LEFT: Two-dimensional polyacrylamide gel of silver-stained proteins from normal lumbar ventral roots of a 70 year-old individual. The large, densely stained area contains serum albumin. The acidic end of the gel is on the right.

RIGHT: Two-dimensional polyacrylamide gel of silver-stained proteins from normal dorsal roots of the same 70 year-old individual whose ventral root pattern was just illustrated. The protein patterns from the dorsal and ventral roots closely resemble one another. The large, densely stained area contains serum albumin. The acidic end of the gel is on the right.