title: Effects of hypotonic stress and ouabain on the apparent diffusion coefficient of water at cellular and tissue levels in Aplysia.
abstract: There is evidence that physiological or pathological cell swelling is associated with a decrease of the apparent diffusion coefficient (ADC) of water in tissues, as measured with MRI. However the mechanism remains unclear. Magnetic resonance microscopy, performed on small tissue samples, has the potential to distinguish effects occurring at cellular and tissue levels. A three-dimensional diffusion prepared fast imaging with steady-state free precession sequence for MR microscopy was implemented on a 17.2 T imaging system and used to investigate the effect of two biological challenges known to cause cell swelling, exposure to a hypotonic solution or to ouabain, on Aplysia nervous tissue. The ADC was measured inside isolated neuronal soma and in the region of cell bodies of the buccal ganglia. Both challenges resulted in an ADC increase inside isolated neuronal soma (+31 ± 24% and +30 ± 11%, respectively) and an ADC decrease at tissue level in the buccal ganglia (-12 ± 5% and -18 ± 8%, respectively). A scenario involving a layer of water molecules bound to the inflating cell membrane surface is proposed to reconcile this apparent discrepancy.
authors.affiliation: NeuroSpin, Commissariat à l'Energie Atomique et aux Energies Alternatives, Gif-sur-Yvette, France.
authors.forename: Ileana Ozana
authors.initials: IO
authors.lastname: Jelescu
authors.forename: Luisa
authors.initials: L
authors.lastname: Ciobanu
authors.forename: Françoise
authors.initials: F
authors.lastname: Geffroy
authors.forename: Pierre
authors.initials: P
authors.lastname: Marquet
authors.forename: Denis
authors.initials: D
authors.lastname: Le Bihan
mesh_terms: D000818:Animals; D001048:Aplysia / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004058:Diffusion; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D006696:Holography; D008279:Magnetic Resonance Imaging; D009928:Organ Specificity / Q000187:drug effects*; D009997:Osmotic Pressure; D010042:Ouabain / Q000494:pharmacology*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D010042:Ouabain
keywords: Aplysia; biophysical mechanisms of MR diffusion; cell swelling; cellular and molecular CNS imaging; digital holographic microscopy; microscopy