(1961). Amylase was measured by determining the appearance of reducing groups ( Noelting and Bernfeld, 1948) in 50 mM glycine–NaOH buffer
at pH 9.5 with 0.5% (w/v) starch as substrate in the presence of 10 mM NaCl. Carboxypeptidase A was determined using 15 mM N-carbobenzoxy-glycyl-l-phenylalanine (ZGlyPhe) in 50 mM Tris–HCl learn more buffer pH 8 in the presence of 50 mM NaCl ( Ferreira et al., 1994). Cellobiase and maltase were assayed according to Dahlqvist (1968), using 7 mM cellobiose and 7 mM maltose in 50 mM sodium citrate–phosphate buffer pH 7.0 and pH 5.0, respectively. Incubations were carried out at 30 °C for at least four different time periods, and initial rates of hydrolysis were calculated. All assays were performed under conditions that the product was proportional to enzyme concentration and to incubation time. Controls without
enzyme and others without substrate were included. One enzyme unit is the amount that hydrolyses 1 μmol of substrate (or bond) per min. Enzyme activities are expressed in milli units (mU). Micropocrine vesicles preparations Apoptosis inhibitor were centrifuged and the resulting pellets and midgut tissues were then fixed in 2.5% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) and picric acid for 2 h. The samples were post-fixed in 1% osmium tetroxide, then dehydrated in an ethanol series and embedded in LR White acrylic resin (Electron Microscopy Sciences, Ft Washington, USA), cut Urease into ultrathin sections, stained with uranyl acetate and lead citrate (Reynolds, 1963) and, finally, examined in a Zeiss EM 109 electron microscopy. The pre-immune blood of all the rabbits used to raise antibodies was non-reactive against proteins of insect midgut and Escherichia coli XL1-Blue. Antibodies
were raised as follows. One mL of an apocrine vesicle protein preparation were dispersed with an equal volume of Freund’s complete adjuvant. This suspension (containing 5 mg of the microapocrine vesicle proteins) was then injected into the inguinal nodes of a rabbit. After 4 weeks, another injection of the same sample with 4 mg was administered, but now with Freund’s incomplete adjuvant. After 7 days the rabbit was bled and antibodies were purified by precipitation with ammonium sulfate as detailed elsewhere ( Ferreira et al., 2007). The resulting antiserum was stored at −20 °C. Antibody production and specificity was checked on Western blots after SDS–PAGE. SDS–PAGE of samples was carried out in 12% (w/v) polyacrylamide gels containing 0.1% (w/v) SDS, on a discontinuous pH system (Laemmli, 1970), using BioRad (USA) Mini-Protein II equipment, as previously described (Ferreira et al., 2007). Immunoblotting was performed as follows. After SDS–PAGE, the proteins were electrophoretically transferred onto a nitrocellulose membrane filter (pore size 0.45 mm; BioRad, USA) (Towbin et al., 1979). The transfer efficiency was evaluated by observing the pre-stained molecular weight markers (BioRad or Sigma, USA).