T. M. Lo

Isolation of a guanylate cyclase inhibitor from the balsam pear (Momordica charantia abreviata)

Summary The balsam pear ( Momordica charantia abreviata ) is a plant which grows wild throughout subtropical regions including the Gulf Coast and Florida. The ripe fruit is highly toxic and produces mild hypoglycemia. Preparations of the ripe fruit and the leaves but not the unripe fruit or seeds inhibited guanylate cyclase activity whereas adenylate cyclase activity was unaffected. The guanylate cyclase inhibitor (GCI) has been purified about 30-fold has an estimated molecular weight of 5000 to 50,000 and is acid stable and heat labile. GCI blocked the activation of guanylate cyclase by nitroso chemical carcinogens, and therefore, may be useful in studying mechanisms of chemical carcinogenesis.

Immunochemical Studies of Infectious Mononucleosis

Abstract. The major sialoglycopeptide released from bovine erythrocytes by papain has been purified and characterized. The glycopeptide contains 82% by weight carbohydrate in molar ratios of galactose ‐5.5:N‐acetylglucosamine ‐3.6:sialic acid ‐2.6:N‐acetylgalactosamine ‐1.0. The carbohydrate and amino acid composition is quite different from the glycoprotein extracted from bovine erythrocyte stroma with hot 75% ethanol. The glycopeptide is devoid of reactivity with Paul‐Bunnell heterophile antibody of infectious mononucleosis ‐ an activity expressed to high degree on the bovine erythrocyte and associated with glycoprotein. The glycopeptide does react, however, with another antibody found in infectious mononucleosis as well as most normal human sera tested.

Immunochemical studies of infectious mononucleosis. VI. a radioimmunoassay for the detection of infectious mononucleosis heterophile antibody and antigen.

The coated-tube method of solid-phase radioimmunoassay has been adapted to the detection of heterophile antibodies and antigens of infectious mononucleosis. Disposable plastic hemagglutination trays were coated with purified glycoprotein from horse erythrocytes and the subsequent uptake of antibody from test sera was detected by radio-iodinated horse erythrocyte glycoprotein. In a preliminary survey of sera from patients with infectious mononucleosis and sera from controls, the assay proved highly sensitive and specific. The test system was also useful in a competitive binding assay for immunochemical studies of glycoproteins from other heterophile antigen-positive species.

Isolation of plasma membrane glycoprotein from bovine thymocytes.

Glycoprotein was isolated from a purified thymocyte membrane preparation by two methods: lithium diiodosalicylate-phenol extraction and hot 75% ethanol extraction. A higher yield of membrane sialic acid was obtained by the latter method. The preparations had similar apparent molecular weights on sodium dodecyl sulfate gel electrophoresis. Both had similar receptor activities against a panel of hemagglutinins, although the 75% ethanol extract was more active on a weight basis. However, there were significant differences in carbohydrate and amino acid compositions of the two thymocyte extracts. The lithium diiodosalicylate-extracted material had much more glucose, ribose, and glycine than the ethanol extract. The glycoprotein preparations from thymocytes were quite distinct from the glycoprotein of bovine erythrocytes in both composition and receptor properties.

Immunochemical Studies of Infectious Mononucleosis IV. Effect of Proteases on the Glycoprotein of Horse Erythrocytes

Summary The effects of three proteases, trypsin, papain, and pronase, upon the major glycoprotein of horse erythrocyte membranes were examined. By three independent criteria, papain was the most effective. Sodium dodecyl sulfate polyacryla-mide gel electrophoresis of stroma derived from papain-treated erythrocytes revealed the loss of the major glycoprotein band characteristic of this membrane. Concomitant with the loss of the major glycoprotein band, fragments were released from the erythrocyte which had a carbohydrate composition similar to that of the intact glycoprotein. Also, reactivity of the treated erythrocytes with infectious mononucleosis antibody, a property associated with the major glycoprotein, was reduced. Only a portion of the membrane glycoprotein was susceptible to pronase action and none was cleaved by trypsin.

Glycoproteins from the Bovine Erythrocyte Membrane

Publisher Summary The chapter describes the extraction of glycoproteins from the bovine erythrocyte membrane. The earlier reports show the isolation of Paul–Bunnell infectious mononucleosis (IM) antigen from bovine erythrocytes (BRBC). In the study described in the chapter, this antigen was extracted from the membranes with hot 75% ethanol. The chapter discusses the isolation by lithium 3, 5-diiodosalicylate (LIS)–phenol–water extraction of a glycoprotein from BRBC membrane and presents the results obtained with the two extraction methods (LIS–phenol) and hot 75% ethanol, applied to a BRBC membrane preparation from a single animal. The chapter presents a comparison of two glycoprotein preparations by electrophoresis.