title: MRI of Retinal Free Radical Production With Laminar Resolution In Vivo.
abstract: OBJECTIVE
  Recent studies have suggested the hypothesis that quench-assisted 1/T1 magnetic resonance imaging (MRI) measures free radical production with laminar resolution in vivo without the need of a contrast agent. Here, we test this hypothesis further by examining the spatial and detection sensitivity of quench-assisted 1/T1 MRI to strain, age, or retinal cell layer-specific genetic manipulations.
  
  
  METHODS
  We studied: adult wild-type mice; mice at postnatal day 7 (P7); cre dependent retinal pigment epithelium (RPE)-specific MnSOD knockout mice; doxycycline-treated Sod2f(lox/flox) mice lacking the cre transgene; and α-transducin knockout (Gnat1(-/-)) mice on a C57Bl/6 background. Transretinal 1/T1 profiles were mapped in vivo in the dark without or with antioxidant treatment, or followed by light exposure. We calibrated profiles spatially using optical coherence tomography.
  
  
  RESULTS
  Dark-adapted RPE-specific MnSOD knockout mice had greater than normal 1/T1 in the RPE and outer nuclear layers that was corrected to wild-type levels by antioxidant treatment. Dark and light Gnat1(-/-) mice also had greater than normal outer retinal 1/T1 values. In adult wild-type mice, dark values of 1/T1 in the ellipsoid region and in the outer segment were suppressed by 13 minutes of light. By 29 minutes of light, 1/T1 reduction extended to the outer nuclear layer. Gnat1(-/-) mice demonstrated a faster light-evoked suppression of 1/T1 values in the outer retina. In P7 mice, transretinal 1/T1 profiles were the same in dark and light.
  
  
  CONCLUSIONS
  Quench-assisted MRI has the laminar resolution and detection sensitivity to evaluate normal and pathologic production of free radicals in vivo.
authors.affiliation: Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States 2Department of Ophthalmology, Wayne State University School of Medicine, Detroit, Michigan, United States.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Berkowitz
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States.
authors.forename: Alfred S
authors.initials: AS
authors.lastname: Lewin
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States.
authors.forename: Manas R
authors.initials: MR
authors.lastname: Biswal
authors.affiliation: Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States.
authors.forename: Bryce X
authors.initials: BX
authors.lastname: Bredell
authors.affiliation: Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States.
authors.forename: Christopher
authors.initials: C
authors.lastname: Davis
authors.affiliation: Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States.
authors.forename: Robin
authors.initials: R
authors.lastname: Roberts
mesh_terms: D000818:Animals; D003623:Dark Adaptation / Q000502:physiology*; D005260:Female; D016166:Free Radical Scavengers / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018384:Oxidative Stress / Q000502:physiology*; D012160:Retina / Q000166:cytology* / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000378:metabolism; D041623:Tomography, Optical Coherence
chemical_list: D016166:Free Radical Scavengers