ABSTRACT
Mucus is a substance which gels under appropriate conditions of concentration and other environmental factors, but the comparative weakness of the gel enables relatively simple gel-sol transformations to take place. Rice water stools are the hallmark of cholera diarrhea, the product of excessive passage of both mucus and fluid. In addition to being a potent stimulus for electrolyte secretion by the intestine, cholera toxin also stimulates the secretion of mucin. Mucins are the major organic constituent of mucus and have viscoelastic properties which account very satisfactorily for all of the gelling characteristics of whole mucus. Native mucins are negatively charged to varying degrees by virtue of their sialic acid and sulfate residues. Neutral mucins also have longer oligosaccharide chains than sialomucins, and are on average, denser and more glycosylated. Mucins contain yet another component which offers the potential for genetic and metabolic control, the "link" peptide.
