RELAXATION-TIME AND DIFFUSION NMR MICROSCOPY OF SINGLE NEURONS

Relaxation-time and diffusion-weighted NMR micrographs have been obtai ned for single neurons isolated from Aplysia californica. These images allow the nucleus and cytoplasm to be clearly differentiated, in cont rast to proton spin-density images, which appear relatively homogenous . Images of the spatial distribution of T1 and T2 relaxivities and the diffusion coefficient (D), as well as average values for T1, T2, and D in the cytoplasm and nucleus, were calculated from sets of appropria tely weighted images. In all cases, water in the nucleus had relaxatio n and diffusion properties markedly differing from those of cytoplasmi c water, which in turn had properties which were distinct from those o f free water. Additionally, the cytoplasmic T2 was observed to triple following cell death, which is attributed to cytoplasmic dilution as w ater enters the cell. The work presented represents the first effort a t a consistent exploration of the spatial distribution of NMR characte ristics of water within intact single cells. These studies have implic ations both for modeling the NMR characteristics of water in neuronal tissues based on an understanding of the characteristics of water in d ifferent cell compartments and for understanding water/macromolecule i nteractions within cells. NMR microscopy studies such as these may hel p form a foundation for understanding and interpreting NMR characteris tics measured from large assemblies of cells, i.e., spectroscopy and i maging of living tissues. (C) 1994 Academic Press, Inc.