摘要:

AbstractWe used a monoclonal antibody specific for vimentin from human fibroblasts to stain whole mounts ofDrosophilaembryos. In immunofluorescence observations this antibody cross‐reacts with an antigenic determinant localized throughout mitosis at the nuclear boundary. Double fluorescence observations with the Rb188 antibody that specifically recognizes a centrosomal protein of theDrosophilaembryo [Whitfield et al., 1988] showed that the anti‐vimentin antibody cross‐reacts with an antigen localized in the centrosomal r

ISSN:0886-1544    

DOI:10.1002/cm.970190102

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

年代:1991

数据来源: WILEY

摘要:

AbstractLY195448 is an experimental drug that blocks cells at metaphase (Boder et al.:Microtubules and Microtubule Inhibitors 1985: 353–361, 1985). A 4 hour exposure of NRK cells to a drug concentration of 46 μM (15 μg/ml) increased the number of mitotic cells in the population from 4.9% to 18.5%. Examination of treated cells by immunofluorescence showed increased numbers of cells blocked at prometaphase, with short microtubules extending from the spindle pole to the kinetochores. The cytoskeleton of interphase cells remained intact at these concentrations. However, the number of microtubules appeared to be reduced, and those that remained appeared kinkier and curled, particularly toward the periphery of the cells. When cytoskeletal microtubules of NRK cells were depolymerized with nocodazole, they reassembled within minutes of transfer to drug‐free media. However, nocodazole‐treated cells transferred to fresh media containing 15 μg/ml of LY 195448 required 2‐3 times longer to reassemble cytoplasmic microtubules. Previously isolated Chinese hamster ovary cell microtubule mutants resistant to either taxol or Colcemid were tested for cross‐resistance to this drug. Cell lines resistant to the depolymerizing drug Colcemid exhibited increased resistance to LY 195448 compared to wild‐type cells, whereas taxol resistant cell lines were more sensitive. Of eleven newly isolated mutant CHO cell lines selected for increased resistance to LY 195448, seven exhibited an altered β‐tubulin protein by two‐dimensional polyacrylamide gel electrophoresis. These 11 cell lines also showed a heterogenous pattern of resistance to several microtubule‐active drugs. These data demonstrate that LY 195448 is cytotoxic to mammalian cells because it inhibits microtubule assembly, most likely through a direct int

ISSN:0886-1544    

DOI:10.1002/cm.970190103

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

年代:1991

数据来源: WILEY

摘要:

AbstractForces that elongate the spindle during anaphase B of mitosis might be generated in the asteis, in the spindle, or in both. In the fungusNectria haematococca, it has already been shown that the asters pull on the spindle pole bodies (SPBs) through‐out anaphase B. In this study, we used computerized video motion analysis to characterize brief episodes of spindle bending and straightening to find out if such bending is caused by spindle pushing forces. In three episodes there were two distinct components of spindle bending and straightening: one spanning the entire episode and comprising spindle elongation and another, superimposed on the first, involving a shortening of the distance between the SPBs. In a fourth episode, only spindle elongation was involved. All four spindles elongated rapidly while bending and underwent net growth during the overall bending‐straightening episode at an average rate of 4.2 μm/min. The path of one aster of a fifth mitotic apparatus was blocked by a large, occluding vacuole. This obstacle caused the migration of the mitotic apparatus to stop, resulting in a long (25 sec) episode of spindle curving and bending, usually without any substantial reduction in the distance between the SPBs as well as a marked reduction (from 4.7 to 0.65 μm/min) in the rate of spindle elongation. The results provide evidence that spindle pushing forces are active in vivo during anaphase B inN. haematococcaand that they, along with astral pulling forces, help to elongate the spindle at a mostly constant rate. This is the first demonstration of both kinds of spindle elongation forces in the same org

ISSN:0886-1544    

DOI:10.1002/cm.970190104

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

年代:1991

数据来源: WILEY

摘要:

AbstractActin localization during stomatal complex formation in rye leaf epidermis was compared by three different labeling procedures. When leaf segments are fixed with formaldehyde prior to staining microfilament (MF) patterns visualized with actin antibodies and those with rhodamine‐phalloidin (Rh‐ph) are basically identical in controls. Likewise, on tissues treated with cytochalasin B (CB), actin antibodies and Rh‐ph produce very similar labeling patterns. Compared to MF alignments in fixed samples, additional sets of MFs are observed at the very cortical regions of epidermal cells that are stained with Rh‐ph without aldehyde fixation. Cortical MFs are also present in a variety of mitotic cells; MFs of meristematic cells and guard mother cells are more concentrated near the walls facing spindle poles, whereas a fine meshwork of MFs is observed along the entire periclinal surface of subsidiary mother cells. Although exactly how MFs are involved in control of the division site in higher plant cells is still to be determined, the presence of MFs during mitosis and the abnormal division observed in some stomatal cells after treatment with CB suggest that MFs are necessary for normal orientation of division in these cells, and thus normal morpho

ISSN:0886-1544    

DOI:10.1002/cm.970190105

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe have identified a 260 kD polypeptide as being the major microtubule‐associated protein (MAP) in the ovaries of the hemipteran insect,Oncopeltus fasciatus.The 260 kD insect ovarian MAP resembles certain mammalian brain MAPs by remaining soluble after boiling and promoting the assembly of tubulin into microtubules. It differs from most MAPs by exhibiting nucleotide‐sensitivity, being removed from microtubules by both ATP and GTP. Antibodies specific for the 260 kD MAP allowed its immmunofluorescent localization to the massive micro‐tubule aggregates forming the translocation systems which in hemipterans link the developing oocytes with anteriorly positioned nutritive cells. Such antibodies, in conjunction with electrophoretic methods, also demonstrated the 260 kD MAP to be species‐ and, to an extent at least, tissue‐specific. TheOncopeltus260 kD MAP was not present in the ovaries of eitherNotonectaorCorixa, hemipterans which have similar microtubule systems toOncopeltusbut MAPs of slightly different molecular weight. The 260 kD MAP from the ovaries ofOncopeltuswas not present in neuronal ganglia of the same species. The significance of the species‐ and tissue‐specificity of the 260 kD MAP, as well as its nucleotide‐sensitivity, are speculated upo

ISSN:0886-1544    

DOI:10.1002/cm.970190106

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

年代:1991

数据来源: WILEY

摘要:

AbstractThyonesperm undergo an explosive acrosome reaction resulting in the extension of a 90 μm long acrosomal process. In unreacted sperm, profilamentous actin is sequestered within the profilactin cup (Tilney:Journal of Cell Biology69:73–89, 1976), which consists of four major polypeptides: actin, profilin, and a 250/235 kDa equimolar doublet (TS 250/235). Dialysis of profilactin preparations into an actin assembly buffer resulted in the formation of acrosomal‐like macromolecular aggregates containing actin, TS 250/235, and several other polypeptides as detected by SDS‐PAGE. TS 250/235 was purified by subjecting extracts of pH solubilized profilactin cups to DEAE and phosphocellulose ion exchange chromatography. TS 250/235 demonstrated immunocrossreactivity with affinity purified polyclonal antibodies raised againstS. purpuratusegg spectrin. As determined by biotinylated‐calmodulin overlays, both subunits of TS 250/235 bound calmodulin in a Ca++‐sensitive manner. Electron microscopy of low angle, rotary shadowed replicas of TS 250/235 revealed an elongate rod‐shaped molecule with an average contour length of 203 nm. By indirect immunofluorescence, TS 250/235 was found to be uniformly distributed throughout the profilactin cup of the unreacted sperm. This distribution of TS 250/235 correlated with the location of monomeric actin as determined by localization studies utilizing fluorescent‐DNase‐1. Upon sperm activation, the cellular distribution of TS 250/235 dramatically changed and was observed both along the length and at the base of the extended a

ISSN:0886-1544    

DOI:10.1002/cm.970190107

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

年代:1991

数据来源: WILEY

ISSN:0886-1544    

DOI:10.1002/cm.970190108

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

年代:1991

数据来源: WILEY

ISSN:0886-1544    

DOI:10.1002/cm.970190101

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

年代:1991

数据来源: WILEY