MEASUREMENT OF VASCULAR-PERMEABILITY IN SPINAL-CORD USING EVANS-BLUE SPECTROPHOTOMETRY AND CORRECTION FOR TURBIDITY

Vascular permeability can be visualized by Evans Blue (EB) extravasati on and quantified by spectrophotometry after formamide extraction of t he tissue. However, formamide extracts show significant turbidity, whi ch may contribute to the total optical density at the wavelength of me asurement (e.g., 620 lambda). We developed a simple method for estimat ing the component of the total optical density of a dyed specimen cont ributed by turbidity. Our method, which uses a determination of turbid ity made at another point of the light spectrum (740 lambda), was more precise than two other EB quantification techniques. We therefore rec ommend it for individual correction of formamide extracts of spinal co rd specimens. The application of this technique to the brain remains t o be determined.