Biochemistry in routine neuropathology. II. Determination of hexosamine in chloroform-methanol extracts of brain as a diagnostic procedure with special references to the quantitation of gangliosides.

Abstract

Neuropathological interest in the gangliosides originates from Klenk's dis­ covery that these lipids are accumulated in the brain in infantile amaurotic idiocy (Tay-Sachs disease) and, to a lesser extent, also in the brain in Niemann Pick disease. Consequently measurement of the ganglioside content of the brain may be an aid either in the diagnosis of incidental cases suspect for these diseases, or speaking more broadly, in answering the question whether a given group of neuropathologic ally similar cases should be classified with the lip­ idoses or not. Thus estimation of gangliosides seemed especially indicated in various types of leucodystrophies (1) which, on the basis of their histopatho­ logical features, ,,,ere often assumed to bear a kinship with amaurotic idiocy. The usual method for the estimation of gangliosides in nervous tissue was devised by Klenk and Langerbeins (2) and is essentially based on colorimetrical determination of one of the characteristic components of the ganglioside molecule (i.e. neuraminic acid, Table 1) in a chloroform-methanol extract. Unfortunately, however, adoption of this method for routine purposes was hampered by the fact that a pure neuraminic acid compound, required for the preparation of standard solutions is not for sale and can be only obtained through a chemical laboratory able and willing to produce it by means of a difficult and time con­ suming isolation method .. Moreover, it was not possible to measure neura­ minic acid accurately in samples of the white matter of the brainl as it was re­ quired in the study of the leucodystrophies (1). Therefore, an attempt was made to replace the neuraminic acid determination by the determination of the quan­ tity of hexosamine present in a chloroform-methanol extract. This substance is another component of the ganglioside molecule (fig. 1), and it was presumed that in a lipid extract hexosamine and neuraminic acid come from the same