Tag: Chemopreservation

Ken Hayworth on straight freezing in cryonics

Ken Hayworth’s idea of promoting a fixation-based alternative to brain cryopreservation is something I am highly sympathetic to overall, and I hope some progress in this direction results from the work he is doing and trying to induce others to do. That said, I wanted to comment on Hayworth’s remarks about straight freezing of brain tissue.

Figure 1B shows the horrific damage (destroyed cells) that occurs when such a slice is “preserved” using a freezing technique typical of those employed early in cryonics. Such damage is clearly irreversible by any future technology and it should come as no surprise that such techniques were flatly rejected by the scientific and medical community.

While it’s true that straight-frozen tissue as shown looks pretty awful I think it’s too strong a statement to say that “such damage is clearly irreversible by any future technology” unless you have further supporting arguments. To invoke a relevant analogy, we could run a phone book through a garden-variety shredder found in many offices, and still be able to reconstruct it from the resulting debris. The fact that there is debris remaining with the frozen tissue (as opposed to the cases of decay or burning) means we cannot, without further argument, rule out some sort of reconstructive process using future technology, including nanotechnology. It is also worth noting that with imperfect chemical fixation you run a risk of tissue loss over time that does not occur with cryopreservation; even debris resulting from straight freezing will remain as-is so long as cryogenic temperatures are maintained.

I also note that Hayworth says his proposed plastination could only be done properly if you start with a living patient with still-beating heart to distribute the initial fixative.

It is important to understand that the standard fixation and plasticization protocol is started while the animal is still alive. If the animal’s heart is allowed to stop for even a few minutes before the glutaraldehyde is perfused into the vasculature, then the quality of the preservation is markedly reduced. This fact will also be true for any whole brain protocol based on perfusion.

This of course would be problematic for any procedure to be used on humans; you’d have to treat it as some form of euthanasia.

Chemical preservation and cryonics research

In the 2009-4 issue of Alcor’s Cryonics magazine I review the technical and practical feasibility of chemical preservation. One of the most interesting aspects of chemopreservation is that it could play a useful role in the cryopreservation of ischemic patients.

There is accumulating evidence that it is a lot more difficult to prevent ice formation in patients with extensive ischemic injury. This raises the question whether some cryonics patients could benefit from chemical fixation prior to transport and cryoprotective perfusion.

Such protocols raise a number of obvious concerns but the question is not so much whether these procedures are inferior to vitrification of non-ischemic patients, but whether fixatives can improve the situation of some ischemic patients compared to the prospect of substantial ice formation, or even straight freezing (cooling without cryoprotection). This is an empirical question which needs to be settled by experimental research.

Chemopreservation: The Good, The Bad and the Ugly

Brain preservation

Mind uploading advocate Kenneth Hayworth has launched an interesting website devoted to the science of brain preservation. Of particular interest is his Proposal for a Brain Preservation Technology Prize (PDF). This document includes one of the most comprehensive discussions of chemopreservation as a strategy for personal survival. For example, one of the most common objections to chemopreservation is that fixatives like formaldehyde and glutaraldehyde do a poor job of fixing lipids. In this document, Hayworth reviews a number of papers where a fixative that can stabilize lipids, osmium tetroxide, is perfused (!) through the circulatory system.   For human sized brains such a step would be necessary to avoid the ischemic damage and autolysis that would occur in the case of the time-consuming alternative of diffusion fixation.  He also speculates that such a fixed brain can be perfused with a high viscosity plastic resin for long term preservation.

One of the limitations of this approach, as the author concedes, is that the procedure needs to be started before death. In reality, the situation is even more challenging  than that because the procedure would have to be started before ischemia-induced brain perfusion abnormalities associated with terminal disease and the agonal phase will manifest themselves. This is a problem where “old fashioned” cryonics has a clear advantage. Perfusion impairment may interfere with complete distribution and equilibration of the cryoprotectant in the brain but the unperfused tissues will still be stabilized (although in a damaged form) through low temperatures. In the case of chemical fixation such a “second chance” is absent. This is not just a theoretical problem. Cryonics researchers have become painfully aware of the adverse effects of even the slightest perfusion artifacts on the quality of fixation and the resulting electron micrographs.

As a consequence, this kind of “high quality” chemopreservation can only be a credible alternative for cryonics if the medical establishment would permit the procedure for those who are diagnosed as terminally ill. If the acceptance of cryonics is any guidance, there is little chance that this will happen any time soon.

Chemopreservation has another major obstacle to deal with. As the cryobiologist Brain Wowk has stated on numerous occasions, chemical fixation is a dead end in terms of reversibility with contemporary technologies. This aspect of chemical fixation limits the demonstration of its technical feasibility to a demonstration of ultrastructural preservation.  In the case of cryonics, evidence of excellent ultrastructural preservation has produced little excitement among the scientific establishment and the general public. Linking chemopreservation exclusively to mind uploading may present another obstacle to its acceptance.

In his essay Killed by Bad Philosophy: Why brain preservation followed by mind uploading is a cure for death [PDF] Kenneth Hayworth attempts a defense of mind uploading by identifying the philosophical errors that those who reject the concept, and those who argue that “a copy is not you” in particular, engage in. The author shows little doubt about his position although one might object that the central example that is used to make the case could also be used to  argue against mind uploading. One might even object  that the whole debate involves a pseudo-problem if any kind of empirical observation can be made consistent with the case for and the case against mind uploading.

Aside from these complexities, this is an admirable effort to raises interest in high quality brain fixation. Initial funding for more experimental research should be encouraged.