title: Apparent diffusion coefficient and MR relaxation during osmotic manipulation in isolated turtle cerebellum.
abstract: The apparent diffusion coefficient (ADC) and relaxation times of water were measured by magnetic resonance imaging (MRI) in the isolated turtle cerebellum during osmotic cell volume manipulation. The aim was to study effects of cell volume changes, a factor in ischemia and spreading depression, in isolation from considerations of blood flow and metabolism. Cerebella were superfused at 12-14 degrees C with solutions ranging from 50-200% normal osmolarity. Hypotonic solutions, which are known to cause cell swelling, led to reductions of ADC and increases of T(2), while hypertonic solutions had the opposite effect. This supports the concept that ADC varies with the extracellular space fraction and, combined with published data on extracellular ion diffusion, is consistent with fast or slow exchange models with effective diffusion coefficients that are approximately 1.7 times lower in intracellular than in extracellular space. Spin-spin relaxation can be affected by osmotic disturbance, though such changes are not seen in all pathologies that cause cell swelling.
authors.affiliation: Royal College of Surgeons Unit of Biophysics, Institute of Child Health, University College London, London, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: O'Shea
authors.forename: S R
authors.initials: SR
authors.lastname: Williams
authors.forename: N
authors.initials: N
authors.lastname: van Bruggen
authors.forename: A R
authors.initials: AR
authors.lastname: Gardner-Medwin
mesh_terms: D000818:Animals; D016880:Anisotropy; D048429:Cell Size / Q000187:drug effects; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism*; D004058:Diffusion; D005110:Extracellular Space / Q000378:metabolism; D006982:Hypertonic Solutions / Q000494:pharmacology; D007038:Hypotonic Solutions / Q000494:pharmacology; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D009994:Osmolar Concentration; D010477:Perfusion; D014426:Turtles; D014867:Water / Q000378:metabolism
chemical_list: D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D014867:Water