The cytoskeletal network of cells is postulated to play a role in the signal transduction pathways of growth promoting stimuli. We show here that cytoskeletal active drugs modulate the mitogenic signal transduction pathway of the tumor promoter TPA in 3T3-L1 cells. Compounds which act on microtubules (vinblastine sulfate) and microfilaments (cytochalasin B) have opposite effects on DNA synthesi...

D-Glucose entry into erythrocytes from adult dolphins (Tursiops truncatus) was rapid, showed saturation at high substrate concentrations, and demonstrated a marked stimulation by intracellular D-glucose. Kinetic parameters were estimated from the concentration dependence of initial rates of tracer entry at 6 degrees C: for zero-trans entry, Michaelis constant (K(m)) was 0.78 +/- 0.10 mM and max...

The presence of a reactive exofacial sulfhydryl on the human erythrocyte hexose carrier was used to test several predictions of the alternating conformation or one-site model of transport. The cell-impermeant glutathione-maleimide-I (GS-Mal) irreversibly inhibited hexose entry by decreasing the transport Vmax. This effect was potentiated by phloretin and maltose but decreased by cytochalasin B,...

To compare the effects of cytochalasins on the cellular level with those on the molecular level, 24 cytochalasins, 20 natural compounds and 4 derivatives, were used. The following effects were tested for each of 24 cytochalasins; (a) four high dose (2-20 muM) effects on the cellular level: rounding up of fibroblastic cells, contraction of actin cables, formation of hairy filaments containing ac...

We used electron microscopy to measure the effects of cytochalasins, phalloidin, and pH on the rates of elongation at the barbed and pointed ends of actin filaments. In the case of the cytochalasins, we compared the effects on ATP- and ADP-actin monomers. Micromolar concentrations of either cytochalasin B (CB) or cytochalasin D (CD) inhibit elongation at both ends of the filament, about 95% at ...

Mature bovine oocytes were activated with 7% ethanol followed by cytochalasin B or D treatment. Most oocytes extruded a second polar body and formed one pronucleus when treated with 7% ethanol alone [35/43 (81%)]. With ethanol followed by cytochalasin B or D, overall activation frequency was 70% (309/441), with activated oocytes containing two pronuclei. The cleavage rate was not significantly ...

Cytochalasin B at concentrations of 1, 5, 10, 15, 20, or 40 microgram/ml was continuously exchange-perfused into the eyes of nine living Macaca mulatta monkeys while intraocular pressure (IOP) was maintained at 25 mm Hg for 30 min. Pressures were then slowly reduced to 4 mm Hg to permit blood to reflux into Schlemm's canal as a tracer, and the eyes were fixed while maintained at 4 mm Hg IOP. Ti...

The size increase of skin epithelial cells during aging is well-known. Here we demonstrate that treatment of aging cells with cytochalasin B substantially decreases cell size. This decrease was demonstrated on a mouse model and on human skin cells in vitro. Six nude mice were treated by topical application of cytochalasin B on skin of the dorsal left midsection for 140 days (the right side serv...

Homology modeling and scanning cysteine mutagenesis studies suggest that the human glucose transport protein GLUT1 and its distant bacterial homologs LacY and GlpT share similar structures. We tested this hypothesis by mapping the accessibility of purified, reconstituted human erythrocyte GLUT1 to aqueous probes. GLUT1 contains 35 potential tryptic cleavage sites. Fourteen of 16 lysine residues...

Native differences in cell shape and plasma membrane organization in contact-inhibited and transformed cells and the effects of cytochalasin B and colchicine on these cells have been examined by scanning electron microscopy and freeze fracture-electron microscopy. Confluent BALB/c 3T3 cells show a flat, polygonal shape with limited cell overlapping, some microvilli, and plasma membranes with an...