bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mutants in paramecium tetraurelia defective in their axonemal response to calcium
Authors: Hinrichsen Robert D. , Saimi Yoshiro , Hennessey Todd , Kung Ching 
Published: February 2005

AbstractSix mutants of Paramecium tetraurelia, which display altered axonemal responses to Ca++, are described. The mutants, designated atalantas, are impaired in their ability to swim backward when stimulated by ions or heat; instead they spin very rapidly in one place. Three mutants, ataA1–3, are completely unable to swim backward. The three lines, however, can be distinguished from one another by their forward swimming velocities. The remaining three mutants are leaky. ataB swims backward briefly when stimulated, then stops and spins in place. ataC and ataD are extremely leaky and only display the spinning phenotype at elevated temperatures. An electrophysiological analysis reveals that all six mutants have normal membrane properties, including the Ca++ inward current under voltage clamp. When the membrane is disrupted so as to allow the axoneme free access to Ca++, wild‐type cells swim backward, but the mutants do not. These data indicate the site(s) of lesion in the mutants is in the axoneme or in some step linking Ca++ influx and the axoneme, not within the ciliary membrane. These mutants may be useful in investigating the role of Ca++ in the regulation of axonemal motion.
Ca2+‐dependent contraction of human lung fibroblasts treated with triton X‐100: A role of Ca2+‐calmodulin‐dependent phosphorylation of myosin 20,000‐dalton light chain
Authors: Masuda Hirohisa , Owaribe Katsushi , Hayashi Hiroshi , Hatano Sadashi 
Published: February 2005

AbstractHuman lung fibroblast MRC‐5 cells treated with Triton X‐100 (MRC‐5 cell models) were able to contract in the presence of MgATP and Ca2+ of more than 1 μM. Immunofluorescence microscopy with antibodies to actin and myosin 20,000‐dalton (20 Kd) light chain revealed that stress fibers were prominent in MRC‐5 cell models. Use of a fluorescent actin probe, 7‐nitrobenz‐2‐oxa‐1,3‐diazole‐phallacidin permitted visualization of contraction of the stress fibers in the presence of MgATP and Ca2+. Of the proteins in MRC‐5 cell models, only a myosin 20 Kd light chain was phosphorylated in a Ca2+‐dependent manner. This Ca2+‐dependent phosphorylation of the 20 Kd light chain closely corresponded with the contraction of MRC‐5 cell models: 1) Both phosphorylation of the 20 Kd light chain and contraction of MRC‐5 cell models were inhibited by calmodulin antagonists such as N‐(6‐aminohexyl)5‐chloro‐1‐napthalene sulfonamide. 2) The threshold Ca2+ concentration for phosphorylation of the 20 Kd light chain was similar to that for contraction of MRC‐5 cell models. Both were lowered by exogenous calmodulin in a concentration‐dependent manner. 3) The 20 Kd light chain was thiophosphorylated by incubation of MRC‐5 cell models with an ATP analogue, adenosine 5′‐0‐(3‐thiotriphosphate) only in the presence of Ca2+. After this treatment, MRC‐5 cell models lost the Ca2+‐dependence for contraction. These results indicate that Ca2+‐calmodulin‐dependent phosphorylation of myosin 20 Kd light chain is required for contraction of MRC‐5 cell models.
Axonal elongation as a stochastic walk
Authors: Katz Michael J. , George Edwin B. , Gilbert Leslie J. 
Published: February 2005

AbstractA new formula calculates rates of directed axonal growth (elongation or retraction) using measurements of growth cone movements. By explicitly separating changes in axonal length from other nonelongational growth cone movements, the calculated rates reflect the detailed cellular growth mechanisms more directly than previous growth measures. In addition, the formula produces three distinct parameters of axonal elongation: n, a growth step rate; s, a growth step size; and P, a probability that a growth step leads to axonal elongation. For normal and regenerating individual chick and frog axons in culture, the formula has quantitated the following differences: the axon itself can elongate more rapidly in the chick, and the axon elongates in smaller steps in the chick. The underlying dynamics of growth of regenerating axons are quite similar to normal axons, but, in the short term, regenerating axons elongate in larger steps and at a slower rate. The distribution of these new rate measurements suggests that the elongation of axons can be usefully modelled as a one‐dimensional stochastic walk.
Formation of myofibrils in spreading chick cardiac myocytes
Authors: Sanger Joseph W. , Mittal Balraj , Sanger Jean M. 
Published: February 2005

AbstractCardiac myocytes were isolated from 5–6‐day‐old chick embryos and allowed to spread in culture. The distribution of alpha‐actinin in the cells was followed for five days in culture by exposing permeabilized cells to rhodamine‐labeled alpha‐actinin and also by injecting the labeled alpha‐actinin into living myocytes. In addition to labeling the Z bands of sarcomeres, the added alpha‐actinin also labeled small particles that were usually arranged periodically in linear arrays with a spacing between particles of 0.3–2.0 μm. Actin was localized between the particles of alpha‐actinin by means of fluorescein‐labeled heavy meromyosin. The punctate localization of alpha‐actinin was prominent in pseudopods, behind ruffles, and at the periphery of spreading cells. Long rows of particles of alpha‐actinin were often parallel to one another with the alpha‐actinin particles in register. These linear arrays appeared to merge laterally to form strands with broader concentrations of alpha‐actinin. Other linear arrays were parallel to myofibrils in the cell and some extended outward from the ends of myofibrils. We conclude that during spreading of cardiac myocytes, myofibrils form at the cell periphery behind the extending margins of the cell, and that the aggregates of alpha‐actinin found in these areas are nascent Z bands in the forming myofibrils.
Analysis of the morphology and function of primary cilia in connective tissues:A cellular cybernetic probe?
Authors: Poole C. Anthony , Flint Michael H. , Beaumont Brent W. 
Published: February 2005

AbstractMore than 300 primary cilia have been identified electronmicroscopically in a variety of embryonic and mature connective tissue cells. To further define the enigmatic function of these cilia, we examined the interrelationships between the basal apparatus and cytoplasmic organelles and the ciliary shaft and the extracellular matrix. The basal diplosome was consistently associated with the secretory organelles including the maturing face of the Golgi complex, Golgi vacuoles and vesicles, the microtubular network, the plasma membrane, and coated pits and vesicles. Small vesicles and amorphous granules were also observed within the ciliary lumen and adjacent to the ciliary membrane. Microtubule‐membrane bridges linked axonemal tubules to the ciliary membrane. The position, projection, and orientation of the axoneme were influenced by the structural organisation and mechanical properties of the matrix and frequently caused angulation of the ciliary shaft relative to the basal body. Located midway between the secretory apparatus and the extracellular matrix, primary cilia would appear ideally situated to mediate the necessry interaction between the cell and its surrounding environment prerequisite to the formation and maintenance of a functionally effective matrix. We propose that primary cilia in connective tissue cells could act as multifunctional, cellular cybernetic probes, receiving, transducing, and conducting a variety of extrinsic stimuli to the intracellular organelles responsible for effecting the appropriate homeostatic feedback response to changes in the extracellular microenvironment.
Bending patterns of Chlamydomonas flagella: III. A radial spoke head deficient mutant and a central pair deficient mutant
Authors: Brokaw C. J. , Luck D. J. L. 
Published: February 2005

AbstractFlash photomicrography at frequencies up to 300 Hz and computer‐assisted image analysis have been used to obtain parameters describing the flagellar bending patterns of mutants of Chlamydomonas reinhardtii. All strains contained the uni1 mutation, to facilitate photography. The radial spoke head deficient mutant pf17, and the central pair deficient mutant, pf15, in combination with suppressor mutations that restore motility without restoring the ultrastructural or biochemical deficiencies, both generate forward mode bending patterns with increased shear amplitude and decreased asymmetry relative to the “wild‐type” uni1 flagella described previously. In the reverse beating mode, the suppressed pf17 mutants generate reverse bending patterns with large shear amplitudes. Reverse beating of the suppressed pf15 mutants is rare. There is a reciprocal relationship between increased shear amplitude and decreased beat frequency, so that the velocity of sliding between flagellar microtubules is not increased by an increase in shear amplitude. The suppressor mutations alone cause decreased frequency and sliding velocity in both forward and reverse mode beating, with little change in shear amplitude or symmetry.
Proteins closely similar to flagellar tektins are detected in cilia but not in cytoplasmic microtubules
Authors: Amos W. B. , Amos L. A. , Linck R. W. 
Published: February 2005

AbstractAffinity‐purified antibodies against Strongylocentrotus purpuratus sperm flagellar tektin polypeptides have been tested for cross‐reactivity with microtubules isolated from various sources, using indirect immunofluorescent staining and antibody binding to nitrocellulose replicas of SDS polyacrylamide gels. The antitektins reacted with sperm tail axonemes from four genera of sea urchins and with cilia from sea urchin embryos. Antibody binding was observed only if the specimens were prefixed by methods that would not preserve them well at an ultrastructural level. However, even after such fixation regimes, no antibody binding was detected to cytoplasmic microtubule arrays in the same embryos, to mitotic spindles isolated from sea urchin or to gill cilia from a mollusc. We conclude that, if tektins are present in sea urchin egg cytoplasmic microtubules, they are sufficiently different from the sperm tektins to have no common strongly antigenic determinants.
Tetrahymena cell model exhibiting Ca‐dependent behavior
Authors: Izumi Akemi , Miki‐Noumura T. 
Published: February 2005

AbstractUsing Tetrahymena pyriformis, strain w, and Tetrahymena thermophila, B‐1868, we prepared cell models that showed ciliary reversal with change in Ca‐ion concentration, as was also noted for the Paramecium cell model. No differences could be found between these two strains in the reactivation state, and their response to environmental conditions was essentially the same. The reactivation rate was 90% or more. Swimming velocity of the cell model was found to be 200 ± 49 μm/sec at 25.0°C ± 0.5°C, while the velocity for the living cells was 527 ± 101 μm/sec. Swimming velocity with change in environmental conditions, such as pH, Mg‐ATP, and Ca‐ion concentrations, was studied. Compared to the cell model of Paramecium, the Tetrahymena cell model had higher sensitivity toward Ca‐ion in the reactivation medium. The effects of chlorpromazine, and inhibitor of calmodulin, on the swimming behavior of the cell models were studied.
Chromosome movement during meiotic prophase in crane‐fly spermatocytes: III. Microtubules and the effects of Colcemid, nocodazole, and vinblastine
Authors: LaFountain James R. 
Published: February 2005

AbstractThe effects of Colcemid, nocodazole, and vinblastine on microtubules and on the movement of chromosomes during late diakinesis were investigated in spermatocytes of the crane fly Nephrotoma suturalis. The kinds of movements observed in untreated cells—sex bivalent rotations, sex bivalent excursions, and rotations and positional changes of autosomal bivalents—also were observed in drug‐treated cells. These results were obtained in living cells in which the disruption and inhibition of microtubule assembly had been confirmed with polarized light microscopy. Effects of Colcemid and nocodazole also were assessed in fixed cells using electron microscopy. The results are in agreement with a hypothesis that microtubules are not a force‐generating component of the molecular machinery that brings about prophase movements.
Use of multiple monoclonal antibodies to characterize the major microtubule‐associated protein in sea urchin eggs
Authors: Bloom George S. , Luca Francis C. , Collins Christine A. , Vallee Richard B. 
Published: February 2005

AbstractMicrotubules assembled from sea urchin eggs with the use of taxol contain a 77,000‐dalton protein as the major nontubulin component [Vallee and Bloom (1983): Proc Natl. Acad. Sci. U.S.A. 80:6259–6263]. We have raised five monoclonal antibodies to this protein to aid in its characterization. Immunoblot analysis of the sea urchin microtubule purification fractions indicated that the protein copurified quantitatively with microtubules. All five antibodies stained the mitotic spindle of dividing sea urchin eggs by immunofluorescence microscopy, indicating that the protein was a component of the mitotic spindle and suggesting that it was actually localized on microtubules in vivo. Immunofluorescent staining of higher resolution was observed in a subpopulation of the coelomic cells found in adult sea urchins, confirming that the 77,000‐dalton protein is indeed present on microtubules in vivo. Because taxol was not used for the immunofluorescence experiments, we conclude that the microtubule‐associated protein (MAP)‐like behavior of the 77,000‐dalton protein in vitro was not induced artifactually by taxol. To determine whether this protein is a component of sea urchin microtubules in general, cilia obtained from blastula stage embryos and sperm tail flagella were analyzed with the antibodies. The protein was undetectable by both immunoblot analysis and immunofluorescence microscopy in both preparations of axonemal microtubules. These results indicated that the 77,000‐dalton MAP is restricted to cytoplasmic and mitotic microtubules in the sea urchin. Furthermore, in view of its particular abundance in embryos, whose microtubules are devoted substantially to mitosis, the 77,000‐dalton MAP is likely to play an important role in regulating the activity of mitotic spindle microtubules in the sea urchin.
Orthokinetic and klinokinetic responses of human polymorphonuclear leucocytes
Authors: Keller H. U. , Zimmermann A. 
Published: February 2005

AbstractEvidence is presented to show that klinokinesis, which was previously demonstrated in bacteria and amoeba only, may also occur in metazoan cells. The chemotactic peptide formyl‐Met‐Leu‐Phe (fMLP) elicited orthokinetic and klinokinetic responses of human blood‐borne polymorphonuclear leucocytes (PMNs) under the test conditions used. Increased speed (orthokinesis) was due to an increase in the proportion of migrating cells as well as in the speed of the locomoting subset. The klinokinetic effect was manifested by a decrease in the klinolocomotion index, the mean angle of changes in direction ⩾ 90°, and the frequency of turns ⩾ 90°. The klinolocomotion index was inversely related to speed. This explains the synergistic effect of klinokinesis and orthokinesis in this system. Colchicine alone had and orthokinetic effect which was exclusively due to alterations in the proportion of migrating cells and it altered the turning behaviour without exerting a klinokinetic effect. However, colchicine had marginal orthokinetic and klinokinetic effects on fMLP‐stimulated cells resulting in reduced translocation. The relationship between klinokinesis and mean angle or frequency of turns has been analysed. Klinokinesis was a substantial though not the major element of the chemokinetic response to fMLP under the conditions used. No other metazoan cells have been shown to possess such a complete pattern of responses, including orthokinesis, klinokinesis, and chemotaxis, which regulate locomotion.
A Ca2+ insensitive actin‐crosslinking protein from Dicytostelium discoideum
Authors: Brown Susan S. 
Published: February 2005

AbstractWe 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.
Alteration of the distribution of intermediate filaments in PtK1 cells by acrylamide II: Effect on the organization of cytoplasmic organelles
Authors: Eckert Barry S. 
Published: February 2005

AbstractThe distribution and motility of cytoplasmic particles was examined in PtK1 cells in which intermediate filament networks had been disrupted by acrylamide. In these cells, particles (mitochondria and vesicles) accumulated near the cell center although saltatory movements continued. This left a broad sheet of agranular cytoplasm at the periphery of the cell. Particles were capable of movement into this sheet. Intermediate filaments were absent in the peripheral cytoplasm although microtubules remained in a normal configuration. Particles apparently move along the microtubules. These results indicate that particle movement along microtubules is not dependent upon the normal configuration of intermediate filaments. It is suggested that intermediate filaments are necessary for normal organelle distribution and serve as a matrix with which particles can associate to maintain position.
The lack of interaction between vinculin and actin
Authors: Otto Joann J. 
Published: February 2005

AbstractVinculin 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.
A protein of 175,000 daltons associated with striated rootlets in ciliated epithelia, as revealed by a monoclonal antibody
Authors: Klotz Catherine , Bordes Nicole , Laine M. Christine , Sandoz Daniel , Bornens Michel 
Published: February 2005

AbstractBasal bodies from laying quail oviduct were semipurified and used as immunogen to produce monoclonal antibodies. On 38 clones obtained and among those staining the apical pole of the ciliated cell, CC‐310 was chosen because it labeled the apical region with a punctated aspect, suggesting a staining of basal bodies or of basal body‐associated structures; the basal pole was also labeled.The ultrastructural localization performed by the immunogold technique showed that the labeling was mainly associated with the striated rootlets. The basal feet, the side of the basal bodies, and the basal poles of the demembranated cells were also decorated. The identification of the antigen performed by immunoblots of deciliated cortices revealed two proteins of 175,000 and 40,000, whereas immunoblots of basal bodies showed only the 175,000‐mw protein. The possibility of these two proteins sharing the same epitope, located at both poles of the cell, is discussed.Immunofluorescence ascertained that CC‐310 decorated the striated rootlets in ciliated epithelia from other species: mussel, frog, and human tissue. Finally, when tested on cultured cell lines, CC‐310 labeled the centrosome and its associated rootlets on PtK2 during interphase. During mitosis the poles of the mitotic spindle were stained without any apparent rootlet‐like structure.
Patterns of flagellar wave propagation in Crithidia oncopelti at increased viscosities
Authors: Hirons M. R. , Holwill M. E. J. 
Published: February 2005

AbstractIn its normal culturing environment, the trypanosomid flagellate Crithidia oncopelti propagates basally‐directed planar waves, but may under certain conditions exhibit base‐to‐tip wave propagation in what is regarded as an avoidance response. The beat frequency and wave shape in both modes of beating are dependent on the viscosity of the swimming medium; viscosity may also influence the direction of wave propagation. If Crithidia experience a sudden increase in viscosity, there is a marked increase in the proportion of the population that is seen to exhibit wave propagation from base to tip; this proportion gradually decreases with time until the whole sample has reverted to “normal” beating. In a single organism, the resumption of normal beating is not accomplished in a single transition but by a series of switches between the forward and reverse modes. The interval of time between successive switches appears to be random, while the length of time spent in base‐to‐tip wave propagation gradually decreases. Despite the randomness of the switching process, its rate when averaged over successive time intervals is found to be constant at a particular viscosity and also dependent on it. The precise manner by which this organism is able to control its direction of wave propagation is unclear. However, the switching behavior it exhibits during the period of adaptation to an increased mechanical loading of the flagellum may reflect a process that characterizes a facet of this controlling mechanism.
Microtubule‐dependent reticulopodial motility: Is there a role for actin?
Authors: Travis Jeffrey L. , Bowser Samuel S. 
Published: February 2005

AbstractWe summarize our recent immunocytochemical characterization of the reticulopodial cytoskeleton of two allogromiid foraminifers and our pharmacologic dissection of its motility. The reticulopodial microtubule cytoskeleton stained with an antiserum to brain microtubule‐associated protein 2. Polymeric actin was localized in the reticulopodia by rhodamine‐phalloidin staining. Microtubule inhibitors reversibly inhibited all aspects of motility; cytochalasins induced altered morphology and disorganization of motility but did not inhibit pseudopodial movements or intracellular transport. Simultaneous application of KCN and salicylhydroxamic acid (an alternative oxidase inhibitor) rapidly blocked all movement, indicating that motility is dependent on metabolic energy and that an alternative oxidative pathway functions in allogromiids. Micromanipulation and laser microsurgical experiments revealed tension throughout the reticulopodium. Our results suggest that microtubules are active components of the reticulopodial motile machinery. Actin may mediate substrate adhesion, whole‐cell locomotion, pseudopodial tension, and coordination of the microtubule‐based motility.
In vitro movements of actin and myosin filaments from muscle
Authors: Higashi‐Fujime Sugie 
Published: February 2005

AbstractUnidirectional sliding of myosin filaments along F‐actin bundles was produced with purified muscle actin and myosin in the presence of ATP. The velocity of myosin filament sliding was independent of myosin filament length. This result supports a recent hypothesis that long distance movement of myosin cross‐bridge can be induced by splitting of one ATP molecule [Yanagida, Arata, and Oosawa, 1985. Nature. 316:366–369; Higashi‐Fujime. 1985. J. Cell Biol., 101:2335–2344].