We performed the simultaneous measurement of intrinsic optical signals (IOSs) related to metabolic activity and cellular and subcellular morphological characteristics, i.e., light scattering for a rat global ischemic brain model made by rapidly removing blood by saline infusion. The signals were measured on the basis of multiwavelength diffuse reflectances in which 605 and were used to detect the IOSs that are thought to be dominantly affected by redox changes of heme and CuA in cytochrome c oxidase (CcO), respectively. For measuring the scattering signal, the wavelength that was found to be most insensitive to the absorption changes, e.g., , was used. The measurements suggested that an increase in the absorption due to reduction of heme occurred soon after blood clearance, and this was followed by a large triphasic change in light scattering, during which time a decrease in the absorption due to reduction of CuA occurred. Through the triphasic scattering change, scattering signals increased by (), and the increase in light scattering showed significant correlation with both the reflectance intensity changes at 605 and . This suggests that morphological changes in cells correlate with reductions of heme and CuA. Histological analysis of tissue after the triphasic scattering change showed no alteration in either the nuclei or the cytoskeleton, but electron microscopic observation revealed deformed, enlarged mitochondria and expanded dendrites. These findings suggest that the simultaneous measurement of absorption signals related to the redox changes in the CcO and the scattering signal is useful for monitoring tissue viability in the brain.
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