The overall aim of our continuing investigation is to correlate the structure, localization and metabolism of complex carbohydrates with their functional roles in nervous tissue. To obtain information concerning extracellular matrix glycosaminoglycans during brain development, we plan to extend our previous immunoelectron microscopic studies of the chondroitin sulfate proteoglycans to an examination of hyaluronic acid, which will be localized by means of a novel histochemical probe consisting of biotinylated hyaluronic acid binding region prepared from a chondrosarcoma proteoglycan. Related studies will be aimed at extending our preliminary finding of a significant decrease in the molecular size of hyaluronic acid during brain development. Hyaluronidase will also be purified from rat brain, biochemically characterized, and used to generate antibodies for immunocytochemical studies of its localization in developing and mature brain. We plan to continue our studies on the chondroitin sulfate and heparan sulfate proteoglycans of brain, including the structures of their protein cores and their possible homologies with those of nonnervous tissue proteoglycans. These investigations should also yield more detailed information concerning the distribution of the chondroitin sulfate and heparan sulfate polysaccharide chains and the different types of glycoprotein oligosaccharides on the core proteins. Other studies of the chondroitin sulfate proteoglycan will be aimed at obtaining information concerning the sites and time-course of its biosynthesis. Antibodies will also be prepared to the heparan sulfate proteoglycan which we have recently isolated and partially characterized, for use in immunocytochemical studies on its localization in nervous tissue. Other investigations will be directed towards increasing our understanding of the functional importance of structural specificity in brain glycoprotein oligosaccharides. We will examine the ability of neurons and astrocytes to interact with structurally defined brain glycoprotein oligosaccharides, and in related experiments, we will determine the degree to which the oligosaccharide structures of the Thy-1 glycoprotein may vary in different types of nervous tissue such as PC12 pheochromocytoma cells and purified neurons and astrocytes, and whether these structures are modified in response to functional changes such as nerve growth factor-induced neurite extension in PC12 cells, brain development, or the astroglial differentiation which occurs in response to contact with neurons.
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