Two neutral glycosphingolipids having large straight oligosaccharide chains with eight and nine sugars, provisionally named COS and CNS, were isolated and purified from larvae of the green-bottle fly, Lucilia caesar, as the only two remaining unidentified significant neutral glycolipids in this organism. From the results of sugar analysis, permethylation, negative-ion fast atom bombardment mass spectroscopy (FAB-MS), and 1H-NMR studies, the structures of the two glycolipids are proposed to be: COS, GalNAc beta 1-3GlcNAc beta 1-3Gal beta 1-3GalNAc alpha 1-4GalNAc beta 1-4GlcNAc beta 1-3Man beta 1-4Glc beta 1-Cer; and CNS, Gal beta 1-3GalNAc beta 1-3GlcNAc beta 1-3Gal beta 1-3GalNAc alpha 1-4GalNAc beta 1-4GlcNAc beta 1-3Man beta 1-4Glc beta 1-Cer. The fatty acid and long-chain base compositions of the above glycolipids were very similar, and were dominated by arachidic acid, and tetradeca- and hexadeca-4-sphingenines. The great similarity between the compositions of their ceramide moieties suggests that COS may be a precursor in the glycosylation reaction yielding CNS.
Five kinds of percept have been found to occur when two different stimulus objects are simultaneously presented, exchanging positions with each other in successive exposures. These five percepts can be classified as follows: (i) Appearance-Disappearance (succession), (ii) Lateral Motion, (iii) Depth Motion, (iv) Transmutation (in colour, brightness, and/or shape), and (v) Overlapping (simultaneity). Results of three experiments indicate that relative dominance among these five percepts systematically depends upon differences between the two stimulus objects in colour, luminance, shape, and size. The relative dominance depended upon the stimulus onset asynchrony (SOA) between successive presentations and on the spatial separation between the two objects. Lateral Motion became more dominant as a result of (a) an increase in the number of stimulus attributes differing between the two objects, (b) an increase in the SOA, or (c) a decrease in the distance between the two objects. Colour difference, even without a luminance difference, was one of the determinants for Lateral Motion. Depth Motion frequently occurred when the two objects differed in size and the SOA and the distances between them were relatively great. Transmutation occurred when the objects differed in colour, luminance, or shape. Perceptual modes (ii) to (iv) can be understood as different results of perceptual organisation that always maintains perceptual identity of objects and maintains perceptual constancy of their attributes as much as possible. Long-range apparent motion could be a result of such perceptual organisation.
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