摘要:

AbstractTaxol promotes microtubule (MT) assembly in vitro and induces the reorganization of the cytoskeleton into unusual MT arrays in cultured cells. The possibility that taxol also has an indirect effect on intermediate filaments (IF) was investigated. In baby hamster kidney (BHK‐21) and human skin (ENSON) fibroblasts treated with 1–10 μM taxol for 1–24 h, the drug induces changes which are similar to those produced by colchicine. These include a loss of major cellular extensions, a redistribution of organelles to a perinuclear location, and an inhibition of locomotion. Saltatory particle movements are not inhibited, however. Ruffling and filopod formation continue, indicating that cells are viable up to 24 h.Polarized light microscopy of living fibroblasts treated with taxol reveals the presence of perinuclear birefringent material which has been examined by immunofluorescence. In control cells, IF and MT radiate from a juxtanuclear region and extend to the cell periphery. In taxol‐treated cells, MT and IF are excluded from cell margins, forming large central bundles.In the epithelial cell lines PtK2and PAM, the keratin system of IF does not become redistributed; in PtK2, however, a second fibroblastlike system of IF does become redistributed to a perinuclear position during taxol treatment.Ultrastructural analyses show that taxol‐treated fibroblasts contain parallel arrays of cross‐bridged MT‐IF as well as bundles of MT exclusive of IF. Epithelial cells contain a predominance of IF‐free MT bundles which are organized into hexagonally packed arrays. In these bundles MT frequently exhibit hooks or other incomplete MT profiles and are linked by fila

ISSN:0271-6585    

DOI:10.1002/cm.970030402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe outcome of contact interactions involving neurons and nonneurons varies depending on the cell types involved. When neuronal growth cones from either ciliary (motor) or dorsal root (sensory) ganglia directly contact the lamellipodium of an embryonic heart fibroblast, both neurite elongation and fibroblast locomotion are inhibited. This occurs in spite of the fact that cell‐surface activity in both cells continues unabated. Such contact inhibition is not observed when homologous ganglionic nonneurons are involved in the interaction. In fact, these cells become intimately associated with growth cones and/or neuritic shafts as a result of the contact. The detailed nature of the respose to contact exhibited by nerves and nonnerves varies not only with cell type but also with the portion of the cell involved in the contact. Growth cone filopodia tend to actively palpate the fibroblast surface, whereas spread regions, termed “veils,” form areas of apposition with fibroblast lamellipodia. This latter situation resembles the “typical” contact inhibition of locomotion that occurs following embryonic heart fibroblast‐fibroblast interactions. Growth cones also frequently exhibit contact guidance when interacting with nonruffling lateral surfaces of heart

ISSN:0271-6585    

DOI:10.1002/cm.970030403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractCiliary axonemes from Tetrahymena extracted by KCl to remove the dynein arms reveal an orderly array of interdoublet links connecting adjacent A‐B or A‐A subfibers. The links repeat every 96 nm at a stable site on the A subfiber positioned near the bases of radial spokes 2 and 3. Both links and radial spokes are in lateral register across the nine successive doublets of unbent axonemes. In contrast, bent axonemes or those reactivated by ATP to undergo partial sliding disintegration exhibit systematic displacement of the interdoublet links. The links show no evidence of having elastic or other extendable properties and, therefore, must have undergone intermittent attachment with nonstructural binding sites on the adjacent subfiber. These observations suggest a more dynamic role for the interdoublet links in ciliary motion than previously has been envisio

ISSN:0271-6585    

DOI:10.1002/cm.970030404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe locomotion of C. elegans spermatozoa resembles, in many respects, the crawling movements of other eukaryotic cells. However, these sperm contain surprising little actin, which plays no apparent role in this cell's motility. Electron microscopy has revealed that crawling spermatozoa retain a strict morphological polarity so that the organelle‐filled cell body is separated from the pseudopod by an array of cytoplasmic laminar membranes. When sperm crawl only the pseudopod contacts the substrate; the cell body is either pulled behind or carried on top of the rear portion of the pseudopod. Fingerlike projections which extend forward from the leading edge of the pseudopod initiate contact with the substrate. The underside of the pseudopod exhibits areas of close (40 nm separation) membrane‐substrate association with intervening areas of wide (up to 300 nm) membrane‐substrate gaps. The pseudopod cytoplasm contains 2‐nm filaments but no filamentous actin has been observed. These 2‐nm filaments were detected in thin sections of crawling cells and in negative‐stained remnants of spermatozoa disrupted by either hypotonic buffer on Triton X‐100. The filaments are found both free in the cytoplasm and closely associated with the cytoplasmic face of the plasma membrane and are usually oriented along the long axis of the cell. Neither the identity nor the function of these filaments has been established although their location and orientation suggest that they may be involved in generati

ISSN:0271-6585    

DOI:10.1002/cm.970030405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractChanges in the state of polymerization of actin and phosphorylation of myosin have been observed in polymorphonuclear leukocytes (PMNs) soon after the addition of the chemotactic peptide N‐formylnorleucylleucylphenylalanine. At a time when the cells are observed to extend many ruffles or lamellipodia from their surface, the fraction of the cellular actin present in a monomeric form is decreased by about 25% as assayed by the ability of the G‐actin to inhibit DNAase. These changes are temporally correlated with an increase in the staining by nitrobenzooxadiazole (NBD)‐phallacidin, a probe that binds F‐actin selectively. The NBD‐phallacidin staining is observed in the surface ruffles. When the peptide concentration is decreased by addition of a tenfold excess of buffer, cells withdraw their surface ruffles and form blebs. These changes correlate with an increase in the G‐actin levels detected with the DNAase inhibition assay. An increase in phosphorylation of the 20,000‐dalton light chain of myosin is also observed in leukocytes stimulated by addition of chemotactic peptide. These observations of changes in cytoskeletal proteins of PMNs provide a beginning for further studies on the regulation of cell motility by chemot

ISSN:0271-6585    

DOI:10.1002/cm.970030406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

ISSN:0271-6585    

DOI:10.1002/cm.970030401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY