scholarly journals High density of transmembrane glycoproteins on the flagellar surface of boar sperm cells.

1984 ◽  
Vol 99 (2) ◽  
pp. 655-660 ◽  
Author(s):  
A P Aguas ◽  
P Pinto da Silva
Keyword(s):  
Concanavalin A ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Freeze Fracture ◽  
High Density ◽  
Phospholipid Bilayer ◽  
Boar Sperm ◽  
Surface Motility ◽  
Membrane Components

Membrane halves of boar sperm flagella were produced by freeze-fracture and labeled in situ with concanavalin A and wheat germ agglutinin; the lectins were visualized with protein-gold complexes. Concanavalin A and wheat germ agglutinin binding sites partition with both protoplasmic and exoplasmic halves of the membrane. A high density of lectin marking was found on protoplasmic membrane halves; we conclude that the label corresponds to transmembrane glycoproteins that, on freeze-fracture, are dragged across the outer (exoplasmic) half of the phospholipid bilayer. Our demonstration of numerous transmembrane proteins in sperm flagella offers the structural setting for previous models on flagellar surface motility that postulate accessibility of motile membrane components to the submembranous cytoskeleton.

scholarly journals Freeze-fracture cytochemistry: localization of wheat-germ agglutinin and concanavalin A binding sites on freeze-fractured pancreatic cells.

1981 ◽  
Vol 91 (2) ◽  
pp. 361-372 ◽  
Author(s):  
P Pinto da Silva ◽  
M R Torrisi ◽  
B Kachar
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Concanavalin A ◽  
Binding Sites ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Freeze Fracture ◽  
Combined Application ◽  
Pancreatic Cells ◽  
Critical Point Drying

The combined application of thin-section and critical-point-drying "fracture-label" is used to determine the pattern of distribution and partition of wheat-germ agglutinin and concanavalin A binding sites on the membrane faces of freeze-fractured exocrine and endocrine rat pancreatic cells. Whereas the exoplasmic face of plasma membrane is preferentially labeled by both lectins, the endoplasmic reticulum and nuclear envelope are strongly and uniformly labeled by concanavalin A but not by wheat-germ agglutinin. The results support current views in the glycosylation of membrane proteins and do not support the backflow of sialidated glycoproteins to the endoplasmic reticulum.

Transport Characteristics of Wheat Germ Agglutinin-Modified Insulin-Liposomes and Solid Lipid Nanoparticles in a Perfused Rat Intestinal Model

2006 ◽  
Vol 6 (9) ◽  
pp. 2959-2966 ◽  
Author(s):  
Na Zhang ◽  
Qineng Ping ◽  
Guihua Huang ◽  
Xiuzhen Han ◽  
Yanna Cheng ◽  
...  
Keyword(s):  
Solid Lipid Nanoparticles ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Serum Insulin ◽  
Lipid Nanoparticles ◽  
Solid Lipid ◽  
Mucosal Absorption ◽  
Perfusion Experiment ◽  
Absorption Sites

Wheat germ agglutinin (WGA) modified liposomes and solid lipid nanoparticles (SLNs) were evaluated for improving intestinal absorption of insulin. In an in situ local intestinal perfusion experiment, formulations containing 100 IU/kg insulin were administered to the duodenum, jejunum, and ileum of fasted rats. As hypothesized, ileum was the best intestinal location for the absorption of insulin-containing liposomes. Serum insulin concentrations decreased for the various formulations in different absorption sites according to the following trends: Duodenum > ileum > jejunum for WGA-modified insulin-containing liposomes; duodenum > jejunum > ileum for WGA-modified insulin-containing SLNs; ileum > jejunum > duodenum for insulin-containing liposomes; ileum > duodenum > jejunum for insulin-containing SLNs; and duodenum ≥ ileum > jejunum for aqueous solution of insulin. These results imply that the nanoparticle type and delivery site were important factors with respect to increasing the bioavailability of insulin following oral administration. The proteolytic degradation as well as the epithelial permeability were primary determinants influcing insulin mucosal absorption.

scholarly journals Receptor-mediated gonadotropin action in the ovary. Inhibitory actions of concanavalin A and wheat-germ agglutinin on gonadotropin-stimulated cyclic AMP and progesterone responses in ovarian cells

1981 ◽  
Vol 200 (1) ◽  
pp. 153-159 ◽  
Author(s):  
S Azhar ◽  
K M Menon
Keyword(s):  
Cyclic Amp ◽  
Concanavalin A ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Carbohydrate Chain ◽  
Inhibitory Effect ◽  
Dolichos Biflorus ◽  
Acetylneuraminic Acid ◽  
Ovarian Cells ◽  
Proline Incorporation

Pretreatment of ovarian cells with concanavalin A and wheat-germ agglutinin blocked the gonadotropin-induced cyclic AMP and progesterone responses and this effect was time- and concentration-dependent. Basal production of either cyclic AMP or progesterone, however, was not affected by treatment of cells with lectin. The effect of concanavalin A on gonadotropin-mediated cyclic AMP and progesterone responses was blocked by alpha-methyl D-mannoside and alpha-methyl d-glucoside. Similarly the inhibitory effect of wheat-germ agglutinin was reversed by N-acetyl-D-glucosamine. Pretreatment of ovarian cells with concanavalin A or wheat-germ agglutinin had no effect on protein synthesis in the ovary as monitored by [3H]proline incorporation studies. Concanavalin A and wheat-germ agglutinin did not affect steroid production in response to dibutyryl cyclic AMP and 8-bromo cyclic AMP, indicating that the inhibitory action of lectin was occurring at a step before cyclic AMP formation. Lectins specific for L-fucose, D-galactose and N-acetyl-D-galactosamine, gorse seed agglutinin, peanut agglutinin and Dolichos biflorus agglutinin respectively, did not interfere with gonadotropin-induced cyclic AMP and progesterone responses. The present studies suggest that gonadotropin receptors may be glycoprotein in nature or closely associated with glycoprotein structures with the carbohydrate chain containing N-acetyl-D-glucosamine, mannose and possibly N-acetylneuraminic acid.

Inhibition of H+ secretion by lectins in turtle bladder: role of a cell type on acidification

1985 ◽  
Vol 248 (5) ◽  
pp. R584-R594
Author(s):  
D. M. Potter ◽  
J. A. Arruda
Keyword(s):  
Concanavalin A ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Granular Cell ◽  
Cell Fraction ◽  
Dependent Manner ◽  
O2 Consumption ◽  
Cell Type ◽  
Double Labeling ◽  
Morphological Studies

Because certain lectins have been shown to bind to the intercalated cell of the cortical collecting tubule, we investigated the effect of concanavalin A and wheat germ agglutinin on urinary acidification in isolated turtle bladders. After addition to the mucosal but not serosal fluid, concanavalin A and wheat germ agglutinin decreased H+ secretion in a dose-dependent manner, and these effects were specifically inhibited by the competitive antagonists of concanavalin A (alpha-methyl-D-mannoside) and of wheat germ agglutinin (N-acetylglucosamine). Concanavalin A decreased H+ secretion by decreasing both the proton motive force and the active conductance of protons. Although electroneutral HCO3 secretion was not inhibited by either lectin, Na transport was decreased by 18 and 25%, respectively, after concanavalin A and wheat germ agglutinin. Concanavalin A failed to inhibit O2 consumption by the granular cell fraction but significantly inhibited O2 consumption by the carbonic anhydrase rich cell fraction. Morphological studies utilizing peroxidase or fluorescein-labeled concanavalin A showed that concanavalin A stained one cell type and that this staining was specific since it could be blocked by the competitive antagonist alpha-methyl-D-mannoside. Studies utilizing double labeling with fluorescein concanavalin A and acridine orange suggested that both probes stain the same cell type. The data strongly suggest that concanavalin A interacts specifically with the cell responsible for H+ secretion.

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