摘要:

AbstractWe report the first direct demonstration that the cytoplasmic transport of organelles and vesicles (collectively called particles) takes place along microtubules. Living keratocytes from the corneal stroma of the frog, Rana pipiens, were observed with Allen video‐enhanced constrast, differential interference constrast (AVEC‐DIC) microscopy [Allen et al, 1981]. In sufficiently thin regions of these cells a network of linear elements was visible. When particles were observed in motion, they always moved along these linear elements. The linear elements remained intact and in focus on the microscope when lysed in a cell lysis solution that stabilized microtubules. Preparations were then fixed in formaldehyde, washed with phosphate‐buffered saline (PBS), incubated with rabbit antitubulin, washed with PBS, stained with rhodamine‐conjugated goat antirabbit, and washed with PBS. The extracted cells continued to remain in place and in focus on the microscope throughout these procedures. The same cells were then observed using epifluorescence optics and a silicon‐intensified target (SIT) video camera. A network of fluorescent linear elements was seen to correspond in number, form, and position to the linear elements seen in the live AVEC‐DIC image. Taken together, the AVEC‐DIC and fluorescence microscopy observations prove that the linear elements along which particles move are microtubules (MTLEs). The observed particle speeds, pause times, and distances moved varied widely, even for the same particle on the same microtubule. Particles were also observed to switch from one microtubule to another as they were transported. The polarity of the microtubules did not seem to affect the particle direction, since particles were observed to move in both directions on the same MTLE. When not in motion these particles behaved as if anchored to the microtubules since they showed negligible Brownian motion. Finally, it was observed that an elongate particle could move onto two intersecting linear elements such that it was deformed into an inverted “Y” shape. This indicates that there may be more than a single site of attachment between the force generator

ISSN:0271-6585    

DOI:10.1002/cm.970030102

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

年代:1983

数据来源: WILEY

摘要:

AbstractSeveral proteins (eg, actin, myosin, and actin‐binding protein) in the Tritoninsoluble residue of thrombin‐stimulated platelets are important in the formation of cytoskeletal structures. Electrophoretic analyses have shown that unidentified protein bands of 68,000, 55,000, and 48–50,000 daltons are also present in larger amounts after thrombin stimulation. Since these molecular weights correspond roughly to those of the α, β, and γ chains of fibrin, and since fibrinogen is found in platelet α‐granules, these bands were compared to those obtained when purified fibrinogen was treated with thrombin, exposed to 1% Triton X‐100‐5 mM EGTA, and the resultant Triton‐insoluble residue sedimented. Identification of the 68,000‐, 55,000‐, and 48‐‐50,000‐dalton bands as fibrinogen derivatives was confirmed by identifying them in comigration studies and in autoradiographs of Triton‐insoluble residues of platelets that were electrophoretically transferred to nitrocellulose paper and treated with antifibrinogen antibody and125I‐protein A. Furthermore, if the platelet suspension was treated with thrombin in the presence of calcium ions, protein bands characteristic of the action of Factor XIII on fibrin were observed, active platelet Factor XIII apparently having been made available by lysis of platelets during preparation. Making use of the electrophoretic properties of tubulin recently described by Best et al [1981], comigration studies using hog brain tubulin indicated that tubulin is not present in significant amounts in the Triton‐insoluble residue of platelets as previously suggested. The identification of these proteins as fibrinogen derivatives does not demonstrate a physiological interaction between fibrin and the platelet cytoskeleton, since fibrin is Tritoninsoluble and can be pelleted even in the

ISSN:0271-6585    

DOI:10.1002/cm.970030103

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

年代:1983

数据来源: WILEY

摘要:

AbstractDirected movement of polymorphonuclear neutrophils (PMN) requires cell polarization and the orderly making and breaking of cell‐substrate contacts. We compared the movement of human PMN suspended from the underside of glass coverslips to that of PMN seen in “profile” on fibers, using brightfield, differential interference contrast and reflection interference microscopy. Images were recorded on film and videotape and analyzed in real time and time lapse. The distribution of F‐actin was observed with image‐enhanced fluorescence microscopy after staining with NBD‐phallacidin.PMN exhibited two patterns of motility. Fifteen to twenty‐five percent of cells moved in a low profile gliding pattern and exhibited cauded displacement of dorsal surface folds. Most PMN made progress by cycles of partial release of the lamellipodium from the substrate and anterior advance followed by arching or rolling and lamellipodial reassociation with the substrate. Cells stimulated with bacteria, casein, or chemotactic formyl peptide rarely spread on the coverglass but waved into the medium attached only by the uropod. Eventually, many detached completely from the substrate. Cells confined to the substrate surface with overlying agarose were able to locomote when confronted with these substances.F‐actin was irregularly distributed in nonpolarized suspended cells but concentrated in the lamellipodium in polarized cells. As cells arched along a substrate, F‐actin accumulated in foci corresponding to the substrate‐PMN interface, particularly at the uropod and retraction fibrils. Conversely, cells that were physically restricted to movement in the plane of the substrate surface by overlying agarose exhibited diffuse F‐actin along the entire cell. Suspended PMN polarized with formyl peptide and incubated with Con A accumulated F‐actin at the uropod. These observations suggest that both PMN locomotion and the movement of Con A binding sites involve the caudad re

ISSN:0271-6585    

DOI:10.1002/cm.970030104

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

年代:1983

数据来源: WILEY

摘要:

AbstractActivation of the motile apparatus by chemokinetic factors cannot be reliably assessed in cells that are attached to a solid substratum because motility can be totally abolished by excessive adhesion. It is however, necesary to quantify the activation of the motile apparatus in order to analyze and understand chemokinetic responses.It was the purpose of the present work to establish morphological criteria that can be used to quantify motility in nonadherent (floating) neutrophils and to predict the locomotor response under conditions of limited adhesion. The proportion of neutrophils performing crawling‐like movements (polarized cells) in suspension correlates very closely with stimulated locomotion at low to optimal concentration of f‐Met‐Leu‐Phe, ie, under conditions of limited adhesion. Reduced locomotion at supraoptimal concentrations of f‐Met‐Leu‐Phe has also morphological correlates. The major feature is the decrease in the proportion of neutrophils performing crawling‐like movements and the corresponding appearance of cells that are motile but not polarized in suspension and that do not locomote on the substratum. Concentration‐dependent changes in neutrophil length and in the proportion of polarized neutrophils with and without tail were also observed. The locomotor potential of neutrophils under conditions of limited contact with the substratum can be predicted on the basis of their motile behavior, in particular the proportion of cells showing crawling‐like movements, in suspension. In combination with measurements of adhesion the procedure should permit a more complete analysis of the regulation of che

ISSN:0271-6585    

DOI:10.1002/cm.970030105

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

年代:1983

数据来源: WILEY

摘要:

AbstractFlagellar rootlets play an important role in “primitive motile systems.” They are made of filaments able to contract by twisting and Ca+2binding. The pusules of Dinoflagellates appear to be under the control of large bundles of 2.4 nm nonactin filaments that correspond to the striated rootlets of their two flage

ISSN:0271-6585    

DOI:10.1002/cm.970030106

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

年代:1983

数据来源: WILEY

摘要:

AbstractDuring early anaphase PtK1 cells were briefly treated with the rapidly reversible microtubule (MT) poison nocodazole. This treatment abruptly stopped chromosome motion and effected a large decrease in spindle birefringence. On removal of the drug, chromosome to pole motion (anaphase A) returned, though at a lesser rate but not extent than untreated cells. In most cases elongation of the pole‐pole distance (anaphase B) also occured, at both a rate and to an extent less than in untreated cells. During the recovery period following drug arrest spindle birefringence did not return to pretreatment levels. Electron microscopic analysis of nocodazole arrested, or arrested and released, cells revealed extensive disassembly of the nonkinetochore class of MTs (nkMTs), particularly evident in the astral region. Microtubules seen in the interzone region were largely fragments of midbody precursors. Kinetochore MTs (kMTs) appeared to be unaffected by the brief drug treatment chosen for these experiments. Analysis of MT profiles seen in transverse sections of the interzone region indicated in treated and released cells approximately 60% fewer MTs. This may suggest that chromosome motion during anaphase is not dependent on interactions between kMTs and nkMTs and separation of the spindle poles can occur in the presence of disrupted interzonal MT

ISSN:0271-6585    

DOI:10.1002/cm.970030107

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

年代:1983

数据来源: WILEY

摘要:

AbstractAlthough bacterial flagellar sheaths were observed over 30 years ago, they may still be characterized as structures in search of a function. In addition to true sheaths, bacterial flagella may possess other adornments that cause an increase in the organelle's cross‐sectional diameter. These “complex flagella” are sharply differentiated from sheathed flagella. Immunological and chemical distinctions have been found between flagellar sheaths, flagellar cores, and LPS layers inferred to be the sheath sensu stricto. Although complex flagella may serve as specific receptors for flagellotropic phages or in allowing for more efficient swimming in viscous environments, similar functions have not yet been attributed to true sheaths. It is postulated that flagellar sheaths may allow for specific interaction between a bacterium and a surface. In addition, there is a problem as to the relationship between a rapidly rotating flagellum and the s

ISSN:0271-6585    

DOI:10.1002/cm.970030108

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.970030109

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.970030110

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.970030101

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

年代:1983

数据来源: WILEY