cytochalasin-b and Laryngeal-Neoplasms

Adherence of Aeromonas caviae to HEp-2 and Caco-2 cell monolayers was investigated with 24 clinical isolates. Growth phase, temperature, multiplicity of infection and length of incubation affected adherence. Treatment of the bacteria with trypsin, sodium metaperiodate, mechanical shearing and the addition of cytochalasin B and cycloheximide to the monolayer significantly reduced the adherence capabilities of the strains investigated. The use of chloramphenicol to inhibit protein synthesis reduced the adhesive capabilities of bacteria grown in liquid medium and those subjected to mechanical shearing. Light microscopy, scanning and transmission electron microscopy were employed in the investigation of bacteria-bacteria and bacteria-monolayer interactions and indicated similarities with the aggregative adherence patterns of the Enterobacteriaceae. The presence of extracellular bacterial appendages and their correlation with increased adhesive capacity may indicate a role in the process of adherence.

Topics: Aeromonas; Anti-Bacterial Agents; Bacterial Adhesion; Caco-2 Cells; Carcinoma, Squamous Cell; Chloramphenicol; Cycloheximide; Cytochalasin B; Humans; Laryngeal Neoplasms; Microscopy, Electron, Scanning; Mitogens; Periodic Acid; Protein Synthesis Inhibitors; Stress, Mechanical; Temperature; Trypsin; Tumor Cells, Cultured

Ammonium chloride (4 times 10-3 M) rendered HEp-2 monolayers completely insensitive to the action of diphtheria toxin, as measured by de novo protein synthesis. Total protection was observed even with large amounts of toxin (400 minimum lethal doses/ml). Ammonium chloride did not reduce toxicity by direct action on the protein, nor did it prevent the adsorption of toxin to the cell membrane. Although the ammonium salt did not block the initial interaction between cell and toxin, it did maintain the toxin at a site amenable to neutralization with antitoxin. Surface-adsorbed toxin was inactivated by cellular enzymes or alternatively was desorbed from the membrane during a 12-h incubation in the presence of ammonium chloride. In addition, ammonium chloride provided protection to both toxin-sensitive guinea pig peritoneal macrophages and a partially toxin-resistant strain of HEp-2 cells. Sodium arsenite was effective in protecting cell monolayers from the action of diphtheria toxin; unlike ammonium chloride, its action was not dependent upon continued incubation with cells during exposure to toxin. Inhibitors of energy metabolism abolished toxin action either totally (sodium fluoride) or partially (dinitrophenol and sodium cyanide). Inhibitors of cellular proteases, on the other hand, did not modify toxin activity. The ability of several modifiers of membrane function to alter expression of toxicity for HEp-2 cells was also examined. One compound known to enhance endocytic activity, Tuftsin, had no effect, whereas poly-L-ornithine provided partial protection. Of the two compounds known to alter membrane fluidity, cytochalasin B provided partial protection for HEp-2 cell cultures, whereas colchicine had no effect. Agents that bind to sulfhydryl groups on the cell surface had no apparent effect on toxicity, suggesting that the initial toxin-cell interaction does not involve sulfhydryl groups. Those compounds that provide virtually full protection against the action of diphtheria toxic on cell monolayers (i.e., ammonium chloride, sodium fluoride, and sodium arsenite) had no inhibitory effect on the in vitro enzyme activity associated with fragment A of the toxin.

Topics: Ammonium Chloride; Antimetabolites; Arsenicals; Cell Line; Cell Membrane; Culture Techniques; Cytochalasin B; Diphtheria Antitoxin; Diphtheria Toxin; Dithiothreitol; Drug Resistance; Enzyme Inhibitors; Epithelial Cells; Glutathione; Humans; Laryngeal Neoplasms; Leucine; Macrophages; NADP; Neutralization Tests; Peptide Hydrolases; Pyridines; Tritium

Topics: Animals; Burkitt Lymphoma; Carcinoma; Cell Line; Cells, Cultured; Chromosomes; Cricetinae; Cytochalasin B; Embryo, Mammalian; Humans; Indoles; Kidney; Laryngeal Neoplasms; Lung; Mitosis; Mitosporic Fungi; Mouth Neoplasms; Polyploidy