Fluid excretion by adult Aedes aegypti mosquitoes

Only clear cloacal fluid was eliminated during the first 30–60 min after emergence of feeding on human blood. Neither meconium nor blood was voided. More liquid was excreted after withdrawing blood than after ecdysis, but the pattern of emission was the same, in that fluid was ejected rapidly only or mostly over the first 10–15 min after these events. Diuresis was not exhibited after adults fed on either sucrose or fructose. Injury prevents the release of the diuretic hormone.     

A prestaining method for the quantitative assay of proteins on polyacrylamide gels

Dyes have been synthesised¹, which make it possible to prestain proteins prior to electrophoresis on polyacrylamide gels. After discussing the criteria which have to be fulfilled by the dyes, their method of application is described. The method has been tested on a number of selected acidic and basic proteins and also on peptide obtained by the digestion of bovine serum albumin with cyanogen bromide. Excellent reproducibility, stoichiometry and a sensitivity of 0.2 μg with some proteins has been obtained.     

A computer program for the calculation of sedimentation coefficients and molecular weights of nucleic acids

A procedure is described for the purification of nuclei and identification of chromatin proteins in transformed epithelial cell lines from mammalian bladder and salivary gland. Nuclear purification was performed by homogenization, in hypotonic buffer containing polyamines to stabilize the nuclear structure, followed by 0.1–0.2% Triton X-100 washing and centrifugation through 2.2 m sucrose. Chromatin was liberated from nuclei by freeze-thawing in hypotonic buffer and the chromatin proteins were extracted with 7 m urea/3 m NaCl. The chromatin proteins were identified using NEPHGE two-dimensional electrophoresis and fluorographic autoradiography. This procedure enabled detection of histones and a range of basic nonhistone chromatin proteins, following cell culture in the presence of low levels of l-(4,5-³H)leucine.     

Partial purification and characterization of cyclic AMP phosphodiesterases from Funaria hygrometrica

Natural-abundance ¹³C NMR spectroscopy at 15.04 MHz has been used to examine the effects of pH, calcium, and lanthanide ions on the polypeptide cardiac stimulant Anthopleurin-A in aqueous solution. The carboxyl resonance from the aspartic acid residue not observed in a previous study (R. S. Norton and T. R. Norton, 1979, J. Biol. Chem.254, 10220–10226) has been identified and an apparent pK_a of 3.4 obtained. More accurate estimates have been derived for the apparent pK_a values of the two histidine residues. Binding of Ca²⁺ ions has been found by equilibrium dialysis and ¹³C NMR to be weak (K_d > 0.1 M). The interaction with lanthanide ions is slightly stronger, but binding occurs at the C terminus as well as at a site involving one or both of the aspartate carboxylate groups. These results suggest that possible Anthopleurin-A-induced calcium translocation in the myocardial cell is a secondary effect. The interaction of Anthopleurin-A with lipid monolayers has also been examined. Binding occurs to neutral and zwitterionic lipids, but is stronger with negatively charged lipids, particularly cardiolipin. This interaction is also influenced by the presence of Ca²⁺ ions. The implications of these results for the mechanism of action of this polypeptide are discussed.