MR microscopy of multicomponent diffusion in single neurons

This study examines multicomponent diffusion in isolated single neurons and discusses the implications of the results for macroscopic water diffusion in tissues. L7 Aplysia neurons were isolated and analyzed using a 600 MHz B ruker wide-bore instrument with a magnetic susceptibility-matched radiofreq uency microcoil. Using a biexponential fit, the apparent diffusion coeffici ents (ADCs) from the cytoplasm (with relative fraction) were 0.48 +/- 0.14 x 10(-3) mm(2)S(-1) (61 +/- 11%) for the fast component, and 0.034 +/- 0.01 7 x 10(-3) mm(2)s(-1) (32 +/- 11 %) for the slow component (N = 10). Diffus ion in the nucleus appears to be primarily monoexponential, but with biexpo nential analysis it yields 1.31 +/- 0.32 x 10(-3) mm(2)s(-1) (89 +/- 6%) fo r the fast component and 0.057 +/- 0.073 x 10(-3) mm(2)s(-1) (11 +/- 6%) fo r the slow (N = 5). The slow component in the nucleus may be explained by c ytoplasmic volume averaging. These data demonstrate that water diffusion in the cytoplasm of isolated single Aplysia neurons supports a multiexponenti al model. The ADCs are consistent with previous measurements in the cytopla sm of single neurons and with the slow ADC measurement in perfused brain sl ices. These distributions may explain the multiple compartments observed in tissues, greatly aiding the development of quantitative models of MRI in w hole tissues. (C) 2001 Wiley-Liss, Inc.