A HISTOCHEMICAL AND BIOCHEMICAL STUDY OF THE POLYSACCHARIDIC SUBSTANCES OF THE DEVELOPING NERVOUS SYSTEM OF THE RAT IN RELATION WITH THE APPEARANCE OF CHOLINESTERASE ACTIVITY

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Abstract
The PAS reaction and the cholinesterase reaction run parallel in the lower centers of the developing nervous system in the rat. Also, the two reactions appear progressively between the 10th and 15th day as the result of a chemical maturation of the neurons. Extraction of sections with methanol–chloroform does not alter the PAS reaction while acetylation inhibits it reversibly. These two facts suggest that 1,2-glycol groups are detected. Inhibition by hyaluronidase increases this evidence, despite the fact that diastase has a slight and irregular action. To elucidate the nature of the PAS reaction further, chemical fractionation of the brain substance has been attempted. (A) A fraction soluble in methanol–chloroform is metachromatic and PAS-positive in vitro. (B) A fraction soluble in a potassium chloride – potassium carbonate mixture is non-dialyzable, non-metachromatic, but PAS-positive. After acid hydrolysis it yields glucose but no hexosamine. (C) A fraction extracted from the residue by sodium hydroxide is non-dialyzable, non-metachromatic, but also PAS-positive. By chromatography and electrophoresis it is found to contain a non-sulphated mucoprotein yielding hexosamine in a high concentration following acid hydrolysis. The physiological significance of this mucoprotein is discussed.