Dialysable Neuraminic Acid in Human Cerebrospinal Fluid

Abstract

BECAUSE of the presence of interfering sugars in great excess, it has not been possible heretofore to determine with any certainty in other laboratories as well as our own¹ whether neuraminic acid occurs in dialysable form in cerebrospinal fluid. Recent methods developed in this laboratory for the quantitative fractionation of all the carbohydrate constituents of specimens of human cerebrospinal fluid have been described in the first paper of this series on the cerebrospinal fluid². By using concentration by lyophilization and exhaustive dialysis, all the solids of cerebral spinal fluid have been separated quantitatively into non-dialysable and dialysable fractions. An accurate estimate of the neuraminic acid bound to protein has thereby been obtained without interference from dialysable sugars^2,3. Evidence is now presented that neuraminic acid does indeed occur in dialysable form as well as in protein-bound form, in specimens of human cerebrospinal fluid. The dialysable neuraminic acid does not, however, appear to be free, but rather to be bound to hexose and nitrogenous residues in glycopeptide-like low molecular weight compounds.