Protein analysis of myelin isolated from the CNS of fish: developmental and species comparisons.

The protein composition of myelin isolated from the CNS of four different fish species (trout, goldfish), eel, Tilapia) was analysed by SDS-polyacrylamide gel electrophoresis and compared with that of pig and rat brain. Thereby the following features were found typical to the myelin of fish: (1) a basic protein of particular low molecular weight, (2) the entire absence of Wolfgram protein, (3) the appearance of an additional major component of medium molecular weight (around 36,000) and (4) a strong Con A-affinity exhibited by the intermediate proteins, being most clearly discernible in trout and eel myelin. During development of the trout brain, in particular, a myelin fraction could first be isolated from the brainstem at 14 days after hatching and the myelin yield steadily increased during the first year of life. In tectum and cerebellum main myelin accumulation was stated during the third and seventh month. Concomitantly marked changes in the relative distribution of major myelin proteins were observed: especially the IP1-protein showed a marked increase during the first half year, while the relative amount of the 36-K protein was gradually declining during the same time.