A phylogenetic survey of brain myelin ganglioside patterns and concentrations has been carried out on 16 vertebrate species. Gangliosides were isolated from purified myelin and found to vary in concentration from 25 micrograms of sialic acid per 100 mg of myelin for goldfish to a value of 395 for turkey. The latter species had approximately equivalent amounts of GM1 and GM4 as the two major gangliosides. The 11 mammals studied all had GM1 as the major ganglioside, with variable amounts of GM4; rhesus monkey and human had 20-25% GM4, whereas the others had less than 10%. Amphibia and fish myelin contained the least total ganglioside, with patterns that showed relatively little GM1 and no detectable GM4. Alligator myelin was unique in having a total concentration as high as the avian species, but a pattern with predominantly di- and trisialo gangliosides.
Gangliosides were isolated from purified myelin obtained from brain and spinal cord of mature chickens and pigeons. Total concentrations were approximately two- to fivefold greater than for previously reported mammalian species, and their patterns also differed in containing significantly more sialosylgalactosylceramide (GM4). The latter comprised one-third to one-fourth of total myelin ganglioside, approximately equivalent to GM1 (II3NeuNAcGgOse4Cer). As in mammals, GM4 of avian CNS appeared to be localized in myelin. Fatty acids of this ganglioside included both the hydroxy- and unsubstituted types, and long-chain bases were almost entirely C18. Ganglioside GM1 split into two closely migrating bands on TLC, the slower of which resembled mammalian GM1 in having stearate as the main fatty acid with a measurable amount (10%) of C20-sphingosine; the faster band had predominantly longer-chain fatty acids and very little C20-sphingosine.
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