RAPID AXONAL TRANSPORT IN VITRO IN THE SCIATIC SYSTEM OF THE FROG OF FUCOSE‐, GLUCOSAMINE‐ AND SULPHATE‐CONTAINING MATERIAL

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Abstract
—An in vitro system from the frog has been used to study fast axonal transport of glycoproteins. The migration of [3H]fucose‐, [3H]glucosamine‐ and [35S]sulphate‐labelled material was followed from the dorsal ganglia, along the sciatic nerve towards the gastrocnemius muscle.The distribution in different subcellular fractions, effect of cycloheximide and transport kinetics did not differ very much between fucose‐ and glucosamine‐incorporation into the nerve. Cycloheximide blocked the synthesis of TCA‐insoluble radioactivity, which was transported at a rate of 60–90 mm per day at 18°C, more effectively than the synthesis of stationary proteins in the ganglia. About 10 per cent of the TCA‐insoluble and transported radioactivity was extracted by chloroform‐methanol (2:1, v/v) and might be glycolipids and the rest glycoproteins. Results suggest that TCA‐soluble activity, which was recovered in the nerve, originated in part from labelled macromolecules consumed along the axons. The rapidly transported TCA‐insoluble radioactivity was 85 per cent particulate and mainly associated with structures sedimenting in the microsomal fraction.[35S]Sulphate‐labelled TCA‐insoluble material was resistant towards chloroform‐methanol (2:1, v/v) extraction and rapidly transported from the ganglia into the nerve. The synthesis was inhibited by cycloheximide. The material, probably proteoglycans, represented a quantitatively minor part of transported glycoproteins.

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