Purification of a sialic acid-specific lectin from the Indian scorpion Heterometrus granulomanus

A sialic acid-specific lectin, scorpin, has been purified to apparent homogeneity from the Indian scorpion Heterometrus granulomanus by affinity chromatography on equine submandibular gland glycopeptides linked to Sepharose and gel filtration on Sephadex G-200. The lectin has a molecular mass of 500 000 Da and was dissociated into single polypeptide chains of 15 000 Da, as determined by SDS gel electrophoresis in the presence of 2-mercaptoethanol. Scorpin is a glycoprotein containing 2.8% sugars. Its specificity was investigated by the inhibition of hemagglutination with various derivatives of sialic acid and other sugars. N-Acetylneuraminic acid gave better inhibition than N-glycoloylneuraminic acid but showed less inhibitory effect than sialyl-alpha(2----3)-lactose and disialyllactose. Among the sialoglycoconjugates tested, equine submandibular gland glycopeptide was found to be the most potent inhibitor. Scorpin showed a strong tendency to bind to carboxyl groups, since reduction of the carboxyl group of N-acetylneuraminic acid destroyed the inhibitory potency of this sugar. Furthermore, D-glucuronic acid inhibited hemagglutination whereas N-acetylglucosamine or N-acetylgalactosamine were not inhibitors.     

Ganglioside, protein, hexose, and sialic acid changes in the trisected optic tectum of the chick embryo.

Spatiotemporal changes in membrane constituents of cells from the optic tectum of the chick embryo were analyzed during the period of maximum differentiation and synaptogenesis. Each tectum from 6-, 8-, 10-, and 12-day embryos was cut into three subregions along the topological gradient of differentiation. Electrophoretic analysis of proteins revealed an already complex population by Day 6 which remained relatively unchanged through later stages, with little if any topological variations. In contrast, chromatographic analysis of gangliosides showed an increasingly complex pattern as differentiation proceeded, with a growing preponderance of multisialogangliosides. Total membrane protein increased symmetrically with tissue mass in each subregion. However, hexose concentration and sialic acid/hexose ratios showed strikingly asymmetrical topological distributions as early as Day 8, and tended to fluctuate reversibly within brief (1 day or less) time periods. These results suggest that during the period of maximal differentiation and retino-tectal synaptogenesis in the optic tectum of the chick, the membrane protein population remains relatively stable and topologically invariant, whereas the polysaccharide chains of membrane macromolecules fluctuate according to topological position and developmental state in a complex, relatively rapid, and apparently oscillatory fashion.     

Purification of a unique glycoprotein that enhances phenol oxidase activity in scorpion (Heterometrus bengalensis) haemolymph.

A monomeric glycoprotein (SGP) of Mr 32,000 was isolated to purity from scorpion (Heterometrus bengalensis) haemolymph by (NH4)2SO4 fractionation, chromatofocusing and h.p.l.c. The homogeneity of SGP is confirmed by polyacrylamide-gel electrophoresis. SGP is soluble in 100%-satd. (NH4)2SO4 solution. Needle-shaped crystals of SGP were obtained in an aqueous environment. The glycan part of the molecule contains arabinose, which does not commonly occur in animal glycoproteins. Amino acid analysis demonstrated a preponderance of glycine, tyrosine and glutamic acid. SGP enhances phenol oxidase (EC 1.14.18.1) activity.     

Glycosidically bound sialic acid levels as a predictive marker of postoperative adjuvant therapy in gastric cancer

Summary A group of 293 gastric cancer patients were examined to see if the preoperative value of glycosidically bound sialic acid is a predictor of prognosis and effectiveness of postoperative adjuvant therapy. All patients had gastrectomies and were histologically confirmed to have primary adenocarcinoma of the stomach. Some patients then received either postoperative adjuvant chemotherapy or immunochemotherapy. Patients with sialic acid levels less than 74.5 mg/dl survived significantly longer than those with sialic acid levels of 74.5 mg/dl or of 85.3 mg/dl and over. No significant differences in survival were found among patients treated by gastrectomy alone, gastrectomy plus chemotherapy and gastrectomy plus immunochemotherapy. However, patients with abnormally elevated levels of sialic acid survived significantly longer when they were treated with immunochemotherapy after gastrectomy than those treated by gastrectomy alone or with chemotherapy after gastrectomy. By using Cox's multivariate regression model, pTNM stages, postoperative adjuvant therapy (chemotherapy and immunochemotherapy) and preoperative serum levels of sialic acid were examined as prognostic variables. Postoperative therapy was a significant prognostic variable in patients with abnormally elevated levels of sialic acid. The preoperative serum level of sialic acid is a promising predictive marker of the response to postoperative adjuvant immunochemotherapy.     

Purification and partial characterization of an erythroagglutinin from the hemolymph of scorpion, Heterometrus bengalensis

An erythroagglutinin from the hemolymph of the scorpion, Heterometrus bengalensis, has been purified by gel filtration and ion-exchange chromatography. Its homogeneity has been demonstrated by polyacrylamide gel electrophoresis. The purified agglutinin appears to be a monomeric protein having a possible molecular weight between 146,000 and 148,000. It has no divalent cation requirement for erythroagglutination. The erythroagglutination is not inhibited by saccharides, glycoproteins and mucin. Identical erythroagglutination pattern is obtained with normal as well as neuraminidase treated erythrocytes.     

Effects of calcium and bound sialic acid on the viscosity of mucin

A viscosity drop was observed when pig gastric mucin was titrated with HCl below pH 3.0. When EDTA was present, addition of HCl resulted in an increase in viscosity between pH 3.0 and pH 1.0. Previous treatment of the mucin solution with neuraminidase abolished the pH-dependent viscosity rise in the presence of EDTA.