Concentration, composition and structure of gangliosides from the central nervous systems of dogfish, squalus acanthia, and cod, gadus callarias

Abstract

1. 1. Gangliosides were isolated from the cerebral grey and white matter and spinal cord, and from the brain and spinal cord myelin of dogfish and cod. In the cod the highest ganglioside concentration, expressed as lipid- N-acetylneuraminic acid, was found in cerebral (forebrain) grey matter, 1.67 μmol/g. It was lower in cerebral white matter, 1.13 μmol/g, and spinal cord, 0.70 μmol/g. In dogfish the relations between the concentrations were unique, with the lowest concentration in cerebral grey matter, 0.93 μmol/g, higher in cerebral white matter, 1.13 μmol/g, and the highest in spinal cord, 2.36 μmol/g. 2. 2. Cod brain and spinal cord and dogfish brain had a high proportion of tetra- and pentasialogangliosides, 50–60% of total sialic acid. Of these, the tetrasialogangliosides were the largest fraction in the cod nervous tissues while the pentasialogangliosides were the largest fraction in the dogfish brain. In spinal cord of dogfish GM2 was the predominant ganglioside and accounted for 60% of the total sialic acid. In addition to GM2, spinal cord also contained 12% of the total sialic acid in GD2 and approximately 2% in GT2. 3. 3. The major portions of ganglioside GM2 and GD2 of dogfish were isolated in the myelin fraction which contained a uniquely high ganglioside proportion. The molar ratio of the lipids in spinal cord myelin was: phospholipid: cholesterol:cerebroside:ganglioside-NeuAc (1.00:1.02:0.22:0.021). In the cod myelin the corresponding values were: 1.00:0.76:0.033:0.0033. In the cod myelin the gangliosides with three or more sialic acids accounted for the main part of the total sialic acids. 4. 4. In the nervous system of the dogfish, all the higher gangliosides of the G1 series, GD1, GT1, GQ1 and GP1, had a fatty acid composition similar to gangliosides in mammalian brain, with stearic acid as the dominating fatty acid. In ganglioside GM2 and GD2 the fatty acid 22:1 was more than 60% of the total acids. In cod, stearic acid was the major fatty acid in all the gangliosides.