Preparation of unsaturated disaccharides by eliminative cleavage of heparin and heparan sulfate with heparitinases.

1. Six kinds of unsaturated disaccharides were prepared by enzymatic digestion of heparin and heparan sulfate with heparitinases I0 and IV, and subsequent column chromatography. They were identified by HPLC showing good separation from each other. 2. The content of each unsaturated disaccharide fraction was determined colorimetrically, and found to range from 130.7 to 722.3 mumol. 3. Molecular extinction coefficient of each unsaturated disaccharide was calculated from absorbance at a wavelength of around 230 nm where a peak appeared on the ultraviolet spectrum of each disaccharide solution at pH 2. The values varied from 6000 to 6600.     

Contrasting of Lowicryl K4M thin sections.

A method is presented for increasing the contrast of cellular structures on ultrathin sections from tissues embedded in Lowicryl K4M. The method, designated UA/MC adsorption staining, is based on the uranyl acetate/methyl cellulose staining of thawed cryosections. Ultrathin Lowicryl K4M sections were exposed to a uranyl acetate/methyl cellulose solution and the excess solution was removed with filter paper, leaving the remainder to air dry on the section. Sections on the grids were then directly observed in the electron microscope. Parameters such as methyl cellulose and uranyl acetate concentrations, duration of staining, temperature and pH were all assessed for their effect on subsequent contrast formation. Conditions were achieved which yielded intense contrast of cellular membranes, basement membranes and extracellular matrix components usually not apparent in Lowicryl K4M thin sections routinely counter-stained with uranyl acetate and lead acetate. The enhancement of the contrast of these structures does not obscure colloidal gold particles used for immunocytochemistry or lectin labeling, thus making the UA/MC adsorption staining method useful for increasing membrane contrast in routine post-embedding immuno- and lectin cytochemistry on Lowicryl K4M thin sections.