Multiple mating and sperm displacement in a natural population of Drosophila melanogaster

Summary Mother-offspring data for alcohol dehydrogenase genotypes of a vineyard cellar population of D. melanogaster are best explained by a model that allows 21% of females in the population to mate twice with an 83% level of sperm displacement. A population model with multiple mating and sperm displacement is examined theoretically. A formula for the effective population size is derived under this model. Multiple mating increases the effective population size relative to single mating.     

A proton nuclear magnetic resonance study of gamma-glutamyl-amino acid cyclotransferase in human erythrocytes

Spin-echo NMR spectroscopy was shown to be a reliable technique for the monitoring of the in situ cleavage of gamma-Glu-Ala by gamma-glutamyl-amino acid cyclotransferase in whole erythrocytes and hemolysates. Of particular importance was the difference in chemical shifts between peptide resonances and those of the constituent amino acids. Using lysates of varying dilution, it was shown that the specific activity of the enzyme was not concentration-dependent, thus suggesting a lack of cytosolic low-molecular-weight-effectors or enzyme dissociation. Furthermore, the initial velocities of the reaction as a function of substrate concentration obeyed Michaelis-Menten kinetics with a Km = 2.0 +/- 0.3 mmol/l and Vmax = 137 +/- 7 mmol/h/l of cell water in 1H2O medium. Similar analysis in 2H2O medium revealed a solvent kinetic isotope effect of 1.9 +/- 0.4 at low substrate concentrations. The implications of this observation for the mechanism of the reaction are discussed. Cleavage of the peptide by a suspension of intact erythrocytes was at a rate 300 times less than the corresponding lysate flux, thus indicating the rate limitation by transport in the coupled system.     

Inhibitory effect of ammonium chloride and chloroquine on the entry of the toxic lectin modeccin into HeLa cells

Ammonium chloride and chloroquine protected a variety of cell lines against diphtheria toxin and the toxic lectin modeccin. Experiments where the ability of antibody to neutralize the toxin was measured indicate that in the presence of ammonium chloride and chloroquine, modeccin remains at the cell surface and that the two compounds inhibit the uptake of modeccin into the cytoplasm. A cell line tolerating increased concentrations of modeccin was not protected against modeccin by ammonium chloride or chloroquine, whereas the compounds did protect these cells against diphtheria toxin.     

III. Serum and sputum immunoglobulin E levels in respiratory diseases in adults

Using a solid-phase radioimmunoassay, serum IgE level was determined in 46 normal subjects, 53 patients with bronchial asthma, 44 patients with chronic bronchitis and / or emphysema, and 19 patients with restrictive lung disease. Sputum IgE was measured simultaneously in 51 of the subjects. The range of serum IgE concentration in the normal subjects was wide. It varied between 15 and 750 ng/ml with a mean of 135 ng. Asthmatic patients had significantly higher levels of serum IgE with a mean of 579 ng/ml, but only 30% fell outside the normal 95% confidence limits. Patients with chronic bronchitis, emphysema and restrictive lung diseases had normal IgE levels. There was a significant correlation between serum and sputum IgE levels.