ISSN:0886-1544    

DOI:10.1002/cm.970060202

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

年代:1986

数据来源: WILEY

摘要:

AbstractFlagellar motility of Triton models of sea urchin spermatozoa was reactivated by cyclic AMP‐dependent protein kinase and a protein factor, termed motility activator, both of which were prepared from the detergent‐extract of sea urchin spermatozoa. It was shown that phosphorylation of the motility activator by the protein kinase is necessary for the reactivation of flagellar motility [Ishiguro et al, J. Cell Biol. 92:777–782, 1982; Murofushi et al, in “Biological Functions of Microtubules and Related Structures,” Academic Press, 1982]. Reactivating factor was also detected in a KCI‐extract of the axoneme fraction devoid of the detergent‐extractable materials. The activity of this factor was also cyclic AMP‐ and protein kinase‐dependent. Furthermore, when freshly prepared Triton models were treated with phosphoprotein phosphatase prepared from bovine cardiac muscle, the flagellar motility was drastically suppressed. This inhibition of the motility was partially recovered by the addition of cyclic AMP and protein kinase to the phosphata

ISSN:0886-1544    

DOI:10.1002/cm.970060203

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

年代:1986

数据来源: WILEY

摘要:

AbstractAxial views of depolarization‐ and hyperpolarization‐dependent activation of the frontal cirri ofStylonychiawere cinematically recorded at high rate (250 frames/s) under voltage‐clamp. Images of a cirrus performing the cycle were processed by using computer assistance. In responding to the polarity and amplitude of the voltage signal, a cirrus inclines proximally with a particular angle and orientation. The ciliary cycle–always counterclockwise–is superimposing upon steady inclination. Correction for inclination allowed the assessment of the directional change rate and, after inclusion of the amplitude data, the determination of the ciliary angular velocity during the cycle. The method serves to isolate a new ciliary parameter: inclination, and to register precisely parameters of the cycle which may be meaningful for the understanding of the sliding

ISSN:0886-1544    

DOI:10.1002/cm.970060204

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

年代:1986

数据来源: WILEY

摘要:

AbstractEarlier hypotheses of the origin of flagella appear untenable in the light of recent evidence on the ancestry of eukaryotes. It is suggested that microtubules and flagella evolved early in eukaryote evolution to enhance phagotrophy.

ISSN:0886-1544    

DOI:10.1002/cm.970060205

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn its normal culturing environment, the trypanosomid flagellateCrithidia oncopeltipropagates basally‐directed planar waves, but may under certain conditions exhibit base‐to‐tip wave propagation in what is regarded as an avoidance response. The beat frequency and wave shape in both modes of beating are dependent on the viscosity of the swimming medium; viscosity may also influence the direction of wave propagation. IfCrithidiaexperience a sudden increase in viscosity, there is a marked increase in the proportion of the population that is seen to exhibit wave propagation from base to tip; this proportion gradually decreases with time until the whole sample has reverted to “normal” beating. In a single organism, the resumption of normal beating is not accomplished in a single transition but by a series of switches between the forward and reverse modes. The interval of time between successive switches appears to be random, while the length of time spent in base‐to‐tip wave propagation gradually decreases. Despite the randomness of the switching process, its rate when averaged over successive time intervals is found to be constant at a particular viscosity and also dependent on it. The precise manner by which this organism is able to control its direction of wave propagation is unclear. However, the switching behavior it exhibits during the period of adaptation to an increased mechanical loading of the flagellum may reflect a process that characterizes a facet of this controll

ISSN:0886-1544    

DOI:10.1002/cm.970060206

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe describe a new approach to probe the molecular biology of the living cell that uses small colloidal gold particles coupled to specific ligands. They are visualized in cells by bright‐field, video enhanced contrast microscopy. We describe the basic aspects of the technique and provide examples of applications to intracellular motility, cell membrane dynamics, receptor translocation, internalization, and intracellular routing. We also provide examples of the use of this approach in immunospecific labelling of cells and tissue section

ISSN:0886-1544    

DOI:10.1002/cm.970060207

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe incorporation of tubulin into mitotic spindles in situ was studied by incubating permeabilized mitotic cells in solutions containing [3H]GTP‐labeled or dichlorotriazinylamino fluorescein (DTAF)‐labeled tubulin. Metaphase HeLa cells or spindle‐containing “minicells” fromChaetopterusoocytes were lysed in a microtubule‐assembly buffer plus 0.5% Nonidet P‐40, 1 mg/ml 120,000g supernatant mammalian brain tubulin, and [3H]GTP. After different periods of incubation, mitotic spindles were isolated in 2 M‐glycerol‐containing assembly buffer and separated from unbound counts by centrifugation through a 4 M‐glycerol cushion;3H counts per mg protein increase linearly for 8–12 min and then reach a plateau or steady state in bothChaetopterusoocytes and HeLa cells. Addition of 4 mM CaCl2blocks or reverses incorporation. Little or no [3H]GTP is incorporated if exogenous tubulin or lysed cells are omitted from the assembly mixture.To measure the loss rate of [3H]GTP‐tubulin from mitotic spindles, cells were incubated in tubulin plus [3H]GTP for 30 min, and a 20‐fold excess of cold GTP (2 mM) was added. Samples were removed after incubation for different periods, and spindles were isolated as described above and counted for3H content. [3H]GTP is lost from spindles at a rate of about 16%/min until a new steady state is reached in about 8 min. These results are consistent with an incorporation and turnover of [3H]GTP‐tubulin in spindle microtubules of these lysed‐cell models.The location of this newly incorporated tubulin in the spindle was investigated by incorporating fluorescent DTAF‐tubulin into mitotic spindles of these lysed cell types. A short pulse (2–5 min) appears to label microtubules (MTs) near metaphase chromosomes and longer exposures label the entire spindle.The rates of incorporation and turnover that we see by [3H]GTP and fluorescent tubulin incorporation in situ are faster than those observed with brain MTs at steady state in vitro but are in the range of the rates of spindle fiber formation in prophase, and sp

ISSN:0886-1544    

DOI:10.1002/cm.970060208

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe have used immunofluorescence staining with monoclonal antibodies to tubulin and to components of the flagellar basal apparatus to examine duplication of the basal apparatus and the microtubule system assembled from it during cell division in the quadriflagellate algaPolytomella. The monoclonal antitubulin, prepared againstPolytomellaflagellar axonemes, detectsPolytomellaand mammalian tubulin by immunoblotting. By immunofluorescence and immunogold electron microscopy, it detects all microtubular structures that have been described inPolytomella. One of the antibodies generated using the isolated basal apparatus as immunogen appears to stain four of the eight basal body rootlets and is used in this study to detect early stages in the duplication of the flagellar apparatus. A cytoplasmic microtubule system is present, the elongate morphology of the cell is maintained, and the cells are motile throughout mitosis. The closed mitotic spindle forms perpendicular to the long axis of the cell. During mitosis, the newly formed basal bodies mature and four additional elongating flagella appear. Following mitosis, the eight flagella segregate into two groups, which begin to separate towards opposite poles of the cell. Concomitant with this separation, the rootlets of the parental basal apparatus separate and new rootlets are detected. We suggest that the components of the parental flagellar apparatus are segregated equally to the daughter cells. An interphase cytoskeletal microtubule array is assembled from each basal apparatus, and the morphology of the two cells is progressively established during cytokinesis.

ISSN:0886-1544    

DOI:10.1002/cm.970060209

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

年代:1986

数据来源: WILEY

摘要:

AbstractA survey study of organelle movements in a variety of cell types of plant and animal origin was made with the aid of video‐enhanced contrast, differential interference contrast (AVEC‐DIC) microscopy followed by fine analysis of the motile behavior of the individual organelles. We found that there exists besides Brownian motion a wide spectrum of active motions in cells, i.e. motion that is directionally biased through the expenditure of metabolic energy. The types of active motion seen range from a continuous motion (sometimes appearing as streaming) in plant cells and neurons to various types of less ordered and less well directed motion. We did not see any clear‐cut qualitative difference between plant and animal cells or between systems presumed to be actin‐ and microtubule‐based. A preliminary classification of the types of active motion is presented. The ongoing research activities, which aim at a more precise definition of the different types of motion by a set of quantitative parameters, are described, and the progress made so far is

ISSN:0886-1544    

DOI:10.1002/cm.970060210

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe have investigated the mechanisms that hyphae of the fungusBasidiobolus magnususe to accomplish bulk movement of their cytoplasm and saltatory organelle movements. When cells were irradiated with an ultraviolet microbeam, cytoplasmic contraction occurred. The posterior cytoplasm (toward the septum) always moved forward toward the irradiated area, whereas anterior cytoplasm (between the cell tip and target) never contracted back toward the site of irradiation. Thus, there is an intrinsic polarity in the cytoplasm. Irradiations also arrested saltatory movements. The effects of irradiation on both saltations and cytoplasmic movement appear to be mediated by Ca++. Chelating exogenous Ca++before irradiation eliminated contractions and prevented the inhibition of saltations. Furthermore, the effects of irradiation could be duplicated by using the Ca++ionophore A23187. We relate the present results to our previous report on the effects of irradiation on the cytoskeleton [McKerracher and Heath, 1986]. We conclude that two separate cytoskeletal networks exist in fungal cells, and that an actin‐containing network generates bulk cytoplasmic movemen

ISSN:0886-1544    

DOI:10.1002/cm.970060211

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

年代:1986

数据来源: WILEY