Concentration of Vertebrate Brain Gangliosides. In the approximately 150 vertebrate species investigated sofar, there is great variation in the brain ganglioside ...
PHYLOGENY OF VERTEBRATE BRAIN GANGLIOSIDES R. Hilbig and H. Rahmann Institute of Zoology University of Stuttgart-Hohenheim Garbenstr. 30 0-7000 Stuttgart 70 F. R. Germany INTRODUCTION Gangliosides, a group of complex sialic acid-containing glycosphingolipids are common in the deuterostomate phyla. They have not been detected in even the most highly developed protostomia (56). Among the deuterostomia intensive investigations of ganglioside occurrence and distribution have been carried out, especially for the vertebrates. Considerable interest was focused on nervous tissue (69), whose neurons are unique in ganglioside composition. Whereas extraneuronal tissues and cells generally contain different classes of these substances as minor components (e.g. lac to- and haematoside families), the neuronal plasma membrane contains 10-15 % gangliosides of its total lipid in the form of gangliotri- and -tetraose series. This impressive value increases for the synaptic terminals, in which the gangliosides are according to Ledeen (35,36) thought to be even more enriched. The multiplicity of structural types in neuronal gangliosides, which mainly belong to the ganglio~series, has been pointed out in recent reviews (1,69) and is considered as a general characteristic of CNS neurons. The relative proportions of these different "molecular species" varies significantly among neuronal tissues and types of cells (4, 14,18,64) due to the high content in nervous membranes. Their physicochemical (59) and immunologic (19) properties gangliosides are suggested to have a distinctive role in neuronal differentiation (26,43,52), cell recognition and receptor-function (9,19,20, 65,68,72), adaptive processes and are assumed to be deeply involved in synaptic transmission (44,45,49). All comparative phylogenetic studies concerning the occurrence of gangliosides in vertebrate CNS tissue reveal a great variability in the concentration and composition; these differences are probably to a certain extend due to differences in methods used (4,5,15,18,24,29), but based mainly on the genetic peculiarities of the species investigated (55,58). Improved analytical methods in some cases have changed the reliability of results and many hypotheses or research concepts (5,7,33) about these compounds had to be changed. Nevertheless, some general conclusions about ganglioside concentration and composition concerning phylogenetic differentiation can be drawn.
NATO AS! Series, VoL H7 Gangliosides and Modulation of Neuronal Functions Edited by H, Rahmann © Springer-Verlag Berlin Heidelberg 1987
334 RESUL TS AND DISCUSSION 1. Concentration of Vertebrate Brain Gangliosides In the approximately 150 vertebrate species investigated sofar, there is great variation in the brain ganglioside values among the lower heterothermic vertebrates (e.g. all classes of fish, amphibians, reptiles), and the higher evolved homeothermic birds and mammals (Fig. 1): In the cold-blooded vertebrates the concentration of whole brain samples varies from 110 to 800 g (= 0.36-2.59,41moJ) ganglioside-bound sialic acid per gram wet weight of brains. In birds it ranges between 400 and 1100 g (= 1.29-3.56I'moJ)
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