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NMR imaging and spectroscopy in cyrobiology Isbell, Stephanie A.


Microscopic Chemical Shift Specific Slice Selective (C45) NMR imaging is demonstrated to be a nondestructive and noninvasive technique for monitoring the spatial distributions of solvents and of freezing/thawing phenomena. Studies of test samples show that the C4S NMR imaging sequence can yield quantitative maps of distributions of water., and dimethyl sulfoxide (DMSO). The unique characteristics of C4S NMR imaging are potentially very useful in studies of organ cryopreservation in which cryoprotective solvents (CPSs) like DMSO successfully prevent freezing damage to cells in suspension but presently cannot be used to preserve whole organs at subzero temperatures. There are no other techniques available which are capable of monitoring CPS and water concentration distributions as well as structural changes in organs during cryopreservation procedures. C4S NMR imaging is shown to be useful for monitoring the diffusion of the cryoprotectant DMSO into rat kidney and liver tissues. A detailed investigation of the possibility of mapping concentration distributions of DMSO and water at various temperatures using images with short repetition times verifies that DMSO and water in tissues can be quantified from image signal intensities within certain concentration ranges. Diffusion rates are easily obtained from the imaging data and are similar to those found in the literature. A simple method for determination of effective diffusion coefficients of DMSO in tissues is developed and shown to be more accurate and unambiguous than the commonly used chemical techniques. Aspects of the introduction of DMSO to rat kidney by perfusion through the vasculature are studied. C4S NMR imaging is applied to two common blood removal techniques and is shown to detect blood remaining in the vasculature after these washout procedures. A new method of completely removing blood from rat kidneys is shown to be more effective. Complete blood removal is demonstrated to be essential for homogeneous equilibration of tissues with a cryoprotective solution. Blood clots preventing the equilibration of DMSO in a kidney indirectly cause severe freezing damage. Equilibration of DMSO with rat kidney via perfusion with DMSO in University of Wisconsin (OW) solution is shown to cause minimal damage and proceed most quickly at 20°C. 3P1 NMR spectroscopy is performed on rat kidneys subjected to the new blood washout procedure and the relationship of the spectra to organ viability is discussed.

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