Fig. 1. Autoradiograph of a representative polyacrylamide–urea gel of dialysate samples from 0 to 60 min obtained from a single experiment with the intermediate-length oligodeoxynucleotide. The control lane  is an aliquot of the parent radiolabeled oligodeoxynucleotide injectate. The bands gradually fade over time, indicating the decreasing concentration of oligodeoxynucleotide in cerebrospinal fluid. The absence of additional bands representing portions of a metabolic product of the parent oligodeoxynucleotide shows the absence of discernible metabolism within the cerebrospinal fluid.