Galactocerebrosides and sulfatides are major characteristic components of vertebrate myelin. In contrast, glucocerebroside is the major glycosphingolipid of shrimp nerve. In this study, the concentrations of these glycosphingolipids in the nervous systems of animais from several evolutionary branches were determined by use of high-performance liquid chromatography. In nerves of protostome animals only glucose-containing glycosphingolipids were detected, whereas glycosphingolipids from deuterostomes contained predominantly galactose. Neither the glycolipids containing a-hydroxy fatty acids nor sulfate esters of the glycolipids, both of which always accompany galactocerebrosides in deuterostome myelin, were present in protostome nerves. This correlation suggests an evolutionary trend from gluco-to galactocerebrosides, which corresponds with changes in the nervous system from loosely structured membrane-enwrapped axons to multilameliar highly structured myelin.Rapid saltatory conduction of nerve impulses in vertebrates is facilitated by the myelin sheath, a unique multilamellar membrane that tightly enwraps axons (1). Vertebrate myelin is characterized by abundant lipids, with particularly high levels of galactocerebrosidest and sulfatides, which are considered to be myelin markers (2). The nervous systems of invertebrates, on the other hand, lack true compact myelin, although axons in higher orders (e.g., crustacea) are surrounded by layers ofloosely bound membrane (3). Previously we found that the nervous system of the brown shrimp (Penaeus aztecus aztecus) contained high concentrations of glucocerebroside but no galactocerebroside (4). Since little is known about the chemical composition ofthe nervous system of lower animals and because of the possible evolutionary significance of the change from gluco-to galactocerebroside in the development of the nervous system, we began a systematic survey ofthe sphingolipid composition of nervous tissue from a wide variety of animals from several evolutionary branches. We found that, whereas nervous system glycolipids from deuterostomes contained predominantly galactose, those from protostomes contained only glucose.MATERIALS AND METHODS Animals. Animals studied are listed in Table 1 and were of reproductive age unless otherwise specified. These animals were obtained either from colleagues or from marine supply houses, as also indicated in Table 1. Appropriate nerves (Table 1) were dissected under a microscope after the animal had been anesthetized either by immersion in 0.02% ethyl m-aminobenzoate methane sulfonate or by exposure to cold temperature.Glycosphingolipid Analysis. Concentrations of gluco-and galactocerebrosides and sulfatides were measured by HPLC after treating these lipids by benzoylation-desulfation as described (5). The nerves were homogenized in cold water immediately after dissection and total lipids were extracted with chloroform/methanol and washed according to Folch et al. (6). The total lipids obtained were then benzoylated with benzoyl chlo...
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