Modification of the DNA content in translocated regions of Drosophila polytene chromosomes.

The DNA content of translocated polytene chromosome regions in Drosophila melanogaster is affected by heterochromatic position effect. Microdensitometric studies on wm258-21 translocation heterozygotes showd (Hartmann-Goldstein and Cowell, 1976; Cowell and Hartmann-Goldstein, 1980) that band region 3D1-E2, adjacent to the breakpoint, contained less DNA than the homologous non-translocated region whereas the neighbouring 3C1-10 region contained more DNA than its non-translocated counterpart. In the nuclei selected for measurement the translocated X chromosome was morphologically euchromatic, but both regions undergo heterochromatisation in other nuclei within the same salivary gland.

Contrasting response of euchromatin and heterochromatin to translocation in polytene chromosomes of Drosophila melanogaster.

Studies on Feulgen-DNA content in the polytene chromosomes of D. melanogaster T(1:4)wm258-21 heterozygotes showed that when the euchromatic region 3D1-E2 is located next to the heterochromatic breakpoint it contains less DNA than in the non-translocated homologue (Hartmann-Goldstein and Cowell, 1976). In contrast to the region adjacent to the breakpoint, region 3C1-10, which contains intercalary heterochromatin, shows more DNA in the translocated than in the non-translocated chromosome.

Intracellular localization of the dermonecrotic toxin of Bordetella pertussis.

Localization of the heat-labile dermonecrotic toxin of Bordetella pertussis strain 114 grown in chemically defined Stainer-Scholte medium was studied by using skin reaction in 4-day-old suckling mice as the assay for toxin. Through log phase and into stationary phase of growth the toxin was cell associated and not detected in the culture supernatant. Only about 4% of the activity present in a suspension of lysed cells was detected in a suspension of whole cells, and the dermonecrotic activity was not released by subjecting whole cells to osmotic shock, a procedure that releases proteins from the periplasmic space of many gram-negative bacteria.

Alteration by cereolysin of the structure of cholesterol-containing membranes.

When erythrocyte membranes were treated with cereolysin, negatively stained and examined by electron microscopy, ring and arc-shaped structures were observed in the membrane. The outside diameter of the rings varied from 33 to 50 nm with a border thickness of 6.7 to 8.

Antigenic relationships among thiol-activated cytolysins.

Cereolysin, streptolysin O, and perfringolysin O formed precipitin lines that completely fused when reacted with horse antitetanolysin by Ouchterlony immunodiffusion and formed precipitin lines that showed either partial or complete fusion when diffused against horse antistreptolysin O or antiperfringolysin O.

Purification of cereolysin and the electrophoretic separation of the active (reduced) and inactive (oxidized) forms of the purified toxin.

Cereolysin was purified to apparent homogeneity by using ammonium sulfate fractionation, hydrophobic chromatography with AH-Sepharose, isoelectric focusing, and gel filtration. The active form of the toxin had an isoelectric point of 6.6, and the molecular weight of the protein was about 55,500 as judged by sodium dodecyl sulfate-gel electrophoresis, gel filtration, and gel electrophoresis using various concentrations of acrylamide.

Energetics of glycylglycine transport in Escherichia coli.

The transport system for glycylglycine in Escherichia coli behaves like a shock-sensitive transport system. The initial rate of transport is reduced 85% by subjecting whole cells to osmotic shock, and glycylglycine is not transported by membrane vesicles. The energetics of transport was studied with strain ML 308-225 and its mutant DL-54, which is deficient in Ca(2+)- and Mg(2+)-stimulated adenosine 5'-triphosphatase (EC 3.