The present invention relates to compositions comprising semi-crystalline.beta.-1-4-N-acetylglucosamine polymers (p-GlcNac) and methods utilizing suchpolymers modulation of vascular structure and/or function. The compositionsand methods disclosed are useful for stimulating, in a p-GlcNac concentration-dependent manner, endothelin-1 release, vasoconstriction, and/or reduction inblood flow out of a breached vessel, as well as for contributing to oreffecting cessation of bleeding. The methods of the present invention comprisetopical administration of materials comprising semi-crystalline p-GlcNacpolymers that are free of proteins, and substantially free of single aminoacids as well as other organic and inorganic contaminants, and whoseconstituent monosaccharide sugars are attached in a .beta.-1-4 conformation.
