Optical light scatter imaging of cellular and sub-cellular morphology changes in stressed rat hippocampal slices

Optical imaging, such as transmission imaging, is used to study brain tissu e injury. Transmission imaging detects cellular swelling via an increase in light transmitted by tissue slices due to a decrease in scattering particl e concentration. Transmission imaging cannot distinguish sub-cellular parti cle size changes from cellular swelling or shrinkage. We present an optical imaging method, based on Mic scatter theory, to detect changes in sub-cell ular particle size and concentration. The system uses a modified inverted m icroscope and a 16-bit cooled CCD camera to image tissue light scatter at t wo angles. Dual-angle scatter ratio imaging ne successfully discriminated l atex microsphere suspensions of differing sizes (0.6, 0.8, 1 and 2 mu m) an d concentrations. We applied scatter imaging to hippocampal slices treated with 100 mu M N-methyl-D-aspartate (NMDA) to model er;exitotoxic injury or - 40 mOsm hypotonic perfusion solution to cause edema injury. We detected l ight scatter decreases similar to transmission imaging in the CA1 region of the hippocampus for both treatments. Using our system, we could distinguis h between NMDA and hypotonic treatments on the basis of statistically signi ficant (P < 0.0003) differences in the scatter ratio measured in CA1. Scatt er imaging should be useful ill studying tissue injuries or activity result ing in brain tissue swelling as well as morphological changes in sub-cellul ar organelles such as mitochondrial swelling. (C) 2000 Elsevier Science B.V . All rights reserved.