X-Message-Number: 4983 Date: 13 Oct 95 18:38:53 EDT From: Mike Darwin <> Subject: CRYONICS:what goes there? Joe Strout writes: >>>We are witnessing the gestation of a myth here on Cryonet, probably fathered by Mike Darwin but carried by most of the list, which I will attempt to abort before it gets too big. Straight freeze, despite appearances, is NOT the same thing as a tissue homogenate. A homogenate is made by placing tissue in a blender, which has two effects: 1. parts are physically disconnected from their neighbors 2. the relative location of each part is essentially randomized (Note on #2: not really randomized, of course, but each part takes a chaotic path -- see physics of mixing.) It is especially this second effect which makes reconstruction nearly impossible, even in principle. A straight freeze, on the other hand, causes only effect #1, but not effect #2 since each "part" (disconnected bit of tissue) is locked firmly in place by the ice around it. Position is preserved, and probably orientation as well. A simple analogy should serve to illustrate the difference. Imagine a large, completed jigsaw puzzle. For a homogenate, take the puzzle apart, put the pieces back in the box, shake well, and then lay the pieces out again (in random order) flat on the table. For a straight freeze, take the puzzle apart carefully, and put each piece back right where you found it (spreading them out or overlapping a bit). If you stand back a bit and squint -- or turn the pieces over so you can't see the big picture -- then these two cases look very similar. This is, in fact, how it appears to the electron microscopist. But when you actually sit down and start putting the puzzle back together, it is obvious that the first case is difficult, while the second is trivial. Now. I'm not actually suggesting that straight freeze be offered as anything but an emergency option -- a last-resort variation on what's already a last-resort procedure. But it's not useless either, as the "hamburger" camp would have you believe.>> I was quite careful to point out in my "blender=homogenate" remarks exactly the points Joe makes. The critical question is WHAT IS LEFT IN THE FROZEN STATE???!! Here, I pointed out that it is hard to know, because when we look for structure with freeze substitution we see everything is squashed down or dehydrated into dense, narrow channels. If Joe will recall, I asked him about freeze fracture capabilities sometime ago, but not much came from the help he (Joe) tried to supply (BTW thanks for the refferrals, Joe!). Lots of freeze fracture on straight frozen tissue would help to answer this question. My using the blender experiment was to point up (somewhat whimsically) that AFTER THAWING the results LOOK the same at the SAME level of examination. This point may well be lost on people not conversant with the science involved here, as both Joe and I are, and I am grateful to Joe for pointing out the differences and clarifying points. Now, having said all this I must take issue with Joe's remarks about what goes on during freezing (particularly straight freezing). Joe says: >A simple analogy should serve to illustrate the difference. Imagine a >large, completed jigsaw puzzle. For a homogenate, take the puzzle apart, >put the pieces back in the box, shake well, and then lay the pieces out >again (in random order) flat on the table. For a straight freeze, take >the puzzle apart carefully, and put each piece back right where you found >it (spreading them out or overlapping a bit). >If you stand back a bit and squint -- or turn the pieces over so you >can't see the big picture -- then these two cases look very similar. >This is, in fact, how it appears to the electron microscopist. But when >you actually sit down and start putting the puzzle back together, it is >obvious that the first case is difficult, while the second is trivial. This is only partly true. This is also the same kind of argument (and I believe mistake) that nonbiologists like Merkle, Drexler and others make. Here I specfically exclude Donaldson who understands what I am about to say quite well. Here too I will have recourse to an analogy. Since the time of Leonardo through Harvey, John Hunter and to almost present times biology has been increasingly viewed and modeled from the perspective of "engineering", of looking at living systems as machines. This is fine and has done much good, in part by banishing vitalism and opening up investigation of living systems to investigation using the the same scientific approach that is used in all other areas of science and technology. I call this phase in biology (and medicine to a lesser extent) the "Newtonian Phase." The Newtonian guys view of living systems is like bridges, automobiles, newsprint, clocks, integrated circuits, etc. This is not a useless way to view these things; it is very useful and has resulted in great advances in understing. However, it is, in short, a necessary but NOT sufficient model of living systems. It is not sufficient because it breaks down, much like Newtonian mechanics does as you drop down in scale. If you put a wrist-watch in a vice and squeeze it tight, or you have a bridge fall down in an earthquake you get the kind of situation Joe describes and that Merkle preaches. But cells and tissues are NOT made of up of those kind of of parts. If you stress a bridge to the point that it falls apart, the pieces don't fall into the canyon or river, reassemmble themselves in "amorphous" bubbles and float away. Indeed, no pieces undergo reorginzation such that an I-beam turns into a steel tube with rivets from a neaby or distant joint now studded into its walls. Similarly, cables snapped from stress don't attach themselves to other cables, or change shape into sheets. When we watch cells being frozen under a cryomicroscope we see incredible things. We see blebs of membrane material being budded off under osmotic stress, we see great turbulence as ice grows and vast (on a nanometer scale) flow of water out of cells as ice fronts move forward. A good analogy here would be glaciation where we see things like mineral markers for the presence of diamonds moved hundred or thousands of miles from the volcanic tubes (where the diamonds really are) by ice. We know when we freeze cells, even with cryoprotectant, that surface antigens and bits of membrane material are exuded or "extruded (?)". In fact, even the high glyc (6M glycerol) freezing technique for red cells yeilds cells that have fewer surface antigens than cells that are comparably loaded with CPA and washed clean of it. (Just glycing and deglycing DOES cause some antigen loss). When you freeze living systems you do not JUST get a collapsed bridge or a distorted puzzle. You get mechanisms coming into play which are very different. You get BIOCHEMISTRY and self assembly, and all sorts of phenomenon that are NOT like the molecular bearing designs in NANOSYSTEMS. What you get is biology. What you get is the physics equivalent of the transition from Newtonian to Quantum Mechanical environments. It is no accident that this has been lost on most cryonicists because most of them (no accident here!) are computer people or engineers, very few biologists, fewer still biologists who have an intimate understanding of how cells do the magic they do. And we know its magic not in the DNA. I doubt whether you could fit the volume of DNA required to specify the PRECISE position of every atom in the human body into the volume of that human body. I rest assured here that Merkle or someone else will soon have an exact volme, bit number, and estimate of input/readout equipment volme, calculated in no time at all :). This example is relevant because it points out that living systems operate like capitalist economies; using self order, chaos, and a host of other poorly understood but LOCAL processes to carry on their fabrication and repair. Donalson, Fahy, and I (I think I speak broadly for these others, and they can correct me if I'm wrong) do not look at molecular and cell-level biology from the top down, engineering specified, planned economy perspective of the big N nanotechnologists. A corollary of this world-view is that when you view systems from our perspective, you find yourself in a land with contours and possibilities as removed from each other as West Berlin was from East, or Newton from Plank, Einstein and Heisenberg. Joe and others should give some thought to this. Mike Darwin Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4983