Showing papers by "Peter F. Billingsley published in 1999"

Blood digestion in the mosquito, Anopheles stephensi : the effects of Plasmodium yoelii nigeriensis on midgut enzyme activities

Abstract: Midgut proteases contribute to the success or failure of Plasmodium infection of the mosquito. This paper examines the reciprocal effect of Plasmodium yoelii nigeriensis on midgut trypsin, chymotrypsin, aminopeptidase and carboxypeptidase in the mosquito Anopheles stephensi. The total protein ingested and the rate of protein digestion were unaffected by the parasite, but more protein was ingested at the first than the second bloodmeal. All peptidases were unaffected by the presence of the parasite during the first gonotrophic cycle, when ookinetes were penetrating the midgut. In the second gonotrophic cycle, trypsin and chymotrypsin were unaffected by growing oocysts, but aminopeptidase activity was reduced in the midguts of infected mosquitoes. Chymotrypsin activity was depressed and aminopeptidase activity elevated during the second gonotrophic cycle. Plasmodium infection has a negligible effect on bloodmeal digestion and does not limit the availability of the protein for egg production. The significance of changes in aminopeptidase activity when oocysts are present is discussed.

Detection and characterization of a mannan-binding lectin from the mosquito, Anopheles stephensi (Liston)

Abstract: Two lectins from the serum of the mosquito, Anopheles stephensi (Liston), with distinct characteristics, were detected by agglutination of various animal erythrocytes. The lectins were developmental stage-specific and/or sex-related. One adult female-specific lectin was identified as mannan-specific, and named mosquito mannan-binding lectin (MBL). MBL cross-reacted immunologically with antibodies against a previously characterized cockroach lectin, Blaberus discoidalis lectin (BDL1), and its activity was almost completely blocked by the antibodies. Mosquito MBL agglutinated erythrocytes from human, sheep, goat and rabbit, but not chicken or mouse, and agglutination was inhibited by mannan and nitrophenol-modified sugar derivatives, but not by simple sugars. Using affinity chromatography with immobilized mannan on Sepharose 6B, the mosquito MBL was partially purified. Purified mosquito MBL shared biochemical properties with BDL1, containing two subunits of molecular mass of 28 and 30 kDa under reducing conditions in SDS/PAGE. Its activity is dependent on Ca2+, and it is stable at pH 7–9 and at temperatures less than 30 °C.