It has been found that the aqueous humour contains about the same protein fractions as the serum (Witmer 1952, Wunderly and al. 1954, Frangois and al. 1958. At the proteins of serum there are always bound carbohydrates such as hexose, hexosamine, sialic acid and fucose (Winzler 1958). The literature gives meagre information about the presence of these carbohydrates in the aqueous; hexosamine, however, having been found there in small amounts (Meyer and al. 1938). The purpose of the present work was to study the protein-bound carbohydrates of the aqueous humour, especially sialic acid and hexosamine.
MATERIAL A N D METHODSThe aqueous humour was aspirated from cleaned eyes of freshly slaughtered cattle. About 0.5-2 ml was taken from each eye. The proteins of aqueous were precipitated by the addition of 90 parts of ethanol to 10 parts of aqueous. After centrifugation the precipitate was washed twice with ethanol and dissolved to 21/z parts of 0.1-n NaOH, when a fourfold concentration was obtained. The quantitative analyses were made from this solution; for qualitative analyses samples were concentrated by dialysis under pressure. The presence of sialic acid was shown by using the Bial and the direct Ehrlich colour reactions (Werner and Odin 1952). The quantitative determination of sialic acid was made by a colorimetric resorcinol method (Svennerholm 1957) modification (Miettinen and Takki-Luukkainen) using as a standard N-acetylsialic acid.-$)
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