Tag: Organ Preservation

At last, a sure-cold way to sell cryonics with guaranteed success!

A humorous romp through a promising new technique in aesthetic medicine from one cryonicist’s (warped) point of view.

Figure 1: Before cryopreservation (L) and after cryopreservation (R).

As everyone involved in cryonics for more than a fortnight is sadly aware, cryonics doesn’t sell. Indeed, if we were pitching a poke in the eye with a sharp stick, we’d more than likely have more takers than we’ve had trying to ‘market’ cryonics to the public. To see evidence that this is so, you need only wander around a shopping mall on a weekend and observe all the (painfully) stainless steel lacerated and brightly colored needle-pierced flesh sported by the young and trendy and increasing by the old and worn, as well.

Yes, it’s clear; we misread the market, to our lasting detriment.

It’s true that we’ve tried the ‘you’ll be rich when you wake you up line,’ and heaven knows we’ve beaten the ‘you’ll be young and beautiful forever’ line, well, virtually beaten it to death. And while people are certainly interested in great fortune and youth, both of these things share the same unfortunate shortcoming, namely that they are things that people either don’t have but want, or do have and don’t want to lose. As anyone who is really savvy at marketing will tell you, the best way to sell something is to promise (and preferably be able to deliver) that you can get rid of something that people have and really don’t want – something that is ruining the quality of their life, destroying their health, draining their pocketbook and, worst of all, making them really, really ugly.

So, it turns out that for onto 50 years now, we’ve missed the real selling point of cryonics that’s been there all along: IT WILL MAKE YOU THIN! Guaranteed!

Can such a claim be true? Well, surprisingly, the answer would seem to be an almost unqualified, “Yes!”

Recently it’s been discovered that adipocytes, the cells responsible not only for making you fat, but for making you hungry, as well, are particularly susceptible to a phenomenon in cryobiology that has proved a nettlesome (and only recently (partially) overcome) barrier to solid organ cryopreservation: chilling injury. Quite apart from freezing damage due to ice crystals forming, adipocytes are selectively vulnerable to something called ‘chilling injury.’ 1-5 Chilling injury occurs when tissues are cooled to a temperature where the saturated fats that comprise their cell membranes (external and internal) freeze. You see, saturated fat, which is the predominant type of fat in us humans, freezes well above the temperature of water – in fact, it freezes at just below room temperature. That’s why that big gash of fat on the edge of your T-bone steak is stiff and waxy when it is simply refrigerated, and not frozen.

Figure 2: Chilling injury is thought to result from crystallization of cell membrane lipids.

Chilling injury isn’t really well understood. In the days before both cryobiology and indoor heating, humans used to experience a very painful manifestation of it in the form of chilblains – tender swelling and inflammation of the skin due to prolonged cold exposure (without freezing haven taken place). In the realm of organ preservation it is currently thought that chilling injury occurs when cell membranes are exposed to high subzero temperatures (-5oC to -20oC), again, in the absence of freezing.

There is evidence that the lipids (fats) that make up the smooth, lamellar cell membranes undergo crystallization when cells are cooled much below 0 deg C. Since the crystals are hexagonal in shape and have a hole in the middle, this has the effect of creating a pore or hole in the membrane. Cells don’t like that – those holes let all kinds of ions important to cells keeping their proper volume and carrying on their proper metabolic functions leak in and out, as the case may be. This isn’t merely an inconvenience for cells, it’s downright lethal. Without boring you with technical details, it is possible to partially address this state of affairs in organ preservation by adjusting the ‘tonicity’ of the solution bathing the cells: oversimplifying even more, this means by increasing  the concentration of salts to a concentration higher than would normally be present

Figure 3: Contouring of the skin in a pig subjected to brief, subzero cooling of subcutaneous fat.

But, to return to our chilled adipocytes and the promise not only of weight loss, but of a fat-free future; adipocytes are killed, en masse, when their temperature is dropped to between 0 and -7oC. Within a few days of exposure to such temperatures they undergo programmed cell death (apoptosis) and within a couple of months they are phagocytized by the body; and all that ugly and unwanted fat is carted off to be used as fuel by the liver. Now the rub would seem to be that this effect is most pronounced when the temperature of the tissue is cooled to below the freezing point of water and held there – preferably for a period of 10 minutes or longer.

That sounds dire, doesn’t it? What about the skin, the fascia, blood vessels, and the other subcutaneous tissues that will FREEZE (in the very conventional sense of having lots and lots of ice form in them)? Well, the answer, as any long-time experimental cryobiologist will know (even if he won’t tell you) is: pretty much nothing. Way back in the middle of the previous century, a scientist named Audrey Smith and her colleagues at Mill Hill, England found that you could freeze hamsters ‘solid’ – freeze 70+% of the water in their skin and 50% of the water in their bodies – and they would recover from this procedure none the worse for wear. Similarly, those of us who have carelessly handled dry ice for a good part of our lives will tell you that we see parts of our fingertips turn into stiff chalky islands of ice all the time, with the only side effect being a bit of temporary numbness that resolves in a few days to a week – certainly a side effect well worth it to avoid the considerable inconvenience of rummaging around to find a pair of protective gloves.

Figure 4: The Zeltiq Cool Sculpting Cryolipolysis device.

But alas, we scientists (most of us, anyway) are not a very entrepreneurial lot, and so we never thought either of inventing the ZeltiqTM cryolipolysis system, or using ‘the thin-new-you’ as a marketing tool for cryonics.

Yes, that’s right; some very clever folks have found a way to make a huge asset out of a colossal liability – to organ preservationists, anyway. Around 2004 a Minneapolis dermatologist named Brian Zellickson, MD, who specialized in laser and ultrasonic skin rejuvenating procedures, made a not so obvious connection. Both laser and skin ‘face-lifting’ and skin ‘rejuvenation’ procedures rely on the subcutaneous delivery of injuring thermal energy to the tissues of the face, or other treated parts of the body (cellulite of the buttocks and thighs are two other common areas for treatment). These energy sources actually inflict a second degree burn in a patchy and well defined way to the subdermal tissues.

Now this may seem a very counterintuitive thing to do if you are trying to induce ‘rejuvenation’ or ‘lift’ a sagging face. But if you think about it, it makes a great deal of sense. As any burn victim will tell you, one of the most difficult (and painful) parts of recovery is stretching the highly contracted scar tissue that has formed as a result of the burn injury. Indeed, for many patients with serious burns over much of their body, the waxy, rubbery and very constricting scar tissue prevents the return of normal movement, and can lock fingers and even limbs into a very limited range of motion. Many burn victims must do painful stretching exercises on a daily basis to avoid the return of this paralyzing skin (scar) contracture.

And it must be remembered that aged skin – even the skin of the very old – can still do one thing, despite the many abilities it has lost with age, and that thing is to form scar tissue in response to injury. Thus, laser and ultrasonic heating of normal (but aged) skin induces collagen proliferation and large-scale remodeling of the skin. For all the bad things said about scar tissue it is still a remarkable achievement in that it does constitute regenerated tissue. Regenerated tissue which does the minimum that normal skin must do to keep us alive: provide a durable covering that excludes microbial invasion, and prevents loss of body fluids. By injuring the tissue just below the complexly differentiated layer of the dermis (with its hair follicles, sweat glands and highly ordered pigmentation cells) much of the benefit of ‘scarring’ is obtained without the usual downsides.

The injured tissues respond by releasing collagen building cytokines as well as cytokines that result in angiogenesis (new blood vessel formation) and widespread tissue remodeling. And all that newly laid down collagen contracts over time, tightening and lifting the skin – and the face it is embedded in. These techniques may justly be considered much safer versions of the old fashioned chemical face peel, which could be quite effective at erasing wrinkles and achieving facial ‘rejuvenation,’ but was not titrateable and was occasionally highly unpredictable: every once in awhile the result was disastrous burning and accompanying long term scarring and disfiguration of the patient’s face.

St some point Dr. Zellickson seems to have realized that the selective vulnerability of adipocytes to chilling offered the perfect opportunity for a truly non-invasive approach to ‘liposuctioning’ by using the body’s own internal suctioning apparatuses, the phagocytes, to do the job with vastly greater elegance and panache than any surgeon with a trocar and a suction machine could ever hope to do. Thus was invented the Zeltiq Cool SculptTM cryolipolysis machine.6

Figure 5: The cooling head of the Zeltiq devive equipped with ultrasonic imaging equipment and a suction device to induce regional ischemia and hold the tissue against the cooling surface.

The beauty of cryolipolysis is that it is highly titrateable, seems never to result to in excessive injury to, or necrosis of the overlying skin, and yields a smooth and aesthetically pleasing result. Not unjustifiably for this reason it is marketed under the name Cool SculptingTM. The mechanics of the technique are the essence of simplicity. The desired area of superficial tissue to be remodeled is entrained by vacuum in a cooling head equipped with temperature sensors, an ultrasonic imaging device, and a mechanical vibrator. The tissue in the cooling head is sucked against a conductive surface (made evenly conductive by the application of a gel or gel-like dressing to the skin) where heat is extracted from it. The tissue is cooled to a temperature sufficient to induce apoptosis in the adipocytes, while at the same time leaving the overlying skin untouched. The depth of cooling/freezing is monitored by ultrasound imaging and controlled automatically by the Zeltiq device.  At the appropriate point in the cooling process the tissue is subjected to a 5 minute period of mechanical agitation (massage) which helps to exacerbate the chilling injury, perhaps by nucleating the unfrozen fat causing it to freeze.7 When the treatment is over, the device pages an attendant to return to the treatment room and remove it.

The tissue under vacuum is also made ischemic – blood ceases to flow, and this has the dual advantage of speeding the course of the treatment by preventing the blood borne delivery of unwanted heat – and more importantly, by making the cooling more uniform, predictable and reproducible. It also has the effect of superimposing ischemic injury on top of the chilling injury which is something that seems to enhance adipocyte apoptosis. The whole treatment, in terms of actual cooling time, takes about 60 minutes. In the pig work which served as the basis for the human clinical treatments, the duration of treatment was only 10 minutes: but the cooling temperature was also an ‘unnerving’ -7oC. The degree of temporary and fully reversible peripheral nerve damage (that temporary numbness us ‘dry ice handlers’ know so well) was more severe at this temperature, although it resolved in days to a week or two, without exception.

As previously noted, cryolipolysis causes apoptosis of adipocytes and this results in their subsequently being targeted by macrophages that engulf and digest them. This takes time, and immediately after treatment there are no visible changes in the subcutaneous fat. However, three days after treatment, there is microscopic evidence that an inflammatory process initiated by the apoptosis of the adipocytes is underway, as evidenced by an influx of inflammatory cells into the fat of the treated tissues. This inflammatory process matures between seven and fourteen days after treatment; and between fourteen and thirty days post-treatment, phagocytosis of lipids is well underway. Thirty days after treatment the inflammatory process has begun to decline, and by 60 days, the thickness of interlobular septa in the fat tissue has increased. This last effect is very important because it is weakness, or failure of the interlobular fat septae that is responsible for the ugly ‘cottage cheese’ bulging that is cellulite. Three months after the treatment you get the effect you see below on the ‘love handles’ of this fit, and otherwise trim fellow. Thus, it is fair to say that Cool SculptingTM is in no way a misnomer.

Figure 6: Art left is a healthy, fit young male who has persistent accumulation of fat in the form of ‘love handles’ that are resistant to diet and exercise and the same man 3 months after cryolipolysis.

Does cryolipolysis really work? The answer is that it works extremely well for regional remodeling or sculpting of adipose tissue – those pesky love handles, that belly bulge around the navel, that too plump bum, or those cellulite marred thighs. So far it has not been used to try and ablate large masses of fat – although there seems no reason, in principal, why this could not be done using invasive techniques such as pincushioning the fat pannus with chilling probes, as is done with cryoablation in prostate surgery. However, this would be invasive, vastly more expensive, and likely to result in serious side effects.

And that was one of the really interesting things about the research leading up to FDA approval of cryolipolysis: it seems to cause no perturbation in blood lipids, no disturbance of liver function (the organ that has to process all that suddenly available fat) and no global alterations in immune function. It seems to be safe and largely adverse effect free. There is some localized numbness (as is the case in freezing of skin resulting from handling dry ice) but it resolves without incident with a few weeks of the procedure.8

So, all of this makes me wonder, since human tissues tolerate ice formation and respond to it in much the same way as they do to laser or ultrasound ‘rejuvenation’ (depending upon the degree of damage) a logical question is, “would it be possible to use partial freezing of the skin – just enough to provoke the remodeling response – as a method of facial rejuvenation?” It should be safer than a chemical people and it is, like laser and ultrasound therapy, titrateable.

Figure 7: “Gad darn it, this shiny gold stuff keeps getting into the silt I’m tryin to git out of this here river!”

Which returns me to the whole subject of cryonics: fat is very poorly perfused and it seems unlikely that things done to moderate or abolish chilling injury will be nearly so effective for the adipocytes in fat (if it they are effective at all). That means that we might well all come back from our cryogenic naps not only young, via the magic of nanotechnology and stem cell medicine, and rich via the miracle of compound interest (which none other than Albert Einstein once remarked was “the most powerful force in the universe”), but also THIN! For all these years organ cryopreservationists, like Fahy and Wowk, have been panning for the mundane silt of a way around a chilling injury9 all the while discarding the gleaming nuggets of gold that were persistently clogging up their pans.

We cryonicists should not repeat their error and should realize a good thing when we see it. Now, for the first time, we can credibly claim that if you get cryopreserved you’ll come back not only young and rich, but young and rich and beautiful and thin!

Methinks there must be very few in the Western World today, man woman or child, who can resist a product that has all that to offer – and which, by the way, bestows practical immortality in the bargain.

Ok, Ok, maybe we shouldn’t mention that last part about immortality; it might scare the children.

REFERENCES:

1)     Wiandrowski TP, Marshman G. Subcutaneous fat necrosis of the newborn following hypothermia and complicated by pain and hypercalcaemia. Australas J Dermatol 2001;42:207–10.

2)     Diamantis S, Bastek T, Groben P, Morrell D. Subcutaneous fat necrosis in a newborn following icebag application for treatment of supraventricular tachycardia. J Perinatol 2006;26:518–

3)     Lidagoster MI, Cinelli PB, Levee´ EM, Sian CS. Comparison of autologous fat transfer in fresh, refrigerated, and frozen specimens: an animal model. Ann Plast Surg 2000;44:512–5.

4)      Wolter TP, von Heimburg D, Stoffels I, et al. Cryopreservation of mature human adipocytes: in vitro measurement of viability. Ann Plast Surg 2005;55:408–13.

5)      Manstein D, Laubach H, Watanabe K, Farinelli W, Zurakowski D, Anderson RR. Selective cryolysis: a nivel method of noninvasive fat removal. Lasers Surg Med 2008;40:595–604.

6)     Avram MM, Harry RS. Cryolipolysis for subcutaneous fat layer reduction. Lasers Surg Med. 2009 Dec;41(10):703-8. Review. PubMed PMID: 20014262.

7)     Zelickson B, Egbert BM, Preciado J, Allison J, Springer K, Rhoades RW, Manstein D. Cryolipolysis for noninvasive fat cell destruction: initial results from a pig model. Dermatol Surg. 2009 Oct;35(10):1462-70. Epub 2009 Jul 13. PubMed PMID: 19614940.

8)     Coleman SR, Sachdeva K, Egbert BM, Preciado J, Allison J. Clinical efficacy of noninvasive cryolipolysis and its effects on peripheral nerves. Aesthetic Plast Surg. 2009 ul;33(4):482-8. Epub 2009 Mar 19. PubMed PMID: 19296153.

9)     Fahy GM, Wowk B, Wu J, Phan J, Rasch C, Chang A, Zendejas E. Cryopreservation of organs by vitrification: perspectives and recent advances. Cryobiology. 2004 Apr;48(2):157-78.

Evidence-based cryonics

Cryonics patients can greatly benefit from rapid stabilization after pronouncement of legal death. One fortunate feature of stabilization procedures is that the most effective and validated procedures are relatively inexpensive and easy to perform.  The difference between no stabilization procedures at all and procedures that aim to rapidly restore blood circulation and drop the patient’s temperature is likely to be bigger than that between such basic stabilization and procedures that include administration of a large number of medications and remote blood washout.  This observation gains even more importance when it is considered that there is a serious lack of empirical data to support these more advanced procedures.

To date, no single neuroprotective agent has been approved for the treatment of global or focal ischemia. Despite this fact, cryonics organizations like Alcor and Suspended Animation administer an unorthodox number of medications to protect the brain and prevent impairment of circulation. While there are peer reviewed papers that combine a number of medications, there is no precedent in mainstream medicine or biomedical research in using such a large number of medications (in contemporary cryonics, medications protocol exceeds 12 different drugs and fluids). The only existing justification for using current protocol reflects work done at Critical Care Research in the 1990s. Although scattered reports exist about the effectiveness of this protocol in resuscitating dogs from up to 17 minutes of normothermic global ischemia, no detailed (peer reviewed) paper has been published about these experiments.  Another concern involves the extrapolation of these findings to cryonics. It would go beyond the general nature of this piece to document all the differences between these controlled experiments and cryonics as practiced in the real world, but suffice it to say that the factors of shorter and longer delays, longer  drug administration times, suboptimal “post-ischemia” circulation, and induction of hypothermia introduce many unknowns about the efficacy of these drugs for cryonics patients.  In the case of some medications, like streptokinase, heparin, and dextran 40, a case could be made that the potential benefits outweigh the unknowns, but should this argument be extended to all medications?

Even more complexity is introduced when cryonics organizations make an attempt to wash out the blood and substitute it with a universal organ preservation solution. The rationale for this procedure is found in conventional organ preservation and emergency medicine research. The question in organ preservation research is no longer whether hypothermic organs benefit from blood substitution with a synthetic solution, but what the ideal composition of such a solution should be. In emergency medicine research asanguineous hypothermic circulatory arrest is increasingly being investigated to stabilize trauma victims. But it is a major step from these developments to the practice of remote blood washout of ischemic patients with expected transport times of 24 hours or more. At present the only sure benefit of remote blood washout is that it enables more rapid cooling of the patient, a benefit that should not be underestimated. But when liquid ventilation becomes available to cryonics patients, rapid cooling rates will be possible without extracorporeal circulation.

The lack of relevant published data to support the administration of large numbers of drugs and remote blood washout in cryonics is not just a matter of risking performing redundant procedures. A lot of time and resources are being spent in cryonics on obtaining and maintaining equipment and supplies for these procedures, in addition to the licensing fees paid to use some of these technologies and the training and recruiting of people to perform them. But perhaps the most troublesome problem is that the preparation and execution of these procedures during actual cryonics cases can seriously interfere with rapid and effective cardiopulmonary support and induction of hypothermia.

There is an urgent need to move from extrapolation based cryonics to evidence-based cryonics. This will require a comprehensive research program aimed at creating realistic cryonics research models. It will also require vast improvements in the monitoring and evaluation of cryonics cases.  The current debate should no longer be between advocates and opponents of standby and stabilization but about what stabilization procedures should be used by cryonics organizations given our current knowledge.

Viewing cryonics as an experimental medical procedure does not necessarily commit one to the position that substantial amounts of money and resources should be allocated to recruiting medical professionals and expensive equipment. The most common sense implication of the views outlined above is that the most effective measures to improve the care of cryonics patients are encouraging members to relocate to the area of their cryonics organization, improved health tracking of existing members, and cryonics training aimed at teaching the basic procedures and techniques that confer real evidence-based benefits.

D(+)-Lactose and other sugars in organ preservation and cryonics

A PDF file of this document is available with images and structural visualization of various sugars.

D(+) lactose monohydrate is the principal sugar in mammalian milks. The monohydrate part is easiest to explain; it simply means that the lactose molecule has one water molecule attached to it. This is important because some chemicals can have a lot of water molecules attached to them. For instance, you can have magnesium chloride with two attached water molecules (dihydrate) or six attached water molecules (pentahydrate). This becomes very important when you are weighing out a chemical and you need the chemical to be present in the correct amount. You’ll understand how important this is if you consider that someone proposes to sell you a kilo of some very valuable chemical (say 100 times more valuable than gold per milligram). There is going to be a considerable difference in the amount (by weight and usually by volume) of the actual active chemical you get per milligram or gram (weight) depending upon how hydrated it is (how many water molecules it has attached. The molecular weight (molecular mass) of magnesium chloride is 203.30 and the molecular weight (MW) of water is 18.01. Now, if you have 6 water molecules for each magnesium chloride molecule you have a total mass of water of  (18.01 x 6) = 108.06. That means if you have the pentahydrate salt of magnesium chloride you must add the weight of the 6 water molecules to the MW of magnesium chloride: 203.30 + 108.06 = 311.36. So, if someone is selling you a gram of magnesium chloride pentahydrate at the same price you can buy magnesium chloride anhydrous (no water) you are getting cheated because you are paying the same price for a gram of product that is 1/3rd water!

In biology and chemistry the same principle applies because if you need a certain amount of a chemical for critical reasons, say to maintain normal cell function or inhibit cell swelling in hypothermia, then you must account for any water molecules that may be attached to the chemical. In the case of magnesium chloride pentahydrate versus anhydrous magnesium chloride you are going to have to weigh out about 1/3rd more of the powder of the pentahydrate salt in order to get the same amount of magnesium chloride present in one gram of the anhydrous salt.

Why have pentahydrate, monohydrates, dihydrates and so on of chemicals? The answer is that some chemicals are almost impossible to handle in room air without rapidly absorbing water. Some chemicals will absorb just so much water and no more and thus are very stable under conditions of normal use, so they are supplied in this form. Some chemicals, especially organic chemicals, are virtually impossible to economically produce without one or more attached water molecules. Magnesium chloride is a really good example because it is intensely hygroscopic; it will literally pull water out of the air right before your eyes. So, not only is anhydrous magnesium chloride more expensive than the pentahydrate, it is virtually impossible to handle. If you try to weigh it out it will literally be grabbing water from the ambient air so fast that you can’t tare it on the scale. In seconds you will see tiny droplets of water on the weighing boat or paper where the magnesium chloride has literally pulled so much water out of the air it is fully dissolved in a tiny droplet of water! Calcium chloride is just about as bad, so, you’ll notice that we don’t even bother trying to weigh these chemicals out as dry powders, but rather buy them as pharmaceutical products for injection because they are already dissolved in solution in very precise concentrations. Thus, it is much simpler to draw up the correct volume of these salts dissolved in solution to add the desired amount of these two chemicals to perfusate. It is possible to weigh them, but you have to be quick and it helps if you live the desert where the humidity is very low.

Now we come to the D(+) part which is much harder to explain. In the early part of the 19th Century the French physicist Dominique F.J. Arago noticed that when he passed polarized light through quartz crystals the light could be rotated either to the left or right depending upon the individual crystal. Shortly thereafter the brilliant physicist and mathematician Jean Baptise Biot (the Biot number, a dimensionless number used in unsteady-state (or transient) heat transfer calculations, is named after him) also observed this same effect in liquids and gases of organic substances such as turpentine and some other petroleum products. About 10 years later the English astronomer Sir Joun F.W. Herschel discovered that different crystal forms of quartz rotated the linear polarization in different directions. Simple polarimeters have been used since this time to measure the concentrations of monosaccharide sugars, such as glucose, in solution. In fact, one name for glucose, -dextrose-, is so named because it causes linearly polarized light to rotate to the right or “dexter” side. Similarly, levulose, more commonly known as fructose (fruit sugar) causes the plane of polarization to rotate to the left. Fructose is even more strongly levorotatory than glucose is dextrorotatory. Invert sugar which is formed by adding fructose to a solution of glucose, gets its name from the fact that subsequent structural conversion causes the direction of rotation to “invert” from right to left.

The reason for this behaviour of these seemingly identical substances was not understood until the mid-19th Century when Pasteur was working on the problem of why wine was souring as opposed to fermenting into an alcohol solution. The culprit was yeast that metabolized the fructose in the grape juice to tartaric acid. A solution of tartaric acid derived from living things (the wine lees yeasts) rotated the plane of polarization of light passing through it, whereas chemically synthesized tartaric acid prepared by non-organic means in the laboratory did not have this effect. This was puzzling because both the synthetic and the biologically derived tartaric acid undergo the same chemical reactions and are identical in their elemental (atomic) composition. Pasteur noticed that the crystals came in two asymmetric forms that were mirror images of one another. He meticulously sorted the crystals by hand and then dissolved each of the two forms of crystals in water; solutions of one form rotated polarized light clockwise, while the other form rotated light counter-clockwise. An equal mix of the two had no polarizing effect on light. Pasteur deduced the molecule tartaric acid molecule was asymmetric and could exist in two different forms that resemble one another; as would left- and right-hand gloves, and that the organic form of the compound consisted purely of the one type.

This phenomenon is referred to as isomerism and occurs when two molecules have the same molecular formula (atomic composition) yet have different structures and therefore different chemical and physical properties. There are many different kinds of isomers. The two major divisions of isomers are the geometric and the structural. Structural isomers are isomers that have the same number of atoms but different arrangement of atoms. One structural isomer of glucose is fructose. Geometric isomers are identical in arrangement of covalent bonds but are different in the order that the groups are arranged.

A major category is stereoisomers which are two isomers that have the number of atoms in the same order. A stereoisomer of glucose is galactose. In the Fischer projection all of the atoms are the same except for one rotated group. There are two categories of stereoisomers, enantiomers and diastereomers. Enantiomers are two isomers that are mirror images of each other when looked at in 3D while diastereomers are not. Galactose is just one of many diastereomers of glucose. To find out the possible number of stereoisomer forms a monosaccharide can have, you can use the formula 2x where x is the number of chiral carbons the molecule has. Molecular chirality occurs when a sugar has a carbon with four different groups attached to it. Any carbon with a double bond on it is never chiral nor are the end carbons. Because glucose has four chiral carbons there are 24 different stereoisomers; which means that there are sixteen different stereoisomers for glucose.

Two of the main divisions of glucose’s many forms are l-glucose and d-glucose. These two are enantiomers which are determined by whether the two molecules are symmetrical at the last chiral carbon. When the hydroxyl group is on the last chiral carbon on the right it is considered d-glucose  and when it is on the left it is classified as l-glucose. The “d” means that the glucose rotates polarized light to the right (dextrorotatory) and the “l” stands for  levorotary (rotates polarized light to the left). These refer to how a plane of light rotates as it passes through a solution of it. First light is passed through a polarizing filter, then a polarimeter containing a solution made with the molecule. When a d-solution is in the polarimeter it will cause the light to turn to the right or at positive angle, while an l-solution will cause the light to turn to the left or a negative angle. Both d-glucose and l-glucose exist naturally but d-glucose, also called dextrose, is the most abundant sugar on the planet.

The practical biological and chemical implications of these isomeric structural differences is profound. D-glucose (dextrose) is the principal sugar used by the body to generate energy. By contrast, l-glucose cannot be significantly metabolized and an animal or human would starve to death if this was the only carbohydrate available in its diet and no other sources of energy (fats or proteins) were available. L-glucose looks, tastes and has the same mouth feel as d-glucose and there has been considerable interest in producing it in large quantities as an artificial sweetener.  Unfortunately, the synthetic pathway to produce l-glucose, and more importantly, the separation of the d- and l-glucose isomers after synthesis is currently prohibitively expensive.

What does all this have to with cryonics and organ preservation? Under normal metabolic conditions the cells of the body produce chemical energy in the form of ATP and about 1/3rd of this energy is used to pump ions into and out of the cells. This is necessary because the most common salts (ions) are very small and can easily pass through the cell membranes. Two straightforward examples are very much on-point. Cells need high concentrations of the potassium ion inside them to be able to function properly including carrying out some vital chemical reactions and doing things like contracting in the case of muscles or transmitting signals in the case of nerve cells. Conversely, cells must not have too much sodium in them or they  become swollen (edematous) and while this can ultimately rupture or lyse the cell, long before this happens cell swelling disrupts the meshwork of supports that maintain the cell’s shape and probably serve as scaffolding for various enzymes to be anchored on and to facilitate efficient chemical processing (metabolism). Unfortunately, sodium has a net negative charge and the protein inside cells has a net positive charge. Thus, sodium will flow into cells and carry water with it resulting in cellular edema. This process is prevented by active pumping of sodium out of the cell. Similarly, calcium is extremely toxic to cellular mitochondria in high concentrations and calcium is also used as a critical signalling molecule inside cells. Thus, the calcium concentration outside cells is typically 10,000 times higher than that present inside cells. Again, this difference in concentration is maintained largely by active pumping which requires energy expenditure and on-going metabolism.

So, sodium gets pumped out and potassium gets pumped in and this process is linked and carried out by the same molecular machine; the sodium-potassium pump. Of course, all of this presumes that there is both available energy in the form of ATP and that the cellular pumping machinery can use that energy. There are a number of things that can interrupt ion pumping. There can be a lack of energy due to starvation, hypoxia or ischemia, and there can exist situations where the energy is available but cannot be used. Some chemicals poison enzymes critical to ion pumping; a classic example is tetrodotoxin which comes from blowfish and which poisons sodium pumping. The other condition where adequate energy (ATP) can exist but cannot be used is deep hypothermia. Non-hibernating animals have enzymes that shut down or become inactive when the temperature is reduced well below that of normal body temperature. In humans (and most non-hibernating mammals) the  enzyme responsible for pumping sodium out of cells and potassium into them, sodium-potassium-ATPase, is largely inhibited at 10oC and is virtually shut down at few degrees above 0 oC.

Cell swelling in brain cells occurs with incredible rapidity after interruption of blood flow in ischemia (cardiac arrest). While cell swelling is not the only, or even primary, cause of injury in cerebral ischemia, it is a major player in causing injury in cold ischemia; conditions which obviously obtain in organ preservation and ultra-profound hypothermia in cryonics patients. The way this edema is prevented in organ preservation is to replace almost all of the small cell membrane permeable ions with big molecules that cannot pass through the cell membrane and which are osmotically active; in others words can hold water outside of the cell.  The first solution to do this with any success was Collin’s Solution invented by Geoff Collins. It used comparatively large phosphate salts to keep water outside of the cells and prevent cellular edema. However, phosphates do leak across the cell membrane and they are incompatible with DMSO and also precipitate as crystals when solutions are cooled to low temperatures or frozen.

Thus, the organ preservationists turned to sugars and sugar alcohols as molecules to serve as an osmotic agent and prevent cell swelling. Sugars are comparatively large molecules and some are very large. They do not typically pass through cell membranes rapidly, if at all. Some of the first sugars tried were glucose and sucrose and the sugar-alcohol mannitol. Neither glucose nor sucrose worked well. Glucose leaks across cell membranes fairly rapidly and has facilitated transport in the brain. Sucrose makes quite viscous solutions in the necessary concentrations (~180 mM) and for unknown reasons is toxic to the kidney tubule cells. Mannitol was much more successful in the laboratory but never made it into clinical organ preservation solutions.

In the 1980s, a biochemist named Jim Southard and a transplant surgeon named Folkert Belzer began to systematically study molecules to inhibit cold ischemic swelling, as well as other molecules to help conserve ATP, inhibit free radical damage, and otherwise address the derangements that occur under deep hypothermic conditions. They identified two sugars as particularly effective in inhibiting cold ischemic cellular edema, raffinose and lactobionate. They combined these two sugars along with other ingredients to create the first and still most successful “universal” organ preservation solution, UW-Solution, or as it is commercially marketed, Viaspan.

Unfortunately, ViaSpan does not work for the brain. We tried it extensively in the early 1990s and got serious cerebral edema followed by convulsions and death in dogs that had been perfused with ViaSpan for as little as two hours! By contrast, we could recover dogs perfused with MHP (a mannitol based perfusate) after 5-hours of bloodless perfusion with the solution at  5oC with no neurological or other problems; most of the dogs were placed with cryonics members and lived out the rest of their lives normally.

Recently, 21st Century Medicine has been systematically investigating hypothermic organ preservation and they have made a number of stunning breakthroughs. One thing which was long overdue to be done was to systematically screen various molecules for their cell swelling inhibiting effects. They found that one sugar in particular was highly effective, D(+)-lactose. Only the d-isomer worked well.

Why some sugars work and others do not, or actually cause harm, is a mystery. The molecular weight is certainly a factor, but different sugars with nearly identical molecular weights may perform totally differently. Also, the isomer of the sugar appears critical in some cases, as is the situation with lactose.  21st Century Medicine has patented an organ preservation based on D(+)-lactose and is in Phase II clinical trials for this solution, which they call TranSend. They are currently getting 72-hour simple flush and store on ice preservation of kidneys (rabbit and dog), pancreases and livers (dogs) and are getting similar results in the human clinical trials. They have achieved 48-hour heart preservation using a derivative of this solution which combines periods of trickle-flow cold perfusion with brief intervals of modest warming to ~15 oC.

Polyethylene glycol and cryonics

The blog Al Fin reports on polyethylene glycol (PEG) as an acute treatment for traumatic brain and spinal cord injury. PEG is hypothesized to confer cytoprotection by sealing damaged cell membranes. As such, PEG would also seem a promising candidate for the treatment of acute neural insults in which progressive cell permeability / damage plays a part such as stroke and cardiac arrest. Unfortunately, the inability of high molecular weight polymers to cross an intact blood brain barrier (BBB) may limit the use of PEG as a treatment for cerebral ischemia. One study that investigated PEG in a model of middle cerebral artery occlusion (MCAo) did not find any benefits for PEG. In cryonics, membrane sealing polymers like PEG may still be useful because they can cross the compromised BBB and prevent cell lysis when transport of the patient is delayed. Its membrane sealing properties may also be useful for extending the time cryonics patients can be perfused without causing edema.

As a high molecular weight polymer, PEG has also been investigated as a component for cold organ preservation solutions. A number of studies have found that PEG can be substituted for  hydroxyethyl starch (HES) as the oncotic agent in University of Wisconsin solution (commercial name: Viaspan). Replacing HES with PEG in UW solution also decreases red blood cell aggregation and viscoscity.

PEG is also briefly discussed by Mike Perry as an embedding medium in his article about low-cost alternatives to cryonics.

Remote blood washout in cryonics

One argument that is often raised in favor of “field vitrification” (or vehicle based vitrification) is that it will reduce the time of (cold) ischemia and eliminate the harmful effects of remote blood washout and transport of a patient on water ice to a cryonics facility. A related argument is that field vitrification will eliminate stabilization.

In fact, field vitrification will not eliminate the need for stabilization because patients need to be protected from warm ischemic injury after cardiac arrest until a location to carry out cryoprotectant perfusion has been secured and surgical access to the patient’s vessels has been established (a procedure that, in cryonics, takes at least fifteen minutes under the best of circumstances). During that period the patient will still require prompt cardiopulmonary support, induction of hypothermia, and administration of anticoagulants and neuroprotective agents. As a consequence, stabilization times should not differ between field vitrification or remote blood washout. In light of the possibility that field vitrification will likely require more demanding and time-consuming surgery, field vitrification might even necessitate longer stabilization times. The only procedure that could reduce or eliminate stabilization would be hospital-based vitrification.

Field vitrification will reduce the period between cardiac arrest and the start of cryoprotective perfusion. But whether this is a clear advantage or not depends on the question of whether remote blood washout and transport on water ice introduces additional injury to the patient. Recent anecdotal observations of cryoprotective perfusion of patients who have been washed out in the field indicate that the procedure of blood washout itself may be harmful. It is not clear, however, whether this is an intrinsic element of remote blood washout and cold transport or the result of poor perfusion techniques and flawed composition of the organ preservation solutions that are used to replace the blood.

In cryonics, remote blood washout is done for at least three reasons: (1) to eliminate the possibility of blood clotting and hypothermia-induced red cell membrane rigidity, rouleaux formation, and cold agglutination; (2) to remove ischemia-induced inflammatory products and endotoxins from the circulation; and (3) to protect the patient from hypothermia-induced cell injury and edema by substituting the blood with an organ preservation solution.

The organ preservation solution used today is called MHP-2. The original MHP solution is a modification of RPS-2 (an organ preservation solution for hypothermic kidney preservation created by Greg Fahy at the American Red Cross) and stands for Mannitol-Hepes-Perfusate. It is designed as a so called “intracellular” organ transplant solution. In order to reduce passive ion exchange as a result of hypothermia-induced cell membrane pump inhibition, its composition more closely resembles the composition of the solution inside the cell rather than the interstitial fluid or blood plasma. MHP also contains molecules to provide oncotic support, prevent acidosis, and reduce free radical damage. In a series of groundbreaking experiments by Jerry Leaf and Michael Darwin, MHP was successful in resuscitating dogs from up to 5 hours of asanguineous ultraprofound hypothermia. MHP-2 is a modification of MHP that is believed to produce superior results.

A number of arguments have been put forward why remote blood substitution with MHP-2 is not successful in securing viability of the brain during transport, and may even produce adverse effects. The most obvious reason is that MHP has been validated for up to 5 hours of ultraprofound hypothermia, which is not the typical transport time of a cryonics patient. A related problem is that MHP has not been validated in a model that reflects the typical cryonics patient who experiences variable periods of hypoperfusion and warm ischemia prior to and after cardiac arrest. And, unlike the canine asanguineous ultraprofound hypothermia experiments, in cryonics MHP is used as static cold preservation solution instead of being continuously perfused at low flow rates. Although MHP can reportedly recover dogs from up to 3 hours of asanguineous circulatory arrest (clinical death), such a protocol further reduces the time that viability of the brain can be maintained during transport.

Although the MHP patent and the notebooks from the original washout experiments are clear that MHP should be prepared as a hyper-osmolar perfusate (~ 400 mOsm), it has been established that in recent years many batches of MHP have not been mixed with hyper-osmolality as an endpoint, due to a lack of osmometry quality controls. The exact effects of this are unknown but have been hypothesized to explain why recent remote blood washout has produced worse results than in the past, possibly by aggravating, or in the case of a hypo-osmolar perfusate, producing edema. This problem, and the confusion about the exact composition of MHP-2, is briefly discussed in the Suspended Animation case report of Cryonics Institute patient CI-81.

Field vitrification is not the only solution to the limitations of remote blood washout and transport on water ice. Another solution would be to improve the composition of hypothermic organ preservation solutions and perfusion protocols to secure extended periods of cerebral viability during transport. Instead of substituting the patient’s blood with an organ preservation solution, after which the patient is shipped on water ice, the organ preservation solution can be continuously (or intermittently) perfused at low flow rates, similar to machine perfusion in conventional organ preservation, while the patient is being driven in a rescue vehicle to a cryonics facility. This has a number of advantages, including the possibility to sustain aerobic metabolism, improve microcirculation and administer cytoprotective agents.

Although cerebral viability of the brain may be extended by improved organ preservation solutions, there seems to be a fundamental limit to shipping patients in hypothermic circulatory arrest because the remaining energy demands of the brain will need to be satisfied by oxidative phosphorylation (or other energy substrates) at some point. Although it is not known how far these limits can be pushed by static use of organ preservation solutions, it is likely that a protocol of continued hypothermic perfusion of remote cryonics patients will exceed these limits. Like field vitrification, such a protocol will present non-trivial technical and logistical challenges.

This still leaves the question of whether remote blood washout can aggravate injury in ischemic patients unanswered. Since the original canine experiments investigated MHP in healthy animals we do not know if some patients would be better off without a blood washout. Dr. Southard, one of the inventors of Viaspan (also called the University of Wisconsin solution in the scientific literature), discussed similar concerns in a recent interview:

“In clinical organ preservation/transplantation, there are many unexplained incidents of reperfusion injury. This is characterized by delayed graft function in the liver and kidney. We do not see this in our animal models. Thus, there are some differences between how experimental animals and human donor organs respond to organ preservation. The difference may be related to the fact that the UW solution was developed to preserve the “ideal organ.” This is one taken from a relatively young and healthy lab animal donor and transplanted into a healthy recipient. In the clinics, the donors are usually brain-dead (brain trauma), remain in the ICU for periods up to a day or more, are treated for hypotension, and come from an uncontrolled group of donors. Therefore, we are now studying how UW solution preserves organs from the “less-than-ideal” donor. We are simulating the clinical condition by inducing warm ischemia or brain death in experimental animals to determine if UW solution is suitable for these types of organs. If not, we will develop an ideal method to preserve these less-than-ideal donor organs.” (quoted on the old Viaspan website).

Similarly, organ preservation solutions used in cryonics need to be investigated in models that better reflect the typical pre-mortem pathophysiology and post-mortem procedures encountered in cryonics. Developing stabilization technologies and procedures for “less than ideal patients” is an important element in an approach known as “Evidence Based Cryonics.”