But what about after the cryonics patient has been cooled to ice-water temperature? Could metabolism be significantly slowed by hydrogen sulfide when further cooling is not possible? If so, then hydrogen sulfide could be an excellent additive to organ preservation solutions to prevent cold ischemia. If so, we could ship our cryonics patients to Michigan from all over the world at ice water temperature without much tissue damage. Hearts, kidneys and other transplantable organs could similarly be preserved.

Hi Ben,

Your article is good. Unfortunately, the experiments of 24 hour cold storage of rat brains with perfused with various H₂S concentrations did not show positive results. All the H₂S concentrations I used (200, 100, 50, 25, 12, 6 and 2 mg/L) gave survival of rat brain tissues at the level of the control. I would like to write an article about problems of long term cold storage of brain tissues for a next issue of The Immortalist. I will analyze all the experiments I performed on this topic (including the H₂S experiments).

Yuri Pichugin, Ph.D