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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 25:1816-1820, November-December 2004
© 2004 American Society of Neuroradiology

SPINE

Magnetization Transfer Micro-MR Imaging of Live Excised Lamprey Spinal Cord: Characterization and Immunohistochemical Correlation

Hidemasa Uematsu^a, Andra Popescu^b, Guixin Zhang^c, Alexander C. Wright^b, Suzanne L. Wehrli^d, Masaya Takahashi^e, Felix. W. Wehrli^b, Michael E. Selzer^c and David B. Hackney^e

^a Department of Radiology, University of Fukui, Japan
^b Department of Radiology, University of Pennsylvania, Philadelphia
^c Department of Neurology, University of Pennsylvania, Philadelphia
^d NMR Core Facility, Children’s Hospital of Philadelphia, PA
^e Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA

Address reprint requests to Hidemasa Uematsu, MD, PhD, Department of Radiology, University of Fukui, 23 Shimoaizuki, Matsuoka-cho, Yoshida-gun, Fukui, 910-1193, Japan

BACKGROUND AND PURPOSE: Membrane constituents may play a key role in the magnetization transfer (MT) effect. In lamprey spinal cord, axonal diameters range from <1 µm in the dorsal region to 20–40 µm in the ventral region. There is a corresponding range of axonal, and hence cell membrane, density. These characteristics permit determination of the effect of cell membrane density on MT. The purpose of this study was to characterize regional MT effects in lamprey spinal cord.

METHODS: Excised spinal cords from eight sea lampreys were measured with a 9.4-T MR imaging system. MT saturation was applied for spin-echo sequences. The MT ratio (MTR) was calculated in each location (dorsal, lateral, and ventral columns). Spinal cords from five other lampreys were prepared with an antibody to lamprey glial keratin (LCM 29). The percentage of area staining with LCM29 was calculated for each location.

RESULTS: Mean MTR (± SD) for the dorsal, lateral, and ventral columns were 62.4 ± 4.2, 59.2 ± 2.7, and 56.9 ± 3.0, respectively; all differences were significant (P < .05). Mean LCM29-positive areas for the dorsal, lateral, and ventral columns were 85.1%, 69.7%, and 50.9%, respectively. MTR and percentage LCM29-positive area were significantly correlated (r² = 0.98).

CONCLUSION: Regional differences in MT effect exist in the lamprey spinal cord. MTR is well correlated with percentage LCM29-positive area. These results support the hypothesis that membrane constituents are at least partly responsible for regional variations in MT effect.