Measurement of edema in the nervous system. Use of Percoll density gradients for determination of specific gravity in cerebral cortex and white matter under normal conditions and in experimental cytotoxic brain edema.

A method is presented by which density measurements can be performed on samples from cerebral cortex and white matter of normal and intoxicated animals using nontoxic ingredients as an alternative to the bromobenzene-kerosene technique described by Nelson et al. (1971). A continuous density gradient is prepared in a calibrated glass cylinder by using a new product, Percoll, which consists of colloidal silica particles coated with polyvinyl pyrrolidone. The gradient is stable and the same column can be used for repeated experiments over a long period of time. Interactions between the gradient media and the samples are evaluated and various methodological aspects concerning removal and handling of the tissue samples are presented. Experiments with acute triethyltin (TET) intoxication in the mouse and the hamster show that the Percoll technique can be used as an alternative to the bromobenzene-kerosene method in quantitative studies on cytotoxic brain edema.