bluuebunny/crossref_metadata_2025_split huggingface dataset:
Motility of human polymorphonuclear neutrophils: Microscopic analysis of substrate adhesion and distribution of F‐actin
Authors: Sullivan J. A. , Mandell G. L. 
Published: February 2005

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 redistribution of F‐actin.
Microtubule‐containing detergent‐extracted cytoskeletons in sea urchin eggs from fertilization through cell division: Antitubulin immunofluorescence microscopy
Authors: Balczon Ron , Schatten Gerald 
Published: February 2005

AbstractThe microtubule‐containing structures that appear in eggs during fertilization and cell division in the sea urchins Lytechinus variegatus and Arbacia punctulata were detected by antitubulin immunofluorescence microscopy of detergent extracted cytoskeletal preparations. The extraction buffer, which is composed of 0.55 mM MgCl2, 10 mM EGTA, 25 mM MES, 25% glycerol, 1% Nonidet P‐40, and 25 μM PMSF, pH 6.7, allows for dramatically improved fluorescent images compared to those obtained using conventional staining procedures, with residual background staining being reduced to near zero.The immunofluorescent images obtained using this technique provide information on several motile events that occur during the first cell cycle. This technique demonstrates that all of the cytoplasmic microtubules are associated with the incorporated sperm's centrioles during female pronuclear migration. This changes during the centration of the male and female pronuclei at which time a monastral array of microtubules forms in the egg's cytoplasm. A large proportion of the monastral microtubules do not appear to be associated with the centrioles. At prophase and early metaphase, the centrioles are the dominant microtubule organizing centers (MTOCs) consistent with mitotic theories that the kinetochore catches, but does not initiate, microtubules. Observations of intercentriolar distances show that there are three stages of pole separation during the first cell cycle. The initial separation occurs during pronuclear centration, the second during the streak stage, and the final one during the late stages of mitosis. At telophase, polar microtubules appear to extend into the cortex supporting the cell surface at all regions except the presumptive cleavage site.
Chromosome movement during meiotic prophase in crane‐fly spermatocytes. II. Analysis of polarization of chromosomes and their association with the nuclear envelope
Authors: LaFountain James R. 
Published: February 2005

AbstractAssociation of bivalent chromosomes with the astral centers and nuclear envelope was analyzed in crane‐fly spermatocytes during the final hours of diakinesis. In contrast to other systems in which movement of chromosomes during diakinesis correlates with the clustering of bivalents near the astral centers, such clustering is not prevalent in crane‐fly spermatocytes. Polarization indices of bivalents calculated 5 to 10 minutes before the end of diakinesis provided evidence for polarization of only a fraction of all bivalents. Similar results were obtained in a large number of fixed cells in which asters and chromosomes were preferentially stained. Ultrastructural analysis of cells in late diakinesis revealed significant contact between bivalents and the nuclear envelope in all 46 cells that were analyzed. The extent of contact in some cells was greater than in others. Sites of contact included the telomeric ends of bivalents, and in some cases the distribution of contact sites suggested the possible involvement of centromeres in chromosome‐nuclear envelope association. The results are consistent with the hypothesis that a dynamic interaction between chromosomes and nuclear envelope may exist during late prophase, when the movement of chromosomes is known to occur.
Mitochondrial motility in axons: Membranous organelles may interact with the force generating system through multiple surface binding sites
Authors: Martz Dean , Lasek Raymond J. , Brady Scott T. , Allen Robert D. 
Published: February 2005

AbstractIn living tissue, membrane‐bound organelles, including mitochondria, move along parallel cytoplasmic pathways. Motion is directed and tends to be confined to a single path. Deviations from this single path motion are rare. When present, however, they tend to occur at points of intersection of cytoskeletal linear elements (LE). Such intersections are relatively uncommon in intact axons and extruded axoplasm. However, we have found that such intersections can be produced in extruded preparations by shear forces directed tangential to the axoplasmic surface.We have studied the detailed behavior of mitochondria in extruded squid axoplasm. Special attention was directed to the relationship between mitochondrial shape changes and orientation of cytoskeletal LE. The most striking of these changes in shape is branching. In this process, the mitochondrion transiently assumes a triradial (three‐ended) shape. This appearance may be maintained for seconds to minutes before the normal cylindrical shape is resumed by absorption of either the newly formed end or, more commonly, one of the original ends. The frequency of branching appears to be dependent on the degree of cytoskeletal organization. It becomes more common as the number of apparent intersections between cytoskeletal LE increases. Further, the formation of new ends seems to occur along paths defined by cytoskeletal elements.These observations suggest that the mitochondrial membrane is multivalent. That is, it contains multiple sites capable of interacting with the axonal force generation apparatus. Furthermore, LE in the cytoskeleton may indicate the paths along which these interactions are permissible.
Nucleotide specificity for reactivation of organelle movements in permeabilized axons
Authors: Forman David S. , Brown Kurt J. , Promersberger Mark W. , Adelman Mark R. 
Published: February 2005

AbstractIn a permeabilized axon model, exogenous ATP can reactivate intraaxonal saltatory organelle movements (microscopically visible manifestations of fast axonal transport). We have studied the dependence of the reactivated movements on the ATP concentration and have also examined the nucleotide specificity of the reactivation. Organelle transport was visualized in isolated lobster giant motor axons using Nomarski optics and video microscopy. The axons were permeabilized with saponin, and movement was reactivated with ATP or other nucleotides. Some slight movement was seen with ATP concentrations as low as 10 μM. The velocity and frequency of the reactivated transport increased with increasing ATP concentrations up to about 5 mM. Movement was also reactivated by deoxyadenosine triphosphate, but not by AMP–PNP (a nonhydrolyzable ATP analogue), ADP, or AMP. Although other nucleotides (CTP, GTP, UTP, ITP) could reactivate transport, movement equivalent to that produced by 0.1 mM ATP was only seen with tenfold or greater concentrations of the other nucleotides. This pattern of specificity is consistent with the hypothesis that a dynein‐like ATPase, rather than a myosin, is involved in fast axonal transport.
Trifluoperazine‐induced changes in swimming behavior of paramecium: Evidence for two sites of drug action
Authors: Otter Tim , Satir Birgit H. , Satir Peter 
Published: February 2005

AbstractTrifluoperazine (TFP), a drug that binds to Ca2+‐calmodulin (CaM) complexes, altered swimming behavior not only in living paramecia, but also in reactivated, Triton‐extracted “models” of the ciliate. By comparing the responses of living cells and models, we have ascertained that two sites of drug action exist in paramecium cilia. Swimming movements were recorded in darkfield stroboscopic flash photomicrographs; this permitted accurate quantitation of velocities and body‐shape parameters. When living paramecia were incubated in a standard buffer containing 10 μM TFP, their speed of forward swimming fell over several minutes and their bodies shortened. Untreated paramecia backed up repeatedly and frequently upon transfer to a solution containing barium ions (the “barium dance”), but cells preincubated in TFP did not “dance.” Instead they swam forward slowly for long periods of time without reversing and occasionally then exhibited abnormally prolonged reversals. W7 effects on swimming mimicked low doses of TFP, and the analog W5 did not visibly alter normal swimming patterns. These results suggest that TFP induces a decrease in the intracellular pCa of living paramecia, perhaps by reducing the efficiency of a calmodulin‐activated calcium pump in the cell membrane. Paramecia extracted with Triton X‐100 and reactivated to swim forward (7 ≥ pCa ≥ 6) were not affected by addition of up to 40 μM TFP to the reactivation medium. We conclude that the main drug effect in living cells is probably not at the axoneme. However, at low pCa, TFP directly affected the ciliary axoneme to shift its behavior to one characteristic of a higher pCa: TFP inhibited backward swimming in models reactivated at pCa < 6; instead they swam forward or rocked in place. The mechanism of ciliary reversal in paramecium may therefore depend on an axonemal Ca+‐sensor, possibly bound CaM, which is affected by TFP only at low pCa, as has been postulated for other types of cilia.
Differential distribution and function of microtubules and microfilaments in sea urchin coelomocytes
Authors: Edds Kenneth T. 
Published: February 2005

AbstractSea urchin coelomocytes were used as a model system to investigate the distribution and role of microtubules and microfilaments in cell spreading and filopodial formation. By using immunoblot characterized antisera to tubulin and actin coupled with immunofluorescence techniques, cellular protrusions were seen to contain actin filaments but no microtubules. Cells depleted of MT's by cold and colcemid treatments could attach, spread, and transform to the filopodial morphology normally.
Mechanics of cytogels I: Oscillations in Physarum
Authors: Oster G. F. , Odell G. M. 
Published: February 2005

AbstractThe contractility of actomyosin gels is the basis for a variety of cellular motility phenomena. We present here a mechanical analysis of contractile gels. By making certain hypotheses on the chemical regulation of cytogel contraction we formulate a model for the rhythmic contractions of plasmodia in the slime mold Physarum polycephalum which is in accord with a number of experimental observations.
The locomotion of dissociated sponge cells: A cell‐by‐cell, time‐lapse film analysis
Authors: Gaino Elda , Zunino Lidia , Burlando Bruno , Sarà Michele 
Published: February 2005

AbstractThe production of both lamellipodia and peculiar thin protuberances (scleropodia) characterizes the preaggregative motility of cells after dissociation of the sponge Clathrina.The locomotory paths taken by cells before aggregation were recorded by time‐lapse microcinematography. Changes of direction in successive 50‐s time intervals and 50‐s mean velocities of each cell were both taken into account as statistical variables. Their distributions give probability density curves that seem to fit bilateral exponential functions. The analysis of the angles of turn indicates a tendency for the cells to persist in their direction of motion and to make counter‐clockwise turns. Implications of such in vitro cellular behaviors in aggregative and in vivo processes are suggested.
An approach to digital image analysis of bending shapes of eukaryotic flagella and cilia
Authors: Baba Shoji A. , Mogami Yoshihiro 
Published: February 2005

AbstractA novel method of digital image analysis of the bends of eukaryotic flagella and cilia was devised. In the analysis system, all image pixels were systematically extracted and processed to measure angular direction and curvature. Simulation experiments on theoretical model pictures of flagella with sine‐generated or arcstraight line bending waves demonstrated that the method can be used with considerable high accuracy. This method then revealed abrupt changes in slope of the curvature in sperm flagella and embryo cilia of the sea urchin, Hemicentrotus pulcherrimus. This indicates that the digital image processing used may be helpful in the study of flagellar and ciliary movements.
A model for fast axonal transport
Authors: Blum J. J. , Reed M. C. 
Published: February 2005

AbstractA 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.
Regulation of ciliary motility by membrane potential in Paramecium: A role for cyclic AMP
Authors: Bonini Nancy M. , Gustin Michael C. , Nelson David L. 
Published: February 2005

AbstractThe 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.
Regulation of cell motility, morphology, and growth by sulfated glycosaminoglycans
Authors: Klebe Robert J. , Escobedo Laura V. , Bentley Kevin L. , Thompson Laura K. 
Published: February 2005

AbstractDue to the recent observation that heparin binds to several growth factors and cell adhesion molecules, the effect of heparin on biological processes governed by growth factors and cell adhesion molecules was investigated. Pharmacological doses of heparin were found to alter cell growth rate, cellular morphology, and cell motility.Concentrations (μg/ml) of heparin or dextran sulfate decreased cell growth rate, but not the final cell density attained in plateau phase. The effect of heparin on cell growth rate was most pronounced when cells were cultured in low concentrations of serum. A heparin‐induced decrease in cell growth rate could be reversed by addition of platelet‐derived growth factor (PDGF), a heparin‐binding growth factor.Heparin altered the morphology of all cell lines studied to various degrees. The effect of heparin on cell morphology was quantitated by measuring the heparin‐induced change in cell surface area. HT‐1080 and HeLa cells nearly doubled in surface area upon exposure to 10μg/ml heparin. Since several heparin‐binding cell adhesion proteins mediate both cell spreading and cell migration, the influence of heparin on cell migration was investigated with an improved version of the phagokinetic track technique. Low concentrations of heparin and dextran sulfate were found to increase the rate of cell migration in a dose‐dependent fashion.Since the quantitative effect of heparin on cell growth rate, morphology, and migration depends on the cell line studied, it is suggested that three separate phenomena may be involved. The results presented indicate a central role for sulfated glycosaminoglycans in the control of both cell growth and cell‐cell interactions.
Influence of translocation track on the motion of intra‐axonally transported organelles in human nerve
Authors: Lynn Marc P. , Atkinson Mark B. , Breuer Anthony C. 
Published: February 2005

AbstractThe mechanism by which organelles are transported bidirectionally in axoplasm is still unknown; however, evidence of a key role for microtubules in many nonmammalian models has been established. We have observed common or shared tracks within the axoplasm of human nerves along which multiple organelles of varying size and shape are bidirectionally transported. Organelles traveling anterogradely and retrogradely were visualized by video‐enhanced differential interference contrast optics and analyzed with the aid of computer‐image‐processing techniques.Speeds of translocating organelles were determined at eight to 16 translocation points along a path or “track.” Each translocation speed was plotted against its corresponding position on the track to develop a “speed/position diagram.” Regardless of mean organelle speed or direction of motion, organelles sharing a common track exhibited similar patterns of “speeding up” and “slowing down” relative to position along the track. Speed position data for organelles translocating the local axonal region of a common track showed no unique patterns (not different from a uniform distribution, p < 0.05). The unique speed/position patterns exhibited by common tracks were not necessarily related to the patterns of other tracks in the immediate vicinity (distance between tracks of < 0.50 μm). These findings suggest that (1) there are “common tracks” shared by organelles moving retrogradely and anterogradely; (2) both the organelles and the “track” associated with its translocation play a role in the resultant motion of that organelle; (3) the influence exerted by a common track on the motion of an organelle results in a pattern of speed changes related to position along the track.
Evidence for an interaction between the cell surface and intermediate filaments in cultured fibroblasts
Authors: Green Kathleen J. , Goldman Robert D. 
Published: February 2005

AbstractIntermediate filaments (IF) were found in close proximity to the plasma membrane in substrate attached baby hamster kidney cells (BHK‐21) and chick embryo fibroblasts (CEF) as well as cells removed from their substrate in the absence of trypsin. However, in cells removed with trypsin, it appeared that IF had retracted away from the membrane. In cells with abundant extracellular matrix (ECM), colchicine induced massive cables of IF, which appeared to interact with specialized areas of the inner plasma membrane. In cells lysed to extract most microfilaments and cytoplasmic constituents, the intact IF network which remained was closely associated with the ECM. From these ultrastructural observations it was concluded that IF interact in some way with a “cell membrane complex” defined as comprising the plasma membrane and molecules attached to its inner and outer surfaces.In order to investigate the possibility that components of the membrane complex may co‐isolate with IF, native intermediate filaments (NIF) were prepared. In addition to the structural subunits and other associated polypeptides, a ∼220 kd species which reacted specifically with antibodies directed against the ECM protein fibronectin (FN) was observed; 220 kd was still present after NIF were isolated under pH conditions where FN is more soluble, suggesting that its presence was not simply due to the coprecipitation of two insoluble proteins. Immunofluorescence and immunogold localization confirmed that FN is a component of the cell membrane complex with which IF appeared to interact.
Rhamnolipid from Pseudomonas aeruginosa inactivates mammalian tracheal ciliary axonemes
Authors: Hastie A. T. , Hingley S. T. , Higgins M. L. , Kueppers F. , Shryock T. 
Published: February 2005

AbstractIsolated ciliary axonemes from pig trachea were exposed to increasing concentrations of purified Pseudomonas aeruginosa rhamnolipid. This is a defined ciliary system allowing observation of direct impairment of functional axonemes. Axonemal motility and ATPase activity were decreased in proportion to rhamnolipid concentrations. ATPase‐associated proteins observed in sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and dynein arms seen in ultrastructural cross sections progressively disappeared from axonemes with exposure to rhamnolipid. These four independent measures establish that the rhamnolipid removes the ATPase‐containing outer dynein arms from the ciliary axoneme, thereby rendering the axoneme immotile.
Localization of sea urchin egg cytoplasmic dynein in mitotic apparatus studied by using a monoclonal antibody against sea urchin sperm flagellar 21S dynein
Authors: Hisanaga Shin‐Ichi , Tanaka Takeshi , Masaki Tomoh , Sakai Hikoichi , Mabuchi Issei , Hiramoto Yukio 
Published: February 2005

AbstractA monoclonal antibody against sea urchin (Hemicentrotus pulcherrimus) sperm flagellar 21S dynein was characterized and sued to identify and localized cytoplasmic dynein of sea urchin eggs by the methods of immunoblotting and indirect immunofluorescence microscopy. D57, the monoclonal antibody used in this study, was directed to the Aβ polypeptide of 21S dynein. D57 stained sperm flagella specifically but did not inhibit Mg‐ATPase activity of 21S dynein, its recombination ability with NaCl‐extracted axonemes, or the movement of demembranated sperm. D57 cross‐reacted with sea urchin egg cytoplasmic dynein. High molecular weight cytoplasmic dynein polypeptide which had the same electrophoretic mobility s flagellar dynein. A chains was the only polypeptide that reacted with D57 in the crude extract from unfertilized sea urchin eggs. Indirect immunofluorescence observations showed that the mitotic apparatus was stained most intensely in the frozen sections and lysed eggs. In the mitotic apparatus isolated at metaphase, the half spindles were stained more strongly than the astral regions. The regions near chromosomes in the half spindle appeared to be stained particularly. Staining of the interzone was also observed in the mitotic spindle isolated at anaphase. Comparison of the staining patterns for cytoplasmic dynein with that for tubulin suggested that cytoplasmic dynein was localized where microtubules were densely organized, but its distribution may not necessarily be identical with that of microtubules.