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  • Wiley-Blackwell  (56,788)
  • 1985-1989  (52,677)
  • 1945-1949  (4,111)
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  • 1
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    Wiley-Blackwell
    In:  Journal of Zoology, 214 (2). pp. 189-197.
    Publication Date: 2020-07-17
    Description: The cuttlefish ingests much skeleton from the crustaceans and fish it preys upon. The skeletal pieces are relatively large and their dimensions bear a close relationship to the length of the buccal mass and diameter of the oesophagus. The structures of the buccal mass are instrumental in the breakdown of prey and orientation of long pieces of skeleton to ensure their entry into the oesophagus. Many pieces of skeletal material present in the stomach contents still have attached muscles, showing that there is little, or no, external digestion. Skeletal material may be important for long-term maintenance of young Sepia in captivity.
    Type: Article , PeerReviewed
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  • 2
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    Wiley-Blackwell
    In:  Journal of Zoology, 218 (4). pp. 603-608.
    Publication Date: 2020-07-17
    Type: Article , PeerReviewed
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  • 3
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    Wiley-Blackwell
    In:  Journal of Zoology, 212 (2). pp. 303-324.
    Publication Date: 2020-07-17
    Description: The diet of the king penguin Aptenodytes patagonicus at Marion Island was examined throughout the year by analysis of stomach samples. Fish accounted for 87% by wet mass, 75% by numbers and 69% by reconstituted mass. Their proportional importance by wet mass increased from 68% during winter to almost 100% in summer and probably reflects a real increase in their local availability. Squid comprised most of the remainder with crustaceans forming less than 1% of the diet by numbers. Prey items were generally small, the most abundant being three species of myctophid fish, Krefftichthys anderssoni, Protomyctophum tenisonì and Electrona carlsbergi, and a squid Kondakovia longimana. King penguins took both juvenile and adult Krefftichthys anderssoni and P. tenisoni, but only adult E. carlshergi. The juvenile and adult modal size classes of K. anderssoni and P. tenisoni increased from March through to February and the proportion of juvenile to adult fish increased in winter. The increase in the modal size class of the K. anderssoni/P. tenisoni complex during the year probably reflects growth of the fish, rather than movement of different populations in and out of the area exploited by king penguins. All squid consumed were probably juveniles. The modal size class of Kondakovia longimana increased from March to August, but in September to October smaller squid again formed a large proportion of the squid component of the diet. Numbers of measurable squid beaks recovered from November to February were low. This is the first time that mesopelagic myctophid fish have been shown to comprise a major component of the diet of a vertebrate predator in the Southern Ocean.
    Type: Article , PeerReviewed
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  • 4
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    Wiley-Blackwell
    In:  Lethaia, 21 (4). pp. 375-382.
    Publication Date: 2020-07-15
    Description: In the animal kingdom evolutionary size changes involved increasing, decreasing and stationary patterns. Planktic and benthic Foraminifera chiefly increased their size during evolution. This increase, however, did not always occur gradually, but could be interrupted by periods when the animals maintained or even decreased in size. The rate of the size increase is different for the various species examined, some benthic forms grew only 10% during the Oligocene-Pleistocene interval, while for others this figure was up to 96%. Some benthic species increased in size in certain areas, but not in others. It is not improbable that some phylogenetic trends of planktic Foraminifera representing, according to stratigraphers, the evolution of one species into another, represent in reality, from the biological point of view, specimens of the same species which changed their size and in addition some minor morphological traits which are encompassed by the normal span of intraspecific variability. A comprehensive understanding and explanation of the size change of Foraminifera needs much additional research.
    Type: Article , PeerReviewed
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  • 5
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    Wiley-Blackwell
    In:  Nordic Journal of Botany, 7 (3). pp. 359-363.
    Publication Date: 2018-10-02
    Description: Blidingia minima var. ramifera is reported for the first time in eastern North America. It occurs in the Gulf of St. Lawrence, Nova Scotia and in Maine. In the estuary of the West and Rights Rivers (Antigonish Harbour, Nova Scotia) it is the most common intertidal alga and during its maximum growth period (June‐August) covers 75–90% of the intertidal zone for several km of shoreline at the mouth of the Rights River. In culture, spore germination and early development were typical of the taxon as described from Europe. The taxon is raised to specific status as Blidingia ramifera stat. nov. Blidingia subsalsa is confirmed from New England based on observations of spore germination in plants from Maine and Connecticut.
    Type: Article , PeerReviewed
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  • 6
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    Wiley-Blackwell
    In:  Marine Ecology, 8 . pp. 1-20.
    Publication Date: 2017-10-05
    Description: Benthic metabolism and standing stocks were investigated in the deep Red Sea between 21o and 27oN, Activity was assessed by the determination of respiration rates with a shipboard method and by calculating oxygen consumption from the activity in the electron transport system. We attempted to compare results from different latitudes within the warm Red Sea and with data from cold Atlantic environments. Our investigations were part of an environmental risk assessment to evaluate future mining of metalliferous sediments from the Atlantis II Deep.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 5 (1985), S. 251-263 
    ISSN: 0886-1544
    Keywords: Chlamydomonas ; movement ; flagellar beat ; stigma ; high-speed microcinematography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using high-speed microcinematography (100-500 f/s) the movement of Chlamydomonas reinhardtii mutant 622 E has been studied with frame-by-frame analysis. The stigma lies in the cell equator, displaced out of the flagellar plane anticlockwise by an angle of about 45°. During forward movement the cells rotate anticlockwise about their long axis with a frequency of 1.4-2 Hz (maximum 2.5 Hz). The rotation is caused by a lateral component of 3-dimensional beating of the flagella during the effective strokes. The helical swimming path is a result of an unequal flagellar beating. This is normally synchronous, but synchrony is interrupted from time to time by an additional beat of the outward directed flagellum, in our study one after about every twenty beats on average. These results are discussed and compared with the results published by other groups.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 5 (1985) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 5 (1985), S. 377-392 
    ISSN: 0886-1544
    Keywords: newt ; lung ; cilia ; beat frequency ; waveform ; models ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Highly coupled newt lung ciliated cell models were used to study the effects of MgATP concentration on ciliary beat frequency and waveform. Models were prepared from ciliated lung cells of the newt Taricha granulosa by trypsin dissociation of the epithelium, demembranation with Triton X-100, and reactivation with MgATP, as described previously [Weaver and Hard, 1985]. Beat frequencies were measured stroboscopically. Ciliary waveforms of reactivated models and intact mucociliary epithelial sheets were determined by single frame analysis of high-speed movies. Waveform parameters calculated included the durations of the effective and recovery strokes, the angular velocities of the ciliary base and tip, the position of the bend along the ciliary shaft during the recovery stroke, the velocity of recovery stroke bend propagation, and the ratio of the duration of recovery stroke bend propagation to the duration of the recovery stroke itself. We found that beat frequency varied biphasically in response to MgATP at 21°C, as shown previously for isolated, individual, newt lung axonemes. Apparent Fmax (maximum beat frequency) and Km values of 25 Hz and 0.14 mM, and 35 Hz and 0.47 mM, respectively, were obtained for each linear segment of the biphasic double reciprocal plot. Demembranation did not alter either ciliary waveform or the pattern of coordination. In this system, metachrony is antilaeoplectic and ciliary waveform appears to be regulated independent of beat frequency.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 5 (1985), S. 507-527 
    ISSN: 0886-1544
    Keywords: axonal transport ; microtubules ; organelles ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A model for fast axonal transport is developed in which the essential features are that organelles may interact with mechanochemical cross-bridges that in turn interact with microtubules, forming an organelle-engine-microtubule complex which is transported along the microtubules. Computer analysis of the equations derived to describe such a system show that most of the experimental observations on fast axonal transport can be simulated by the model, indicating that the model is useful for the interpretation and design of experiments aimed at clarifying the mechanism of fast axonal transport.
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 1-1 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 25-34 
    ISSN: 0886-1544
    Keywords: respiratory cilia ; dynein ; ATPases ; porcine trachea ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Milligram amounts of mammalian ciliary axonemes were isolated from porcine tracheas. These were reactivated upon addition of ATP, indicating intact functional capability with a mean beat frequency at 37°C of 8.2 Hz. Electron microscopy showed typical ultrastructure of the isolated demembranated axonemes. Electrophoresis into polyacrylamide gradient gels containing sodium dodecyl sulfate revealed reproducible protein profiles from ten different tracheal preparations. Four major protein bands were observed in the 300-330 K molecular weight region, as well as tubulin at 51-54K. Extraction of the isolated tracheal axonemes with 0.6M KCl removed the outer dynein arms seen in electron microscopic cross-section of axonemes, preferentially solubilized two of the high molecular weight proteins at 320 and 330 K, and resulted in a three- to four-fold increase in ATPase specific activity. Sedimentation of the dialyzed salt extract on a 5-30% sucrose density gradient and subsequent fractionation yielded two peaks of ATPase activity. The faster migrating, 19S major ATPase peak correlated with the 320 and 330 K proteins, and two other proteins at 81 and 67 K. The slower sedimenting, 12S minor ATPase peak corresponded to a 308 K protein and two smaller proteins at 33 and 48 K. Thus, the outer dynein arm of tracheal cilia appeared to be associated with at least two high molecular weight proteins. These results demonstrate that adequate quantities of functionally intact axonemes can be reproducibly isolated from porcine tracheas, allowing further fractionation and analysis of mammalian cilia.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 14
    ISSN: 0886-1544
    Keywords: contractile system ; microfilaments ; microtubules ; endoplasmic reticulum ; ciliophora ; oligotrichina ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Tontonia appendiculariformis is a marine planktonic ciliate with a long tail. The tail can contract rapidly, becoming transformed into an oval mass one-twentieth of its original length. The highly complex ulrastructure of the tail is described here in detail. A large part of the volume of the tail contains numerous more or less parallel membranous tubes. The membrane of the tubes has numerous invaginations and is probably derived from the smooth endoplasmic reticulum. This tubular material forms a continuous layer around the tail, interrupted in only one region, which contains cilia. Associated with the cilia are basal fibres with a periodically banded appearance. The tubular layer forms several folds separated by hyaloplasm containing many mitochondria. The pellicle of the tail is thrown into numerous pleats. It comprises a perilemma, a plasmalemma, and complex alveoli, but epiplasm and microtubules are absent. The alveoli appear to form septa within the folds of the layer of membranous tubes. In the region where the tail is attached to the body of the ciliate there are conspicuous bundles of microtubules and microfilaments. The membranous tubes and septa appear to be connected to small bundles of microfilaments, which presumably represent the contractile material. However, we consider the membranous tubes as potentially active in producing the change in shape. Although the structure of the tail of Tontonia is unique, there are certain similarities to the stalk of the Tintinnina and also to the motile extension of the dinoflagellate Erythropsidinium.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 249-255 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 229-236 
    ISSN: 0886-1544
    Keywords: α-helix ; filament motility ; filament contractility ; filament sliding ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The twisting behavior of α helices has hardly been considered hitherto with regard to the function of proteins. The well-known electrostatic repulsion between the highly charged side chains, which depends on their interaction with ions, is absolutely connected with torsional rotations of the helix as long as its hydrogen bonds hold. This means a direct transformation of chemical into mechanical energy. However, the stability of a twisted single α helix with charged side chains is low in an aqueous environment. It may easily ball up to form a globular molecule with nonhelical regions of the polypeptide chain. This corresponds to a primitive contraction that obviously occurs with spasminlike proteins that contain strongly twisted filaments as Salisbury [J. Submicrosc. Cytol. 15:105-110, 1983] has shown. Steps that increase the stability and rigidity of α helical filaments are (1) the formation of coiled-coils, (2) self-intertwining (“telephone cord phenomenon”) or intertwining with other coiled-coils as shown with the intermediate filaments, and (3) association with cytoskeletal elements (microfilaments, protofilaments of microtubules) that contain globular subunits. These coarser elements are rotated by winding and unwinding of the smaller helical molecules and thus transmit the torsion produced in the α helices to the microscopic level by the sliding (screwing) motion and the shearing effect that is connected with the waves of a rotating helix. Particles are transported if connected to the helical side arms. Since the displacement of the side arms seems to occur along the single protofilaments of a microtubule, a rotation of these protofiiaments is suggested. The bidirectional transport of particles along single microtubules may be explained by the association of left- and right-handed helices with the protofilaments. According to the models, parallel and antiparallel sliding of neurofilaments and neurotubules is suggested.
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 256-272 
    ISSN: 0886-1544
    Keywords: ciliary motility ; cAMP regulation ; swimming speed ; membrane potential ; detergent models ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The membrane potential of Paramecium controls the frequency and direction of the ciliary beat, thus determining the cell's swimming behavior. Stimuli that hyperpolarize the membrane potential increase the ciliary beat frequency and therefore increase forward swimming speed. We have observed that (1) drugs that elevate intracellular cyclic AMP increased swimming speed 2-3-fold, (2) hyperpolarizing the membrane potential by manipulation of extracellular cations (e.g., K+) induced both a transient increase in, and a higher sustained level of cyclic AMP compared to the control, and (3) the swimming speed of detergent-permeabilized cells in MgATP was stimulated 2-fold by the addition of cyclic AMP. Our results suggest that the membrane potential can regulate intracellular cAMP in Paramecium and that control of swimming speed by membrane potential may in part be mediated by cAMP.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 5 (1985), S. 529-543 
    ISSN: 0886-1544
    Keywords: actin ; regulatory protein ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have isolated a 30,000-dalton protein from Dictyostelium which cosedimented with and affected the low shear viscosity of actin. At low concentrations, this protein increased the low shear viscosity to greater than that of the actin control, whereas higher concentrations decreased viscosity. The viscosity decrease correlated with the formation of actin filament bundles, as seen electron microscopically. This protein resembled a previously reported actin-binding protein from Dictyostelium [Fechheimer and Taylor, 84, J Biol Chem 259:4514] in electrophoretic mobility, Stokes radius, and ability to crosslink filaments, but was shown to be different by peptide mapping, lack of immunologic crossreactivity, and lack of sensitivity to calcium.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 5 (1985), S. 545-557 
    ISSN: 0886-1544
    Keywords: neutrophils ; cytoskeleton ; actin polymerization ; NBDphallacidin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The studies presented here characterize a simple, quantitative NBDphallacidin extraction assay for determining the F-actin content of fMLP-activated neutrophils. The NBDphallacidin extraction assay is based upon the specificity of NBDphallacidin binding to F-actin and the solubility of NBDphallacidin in methanol. Cells are fixed, permeabilized, and stained with NBDphallacidin; the cells are then pelleted, the bound NBDphallacidin is extracted into methanol, and the RFI (excite 465; emit 535) of the solution is determined. Binding of NBDphallacidin to neutrophils is saturable and 90% of bound NBDphallacidin is displaced by nonfluorescent phalloidin. The extraction of bound NBDphallacidin into methanol is complete and the excitation/emission characteristics of NBDphallacidin are not altered by extraction. The assay is relatively inexpensive, applicable to the study of cells in suspension or on substratum, allows kinetic studies with 5-10s time resolution, and is not affected by the shape of the cell or the distribution of the probe. We used the NBDphallacidin extraction assay to study the kinetics of fMLP-induced change in the F-actin content of neutrophils and the effect of tBOC peptide, an inhibitor of fMLP binding, on these changes. The extraction assay reveals a rapid, sequential fMLP-induced increase followed by a decrease in F-actin content. The tBOC peptide inhibits fMLP-induced actin polymerization. Addition of tBOC during fMLP-induced polymerization or at times when F-actin content is maximal enhances F-actin depolymerization. The rate of F-actin depolymerization is ≥ fourfold faster in the presence than in the absence of tBOC. The results show that (1) The NBDphallacidin extraction assay is useful for studying the kinetics of change in F-actin content of nonmuscle cells; (2) fMLP receptor occupancy is required for fMLP-dependent polymerization but not depolymerization; and (3) both the actin polymerizing and depolymerizing processes are active in the cell within 5 s after fMLP stimulation. Implications of these observations for understanding the observed increase and, then, decrease in F-actin content of fMLP-activated cells are discussed.
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 48-55 
    ISSN: 0886-1544
    Keywords: vinculin ; actin ; adhesion plaques ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Vinculin was purified from chicken gizzard by a modification of the method of Feramisco and Burridge [1980; J Biol Chem 255:1194]. Vinculin did not alter the viscosity of actin as measured in an Ostwald viscometer, nor did it affect actin polymerization as measured with the fluorescent NBD-actin assay. Sedimentation experiments demonstrated that vinculin did not bind to actin, and electron microscopy of negatively stained specimens indicated that vinculin did not aggregate actin filaments into bundles. These results suggest that vinculin, by itself, does not interact with actin at least under commonly used conditions to assay actin-protein interactions in vitro.
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  • 21
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 35-47 
    ISSN: 0886-1544
    Keywords: microbeam ; microtubules ; nucleus ; cytoskeleton ; motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: During hyphal tip growth in the fungus Basidiobolus magnus, nuclei normally maintain a constant distance from the advancing cell apex by continuously migrating forward. It is not known whether the mechanism that produces nuclear movement also mediates nuclear positioning, or whether these two processes are under separate control. By irradiating small cytoplasmic regions with an ultraviolet microbeam, the coordination between movement and positioning could be disrupted. Regardless of the distance of the target from the nucleus, anterior irradiations (those ahead of the nucleus) caused the nucleus to stop or move backwards, whereas posterior (behind the nucleus) irradiations caused an acceleration in the nuclear velocity. The nucleus retained its ability to move following irradiation, so there was only loss of control over normal positioning. These results suggest that movement and positioning are mediated by different mechanisms. Quantitative microtubule analysis demonstrated that microtubules in the target region had been depolymerized, but in other regions of the cell they were apparently normal. We suggest that the depolymerization of microtubules affects nuclear movement by altering the tensile strength of the cytoplasm, and that cytoskeletal tension mediate nuclear positioning.We also found that accelerated nuclear movement could occur when most of the microtubules surrounding the nucleus were depolymerized. A comparison of the microtubule population surrounding the nucleus in unirradiated versus irradiated cells suggested that microtubules move with nuclei. Therefore, the nucleus does not appear to move via a direct interaction with microtubules.
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  • 22
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 7 (1987) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 23
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 640-648 
    ISSN: 0886-1544
    Keywords: cell model ; lamellipodia ; phosphorylation ; Ca2+-dependent contraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Permeabilized cell models of muscle and nonmuscle cells have proven useful for examining the regulation of actin, myosin, and other cytoskeletal proteins during cell contraction. Upon addition of Ca2+ and ATP, glycerinated chick embryonic skin fibroblasts retract their tails and lamellipodia. Ca2+-independent contractions are obtained by preincubation of cell models in Ca2+ ATPγS, followed by EGTA and ATP addition, or by addition of trypsin-treated myosin light chain kinase that no longer requires Ca2+ for reactivation. By pretreating cells before glycerination with colchicine, it is possible to study lamellipodial contraction independent of tail contraction. Similar responses to ATPγS pretreatment and unregulated myosin light chain kinase are observed in cells that only contain lamellipodia. SDS-PAGE electrophoresis of glycerinated fibroblasts incubated in ATPγ35S and Ca2+ shows that only two major proteins are thiophosphorylated, and that one of them, a band that comigrates with the 20K MW light chain of myosin, is thiophosphorylated in a Ca2+-dependent manner. Since the rate of tail contraction is several-fold faster after Ca2+ and ATPγS pretreatment or incubation in excess myosin light chain kinase, myosin light chain phosphorylation may be a rate-limiting step during contraction.
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  • 24
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We present a high-resolution electron microscopic study of the sidearms on microtubules and vesicles that are suggested to form the crossbridges which produce the microtubule-based vesicle transport in squid axoplasm. The sidearms were found attached to the surfaces of the anterogradely transported vesicles in the presence of ATP. These sidearms were made of one to three filaments of uniform diameter. Each filament measured 5-6 nm in width and 30-35 nm in length. The filaments in some of the sidearms had splayed apart by pivoting at their base, thereby assuming a “V” shape. The spread configuration illustrated the independence of the individual filaments. The filaments in other sidearms were closely spaced and oriented parallel to each other, a pattern called the compact configuration. In axoplasmic buffer containing AMP-PNP, structures indistinguishable from the filaments of the sidearms on the vesicles were observed attached to microtubules. Pairs of filaments, thought to represent the basic functional unit, were observed attached to adjacent protofilaments of the microtubules by their distal tips. These data support a model of vesicle movement in which a pair of filaments within a sidearm forms two crossbridges and moves a vesicle by “walking” along the protofilaments of the microtubule.
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  • 25
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 7 (1987), S. 31-38 
    ISSN: 0886-1544
    Keywords: microtubule assembly ; proleolysis ; Vinca drugs ; Zn2+-induced assembly ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Limited proteolysis of tubulin with subtilisin results in cleavage of both the α and β subunits, releasing small peptides from the C-terminal ends. At 37°C the digested tubulin assembles into polymorphic structures: microtubules with attached ribbons in the presence of GTP, rings in the presence of GDP, and protofilament spirals in the presence of vinblastine. Undigested tubulin does not assemble under these conditions. Rings and Vinca-induced spiral structures are assembled from undigested tubulin only when microtubule-associated proteins, high Mg2+ concentrations, or polycations are present. Thus, cleavage with subtilisin affects assembly in a manner similar to the addition of these agents. It appears that binding of positively charged substances may act by neutralizing the charge on the highly acidic C-terminal regions of the α- and β-subunits, while cleavage with subtilisin produces the same effect by removing these peptides. Undigested and subtilisin-digested tubulin form sheets of protofilaments in the presence of Zn2+, which indicates that the binding sites for the 2-3 Zn2+ ions necessary to induce sheet formation do not reside in the C-terminal regions of the monomers.
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  • 26
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 7 (1987), S. 46-53 
    ISSN: 0886-1544
    Keywords: actin filament ; fertilization ; fluorescent labeled phallotoxins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution of actin filaments in the cortical layer of sea urchin eggs during fertilization has been investigated by light microscopy using fluorescently labeled phallotoxins. The cortical layer of both whole eggs and cortices isolated on a glass surface was examined. In cortices of unfertilized eggs, numerous fluorescent spots were seen, which may correspond to short actin filament cores in microvilli. After insemination, one of the sperm-attaching points on the egg surface first became strongly fluorescent. This fluorescence grew around the point of sperm penetration with the growth of the fertilization cone. Then, the cortical layer of the egg around the fertilization cone became strongly fluorescent and the fluorescence propagated in a wavelike manner over the entire cortex. The mechanism of the propagation of actin polymerization is discussed.
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    Cell Motility and the Cytoskeleton 7 (1987), S. 87-93 
    ISSN: 0886-1544
    Keywords: movement ; flagellar ; beat, flagellar ; stigma ; high-speed microcinematography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chlamydomonas cells sucked onto micropipettes were filmed at 500 frames/sec and analyzed as to their forward beating mode. A comparison with freely swimming cells revealed that the flagella of the sucked cells beat in a normal threedimensional manner, with beat frequencies that correspond to those of freely swimming cells. Most beats were synchronous. but not symmetrical; cis- and trans-flagellum appear to beat in a slightly different manner. Some cells beat synchronously throughout, but mostly synchrony was interrupted by a single asynchrony or up to incessant asynchronies, caused by transient accelerations of the trans- (fo-) flagellum. Only rarely did cis- and trans-flagella have different but constant beat frequencies. Helical swimming of Chlamydomonas more likely is due to the beat asymmetries of the two flagella than to differences of beat frequencies. In our records, the stigma is on the inside of the helical swimming path.
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  • 28
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    Cell Motility and the Cytoskeleton 7 (1987), S. 110-115 
    ISSN: 0886-1544
    Keywords: microtubules ; antitubulin ; particle translocalion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubules have been demonstrated to be a substrate for organelle transport and particle translocation in vitro and in vivo. Subsequent to a previous report of inhibition of axonal transport of exogenous tracers in vivo using antiserum NS-20 against tubulin (Johnston et al: Brain Res. 1986), we now show disruption of particle movement in extruded squid axoplnsm using this unique immunological probe. Using video-enhanced contract-differential interference contrast (AVEC-DIC) microscopy, we examined the properties of particle movement along microtubules and demonstrated that bolh the velocity of particle movement and the numbers of particles moving are decreased in the presence of NS-20 antiserum or NS-20 affinity-purified antibodies but. not in the presence of another antiserum against tubulin. The amount of microtubule substrate does not change in the presence of any of the antisera. In conclusion, we suggest that NS-20 antibodies bind near or at a site on the tubulin molecule which is critical in the mechanism of particle transport, and provide a direct immunological probe to examine the mechanism of microtubule involvement in axonal transport.
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  • 29
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    Cell Motility and the Cytoskeleton 7 (1987), S. 116-128 
    ISSN: 0886-1544
    Keywords: actin filament bundle ; macrociliary cell ; Clenophores ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Macrocilia are thick compound ciliary organlles arising individually from elongated epithelial cells on the lips of beroid ctenophores. A giant wedge-shaped bundle of microfilaments extends 25-30 μm from the base of each macrocilium to the lower end of the cell, terminating at a junction with an underlying smooth muscle cell. The broad end of the microfilament bundle is anchored to the macrocilium by striated rootlet fibers that extend from the basal bodies into the bundle and are linked to the microfilaments by periodic bridges. Fluorescence microscopy of rhodamine-phalloidin stained intact tissue, dissociated macrociliary cells, and Triton/glycerol-isolated bundles shows that the microfilaments contain actin. The microfilaments run generally parallel to the long axis of the bundle but are not highly ordered. Filaments decorated with myosin S1 show a uniform polarity with arrowheads pointing away from the tapered membrane-associated end of the bundle. No variations in bundle length (nor changes in rootlet periodicity) were observed in tissue fixed under conditions of calcium activation. Isolated bundles did not contract in Mg-ATP, even though detached macrocilia underwent reactivated beating and sliding disintegration. Macrocilia arc used to bite through food organisms or transport prey into the stomach. The actin filament bundles probably play a supporting role as a structural linker between macrocilia and subepithelial muscle fibers and may serve as intracellular tendons lo mechanically coordinate the motor activities of macrocilia and muscles during prey ingestion.
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    Cell Motility and the Cytoskeleton 7 (1987), S. 129-137 
    ISSN: 0886-1544
    Keywords: actin mRNA ; sclerotium ; polysomes ; Triton X-100 extraction ; cycloheximide ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Translationally active plasmodia of the syncytial slime mold Physarum polycephalum develop into translationally dormant sclerotia during starvation. Although functional mRNA and ribosomes exist in sclerotia, protein synthesis is suppressed at the level of initiation. To test the possibility that alterations in the cytoskeleton may limit protein synthesis, we have examined the distribution of polysomes and actin mRNA in the cytoskeletal (CSK) and soluble (SOL) fractions of Triton X-100-extracted plasmodia and sclerotia. Most of the polysomes and actin mRNA were located in the CSK of plasmodia, while most of the ribosomes and actin mRNA were located in the SOL of sclerotia. The results suggest that ribosomes and mRNA shift from the CSK to the SOL as protein synthesis is suppressed during starvation. Plasmodia and sclerotia can be induced to accumulate excess polysomes by treatment with low levels of the elongation inhibitor cycloheximide. Treatment of plasmodia with cycloheximide caused excess polysomes to accumulate in the SOL, suggesting that the CSK contains a limited capacity for binding translational components and that the association of polysomes with the cytoskeleton is not required for protein synthesis. Treatment of sclerotia with cycloheximide, however, caused polysomes and actin mRNA to accumulate in the CSK, suggesting that the selcrotial cytoskeleton, although depleted in ribosomes and mRNA, is capable of binding translational components. It is concluded that alterations in the sclerotial cytoskeleton are not involved in translational control.
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    ISSN: 0886-1544
    Keywords: calcium ; protein phosphorylation ; TFP ; Triton-extracted model ; ciliary orientation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To explore possible roles of calmodulin in Ca2+-induced ciliary reversal, we tested the effects of calmodulin antagonists on Triton-extracted models of Paramecium. In the extracted models prepared by the method of Naitoh and Kaneko [Science 176:523-524, 1972], the Ca2+ -induced ciliary reversal was not inhibited by calmodulin antagonists, trifluoperazine (TFP), or 5-chloro-l-naphthalenesulphone amide (W-7). However, in the presence of adenosine 3′,5′-cyclic mono-phosphate (cAMP), whose concentration is below the one that alters the ciliary direction, TFP inhibited ciliary reversal and the models swam forward at 10-5 M Ca2+. When the washing medium in the preparation of the extracted models was replaced with one containing MgCl2, the extracted model showed sensitivity to calmodulin antagonists without addition of cAMP; at 10-5 M Ca2+, 40 μM TFP or 100 μM W-7 inhibited the ciliary reversal and the models swam forward. Such effect of antagonists was abolished by an inhibitor of cAMP-dependent protein kinase. On the other hand, addition of cAMP enhanced the inhibitory effect of antagonists. These results suggest that calmodulin antagonists act to increase the extent of cAMP-dependent protein phosphorylation that inhibits the Ca2+ -induced ciliary reversal.
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    Cell Motility and the Cytoskeleton 7 (1987) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 7 (1987), S. 178-186 
    ISSN: 0886-1544
    Keywords: colchicine binding ; tubulin ; immunofluorescence ; PtK2 ; Pk15 ; SV-3T3 cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: 2-methoxy-5-(2,3,4-trimethoxyphenyl) 2,4,6-cycloheptatrien-1-one (MTC) is a synthetic colchicine analogue, lacking the B ring of the alkaloid (Fitzgerald: Biochem. Pharmacol. 25:1381-1387, 1976). MTC has been shown to bind reversibly to the colchicine binding site of tubulin and to inhibit microtubule assembly in vitro (Andreu et al: Biochemistry 23:1742-1752, 1984; Bane et al: J. Biol. Chem. 259:7391-7398, 1984). Its action on different cultured cell lines (PtK2, Pk15, and SV-3T3) has now been studied. 0.2 × 10-6 M MTC stopped Pkl5 and SV-3T3 cell growth, inducing an accumulation of mitoses in a few hours. Removal of MTC from the culture medium rapidly restored normal mitotic index and growth rates. Partial depolymerization of the cytoplasmic microtubules of PtK2 cells was observed at concentrations ranging from 2 to 5 × 10-7 M. Maximal microtubule network depolymerization was obtained after 4 h of treatment with 2 to 5 × 10-6 M MTC or at a higher MTC concentration (2 × 10-5 M) for less than 2 h. Removal of 2 × 10-5 M MTC (the highest MTC concentration used) from the culture medium resulted in almost complete microtubule polymerization after 10 min of drug recovery and a normal microtubule network in 20-30 min.MTC constitutes an antimitotic drug directed to the colchicine site. It is water-soluble, shows a fast and reversible action, and may therefore be employed as a convenient tool to study cellular microtubule-dependent functions.
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    Cell Motility and the Cytoskeleton 8 (1987), S. 238-249 
    ISSN: 0886-1544
    Keywords: human lymphoblastoma cells ; microtubule organizing centers ; isolation centrioles ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A procedure adapted from that described by Mitchison and Kirschner [Nature 312:232-237, 1984] was used to isolate centrosomes from human lymphoid cells. High yields of homogeneous centrosomes (60% of the theoretical total, assuming one centrosome per cell) were obtained. Centrosomes were isolated as pairs of centrioles, plus their associated pericentriolar material. Ultrastructural investigation revealed: 1) a link between both centrioles in a centrosome formed by the gathering in of a unique bundle of thin filaments surrounding each centriole; 2) a stereotypic organization of the pericentriolar material, including a rim of constant width at the proximal end of each centriole and a disc of nine satellite arms organized according to a ninefold symmetry at the distal end and; 3) an axial hub in the lumen of each centriole at the distal end surrounded by some ill-defined material.The total protein content was 2 to 3 × 10-2 pg per isolated centrosome, a figure that suggests that the preparations were close to homogeneity. The protein composition was complex but specific, showing proteins ranging from 180 to 300 kD, one prominent band at 130 kD, and a group of proteins between 50 and 65 kD. Actin was also present in centrosome preparations.Functional studies demonstrated that the isolated centrosomes were competent to nucleate microtubules in vitro from purified tubulin in conditions in which spontaneous assembly could not occur. They were also very effective at inducing cleavage when microinjected into unfertilized Xenopus eggs.
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    Cell Motility and the Cytoskeleton 8 (1987), S. 274-283 
    ISSN: 0886-1544
    Keywords: focal contacts ; vimentin filaments ; microtubules ; immunofluorescence ; platinum replicas ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Double immunofluorescence staining of quail embryo fibroblasts with rabbit antibody to vinculin and mouse monoclonal antibody to vimentin revealed a coincidence between fluorescence patterns for cell-substrate focal contacts and intermediate filaments. Most of the vinculin-containing adhesion plaques coincided with the ends of vimentin-positive fibrils.This association was further corroborated by immunoelection microscopic observations of the cytoskeletons of quail and mouse fibroblasts using a platinum replica technique. The intermediate filaments were identified either by direct treatment with antivimentin IgM or by an indirect immunogold staining method.Colcemid treatment of the cells caused a collapse of intermediate filaments and destroyed their association with focal contacts. During the early stages of the colcemid-induced collapse of the intermediate filaments, single vimentin fibrils appeared to retain their association with focal contacts.The possible role of the intermediate filaments in the formation and maintenance of focal contacts is discussed.
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    Cell Motility and the Cytoskeleton 8 (1987), S. 284-291 
    ISSN: 0886-1544
    Keywords: tyrosination ; acetylation ; post-translational modifications ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have examined the distribution of acetylated α-tubulin using immunofluorescence microscopy in fibroblastic cells of rat brain meaninges. Meningeal fibroblasts showed heterogenous staining patterns with a monoclonal antibody against acetylated α-tubulin ranging from staining of primary cilia or microtubule-organising centers (MTOCs) alone to extensive microtubule networks. Staining with a broad spectrum anti-α-tubulin monoclonal indicated that all cells possessed cytoplasmic microtubule networks. From double-labeling experiments using an antibody against acetylated α-tubulin (6-11B-1) and antibodies against either tyrosinated or detyrosinated α-tubulin, it was found that acetylated α-tubulin and tyrosinated α-tubulin were often segregated to different microtubules. The microtubules containing acetylated but not tyrosinated α-tubulin were cold stable. Therefore, it appeared that in general meningeal cells possessed two subset of microtubules: One subset contained detyrosinated and acetylated α-tubulin and was cold stable, and the other contained tyrosinated α-tubulin and was cold labile. These results are consistent with the idea that acetylation and detyrosination of α-tubulin are involved in the specification of stable microtubules.
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    Cell Motility and the Cytoskeleton 8 (1987), S. 302-311 
    ISSN: 0886-1544
    Keywords: flagella ; cAMP ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When demembranted axonemes of Chlamydomonas were reactivated with Mg ATP, the proportion of motile axonemes was significantly increased by the preence of either phosphodiesterase (PDE) or protein inhibitor of cAMP-dependent kinase (PKI). The effect of PDE was cancelled by the addition of cAMP. These findings strongly suggest that the axoneme samples have endogenous cAMP, which can reduce the proportion of motile axonemes via phosphorylation. This inhibitory effect of cAMP on Chlamydomonas axonemes is opposite to its stimulatory effect on the axonemal motility in other organisms so far reported. PKI or PDE activated the motility motility either in the absence of Ca2+, when the axonemes beat with an asymmetric waveform, or in 10-5M Ca2+, when the axonemes beat with a symmetric waveform. This cAMP-dependent regulation of motility was observed with the axonemes from which detergent-soluble material had been removed, indicating that the proteins responsible for the regulation still remained in the axonemes. Preliminary in vitro phosphorylation stdies have implicated two polypetides as candidates for the target protein of cAMP-dependent protein kinase: one with a molecular weight of 270 kD and the other with a much larger molecular weight.
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    Cell Motility and the Cytoskeleton 8 (1987), S. 345-359 
    ISSN: 0886-1544
    Keywords: alpha-actinin ; cytoskeleton ; muscle cells ; nonmuscle cells ; stress fiber ; myofibril ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study report the first development of a fluorescently labeled filamin. Smooth muscle was labeled with fluorscent dyes in order to study its interaction with stress fibers and myofibrils, both in living cells and in permeabilized cells. The labeled filamin bounds to the Z bands of isolated cross-striated myofibrils and to the Z bands and intercalated discs in both permeabilized embryonic cardiac myocytes and in frozen sections of adult rat venticle. In permeabilized embryonic chick myotubes, filamin bound to early myotubes but was absent at later stages. In living embryonic chick myotubes, the fluorescently labeled filamin was incorporated into the Z bands of myofibirls during early and late stages of develoment but was absent during an intermediate stages. In living cardiac myocytes, filamin-IAR was incorporated into nascent as well as fully formed sarcomeres throughout develoment. In permeabilized nonmuslce cells, labeled filamin bound to attachment plaques and foci of polygonal networks and to the dense bodies in stress fibers. The periodic bands of filamin in stress fibers had a longer spacing in fibroblasts than in epithelial cells. When injected into living cells, filamin was readily incorporated into stress fibers in a striated pattern. The fluorescent filamin bands were broader in injected cells, however, than they were in permeabilized cells. We have interpreted these results from living and permeabilized cells to mean that native filamin is distributed along the full lengh of the actin filaments in the stress fibers, with a higher concentration present in the dense bodies. A sarcomeric model is presented indicating the position of filamin with respect to other proteins in the stress fibers.
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    ISSN: 0886-1544
    Keywords: chemotaxis ; cell motility ; cellular polarity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Amebae of Dictyostelium discoideum normally chemotax to aggregation centers by assessing the direction of outwardly moving, nondissipating waves of the chemoattractant cAMP. However, D. discoideum amebae can also assess the direction of a relatively stable spatial gradient. We demonstrate that amebae migrating towards the “source” of a stable, spatial gradient move faster, extend fewer pseudopodia, and turn less frequently than amebae migrating away from the “source” in the same spatial gradient. In addition, amebae extend lateral pseudopods in a polarized fashion from the anterior half of the cell, and do so as frequently towards the source as away from the source. However, those formed towards the source more often produce a turn than those formed away from the source. These results suggest that there may be two decision-making systems, one localized in the pseudopods, and one along the entire cell body; they support the suggestion that Dictyostelium amebae may employ a temporal mechanism to assess the direction of a spatial gradient of chemoattractant.
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  • 40
    ISSN: 0886-1544
    Keywords: nuclear migration ; microtubules ; F-actin ; root hairs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A prominent feature of tip growth in filamentous plant cells is that the nucleus often migrates in step with the tip as it extends. We have studied this long-recognized but unexplained relationship in root hairs of the legume Vicia hirsuta by a variety of microscopic techniques. Using rhodaminyl lysine phallotoxin, and antitubulin antibodies, root hairs are shown to contain axial bundles of F-actin and a complex microtubular system. To the basal side of the nucleus the microtubules are cortical and net axial but in the region between nucleus and tip the arrangement is more complicated. Electron microscopic thin sections demonstrate that internal bundles of microtubles exist in addition to the plasma membrane-associated kind. Computerized deblurring of through-focal series of antitubulin stained hairs clarifies the three-dimensional organization: bundles of endoplasmic microtubules progress from the nuclear region toward the apical dome where they can be seen to fountain out upon the cortex.The relationship between nucleus and tip can be uncoupled with antimicrotubule herbicides. Time lapse video microscopy shows that these agents cause the nucleus to migrate toward the base. This contrary migration can be inhibited by adding cytochalasin D, which fragments the F-actin bundles.It is concluded that microtubules connect the nucleus to the tip but that F-actin is involved in basipetal migration as is known to occur when symbiotic bacteria uncouple the nucleus from the tip.
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  • 41
    ISSN: 0886-1544
    Keywords: capping ; concanavalin A ; glycoprotein ; membrane-cytoskeletal interactions ; thymocyte ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two major rat thymocyte surface glycoproteins, the leucocyte-common (L-C) antigen and the leucocyte sialoglycoprotein (LSGP), were induced to cap independently, using the specific monoclonal antibodies OX-1 and W3/13, respectively, and an appropriate fluorescently labeled second antibody layer. The caps were subsequently isolated from detergent extracted cells by a procedure involving gentle shearing.TRITC-phalloidin staining of the isolated caps demonstrated the presence of F-actin within these structures, and lectin-affinity staining after fractionation on SDS polyacrylamide gels revealed the presence of a concanavalin A (Con A) binding protein of relative molecular weight (Mr) 205,000, gp205, in both the L-C antigen and LSGP caps, but absent from the detergent-insoluble residue isolated from unchallenged cells. These results suggest that gp205 may be involved in the association of cross-linked glycoproteins with the cytoskeleton during capping.
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    ISSN: 0886-1544
    Keywords: vimentin ; hereditary disease ; proteolysis ; serum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Skin fibroblasts from two siblings with giant axonal neuropathy (GAN) were examined by both biochemical and immunocytochemical studies. The presence of intermediate filaments (IF) characteristic of these cells was affected by the growth conditions. Immediately after plating and during the following 24 hours the majority of the cells contained an IF “bundle”; however, after 4-6 days in culture only a minority of the cells retained this structure. We present evidence that trypsinization but not serum concentration is likely to influence the formation of the “bundle.” The results indicate that the formation of the “bundle” may result from a defective association or relationship between the cytoskeleton and the plasma membrane.
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    Cell Motility and the Cytoskeleton 8 (1987), S. 44-54 
    ISSN: 0886-1544
    Keywords: monoclonal antibody ; phosphoproteins ; basal bodies ; morphogenesis ; Paramecium ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The presence of phosphorylated proteins associated with microtubule organizing centers in tissue culture cells during mitosis has been demonstrated by the use of monoclonal antibodies raised against mitotic HeLa cells [Vandre et al., Proc. Natl. Acad. Sci. U.S.A. 81:4439-4443, 1984]. We report here that in Paramecium two of the mitosis specific antibodies, MPM-1 and MPM-2, decorate throughtout the cell cycle all the microtubule organizing centers (MTOCs) located in the cortex and in the oral apparatus (gullet). Immuno-electron microscopy showed that these antibodies labeled the electron-dense material surrounding basal bodies from which several microtubule networks as well as kinetodesmal fibers originate. During mitosis, these antibodies also stained other cortical cytoskeletal structures, the kinetodesmal fibers (MPM-1 and MPM-2) and the epiplasm (MPM-1). Among the different polypeptides recognized by the antibodies on immunoblots, three major ones of 60, 63, and 116 kDa were found to be common to the cortex (where several thousand ciliary basal bodies are anchored) and the oral apparatus (which comprises several hundred basal bodies around which various arrays of cytoplasmic microtubules are organized). Alkaline phosphatase treatment abolished the immunoreactivity of the polypeptides and the labeling observed by immunofluorescence. These results demonstrate that phosphorylated proteins are associated with all the known active microtubule organizing centers present in the cortex throughout the cell cycle of Paramecium. Furthermore they indicate that in Paramecium phosphorylation of proteins could also be involved in the cell cycle dependent dynamics of cortical cytoskeletal structures other than microtubules.
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    Cell Motility and the Cytoskeleton 8 (1987), S. 68-75 
    ISSN: 0886-1544
    Keywords: dynein ; flagella ; motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mutants with outer dynein arm defects or deficiencies all show a major reduction in beat frequency to about half the normal value; some of these mutants show an additional decrease in sliding velocity associated with reduced shear amplitude and an additional reduction in beat frequency, as well as other more minor modifications of the normal forward mode bending pattern. New mutants (ida98, pf30), which appear to be deficient in a subset of inner dynein arms show a reduction in sliding velocity that is primarily associated with a reduction in shear amplitude, with only a small reduction in beat frequency. These differences in motility phenotype between inner and outer dynein arm mutants suggest that inner and outer dynein arms may have distinct functions. The relatively large decrease in sliding velocity associated with partial loss of inner arms is consistent with earlier observations on pf23, a nonmotile mutant lacking inner arms, suggesting that inner arms may have an essential function in motility. The ability to generate reverse mode bending patterns is retained in some inner or outer dynein arm mutants, but appears to be decreased in those mutants which show reduced shear amplitude for the forward mode bending pattern.
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    Cell Motility and the Cytoskeleton 8 (1987), S. 85-90 
    ISSN: 0886-1544
    Keywords: blue damselfish ; motile iridophore ; microtubule ; colchicine ; EHNA ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Iridophores of the blue damselfish, Chrysiptera cyanea, responded to the sympathetic substance, norepinephrine by a shift towards longer wavelengths of the spectral peak of the light reflected by stacks of light-reflecting platelets (“coloring response”). All antimitotic reagents tested, i.e., colchicine, vinblastine, and podophyllotoxin, inhibited the response reversibly, while an actin inhibitor, cytochalasin B, did not. Erythro-9-[3-(2-hydroxynonyl)]adenine (EHNA), a dynein ATPase inhibitor, also blocked the iridophore response effectively. These results indicate that the tubulin-dynein system may be involved in the motility of iridophores, which is regarded as the simultaneous alteration of the distance between adjacent reflecting platelets within the cells.
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  • 46
    ISSN: 0886-1544
    Keywords: cell motility ; sensory transduction ; slime mold ; pseudopod formation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In an aggregation territory of Dictyostelium discoideum, outwardly moving, nondissipating waves of the chemoattractant cAMP sweep across each ameba. At the front of each wave, an ameba experiences an increasing temporal and a positive spatial gradient of cAMP. At the back of a wave, an ameba experiences a decreasing temporal and a negative spatial gradient of cAMP. Employing a perfusion chamber, we have mimicked the temporal dynamics of these waves in the absence of a spatial gradient and demonstrated that the frequency of lateral pseudopod formation and the frequency of turning are dramatically affected by the direction and dynamics of the temporal gradient. In addition, since an ameba will move in a directed fashion up a shallow, nonpulsatile gradient of cAMP, we also mimicked the increasing temporal gradient generated by an ameba moving up a shallow spatial gradient. The frequency of lateral pseudopod formation and the frequency of turning were depressed. Together, these results demonstrate that amebae can assess the direction of a temporal gradient of chemoattractant in the absence of a spatial gradient and alter both the frequency of pseudopod extension and turning, accordingly. Although these results do not rule out the involvement of a spatial mechanism in assessing a spatial gradient, they strongly suggest that the temporal dynamics of a cAMP wave or the temporal gradient generated by an ameba moving through a spatial gradient may play a major role in chemotaxis.
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  • 47
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 8 (1987), S. 61-67 
    ISSN: 0886-1544
    Keywords: platelets ; cytoskeleton ; vimentin ; microtubules ; immunofluorescence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human and bovine platelets contain a 58,000-dalton vimentinlike protein that cross-reacts with antivimentin antibody. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blots indicate that this protein is present in whole platelet lysates and triton insoluble cytoskeletons. Transmission electron microscopy of platelets reveals an isotropic network of individual intermediate filaments distributed throughout the platelets. High salt, triton extracted, glutaraldehyde and tannic acid fixed platelets reveal 10-nm filaments that can be seen to form a peripheral ring, as well as an isotropic network in the body of the cells. Indirect immunofluorescence of resting and spread platelets demonstrates a circumferential staining pattern close to the cell membrane, with additional fibrillar staining throughout the platelets. Our data suggest that the 58,000-dalton vimentinlike protein may be associated with the microtuble coil and the plasma membrane, and may thus help to maintain the resting platelet's discoid shape.
    Additional Material: 3 Ill.
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  • 48
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 8 (1987) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 49
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 8 (1987), S. 76-84 
    ISSN: 0886-1544
    Keywords: flagella ; starfish spermatozoon ; proximal centriole ; bend direction ; bend asymmetry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Since starfish spermatozoa have spherical heads, it is not easy to determine the topographical relationship of the axoneme to the directions of the flagellar bends, the principal, and the reverse bends as defined by Gibbons and Gibbons [J. Cell. Biol. 1972, 63:970-985]. The demembranated spermatozoa are known to take the quiescent “cane” shape with a sharp principal bend at the proximal region of the flagellum in the presence of high concentration of Ca2+. When such spermatozoa were placed on a grid for electron microscopy, fixed with osmic acid vapor, washed with distilled water, and negatively stained with urany1 acetate, the head of the spermatozoon was disrupted and dispersed disclosing the proximal centriole at at the proximal end of the flagellum. The proximal centriole was always found on the concave side of the “cane” -shaped flagella. Electron microscopy of the serial thin sections of intact and demembranated spermatozoa revealed that the doublet microtobules numbers 5 and 6 were contained in the convex edge of the principal bend.
    Additional Material: 7 Ill.
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  • 50
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 105-113 
    ISSN: 0886-1544
    Keywords: video-microscopy ; colloidal gold ; immunocytochemistry ; microtubules ; receptors ; saltatory motion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We 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 sections.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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