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1 May 2002 Histochemical Localization of N-Acetyl-Galactosamine in the Midgut of Lutzomyia longipalpis (Diptera: Psychodidae)
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The binding of lectins to the midgut of the female sand fly Lutzomyia longipalpis (Lutz & Neiva) was investigated using lectin-gold conjugates. Midguts from laboratory-reared flies provided fructose solution and/or blood fed on hamster were dissected at 6, 24, and 48 h and at 5 and 7 d after feeding. Before examination by transmission electron microscopy, each midgut was sectioned, incubated with lectins from four sources (Canavalia ensiformis [ConA], Helix pomata agglutinin [HPA], peanut agglutinin [PNA], and wheat germ agglutinin [WGA]), then conjugated with colloidal gold. Only HPA, which is specific for N-acetyl-galactosamine (GalNAc), bound to the midgut. Binding sites were cytoplasmic secretory granules and microvilli throughout the length of the midgut epithelium. Binding occurred in sand flies fed fructose as well as in flies receiving a blood meal. The presence of GalNAc on the midgut microvilli of sand flies before, during, and after blood feeding indicates this amino-sugar is not altered by digestion. As a structural component, GalNAc may represent a terminal on a receptor molecule. The failure of the sand fly peritrophic matrix to bind WGA by N-acetyl-glucosamine may be caused by the complex composition of the membrane, which renders N-glycan inaccessible to the lectin-gold conjugate.

L. G. Evangelista and A. C R. Leite "Histochemical Localization of N-Acetyl-Galactosamine in the Midgut of Lutzomyia longipalpis (Diptera: Psychodidae)," Journal of Medical Entomology 39(3), 432-439, (1 May 2002).
Received: 27 March 2001; Accepted: 1 August 2001; Published: 1 May 2002

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