Lavender is a mutation of chick neural-crest-derived melanocytes showing dilute feather pigmentation. This defect, previously attributed to a lack of attenuation of dendrites, was found to be due to a defect in melanosome translocation. The mutant phenotype, of melanincongested perikarya and pigmentless dendrites is expressed both in vivo and in vitro. Studies with colcemid and cytochalasin B s...

Human endothelial cells prepared from unbilical cords are characterized in parallel by electron microscopy and indirect immunofluorescence microscopy using specific antibodies against different classes of intermediate-sized filaments. The strongly developed, loose bundles of intermediate-sized filaments typically found in these cells are not decorated by antibodies against prekeratin or antibod...

Actin filaments and microtubules lengthen and shorten by addition and loss of subunits at their ends, but it is not known whether this is also true for intermediate filaments. In fact, several studies suggest that in vivo, intermediate filaments may lengthen by end-to-end annealing and that addition and loss of subunits is not confined to the filament ends. To test these hypotheses, we investig...

In the developing aorta, endothelial cell connecting filaments extend from the abluminal surface of the endothelial cell to the subjacent elastic lamina. The connecting filaments are in alignment with intracellular stress fibers and are oriented parallel to the direction of blood flow. In the present study, the composition of the endothelial cell connecting filaments was investigated by indirec...

Extraction of SC-1 cells (African green monkey kidney) with the detergent Triton X-100 in combination with stereo high-voltage electron microscopy of whole mount preparations has been used as an approach to determine the mode of action of cytochalasin D on cells. The cytoskeleton of extracted BSC-1 cells consists of substrate-associated filament bundles (stress fibers) and a highly cross-linked...

We characterize aspects of the conformation and dynamic state of RecA filaments when bound to dsDNA that are specifically linked to the presence of the second of the two bound DNA strands. Filaments bound to dsDNA exhibit a facile exchange between free and bound RecA monomers or oligomers in the filament interior that is not seen on ssDNA. The RecA mutant K72R, which binds but does not hydrolyz...

The extraction of isolated vertebrate smooth muscle cells at high and low ionic strength yields cell ghosts which are seen in the electron microscope to be composed of a complex network of 10-nm filaments, together with residual actin. After SDS-gel electrophoresis of the cell ghosts only 2 bands may be recognized, one corresponding to actin and the other migrating at about 55 000 mol. wt that ...

Host cell entry by Toxoplasma gondii depends critically on actin filaments in the parasite, yet paradoxically, its actin is almost exclusively monomeric. In contrast to the absence of stable filaments in conventional samples, rapid-freeze electron microscopy revealed that actin filaments were formed beneath the plasma membrane of gliding parasites. To investigate the role of actin filaments in ...

The Arp2/3 complex is a stable assembly of seven protein subunits including two actin-related proteins (Arp2 and Arp3) and five novel proteins. Previous work showed that this complex binds to the sides of actin filaments and is concentrated at the leading edges of motile cells. Here, we show that Arp2/3 complex purified from Acanthamoeba caps the pointed ends of actin filaments with high affini...

Heavy meromyosin (HMM) decoration of actin filaments was used to detect the polarity of microfilaments in interphase and cleaving rat kangaroo (PtK2) cells. Ethanol at -20 degrees C was used to make the cells permeable to HMM followed by tannic acid-glutaraldehyde fixation for electron microscopy. Uniform polarity of actin filaments was observed at cell junctions and central attachment plaques ...