X-Message-Number: 5008 Date: Tue, 17 Oct 1995 09:36:58 -0700 (PDT) From: Joseph Strout <> Subject: tissue-degeneration model In scuba diving, it is important to keep track of the amount of nitrogen which diffuses into your tissues, because this nitrogen will be released when the pressure decreases, and if released too fast, could cause bubbles in the blood (affectionately dubbed "the bends"). This used to be done with tables compiled empirically, but lately, they've developed "dive computers" which contain a relatively simple model of various tissues and track the nitrogen concentrations over time. This allows a diver to have a more accurate picture of his or her body's state, diving longer and more safely. It occurs to me that a similar model for brain tissue state would be very useful. Every case is different; different conditions of ischemia, fixation, temperatures, etc. Moreover, to extrapolate cryomicroscopy results from small tissue samples to entire brains, we need estimates of how each effect scales with tissue thickness and time. (And, more importantly, we need to APPLY these estimates, so that we don't blindly suggest that what works for a 1-mm tissue slice will work for an entire brain). Such a model would certainly not replace experience and good judgement, but it could serve as a valuable aid. Each patient's condition and treatment would be entered into the model, giving a picture of the state of his/her brain tissue at varying depths from the outside or from the vasculature. Alternative treatments could then be "tried" first on the model, to see the effect on a variety of measures. As treatments are applied, the model would be updated at each step, and the suspension team leader would glance at it now and then to make sure they hadn't overlooked any side-effects or whatever. As new treatments (e.g., microwave fixation) are developed in cryobiology or microscopy, these could be entered into the model. We could then have much more productive discussion about alternatives. The model would also make it painfully clear where more research is needed. Difficult? Certainly, but probably not impossible. The "state" of the tissue (our real interest) could be measured along several independent dimensions, such as: - mobility or viscosity (how "hard" or "soft" is it?) - synapse/spine degeneration - cell membrane integrity - dislocation (i.e., how far has a "part" moved from its proper position) Inputs would all be functions of time, and would include: - perfusion solution (constituents) - application method (external, vascular, other?) - temperature Even if such a model never proves good enough for clinical use, building it might serve to focus attention on important issues and effects. What do you think? ,------------------------------------------------------------------. | Joseph J. Strout Department of Neuroscience, UCSD | | http://www-acs.ucsd.edu/~jstrout/ | `------------------------------------------------------------------' Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5008