26. January 2015 · Comments Off · Categories: Health, Neuroscience, Science

After a few articles considering Alzheimer disease from several angles, I would like to switch gears this month and talk more generally about the interaction between the immune system and aging.

In his 2012 paper[1], Caleb E. Finch documents the evolution of life expectancy in the course of human history. The life expectancy at birth of our shared ape ancestor 6 millions years ago is hypothesized to approximate that of a chimpanzee, 15 years. The first Homo species appeared 1-2 million years ago and had a life expectancy of ~20 years, while H. sapiens came onto the scene ~100,000 years ago and could expect about 30 years of life. But starting around 200 years ago, concurrent with industrialization, human life expectancy jumped rapidly, to somewhere between 70 and 80 years today.

As many readers are likely aware, the huge recent increases in life expectancy are commonly attributed to improvements in hygiene, nutrition, and medicine during the nineteenth and twentieth centuries that reduced mortality from infections at all ages. Finch hypothesizes, generally, that early age mortality over the course of human history is primarily due to (acute) infection, while old age mortality is primarily due to (chronic) inflammation. Further analysis of mortality rates over the last several hundred years leads him to further hypothesize that aging has been slowed in proportion to the reduced exposure to infections in early life. These hypotheses are supported by twentieth century examples which strongly demonstrate influences of the early life environment on adult health, such as the effects of prenatal and postnatal developmental influences (e.g., nutrition, exposure to infection) on adult chronic metabolic and vascular disorders as well as physical traits and mental characteristics. This leads Finch to suggest “broadening the concept of ‘developmental origins’ to include three groups of factors: nutritional deficits, chronic stress from socioeconomic factors, and direct and indirect damage from infections.”

Finch also considers the effects of inflammation and diet on human evolution, proposing several environmental and foraging factors that may have been important in the genetic basis for evolving lower basal mortality through interactions with chronic inflammation, in particular: dietary fat and caloric content; infections from pathogens ingested from carrion and from exposure to excreta; and noninfectious inflammagens such as those in aerosols and in cooked foods. He hypothesizes that exposure to these proinflammatory factors, which one would expect to shorten life expectancy, actually resulted in humans evolving lower mortality and longer lifespans in response to highly inflammatory environments.

A means for this, he argues, was the development of the apoE4 genotype. Noting that the apoE4 allele favors advantageous fat accumulation and is also associated with enhanced inflammatory responses, Finch argues that heightened inflammatory response and more efficient fat storage would have been adaptive in a pro-inflammatory environment and during times of uncertain nutrition. As has been discussed in prior articles in Cooler Minds Prevail, the apoE alleles also influence diverse chronic non-infectious degenerative diseases and lifespan. “Thus,” Finch concludes, “the apoE allele system has multiple influences relevant to evolution of brain development, metabolic storage, host defense, and longevity.”

With the general relationship between inflammation and the evolution of human aging and life expectancy in mind, let us now consider immune system involvement in more detail, and the relationship between HIV and immunosenescence more specifically.

Immunosenescence refers to the ageassociated deterioration of the immune system. As an organism ages it gradually becomes deficient in its ability to respond to infections and experiences a decline in long-term immune memory. This is due to a number of specific biological changes such as diminished self-renewal capacity of hematopoietic stem cells, a decline in total number of phagocytes, impairment of Natural Killer (NK) and dendritic cells, and a reduction in B-cell population. There is also a decline in the production of new naïve lymphocytes and the functional competence of memory cell populations. As a result, advanced age is associated with increased frequency and severity of pathological health problems as well as an increase in morbidity due to impaired ability to respond to infections, diseases, and disorders.

It is not hard to imagine that an increased viral load leading to chronic inflammatory response may accelerate aging and immunosenescence. Evidence for this is accumulating rapidly since the advent of antiretroviral therapies for treatment of HIV infection. An unforeseen consequence of these successful therapies is that HIV patients are living longer but a striking number of them appear to be getting older faster, particularly showing early signs of dementia usually seen in the elderly. In one study, slightly more than 10% of older patients (avg = 56.7 years) with wellcontrolled HIV infection had cerebrospinal fluid (CSF) marker profiles consistent with Alzheimer disease[2] – more than 10 times the risk prevalence of the general population at the same age. HIV patients are also registering higher rates of insulin resistance and cholesterol imbalances, suffer elevated rates of melanoma and kidney cancers, and seven times the rate of other non-HIV-related cancers. And ultimately, long-term treated HIV-infected individuals also die at an earlier age than HIV-uninfected individuals[3].

Recent research is beginning to explore and unravel the interplay between HIV infection and other environmental factors (such as co-infection with other viruses) in the acceleration of the aging process of the immune system, leading to immunosenescence. In the setting of HIV infection, the immune response is associated with abnormally high levels of activation, leading to a cascade of continued viral spread and cell death, and accelerating the physiologic steps associated with immunosenescence. Despite clear improvements associated with effective antiretroviral therapy, some subjects show persistent alterations in T cell homeostasis, especially constraints on T cell recovery, which are further exacerbated in the setting of co-infection and increasing age.

Unsurprisingly, it has been observed that markers of immunosenescence might predict morbidity and mortality in HIV-infected adults as well as the general population. In both HIV infection and aging, immunosenescence is marked by an increased proportion of CD28- to CD57+, and memory CD8+ T cells with reduced capacity to produce interleukin 2 (IL-2), increased production of interleukin 6 (IL-6), resistance to apoptosis, and shortened telomeres. Levels of markers of inflammation are elevated in HIV infected patients, and elevations in markers such as high-sensitivity C-reactive protein, D-dimer, and interleukin 6 (IL-6) have been associated with increased risk for cardiovascular disease, opportunistic conditions, or all-cause mortality[4].

But even as we are beginning to identify markers that appear to be associated with risk of poor outcome in HIV infection, it is still unclear how patients should be treated on the basis of this information. To that end, several trials are underway to evaluate the effects of modulation of immune activation and inflammation in HIV infection. At the same time, clinicians at the forefront of advancing knowledge and clinical care are performing research aimed at optimizing care for aging HIV patients.

The implications for such research may be far-reaching. In fact, many HIV clinicians and researchers think that HIV may be key to understanding aging in general. Dr. Eric Verdin states, “I think in treated, HIV-infected patients the primary driver of disease is immunological. The study of individuals who are HIV-positive is likely to teach us things that are really new and important, not only about HIV infection, but also about normal aging.”

Dr. Steven Deeks stresses the collaborative efforts of experts across fields. “I think there is a high potential for tremendous progress in understanding HIV if we can assemble a team of experts from the world of HIV immunology and the world of gerontology,” he says. “Each field can dramatically inform the other. I believe HIV is a well described, well studied, distinct disease that can be used as
a model by the larger community to look at issues of aging.”

References

[1] Finch, C (2012). Evolution of the Human Lifespan, Past, Present, and Future: Phases in the Evolution of Human Life Expectancy in Relation to the Inflammatory Load. Proceedings of the American Philosophical Society, 156:1, 9-44.

[2] Mascolini, M (2013). Over 10% in Older HIV Group Fit Alzheimer’s Biomarker Risk Profile. Conference Reports for NATAP: 20th Conference on Retroviruses and Opportunistic Infections, March 3-6, 2013.

[3] Aberg, X (2012). Aging, Inflammation, and HIV Infection. Topics in Antiviral Medicine, 20:3, 101-105.

[4] Deeks, S, Verdin, S. and McCune, JM (2012). Immunosenescence and HIV. Current Opinion in Immunology, 24: 1-6.

Originally published as an article (in the Cooler Minds Prevail series) in Cryonics magazine, June, 2013

23. January 2015 · Comments Off · Categories: Neuroscience, Science

Last month this column considered current and future progress in Alzheimer Disease (AD) diagnosis, management, and treatment. Because AD is a terrible brain disease with an increasing rate of prevalence with age, and because it represents one of – if not the – worst conditions that can afflict a person with cryopreservation arrangements, I would like to continue our consideration of this well-known and widely-feared neurodegenerative disease. Specifically, our focus will be on apolipoprotein E (apoE) and research regarding its role in the modulation of physiological responses to certain viral infections.

ApoE protein is primarily synthesized peripherally in the liver and mediates cholesterol metabolism systemically, but it is also made in the central nervous system by astroglia and microglia (non-neuronal cell types) where it transports cholesterol to neurons. In the CNS, neurons express receptors for apoE that are part of the low density lipoprotein receptor gene family. Historically, apoE has been recognized for its role in lipoprotein metabolism and its importance in cardiovascular disease. Of course, apoE carrier status is also widely known as the major factor determining one’s risk of developing late-onset Alzheimer disease (AD). But more recent research has indicated that the various isoforms of apoE may also have significant immunological impact by conferring different susceptibilities to other diseases, as well.

The human apoE gene is located on chromosome 19 and is composed of 79 individual single nucleotide polymorphisms (SNPs). The three major alleles of apoE, named Epsilon-2 (Ɛ2), Epsilon-3 (Ɛ3), and Epsilon-4 (Ɛ4), are determined by differences in SNPs s429358 and rs7412. The products of these alleles are the protein isoforms apoE2, apoE3, and apoE4, which differ only by a single amino acid at two residues (amino acid 112 and amino acid 158). These amino acid substitutions affect noncovalent “salt bridge” formation within the proteins, which ultimately impacts on lipoprotein preference, stability of the protein, and receptor binding activities of the isoforms (see Table 1).

Isoform Amino acid 112 Amino acid 158 Relative charge Lipoprotein preference LDL receptor binding ability

apoE2

cysteine

cysteine

0

HDL

low

apoE3

cysteine

arginine

+1

HDL

high

apoE4

arginine

arginine

+2

VLDL, chylomicrons

high

Table 1. ApoE isoform amino acid differences and resulting chemical and physiological changes.

There are also two minor alleles, Epsilon-1 (Ɛ1) and Epsilon-5 (Ɛ5), which are present in less than 0.1% of the population. The three major alleles are responsible for three homozygous (Ɛ2/Ɛ2, Ɛ3/Ɛ3, Ɛ4/Ɛ4) and three heterozygous (Ɛ2/Ɛ3, Ɛ2/Ɛ4, Ɛ3/Ɛ4) genotypes. [I will pause to mention here that it is now quite easy to determine one’s genotype through services such as 23andme.com.]

An interesting document in the field is the literature review by Inga Kuhlman, et al. (Lipids in Health and Disease 2010, 9:8) which assesses hepatitis C, HIV and herpes simplex disease risk by ApoE genotype. An important finding is that the Ɛ4 allele is found less frequently in populations as they age (e.g., 14% of the general German population vs. 5% in centenarians), indicating that Ɛ4 is a major mortality factor in the elderly. This is assumed to be a result of the Ɛ4 allele’s well-known predisposition to Alzheimer and cardiovascular diseases.

The authors explain that “apoE4 carriers have a tendency for 5-10% higher fasting total cholesterol, LDL-cholesterol and triglyceride levels relative to homozygote Ɛ3/Ɛ3” and that this tendency towards higher lipid levels is probably responsible for the 40-50% greater cardiovascular disease risk in Ɛ4 carriers. They also point out that “although the molecular basis of the pathology is poorly understood, and likely to be in part due to apoE genotype associated differences in brain lipid metabolism, an apoE4 genotype has been highly consistently associated with the risk of an age-related loss of cognitive function, in an allele dose fashion.” This means, of course, that Ɛ4/Ɛ4 carriers are at greatest risk for cognitive dysfunction with increasing age.

In the field of immune regulation, a growing number of studies point to apoE’s interaction with many immunological processes. In their article, Kuhlman, et al., summarize the impact of the Ɛ4 allele on the susceptibility to specific infectious viral disease. The authors review a number of studies of the effects of apoE4 genotype on hepatitis C (HCV), human immunodeficiency virus (HIV), and herpes simplex (HSV) infection and outcome in humans.

In general, apoE4 was found to be protective against hepatitis C infection vs. (Ɛ3/Ɛ3) controls. Though the exact mechanisms of apoE genotype-specific effects on HCV life cycle remain uncertain, apoE seems to be involved because “available data indicate that the outcome of chronic HCV infection is better among Ɛ4 carriers due to slower fibrosis progression.”

Concerning the possible influence of apoE genotype on HIV infection and HIV-associated dementia, the authors call attention to the fact that “cholesterol is a crucial component of the HIV envelope and essential for viral entry and assembly.” Given that apoE is essential for cholesterol transport, they hypothesize that apoE genotype influences HIV-induced effects on neurological function. Subsequent review of available research suggests that the 4 allele is associated with higher steady-state viral load and faster disease progression due to accelerated virus entry in 4 carriers, but a correlation between apoE4 and HIV-associated dementia “remains controversial and needs to be clarified by further studies.”

Lastly, a review of the literature regarding the effects of apoE4 genotype on herpes simplex virus (HSV)-1 infection and outcome in humans indicates that apoE4 enhances the susceptibility for HSV-1 “as well as the neuroinvasiveness of HSV-1 compared to other apoE variants” (i.e., HSV-1 is found in more frequently in the CNS of 4 carriers). Importantly, the authors also note that “the combination of apoE4 and HSV-1 may lead to a higher risk of Alzheimer disease (AD) than either factor in isolation.”

Due to its generally being associated with higher risk of cardiovascular disease, dementia, and increased susceptibility to and/or accelerated progression of various viral infections, one may wonder why the 4 allele has not been eliminated by evolutionary selection. This may be explained, in part, by the protective and beneficial effects it exhibits in certain harmful infectious diseases, as demonstrated for hepatitis C.

The exact mechanisms of apoE influence on susceptibility to and course of viral infection remain shrouded. Because the mechanisms of HCV, HIV, and HSV infection are quite similar (i.e., all three viruses compete with apoE for cell attachment and receptor binding), it is interesting to find differences in receptor binding among them.

Involvement or interaction between the immune system, cognition, and brain diseases such as AD is an as-yet widely untouched field of inquiry. Further elucidation of the mechanisms by which apoE may influence the pathogenesis of infectious viral diseases can lead to new developments in the treatment of disease based on an individual’s apoE genotype.

Aside from the role that ApoE plays in susceptibility and progression of infectious disease, there is growing interest in the role that infection or a compromised immune system plays in the development of dementia. For example, despite the successful management of HIV with antiretroviral drugs, some patients are showing signs of memory impairment and dementia at a relatively young age. Interestingly, these people seem to show accelerated aging, too, which raises important questions about the relationship between the immune system, immunosenescence, and aging.

Originally published as an article (in the Cooler Minds Prevail series) in Cryonics magazine, May, 2013

20. January 2015 · Comments Off · Categories: Cryonics, Society

This article was previously published in Cryonics Magazine, May, 2013

In this short article I will discuss two distinct developments in contemporary cryonics that are setting the stage of how cryonics is going to be practiced in the foreseeable future.

First, there is the recognition that the most formidable obstacle for people to make cryonics arrangements is not scientific or technological, but psychological. We know this because people tell us so. It is a form of anxiety about the future and social alienation that is even a concern for people who have made cryonics arrangements. Ignoring this and/or telling people to “toughen up” is simply not an effective response.

Second, there is an increasing interest in long-term wealth preservation among people who have made cryonics arrangements and this interest is no longer confined to wealthy Alcor members. In addition, there is also a growing interest in preserving biographical information, ranging from personal memories to tangible objects. This development can reflect a desire to prevent “disintegration” (see Keegan Macintosh’s excellent article in this magazine) during cryostasis or may be motivated by the use of such information for damage repair or validation of resuscitation attempts.

It seems clear to me that these two developments are closely associated and that Alcor can address the desire of their members to preserve biographical information, remain “connected” and make cryonics a less anxiety-inducing choice at the same time.

In the April 2013 issue of Cryonics magazine Mike Anzis contributed a useful review of very long-term storage alternatives for personal information and materials and all these options have their pro’s and con’s. I suspect that many people not only have reservations about the long-term survival of many of the organizations and companies reviewed, but also have concerns about privacy and the alignment of the goals of these entities and the objective of personal survival.

While it is unrealistic to expect that Alcor can be involved in all matters concerning personal data storage and reintegration (there is an argument for diversification and redundancy, too) it seems rather obvious that Alcor has a more substantial role to play than it does today. It needs to play a substantial role if we want Alcor to be perceived as an organization that does not just see reversible cryopreservation and rejuvenation as a technical problem to be solved, but one that will also do its best to give its patients a face, maintain the social integration of its patients, and facilitate means to protect personal assets and personal information.

I cannot do justice to the practical aspects of this objective in this short article but let me conclude with a number of specific suggestions.

We do not know whether email in its current format will still exist in the future but we do know that Alcor owns a domain name and can issue email addresses to their cryopreservation members and provide secure storage of email messages.

We do not need to speculate as much about the nature and compatibility of very long-term data storage technologies if Alcor starts offering such services and will ensure to upgrade them as times change. In addition, Alcor can allow its members to securely edit their personal information and medical records to allow for a better response in time of need.

Alcor can hardly compete with social networking platforms such as Facebook and Google+ but we can make an effort to offer individual members the opportunity to create a private or public online profile that will be retained after cryopreservation of the member, and that can perhaps even be updated by Alcor, family, and friends.

The benefits of such changes are greater than just offering Alcor members more opportunities to retain personal information, prevent disintegration, and more strongly identify with their cryonics organization. By giving our members a visible place and the tools to remain relevant we will also communicate to the rest of the world that we are serious and that we will not let our members slide into oblivion – even during cryostasis.

20. January 2015 · Comments Off · Categories: Cryonics, Death, Society

“…it is not the strongest that survives; but the species that survives is the one that is able best to adapt and adjust to the changing environment in which it finds itself” so reads a quote that, in modified form, often has been mistakenly attributed to Charles Darwin but was in fact a description of Darwin’s views penned down by a Professor of Management and Marketing named Leon C. Megginson in 1963. But, surely, one reason for the popularity of this quote is that it captures the modern view of evolution quite well. In this column I would like to briefly reflect on what cryonics means in the context of evolution and natural selection.

Any cryonicist that has not kept his support of cryonics completely to himself must have found himself in a situation where even the most reasonable arguments seemed to leave someone else completely indifferent, or even hostile. Even in the case of family members or friends there comes a point where one cannot help thinking, “well, if you would rather die than think, fine, I am not going to stop you.” It appears, then, that people who make cryonics arrangements are part of an extremely small group of people that will escape the common fate of all humans (i.e. death), as a consequence of being extremely open-minded and adaptable.  But is this the “survival” that the theory of natural selection speaks of?

The modern theory of natural selection is essentially about reproduction. It is not necessarily the longest-lived species (the survivors) whose (genetic) traits will become more common in a population but the ones whose fitness leads to greater reproductive success. It can hardly be denied that cryonicists are extraordinarily capable of adapting to change (or ready to adapt to future change) but it has also been quite firmly observed that cryonicists (or life extentionists in general) are lagging the general population in terms of reproduction, either because of the higher number of single persons or because of the lower interest in having children. It is sometimes observed that whereas most people seek “immortality” by ensuring their genes will survive in future generations, cryonicists see immortality by seeking to survive themselves. In addition, even allowing for a growing interest in cryonics, the number of people making cryonics arrangements is simply too small to have a meaningful effect on the genetic and mental traits of future generations. At best, cryonicists may find themselves being perceived as independent, courageous, individuals that were simply more capable of anticipating the future of science and medicine.

It is tempting, indeed, to think of cryonicists as a homogeneous group of people who are extraordinarily analytic and adaptable but a closer inspection of the motives of people who make cryonics arrangements suggests something different. Indeed, if we look at the early days of cryonics, we see a disproportionate number of cryonicists who where extraordinary visionaries, sometimes independently arriving at the same conclusions (think of Robert Ettinger and Ev Cooper). As cryonics received more mainstream exposure, however, we see different reasons why people endorse cryonics. A partner has cryonics arrangements and the other person is persuaded to do so, too. Subcultures in which making cryonics arrangements is strongly endorsed (like transhumanism). A strong fear of death that prompts a person to do anything to not die, regardless of a dispassionate assessment of cryonics. In more recent times, even career considerations can be a factor as more “market-based” salaries are available in the field of cryonics. Still, despite the possibility that the personality type that chooses cryonics is increasingly getting more diverse, it still makes sense to talk about the demographics of cryonics for as long as the cryonics population is substantially different from the general population.

Where does all this leave us concerning cryonics and natural selection? Since natural selection is basically about reproductive success despite death it would not be correct to characterize the small group of cryonicists that will survive (where others do not) as an example of Darwinian evolution in action, I think. It may be tempting to use Darwinian terminology to characterize our situation but upon closer scrutiny there are problems with this. What might be said, though, is that (successful) cryonicists will be in the extraordinary situation to live for such a long time that they can see human evolution further unfold and even be in a position to consciously direct it through human enhancement.

This is a web-exclusive edition of the Quod incepimus conficiemus column that is published in Cryonics magazine but was omitted from the December 2014 issue.  

29. November 2014 · Comments Off · Categories: Health, Science

This article was originally published in Cryonics Magazine, 2011 Issue #1

I am an ardent supporter of Dr. Aubrey de Grey and his work to advance rejuvenation science. The man is priceless and unique in his concepts, brilliance, dedication, organizational abilities, and networking skill. His impact on anti-aging science has been powerful. I have attended all four of the conferences he has organized at Cambridge University in England. For the February 2006 issue of LIFE EXTENSION magazine I interviewed Dr. de Grey, and for the December 2007 issue of LIFE EXTENSION I wrote a review of ENDING AGING, the book he co-authored with Michael Rae.

Dr. de Grey asserts that aging is the result of seven kinds of damage – and that technologies that repair all seven types of damage will result in rejuvenation. His seven-fold program for damage repair is called SENS: “Strategies for Engineered Negligible Senescence”. Dr. de Grey asserts that repairing aging damage is a more effective approach than attempting to slow or prevent aging, and I agree with him. Being an ardent supporter of SENS has not stopped me from simultaneously being a critic of aspects of his program that I think are flawed or deficient. I will attempt to outline some of my criticisms in simple language, assuming that my readers have some knowledge of basic science.

Two SENS strategies cannot justly be described as damage-repair, in my opinion. To protect mitochondrial DNA from free radical damage he wants to make copies of mitochondrial DNA in the nucleus – and import the resulting proteins back into the mitochondria. I would call this an attempt to slow or prevent aging – it cannot be called repair.

Similarly, SENS aims to eliminate cancer by deletion of genes that contribute to cancer, specifically telomerase and ALT (Alternate Lengthening of Telomeres) genes. I am not convinced that this is the best way to eliminate cancer, and I do not believe that deleting cancer-producing genes can properly be called damage-repair.

My criticisms about a procrustean attempt to force two strategies into a model purporting to only be concerned with damage and repair is minor, however, compared to a more fundamental concern that I have that a significant form of aging damage may be being ignored by SENS. I have written a review expressing my concern entitled “Nuclear DNA Damage as a Direct Cause of Aging” that was published in the June 2009 issue of the peer-reviewed journal Rejuvenation Research, [note 1] a journal of which Dr. de Grey is Editor-in-Chief. A PDF of my review is available in the life extension section of my website BENBEST.COM. Those interested in all the citations for claims I will make in this essay are encouraged to read my review. In this essay, I limit my citations to only a few critical articles.

There are many types of DNA damage, but for the purposes of this essay I will focus on breakage of both DNA strands – resulting in a gap in a chromosome. There are two mechanisms for repairing double-strand DNA breaks: Homologous Recombination (HR) and Non-Homologous End-Joining (NHEJ). HR usually results in perfect repair, but HR can only operate when cells are dividing. NHEJ is the more frequent form of double-strand break repair, but it is error-prone. NHEJ is the only DNA repair mechanism available for non-dividing cells. Even in cells that divide, 75% of double-strand breaks are repaired by NHEJ. [note 2]

It is hard to believe that it could be a coincidence that the most notorious “accelerated aging” diseases are due to defective DNA repair. The two most prominent of these diseases are Werner’s syndrome (“adult progeria”) and Hutchinson-Gilford syndrome (“childhood progeria”), both of which are caused by defective nuclear DNA repair, mainly HR. In both diseases the “aging phenotype” is apparently due to high levels of apoptosis and cellular senescence. Apoptosis (“cell suicide”) and cellular senescence (cessation of cell division) are both mechanisms that are induced in cells experiencing nuclear DNA damage that the cell is unable to repair. It is not surprising that victims suffering massive depletion of properly functioning cells should exhibit “accelerated aging”. Mice that are genetically altered to show increased apoptosis and cellular senescence also show an “accelerated aging phenotype”.

Elimination of senescent cells and stem-cell replenishment of cells depleted in tissues by this elimination – as well as depleted by apoptosis – are part of SENS. But these strategies are only applicable to cells that divide – not to non-dividing cells such as neurons. Cryonicists are acutely aware that organs – and even whole bodies – can be replaced, but brains (neurons, axons, dendrites, and synapses, particularly) must be preserved if we are not to lose memory and personal identity. The ability of future medicine to replace all organs and tissues other than the brain would render most of SENS unnecessary – except for the brain.

There is considerable evidence of a significant role for DNA damage in brain aging. There are nearly twice as many double-stand nuclear DNA breaks in the cerebral cortex of adult (180 days) rats as in young rats (4 days) – and old (over 780 days) rats have more than twice the double-strand breaks as adult rats. [note 3] Adult rats show a 28% decrease in NHEJ activity in the cerebral cortex neurons compared to neonatal rats – and old rats show a 40% decrease. [note 4] Declining NHEJ activity with age is at least partially due to ATP decline and cellular damage that SENS is intended to fix. But even if NHEJ activity did not decline with age, nuclear DNA damage in neurons will increase at least in part because NHEJ is so error-prone.

Nuclear DNA damage typically leads to mutation or DNA repair – or apoptosis or cellular senescence when DNA repair fails (a mechanism that is believed to have evolved for protection against cancer). But not all DNA damage is repaired, and NHEJ repair is often defective. Accumulating DNA damage and mutation can lead to increasingly dysfunctional cells.

Cancer is due to nuclear DNA damage, mutations, and epimutations. Dr. de Grey has written that “only cancer matters” for mutation and epimutation to nuclear DNA. His mutation terminology does not even acknowledge DNA damage. He has assumed that damaged DNA either is or becomes a mutation. He has assumed that DNA damage that does not become a mutation is either repaired – or leads to apoptosis or cellular senescence.

Dr. de Grey has made the claim that evolution has required such strong defenses against cancer that residual mutation (and, implicitly, DNA damage) is negligible. But cancer incidence increases exponentially with age up to age 80, so it is likely that the residual increases exponentially at the same time.

As recently as the 1980s it was widely believed that normal aging is associated with extensive neuron loss. Now it is established that functional decline in the aging brain is associated with increased neural dysfunction rather than neurodegeneration. [note 5] This neural dysfunction may or may not be mostly due to cellular damage that SENS is intended to fix – including causes of declining NHEJ activity. How much neuron dysfunction associated with aging is due to accumulating mutations or unrepairable nuclear DNA damage is unknown. SENS assumes without proof that nuclear DNA damage and mutation is negligible as a cause of aging (apart from cancer, apoptosis, and cellular senescence). This may be right or it may be wrong. I believe that without definitive proof, nothing should be assumed, and active investigation to determine the facts should not be neglected.

I believe the situation is not hopeless if nuclear DNA damage proves to be a significant cause of brain aging. Future molecular technologies for detection and repair of nuclear DNA damage could be significantly better than natural DNA repair enzymes. And, to simplify the required effort, the DNA repair technologies could be restricted to genes that are actively transcribed in neurons, rather than needing to repair the whole genome.

Notes

1: Best BP. Nuclear DNA damage as a direct cause of aging. Rejuvenation Res. 2009 Jun;12(3):199-208.

2: Mao Z, Bozzella M, Seluanov A, Gorbunova V. Comparison of nonhomologous end joining and homologous recombination in human cells. DNA Repair (Amst). 2008 Oct 1;7(10):1765-71.

3: Mandaville BS, Rao KS. Neurons in the cerebral cortex are most susceptible to DNA-damage in aging rat brain. Biochem Mol Biol Int 1996 Oct; 40(3):507-14.

4: Vyjayanti VN, Rao KS. DNA double strand break repair in brain: reduced NHEJ activity in aging rat neurons. Neurosci Lett. 2006 Jan 23;393(1):18-22.

5: Morrison JH, Hof PR. Life and death of neurons in the aging brain. Science. 1997 Oct 17;278(5337):412-9.

14. November 2014 · Comments Off · Categories: Health, Neuroscience

Any terminal illness is a terrible thing; but to a cryonics member, a brain-destroying neurodegenerative disease is the worst contemporary medical “death sentence” one can receive. There are several flavors of neurodegenerative disorders, many of which primarily affect the patient’s movement, strength, coordination, or the peripheral nervous system. And there are numerous contributory mechanisms in the causation of neurodegeneration, including prion infection and toxin related disease. But the most common – and the most feared – neurodegenerative disease is one that affects not movement, but cognition.

Of course, I am speaking of Alzheimer disease (AD). Originally described in a 51- year old woman by the Bavarian psychiatrist Alois Alzheimer in 1906, neuropathologists have increasingly recognized that AD is also the most common basis for latelife cognitive failure. Culminating in neuronal dystrophy and death leading to the progressive loss of memory and other cognitive functions (i.e., dementia), and affecting individuals of both sexes and of all races and ethnic groups at a rate of occurrence in the U.S. ranging from approximately 1.3% (age 65-74) to 45% (age 85-93), it is easy to see why AD has generated so much intense scientific interest in recent years.

In the recently published work “The Biology of Alzheimer Disease” (2012), most of what is known about AD today is described in detail in the various chapters covering topics such as the neuropsychological profile and neuropathological alterations in AD, biomarkers of AD, the biochemistry and cell biology of the various proteins involved in AD, animal models of AD, the role of inflammation in AD, the genetics of AD, and treatment strategies. The editors’ selection of contributions has resulted in the most up-to-date compendium on Alzheimer disease to date.

The book culminates in a chapter called Alzheimer Disease in 2020, where the editors extol “the remarkable advances in unraveling the biological underpinnings of Alzheimer disease…during the last 25 years,” and yet also recognize that “we have made only the smallest of dents in the development of truly disease-modifying treatments.” So what can we reasonably expect over the course of the next 7 years or so? Will we bang our heads against the wall of discovery, or will there be enormous breakthroughs in identification and treatment of AD?

Though a definitive diagnosis of AD is only possible upon postmortem histopathological examination of the brain, a thorough review of the book leads me to believe that the greatest progress currently being made is in developing assays to diagnose AD at earlier stages. It is now known that neuropathological changes associated with AD may begin decades before symptoms manifest. This, coupled with the uncertainty inherent in a clinical diagnosis of AD, has driven a search for diagnostic markers. Two particular approaches have shown the most promise: brain imaging and the identification of fluid biomarkers of AD.

Historically, imaging was used only to exclude potentially surgically treatable causes of cognitive decline. Over the last few decades, imaging has moved from this minor role to a central position of diagnostic value with ever-increasing specificity. The ability to differentiate AD from alternative or contributory pathologies is of significant value now, but the need for an earlier and more certain diagnosis will only increase as disease-modifying therapies are identified. This will be particularly true if these therapies work best (or only) when initiated at the preclinical stage. Improvements in imaging have also greatly increased our understanding of the biology and progression of AD temporally and spatially. Importantly, the clinical correlations of these changes and their relationships to other biomarkers and to prognosis can be studied.

The primary modalities that have contributed to progress in AD imaging are structural magnetic resonance imaging (MRI), functional MRI, fluorodeoxyglucose (FDG) positron emission tomography (PET), and amyloid PET. Structural MRI, which is used to image the structure of the brain, has obvious utility in visualizing the progressive cerebral atrophy characteristic of AD. Such images can be used as a marker of disease progression and as a means of measuring effective treatments (which would slow the rate of atrophy). Functional MRI, on the other hand, measures changes in blood oxygen leveldependent (BOLD) MR signal. This signal, which can be acquired during cognitive tasks, may provide the clinician with a tool to compare brain activity across conditions in order to assess and detect early brain dysfunction related to AD and to monitor therapeutic response over relatively short time periods.

FDG PET primarily indicates brain metabolism and synaptic activity by measuring glucose analog fluorodeoxyglucose (which can be detected by PET after labeling it with Fluorine-18). A large body of FDG-PET work has identified an endophenotype of AD – that is, a signature set of regions that are typically hypometabolic in AD patients. FDG hypometabolism parallels cognitive function along the trajectory of normal, preclinical, prodromal, and established AD. Over the course of three decades of investigation, FDG PET has emerged as a robust marker of brain dysfunction in AD. Imaging of β-amyloid (Aβ) – the peptide that makes up the plaques found in the brains of AD patients – is accomplished via amyloid PET to determine brain Aβ content. Historically, this has only been possible upon postmortem examination, so the utility of amyloid imaging is in moving this assessment from the pathology laboratory to the clinic. Because amyloid deposition begins early on, however, amyloid PET is not useful as a marker of disease progression.

The well-known hallmarks of AD, the plaques and neurofibrillary tangles first described by Alouis Alzheimer in 1906, were discovered in 1985 to be composed primarily of β-amyloid and hyperphosphorylated tau protein, respectively. Advances in our knowledge of Aβ generation and tau protein homeostasis have led to substantial research into disease-modifying drugs aimed at decreasing overall plaque and tangle load in an effort to halt neurodegeneration. Such treatments will likely be most effective if started early in the disease process, making sensitive and accurate fluid biomarkers of Aβ and tau especially important.

Outside of imaging, progress in AD diagnostics stems primarily from the assessment of fluid biomarkers of AD. These biomarkers are generally procured from the cerebrospinal fluid (CSF) and blood plasma and include total tau (T-tau), phosphorylated tau (P-tau) and the 42 amino acid form of of β-amyloid (Aβ42). These core biomarkers reflect AD pathology and have high diagnostic accuracy, which is especially useful in diagnosing AD in prodromal and mild cognitive impairment cases.

Because the CSF is in direct contact with the extracellular space of the brain, biochemical changes in the brain can be detected in the CSF. Assays to detect Aβ42 led to the discovery that Aβ42 in AD is decreased to approximately 50% of control levels, making the measurement of Aβ42 a useful clinical tool. Measurements of T-tau (around 300% of control in AD patients) and P-tau biomarkers (a marked increase in AD patients) in combination with Aβ42, however, provide an even more powerful diagnostic assay.

Fluid biomarkers for AD other than Aβ and tau have been posited, but positive results have been difficult to replicate. Novel biomarkers with the most promise inlcude the amyloid precursor proteins sAPPβ and sAPPα, β-site APP cleaving enzyme-1 (BACE1), Aβ oligomers, and other Aβ isoforms. Additionally, neuronal and synaptic proteins as well as various inflammatory molecules and markers of oxidative stress may prove valuable as CSF biomarkers. Studies of plasma biomarkers such as those investigating plasma Aβ have yielded contradictory results, but promising novel blood biomarkers for AD may be found in certain signaling and inflammatory proteins.

Taken together, progress in brain imaging and identification of fluid biomarkers hold great promise in improved diagnosis of AD cases. When combined with expected drug therapies we may be able to delay the onset of neurodegeneration and associated cognitive impairment significantly. In the meantime, early diagnosis is helpful in stratifying AD cases, monitoring potential treatments for safety, and monitoring the biochemical effect of drugs. For cryonicists, early diagnosis can help guide treatment and end-of-life care decisions in order to optimize cryopreservation of the brain.

So – back to the original question. What can we predict about the AD landscape in 2020?

Besides continued progress in early diagnosis through brain imaging and fluid biomarkers, the authors anticipate that advances in whole-genome and exome sequencing will lead to a better understanding of all of the genes that contribute to overall genetic risk of AD. Additionally, improved ability to sense and detect the proteins that aggregate in AD and to distinguish these different assembly forms and to correlate the various conformations with cellular, synaptic, and brain network dysfunction should be forthcoming in the next few years. Lastly, we will continue to improve our understanding of the cell biology of neurodegeneration as well as cell-cell interactions and inflammation, providing new insights into what is important and what is not in AD pathogenesis and how it differs across individuals, which will lead, in turn, to improved clinical trials and treatment strategies.

Originally published as an article (in the Cooler Minds Prevail series) in Cryonics magazine, April, 2013

10. November 2014 · Comments Off · Categories: Cryonics, Neuroscience, Science

Cryonics seeks to preserve terminally ill humans in anticipation of future medical advances that may restore these patients to youthful vigor, cure their devastating diseases, and resuscitate them from cryopreservation itself. At the core of this mission lies the goal of preserving that which we know to be most important to continuity of the person him/herself: the brain.

Absent reversible cryopreservation of the brain (i.e., maintenance of viability), a cryonicist’s best hope for eventual resuscitation lies in preserving brain ultrastructure with as much fidelity as possible. Improvements in cryopreservation solutions, methodologies, and protocols from the field to the operating room have greatly enhanced our ability to meet this objective, as evidenced by microscopic evaluations of tissues vitrified in the lab. More recently, CT scans of patients after neuropreservation have provided valuable feedback as to the efficacy of cryoprotective perfusion in actual Alcor cases. Such progress bodes well for good patient outcomes.

But even our greatest attempts at optimal preservation are thwarted by issues such as long ischemic periods resulting in significant perfusion impairment or even the inability to perfuse at all. So how do we evaluate these patients in light of our objective?

Perhaps the best place to start is the extreme. Let us consider, for example, a prehistoric human brain discovered in 2008 at a construction site in York, UK. A paper published in 2011 in the Journal of Archaeological Science (“Exceptional preservation of a prehistoric human brain from Heslington, Yorkshire, UK”) provides gross and histological observations as well as preliminary results of chemical assays in order to determine the extent and cause of preservation of the brain. Low-powered reflected light microscopy and electron microscopy were performed to explore the surviving morphology and histology of the brain, while highly sensitive neuroimmunological techniques and proteomic analyses were employed to explore brain chemistry.

Examination of the skull indicated death by an abrupt trauma to the neck followed by deliberate dismemberment of the head between veretebrae C2 and C3. Significantly, the authors report “no trace of microbial activity, bacterial or fungal, with none of the porosity or ‘tunneling’ that is characteristic of putrefactive microorganisms.” Examination of the brain masses revealed recognizable sulci and gyri, but neither macroscopic nor CT evaluation could differentiate between grey and white matter.

Histological examination of the brain masses showed “a homogenous, amorphous substance that had not retained any cellular or matrix structure.” Transmission electronic microscopy (TEM) also did not detect any surviving cellular structure, although it did reveal what appeared to be “numerous morphologically degraded structures characteristic of the myelin sheath of nerve fibres.”

Preliminary biomolecular analysis found only 5% of the brain was detectable as hydrolysable amino acids, in contrast to fresh brain tissue of which proteins represent more than 1/3 of dry weight. When compared with a fresh brain, the Heslington brain was also depleted in polar amino acids and enriched in hydrophobic amino acids. Very little undegraded solventsoluble brain lipid was preserved (0.8%- 1.1% wet weight compared with 17.1% for rat brain). In addition, there was an almost complete absence of phospholipids and only a trace of cholesterol, while degradation products of a wide range of lipids were found in abundance.

Ultimately, the authors determined that the preservation of this brain was due to decapitation (thus eliminating the movement of putrefying bacteria from the gut to the brain) followed by inhibition of postmortem putrefaction achieved through rapid burial into fine-grained wet sediment. They go on to argue that this type of preservation is not as unusual as one might think, citing several similar examples of preserved prehistoric human brains, almost always found in wet burial environments.

While interesting in its own right, few would argue that the Heslington brain represents a state of preservation amenable to resuscitation. The ability to infer anything beyond gross macro structure has been obliterated and the normal chemical constituents of the brain have dissolved almost completely into the surrounding environment. Clearly, much of the look of a brain can be retained while none of the person’s identity remains (or is recoverable).

Let us then look at a situation that hits a little closer to home. Published in Forensic Science International in 2007, an article entitled “Autopsy at 2 months after death: Brain is satisfactorily preserved for neuropathology” provides us with considerable food for thought. In this example, a 77-year-old woman’s whole body was stored postmortem in a 3°C cooling chamber for 2 months prior to chemical fixation of her brain at autopsy.

The authors describe moderate autolysis of internal organs of the body, indicating the start of decomposition and putrefaction, as well as reduced tissue consistency and superficial areas of disintegration of the brain. Overall gross morphology was sufficiently preserved to allow macroscopic examination and application of neuropathological methods for diagnosis of neurological disorders. Importantly, they also report that “histologically, normal brain structures including all major parenchymal cell types (neurons, astrocytes, oligodendrocytes, microglia), neuropil, axons, and myelin sheaths were preserved.”

In this case, the use of cold temperatures (3°C) drastically slowed, but did not stop, deterioration of the brain. However, enough of the brain’s chemical constituents and physical structure remained to provide the basis for possible future resuscitation. And while this woman’s brain was preserved by chemical diffusion over the course of 9 weeks (allowing for continued degradation of subcortical tissues during the course of fixation), the use of cryogenic temperatures to quickly preserve her brain would also have been possible, as has been the situation for many “straight frozen” Alcor patients who were received in similar condition.

Exactly where the line between recoverability and non-recoverability — resulting in information-theoretic death — exists is yet to be determined. And while we push, rightfully, for ever greater preservation methods, we do well to remember that those preserved under lessthan- optimal conditions are by no means lost causes. Preserved information, even in fractured and distorted form, may well be adequate to infer the original state.

Originally published as an article (in the Cooler Minds Prevail series) in Cryonics magazine, March, 2013

20. October 2014 · Comments Off · Categories: Neuroscience, Science

Cryonics Magazine, February 2013

This is the first entry in a new series of short articles about neuroscience and its implications for the field of human cryopreservation and life extension. In this article I discuss the relationship of the brain to consciousness and knowledge acquisition before venturing into more specific and practical topics

What is consciousness? Most of us understand the word in context, but when asked to define it we are suddenly at a loss for words or at best we offer a description that seems wholly inadequate. Scientists, philosophers, and religious scholars have debated the source, meaning, and nature of consciousness for all of recorded history. But with the rise of neuroscience over the past few decades, it now seems as though explaining the nature and mechanisms of conscious experience in neurobiological terms may be an attainable goal.

The recent work on consciousness by neuroscientists has left certain philosophers more frustrated than ever before, including the likes of Thomas Nagel and David Chalmers. They suspect that consciousness may be quite different and separate from the brain circuitry proposed to underlie it.

Consciousness has appeared to be a strange and undefinable phenomenon for a very long time. Daniel Dennett captured the feeling very nicely in the 1970s:

“Consciousness appears to be the last bastion of occult properties, epiphenomena, immeasurable subjective states — in short, the one area of mind best left to the philosophers. Let them make fools of themselves trying to corral the quicksilver of “phenomenology” into a respectable theory.”(1)

Consciousness no longer appears this strange to many researchers, but the philosophers just mentioned continue to hold that it may not be reduced to brain processes active in cognition. A common philosophical complaint is that any neurobiological theory of consciousness will always leave something out. What it will always leave out is the feeling itself — the feeling of what it is like to be aware, to see green, to smell flowers, and so on (Nagel 1974; Chalmers, 1996). These are so-called qualia — the experiences themselves — and these are what are important about consciousness. The philosopher making this argument may go on to conclude that no science can ever really explain qualia because it cannot demonstrate what it is like to see green if you have never seen green. Ultimately, they argue, consciousness is beyond the reach of scientific understanding.

By contrast, neuroscientists take for granted that consciousness will be domesticated along with the rest of cognition. Indeed, this work tends to assume that neuroscience will not only identify correlates of consciousness, but will eventually tell us what consciousness is. By and large, these neuroscientific efforts have been directed toward cortical regions of the brain, cortical pathways, and cortical activity. This is due, in part, to the prevalence of clinical studies of human patients with region-specific cortical lesions that are correlated with deficits in specific kinds of experiences. This tendency to focus on the cortex may also reflect the common knowledge that humans possess the highest level of consciousness of all animals and have proportionally more cortex than our closest relatives (and — so the supposition goes — therein lies the difference in levels of consciousness).

Another theory of consciousness, offered by Dr. Gerald M. Edelman, aims to resolve this “divorce” between science and the humanities over theories of consciousness. The premise of Edelman’s theory is that the field of neuroscience has already provided enough information about how the brain works to support a scientifically plausible understanding of consciousness. His theory attempts to reconcile the two positions described earlier by examining how consciousness arose in the course of evolution.

In his book on the topic, Second Nature: Brain Science and Human Knowledge, Edelman says:

“An examination of the biological bases of consciousness reveals it to be based in a selectional system. This provides the grounds for understanding the complexity, the irreversibility, and the historical contingency of our phenomenal experience. These properties, which affect how we know, rule out an all-inclusive reduction to scientific description of certain products of our mental life such as art and ethics. But this does not mean that we have to invoke strange physical states, dualism, or panpsychism to explain the origin of conscious qualia. All of our mental life, reducible and irreducible, is based on the structure and dynamics of our brain.

In essence, Edelman has attempted to construct a comprehensive theory of consciousness that is consistent with the latest available neuroanatomical, neurophysiological, and behavioral data. Calling his idea Neural Darwinism, Edelman explains that the brain is a selection system that operates within an individual’s lifetime. Neural Darwinism proposes that, during neurogenesis, an enormous “primary repertoire” of physically connected populations of neurons arises. Subsequently, a “secondary repertoire” of functionally defined neuronal groups emerges as the animal experiences the world. A neural “value system,” developed over the course of evolution and believed to be made up of small populations of neurons within deep subcortical structures, is proposed to assign salience to particular stimuli encountered by the animal in order to select patterns of activity.

For example, when the response to a given stimulus leads to a positive outcome the value system will reinforce the synaptic connections between neurons that happened to be firing at that particular moment. When a stimulus is noxious, the value system will similarly strengthen the connections between neurons that happened to be firing at the time the stimulus was encountered, thus increasing the salience of that stimulus. When a stimulus has no salience, synaptic connections between neurons that fired upon first exposure to that stimulus will become weaker with successive exposures.

Importantly, the mapping of the world to the neural substrate is degenerate; that is, no two neuronal groups or maps are the same, either structurally or functionally. These maps are dynamic, and their borders shift with experience. And finally, since each individual has a unique history, no two individuals will express the same neural mappings of the world.

This brings us to the three tenets of Edelman’s theory:

1. Development of neural circuits leads to enormous microscopic anatomical variation that is the result of a process of continual selection;

2. An additional and overlapping set of selective events occurs when the repertoire of anatomical circuits that are formed receives signals because of an animal’s behavior or experience;

3. “Reentry” is the continual signaling from one brain region (or map) to another and back again across massively parallel fibers (axons) that are known to be omnipresent in higher brains.

Edelman thus believes that consciousness is entailed by reentrant activity among cortical areas and the thalamus and by the cortex interacting with itself and with subcortical structures. He suggests that primary consciousness appeared at a time when the thalmocortical system was greatly enlarged, accompanied by an increase in the number of specific thalamic nuclei and by enlargement of the cerebral cortex — probably after the transitions from reptiles to birds and separately to mammals about a quarter of a billion years ago. Higherorder consciousness (i.e., consciousness of consciousness), on the other hand, is due to reentrant connections between conceptual maps of the brain and those areas of the brain capable of symbolic or semantic reference — and it only fully flowered with hominids when true language appeared. Regarding language and its relationship to higher-order consciousness, Edelman explains:

“We do not inherit a language of thought. Instead, concepts are developed from the brain’s mapping of its own perceptual maps. Ultimately, therefore, concepts are initially about the world. Thought itself is based on brain events resulting from the activity of motor regions, activity that does not get conveyed to produce action. It is a premise of brain-based epistemology that subcortical structures such as the basal ganglia are critical in assuring the sequence of such brain events, yielding a kind of presyntax. So thought can occur in the absence of language….

The view of brain-based epistemology is that, after the evolution of a bipedal posture, of a supralaryngeal space, of presyntax for movement in the basal ganglia, and of an enlarged cerebral cortex, language arose as an invention. The theory rejects the notion of a brainbased, genetically inherited, language acquisition device. Instead, it contends that language acquisition is epigenetic. Its acquisition and its spread across speech communities would obviously favor its possessors over nonlinguistic hominids even though no direct inheritance of a universal grammar is at issue. Of course, hominids using language could then be further favored by natural selection acting on those systems of learning that favor language skills.”

Such a theory is attractive because it does not simply concentrate on conscious perception, but it also includes the role of behavior. We do well to keep in mind that moving, planning, deciding, executing plans, and more generally, keeping the body alive, is the fundamental business of the brain. Cognition and consciousness are what they are, and have the nature they have, because of their role in servicing behavior.

An important element of Edelman’s theory that consciousness is entailed by brain activity is that consciousness is not a “thing” or causal agent that does anything in the brain. He writes that “inasmuch as consciousness is a process entailed by neural activity in the reentrant dynamic core it cannot be itself causal.” This process causes a number of “useful” illusions such as “free will.”

Edelman’s theory of consciousness has further implications for the development of brain-based devices (BBDs), which Edelman believes will be conscious in the future as well. His central idea is that the overall structure and dynamics of a BBD, whether conscious or not, must resemble those of real brains in order to function. Unlike robots executing a defined program, the brains of such devices are built to have neuroanatomical structures and neuronal dynamics modeled on those known to have arisen during animal evolution and development.

Such devices currently exist — such as the “Darwin” device under development by The Neurosciences Institute. Darwin devices are situated in environments that allow them to make movements to sample various signal sequences and consequently develop perceptual categories and build appropriate memory systems in response to their experiences in the real world.

And though Edelman recognizes that it is currently not possible to reflect the degree of complexity of the thalmocortical system interacting with a basal ganglia system, much less to have it develop a true language with syntax as well as semantics, he nevertheless suggests that someday a conscious device could probably be built.

More ambitiously, Edelman also thinks that contemporary neuroscience can contribute to a naturalized epistemology. The term “naturalized epistemology” goes back to the analytical philosopher Willard Quine and refers to a movement away from the “justification” (or foundations) of knowledge and emphasizes the empirical processes of knowledge acquisition. Edelman is largely sympathetic towards Quine’s project, but provides a broader evolutionary framework to epistemology that also permits internal states of mind (consciousness).

1 Daniel C. Dennett, “Toward a Cognitive Theory of Consciousness,” in Brainstorms: Philosophical Essays on Mind and Psychology (Montgomery, VT: Bradford Books, 1978).

16. October 2014 · Comments Off · Categories: Cryonics

Cryonics Magazine, August, 2013

Why Reversible Cryopreservation Matters

[The following is a text adaptation of a PowerPoint presentation given on Sunday, May 12, 2013 at the Resuscitation and Reintegration of Cryonics Patients Symposium in Portland, Oregon.]

Let’s start with the following definition of cryonics:

“Cryonics is the stabilization of critically ill patients at ultra-low temperatures to allow resuscitation in the future.”

As you can see, nothing in this definition says that repair is an intrinsic feature of cryonics. But is this a reasonable perspective? Let’s think about a number of aspects of cryonics that could be classified as “repair.”

• Critically ill patients are sick and will need medical treatment in the future.
• Most cryonics patients will require
rejuvenation.
• The cryopreservation process itself causes (irreversible) damage.

Yes, cryonics patients will require a second look at their condition by a future doctor who will have more advanced medical technologies at his/her disposal. This could conceivably be called “repair.” Most cryonics patients will also require rejuvenation biotechnologies. After all, it makes little sense to cure the patient’s disease but leave him/her in a fragile, debilitated state. This could be called “repair” too, in particular if you believe that aging is the progressive accumulation of damage. The repair that I want to discuss here is repair of the damage that is associated with the cryopreservation process itself. If we can eliminate this kind of damage, and the associated requirement of repair in the future, we will make the idea of cryonics a whole lot more attractive. What would be the advantages of being able to offer such “cryonics without repair?”

Perhaps the most obvious advantage is that cryonics could not be dismissed solely by pointing to the (irreversible) damage caused by the cryopreservation process itself. In essence, such a form of cryonics would be akin to putting a critically ill patient in a state of true suspended animation. This would strengthen the legal position of cryonics patients because a decision to abandon a patient in such a condition would be more akin to murder (or at least serious neglect). Another advantage would be that the absence of cryopreservation damage would increase the likelihood of the patient being restored to good health in the future. Less damage is also likely to translate into lower costs, too, and it is rather obvious that such an advantage can mean more security for the patient. Reversible cryopreservation may also lead to earlier treatment and resuscitation attempts, which may reduce challenges associated with re-integration. Cryonics without repair also matters in the here-and-now. Without the goal of reversible cryopreservation there are no objective, empirical criteria to evaluate the quality of care in a cryonics case. Last, but not least, we should do no harm. Allowing unnecessary injury of the patient because future advanced technologies should be able to fix it is a morally suspect gamble with a person’s life.

That is an impressive list of arguments in favor of offering reversible human cryopreservation. Now let’s try to be more specific about what cryonics without repair means. Clearly, the condition of the patient should not worsen relative to the critical condition the patient was in at the time of pronouncement of legal death. In fact, a rarely recognized possibility in a good cryonics case is that it might even be feasible to slightly improve the condition of the patient through the administration of cerebroprotective medications and washing out the blood, provided these procedures do not restore spontaneous circulation and consciousness, of course. A common perspective at Alcor to look at the objective of stabilization procedures is to say that these procedures should be aimed at maintaining viability of the patient by contemporary criteria. In the past I have characterized this objective as securing viability of the brain, but I think it would be better to aim for complete viability of the body unless there is a clear trade-off between viability of the brain (the most important organ in cryonics) and the rest of the body. Ultimately, though, we do not just want to be able to reverse the stabilization procedures but all cryonics procedures.

Before we walk through basic cryonics procedures to identify obvious and notso- obvious opportunities for cryonics procedures to produce additional damage, let’s look at circumstances in which the patient suffers additional damage that cannot be attributed to the cryonics organization. The most obvious situation is where there is a long delay between pronouncement of legal death and the start of cryonics procedures because hours go by before the patient is discovered or hospital administrators do not allow immediate access. It is important to recognize that the goal of maintaining viability can be defeated before we even start our procedures. Critics of cryonics often talk about compromising circumstances as if they are intrinsic aspects of cryonics instead of the result of tragic but avoidable events or hostile authorities. Reversible cryopreservation is only possible if the cryonics organization is notified in time and receives good cooperation from hospital administrators and other authorities.

The first real opportunity for a cryonics organization to “screw up” is to allow substantial periods of warm and cold ischemia. This can happen in a number of ways including, but not limited to, not restoring adequate circulation, inadequate ventilation, allowing blood pressure and cerebral perfusion to drop (restoring blood pressure does not guarantee good cerebral blood flow), suboptimal induction of hypothermia, or conducting surgery at high temperatures without metabolic support. In ideal circumstances a cryonics stabilization is conducted so that suboptimal results in one of these areas are offset by gains in the other protocols.

If a cryonics organization is able to provide metabolic support and rapidly cool down the patient to close to the freezing point of water the next challenges involve the cryopreservation process. The best known form of damage here is, of course, ice damage. While today’s vitrification agents are formulated to inhibit ice formation at realistic cooling rates, there are still a number of things that can go wrong. The distribution of cryoprotectant in the brain can be incomplete as a result of surgical errors or flaws during cryoprotective perfusion (e.g., vessels not properly cannulated, extremely low or high pressures, pumping air, etc.) The cryoprotectant can also be introduced at temperatures that are too warm or introduced too rapidly to allow the cells to maintain volume in an acceptable range. Even if none of these mistakes are made, we run into other challenges that cryonics organizations cannot successfully overcome yet.

Successful vitrification requires the use of high concentrations of organic solutes (such as DMSO and formamide) and non-penetrating polymers. While much progress has been made by cryobiology researchers Gregory Fahy and Brian Wowk to formulate solutions with low toxicity, and such solutions have been shown to successfully cryopreserve brain slices, our current understanding is that it is not likely that the brain of a cryonics patient remains spontaneously viable after being equilibrated with these agents. This is partly because the “blood brain barrier” leads to a situation in which solutes naturally present in the brain become concentrated during cryoprotective perfusion (dehydration) as discussed in the next paragraph. This causes cells inside whole brains to be cryoprotected by a mixture of natural solutes and some components of the perfused cryoprotectant solution rather than just the carefully-formulated cryoprotectant solution. Sometimes natural is not good.

It is sometimes said that eliminating cryoprotectant toxicity is the “holy grail” of cryonics research. While there is good empirical evidence to suggest that despite this toxicity good ultrastructure of the brain is still possible, true reversible human cryopreservation without reliance on sophisticated repair will require cryoprotectants with much lower toxicity. The need for less toxic cryoprotectants is especially tied into the problem of achieving concurrent and adequate distribution of cryoprotectant to all parts of the body that are vulnerable to freezing injury, which requires many hours of perfusion. In addition to cryoprotectant toxicity there are a number of other poorly-understood phenomena that could frustrate the ideal of cryonics without repair such as “chilling injury” and “thermal shock.”

An interesting form of injury that is not well known by the general public but that triggers a lot of discussion among cryonics researchers is dehydration of the brain. Without exception, a wellconducted cryopreservation of the brain with present technology produces severe shrinking. In fact, this shrinkage, and the corresponding increase in concentration of salts and proteins naturally present in the brain, appears to be a key mechanism by which whole brains vitrify despite limited permeability to perfused cryoprotectants. Evidence of substantial dehydration (obtainable by direct inspection of the brain inside the skull or via CT scans) is often considered an indicator of good care in cryonics. Of course, this leaves the question unanswered whether such a degree of dehydration is compatible with viability of the brain. Yuri Pichugin, the researcher who developed the Cryonics Institute’s current vitrification agent, VM-1, considered such extreme cerebral dehydration an obstacle to restoring viability after vitrification and identified a number of blood brain barrier modifiers that allowed him to recover brain slices after whole brain cryoprotective perfusion with improved viability. Whether such agents are of benefit or actually harmful is still an open research question.

Even if we could cryopreserve a human being without ice formation, toxicity, chilling injury, or other forms of injury associated with cryoprotection, there is still one remaining obstacle for reversible  cryopreservation: fracturing caused by thermal stress. While fracturing has been recognized as a problem and observed as an empirical phenomenon in patients as far back as the early 1980s, this form of injury has pushed itself to center stage (together with cryoprotectant toxicity and cerebral dehydration) since cryonics organizations started using vitrification agents aimed at eliminating ice formation altogether. If ice formation is eliminated, fracturing is the only mechanical form of damage left. While the significance of fracturing damage is sometimes downplayed by molecular nanotechnology experts, and fracturing at cryogenic temperatures doesn’t result in actual fragmentation, letting a human brain form fractures is not what most people would consider appropriate treatment of a critically ill patient.

What is striking, however, is how little we actually know about fracturing in cryonics patients. Fracturing has been observed in patients that were cryopreserved with (relatively) low concentrations of cryoprotectants. Such protocols produced ice formation and we should therefore not be surprised about observing cracking in those patients. Even in patients who have been cryopreserved using modern vitrification agents acoustic fracturing events (which may or may not correspond with actual fractures) have been detected above the glass transition temperature (Tg) of the pure vitrification solution. But even these observations have little relevance to the question of what we should expect in a good case. Many cryonics patients are perfused under sub-optimal conditions due to delays after clinical death. It is therefore likely that many of these fracturing events, if real, can be attributed to ischemia-induced perfusion impairment and ice formation. And that cooling frozen tissues to very low temperatures can cause fracturing is something we already know.

There are some encouraging preliminary research results suggesting that under ideal circumstances (i.e., good equilibration, controlled cooling) fracturing is not as serious a problem as it has been made out to be. The current practice of long term care at liquid nitrogen temperature may not be salvaged by such observations, but the intermediate temperature storage (ITS) systems that have been developed might be sufficient to eliminate this problem under good conditions at temperatures not too far below Tg. A related intriguing question is what the effect of severe cerebral dehydration is on the occurrence and frequency of fractures in the brain.

Let’s say that one agrees with the objective of “cryonics without repair” (or very limited repair), and the identification of the biggest scientific and technical obstacles to achieve this. What should our research and clinical objectives be? For starters, cryonics organizations should continue to cultivate an interest in personal alarm systems and securing good legal and logistical cooperation with providers of medical care. One technical development that deserves to be introduced is “field vitrification.” Strictly speaking, the phrase is a misnomer because we are not really talking about the patient being vitrified in a remote location; it is the cryoprotective perfusion part of the procedure that is done prior to transport to Alcor (in remote cases). Evidence from at least three labs indicates that perfusing the patient in the field with a vitrification solution and shipping on dry ice is safe, practical, and superior to blood substitution in most scenarios. While remote blood substitution (“washout”) is clearly demonstrated to be better than shipping the patient without removing the blood, it is not likely that hypothermic organ preservation solutions capable of keeping the brain viable for longer than 24 hours, and capable of inhibiting whole body edema, will be developed any time soon. Field vitrification is simply the next logical development in high-quality evidence-based cryonics. Other important improvements include better cooling efficiency (e.g., using cyclic cold lung lavage), improved cardiopulmonary support protocols, a renewed emphasis on monitoring during casework, and the introduction of intermediate temperature storage.

The most formidable challenge will be to develop what I call “brain-friendly” cryoprotectants. What needs to be accomplished? These agents should have no, or tolerable, toxicity, eliminate chilling injury and other poorly-understood forms of cryopreservation injury, allow safe and fracture-free storage at intermediate temperatures, and allow cryoprotective perfusion with greater penetration of agents into brain tissue with less dehydration so that results in whole brains can more closely match the high viabilities now obtainable in brain slices.

At my own company, Advanced Neural Biosciences, we have successfully developed a rat EEG model to screen for such brain-friendly cryoprotectants. As I write up this presentation, we have been successful in recovering integrated whole brain electrical activity after hypothermic circulatory arrest at 0° Celsius. Our next objectives are to recover EEG activity in the brain after cooling to subzero temperatures and to understand the relationship between cryoprotectants, the blood brain barrier, dehydration, and viability. It is too early to report any significant findings yet, but one thing that has become quite clear to us is that adequate ventilation during cool down is essential to recovery of whole brain activity. This is rather important because cryonics organizations have not been that concerned about meeting the brain’s demand for oxygen during stabilization, and during blood washout and blood substitution in particular. No doubt, if we continue this research we will learn other things that have direct relevance to the practice of cryonics.

The whole brain cryopreservation research project has been made possible by the generous support of the Life Extension Foundation. The author also wishes to thank the Immortalist Society, Cryonics Institute, Alcor, LongeCity, 21st Century Medicine, Alan Mole, York Porter, Jordan Sparks, David Ettinger, Ben Best, Mark Plus, Peter Gouras, James Clement, Luke Parrish, and John Bull for additional support.

15. October 2014 · Comments Off · Categories: Cryonics, Science

Cryonics Magazine, July 2013

[The following is a text adaptation of a PowerPoint presentation given on Sunday, May 12, 2013 at the Resuscitation and Reintegration of Cryonics Patients Symposium in Portland, Oregon]

An understanding of probable future repair requirements for cryonics patients could affect current cryostorage temperature practices. I believe that molecular nanotechnology at cryogenic temperatures will probably be required for repair and revival of all cryonics patients in cryo-storage now and in the foreseeable future. Current nanotechnology is far from being adequate for that task. I believe that warming cryonics patients to temperatures where diffusion-based devices could operate would result in dissolution of structure by hydrolysis and similar molecular motion before repair could be achieved. I believe that the technologie for scanning the brain/mind of a cryonics patient, and reconstructing a patient from the scan are much more remote in the future than cryogenic nanotechnology.

Cryonicists face a credibility problem. It is important to show that resuscitation technology is possible (or not impossible) if cryonicists are to convince ourselves or convince others that current cryonics practice is not a waste of money and effort. For some people it is adequate to know that the anatomical basis of the mind is being preserved well enough ― even if in a very fragmented form ― that some unspecified future technology could repair and restore memory and personal identity. Other people want more detailed elaboration.

Books have detailed what nanotechnology robots (nanorobots) will look-like and be capable-of, including (notably) Nanosystems by K. Eric Drexler (1992) and Nanomedicine by Robert A. Freitas, Jr. (Volume I, 1999; Volume IIA, 2003). The online Alcor library contains articles detailing repair of cryonics patients by nanorobots at cryogenic temperature, in particular, “A Cryopreservation Revival Scenario using Molecular Nanotechnology” by Ralph Merkle and Robert Freitas as well as “‘Realistic’ Scenario for Nanotechnological Repair of the Frozen Human Brain.” Despite the detailed descriptions, calculations, and quantitative analyses that have been given, any technology as remote from present capabilities as cryogenic nanotechnology is certain to be very different from whatever anyone may currently imagine. It is difficult to argue against claims that all such descriptions are nothing more than handwaving, blue-sky speculations.

Current medical applications of nanotechnology are mainly limited to the use of nanoparticles for drug delivery.1 Nanomachines are being built, but they are little more than toys ― including a rotor that can propel a molecule2 or microcantilever deflection of DNA by electrostatic force.3 In classical mechanics and kinetic theory of gases, on a molecular level, temperature is defined in terms of the average translational kinetic energy of molecules, which means that the lower the temperature the slower the motion of the molecules. According to the Arrhenius Equation, the rate of a chemical reaction declines exponentially with temperature decline. It would be wrong to conclude that nanomachines would barely be able to move at cryogenic temperatures, however. Nanomachines operate by mechanical movement of constituent atoms, a process that is temperature-independent. In fact, nanomachines would probably operate more effectively at cryogenic temperature because there would be far less jostling of atoms in the molecular structures upon which nanomachines would operate. Nanomachines would also be less vulnerable to reactions with oxygen at cryogenic temperature, although it would nonetheless be preferable for cryogenic nanorepair to occur in an oxygen-free environment.

Although under ideal circumstances ice formation can be prevented in cryonics patients, circumstances too often result in at least some freezing―such as inability to perfuse with vitrification solution, or poor perfusion with vitrification solution because of ischemia due to delayed treatment. Past cryonics patients were perfused with the (anti-freeze) cryoprotectant glycerol, whereas cryonics patients are currently perfused with cryoprotectant solutions that include ethylene glycol and dimethylsulfoxide (DMSO). Unlike water, which forms crystalline ice when solidifying upon cooling, cryoprotectants form an amorphous (non-crystalline, vitreous) solid (a “hardened liquid”) when solidifying upon cooling. The “hardened liquid” is a glass rather than an ice. The temperature at which the solidification (vitrification) occurs is called the glass transition temperature (Tg).

For M22, the cryoprotectant used by Alcor to vitrify cryonics patients, Tg is typically between −123°C and −124°C (depending on the cooling rate). Tg is about the same for the cryoprotectant (VM-1) used for cryonics patients at the Cryonics Institute. Although freezing can be reduced or eliminated by perfusing cryonics patients with vitrification solution before cooling to Tg, eliminating cracking is a more difficult problem. Cryonics patients are cooled to cryogenic temperatures by external cooling. Thermal conductivity is slow in a cryonics patient, which means that the outside gets much colder than the inside. When the outside of a sample cools more quickly than the inside of the sample, thermal stress results. A vitrified patient subjected to such thermal stress can crack or fracture. No efforts have been made to find additives to M22 that would have a similar effect as boron oxide has on allowing Pyrex glass to reduce thermal stress.

If a vitrified sample is small enough, and if cooling is slow enough, the sample can be cooled far below Tg ― down to liquid nitrogen temperature ― without cracking. A rabbit kidney (10 milliliter volume) can be cooled down to liquid nitrogen temperature in two days without cracking/fracturing.6 Cryonics patients are much too large to be cooled to liquid nitrogen temperature over a period of days without cracking. The amount of time required for cooling vitrified cryonics patients to liquid nitrogen temperature without cracking is unknown, and would probably be much too long.

In 1990 cryobiologist Dr. Gregory Fahy published results of cracking experiments that he performed on samples of the cryoprotectant propylene glycol.4 Tg for propylene glycol is −108°C, but in RPS-2 carrier solution the Tg is −107°C. In one experiment he demonstrated that cracking began at lower temperatures for smaller samples, specifically: −143°C for 46 mL, −116°C for 482 mL, and −111°C for 1412 mL. (The last volume is comparable to the volume of an adult human brain.) Dr. Fahy also demonstrated that cracking could be delayed by cooling at slower cooling rates. But when cracking did occur, the cracks formed at the lower temperatures were finer and more numerous.

Based on evidence that large cracks formed at higher temperatures by more rapid cooling results in a relief of thermal stress that prevents the fine and more numerous cracks formed when cracking begins at lower temperature, the Cryonics Institute (CI) altered its cooling protocol for cryonics patients. CI patients are cooled quickly from −118°C to −145°C, and then cooled slowly to −196°C.5 In order to minimize or eliminate cracking in cryonics patients, proposals have been made to store the patients at temperatures lower than Tg (−124°C), but higher than liquid nitrogen temperature (−196°C).6 Such a cryo-storage protocol is described as Intermediate Temperature Storage (ITS). Alcor currently cares for a number of ITS patients at −140°C, but a consensus has not yet been reached about what ITS temperature will be chosen when this service is made available to all Alcor members.

Although Alcor’s vitrification solution M22 can prevent ice formation with some samples and protocols, M22 cannot prevent ice nuclei from forming at cryogenic temperatures. Ice nuclei are local clusters of water molecules that rotate into an orientation that favors later growth of ice crystals when a solution is warmed. Ice nuclei are not damaging, but the fact that ice nuclei can form indicates molecular mobility which could be damaging. Specifically, between the temperatures of −100°C and −135°C, ice nuclei can form in M22, with the maximum ice nucleation rate occurring near Tg. At −140°C the ice nucleation rate for M22 is undetectable. But nuclei will be probably formed in cooling to −140°C.

Although cryostorage at −140°C is an attempt to minimize cracking and minimize nucleation, this ITS neither eliminates cracking nor ice nuclei formation. Cryonics patients slowly cooled from Tg to −140°C will surely experience some ice nucleation. Alcor places a listening device (“crackphone”) under the skull of its cryonics patients for the purpose of monitoring cracking events. My understanding is that for most Alcor patients the crackphone detects cracking at Tg or only slightly below Tg, although there was reportedly one M22-perfused patient for which the first fracturing event occurred at −134°C. The propylene glycol experiments would support the view of cracking occurring slightly below Tg, but vitrified biological samples resist cracking better than pure cryoprotectant solutions.

With ice formation, cracking could occur at temperatures higher than Tg. Although ITS may prevent the formation of cracking that could occur in cooling below −140°C, it does not prevent the cracks that occur in cooling from Tg to −140°C. I have wondered whether there are forms of damage which would occur in a cryonics patient stored at −140°C that would not occur during storage at −196°C. A solid cryogenic state of matter does not prevent molecular motion. Molecular motion in a biological sample held at cryogenic temperature could result in damage to that sample.

Ions generated by radiation are much more mobile than molecules. An ionic species (probably protons) in trimethylammonium dihydrogen phosphate glass is nine orders of magnitude more mobile than the glass molecules—and sodium ions in sodium disilicate glass are twelve orders of magnitude more mobile than the glass molecules.9

Cryobiologist Peter Mazur has stated that below −130°C “…viscosity is so high (>1013 Poise) that diffusion is insignificant over less than geological time spans.” He adds that “…there is no confirmed case of cell death ascribed to storage at −196°C for some 2-15 years and none even when cells are exposed to levels of ionizing radiation some 100 times background for up to 5 yr.”10 Frozen 8-cell mouse embryos subjected to the equivalent of 2,000 years of background gamma rays during 5 to 8 months in liquid nitrogen showed no evident detrimental effect on survival or development.11

In attempting to evaluate damaging effects of temperature and radiation, it could be valuable to analyze chemical alterations, rather than complete cell death or viability. Acetylcholinesterase enzyme subjected to X-ray irradiation shows conformational changes at −118°C, but no conformational changes when irradiated at −173°C.12 X-ray irradiation of insulin and elastase crystals resulted in four times as much damage to disulfide bridges at −173°C compared to −223°C.13 Another study showed a 25% crystal diffraction lifetime extension for D-xylose isomerase crystals X-ray irradiated at less than −253°C compared to those irradiated at −173°C.14

One study showed that lettuce seeds show measurable deterioration when stored at liquid nitrogen temperature for periods of 10 to 20 years. Rotational molecular mobility was quantified. A graphical plot was generated showing increasing times for when 50% of lettuce seeds would fail to germinate as a function of decreasing temperature. Those times were estimated to be about 500 years for −135°C and about 3,400 years for −196°C.15 Translational vibrational motion has been given as an explanation for seed quality deterioration at cryogenic temperatures.16 The mean square vibrational amplitude of a water molecule is not even zero at 0 Kelvins (−273°C), and has been determined to be 0.0082 square Angstroms. The mean square vibrational amplitude is 0.0171 square Angstroms at −173°C and 0.0339 square Angstroms at −73°C.17

Realistically, however, 3,400 years is much longer than cryonics patients are likely to be stored. Storage in liquid helium at −269°C or in a shadowed moon crater at −235°C18 would certainly be more trouble than it is worth. Northern wood frogs spend months in a semi-frozen state at −3°C to −6°C, and are able to revive with full recovery of heartbeat upon re-warming.19 An empirical study of a cryoprotectant very similar to M22 (VS55)
showed viscosity continuing to increase exponentially below Tg, just as viscosity increases exponentially with temperature decrease above Tg.20 The exponential decrease in viscosity (molecular mobility) that makes ice nucleation cease at −135°C indicates that there is probably little molecular mobility at −140°C, despite the possibility of damage from ionic species or vibrational motion. All things considered, however, my personal preference is for storage in liquid nitrogen, rather than some intermediate temperature above −196°C. I would also prefer for cryogenic nanorobot repair to be at liquid nitrogen temperature.

I am by no means a nanotechnology expert, but I can give a brief description of my own views of how cryogenic nanotechnology repair of a cryonics patient would proceed. I must thank Ralph Merkle for his assistance in allowing me to consult with him to formulate and clarify many of my views. I believe that repair of cryonics patients at cryogenic temperature would be a combination of nano-mining and nanoarcheology. Nanorobots (nanometer-sized robots) would first clear blood vessels of water, cryoprotectant, plasma, blood cells, etc. The blood vessels would become mining shafts that would provide access to all body tissues. Nanometer-sized conveyor belts or trucks on rails could remove blood vessel contents. Where freezing or ischemia had destroyed blood vessels, artificial shafts would be created. Unlike the nano-mining that simply removes all blood vessel contents, the creation of artificial shafts would have the character of an archeological dig. Care would be taken in removing material to avoid damaging precious artifacts that might indicate original structure ― which could
be discovered at any unexpected moment.

Section 13.4 of K. Eric Drexler’s book Nanosystems provides diagrams and details of a nanorobot manipulator arm. Such a “diamondoid” component would contain about four million atoms, and could be fitted with a variety of tools at the end of the arm. A variety of tips with varying degrees of chemical reactivity could allow for reversible, temporary chemical bonds that could be used for grabbing and moving molecules. These could range from radicals or carbenes that would form strong covalent bonds, to boron that can form relatively weak and reversible bonds to nitrogen and oxygen, to simple O-H groups that can form even weaker hydrogen bonds. Tools for digging need not be so refined. The manipulator arm is depicted as being 100 nanometers long and 50 nanometers wide, although nanorobots would need to be larger to include capability for locomotion, computation, and power. A complete nanorobot could be as large as a few thousand nanometers in size. A capillary is between 5,000 to 10,000 nanometers in diameter, so there should be plenty of room for many such nanorobots to operate. Ralph Merkle estimates that 3,200 trillion nanorobots weighing a total of 53 grams could repair a cryonics patient in about 3 years.21,22 Like many of the calculations associated with nanotechnology, I take these figures with a pound of salt. It is certainly true, however, that it could take years to repair a patient, and that there should not be a rush to finish the job.

Merkle & Freitas have suggested that nanorobots be powered by electrostatic motors. Stators and rotors would be electric rather than magnetic. Tiny moving charged plates are easier to fabricate than tiny coils and tiny iron cores, but more fundamentally, magnetic properties do not scale well with reduced size (i.e., molecular-scale magnetic motors don’t work), whereas electrostatic properties do scale well with reduced size. Electrostatic actuators are already being used in microelectromechanical systems (MEMS).23 High density batteries could provide power for days, and recharging stations could be located throughout the patient. Alternatively, nanotube cables could bring power to the patient from the outside. Such cables could also be a means of transmitting and receiving computational data. Nanotube cables could also be used to reunite fracture faces
created by cracking. Scanning and image processing capabilities would need to evaluate what needs to be fixed.

As much as possible I would favor replacement rather than repair, which would greatly simplify the process. It would be much easier to replace a kidney than to repair the diseased kidney of an elderly patient who died of kidney disease. Curing disease and rejuvenation would thus become part of the repair of a cryonics patient. Of course, neuro patients would require an entirely new body. The brain would be the major exception to replacement strategy because the brain could not be replaced without loss of memory and personal identity.

Even within the brain, however, it could be feasible to replace many components without loss of memory and personal identity. It could be feasible to replace many organelles such as mitochondria, lysosomes, etc., and many macromolecules such as proteins, carbohydrates, and lipids. DNA could be repaired, and possibly even modified to cure genetic disease, but epigenetic expression in neurons may be critical for reconstruction of synaptic structure. Synaptic connections would not only be restored, but the quantity and quality of neurotransmitter contents should be restored. It is not simply a matter that some neurotransmitters are inhibitory and others are stimulatory. There are more than 40 different neurotransmitters used in the brain, and there must be a good reason why such variety is necessitated.

Part of the repair process could involve removal of ice nuclei, nearly all of which would be extracellular. Re-created blood vessel contents would include fresh cryoprotectant, water, plasma, and blood cells without the original ice nuclei. Although some repair scenarios favor different types of repair above cryogenic temperature, I doubt that this is necessary or desirable. Alternative repair scenarios involve splitting the brain in half, and halving the halves repeatedly at cryogenic temperature—with digitization at each step—until the brain has been totally digitized.21,22 Or digitization could be done by repetitive nano-microtomes at cryogenic temperature. The digital data could be used for full reconstruction. Some people might object that if one individual could be created from digital data, many such individuals could be created—raising questions of which are duplicates and
which is the original. There is detailed discussion of the duplicates problem/ paradox in the philosophy section of my website BENBEST.COM.

Although other repair scenarios could prove to be feasible, I believe that cryogenic nanotechnology will be required for all cryonics patients in the foreseeable future until the problem of cryoprotectant toxicity can be solved. With effective nontoxic cryoprotectants, sufficient cryoprotectant could be used to prevent ice nuclei formation at all temperatures, prevent devitrification (freezing) upon rewarming, and eliminate all toxic damage. In such a case, there could be true reversible cryopreservation (suspended animation).

What is needed to create the nanotechnology required for repair of cryonics patients? Small machines will need to build parts for smaller machines, which would in turn build even smaller machines. Many details of machine
operation must be perfected at each stage. Current modern technological civilization began with cave people pounding on rocks. Ralph Merkle has said that compared to future technology, current technology is pounding on rocks.

References

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11. Glenister PH, Whittingham DG, Lyon MF. Further studies on the effect of radiation during the storage of frozen 8-cell mouse embryos at -196 degrees C. J Reprod Fertil. 1984 Jan;70(1):229-34.

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13. Meents A, Gutmann S, Wagner A, Schulze-Briese C. Origin and temperature dependence of radiation damage in biological samples at cryogenic temperatures. Proc Natl Acad Sci U S A. 2010 Jan 19;107(3):1094-9.

14. Chinte U, Shah B, Chen YS, Pinkerton AA, Schall CA, Hanson BL. Cryogenic (<20 K) helium cooling mitigates radiation damage to protein crystals. Acta Crystallogr D Biol Crystallogr. 2007 Apr;63(Pt 4):486-92.

15. Walters C, Wheeler L, Stanwood PC. Longevity of cryogenically stored seeds. Cryobiology. 2004 Jun;48(3):229-44.

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