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  • 2000-2004
  • 1990-1994  (2,276)
  • 1920-1924
  • 1993  (2,276)
  • Life and Medical Sciences  (2,230)
  • ddc:000
  • 1
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    Facets for the Multiple Knapsack Problem. (1993)
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    Publication Date: 2014-02-26
    Description: In this paper we consider the multiple knapsack problem which is defined as follows: given a set $N$ of items with weights $f_i$, $i \in N$, a set $M$ of knapsacks with capacities $F_k$, $k \in M$, and a profit function $c_{ik}, i \in N, k \in M$; find an assignment of a subset of the set of items to the set of knapsacks that yields maximum profit (or minimum cost). With every instance of this problem we associate a polyhedron whose vertices are in one to one correspondence to the feasible solutions of the instance. This polytope is the subject of our investigations. In particular, we present several new classes of inequalities and work out necessary and sufficient conditions under which the corresponding inequality defines a facet. Some of these conditions involve only properties of certain knapsack constraints, and hence, apply to the generalized assignment polytope as well. The results presented here serve as the theoretical basis for solving practical problems. The algorithmic side of our study, i.e., separation algorithms, implementation details and computational experience with a branch and cut algorithm are discussed in the companion paper SC 93-07.
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  • 2
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    A Study of Lanczos-Type Iterations for Symmetric Indefinite Linear Systems (1993)
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    Publication Date: 2014-02-26
    Description: The Lanczos iteration for symmetric indefinite linear systems seems to be well--known for quite a while. However, in order to modify it with the aim of improved performance, the present paper studies certain aspects in terms of an adjoint scalar three--term recurrence. Thus, at least a different view is opened. Moreover, an alternative $3n$--implementation in terms of the Euclidean orthogonal basis has been found that easily permits generalizations. The study is understood as a start--off for further numerical investigations and experiments.
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  • 3
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    Adaptive Multilevel-Methods for Obstacle Problems in Three Space Dimensions. (1993)
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    Publication Date: 2020-10-02
    Description: We consider the discretization of obstacle problems for second order elliptic differential operators in three space dimensions by piecewise linear finite elements. Linearizing the discrete problems by suitable active set strategies, the resulting linear sub--problems are solved iteratively by preconditioned cg--iterations. We propose a variant of the BPX preconditioner and prove an $O(j)$ estimate for the resulting condition number. To allow for local mesh refinement we derive semi--local and local a posteriori error estimates. The theoretical results are illustrated by numerical computations.
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  • 4
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    Coxeter-associahedra. (1993)
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    Publication Date: 2014-02-26
    Description: \def\KPA{\hbox{\rm KPA}}\def\A{{\rm A}}\def\KPW{\hbox{\rm KPW}}\def\W{{\rm W}}\def\B{{\rm B}} \def\D{{\rm D}} Recently M.~M.~Kapranov [Kap] defined a poset $\KPA_{n-1}$, called the {\it permuto-associahedron}, which is a hybrid between the face poset of the permutahedron and the associahedron. Its faces correspond to the partially parenthesized, ordered, partitions of the set $\{1,2,\ldots,n\}$, with a natural partial order. Kapranov showed that $\KPA_{n-1}$ is the face poset of a CW-ball, and explored its connection with a category-theoretic result of MacLane, Drinfeld's work on the Knizhnik-Zamolodchikov equations, and a certain moduli space of curves. He also asked the question of whether this CW-ball can be realized as a convex polytope. We show that this permuto-associahedron corresponds to the type $\A_{n-1}$ in a family of convex polytopes $\KPW$ associated to each of the classical Coxeter groups, $\W = \A_{n-1}, \B_n, \D_n$. The embedding of these polytopes relies on the secondary polytope construction of the associahedron due to Gel'fand, Kapranov, and Zelevinsky. Our proofs yield integral coordinates, with all vertices on a sphere, and include a complete description of the facet-defining inequalities. Also we show that for each $\W$, the dual polytope $\KPW^*$ is a refinement (as a CW-complex) of the Coxeter complex associated to $\W$, and a coarsening of the barycentric subdivision of the Coxeter complex. In the case $\W=\A_{n-1}$, this gives an elementary proof of Kapranov's original sphericity result.
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  • 5
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    Some Integer Programs Arising in the Design of Main Frame Computers. (1993)
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    Publication Date: 2020-11-13
    Description: In this paper we describe and discuss a problem that arises in the (global) design of a main frame computer. The task is to assign certain functional units to a given number of so called multi chip modules or printed circuit boards taking into account many technical constraints and minimizing a complex objective function. We describe the real world problem. A thorough mathematical modelling of all aspects of this problem results in a rather complicated integer program that seems to be hopelessly difficult -- at least for the present state of integer programming technology. We introduce several relaxations of the general model, which are also $NP$-hard, but seem to be more easily accessible. The mathematical relations between the relaxations and the exact formulation of the problem are discussed as well.
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  • 6
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    Cascadic Conjugate Gradient Methods for Elliptic Partial Differential Equations I. Algorithm and Numerical Results. (1993)
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    Publication Date: 2014-02-26
    Description: Cascadic conjugate gradient methods for the numerical solution of elliptic partial differential equations consists of Galerkin finite element methods as outer iteration and (possibly preconditioned) conjugate gradient methods as inner iteration. Both iterations are known to minimize the energy norm of the arising iterations errors. A simple but efficient strategy to control the discretization errors versus the PCG iteration errors in terms of energy error norms is derived and worked out in algorithmic detail. In a unified setting, the relative merits of different preconditioners versus the case of no preconditioning is compared. Surprisingly, it appears that the cascadic conjugate gradient method without any preconditioning is not only simplest but also fastest. The numerical results seem to indicate that the cascade principle in itself already realizes some kind of preconditioning. A theoretical explanation of these observations will be given in Part II of this paper.
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  • 7
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    Interpolation Spaces and Optimal Multilevel Preconditioners. (1993)
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    Publication Date: 2014-02-26
    Description: This paper throws light on the connection between the optimal condition number estimate for the BPX method and constructive approximation theory. We provide a machinery, which allows to understand the optimality as a consequence of an approximation property and an inverse inequality in $H^{1+\epsilon}$, $\epsilon 〉 0$. This machinery constructs so-called {\em approximation spaces}, which characterize a certain rate of approximation by finite elements and relates them with interpolation spaces, which characterize a certain smoothness.
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  • 8
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    Telebus-Disposition: Ein Konzept zur Serviceverbesserung bei gleichzeitiger Kostensenkung.[nur hausintern] (1993)
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    Publication Date: 2020-08-05
    Description: "`Telebus"' ist der soziale Behindertenfahrdienst im Land Berlin. Das Telebus-Forschungsprojekt des Konrad-Zuse-Zentrums für Informationstechnik (ZIB) hat das Ziel, den Fahrdienst (insbesondere die Disposition der Telebusse) zu verbessern, d.h. kundenfreundlicher zu gestalten und gleichzeitig billiger zu machen. In diesem Bericht werden die bisherigen Ergebnisse dargestellt und weitere Möglichkeiten zur Verbesserung des Service und zur Reduzierung der Kosten skizziert. \originalTeX
    Keywords: ddc:000
    Language: German
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  • 9
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    Lectures on Polytopes. (1993)
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    Publication Date: 2014-02-26
    Description: These lecture notes have several aims: \begin{itemize} \item to give an introduction to some basic facts about convex polytopes, with an emphasis on the basic methods that yield them (Fourier-Motzkin elimination, Schlegel diagrams, shellability, Gale transforms and oriented matroids), \item to discuss some important examples and elegant constructions (cyclic and neighborly polytopes, zonotopes, Minkowski sums, permutahedra and associahedra, fiber polytopes, the Lawrence construction) \item and to illustrate why polytope theory is exciting, with highlights like Kalai's new diameter bounds, the construction of non-rational polytopes, the Bohne-Dress tiling theorem, shellability and the upper bound theorem, .... \end{itemize} For several of these topics the decisive break-through is very recent, which suggests that there is much more discovered.
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  • 10
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    GRAZIL - Beschreibung der Version 6.0 des Plotpaketes. (1993)
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    Publication Date: 2020-03-11
    Description: GRAZIL ist ein interaktives Programmpaket zur grafischen Darstellung von zwei-dimensionalen Kurvenverläufen. Dem Benutzer stehen zahlreiche Kommandos und ein grafisches User-Interface zum Gestalten des Layouts der Zeichnung zur Verfügung. Die Eingabedaten müssen dem GRAZIL-Eingabe-Format genügen. Somit wird eine hohe Flexibilität und eine gro\"se Bandbreite der Einsatzmöglichkeiten erreicht. GRAZIL wurde mit der grafischen Grundsoftware GKS entwickelt. Dadurch kann ein breites Rechner- und Ausgabegerätespektrum genutzt werden.
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    Language: German
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  • 11
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    Kaskade Manual - Version 2.0. (1993)
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    Publication Date: 2019-05-10
    Description: The KASKADE toolbox defines an interface to a set of C subroutines which can be used to implement adaptive multilevel Finite Element Methods solving systems of elliptic equations in two and three space dimensions. The manual contains the description of the data structures and subroutines. The main modules of the toolbox are a runtime environment, triangulation and node handling, assembling, direct and iterative solvers for the linear systems, error estimators, refinement strategies, and graphic utilities. Additionally, we included appendices on the basic command language interface, on file formats, and on the definition of the partial differential equations which can be solved. The software is available on the ZIB ftp--server {\tt elib} in the directory {\tt pub/kaskade}. TR 93--5 supersedes TR 89--4 and TR 89--05.
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  • 12
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    Volume Rendering - Mathematicals Models and Algorithmic Aspects. (1993)
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    Publication Date: 2020-10-02
    Description: In this paper various algorithms for rendering gaseous phenomena are reviewed. In computer graphics such algorithms are used to model natural scenes containing clouds, fog, flames and so on. On the other hand it has become an important technique in scientific visualization to display three dimensional scalar datasets as cloudy objects. Our emphasis is on this latter subject of so-called {\em direct volume rendering}. All algorithms will be discussed within the framework of linear transport theory. The equation of transfer is derived. This equation is suitable to describe the radiation field in a participating medium where absorption, emission, and scattering of light can occur. Almost all volume rendering algorithms can be shown to solve special cases of the equation of transfer. Related problems like the mapping from data values to model parameters or possible parallelization strategies will be discussed as well.
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  • 13
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    An Implementation of Extrapolation Codes in C++. (1993)
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    Publication Date: 2014-02-26
    Description: This report describes the new object oriented implementation of extrapolation codes {\sc Eulex, Eulsim, Difex} for ordinary differential equations. The resulting C++ class library provides a simple and flexible interface to these methods and incorporates advanced features like continuous output and order-stepsize freezing. The interface of the ODE classes allows in particular a user-defined solver for the linear systems occuring in the linearly implicit discretization scheme. The library also provides some classes for numerical objects such as vectors and (full) matrices. Due to the underlying data-view concept it is possible to access substructures without copying. In addition, we included several utility classes such as a timer and a minimal command language that may be useful in other contexts, too.
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  • 14
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    Materialien zur Euler-Vorlesung in Sanssouci. (1993)
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    Publication Date: 2014-02-26
    Description: Aus dem Inhalt: Vorwort; Leonhard Euler - aus der Zeit seines Wirkens in Berlin; Introductory Remarks.
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    Language: German
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  • 15
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    Cellular Structured Space (Rechnender Raum) and Physical Phenomena. (1993)
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    Publication Date: 2014-02-26
    Description: The problem of nonlocal correlation and symmetry in space is of great importance in physical phenomena like the \underline{Einstein-Poloski-Rosen-Paradox} and others. It is shown that in Cellular Automata (Rechnender Raum) the structure of the space offers solutions for such problems.
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  • 16
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    KARDOS - KAskade Reaction Diffusion One-dimensional System. (1993)
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    Publication Date: 2014-02-26
    Description: A software package for the adaptive solution of time--dependent reaction--diffusion systems and linear elliptic systems in one space dimension is presented. The used algorithm is based on fundamental arguments in J.~Lang, A.~Walter: {\it A Finite Element Method Adaptive in Space and Time for Nonlinear Reaction--Diffusion Systems.} IMPACT of Computing in Science and Engineering, 4, p.~269--314 (1992). Here, only brief outlines of the algorithm are given. This software package is based on the KASKADE toolbox B.~Erdmann, J.~Lang, R.~Roitzsch: {\it KASKADE -- Manual.} To appear as Technical Report TR 93--5, Konrad--Zuse--Zentrum (ZIB) (1993).
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  • 17
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    Inexact Gauss Newton Methods for Parameter Dependent Nonlinear Problems. (1993)
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    Publication Date: 2014-02-27
    Description: A new approach to inexact Gauss Newton methods for the solution of underdetermined nonlinear problems is presented. It is based on a convergence theorem being invariant under affine transformations of the domain and results in an easily implementable accuracy matching strategy for the arising linear subproblems which guarantees the quadratic convergence. Thanks to the weak assumptions on the given nonlinear problem, the results provide a general framework for multilevel Newton and continuation methods. As an example, a new multilevel Newton h-p collocation method for boundary value problems of ordinary differential equations is developed. It combines the inexact Newton method with a linear collocation solver using adaptive refinement and variable orders. The performance of the resulting C++ class library {\sc Cocon} is demonstrated by some numerical examples including singular perturbed problems. In addition, the new method is applied to a realistic railway bogie model in which a branch of periodic solutions emanates from a branch of fixed points at a Hopf bifurcation.
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    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 18
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    Adaptive Linienmethoden für nichtlineare parabolische Systeme in einer Raumdimension. (1993)
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    Publication Date: 2014-02-27
    Description: A new method for the numerical solution of highly nonlinear, coupled systems of parabolic differential equations in one space dimension is presented. The approach is based on a classical method of lines treatment. Time discretization is done by means of the semi--implicit Euler discretization. Space discretization is done with finite differences on non--uniform grids. Both basic discretizations are coupled with extrapolation techniques. With respect to time the extrapolation is of variable order whereas just one extrapolation step is done in space. Based on local error estimates for both, the time and the space discretization error, the accuracy of the numerical approximation is controlled and the discretization stepsizes are adapted automatically and simultaneously. Besides the local adaptation of the space grids after each integration step (static regridding), the grid may even move within each integration step (dynamic regridding). Thus, the whole algorithm has a high degree of adaptivity. Due to this fact, challenging problems from applications can be solved in an efficient and robust way.
    Keywords: ddc:000
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 19
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    Mechanical Theorem Proving in Projective Geometry. (1993)
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    Publication Date: 2014-02-26
    Description: We present an algorithm that is able to confirm projective incidence statements by carrying out calculations in the ring of all formal determinants (brackets) of a configuration. We will describe an implementation of this power and present a series of examples treated by the prover, including {\it Pappos' and Desargues' Theorems,} the {\it Sixteen Point Theorem, Saam's Theorem, }the {\it Bundle Condition,} the uniqueness of a harmonic Point and {\it Pascal's Theorem.}
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  • 20
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    Polyhedral and Computational Investigations for Designing Communication Networks with High Survivability Requirements. (1993)
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    Publication Date: 2020-12-14
    Description: We consider the important practical and theoretical problem of designing a low-cost communications network which can survive failures of certain network components. Our initial interest in this area was motivated by the need to design certain ``two-connected" survivable topologies for fiber optic communication networks of interest to the regional telephone companies. In this paper, we describe some polyhedral results for network design problems with higher connectivity requirements. We also report on some preliminary computational results for a cutting plane algorithm for various real-world and random problems with high connectivity requirements which shows promise for providing good solutions to these difficult problems. \def\NP{$\cal NP$}
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  • 21
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    On a Two-Dimensional Multilevel Adaptive Finite Element Method for the Time-Independent Schrödinger-Equation. (1993)
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    Publication Date: 2014-02-26
    Description: The subject of this study is a multilevel Finite Element Method based on an error estimator and step by step grid refinement as an universal tool for solving time--independent Schrödinger--eigenvalue problems. Numerical results for standard problems appearing in vibrational motion and molecular electronic structure calculations are given and discussed.
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  • 22
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    Secondary Hopf Bifurcation Caused by Steady-State Steady-State Mode Interaction. (1993)
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    Publication Date: 2014-02-26
    Description: In two-parameter systems with symmetry two steady state bifurcation points of different symmetry types coalesce generically within one point. Under certain group theoretic conditions involving the action of the symmetry group on the kernels, we show that secondary Hopf bifurcation is borne by the mode interaction. We explain this phenomenon by using linear representation theory. For motivation an example with $D_3$-symmetry is investigated where the main properties causing the Hopf bifurcation are summarized.
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  • 23
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    Symmetric Hierarchical Polynomials for the h-p-Version of Finite Elements. (1993)
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    Publication Date: 2021-03-19
    Description: Adaptive numerical methods using the $h$-$p$-version of finite elements require special kinds of shape functions. Desirable properties of them are symmetry, hierarchy and simple coupling. In a first step it is demonstrated that for standard polynomial vector spaces not all of these features can be obtained simultaneously. However, this is possible if these spaces are extended. Thus a new class of polynomial shape functions is derived, which is well-suited for the $p$- and $h$-$p$-version of finite elements on unstructured simplices. The construction is completed by minimizing the condition numbers of the arising finite element matrices. The new shape functions are compared with standard functions widely used in the literature.
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  • 24
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    A Posteriori Error Estimates for Elliptic Problems. (1993)
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    Publication Date: 2019-05-10
    Description: {\def\enorm {\mathop{\mbox{\boldmath{$|\!|$}}}\nolimits} Let $u \in H$ be the exact solution of a given self--adjoint elliptic boundary value problem, which is approximated by some $\tilde{u} \in {\cal S}$, $\cal S$ being a suitable finite element space. Efficient and reliable a posteriori estimates of the error $\enorm u - \tilde{u}\enorm $, measuring the (local) quality of $\tilde{u}$, play a crucial role in termination criteria and in the adaptive refinement of the underlying mesh. A well--known class of error estimates can be derived systematically by localizing the discretized defect problem using domain decomposition techniques. In the present paper, we provide a guideline for the theoretical analysis of such error estimates. We further clarify the relation to other concepts. Our analysis leads to new error estimates, which are specially suited to three space dimensions. The theoretical results are illustrated by numerical computations.}
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  • 25
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    Algebraic Solution of Nonlinear Equation Systems in REDUCE. (1993)
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    Publication Date: 2014-02-26
    Description: The strategy for solving nonlinear equation systems automatically in the computer algebra system REDUCE is described. Kernel of the solver is a factoring Buchberger algorithm. Pre -- and postprocessors enable the use of the Gröbner techniques in a black box manner. In addition to polynomials equations with surds, trigonometric functions and separable transcendental functions are covered.
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  • 26
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    Wissenschaftliches Publizieren und Elektronische Fachinformation im Umbruch: ein Situationsbericht aus der Sicht der Mathematik. (1993)
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    Publication Date: 2014-02-26
    Description: In diesem Aufsatz geben wir einen Bericht über den Stand der elektronischen Fachinformation in der Mathematik in Deutschland. Wir sehen diesen Bereich nicht als ein organisatorisch isoliertes Unterfangen, sondern eingebettet in weltweite Bestrebungen und Entwicklungen in der Informationstechnik, im wissenschaftlichen Publikationswesen und natürlich auch in der Mathematik selber. Unser Artikel endet mit einigen weitreichenden (und einigen Lesern möglicherweise spektakulär erscheinenden) Vorschlägen, die sowohl die Informationsanbieter (wie die Fachinformationszentren und Verlage), die öffentlichen Geldgeber als auch die mathematischen Organisationen (wie z.~B.~ die DMV und die mathematischen Fachbereiche) betreffen. Um den gegenwärtigen Zustand der elektronischen Fachinformation und unsere Gedanken zu diesem Thema adäquat beschreiben zu können, präsentieren wir eine breit angelegte Situationsanalyse. Wir stellen den gegenwärtigen Stand der technologischen Entwicklung im elektronischen Publizieren dar und skizzieren seine Auswirkungen. Wir beschreiben das Feld der Interessen und Kräfte im Bereich des mathematischen Publizierens. Wir geben einen kurzen historischen Abriss der Geschichte der Klassifikation und des Referatewesens und zeigen, wie dieses in die elektronische Fachinformation auf dem Gebiet der Mathematik mündete und dann zum DMV-Projekt Fachinformation führte, das der Anlass zur Abfassung dieses Artikels war. Wir skizzieren die gegenwärtige Rezeption elektronischer Fachinformation in der Mathematik in Deutschland. Ausgehend von einer Darstellung und Bewertung verschiedener Modelle des Referatewesens zeigen wir unter Einbeziehung der vorhandenen technischen Gegebenheiten (elektronische Netze etc.) verschiedene Möglichkeiten zur Liberalisierung und Rationalisierung des weltweiten mathematischen Informationswesens auf. Wir sehen den Austausch von Information in engem Zusammenhang mit dem Austausch von Software im Wissenschaftsbereich und regen auch in diesem Bereich an, internationale Kooperation und Offenheit anzustreben. \originalTeX
    Keywords: ddc:000
    Language: German
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  • 27
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    A Cutting Plane Based Algorithm for the Multiple Knapsack Problem. (1993)
    Details
    Publication Date: 2014-02-26
    Description: In this paper we describe a cutting plane based algorithm for the multiple knapsack problem. We use our algorithm to solve some practical problem instances arising in the layout of electronic circuits and in the design of main frame computers, and we report on our computational experience. This includes a discussion and evaluation of separation algorithms, an LP-based primal heuristic and some implementation details. The paper is based on the polyhedral theory for the multiple knapsack polytope developed in our companion paper SC 93-04 and meant to turn this theory into an algorithmic tool for the solution of practical problems.
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    Language: English
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    Design of Survivable Networks (1993)
    Details
    Publication Date: 2020-12-14
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 29
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    A quasiresonant smoothing algorithm for the fast analysis of selective vibrational excitation. (1993)
    Details
    Publication Date: 2014-02-26
    Description: One key problem in modern chemistry is the simulation of the dynamical reaction of a molecule subjected to external radiation. This is described by the Schrödinger equation, which, after eigenfunction expansion, can be written in form of a system of ordinary differential equations, whose solutions show a highly oscillatory behaviour. The oscillations with high frequencies and small amplitudes confine the stepsizes of any numerical integrator -- an effect, which, in turn, blows up the simulation time. Larger stepsizes can be expected by averaging these fast oscillations, thus smoothing the trajectories. This idea leads to the construction of a quasiresonant smoothing algorithm (QRS). In QRS, a natural and computationally available splitting parameter $\delta$ controls the smoothing properties. The performance of QRS is demonstrated in two applications treating the selective excitation of vibrational states by picosecond laser pulses. In comparison with standard methods a speedup factor of 60--100 is observed. A closer look to purely physically motivated quasiresonant approximations such as WFQRA shows some additional advantages of the above smoothing idea. Among these the possibility of an adaptive formulation of QRS via the parameter $\delta$ is of particular importance.
    Keywords: ddc:000
    Language: English
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  • 30
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    Combinatorial Optimization. (1993)
    Details
    Publication Date: 2020-11-16
    Description: This paper will appear as Chapter 28 of the forthcoming "Handbook on Combinatorics" (editors: R. Graham, M. Grötschel, L. Lovasz) to be published in 1994, by North-Holland.
    Keywords: ddc:000
    Language: English
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  • 31
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    Numerical Simulation of Relaxation Oscillations of Waveguide-Lasers. (1993)
    Details
    Publication Date: 2014-02-26
    Description: An analysis of relaxation oscillations in local Er-doped optically pumped lasers is reported. It is based on a time dependent rate equation model for a quasi-two-level-system with wavelength dependent emission- and absorption cross-sections. For the first time a numerically reliable simulation of the characteristic laser behaviour was possible: the onset and decay of the oscillations, the time-dependent repetition period and the steady state signal output power. The characteristic waveguide parameters, as the erbium-concentration profile, the polarization dependent pump- and signal mode intensity profiles, the scattering losses, the cavity length and the front and rear reflectivities were all taken into account. The basic formulas are general and can also be used for Er-doped fiber lasers. Mathematically the problem can be characterized as a large boundary value problem, which can approximately be replaced by a stiff initial value problem of ordinary differential equations. The used algorithmic replacement procedure is motivated and discussed in detail. Here, pump- and signal evolution versus time are presented for an planar Er-diffused $\rm Ti$:$\rm LiNbO_{3}$ waveguide laser. The numerically obtained results show a nearly quantitative agreement with experimental investigations. Simultanously they supply knowledge about non-measureable (space-dependent population dynamic of the Er-atoms) and till today not measured data (dynamical response of the laser by a sharp peak in the external pump).
    Keywords: ddc:000
    Language: English
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  • 32
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    Algebraic Algorithms for Sampling from Conditional Distributions. (1993)
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    Publication Date: 2014-02-26
    Description: We construct Markov chain algorithms for sampling from discrete exponential families conditional on a sufficient statistic. Examples include generating tables with fixed row and column sums and higher dimensional analogs. The algorithms involve finding bases for associated polynomial ideals and so an excursion into computational algebraic geometry.
    Keywords: ddc:000
    Language: English
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  • 33
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    Monotone Multigrid Methods for Elliptic Variational Inequalities I. (1993)
    Details
    Publication Date: 2014-02-26
    Description: Extending well--known linear concepts of successive subspace correction, we arrive at extended relaxation methods for elliptic variational inequalities. Extended underrelaxations are called monotone multigrid methods, if they are quasioptimal in a certain sense. By construction, all monotone multigrid methods are globally convergent. We take a closer look at two natural variants, which are called symmetric and unsymmetric multigrid methods, respectively. While the asymptotic convergence rates of the symmetric method suffer from insufficient coarse--grid transport, it turns out in our numerical experiments that reasonable application of the unsymmetric multigrid method may lead to the same efficiency as in the linear, unconstrained case.
    Keywords: ddc:000
    Language: English
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  • 34
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    Multilevel Methods for Elliptic Problems on Domains not Resolved by the Coarse Grid. (1993)
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    Publication Date: 2014-02-26
    Description: Elliptic boundary value problems are frequently posed on complicated domains which cannot be covered by a simple coarse initial grid as it is needed for multigrid like iterative methods. In the present article, this problem is resolved for selfadjoint second order problems and Dirichlet boundary conditions. The idea is to construct appropriate subspace decompositions of the corresponding finite element spaces by way of an embedding of the domain under consideration into a simpler domain like a square or a cube. Then the general theory of subspace correction methods can be applied.
    Keywords: ddc:000
    Language: English
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  • 35
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    Zonotopal Tilings and the Bohne-Dress Theorem. (1993)
    Details
    Publication Date: 2014-02-26
    Description: We prove a natural bijection between the polytopal tilings of a zonotope $Z$ by zonotopes, and the one-element-liftings of the oriented matroid ${\cal M}(Z)$ associated with $Z$. This yields a simple proof and a strengthening of the Bohne-Dress Theorem on zonotopal tilings.
    Keywords: ddc:000
    Language: English
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  • 36
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    A package on formal power series. (1993)
    Details
    Publication Date: 2015-06-01
    Description: Formal Laurent-Puiseux series of the form \[ f(x)=\sum \limits_{k=k_0}^{\infty}a_{k}x^{k/n} \] are important in many branches of mathematics. Whereas {\sc Mathematica} supports the calculation of truncated series with its {\tt Series} command, and the {\sc Mathematica} package {\tt SymbolicSum} that is shipped with {\sc Mathematica} version 2 is able to convert formal series of the type mentioned above in some instances to their corresponding generating functions, in six publications of the author we developed an algorithmic procedure to do these conversions that is implemented by the author, A.\ Rennoch and G.\ Stölting in the {\sc Mathematica} package {\tt PowerSeries}. The implementation enables the user to reproduce most of the results of the extensive bibliography on series of Hansen, E.\ R.: A table of series and products. Prentice-Hall, 1975. Moreover a subalgorithm of its own significance generates differential equations satisfied by the input function.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 37
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    Formal Power Series. (1993)
    Details
    Publication Date: 2015-06-01
    Description: {\newcommand{\C}{{\rm {\mbox{C{\llap{{\vrule height1.52ex}\kern.4em}}}}}} \newcommand{\Z} {{\rm {\mbox{\protect\makebox[.2em][l]{\sf Z}\sf Z}}}} \newcommand{\Maple}{{\sc Maple}} Formal Laurent-Puiseux series of the form \[ f(x)=\sum\limits_{k=k_0}^{\infty}a_{k}x^{k/n} \label{eq:formalLPS} \] with coefficients $a_{k}\in\C\;(k\in\Z)$ are important in many branches of mathematics. \Maple\ supports the computation of {\em truncated\/} series with its {\tt series} command, and through the {\tt powerseries} package infinite series are available. In the latter case, the series is represented as a table of coefficients that have already been determined together with a function for computing additional coefficients. This is known as {\em lazy evaluation\/}. But these tools fail, if one is interested in an explicit formula for the coefficients $a_k$. In this article we will describe the \Maple\ implementation of an algorithm presented in several papers of the second author which computes an {\em exact\/} formal power series of a given function. This procedure will enable the user to reproduce most of the results of the extensive bibliography on series. We will give an overview of the algorithm and then present some parts of it in more detail. This package is available through the \Maple-share library with the name {\tt FPS}. We flavor this procedure with the following example. %\begin{maple} \begin{verbatim}〉 FormalPowerSeries(sin(x), x=0);\end{verbatim} \begin{samepage} \begin{verbatim} infinity ----- k (2 k + 1) \ (-1) x ) ---------------- / (2 k + 1)! ----- k = 0 \end{verbatim} \end{samepage} }
    Keywords: ddc:000
    Language: English
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  • 38
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    Packing Paths and Steiner Trees: Routing of Electronic Circuits. (1993)
    Details
    Publication Date: 2014-02-26
    Description: One of the challenging problems in the design of electronic circuits is the so-called routing problem. Roughly speaking, the task is to connect so-called terminal sets via wires on a predefined area. In addition, certain design rules are to be taken into account and an objective function such as the wiring length must be minimized. The routing problem in general is too complex to be solved in one step. Depending on the user's choice of decomposing the chip design problem into a hierarchy of stages, on the underlying technology, and on the given design rules, various subproblems arise. We discuss several variants of practically relevant routing problems and give a short overview on the underlying technologies and design rules. Many of the routing problems that come up this way can be formulated as the problem of packing so-called Steiner trees in certain graphs. We consider the Steiner tree packing problem from a polyhedral point of view and present three possibilities to define an appropriate polyhedron. Weighing their pros and cons we decide for one of these polytopes and sketch some of our investigations.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 39
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    Monotone Multigrid Methods for Elliptic Variational Inequalities II. (1993)
    Details
    Publication Date: 2014-02-26
    Description: We derive fast solvers for discrete elliptic variational inequalities of the second kind as resulting from the approximation by piecewise linear finite elements. Following the first part of this paper, monotone multigrid methods are considered as extended underrelaxations. Again, the coarse grid corrections are localized by suitable constraints, which in this case are fixed by fine grid smoothing. We consider the standard monotone multigrid method induced by the multilevel nodal basis and a truncated version. Global convergence results and asymptotic estimates for the convergence rates are given. The numerical results indicate a significant improvement in efficiency compared with previous multigrid approaches.
    Keywords: ddc:000
    Language: English
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  • 40
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    A Polyhedral Approach to Multicommodity Survivable Network Design. (1993)
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    Publication Date: 2014-02-26
    Description: The design of cost-efficient networks satisfying certain survivability constraints is of major concern to the telecommunications industry. In this paper we study a problem of extending the capacity of a network by discrete steps as cheaply as possible, such that the given traffic demand can be accommodated even when a single edge or node in the network fails. We derive valid and non-redundant inequalities for the polyhedron of capacity design variables, by exploiting its relationship to connectivity network design and knapsack-like subproblems. Computational work using this model and the additional inequalities is in progress.
    Keywords: ddc:000
    Language: English
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  • 41
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    Adaptive Discrete Galerkin-Methods for Macromolecular Processes. (1993)
    Details
    Publication Date: 2014-02-26
    Description: In this paper, a rather recent algorithmic approac to the numerical simulation of macromolecula processes is surveyed. It avoids the numerical stiff integration o thousands up to millions of ODE's by constructing a scale of discret Hilbert spaces, especially weighted sequence spaces, and establishing corresponding Galerkin method. Examples including polyreactions o industrial relevance and ecological waste management by biochemica recycling illustrate the importance and efficiency of the algorithm.
    Keywords: ddc:000
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  • 42
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    Optimum Path Packing on Wheels: The Noncrossing Case. (1993)
    Details
    Publication Date: 2014-02-26
    Description: We show that, given a wheel with nonnegative edge lengths and pairs of terminals located on the wheel's outer cycle such that no two terminal pairs cross, then a path packing, i.~e.,a collection of edge disjoint paths connecting the given terminal pairs, of minimum length can be found in strongly polynomial time. Moreover, we exhibit for this case a system of linear inequalities that provides a complete and nonredundant description of the path packing polytope, which is the convex hull of all incidence vectors of path packings and their supersets.
    Keywords: ddc:000
    Language: English
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  • 43
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    Jahresbericht 1993 (1993)
    Details
    Publication Date: 2019-10-24
    Keywords: ddc:000
    Language: German
    Type: annualzib , doc-type:report
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  • 44
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    Jahresbericht 1992 (1993)
    Details
    Publication Date: 2019-10-24
    Keywords: ddc:000
    Language: German
    Type: annualzib , doc-type:report
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  • 45
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    Discrete Transparent Boundary Conditions for the Numerical Solution of Fresnel's Equation. (1993)
    Details
    Publication Date: 2022-07-07
    Description: The paper presents a construction scheme of deriving transparent , i. e. reflection-free, boundary conditions for the numerical solution of Fresnel's equation (being formally equivalent to Schrödinger's equation). These boundary conditions appear to be of a nonlocal Cauchy type. As it turns out, each kind of linear implicit discretization induces its own discrete transparent boundary conditions.
    Keywords: ddc:000
    Language: English
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  • 46
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    On the Impact of Communication Latencies on Distributed Sparse LU Factorization. (1993)
    Details
    Publication Date: 2022-07-19
    Description: Sparse LU factorization offers some potential for parallelism, but at a level of very fine granularity. However, most current distributed memory MIMD architectures have too high communication latencies for exploiting all parallelism available. To cope with this, latencies must be avoided by coarsening the granularity and by message fusion. However, both techniques limit the concurrency, thereby reducing the scalability. In this paper, an implementation of a parallel LU decomposition algorithm for linear programming bases is presented for distributed memory parallel computers with noticable communication latencies. Several design decisions due to latencies, including data distribution and load balancing techniques, are discussed. An approximate performance model is set up for the algorithm, which allows to quantify the impact of latencies on its performance. Finally, experimental results for an Intel iPSC/860 parallel computer are reported and discussed.
    Keywords: ddc:000
    Language: English
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  • 47
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cm.970260101
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  • 48
    Electronic Resource
    Electronic Resource
    Site-directed antibodies to tubulin (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 1-6 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970260102
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  • 49
    Electronic Resource
    Electronic Resource
    Protein kinases are required for embryonic neural crest cell galvanotaxis (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 54-66 
    Details
    ISSN: 0886-1544
    Keywords: protein kinase ; galvanotaxis ; motility ; phorbol ester ; neural crest ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Embryonic quail neural crest cells migrate towards the negative pole of an imposed dc electric field as small as 7 mV/mm (0.4 mV per average cell length). The involvement of protein kinases in the mechanism utilized by these cells to detect and respond to such imposed fields was tested through the use of several kinase inhibitors. Evidence for the involvement of protein kinase C (PKC) included: (1) inhibition of the directed motility by 1 μM sphingosine that was reversed by the addition of the phorbol ester, PMA; (2) stimulation of a faster response to the imposed field by PMA; and (3) inhibition of the directed translocation by 5 μM H-7. However, another PKC inhibitor, staurosporin, did not inhibit the directed translocation (1 nM-1 μM). We also found evidence for the involvement of either cAMP- or cGMP-dependent protein kinase. The galvanotactic response was partially inhibited by the addition of 10 μM H-9 and the response was enhanced in the presence of the phosphodiesterase inhibitor, IBMX. However, the adenylate cyclase stimulant, forskolin, had no significant influence on the directed motility, although it reduced the average cell velocity. While these experiments suggest that cAMP- or cGMP-dependent protein kinase or PKC may be involved in the galvanotaxis response, two other protein kinases appeared not to be required. The myosin light chain kinase inhibitor, ML-7, had no effect on the directed motility in an imposed field, so myosin light chain kinase may not be required for galvanotaxis. Similarly, 5 μM W-7 had no significant effect on the directed translocation, suggesting that calmodulin-dependent protein kinase is not involved.Interestingly, the continuous activity of a protein kinase is apparently not required for the directed translocation response. The addition of the PKC and cAMP-dependent protein kinase inhibitor, H-7, after the cells had been exposed to the field for 1 hour, had no effect on the subsequent directed translocation. Thus, for these inhibitors to block the directed translocation, they must be present at the same time as the initial field application. This implies that an integral step in the cellular response mechanism for galvanotaxis involves the stimulation of a protein kinase whose effect is long lasting. © 1993 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970240107
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  • 50
    Electronic Resource
    Electronic Resource
    Dynamics of organelles in the mitotic spindles of living cells: Membrane and microtubule interactions (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 19-39 
    Details
    ISSN: 0886-1544
    Keywords: endoplasmic reticulum ; carbocyanine dyes ; mitosis ; cell division ; membranous organelles ; confocal microscopy ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution and dynamics of the membranous organelles in two cell types were investigated during cell division. Live cells (either PtK2 or LLC-PK1) labeled with the vital dye 3,3′-dihexyloxacarbocyanine iodide [DiOC6(3)] were observed via serial optical sectioning with the laser-scanning confocal microscope. Z-series of labeled, dividing cells were collected every 1-2 minutes throughout mitosis, beginning at prophase and extending to the spreading of the daughter cells. Membrane distribution began to change from the onset of prophase in both cell types. When the mitotic spindle formed in prometaphase, fine tubular membranes, similar to those extending out to the edges of interphase cells aligned along the kinetochore spindle fibers. The lacy polygonal network typical of interphase cells persisted beneath the spindle, and a membrane network was also associated with the dorsal layer of the cell. As PtK2 cells reached metaphse, their spindles were nearly devoid of membrane staining, whereas the spindles of LLC-PK1 cells contained many tubular and small vesicular membranous structures. X-Z series of the LLC-PK1 metaphase spindle revealed a small cone of membranes that was separated from the rest of the cytoplasm by kinetochore MTs. In both cell types, as chromosome separation proceeded, the interzone remained nearly devoid of membranes until the onset of anaphase B. At this time the elongating interzonal microtubules were closely associated with the polygonal network of endoplasmic reticulum. Cytokinesis caused a compression, and then an exclusion of organelles from the midbody. Immunofluorescence staining with anti-tubulin antibodies suggested that spindle membranes were associated with microtubules throughout mitosis. In addition, taxol induced a dense and extensive collection of small vesicles to collect at the spindle poles of both cell types. Nocodazole treatment induced a distinct loss of organization of the membranous components of the spindles. Together these results suggest that microtubules organize the membrane distribution in mitotic cells, and that this organization may vary in different cell types depending on the quantity of microtubules within the spindle. © 1993 Wiley-Liss, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970260104
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  • 51
    Electronic Resource
    Electronic Resource
    Method of cell handling affects leakiness of cell surface labeling and detection of intracellular keratins (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 77-87 
    Details
    ISSN: 0886-1544
    Keywords: cell surface iodination ; intermediate filaments ; cell surface keratins ; keratins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Keratins are a subgroup of cytoskeletal intermediate filament proteins found in most epithelial cells. Some reports have suggested that keratins may be found on the cell surface as well as their well-accepted cytoskeletal location. A major part of the evidence in the interpretation of cell surface expression of keratins is cell surface radioiodination. Here we show that lactoperoxidase-catalyzed iodination of colonic and breast tissue culture cells results in radiolabeling of the keratins when cells are manipulated. No labeling of keratins is detected when cells are labeled directly on the tissue culture dish. A similar result was obtained when intact cells were biotinylated using water-soluble sulfo-NHS-biotin. Partitioning of the keratins to a soluble and an insoluble pool after “cell surface” 125I-labeling showed that both pools became iodinated. Indirect immunofluorescence showed that binding of a panel of anti-keratin antibodies to intact epithelial cells occurs only on the cells that are more adherent, which are the cells that require longer manipulation to remove from the tissue culture dish. Taken together, our results indicate that the reported expression of cell surface keratins in some cells likely reflects intracellular keratins. In addition, the method of epithelial cell handling can dramatically alter the leakiness of cell surface iodination techniques. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970260108
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  • 52
    Electronic Resource
    Electronic Resource
    Contraction of reconstituted Dictyostelium cytoskeletons: An apparent role for higher order associations among myosin filaments (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 103-114 
    Details
    ISSN: 0886-1544
    Keywords: thick filament structure ; actin meshwork ; stopped flow ; cytoskeletal contraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A large number of cellular functions require assembly of actin and myosin and coordinated interactions between the resulting filaments. To better understand the structure and function of one such contractile assembly, we have begun fractionation and reconstitution studies of Dictyostelium cytoskeletons. Isolated cytoskeletons rapidly contracted when mixed with Mg-ATP, and myosin II was essential for this since myosin-depleted (stripped) cytoskeletons failed to contract. Dictyostelium, Acanthamoeba, or skeletal muscle myosins bound to stripped cytoskeletons with equal efficiency, and the Mg-ATPase of all three myosins was stimulated by the cytoskeleton-associated actin. Near neutral pH, however, only the homologous system reconstituted with Dictyostelium myosin contracted, despite the fact that under the same conditions all three myosins bound to myosin-depleted (ghost) muscle myofibrils and restored contractility. Individual Dictyostelium myosin thick filaments have a strong tendency to aggregate and associate end-to-end, and this may be important for functional contraction of cytoskeletons. This suggestion is supported by the observation that under conditions where individual Acanthamoeba myosin filaments aggregated, reconstituted cytoskeletons contracted. None of the solution conditions tested caused rabbit muscle myosin filaments to aggregate or to contract cytoskeletons. Thus higher order associations among individual myosin filaments may be essential for some types of cell motility. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970260202
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  • 53
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cm.970240301
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    PDGF and neomycin induce similar changes in the actin cytoskeleton in human fibroblasts (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 139-149 
    Details
    ISSN: 0886-1544
    Keywords: growth factor ; phosphatidylinositol cycle ; actin polymerization ; fluorescence microscopy ; cytochalasin D ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The addition of platelet-derived growth factor (PDGF) to serum-starved fibroblasts induces increased motility, formation of lamellipodia, increased ruffling activity, and actin ring structures associated with dorsal ruffles. Involvement of the phosphatidylinositol cycle (PI-cycle) in these morphological changes was investigated by observing the effects of neomycin, an inhibitor of the PI-cycle, on cultured human foreskin fibroblasts. The role of actin in the changes was investigated by using cytochalasin D (CD). Actin in detergent-extracted cells was labelled with TRITC-phalloidin and examined with fluorescence microscopy. Using PDGF and neomycin simultaneously potentiated lamellipodia formation, ruffling activity, as well as the number of cells with actin rings. Furthermore, neomycin by itself induced morphological changes similar to those induced by PDGF. Quantitation of actin rings showed dose and time dependency for PDGF and neomycin respectively, with a maximal number of cells containing rings after 15 min of exposure to either 3.5 mM neomycin or 10 ng PDGF/ml. Comparing the two substances, PDGF induced ring formation in a greater number of cells. These processes were inhibited by the presence of CD. PDGF- and neomycin-induced changes in the actin cytoskeleton were also observed in human embryonic lung fibroblasts, human glial cells, and embryonic mouse fibroblasts, all of which are known to express PDGF-receptors. In conclusion, the present study indicates that an increased turnover of the PI-cycle is not essential for the changes in actin organization induced by PDGF. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240207
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    Divergent neural β tubulin from the antarctic fish notothenia coriiceps neglecta: Potential sequence contributions to cold adaptation of microtubule assembly (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 156-166 
    Details
    ISSN: 0886-1544
    Keywords: tubulin isotypes ; tubulin cDNA sequence ; Antarctic nototheniid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cytoplasmic microtubules of the cold-adapted Antarctic fishes, unlike those of homeotherms and temperate poikilotherms, assemble and function at body temperatures in the range -1.8 to +2°C. To determine whether alterations to the primary sequence of β tubulin may contribute to enhancement of microtubule assembly at cold temperatures, we have cloned and sequenced a 1.8-kilobase neural β-chain cDNA, Ncnβ1, from an Antarctic rockcod, Notothenia coriiceps neglecta. Based on nucleotide sequence homology, Ncnβ1 probably corresponds to a class-II β-tubulin gene. The 446-residue β chain encoded by Ncnβ1 is closely related (sequence homology ∼95%) both to the neural class-I/II isotypes and to the neural/testicular class-IV variants of higher vertebrates, but the sequence of its carboxy-terminal isotype-defining region (residues 431-446) has diverged markedly (≥ 25% change relative to the I/II/IV referents). Furthermore, the NcnβsZ1 polypeptide contains six unique amino-acid substitutions (five conservative, one nonconservative) not found in other vertebrate brain isotypes, and the carboxyterminal region possesses a unique tyrosine inserted at position 442. We conclude that Ncnβ1 encodes a class-II β tubulin that contains sequence modifications, located largely in its interdimer contact domain, that may contribute to cold adaptation of microtubule assembly. © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240303
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    Dynamics of microfilaments are similar, but distinct from microtubules during cytokinesis in living, dividing plant cells (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 151-155 
    Details
    ISSN: 0886-1544
    Keywords: carboxyfluorescein tubulin ; cell plate formation ; confocal microscopy ; phragmoplast ; rhodamine phalloidin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development and dynamics of the phragmoplast cytoskeleton have been analyzed in living stamen hair cells of Tradescantia. Microtubules and actin microfilaments have been identified by microinjecting either carboxyfluorescein labeled brain tubulin or rhodamine phalloidin. Examination with the confocal laser scanning microscope has permitted sequential imaging of the fluorescent cytoskeletal elements in single living cells progressing through division. Phragmoplast microtubules initially emerge through the lateral coalescence of preexisting interzone microtubules. As cytokinesis progresses, these tightly clustered microtubules shorten in length and expand centrifugally toward the cell periphery. By contrast, the phragmoplast microfilaments appear to arise de novo in late anaphase in close association with the proximal surfaces of the reconstituting daughter nuclei. The microfilaments are oriented parallel to the microtubules but conspicuously do not occupy the equatorial region where microtubules interdigitate and where the cell plate vesicles aggregate and fuse. As development proceeds the microfilaments shorten in length and expand in girth, similar to microtubules, although they remain excluded from the cell plate region. In terminal phases of cell plate formation, microtubules degrade first in the central regions of the phragmoplast and later toward the edges, whereas microfilaments break down more uniformly throughout the phragmoplast. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    Effects of cytochalasin and colcemid on cortical flow in coelomocytes (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 262-273 
    Details
    ISSN: 0886-1544
    Keywords: cortical flow ; coelomocytes ; cytoskeleton ; video enhanced microscopy ; cytochalasin ; colcemid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Sea urchin coelomocytes naturally flatten on a substratum into a discoid morphology and display striking, centripetally directed cortical flow along the radii of the cell when viewed with time lapse, video enhanced microscopy. The rate of cortical flow averaged 4.5 μm/min in the peripheral most 10 μm of cytoplasm but slows considerably in the perinuclear region. Cytochalasin B causes: (1) the flow to stop, (2) the buildup of an actin filament-rich peripheral ridge of cytoskeletal material, (3) the centrifugal dissolution of a portion of the actin cytoskeleton, and (4) the contraction of other portions of the cytoskeleton into foci. Cytochalasin D (CD), on the other hand, causes the flowing actin meshwork to become severed from the edge of the cell and allows it to be drawn at least part way in towards the nucleus. A smaller peripheral ridge of actin filament buildup is also seen with CD. Colcemid induces another striking change in the cytoskeleton. The centripetal progression of the actin is not stopped by colcemid, but shortly after leaving the periphery of the cell, the linear elements within the flow become reoriented into arcs. The long axis of the arcs is roughly parallel with the cell's edge. The effects of all three drugs are reversible. The results are discussed in light of other systems and potential mechanisms for cortical flow. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970260309
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    Control of profilin and actin expression in muscle and nonmuscle cells (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 179-188 
    Details
    ISSN: 0886-1544
    Keywords: protein synthesis ; northern analysis ; BC3H1 cells ; HepG-2 cells ; C2C12 cells ; profilactin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Profilin is a small G-actin binding protein implicated in sequestering actin monomers in vivo. We have quantitated profilin and actin expression in human hepatoma HepG-2 cells and in two mouse myogenic cell lines, BC3H1 and C2C12, to determine whether the expression of profilin and the expression of nonmuscle isoactin or total actin are co-regulated. During differentiation of both muscle cell types, profilin and nonmuscle actin expression decrease in a coordinate manner as shown by measurements of steady state mRNA and newly synthesized protein. In human hepatoma HepG-2 cells, the twofold increase in actin synthesis observed after 24 hours of exposure to cytochalasin D did not result in an increase in profilin synthesis. Thus, profilin and actin expression are not coregulated in all cells. To determine if there is sufficient profilin to sequester a large portion of cellular G-actin, we measured total profilin and G-actin levels in the three cell types. In each case, profilin accounted for less than 10% of the total G-actin on a molar basis. Thus, profilin is not responsible for total G-actin sequestration in these cells. Finally, using poly-L-proline affinity chromatography, we showed that, in the cell types tested, less than 20% of the poly-L-proline purified profilin existed as a complex with G-actin. The profilin in these cells may be interacting with cellular components other than actin. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240305
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  • 59
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    Microinjection of fluorescent brain tubulin reveals dynamic properties of cortical microtubules in living plant cells (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 205-213 
    Details
    ISSN: 0886-1544
    Keywords: microtubule dynamics ; cell morphogenesis ; Nitella pseudoflabelatta ; plant cytoskeleton ; Tradescantia virginiana ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fluorescent brain tubulin, injected into living cells of the green alga Nitella pseudoflabellata and the higher plant Tradescantia virginiana, incorporates into the cortical microtubules, allowing these structures to be observed. With confocal laser scanning microscopy, clear images of microtubules were recorded and changes in microtubule patterns documented. After injection, fluorescent lengths of microtubules appeared within a few minutes and their number and length increased rapidly to a “steady state” over the first 15 min. In many instances, fluorescent microtubules could still be detected several hours after injection. In the cells examined, microtubules are arranged as an array of separate units only occasionally displaying close association or accurate co-alignment with neighboring microtubules. In what we perceive to be the steady state condition, some microtubules remain relatively static, while others undergo rapid changes in length or small translocations. We also document what appears to be bidirectional microtubule elongation during postdepolymerization assembly. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240308
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  • 60
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    Reactivation of demembranated, cytosol-free ram spermatozoa (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 264-273 
    Details
    ISSN: 0886-1544
    Keywords: sperm motility ; axonemes ; sperm fractionation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A procedure for preparing cytosol-free ram sperm models was developed. Sperm are introduced to a Triton X-100-containing demembranation medium layered on top of a discontinuous Percoll gradient. After brief exposure to the demembranating solution, the sperm are separated from the detergent-soluble components by centrifugation through a 55% Percoll layer, finally collecting on top of a 90% Percoll cushion from where they are recovered. Optimum conditions consisted of Triton X-100 at 0.20% and a demembranation time of 35 sec. Cross-sections of midpieces and principal pieces of the demembranated sperm were examined by electron microscopy. With 0.20% Triton X-100 in the demembranation medium, 86% of the cross-sections showed no plasma membranes and the rest had broken plasma membranes. The remaining tail structures appeared to be morphologically intact. Assay of phosphoglucose isomerase as a marker enzyme confirmed that at least 98% of the cytosolic protein was removed. Ram sperm models obtained by this procedure could be reactivated, and the percent motility and beat parameters were similar to those of the intact sperm. Reconstitution with the detergent-soluble components was neither required for, nor enhanced, reactivation. Therefore, demembranated ram sperm do not require a detergent-soluble protein factor for reactivation. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240407
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    Monensin-sensitive cellular events modulate neurite extension on laminin: An example of higher-order regulation of cell motility (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 256-263 
    Details
    ISSN: 0886-1544
    Keywords: laminin ; cell adhesion ; cell motility ; laminin receptors ; receptor internalization ; monensin ; osmolarity ; polylysine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: NG108-15 cells extend “rapid-onset” neurites vigorously within the first hour after plating in minimal serum-free medium on Petri dishes coated with polylysine and laminin (1 ng/mm2). We recently reported that the initial rates of neurite formation and cell translocation are further accelerated in this system when nonspecific substratum attachment sites are partially blocked by polyglutamate, bovine serum albumin, or polyethylene glycol polymers [Smalheiser, N. R. (1991): Dev. Brain Res. 62:81-89]. When cells were plated in the presence of the monovalent cation ionophore monensin (1-5 μM) or hypertonic sucrose (50-100 mM), the initial rate of outgrowth on laminin/polylysine-treated Petri dishes was not affected, yet the acceleration produced by polyglutamate was strongly inhibited. These data indicate that monensin-sensitive intracellular events can regulate neurite extension on laminin indirectly, through modulating the effects exerted on cells by nonspecific substratum sites. Although the critical events affected by monensin remain to be identified, movements of laminin receptors (their clustering, internalization, and recycling) are likely targets for further study. © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240406
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    Abstracts (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 284-312 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970240409
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    Masthead (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cm.970250101
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    Microtubules, ribosomes, and RNA: Evidence for cytoplasmic localization and translational regulation (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 1-9 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970250102
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  • 65
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    DiOC6 staining reveals organelle structure and dynamics in living yeast cells (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 111-128 
    Details
    ISSN: 0886-1544
    Keywords: nucleus ; mitochondria ; karmellae ; confocal microscopy ; DiOC6 ; endoplasmic reticulum ; mitosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When present at low concentrations, the fluorescent lipophilic dye, DiOC6, stains mitochondria in living yeast cells [Pringle et al.: Methods in Cell Biol. 31:357-435, 1989; Weisman et al.: Proc. Natl. Acad. Sci. U.S.A. 87:1076-1080, 1990]. However, we found that the nuclear envelope and endoplasmic reticulum were specifically stained if the dye concentration was increased or if certain respiratory-deficient yeast strains were examined. The quality of nuclear envelope staining with DiOC6 was sufficiently sensitive to reveal alterations in the nuclear envelope known as karmellae. These membranes were previously apparent only by electron microscopy. At the high dye concentrations required to stain the nuclear envelope, wild-type cells could no longer grow on non-fermentable carbon sources. In spite of this effect on mitochondrial function, the presence of high dye concentration did not adversely affect cell viability or general growth characteristics when strains were grown under standard conditions on glucose. Consequently, time-lapse confocal microscopy was used to examine organelle dynamics in living yeast cells stained with DiOC6. These in vivo observations correlated very well with previous electron microscopic studies, including analyses of mitochondria, karmellae, and mitosis. For example, cycles of mitochondrial fusion and division, as well as the changes in nuclear shape and position that occur during mitosis, were readily imaged in time-lapse studies of living DiOC6-stained cells. This technique also revealed new aspects of nuclear disposition and interactions with other organelles. For example, the nucleus and vacuole appeared to form a structurally coupled unit that could undergo coordinated movements. Furthermore, unlike the general view that nuclear movements occur only in association with division, the nucleus/vacuole underwent dramatic migrations around the cell periphery as cells exited from stationary phase. In addition to the large migrations or rotations of the nucleus/vacuole, DiOC6 staining also revealed more subtle dynamics, including the forces of the spindle on the nuclear envelope during mitosis. This technique should have broad application in analyses of yeast cell structure and function. © 1993 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970250202
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  • 66
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    Fimbrin localized to an insoluble cytoskeletal fraction is constitutively phosphorylated on its headpiece domain in adherent macrophages (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 223-233 
    Details
    ISSN: 0886-1544
    Keywords: actin-bundling protein ; phosphorylation ; macrophage fractions ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The actin-bundling protein fimbrin is homologous to l-plastin, a 65kD phosphoprotein expressed in leukocytes and transformed cells [de Arruda et al., J. Cell Biol. 111, 1069-1080]. Because fimbrin is present in cell adhesion sites, we studied the phosphorylation state of fimbrin and its distribution in macrophages sequentially extracted with Triton-X-100 (soluble fraction), Tween 40-deoxy-cholate (cytoskeletal fraction), and SDS (insoluble cytoskeletal fraction). The approximate distribution of fimbrin and actin among these fractions was found to be: 65% fimbrin/55% actin in the soluble fraction, 30% fimbrin/20% actin in the cytoskeletal fraction, and 5% fimbrin/25% actin in the insoluble cytoskeletal fraction. PMA did not alter this distribution. Fluorescence microscopy of acetone-extracted macrophages showed that actin is concentrated in podosomes at the substratum interface and is diffusely distributed throughout the remainder of the cell. Fimbrin colocalizes with actin in podosomes and also exhibits a punctate distribution in the cytoplasm that overlaps with actin. In Tween 40/DOC-extracted cells, podosomes remain, and fimbrin also exhibits a punctate distribution along actin filaments. Metabolic 32PO4 labeling revealed that fimbrin is constitutively phosphorylated and that phosphorylated fimbrin is concentrated in the insoluble cytoskeletal fraction. PMA increased the relative levels of fimbrin phosphorylation twofold but did not alter the pattern of fimbrin fluorescence or the distribution of phosphorylated fimbrin. Limited trypsin digestion and phosphoamino acid analysis demonstrated that phosphorylation occurs specifically on serine residues within the 10kD headpiece domain of fimbrin. Phosphorylation of the headpiece domain could regulate the actin binding and bundling properties of fimbrin, or it could regulate the interaction of fimbrin with other proteins. © 1993 Wiley-Liss, Inc.
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  • 67
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    Multiple sites for subtilisin cleavage of tubulin: Effects of divalent cations (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 282-297 
    Details
    ISSN: 0886-1544
    Keywords: isoelectric focusing ; proteolysis ; cation-tubulin interactions ; microtubules ; GDP-tubulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Limited digestion of pig brain GDP-tubulin by subtilisin was carried out in the presence of Mg2+, Mn2+, Ca2+, Zn2+, or Be2+. Isoelectric focusing, followed by SDS-PAGE, revealed characteristic divalent cation-dependent changes in the α- and β-tubulin cleavage patterns. Previous studies revealed that the β-cleavage pattern is different for heterodimers and microtubules [Lobert and Correia, 1992: Arch. Biochem. Biophys. 296:152-160]. Divalent cation effects on subtilisin digestion of tubulin indicate different classes of divalent cation binding sites. Western blot analysis locates the proteolytic zone at residue 430 or higher in both subunits for all conditions. Turbidity and electron microscopy reveal that GDP-tubulin cleaved by subtilisin in the presence of Mg2+, Ca2+, or Mn2+ forms sheets of rings. Mn2+ induces ring formation in uncleaved GDP-tubulin. Isotype-depleted tubulin was generated by the removal of class III β-tubulin using immunoaffinity chromatography. Subtilisin digestion of the depleted fraction and the purified class III β-tubulin demonstrates that cleavage occurs at three to four distinct sites. Thus, subtilisin-digested tubulin is more heterogeneous than was previously reported and the cleavage sites depend on solution conditions, divalent cations, and the state of assembly. This has important implications for experiments that utilize subtilisin-digested tubulin for studying microtubule-associated protein binding. © 1993 Wiley-Liss, Inc.
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  • 68
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    Motility of intracellular particles in rat fibroblasts is greatly enhanced by phorbol ester and by over-expression of normal p21N-ras (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 254-266 
    Details
    ISSN: 0886-1544
    Keywords: phorbol 12-myristate 13-actate (PMA) ; signal transduction ; sphingosine ; colcemid ; organelles ; video-enhanced microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Particle motility in cultured rat fibroblasts was studied using video-enhanced differential interference contrast microscopy. The average velocity of large bright particles (apparent diameter about 0.5-0.7 μm) was measured in control cells and in cells treated with agents which affected targets related to signal transduction pathways. A Rat-2-derived fibroblast line transfected with a construct containing multiple copies of the N-ras proto-oncogene under the control of dexamethasonesensitive promoter was used as a main experimental model. Dexamethasone treatment was shown to induce high levels of N-ras expression in these cells. This treatment greatly increased the average particle velocity. At the same time dexamethasone did not influence the particle motility in the non-transfected parent cells and in the cells transfected with a construct which did not contain N-ras. Phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), also induced an approximate eightfold increase in the particle rate after several hours of incubation, while sphingosine, an inhibitor of PKC, prevented this activation. Sphingosine alone reduced the particle motility after a 20 min incubation. The particle movements were inhibited also by colcemid. These data show that the activation of N-ras and PKC produced dramatic activation of microtubule-dependent particle motility. A possible role of this activation in signal-induced alterations of cell morphology is discussed. © 1993 Wiley-Liss, Inc.
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    Masthead (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cm.970240101
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    Immunological comparison of 22S, 19S, and 12S dyneins from Paramecium cilia (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 17-28 
    Details
    ISSN: 0886-1544
    Keywords: antibody ; motility ; axoneme ; ATPase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Three forms of dynein (22S, 19S, and 12S) were purified from Paramecium cilia. Two classes of monoclonal antibodies against purified 22S dynein were generated. One class reacted on immunoblots with the heavy chains of 22S, 19S, and 12S dyneins; the second class reacted with an 88 kD intermediate chain of 22S dynein. Polyclonal antiserum to the heavy chains of 22S dynein reacted with the γ-heavy chain of 22S and 19S dyneins. A previously described antiserum raised against 22S dynein [Travis et al.: Biochim. Biophys. Acta 966:73-83, 1988] recognized the γ-heavy chain of 22S dynein which was also present in 19S and 12S dyneins, along with the 88 and 76 kD intermediate chains of 22S dynein. This antiserum was also able to immunoprecipitate dynein from crude extracts of cilia.Electron microscopy revealed that the 22S dynein consisted mainly of two-headed particles with some three-headed particles present. The 12S dynein was mainly one-headed particles. The 19S dynein was a mixture of three-, two-, and one-headed particles. The immunological and electron microscopic studies showed that 19S dynein arises from 22S dynein, and that 12S dynein is heterogeneous, composed of the γ-heavy chain of 22S dynein and a unique dynein ATPase.The polyclonal antibodies were also used to detect cross-reactive proteins in other organisms. Both the anti-heavy chain and the anti-22S dynein sera reacted strongly with 22S outer arm dynein of Tetrahymena, but not with the 14S dynein of this organism. © 1993 Wiley-Liss, Inc.
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  • 71
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    Ciliary dynein of Paramecium tetraurelia: Photolytic maps of the three heavy chains (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 29-38 
    Details
    ISSN: 0886-1544
    Keywords: vanadate ; vanadate-mediated photolysis of dynein ; ATP-binding domain of dynein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ciliate Paramecium tetraurelia presents a powerful system to define the structural basis for dynein functional diversity within a single cell. This analysis will depend on the biochemical resolution of the dynein proteins. As an important first step, the three heavy chains of the ciliary outer arm dynein of paramecium were characterized. Sucrose density gradient centrifugation in a high salt buffer separated the dynein into a 22S species, which contained the α and β heavy chains, and a 12S species, which contained the α chain as well as the inner arm dynein heavy chains. Both the 22S and 12S species retained enzymatic latency as indicated by stimulation of MgATPase activity by 0.1% Triton X-100. An unusual ATP-independent V1-like photolysis of only the β chain provided the basis for estimating that the β chain contributes almost half of the 22S MgATPase activity that is susceptible to V1 photolysis. The combination of the density gradient separation of the partially dissociated dynein and the ATP-independent V1-like photolysis of only the β chain led to the unambiguous assignment of the V1 photolytic products to the appropriate parent heavy chains. An estimate of the molecular sizes of the three heavy chains was obtained. The photolytic peptide maps, which define the ATP-binding domains, were determined for the three heavy chains. © 1993 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240104
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    Steric inhibition of cytoplasmic dynein and kinesin motility by MAP2 (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 1-16 
    Details
    ISSN: 0886-1544
    Keywords: cytoplasmic dynein ; kinesin ; microtubules ; motility ; MAPs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using several in vitro motility assays, we found that motility driven by the microtubule (MT) motors, kinesin and cytoplasmic dynein, could be inhibited by MAP2 but not by tau protein or the MT-binding proteolytic fragment of MAP2.In MT gliding assays, even the presence of one MAP2 molecule per sixty-nine tubulin dimers caused an inhibition of about 75% of MT motility at low concentrations of both motors. The percent inhibition of motility decreased with increasing concentration of either motor, suggesting that the inhibition was the result of competition for access to the MT surface. The decrease in the number of moving MTs with MAP2 was correlated with an increase in the frequency of release of moving MTs from the motor-coated glass. In assays of in vitro vesicular organelle motility and formation of ER networks, the presence of MAP2 inhibited small vesicle movements and to a lesser extent ER network formation.To determine if competition for specific sites on the MT or coating of the MT surface inhibited motility, we used tau protein and the chymotryptic MT-binding fragments of MAP2 to coat MTs. No inhibition was observed and there was even an increase in the number of attached and moving MTs in the gliding assay with tau-coated MTs. Because MAP2, tau and the chymotryptic MT-binding fragments of MAP2 bind to the same domain on tubulin, masking of the MT surface sites does not appear responsible for the inhibition of motility by MAP2. Rather, we suggest that the sidearm of MAP2 interfered with the interaction of motors with MTs and caused a dramatic increase in the rate of MT release. In vivo, MAP2 could play a major role in the generation of cellular polarity even at substoichiometric levels by inhibiting transport on microtubules in specific domains of the cytoplasm. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240102
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    Action of tolytoxin on cell morphology, cytoskeletal organization, and actin polymerization (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 39-48 
    Details
    ISSN: 0886-1544
    Keywords: actin ; microfilament ; stress fiber ; cytochalasin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Tolytoxin, a cytostatic, antifungal macrolide produced by blue-green algae of the genus Scytonema, is a potent, reversible inhibitor of cytokinesis in cultured mammalian cells. Treatment of KB cells with 2-16 nM tolytoxin results in profound morphological changes, beginning with the formation of zeiotic processes and culminating in nuclear protrusion. In L1210 cells, cytokinesis is inhibited by as little as 2 nM tolytoxin, while karyokinesis proceeds normally, resulting in polynucleation. Tolytoxin specifically disrupts microfilament organization in A10 cells, while having no apparent effect on microtubules or intermediate filaments. Tolytoxin inhibited actin polymerization in vitro and also caused the depolymerization or fragmentation of F-actin in vitro. Tolytoxin exhibits effects that closely resemble those of cytochalasin B but is effective at concentrations 1/50-1/1,000 that of cytochalasin B. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240105
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    Masthead (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cm.970240201
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    Native microtubules with a variable number of protofilaments (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 49-53 
    Details
    ISSN: 0886-1544
    Keywords: insect sperm tail ; trichopteran axoneme ; computer image analysis ; axonemal ultrastructure ; accessory tubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Insect spermatozoa are characterized by having a set of accessory tubules that surrounds the microtubular doublets of the axoneme and that are formed from the B-subtubules of the doublets. In trichopteran species, the accessory tubules have an unusually large diameter. Those of one species, Odontocerum albicorne, were seen to have a number of protofilaments that is 19 in the main part of the axoneme, but gradually decreasing to 18, 17, and 16 near the distal tip. The accessory tubule of the trichopteran axoneme has an asymmetrical shape and a skewed orientation, which makes it easy to distinguish a tubule that is viewed from its plus-end from one viewed from the minus-end. The shape of a cross-sectioned protofilament in the trichopteran accessory tubules differs from that of microtubules in general, including accessory tubules of other insects, by being polygonal with the most acute angle pointing centripetally. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240106
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    Molecular cloning and expression of the chicken smooth muscle γ-actin mRNA (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 67-81 
    Details
    ISSN: 0886-1544
    Keywords: development ; cDNA ; actin isoform ; enteric ; myogenesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have investigated the expression of chicken smooth muscle γ-actin mRNA by isolation and characterization of cDNAs representing this actin isoform and utilizing the cDNA to probe RNA from adult and developing cells. Nucleotide sequence elucidated from an apparent full length smooth muscle γ-actin cDNA revealed that it contained 94 bp of 5′ non-translated sequence, an open reading frame of 1131 bp, and 97 bp of 3′ non-translated sequence. Within the 376 amino acid sequence deduced from the chicken cDNA were diagnostic amino acids at the NH2- and COOH-terminal regions which provided unequivocal identification of the γ-enteric smooth muscle actin isoform. In addition, the chicken γ-enteric actin deduced from our cDNA clones was found to differ from the sequence reported in earlier protein studies [J. Vandekerckhove and K. Weber, FEBS Lett. 102:219, 1979] by containing a proline rather than a glutamine at position 359 of the protein, indicating that the avian γ-enteric actin isoform is identical to its mammalian counterpart. Comparison of the 5′ and 3′ non-translated sequence determined from the chicken cDNA to that elucidated for rat, mouse, and human showed that there is not a high degree of cross-species sequence conservation outside of the coding regions among these mRNAs. Northern hybridization analyses demonstrated that the γ-enteric actin mRNA is expressed in adult aorta and oviduct tissues but not in adult skeletal muscle, cardiac muscle, liver, brain, and spleen tissues. The γ-enteric actin mRNA was first observed in measurable quantities in gizzard tissue from 4-5 day embryos and increased in content in developing smooth muscle cells through 16-17 embryonic days. Following this initial increase during embryonic development, the γ-enteric actin mRNA exhibits a decline in content until ∼7 days posthatching, after which there is an increase in content to maximal levels found in adult gizzard tissue. In general, the developmental appearance of the γ-enteric mRNA parallels that observed for this protein in previous studies indicating that the developmental expression of smooth muscle γ-actin is regulated, in part, by an increased content of mRNA in chicken visceral smooth muscle cells during myogenesis. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240108
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    Biochemical and immunochemical identification of a microtubule-binding protein from bovine pancreas (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 381-390 
    Details
    ISSN: 0886-1544
    Keywords: pancreas MAPs ; microtubule-affinity chromatography ; 67 kDa polypeptide ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have identified a 67 kDa heat-stable protein among the proteins which bind specifically to brain microtubules immobilized on a chromatographic support. Its relationship to tubulin and to the cytoskeleton using polyclonal antibodies has been studied. This 67 kDa protein is present in cytoskeleton and microtubule preparations from pancreas. This heat-stable microtubule-associated protein (MAP) copolymerized with phosphocellulose purified brain tubulin. The 67 kDa polypeptide was immunoreactive to antibodies against the 210 kDa MAP from HeLa cells; it also reacted with antibodies against an oligopeptide whose sequence corresponded to the second repeat of mouse brain tau. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970250408
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    Cytoskeletal sheets of mammalian eggs and embryos: A lattice-like network of intermediate filaments (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 85-99 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeletal sheets ; intermediate filaments ; blastomere - blastomere contact ; cross-bridges ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mammalian eggs and embryos possess a major cytoskeletal network composed of large planar “sheets” distributed throughout the cytoplasm. Cytoskeletal sheets are found neither in mammalian somatic cells nor in eggs or embryos of non-mammals. In this study, we have investigated the structural composition of the sheets in eggs and embryos of the golden Syrian hamster by (1) analysis of replicas from quick-frozen, deep-etched specimens, (2) analysis of thick, resinembedded specimens using an intermediate voltage electron microscope (IVEM), (3) laser diffraction of EM images, (4) differential extraction with detergents, and (5) immunocytochemistry. Our results indicate that each sheet is composed of two closely apposed arrays of 10-nm filaments. Each filament within an array is held in register with its neighbor by lateral cross-bridges and the two parallel arrays of filaments are interconnected by periodic cross-bridges about 20 nm in length. Laser diffraction of negatives from IVEM images indicates that each array is composed of fibers that form a square lattice, and the two arrays are positioned in register by cross-bridges forming a single sheet. This lattice forms the skeleton of the sheets which is covered with a tightly packed layer of particulate material. By incubation in media containing different ratios of mixed-micelle detergents, it is possible to remove components sequentially from the sheets and to extract the particulate material. Immunocytochemical localization demonstrates that the sheets bind antibodies to keratin, and to a small extent actin, but do not bind antibodies to vimentin or tubulin. Examination of sheets within embryos at the time of embryonic compaction demonstrates that the sheets begin to fragment and disassemble in regions of blastomeres where desmosomes form, but undergo no structural alterations in interior and basal surfaces of the blastomeres. In regions of blastomere - blastomere contact the sheets fragment and associate with granules resembling keratohyalin granules found in keratinocytes. © 1993 Wiley-Liss, Inc.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240202
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    Morphology of nexin links in relation to interdoublet sliding in the sperm flagellum (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 109-118 
    Details
    ISSN: 0886-1544
    Keywords: motility ; flagellum ; spermatozoon ; nexin ; freeze-etch ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this work, we examine whether the “nexin” linkages of the flagellum can extend in length to accommodate interdoublet sliding. Flagellar bends of large angle were induced in bull spermatozoa by hypotonic treatment. It is argued that this produces large interdoublet displacements that are, nevertheless, still within physiological limits. Such flagella were examined by the rapid-freeze, deep-etch techique and the nexin linkages identified by their position in relation to the inner dynein arms and by their straplike, bipartite, morphology. They were found to bridge perpendicularly (or occasionally at an angle) between the A- and B-tubules of adjacent doublets. The nexin linkages were no more than ∼20 nm in length, even in regions in which ∼200 nm of sliding could be inferred. Variable registration between adjacent nexin rows gave some further support to the assumption that sliding had indeed taken place. From this, it is concluded that elastic deformation of the links, such as would accommodate interdoublet sliding, does not occur; some form of displacement must occur between nexin and the adjacent B-tubule. © 1993 Wiley-Liss, Inc.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240204
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    Incorporation of microinjected mutant and wildtype recombinant tropomyosins into stress fibers in fibroblasts (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 119-128 
    Details
    ISSN: 0886-1544
    Keywords: actin ; actin filament assembly ; actin binding sites ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The structural requirements for assembly of tropomyosin into stress fibers were investigated by microinjecting wildtype and four mutant striated chicken muscle α-tropomyosins expressed in E. coli as fusion and nonfusion proteins into cultured rat embryo fibroblasts, followed by localization of tropomyosin using indirect immunofluorescence. The results show that the determinants for stress fiber incorporation in living cells correlate with the in vitro actin affinity of these tropomyosins. Wildtype recombinant protein incorporated into stress fibers both when the amino terminus was unacetylated and when it was blocked with an 80-residue fusion protein [Hitchcock-DeGregori, S.E., and Heald, R.W. (1987): J. Biol. Chem. 262:9730-9735]. The pattern of incorporation was indistinguishable from that of tropomyosin isolated from chicken pectoral muscle. The striated α-tropomyosin incorporated into stress fibers, even though this isoform is not found in nonmuscle cells. Three recombinant mutant tropomyosins in which one-half, two-thirds, or one actin binding site was deleted were tested [Hitchcock-DeGregori, S.E., and Varnell, T.A. (1990): J. Mol. Biol. 214:885-896]. Only the fusion protein with a full actin binding site deleted incorporated into stress fibers. However, the unacetylated, nonfusion proteins with one half and one actin binding site deleted incorporated into stress fibers, consistent with the ability of troponin to promote the actin binding in vitro. A fourth mutant, in which the conserved amino-terminal nine residues were deleted, did not incorporate into stress fibers, consistent with the complete loss of function of this mutant [Cho, Y.J., Liu, J., and Hitchcock-DeGregori, S.E. (1990): J. Biol. Chem. 265:538-545]. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240205
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    Effects of taxol and taxol/hyperthermia treatments on the functional polarization of cytotoxic T lymphocytes (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 129-138 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; MTOC ; centrosome ; pericentriolar material ; cytolytic activity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Immunofluorescence staining, electron microscopy, and (51Cr) cytolytic release assays are used to investigate the effects of taxol and taxol/hyperthermia treatments on the microtubule organization and cytolytic activity of cytotoxic T lymphocytes (CTLs). A 4 h treatment of CTLs with 1 μM taxol results in an extensive reorganization of the microtubule system to form one to a few large microtubule bundles that extend from the centrosome. The Golgi apparatus is not disrupted by this treatment and remains associated with the microtubule organizing centre (MTOC). This microtubule reorganization has no effect on the ability of CTLs to orient their MTOC towards a bound target cell, nor on their cytolytic activity. In control CTLs, not treated with taxol, a mild hyperthermia treatment (42°C, 30 min) results in an aggregation of the pericentriolar material, a loss of MTOC orientation, an inhibition of cytolytic activity, and a disorganization of the microtubule system [Knox et al.: Exp. Cell Res. 194:275-283, 1991]. In contrast, in taxol-treated CTLs the stabilized microtubule bundles are unaffected by such hyperthermia treatment; however, the other effects of hyperthermia appear identical in control and taxol-treated CTLs. These results indicate that a dynamic, radially arranged microtubule array is not required for the functional polarization of CTLs and suggest that a component of the pericentriolar material may play a key role in effecting MTOC orientation. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240206
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    Decreased levels of the high molecular weight subunit of neurofilaments and accelerated neurofilament transport during the recovery phase of 2,5-hexanedione exposure (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 133-143 
    Details
    ISSN: 0886-1544
    Keywords: 2,5-hexanedione ; neurofilament ; slow axonal transport ; neurofilamentous axonopathy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The neurotoxicant 2,5-hexanedione (HD) causes the accumulation of neurofilaments in the distal axon and an acceleration of neurofilament transport proximal to the site of their accumulation. It has been proposed that the acceleration of transport is due to the direct reaction of HD with neurofilament proteins and, conversely, that this acceleration is a secondary response of the axon to injury. The objective of this study was to determine whether the response of axons to HD intoxication includes acceleration of neurofilament transport. Pulse labeling was used to analyze neurofilament transport in age-matched rats exposed to HD or PBS. The animals receiving HD were exposed either throughout the period of radiolabel transport, or prior to the pulse labeling of neurofilament proteins. If acceleration of the rate of neurofilament transport was due to the direct reaction of HD with proteins, then neurofilaments synthesized after the exposure period should travel at control rates, since these proteins would not have been exposed to the toxicant. After 28 days of transport, optic nerve proteins were examined using SDS-PAGE, fluorography, and computerized densitometry. In both HD-treated groups, neurofilament transport was accelerated relative to age-matched control animals. In addition, the amount of NFH was decreased relative to other neurofilament subunits. The combination of accelerated transport and a diminished proportion of NFH is similar to the observations of neurofilament axonal transport during growth and development. These observations suggest that this persistent, secondary effect is a reparative response to injury that recapitulates axonal growth and development. © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970260205
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    Microtubule sliding in reduced-amplitude bending waves of Ciona sperm flagella: Resolution of metachronous and synchronous sliding components of stable bending waves (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 144-162 
    Details
    ISSN: 0886-1544
    Keywords: axoneme ; bend propagation ; flagella ; microtubule sliding ; motility ; vanadate ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubule sliding associated with the bending of reactivated flagella of demembranated spermatozoa of the tunicate, Ciona, has been analyzed using a descriptive model that permits quantitation of metachronous and synchronous components of sliding. Reduced-amplitude bending waves, obtained by addition of increased salt (K acetate), lithium, or vanadate to the reactivation solutions, have been examined. Increased K acetate can decrease bend angle by as much as 70% with little change in frequency.In all cases, a decrease in the amplitude, or bend angle, of propagated bends is measured as a decrease in the metachronous component of sliding and is associated with a reduction in the growth of new bends after they begin to propagate during the second half-cycle of bend development. At higher K acetate concentrations, bend growth during the second half-cycle of bend development is very strongly reduced and may even become negative. A disparity between the rates of bend growth in the first and second half-cycles of bend development corresponds to a large amount of synchronous sliding in the distal portion of the flagellum. When the synchronous sliding component is large, the sliding velocity in a propagating bend decreases to near-0 values and may even reverse its direction as the bend propagates through the mid-region of the flagellum. Since these large perturbations of sliding velocity do not interfere with regular propagation of bends with nearly constant bend angle, the bend propagation mechanism cannot operate by metachronous control of the velocity of sliding, and is unlikely to operate by local monitoring of either the amount or velocity of sliding. These observations therefore argue against models in which active sliding is regulated by shear or sliding velocity, and make curvature-controlled models relatively more attractive.In many cases, a reduction in sliding during bend initiation (the first half-cycle of development of new bends) also contributes to the decreased amplitude of propagated bends. These changes in bend initiation are similar in both full-length flagella and in flagella shortened by breakage. The amount of sliding that occurs during bend initiation is relatively independent of the distribution of sliding between metachronous and synchronous components in the distal part of the flagellum. These observations therefore provide additional evidence that bend initiation and bend propagation are independent and separable processes. © 1993 Wiley-Liss, Inc.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970260206
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    CENP-F is a ca 400 kDa kinetochore protein that exhibits a cell-cycle dependent localization (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 214-226 
    Details
    ISSN: 0886-1544
    Keywords: mitosis ; autoantibodies ; kinetochore ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have identified a novel .ca 400 kDa cell-cycle dependent kinetochore associated protein in human cells, designated CENP-F, using human autoimmune serum. Immunofluorescence staining using the native serum, affinity purified antibodies, or antibodies raised against a cloned portion of CENP-F first reveals CENP-F homogeneously distributed throughout the nucleus of HeLa cells in the G2 stage of the cell cycle. Progression into prophase is accompanied by the localization of CENP-F to all the kinetochore regions of the karyotype. Kinetochore association is maintained throughout metaphase, but at the onset of anaphase CENP-F is no longer detected in association with the kinetochore but is found at the spindle mid-zone. By telophase, it is concentrated into a narrow band on either side of the midbody. Studies of the interaction of CENP-F with the kinetochore indicate that this protein associates with the kinetochore independent of tubulin and dissociation is dependent on events connected with the onset of anaphase. Nuclease digestion studies and immunoelectron-microscopy indicate that CENP-F is localized to the kinetochore plates and specifically to the outer surface of the outer kinetochore plate. The distribution of CENP-F closely parallels that of another high molecular weight kinetochore associated protein, CENP-E. Comparative studies indicate that there are antibodies in the CENP-F reactive autoimmune serum that recognize determinants present in the central helical rod domain of CENP-E. Immune depletion experiments confirm that CENP-F exhibits the distribution pattern in cells that was seen with the native autoimmune serum. © 1993 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970260305
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    Regulation of microtubule dynamic instability (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 275-281 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970260402
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    Smooth muscle myosin subfragment-1 is a kinetic analogue for heavy meromyosin in the extended conformation (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 291-300 
    Details
    ISSN: 0886-1544
    Keywords: conformational transition ; single turnover assays ; ionic strength ; S1/S2 junction ; actin-activated ATPase activity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The 10S→6S (Flexed→Extended) transition in smooth muscle myosin is related to increased ATPase activity, but there is controversy over whether the analogous 9S→7S transition in HMM is also associated with ATPase activity. We therefore studied the association of ionic strength, phosphorylation, and ATPase activity for HMM as compared to S1 which has no apparent flexed conformation. In addition, we performed both steady state and single turnover analyses, to control for artifacts due to multiple subfragment populations that might skew steady state results.At low ionic strength where myosin and HMM are in the flexed conformation, HMM had a near zero ATPase activity while S-1 had a high ATPase rate (0.07 s-1). At 400 mM ionic strength, where both myosin and HMM are in the extended conformation, S1 and HMM had the same ATPase rate (0.04 s-1). Phosphorylation did not affect S1 significantly, but shifted the HMM curve to higher rates at lower ionic strengths. Both steady state and single turnover experiments gave the same results, indicating that steady state results were not skewed by multiple subfragment populations. These data indicate that HMM has a conformation-ATPase relation similar to that observed with myosin. Furthermore, these findings suggest that the S1 ATPase rate corresponds to that of HMM in the extended conformation. © 1993 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970260404
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    Role of phosphorylation in keratin and vimentin filament integrity in cultured thyroid epithelial cells (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 325-339 
    Details
    ISSN: 0886-1544
    Keywords: calyculin A ; phosphatase 1/2A ; intermediate filament disruption ; actomyosin contraction ; C-kinase ; intermediate filament protein kinase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytokeratin and vimentin intermediate filaments (IFs) possess relatively stable polymeric properties which can be affected by phosphorylation. The present study, using cultures of thyroid epithelial cells, shows by indirect immunofluorescence that these cells contain both keratin tonofilament and vimentin IF complexes. Immunoblots of Triton X-100 insoluble cytoskeletal fractions show vimentin, and ∼52 kDa type II and 40/38 kDa type I keratins. Under “basal” conditions, following prelabeling of cells with [32PO4], vimentin is not significantly phosphorylated, while both type II and I keratins are phosphorylated. Treatment of cells for 20 min with 1 mM dbcAMP or 0.4 μM 12-O-tetradecanoylphorbol-13-acetate (TPA), to stimulate protein kinase A and C, respectively, has no effect on either the phosphorylation state or cytoplasmic filament integrity of vimentin. However, while dbcAMP also does not affect keratin filaments, TPA increases both type II and I phosphorylation ∼3-fold, and concomitantly disrupts tonofilament complexes associated with the nucleus, cytoplasm, and desmosomes. TPA-treated cells also show dramatic shape changes and protrusive activity. Tryptic peptide mappings show phosphorylations of at least 6 and ∼2 additional sites for type II and I keratins, respectively, vs. [32P]-peptides from control cells. Treatment of [32PO4]-labeled cells with 0.4 μM calyculin A to inhibit types 1 and 2A phosphatase activity causes hyperphosphorylation of both vimentin and keratin, disruption of IF complexes, and actomyosin/cell contraction within 20 min. Quantitatively, ∼50% of the type II/I keratin hyperphosphorylations are at some sites apparently also phosphorylated after TPA treatment. Thus, in these cells, IFs are specifically and differentially affected and regulated by the activity of several kinases. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970260407
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    Primary and secondary chick heart fibroblasts: Fast and slow-moving cells show no significant difference in microtubule dynamics (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 233-244 
    Details
    ISSN: 0886-1544
    Keywords: microtubule dynamics ; fibroblasts ; microinjection ; cold stability ; drug stability ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Highly motile chick heart fibroblasts in primary culture (1° CHFs) gradually convert into much slower-moving secondary (2°) cells. The polarized movement of the latter, but not the former, cell type has been found to be dependent on an intact microtubule (MT) network [Middleton et al., 1989, J. Cell Sci. 94:25-32]. To investigate the comparative stability of the MT networks of 1°s and 2°s, turnover was investigated by microinjection of biotin-labeled brain tubulin to act as a reporter. MTs in both cell types were found to be very dynamic, with the MT networks effectively disassembled by about 30 min in 1° CHFs and 60 min in 2° CHFs, with mainly MT fragments remaining beyond these times. All MTs and fragments were found to have turned over by 1 h in 1° CHFs and 80 min in 2°s. Because 2° CHFs were found to be on average six times larger than 1°s, the difference in MT turnover time was considered largely due to the size difference. For both 1° and 2° cells, the more slowly turning over MTs were generally curly and perinuclear in distribution, resembling stable MTs in other systems, but they appeared significantly earlier in CHFs. However, no discrete subpopulations of slower turning over MTs were found to be associated with either the leading edges or the processes of either cell type. In addition, no major differences were identified in the patterns of modified α-tubulin along the MTs or of MT cold or drug stability. It is concluded that MTs do not have a direct structural or skeletal function in maintaining a polarized 2° CHF cell shape, but rather play an ancillary role. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240404
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  • 89
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    Elastic properties of titin filaments demonstrated using a “freeze-break” technique (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 274-283 
    Details
    ISSN: 0886-1544
    Keywords: immunoelectron microscopy ; rabbit psoas ; elasticity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A “freeze-break” technique (Trombitás, K.: Acta Biochim. Biophys. Hung. 6:419-427, 1971) and immunoelectron microscopy were used to study the elastic properties of titin filaments. Small bundles of freshly prepared rabbit psoas muscle fibers were quickly frozen and broken under liquid nitrogen to fracture sarcomeres in planes perpendicular to the filament axis, in each of various regions along the sarcomere. The still-frozen specimens were thawed during fixation to allow elastic filaments to retract. The broken specimens were then labelled with monoclonal anti-titin antibodies against an unique epitope in the I-band.The titin epitopes were normally positioned symmetrically about the Z-line. However, in sarcomeres broken at the A-I junction, the epitopes no longer remained symmetrical: the titin filaments in the broken half-sarcomere retracted, independently of the thin filaments, forming a dense band just near the Z-line. The retracted density apparently did not reach the Z-line; retraction stopped at the level of the so-called N1-line. In sarcomeres broken at the Z-line level, the titin filaments retracted in the opposite direction. In this case the titin epitope retracted all the way to the ends of the thick filaments.It appears then that titin molecules form elastic filaments that are independent of thin filaments in most of the I-band. Near the Z-line, however, the titin filaments either have an inelastic domain or associate firmly with the thin filaments at the N1-line level. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240408
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  • 90
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    Ultrastructure and immunocytochemistry of the isolated human erythrocyte membrane skeleton (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 30-42 
    Details
    ISSN: 0886-1544
    Keywords: spectrin ; cytoskeleton ; erythrocyte ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Isolated skeletons from human erythrocyte ghosts were studied using immunogold labeling; negative staining; and quick-freeze, deep-etch, rotary replication with Pt/C (QFDERR). Isolated skeletons visualized by QFDERR were similar to the negatively stained skeletons in that the proteins spectrin, actin, and ankyrin could be easily distinguished. However, the quick-frozen skeletons had two fewer filaments (4.2 ± 0.7) at an actin junction. Immunogold labeling of skeletons with site-specific spectrin antibodies not only confirmed the designation of these filaments as spectrin molecules, but indicated that about 30% of spectrin filaments form non-actin junctions consistent with the hexameric organization of these filaments. Many of the filaments displayed a striking banding pattern indicative of underlying substructure. Isolated skeletons prepared by QFDERR also showed evidence of laterally associated spectrin filaments. These associations, as well as many hexamer junctions, are lost during negative staining. Negative staining also apparently caused ∼21% of the spectrin filaments to separate into their monomeric subunits. These results indicate that the surface tension imposed during negative staining of isolated skeletons can cause a loss of interactions normally present in the intact membrane skeleton. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970250105
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  • 91
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    βIV is the major β-tubulin isotype in bovine cilia (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 19-29 
    Details
    ISSN: 0886-1544
    Keywords: photoreceptor ; retina ; cilium ; trachea ; microtubules ; immunocytochemistry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Four different isotypes of β-tubulin are known to be expressed in mammalian brain. Monoclonal antibodies against βII, βIII, and βIV were used to characterize the β-tubulin isotypes in two ciliated bovine tissues: non-motile sensory cilia of retinal rod cells and motile cilia of tracheal epithelium. Retinal rod outer segment (ROS) connecting cilia and cytoskeletons were purified by density gradient centrifugation. This preparation contained more than 20 major protein protein components, as shown by dodecyl sulfate polyacrylamide gel electrophoresis. Electroblots were used to quantitate the relative amounts of βII, βIII, and βIV. The connecting cilium and cytoskeleton of the rod outer segment has less type III β-tubulin than brain and more type IV. The ratio of βIV to βII in the ROS is nearly a factor of 8 larger than in brain. Electron microscopic immunocytochemistry showed extensive labeling of cilia by anti-type IV in thin sections of retinas and trachea, and also in purified ROS cilia and cyoskeletons. Labeling of cilia by anti-βII was also observed, although in the purified ROS cilia and cytoskeleton, the anti-βII labeling was primarily on amorphous non-ciliary material. The results suggest that both motile and non-motile cilia are enriched in the type IV β-tubulin subunit. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970250104
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  • 92
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    Colchicine-induced stimulation of PMN motility related to cytoskeletal changes in actin, α-actinin, and myosin (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 10-18 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; blebs ; locomotion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Colchicine-induced stimulation of polymorphonuclear leukocyte (PMN) locomotion is an interesting model because extension of blebs at the front occurs at a rate (about 2.4 μm/s) which is far above that reported for growth of actin filaments. The following cytoskeletal changes were observed in colchicine-treated PMNs: (1)a small increase in cytoskeleton-associated actin was noted, as well as a somewhate more pronounced increase in cytoskeleton-associated α-actinin, as compared with untreated or DMSO-treated controls. There was, however, no measurable increase in F-actin as determined by NBD-phallacidin blinding; (2)the values for the ratio (α-actinin/actin) are lower in PMNs treated with colchicine for 30 min, as compared with PMNs stimulated with fNLPNTL for 1 minute (non-polar ruffling cells) or 30 min (polarized locomoting cells); thus, this ratio may depend on the type of PMN motility; (3) in polarized PMNs F-actin was mainly located linearly all along the cell membrane; there was more intense staining at the front of the cells; (4) α-actining appeared to colocalize with F-actin at the leading front, but not with F-actin at the tail of polarized cells; (5) myosin was preferentially found at the rear part of polarized cells but not or only to a small extent at the front. Our data indicate a close functional correlation between microtubules and microfilaments. We speculate that F-actin in combination with α-actinin promotes expansion of pseudopods, whereas myosin combined with F-actin promotes contraction. In more general terms we suggest that different forms of PMN motility are generated by differential selective interaction of cytoskeletal compnents and variations in the composition of the cytoskeleton in different sites of the same cells. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970250103
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  • 93
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    High level expression of nonacetylatable α-tubulin in Chlamydomonas reinhardtii (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 158-170 
    Details
    ISSN: 0886-1544
    Keywords: acetylation ; epitope-tagging ; flagella ; tubulin isoforms ; microtubules ; rubisco ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Following the discovery of acetylated α-tubulin in the flagella of Chlamydomonas, many studies have documented the presence of acetylated α-tubulin in a variety of evolutionarily divergent organisms. While this posttranslational modification may define an isoform with a unique function, the primary effect of α-tubulin acetylation remains unknown. To study the function of α-tubulin acetylation, we have transformed Chlamydomoas, a organism in which almost all of the flagellar tubulin ad a subset of the cytoplasmic microtubules are acetylated, with a α1-tubulin gene whose product cannot be acetylated. Specifically, the codon for lysine 40, the lysine that is acetylated, has been replaced with the codons of nonacetylatable amino acids. To distinguish mutagenized α-tubulin from that produced by the two endogenous α-tubulin genes, mutant α-tubulin was tagged with an epitope from influenza virus hemagglutinin. Utilizing the constitutive Chlamydomonas rubisco small subunit S2 promoter, we have obtained in selected clones high levels of nonacetylatable α-tubulin expression approximating 50-70% of the total flagellar α-tubulin. Immunofluorescence and immunoblot analysis of transformed cells indicated that nonacetylatable α-tubulin could assemble, along with endogenous α-tubulin, into both cytoplasmic and flagellar microtubules. However, no gross phenotypic effects were observed, suggesting that the effect of α-tubulin acetylation is subtle. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970250205
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  • 94
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    Perspectives on tubulin isotype function and evolution based on the observation that Tetrahymena thermophila microtubules contain a single α- and β-tubulin (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 243-253 
    Details
    ISSN: 0886-1544
    Keywords: multitubulin hypothesis ; neighbor-joining method ; ciliate ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have cloned and sequenced the two β-tubulin genes of the ciliated protozoan Tetrahymena thermophila. The two genes encode identical 443 amino acid peptides which are 99.7% identical to the β-tubulin proteins of T. pyriformis and 95% identical to human β1 tubulin. T. thermophila contains only one β-tubulin gene (Callahan et al., 1984: Cell 36:441-445). Thus, all of the extremely diverse microtubule structures in this unicellular organism can be formed from a single α- and a single β-tubulin peptide. We have also carried out a phylogenetic analysis of 84 complete β-tubulin peptide sequences. This analysis supports two hypotheses regarding β-tubulin evolution and function: (1) Multifunctional β-tubulins are under greater evolutionary constraint than β-tubulins present in specialized cells or in cells with very few microtubule related functions, which can evolve rapidly; and (2) Cells which form axonemes maintain a homogeneous population of tubulins. © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970250305
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  • 95
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    Centrosome repositioning immediately following karyokinesis and prior to cytokinesis (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 239-247 
    Details
    ISSN: 0886-1544
    Keywords: centrosome ; telophase ; microtubule ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The behaviour of the centrosome immediately following cell division in tissue culture cells has been investigated. We find that following karyokinesis, but preceding cytokinesis, sister centrosomes relocate from the spindle poles to a position adjacent to the intercellular bridge. This repositioning is accompanied by the appearance of a microtubule bundle that extends from the poleward region of the cell to the centrosome and increases in length as the centrosome approaches the intercellular bridge. Disruption of this bundle with colcemid interrupts centrosome repositioning. In contrast, centrosome repositioning persists in late mitotic cells grown in the presence of cytochalasin D. However, the position of the microtubule-centrosome complex within the cell is randomized suggesting that the path, but not the process, of centrosome repositioning is dependent on an intact actin filament network. This study points out, for the first time, that the complex migration of the centrosome preceding mitosis is paralleled by an equally complex set of events following cell division. We suggest that post-mitotic centrosome repositioning may play a role in ensuring that daughter cells have equal but opposite polarity and may reflect an interrelationship between the establishment of the interphase cytoskeleton and the completion of cytokinesis. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970260307
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  • 96
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    In vitro functional characterization of bacterially expressed human fibroblast tropomyosin isoforms and their chimeric mutants (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 248-261 
    Details
    ISSN: 0886-1544
    Keywords: human fibroblast tropomyosins ; actin-binding protein ; caldesmon ; actin-tropomyosin-activated HMM ATPase ; motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: At least eight tropomyosin isoforms (hTM1, hTM2, hTM3, hTM4, hTM5, hTM5a, hTM5b, and hTMsmα) are expressed from four distinct genes in human fibroblasts. In order to elucidate isoform properties, we have subcloned hTM3 and hTM5 full-length cDNAs, as well as their chimeric cDNAs into the bacterial expression pET8C system. Bacterially expressed tropomyosin isoforms (called PEThTM3, PEThTM5. PEThTM5/3, and PEThTM3/5) were purified and characterized. Under optimal binding conditions, the binding of PEThTM5 isoform to F-actin was stronger than the PEThTM3 isoform. However, analysis of actin-binding by the McGhee and von Hippel equation revealed that PEThTM3 exhibits higher cooperativity in binding than PEThTM5 does. Furthermore, the chimera PEThTM5/3 which possessed the N-terminal fragment of hTM5 fused to the C-terminal fragment of hTM3 had even stronger actin binding ability. The reverse chimera PEThTM3/5 which possessed the N-terminal fragment of hTM3 fused to the C-terminal fragment of hTM5 demonstrated greatly reduced affinity to actin filaments. In addition, both chimeras had different KCl requirements for optimal binding to F-actin than their parental tropomyosins. A bacterially made C-terminal fragment of human fibroblast caldesmon (PETCaD39) and native chicken gizzard caldesmon were both able to enhance the actin-binding of these bacterially expressed tropomyosins. However, PETCaD39′s enhancement of binding to F-actin was greater for PEThTM5 than PEThTM3. Under 30 mM KCl and 4 mM MgCl2, the low Mr isoform PEThTM5 appeared to be able to amplify the actin-activated HMM ATPase activity by 4.7 fold, while the high Mr isoform PEThTM3 stimulated the activity only 1.5 fold. The higher enhancement of ATPase activity by PEThTM5 than by PEThTM3 suggested that the low Mr isoform hTM5 may be more involved in modulating nonmuscle cell motility than hTM3. These results further suggested that different isoforms of tropomyosin might have finite differences in their specific functions (e.g., cytoskeletal vs. motile) inside the cell. © 1993 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970260308
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  • 97
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    Contractile protein dynamics of myofibrils in paired adult rat cardiomyocytes (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 301-312 
    Details
    ISSN: 0886-1544
    Keywords: intercated discs ; microinjection ; actin ; alpha-actinin ; vinculin ; myosin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The purpose of this study was to determine how quickly contractile proteins are incorporated into the myofibrils of freshly isolated cardiomyocytes and to determine whether there are regions of the cells that are more dynamic than others in their ability to incorporate the proteins. Paired cardiomyocytes joined at intercalated discs and single cells were isolated from adult rats, and microinjected 3 hours later with fluorescently labeied actin, alpha-actinin, myosin light chains, and vinculin. The cells were fixed and permeabilized at various period, 5 seconds and longer, after microinjection. Actin became incorporated throughout the I-Bands in as short a time as 5 seconds. The free edges of the cells, which were formerly intercalated discs, exhibited concentrations of actin greater than that incorporated in the I-Bands. This extra concentration of actin was not detected, however, at intact intercalated discs connecting paired cells. Alpha-actinin was incorporated immediately into Z-Bands and intercalated discs. Vinculin, also, was localized at the Z-Bands and at intercalated discs, but in contrast to alpha-actinin, there was a higher concentration of vinculin in the region of the intact intercalated discs. Both alpha-actinin and vinculin were concentrated at the free ends of the cells that were formerly parts of intercalated discs. Myosin light chains were observed to incorporate into the A-Bands in periods as short as 5 seconds. These results suggest that the myofibrils of adult cardiomyocytes may be capable of rapid isoform transitions along the length of the myofibrils. The rapid accumulation of fluorescent actin, alpha-actinin, and vinculin in membrane sites that were previously parts of intercalated discs, may reflect the response to locomotory activity that is initiated in these areas as cells spread in culture. A similar response after an injury in the intact heart could allow repair to occur. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970260405
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  • 98
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    Assembly dynamics of actin in adherent human neutrophils (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 340-348 
    Details
    ISSN: 0886-1544
    Keywords: neutrophils ; actin ; laminin ; fibronectin ; adherence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have extended our previous studies of adherent neutrophils and compared actin depolymerization and intracellular calcium changes induced by adherence to laminin and fibronectin. In order to accurately assess cellular actin changes, F-actin depolymerization in the cell lysates must be inhibited. We found that phalloidin or 3.7% formaldehyde treatment effectively inhibited the depolymerization of F-actin fragments following cell lysis. Formaldehyde and phalloidin treatment reduced G-actin levels 75-80% in suspended cells, 35-73% in cells adherent for 1 min, and about 50% for cells adherent for 3 min. When the actin was fixed, there were highly significant differences in G-actin levels between the suspended and adherent cells as compared with unfixed cells. Adhesion to both laminin and fibronectin initiated a rapid rise in G-actin with a corresponding decrease in F-actin. However, the changes were more pronounced in cells adherent to laminin. The peak of depolymerization occurred by 1 min and, thereafter, G-actin decreased and F-actin increased reaching a steady state at 5 min. Adhesion to both laminin- and fibronectin-coated surfaces was accompanied by an increase of [Ca2+]i with a peak at 3 min, followed by a decrease from 3-5 min and a steady state attained between 5 and 10 min. The rise of [Ca2+]i in laminin-adherent cells was about twice that in fibronectin-adherent cells at 3 min (P 〈 0.02). Pertussis toxin, H-7, and staurosporin treatments did not alter the dynamic changes of actin in adherent cells, suggesting that these metabolic events are transduced by a G-protein and Protein Kinase C independent mechanism. The results support the hypothesis that a transient mobilization of F-actin to a monomeric pool, which then serves as a source for further repolymerization, is induced by adherence of neutrophils to extracellular matrix proteins. © 1993 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970260408
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  • 99
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    Myosin heavy chain dephosphorylation during cytokinesis in dividing sea urchin embryos (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 369-380 
    Details
    ISSN: 0886-1544
    Keywords: myosin heavy chain ; cytokinesis ; dephosphorylation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Myosin heavy chain (MHC) phosphorylation was examined throughout the period of first cleavage in developing sea urchin embryos. MHC was found to be phosphorylated in these cells and, furthermore, the relative state of myosin phosphorylation was found to decrease as cells progressed through cytokinesis. Following the completion of cytokinesis, the relative state of MHC phosphorylation returned to levels observed in precytokinesis cells. The above results were obtained with myosin immunoprecipitated from whole cell lysates. In order to specifically examine the phosphorylation, state of MHC in the cleavage furrow, a protocol was developed for the isolation of intact contractile rings from dividing sea urchin embryos. MHC was immunoprecipitated from isolated contractile rings and the relative phosphorylation state of this MHC was compared with that of MHC isolated from whole cell lysates prepared at the same time. MHC from isolated contractile rings was found to be significantly less phosphorylated than total cellular MHC, suggesting a role for MHC dephosphorylation during cytokinesis. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970250407
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  • 100
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    Actin-binding protein is a component of bovine erythrocytes (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 100-108 
    Details
    ISSN: 0886-1544
    Keywords: actin-binding protein ; filamin ; erythrocytes ; membrane skeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Actin-binding protein (ABP) is a well-characterized polypeptide capable of crosslinking filamentous actin. To date, this polypeptide has been shown to exist in a number of tissues and cultured cell lines. This report shows that by using a panel of three monoclonal antibodies for immunoblotting and immunofluorescence analysis, that ABP is present in bovine erythrocytes. Moreover, the data obtained suggest that this protein is a component of the erythrocyte membrane skeleton. Additionally, bovine erythrocyte ABP is shown to possess both an apparent molecular weight and an isoelectric point identical to that of bovine smooth muscle filamin, implying that these two polypeptides are identical. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970240203
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