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  • Inorganic Chemistry  (10,401)
  • Cell & Developmental Biology  (7,819)
  • Aerodynamics
  • 1990-1994  (10,134)
  • 1950-1954  (2,356)
  • 1940-1944  (2,309)
  • 1910-1914
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  • 1
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    Windsurfer Fin (1994)
    In:  CASI
    Details
    Publication Date: 2018-06-09
    Description: A NASA report detailing a wind tunnel investigation of a variable camber and twist could effectively reduce drag, thus improving performance. The resulting VooDoo fin is made of composite materials, has a rigid internal spar and a flexible polymer exterior coating. It is computer-designed and exceptionally durable.
    Keywords: Aerodynamics
    Type: Spinoff 1994; 79; NASA-NP-214
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  • 2
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    Simplified Aerodynamic and Structural Modeling for Oblique All-Wing Aircraft. Phase 2: Structures (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Any aircraft preliminary design study requires a structural model of the proposed configuration. The model must be capable of estimating the structural weight of a given configuration, and of predicting the deflections which will result from foreseen flight and ground loads. The present work develops such a model for the proposed Oblique All Wing airplane. The model is based on preliminary structural work done by Jack Williams and Peter Rudolph at Mdng, and is encoded in a FORTRAN program. As a stand-alone application, the program can calculate the weight CG location, and several types of structural deflections; used in conjunction with an aerodynamics model, the program can be used for mission analysis or sizing studies.
    Keywords: Aerodynamics
    Type: NASA-CR-202164 , NAS 1.26:202164
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  • 3
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    A supercritical airfoil experiment (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The purpose of this investigation is to provide a comprehensive data base for the validation of numerical simulations. The objective of the present paper is to provide a tabulation of the experimental data. The data were obtained in the two-dimensional, transonic flowfield surrounding a supercritical airfoil. A variety of flows were studied in which the boundary layer at the trailing edge of the model was either attached or separated. Unsteady flows were avoided by controlling the Mach number and angle of attack. Surface pressures were measured on both the model and wind tunnel walls, and the flowfield surrounding the model was documented using a laser Doppler velocimeter (LDV). Although wall interference could not be completely eliminated, its effect was minimized by employing the following techniques. Sidewall boundary layers were reduced by aspiration, and upper and lower walls were contoured to accommodate the flow around the model and the boundary-layer growth on the tunnel walls. A data base with minimal interference from a tunnel with solid walls provides an ideal basis for evaluating the development of codes for the transonic speed range because the codes can include the wall boundary conditions more precisely than interference connections can be made to the data sets.
    Keywords: Aerodynamics
    Type: OTN-035236 , OTN-BIBL-AGARD-AR-303-Vol-2
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  • 4
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    Progress in Grid Generation: From Chimera to DRAGON Grids (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Hybrid grids, composed of structured and unstructured grids, combines the best features of both. The chimera method is a major stepstone toward a hybrid grid from which the present approach is evolved. The chimera grid composes a set of overlapped structured grids which are independently generated and body-fitted, yielding a high quality grid readily accessible for efficient solution schemes. The chimera method has been shown to be efficient to generate a grid about complex geometries and has been demonstrated to deliver accurate aerodynamic prediction of complex flows. While its geometrical flexibility is attractive, interpolation of data in the overlapped regions - which in today's practice in 3D is done in a nonconservative fashion, is not. In the present paper we propose a hybrid grid scheme that maximizes the advantages of the chimera scheme and adapts the strengths of the unstructured grid while at the same time keeps its weaknesses minimal. Like the chimera method, we first divide up the physical domain by a set of structured body-fitted grids which are separately generated and overlaid throughout a complex configuration. To eliminate any pure data manipulation which does not necessarily follow governing equations, we use non-structured grids only to directly replace the region of the arbitrarily overlapped grids. This new adaptation to the chimera thinking is coined the DRAGON grid. The nonstructured grid region sandwiched between the structured grids is limited in size, resulting in only a small increase in memory and computational effort. The DRAGON method has three important advantages: (1) preserving strengths of the chimera grid; (2) eliminating difficulties sometimes encountered in the chimera scheme, such as the orphan points and bad quality of interpolation stencils; and (3) making grid communication in a fully conservative and consistent manner insofar as the governing equations are concerned. To demonstrate its use, the governing equations are discretized using the newly proposed flux scheme, AUSM+, which will be briefly described herein. Numerical tests on representative 2D inviscid flows are given for demonstration. Finally, extension to 3D is underway, only paced by the availability of the 3D unstructured grid generator.
    Keywords: Aerodynamics
    Type: NASA-TM-106709 , NAS 1.15:106709 , ICOMP-94-19 , E-9071
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  • 5
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    Validation of the RPLUS3D Code for Supersonic Inlet Applications Involving Three-Dimensional Shock Wave-Boundary Layer Interactions (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A three-dimensional computational fluid dynamics code, RPLUS3D, which was developed for the reactive propulsive flows of ramjets and scramjets, was validated for glancing shock wave-boundary layer interactions. Both laminar and turbulent flows were studied. A supersonic flow over a wedge mounted on a flat plate was numerically simulated. For the laminar case, the static pressure distribution, velocity vectors, and particle traces on the flat plate were obtained. For turbulent flow, both the Baldwin-Lomax and Chien two-equation turbulent models were used. The static pressure distributions, pitot pressure, and yaw angle profiles were computed. In addition, the velocity vectors and particle traces on the flat plate were also obtained from the computed solution. Overall, the computed results for both laminar and turbulent cases compared very well with the experimentally obtained data.
    Keywords: Aerodynamics
    Type: NASA-TM-106579 , E-8839 , NAS 1.15:106579
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  • 6
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    Effect of leading- and trailing-edge flaps on clipped delta wings with and without wing camber at supersonic speeds (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation of the aerodynamic characteristics of thin, moderately swept fighter wings has been conducted to evaluate the effect of camber and twist on the effectiveness of leading- and trailing-edge flaps at supersonic speeds in the Langley Unitary Plan Wind Tunnel. The study geometry consisted of a generic fuselage with camber typical of advanced fighter designs without inlets, canopy, or vertical tail. The model was tested with two wing configurations an uncambered (flat) wing and a cambered and twisted wing. Each wing had an identical clipped delta planform with an inboard leading edge swept back 65 deg and an outboard leading edge swept back 50 deg. The trailing edge was swept forward 25 deg. The leading-edge flaps were deflected 4 deg to 15 deg, and the trailing-edge flaps were deflected from -30 deg to 10 deg. Longitudinal force and moment data were obtained at Mach numbers of 1.60, 1.80, 2.00, and 2.16 for an angle-of-attack range 4 deg to 20 deg at a Reynolds number of 2.16 x 10(exp 6) per foot and for an angle-of-attack range 4 deg to 20 deg at a Reynolds number of 2.0 x 10(exp 6) per foot. Vapor screen, tuft, and oil flow visualization data are also included.
    Keywords: Aerodynamics
    Type: NASA-TM-4542 , L-17272 , NAS 1.15:4542
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  • 7
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    The NASA Langley 8-foot Transonic Pressure Tunnel calibration (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The NASA Langley 8-Foot Transonic Pressure Tunnel is a continuous-flow, variable-pressure wind tunnel with control capability to independently vary Mach number, stagnation pressure, stagnation temperature, and humidity. The top and bottom walls of the test section are axially slotted to permit continuous variation of the test section Mach number from 0.2 to 1.2, the slot-width contour provides a gradient-free test section 50 in. long for Mach numbers equal to or greater than 1.0 and 100 in. long for Mach numbers less than 1.0. The stagnation pressure may be varied from 0.25 to 2.0 atm. The tunnel test section has been recalibrated to determine the relationship between the free-stream Mach number and the test chamber reference Mach number. The hardware was the same as that of an earlier calibration in 1972 but the pressure measurement instrumentation available for the recalibration was about an order of magnitude more precise. The principal result of the recalibration was a slightly different schedule of reentry flap settings for Mach numbers from 0.80 to 1.05 than that determined during the 1972 calibration. Detailed tunnel contraction geometry, test section geometry, and limited test section wall boundary layer data are presented.
    Keywords: Aerodynamics
    Type: NASA-TP-3437 , L-17322 , NAS 1.60:3437
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  • 8
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    Navier-Stokes Calculations For a Venus Composition Probe With Ablation And Wake Radiation (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: A numerical investigation is carried out to determine the magnitude of wake radiation for a proposed Venus composition probe. One of the scientific goals of the mission is to determine the atmospheric composition of Venus by examining the intensity of scattered sunlight through the wake of the vehicle during planetary entry. In the wake of the vehicle, excited particles generated in the bow shock and boundary layers absorb and emit radiation. Thus, the purpose of this study is to determine if the radiation sensor will be able to sense the incoming solar radiative flux relative to the radiative flux generated in the wake. During portions of the entry trajectory the incident surface heat flux will be high enough to produce significant ablation. Ablation products such as CN are known to be strong radiators. Also, the ablation will be driven by strong radiation emanating from the bow shock. Thus, radiation and ablation will be coupled into the Navier-Stokes flow solutions.
    Keywords: Aerodynamics
    Type: AIAA 29th Thermophysics Conference; Jun 19, 1995 - Jun 22, 1995; San Diego, CA; United States
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  • 9
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    Quiet Supersonic Wind Tunnel Development (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: The ability to control the extent of laminar flow on swept wings at supersonic speeds may be a critical element in developing the enabling technology for a High Speed Civil Transport (HSCT). Laminar boundary layers are less resistive to forward flight than their turbulent counterparts, thus the farther downstream that transition from laminar to turbulent flow in the wing boundary layer is extended can be of significant economic impact. Due to the complex processes involved experimental studies of boundary layer stability and transition are needed, and these are performed in "quiet" wind tunnels capable of simulating the low-disturbance environment of free flight. At Ames, a wind tunnel has been built to operate at flow conditions which match those of the HSCT laminar flow flight demonstration 'aircraft, the F-16XL, i.e. at a Mach number of 1.6 and a Reynolds number range of 1 to 3 million per foot. This will allow detailed studies of the attachment line and crossflow on the leading edge area of the highly swept wing. Also, use of suction as a means of control of transition due to crossflow and attachment line instabilities can be studied. Topics covered include: test operating conditions required; design requirements to efficiently make use of the existing infrastructure; development of an injector drive system using a small pilot facility; plenum chamber design; use of computational tools for tunnel and model design; and early operational results.
    Keywords: Aerodynamics
    Type: Aerospace Ground Test Facilities and Flight Testing XXIX Short Course; Apr 25, 1994 - May 05, 1994; Tullahoma, TN; United States
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  • 10
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    Wind Tunnel Testing for the Stratospheric Observatory for Infrared Astronomy (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: NASA Ames Research Center is pursuing the development of SOFIA, the Stratospheric Observatory For Infrared Astronomy. SOFIA will consist of a 2.5 meter telescope mounted aft of the wing of a Boeing 747 aircraft. Since a large portion of the infrared spectrum is not visible at ground level due to absorption by water vapor in the atmosphere below 40,000 feet, it is highly desirable to make observations above this altitude. SOFIA will provide the opportunity for astronomers to conduct high-altitude research for extended periods of time. Current study is focused on wind tunnel testing for the open cavity. If not controlled, air would create resonance and damage the telescope. For this reason, SOFIA will design a boundary layer control device to achieve laminar flow over the cavity. This also provides a clearer flow for seeing, thus improving resolution on infrared sources. Other effects being tested in the wind tunnel are aerodynamic torque loads on the telescope, and flutter loads on the tail.
    Keywords: Aerodynamics
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  • 11
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    Separated and Recovering Turbulent Boundary Layer Flow Behind a Backward Facing Step For Different Reynolds Numbers (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Experimental results for a two-dimensional separated turbulent boundary layer behind a backward facing step for five different Reynolds numbers are reported. Results are presented in the form of tables, graphs and a floppy disk for an easy access of the data. Reynolds number based on the step height was varied by changing the reference velocity upstream of the step, U(sub o), and the step height, h. Hot-wire measurement techniques were used to measure three Reynolds stresses and four triple-velocity correlations. In addition, surface pressure and skin friction coefficients were measured. All hot-wire measurements were acquired in a measuring domain which excluded recirculating flow region due to the directional insensitivity of hot-wires. The downstream extent of the domain from the step was 51 h for the largest and I 14h for the smallest step height. This significant downstream length permitted extensive study of the flow recovery. Prediction of perturbed flows and their recovery is particularly attractive for popular turbulence models since variations of turbulence length and time scales and flow interactions in different regions are generally inadequately predicted. The data indicate that the flow in the free shear layer region behaves like the plane mixing layer up to about 2/3 of the mean reattachment length when the flow interaction with the wall commences the flow recovery to that of an ordinary turbulent boundary layer structure. These changes of the flow do not occur abruptly with the change of boundary conditions. A reattachment region represents a transitional region where the flow undergoes the most dramatic adjustments to the new boundary conditions. Large eddies, created in the upstream free-shear layer region, are being torn, recirculated, reentrained back into the main stream interacting with the incoming flow structure. It is foreseeable that it is quite difficult to describe the physics of this region in a rational and quantitative manner other than statistical. Downstream of the reattachment point the flow recovers at different rates near the wall, in the newly developing internal boundary layer, and in the outer part of the flow. It appears that Reynolds stresses do not fully recover up to the longest recovery length of 114 h.
    Keywords: Aerodynamics
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  • 12
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    Analysis of F/A-18 Tail Buffet Data Acquired in the 80- by 120-Foot Wind Tunnel (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Tail buffet studies were conducted on a full-scale, production, F/A-18 fighter aircraft in the 80- by 120-Foot Wind Tunnel of the National Full-Scale Aerodynamic Complex at NASA Ames Research Center at Moffett Field, California. Tail buffet data were acquired over an angle-of-attack range of +20 deg to +40 deg, a side-slip range of -16 deg to + 16 deg, and at wind speeds up to 100 knots. The maximum speed corresponds to a Reynolds number of l2.3 x l0(exp 6) based on mean aerodynamic chord and a Mach number of 0. 15. The port, vertical tail fin was instrumented with ninety-six surface-pressure transducers, arranged in six by eight arrays, on each side of the fin. ne aircraft was also equipped with a removable Leading-Edge Extension (LEX) fence whose purpose is to reduce tail-buffet loads. Current analysis methods for the unsteady aerodynamic pressures and loads are described. Only results for the zero side-slip condition are to be presented, both with and without the LEX fence. Results of the time-averaged, power-spectral analysis are presented for the tail fin bending moments which are derived from the integrated pressure field. Local wave velocities on the tail surfaces are calculated from pressure correlations. It was found that the LEX fence significantly reduces the magnitude of the root-mean-square pressures and bending moments. Scaling and repeatability issues are addressed by comparing the present full scale results for pressures at the 60%-span and 45%-chord location with previous full-scale F/A-18 tail-buffet test in the 80- by 120- Foot Wind Tunnel, and with several small-scale tests. The comparisons show that the tail buffet frequency scales very well with tail chord and free-stream velocity, and that there is good agreement with the previous full-scale test. Root-mean-square pressures and power spectra do not scale as well as the frequency results. Addition of a LEX fence caused tail-buffet loads to be reduced at all model scales.
    Keywords: Aerodynamics
    Type: SAE Aerospace Atlantic Conference; Apr 18, 1994 - Apr 22, 1994; Dayton, OH; United States
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  • 13
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    Investigation of a Laminar Flow Leading Edge (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: The recent resurgence of interest in utilizing laminar flow on aircraft surfaces for reduction in skin friction drag has generated a considerable amount of research in natural laminar flow (NLF) and hybrid laminar flow control (HLFC) on transonic aircraft wings. This research has focused primarily on airfoil design and understanding transition behavior with little concern for the surface imperfections and manufacturing variations inherent to most production aircraft. In order for laminar flow to find wide-spread use on production aircraft, techniques for constructing the wings must be found such that the large surface imperfections present in the leading edge region of current aircraft do not occur. Toward this end, a modification to existing leading edge construction techniques was devised such that the resulting surface did not contain large gaps and steps as are common on current production aircraft of this class. A lowspeed experiment was first conducted on a simulation of the surface that would result from this construction technique. Preston tube measurements of the boundary layer downstream of the simulated joint and flow visualization using sublimation chemicals validated the literature on the effects of steps on a laminar boundary layer. These results also indicated that the construction technique was indeed compatible with laminar flow. In order to fully validate the compatibility of this construction technique with laminar flow, thus proving that it is possible to build wings that are smooth enough to be used on business jets and light transports in a manner compatible with laminar flow, a flight experiment is being conducted. In this experiment Mach number and Reynolds number will be matched in a real flight environment. The experiment is being conducted using the NASA Dryden F-104 Flight Test Fixture (FTF). The FTF is a low aspect ratio ventral fin mounted beneath an F-104G research aircraft. A new nose shape was designed and constructed for this experiment. This nose shape provides an accelerating pressure gradient in the leading edge region. By flying the aircraft at appropriate Mach numbers and altitudes, this nose shape simulates the leading edge region of a laminar flow wing for a business jet or light transport. Manufactured into the nose shape is a spanwise slot located approximately four inches downstream of the leading edge. The slot, which is an inch wide and one-eighth of an inch deep allows the simulation of surface imperfections, such as gaps and steps at skin joints, which will occur on aircraft using this new construction technique. By placing strips of aluminum of various sizes and shapes in the slot, the effect on the boundary layer of different sizes and shapes of steps and gaps will be examined. It is planned to use five different configurations, differing primarily in the size and number of gaps. Downstream of the slot, the state of the boundary layer is determined using hot film gages and Stanton gages. Agreement between these two very different techniques of measuring boundary layer properties is considered important to being able to state with confidence the effects on the boundary layer of the simulated manufacturing imperfections. To date, the aircraft has not flown. First flights of the aircraft are on schedule to begin October 4, 1993. Low-speed, preliminary experiments at matching Reynolds numbers have been completed.
    Keywords: Aerodynamics
    Type: AIAA 6th Biennial Flight Test Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
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  • 14
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    Adaptive Wing Camber Optimization: A Periodic Perturbation Approach (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Available redundancy among aircraft control surfaces allows for effective wing camber modifications. As shown in the past, this fact can be used to improve aircraft performance. To date, however, algorithm developments for in-flight camber optimization have been limited. This paper presents a perturbational approach for cruise optimization through in-flight camber adaptation. The method uses, as a performance index, an indirect measurement of the instantaneous net thrust. As such, the actual performance improvement comes from the integrated effects of airframe and engine. The algorithm, whose design and robustness properties are discussed, is demonstrated on the NASA Dryden B-720 flight simulator.
    Keywords: Aerodynamics
    Type: H-1998 , Automatic Control in Aerospace; 35-40|Aerospace Control; Sep 12, 1994 - Sep 16, 1994; Palo Alto, CA; United States
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  • 15
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    Unsteady Aerodynamic Behavior Measured in Hovering Flight (1994)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: A highly-instrumented UH-60A aircraft was tested at NASA-Ames Research Center from August 1993 to February 1994 obtaining an extensive data base for level flight, maneuvers, acoustics (both with respect to ground microphone arrays and inflight microphones), and flight dynamics. A majority of the data obtained are now in an electronic data base, however, only a small fraction of the data have been examined. The proposed paper will examine the issue of hovering steadiness in more detail. In particular, a single set of data obtained during ground acoustic testing may provide considerable insight as the wind speeds were measured at a hover height of 250 feet and the aircraft was positioned in 15 deg. steps in heading from 0 to 180 deg. Also, hover housekeeping data were obtained for many of the 31 flights and these will also allow a characterization of the unsteadiness. The variation in section lift will be examined in terms of the induced flow angle variation and this will be related to possible physical explanations.
    Keywords: Aerodynamics
    Type: AHS 51st Annual Forum and Technology Display; May 09, 1995 - May 11, 1995; Fort Worth, TX; United States
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  • 16
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    An Assessment of the Effect of Compressibility on Dynamic Stall (1994)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Compressibility plays a significant role in the development of separation on airfoils experiencing unsteady motion, even at moderately compressible free-stream flow velocities. This effect can result in completely changed stall characteristics compared to those observed at incompressible speed, and can dramatically affect techniques used to control separation. There has been a significant effort in recent years directed toward better understanding; of this process, and its impact on possible techniques for control of separation in this complex environment. A review of existing research in this area will be presented, with emphasis on the physical mechanisms that play such an important role in the development of separation on airfoils. The increasing impact of compressibility on the stall process will be discussed as a function of free-stream Mach number, and an analysis of the changing flow physics will be presented. Examples of the effect of compressibility on dynamic stall will be selected from both recent and historical efforts by members of the aerospace community, as well as from the ongoing research program of the present authors. This will include a presentation of a sample of high speed filming of compressible dynamic stall which has recently been created using real-time interferometry.
    Keywords: Aerodynamics
    Type: 33rd AIAA Aerospace Sciences Meeting; Jan 09, 1995 - Jan 12, 1995; Reno, NV; United States
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  • 17
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    Hypersonic Research Program at NASA Ames Research Center (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: This paper will describe the Airbreathing Hypersonic Research Program at NASA Ames Research Center. A main theme will be the "From Computation Through Flight" research effort. General research areas covered will include systems analysis, aerodynamics and aerothermodynamics, propulsion, materials, and flight research. Illustrative results from each discipline will be presented. The synergism between computational and experimental research will be demonstrated by examples. All examples given will have been published in the open literature.
    Keywords: Aerodynamics
    Type: AIAA Atmospheric Flight Mechanics Conference; Aug 01, 1994 - Aug 03, 1994; Scottsdale, AZ; United States
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  • 18
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    Aerodynamics Characteristics of Multi-Element Airfoils at -90 Degrees Incidence (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: A developed method has been applied to calculate accurately the viscous flow about airfoils normal to the free-stream flow. This method has special application to the analysis of tilt rotor aircraft in the evaluation of download. In particular, the flow about an XV-15 airfoil with and without deflected leading and trailing edge flaps at -90 degrees incidence is evaluated. The multi-element aspect of the method provides for the evaluation of slotted flap configurations which may lead to decreased drag. The method solves for turbulent flow at flight Reynolds numbers. The flow about the XV-15 airfoil with and without flap deflections has been calculated and compared with experimental data at a Reynolds number of one million. The comparison between the calculated and measured pressure distributions are very good, thereby, verifying the method. The aerodynamic evaluation of multielement airfoils will be conducted to determine airfoil/flap configurations for reduced airfoil drag. Comparisons between the calculated lift, drag and pitching moment on the airfoil and the airfoil surface pressure will also be presented.
    Keywords: Aerodynamics
    Type: AIAA Aerospace Sciences; Jan 09, 1995 - Jan 12, 1995; Reno, NV; United States
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  • 19
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    Navier-Stokes Flowfield Simulation of Boeing 747-200 as Platform for SOFIA (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Steady and unsteady viscous, three-dimensional flowfields are calculated using a thin layer approximation of Navier-Stokes equations in conjunction with Chimera overset grids. The finite-difference numerical scheme uses structured grids and a pentadiagonal flow solver called "OVERFLOW". The configuration of Boeing 747-200 has been chosen as one of configurations to be used as a platform for the SOFIA (Stratospheric Observatory For Infrared Astronomy). Initially, the steady flowfield of the full aircraft is calculated for the clean configuration (without a cavity to house telescope). This solution is then used to start the unsteady flowfield of a configuration containing cavity housing the observation telescope and its peripheral units. Analysis of unsteady flowfield in the cavity and its influence on the tail empennage, as well as the noise due to turbulence and optical quality of the flow are the main focus of this study. For the configuration considered here, the telescope housing cavity is located slightly downstream of the portwing. The entire flow-field is carefully constructed using 45 overset grids and consists of nearly 4 million grid points. All the computations axe done at one freestream flow condition of M(sub infinity) = 0.85, alpha = 2.5deg, and a Reynolds of Re = 1.85x10deg
    Keywords: Aerodynamics
    Type: AIAA Aerspace Sciences; Jan 02, 1995 - Jan 12, 1995; Reno, NV; United States
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  • 20
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    Wind Tunnel Visualization of the Flow Over a Full-Scale F/A-18 Aircraft (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: The proposed paper presents flow visualization performed during experiments conducted on a full-scale F/A-18 aircraft in the 80- by 120-Foot Wind-Tunnel at NASA Ames Research Center. This investigation used both surface and off-surface flow visualization techniques to examine the flow field on the forebody, canopy, leading edge extensions (LEXs), and wings. The various techniques used to visualize the flow field were fluorescent tufts, flow cones treated with reflective material, smoke in combination with a laser light sheet, and a video imaging system. The flow visualization experiments were conducted over an angle of attack range from 20deg to 45deg and over a sideslip range from -10deg to 10deg. The results show regions of attached and separated flow on the forebody, canopy, and wings. Additionally, the vortical flow is clearly visible over the leading-edge extensions, canopy, and wings.
    Keywords: Aerodynamics
    Type: SAE Aerospace Atlantic Conference; Apr 18, 1994 - Apr 22, 1994; Dayton, OH; United States
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  • 21
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    Comment on 'Guidance for an Aerocapture Maneuver (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: It is stated that the aerodynamic forces on the vehicle being aerocaptured are controlled by "altering the angle of attack" and thereby controlling the lift coefficient. Furthermore, the resulting variation of drag coefficient with angle of attack was ignored. The purpose of this Comment is to point out that an aerodynamic control method that is much more effective than the pitch modulation has been studied and utilized during entries for many years. During aerocapture, it is desirable to have a large range of lift coefficients available, while keeping the vehicle's ballistic coefficients constant. This is accomplished by modulating the vehicle's bank angle, i.e., by rolling the vehicle about its velocity vector. By this method, the angle of attack can be held constant (at the trim angle, if desired), and the C(sub D) and the ballistic coefficient remain constant. Furthermore, the vertical component of the normal force vector (essentially the lift) can be varied over its entire range, from maximum positive to maximum negative values. Reaction controls, rather than aerodynamic ones, are usually utilized to change the bank angle of the vehicle, thus requiring the use of fuel. However, the fuel expenditure that is required to change the bank angle is far less than the amount that would have to be used to continuously hold the vehicle at pitch angles that differ significantly from its trim angle of attack. Also, it has been shown that bank angle modulation to vary the lift can enlarge the entry corridor by increasing the entry angle for the undershoot boundary, where both the heating rate and deceleration reach a maximum. Finally, the crew's deceleration tolerance can be increased somewhat when the bank angle is varied, as opposed to the pitch angle. For bank modulation, the deceleration force vector can be kept at a constant angle with respect to the occupants whose tolerance to g loads is highest when the force is applied in a direction normal to the upper torso. The advantages of bank angle variation to modulate the lift vector were recognized long ago, and this method of control was used successfully on the Apollo command module during lunar return' and, more recently, for the Space Shuttle Orbiter.
    Keywords: Aerodynamics
    Type: Journal of Guidance, Control, and Dynamics; 17; 4; 878-878
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  • 22
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    Experimental and Computational Study of Sonic and Supersonic Jet Plumes (1994)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Study of sonic and supersonic jet plumes are relevant to understanding such phenomenon as jet-noise, plume signatures, and rocket base-heating and radiation. Jet plumes are simple to simulate and yet, have complex flow structures such as Mach disks, triple points, shear-layers, barrel shocks, shock-shear-layer interaction, etc. Experimental and computational simulation of sonic and supersonic jet plumes have been performed for under- and over-expanded, axisymmetric plume conditions. The computational simulation compare very well with the experimental observations of schlieren pictures. Experimental data such as temperature measurements with hot-wire probes are yet to be measured and will be compared with computed values. Extensive analysis of the computational simulations presents a clear picture of how the complex flow structure develops and the conditions under which self-similar flow structures evolve. From the computations, the plume structure can be further classified into many sub-groups. In the proposed paper, detail results from the experimental and computational simulations for single, axisymmetric, under- and over-expanded, sonic and supersonic plumes will be compared and the fluid dynamic aspects of flow structures will be discussed.
    Keywords: Aerodynamics
    Type: AIAA Atmospheric Flight Mechanics Conference; Aug 07, 1995 - Aug 09, 1995; Baltimore, MD; United States
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  • 23
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    The Effect of Two-Dimensional Forcing on Self-Similar Turbulent Plane Wakes (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Three direct numerical simulations of time-evolving turbulent plane wakes with velocity deficit Reynolds numbers of about 2,000 have been simulated using a spectral numerical method with up to 600 x 260 x 160 modes. The initial conditions for the simulations are generated from direct numerical simulations of a turbulent boundary layer (momentum thickness Reynolds number of 670), and varying amounts of additional two- dimensional, forcing. In order to preserve the self-similar flow evolution, the forcing is implemented by multiplying all the two-dimensional modes in the initial condition by a constant factor. In the "natural" case no additional forcing is used; in the "forced" and "heavily forced" cases this factor is 5 and 20, respectively. The wake spreading rate Is increased by factors of 1.7 and 7.1 for the two forced cases. The Reynolds stresses are also increased by a similar or even larger factor. These results indicate that the plane wake is much more sensitive to initial forcing than the plane mixing layer. As in the plane mixing layer, two-dimensional forcing promotes more organized large-scale vortical flow structures and these structures axe sometimes separated by "braid regions" containing streamwise "rib" vortices, unlike in the unforced wake.
    Keywords: Aerodynamics
    Type: Forty-Seventh Annual Meeting of the American Physical Society; Nov 20, 1994 - Nov 22, 1994; Atlanta, GA; United States
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  • 24
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    On the Two-Dimensionalization of Homogeneous Rotating Turbulence (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Large-eddy simulation of the incompressible Navier-Stokes equations has been used to examine the long-time development of initially isotropic turbulence subjected to solid-body rotation. The simulations were carried out using a pseudo-spectral method with 128 x 128 x 512 collocation points in a computational domain that is four times larger along the rotation axis than in the other directions; subgrid-scale motions were parameterized using a spectral eddy viscosity model modified for system rotation. Simulation results show that the correlation length along the rotation am's of velocities orthogonal to the rotation vector exhibits rapid growth while the integral length-scale of velocities aligned with the rotation axis is relatively unaffected by rotation. Examination of the energy spectrum of two-dimensional, two-component motions indicates the presence of an inverse cascade of energy. System rotation also causes an alignment of vorticity along the rotation axis with relatively stronger cyclonic vorticity than anticyclonic. The onset of anisotropic effects are well characterized by Rossby numbers defined in terms of both macroscopic and microscopic quantities.
    Keywords: Aerodynamics
    Type: Forty-Seventh Annual Meeting of the American Physical Society; Nov 20, 1994 - Nov 22, 1994; Atlanta, GA; United States
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  • 25
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    Navier-Stokes Solutions of Rotor and Rotor-Body Flows (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: This paper will review the advances made recently in the Navier-Stokes CFD methods to simulate aerodynamics and aeroacoustics of helicopter rotors and rotor-body flows. Although a complete flowfield simulation of full helicopter is currently not feasible with these methods, impressive gains have been made in analyzing individual components of this complex problem in a very detailed manner. The use of the state-of-the-art numerical algorithms in solution methods, in conjunction with powerful supercomputers, like the Cray-2, have enabled noticeable progress to be made in modeling viscous-inviscid interactions, blade-vortex interactions, tip-vortex: simulation and wake effects, as well as high speed impulsive noise in hover and forward flight for isolated rotor blades. This paper will critically evaluate the presently available Euler and Navier-Stokes methods, both finite-difference and finite volume methods using structured and unstructured grids for helicopter applications for accuracy, suitability, and computational efficiency. The review will also include the recent progress made using overset grids to model rotor-body flows. All the material for this review will be drawn from the published material shown below.
    Keywords: Aerodynamics
    Type: International Colloquium on Vortical Flows in the Aeronautics; Oct 12, 1994 - Oct 14, 1994; Aachan; Germany
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  • 26
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    Wing-Body Aeroelasticity Using Finite-Difference Fluid/Finite-Element Structural Equations on Parallel Computers (1994)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: In recent years significant advances have been made for parallel computers in both hardware and software. Now parallel computers have become viable tools in computational mechanics. Many application codes developed on conventional computers have been modified to benefit from parallel computers. Significant speedups in some areas have been achieved by parallel computations. For single-discipline use of both fluid dynamics and structural dynamics, computations have been made on wing-body configurations using parallel computers. However, only a limited amount of work has been completed in combining these two disciplines for multidisciplinary applications. The prime reason is the increased level of complication associated with a multidisciplinary approach. In this work, procedures to compute aeroelasticity on parallel computers using direct coupling of fluid and structural equations will be investigated for wing-body configurations. The parallel computer selected for computations is an Intel iPSC/860 computer which is a distributed-memory, multiple-instruction, multiple data (MIMD) computer with 128 processors. In this study, the computational efficiency issues of parallel integration of both fluid and structural equations will be investigated in detail. The fluid and structural domains will be modeled using finite-difference and finite-element approaches, respectively. Results from the parallel computer will be compared with those from the conventional computers using a single processor. This study will provide an efficient computational tool for the aeroelastic analysis of wing-body structures on MIMD type parallel computers.
    Keywords: Aerodynamics
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  • 27
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    Cluster Computation of Flight Reynolds Number Flows (1994)
    In:  Other Sources
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    Publication Date: 2019-08-13
    Description: The performance of a workstation cluster used for the solution of the Reynolds-averaged Navier-Stokes equations is compared with a conventional vector supercomputer architecture. The application simulation of the steady flowfield about a transonic transport was computed using an implicit diagonal scheme in an overset mesh framework. Static load balancing was used, while coarse grain decomposition was achieved by solution of a grid zone per processor. Price/performance ratios are estimated for several scenarios in which such clusters may be utilized.
    Keywords: Aerodynamics
    Type: OAI/NASA Symposium Application of Parallel and Distributed Computing; Apr 18, 1994 - Apr 19, 1994; Columbus, OH; United States
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  • 28
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    Off-Axis Drag of Dendrite Fragments at Low Reynolds Number (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The aim of the present investigation is to characterize the motion of dendrite fragments falling under the influence of gravity in a uniform liquid medium at low Reynolds number. In an earlier study, Zakhem, Weidman and de Groh (1992) reported on the settling speed of model equiaxed dendrite grains released along their axis of symmetry. In this follow-up study uniaxial model dendrite grains were released off-axis to observe and document their motion at different orientations. It was hypothesized that the dendrite models might rotate when released off-axis in which case an attempt would be made to document the ensuing unsteady motion. This latter event turned out to be in fact true: at the small but finite Reynolds numbers that existed, each uniaxial dendrite slowly rotated towards its equilibrium orientation while failing under the influence of gravity. In addition to completing the original goal, we have made use of a beads-on-a shell Stokes flow code to numerically determine the drag coefficient for capsules, i.e.. uniaxial dendrites without arms. The drag on horizontally and vertically falling capsules are reported and compared with measurements.
    Keywords: Aerodynamics
    Type: NASA/CR-94-207107 , NAS 1.26:207107
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  • 29
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    Investigation of supersonic jet plumes using an improved two-equation turbulence model (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Supersonic jet plumes were studied using a two-equation turbulence model employing corrections for compressible dissipation and pressure-dilatation. A space-marching procedure based on an upwind numerical scheme was used to solve the governing equations and turbulence transport equations. The computed results indicate that two-equation models employing corrections for compressible dissipation and pressure-dilatation yield improved agreement with the experimental data. In addition, the numerical study demonstrates that the computed results are sensitive to the effect of grid refinement and insensitive to the type of velocity profiles used at the inflow boundary for the cases considered in the present study.
    Keywords: Aerodynamics
    Type: NASA-TM-111555 , NAS 1.15:111555 , AIAA Paper 92-2604 , Applied Aerodynamics Conference; Jun 22, 1992 - Jun 24, 1992; Palo Alto, CA; United States
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  • 30
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    Viscous Shock-Layer Analysis of Two-Dimensional and Axisymmetric Flows (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Results are obtained for cylindrical leading edges of proposed transatmospheric vehicles by employing a two-dimensional viscous shock-layer code for nonequilibrium gas flows. The accuracy and efficiency of the planar code is verified through detailed comparisons with other predictions. This study includes results for 6-deg half-angle bodies with nose radii ranging from 0.01 to 2.0 ft for both cylindrically blunted wedges and spherically blunted cones (included for comparison). Some results are presented as a ratio of the noncatalytic to the corresponding fully catalytic heating value to illustrate the maximum potential for a heating reduction in dissociated nonequilibrium flows. Generally, this ratio and the individual heating rates are smaller for cylindrically blunted wedges with small nose radii as compared to the spherically blunted cones (for the same nose radius). Therefore, a larger potential exists for heating reduction in cylindrically blunted as compared with the spherically blunted surfaces. However, the results presented at higher altitudes (where the slip effects become important) show that the spherically, blunted nose gives lower stagnation-point heating due to stronger merged shock-layer effects as compared with a cylindrically blunted nose.
    Keywords: Aerodynamics
    Type: NASA-TM-111564 , NAS 1.15:111564 , AIAA Paper 93-2751 , Thermophysics Conference; Jul 06, 1993 - Jul 09, 1993; Orlando, FL; United States
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  • 31
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    Navier-Stokes prediction of large-amplitude forced and free-to-roll delta-wing oscillations (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The three-dimensional Reynolds-averaged, Navier-Stokes (RANS) equations are used to numerically simulate nonsteady vortical flow about a 65 degree sweep delta wing at 30 degrees angle of attack. Two large-amplitude, high-rate, forced-roll motions and a damped free-to-roll motion are presented. The free-to-roll motion is computed by coupling the time-dependent RANS equations to the flight dynamic equation of motion. The computed results are compared with experimental forces, moments, and roll-angle time histories. The overall agreement is good. Vortex breakdown is present in each case, which causes significant time lags in the vortex breakdown motions relative to the body motions. This behavior strongly influences the dynamic forces and moments.
    Keywords: Aerodynamics
    Type: NASA-TM-111611 , NAS 1.15:111611 , AIAA Paper 94-1884 , AIAA Applied Aerodynamics Conference; Jun 20, 1994 - Jun 22, 1994; Colorado Springs, CO; United States
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  • 32
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    Validation of Vortex-Lattice Method for loads on wings in lift-generated wakes (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A study is described that evaluates the accuracy of vortex-lattice methods when they are used to compute the loads induced on aircraft as they encounter lift-generated wakes. The evaluation is accomplished by use of measurements made in the 80- by 120-foot wind tunnel of the lift, rolling-moment, and downwash in the wake of three configurations of a model of a subsonic transport aircraft. The downwash measurements are used as input for a vortex-lattice code in order to compute the lift and rolling moment induced on wings that have a span of 0.186, 0.510, or 1.022 times the span of the wake-generating model. Comparison of the computed results with the measured lift and rolling moment distributions are used to determine the accuracy of the vortex-lattice code. It was found that the vortex-lattice method is very reliable as long as the span of the encountering of following wing is less than about 0.2 of the generator span. As the span of the following wing increases above 0.2, the vortex-lattice method continues to correctly predict the trends and nature of the induced loads, but it overpredicts the magnitude of the loads by increasing amounts. The increase in deviation of the computed from the measured loads with size of the following wing is attributed to the increase in distortion of the structure of the vortex wake as it approaches and passes the larger following wings.
    Keywords: Aerodynamics
    Type: NASA-TM-111610 , NAS 1.15:111610 , AIAA-94-1839 , AIAA Applied Aerodynamics Conference; Jun 20, 1994 - Jun 22, 1994; Colorado Springs, CO; United States
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  • 33
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    Navier-Stokes Calculations for a Highly-Twisted Rotor Near Stall (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The viscous flow field near the surface of a hovering rotor blade was studied for blade twist distributions typical of a till rotor blade and a conventional helicopter rotor blade. Three blade geometries were studied, including a tilt rotor blade twist distribution (baseline), conventional helicopter rotor blade twist distribution, and the baseline twist distribution with 2 deg of precone. The results give insight into the delayed stall phenomenon often observed for highly twisted rotors. Calculations were performed for a high thrust condition near stall using the thin-layer Navier-Stokes CFD code TURNS. Effects of built-in twist on section force coefficients, skin friction, velocities, surface pressures, and boundary layer shape factor are discussed. Although the rotor thrust coefficient was nominally the same for the cases using the two twist distributions, large differences were found in the section in-plane and normal force coefficients. These preliminary results imply that the blade outboard region, rather than the inboard region, provides the majority of the performance advantage of the baseline case over the low twist case. Skin friction, velocities near the blade, and surface pressures for the two twist distributions reveal significant differences in the blade outboard region.
    Keywords: Aerodynamics
    Type: NASA-TM-111741 , NAS 1.15:111741 , Aeromechanics Specialists; Jan 19, 1994 - Jan 21, 1994; San Fransisco, CA; United States
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  • 34
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    A hybrid Navier-Stokes/full-potential method for the prediction of iced wing aerodynamics (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A hybrid method for computing compressible viscous flows is presented. This method divides the computational domain into two zones. In the outer zone, the unsteady full-potential equation (FPE) is solved. In the inner zone, the Navier-Stokes equations are solved. The two zones are tightly coupled so that steady and unsteady flows may be efficiently solved. The resulting CPU times are less than 50 percent of the required for a full-blown Navier-Stokes analysis. Sample applications of the method to an unswept iced wing at 4 deg and 8 deg angle of attack are presented. Surface pressures are in good agreement with the measurements obtained by Bragg et al. at the University of Illinois.
    Keywords: Aerodynamics
    Type: NASA-CR-201432 , NAS 1.26:201432 , AIAA Paper 94-0489 , AIAA Aerospace Sciences Meeting and Exhibit; Jan 10, 1994 - Jan 13, 1994; Reno, NV; United States
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  • 35
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    Static aeroelastic analysis of wings using Euler/Navier-Stokes equations coupled with improved wing-box finite element structures (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Strong interactions between flow about an aircraft wing and the wing structure can result in aeroelastic phenomena which significantly impact aircraft performance. Time-accurate methods for solving the unsteady Navier-Stokes equations have matured to the point where reliable results can be obtained with reasonable computational costs for complex non-linear flows with shock waves, vortices and separations. The ability to combine such a flow solver with a general finite element structural model is key to an aeroelastic analysis in these flows. Earlier work involved time-accurate integration of modal structural models based on plate elements. A finite element model was developed to handle three-dimensional wing boxes, and incorporated into the flow solver without the need for modal analysis. Static condensation is performed on the structural model to reduce the structural degrees of freedom for the aeroelastic analysis. Direct incorporation of the finite element wing-box structural model with the flow solver requires finding adequate methods for transferring aerodynamic pressures to the structural grid and returning deflections to the aerodynamic grid. Several schemes were explored for handling the grid-to-grid transfer of information. The complex, built-up nature of the wing-box complicated this transfer. Aeroelastic calculations for a sample wing in transonic flow comparing various simple transfer schemes are presented and discussed.
    Keywords: Aerodynamics
    Type: NASA-CR-201433 , NAS 1.26:201433 , AIAA Paper 94-1587 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference; Apr 18, 1994 - Apr 20, 1994; Hilton Head, SC; United States
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  • 36
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    Rarefield-Flow Shuttle Aerodynamics Flight Model (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A model of the Shuttle Orbiter rarefied-flow aerodynamic force coefficients has been derived from the ratio of flight acceleration measurements. The in-situ, low-frequency (less than 1Hz), low-level (approximately 1 x 10(exp -6) g) acceleration measurements are made during atmospheric re-entry. The experiment equipment designed and used for this task is the High Resolution Accelerometer Package (HiRAP), one of the sensor packages in the Orbiter Experiments Program. To date, 12 HiRAP re-entry mission data sets spanning a period of about 10 years have been processed. The HiRAP-derived aerodynamics model is described in detail. The model includes normal and axial hypersonic continuum coefficient equations as function of angle of attack, body-flap deflection, and elevon deflection. Normal and axial free molecule flow coefficient equations as a function of angle of attack are also presented, along with flight-derived rarefied-flow transition bridging formulae. Comparisons are made between the aerodynamics model, data from the latest Orbiter Operational Aerodynamic Design Data Book, applicable computer simulations, and wind-tunnel data.
    Keywords: Aerodynamics
    Type: NASA-TM-111566 , NAS 1.15:111566 , AIAA Paper 93-3441 , Applied Aerodynamics Conference; Aug 09, 1993 - Aug 11, 1993; Monterey, CA; United States
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  • 37
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    Analysis of tangential slot blowing on F/A-18 isolated forebody (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Generation of significant side forces and yawing moments on an F/A-18 fuselage through tangential slot blowing is analyzed using computational fluid dynamics. The effects of freestream Mach number, jet exit conditions, jet length, and jet location are studied. The effects of over- and under-blowing on force and moment production are analyzed. Non-time-accurate solutions are obtained to determine the steady-state side forces, yawing moments, and surface pressure distributions generated by tangential slot blowing. Time-accurate solutions are obtained to study the force onset time lag of tangential slot blowing. Comparison with available experimental data from full-scale wind tunnel and sub-scale wind tunnel tests are made. This computational analysis complements the experimental results and provides a detailed understanding of the effects of tangential slot blowing on the flow field about the isolated F/A-18 forebody. Additionally, it extends the slot-blowing database to transonic maneuvering Mach numbers.
    Keywords: Aerodynamics
    Type: NASA-TM-111696 , NAS 1.15:111696 , AIAA Paper 95-1831 , AIAA Applied Aerodynamics Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
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  • 38
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    Measurements of Supersonic Wing Tip Vortices (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: An experimental survey of supersonic wing tip vortices has been conducted at Mach 2.5 using small performed 2.25 chords down-stream of a semi-span rectangular wing at angle of attack of 5 and 10 degrees. The main objective of the experiments was to determine the Mach number, flow angularity and total pressure distribution in the core region of supersonic wing tip vortices. A secondary aim was to demonstrate the feasibility of using cone probes calibrated with a numerical flow solver to measure flow characteristics at supersonic speeds. Results showed that the numerically generated calibration curves can be used for 4-hole cone probes, but were not sufficiently accurate for conventional 5-hole probes due to nose bluntness effects. Combination of 4-hole cone probe measurements with independent pitot pressure measurements indicated a significant Mach number and total pressure deficit in the core regions of supersonic wing tip vortices, combined with an asymmetric 'Burger like' swirl distribution.
    Keywords: Aerodynamics
    Type: NASA-CR-202591 , NAS 1.26:202591 , AIAA Paper 94-2576 , Aerospace Ground Testing; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
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  • 39
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    Severe Turbulence and Maneuvering from Airline Flight Records (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Digital flight records from reported clear-air turbulence incidents are used to determine winds and turbulence, to determine maneuver g loads, and to analyze control problems. Many cases of severe turbulence are found downwind of mountains and thunderstorms where sharp, sudden jolts are associated with vortices in atmospheric waves. Other cases of severe turbulence are round in strong updrafts above thunderstorm buildups that may be undetected by onboard weather radar. An important finding is that there are large maneuvering loads in over half of the reported clear-air turbulence incidents. Maneuvering loads are determined through an analysis of the short-term variations in elevator deflection and aircraft pitch angle. For altitude control in mountain waves the results indicate that small pitch angle changes with proper timing are sufficient to counter variations in vertical wind. For airspeed control in strong mountain waves, however, there is neither the available thrust nor the quickness in engine response necessary to counter the large variations in winds.
    Keywords: Aerodynamics
    Type: NASA-TM-111780 , NAS 1.15:111780 , AIAA Paper 92-4341 , Journal of Aircraft; 31; 4; 753-760|Atmospheric Flight Mechanics; Aug 10, 1992 - Aug 12, 1992; Hilton Head, SC; United States
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  • 40
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    Forebody Tangential Slot Blowing on an Aircraft Geometry (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The effect of forebody tangential slot blowing on the flowfield about an F/A-18 aircraft is investigated numerically using solutions of the Navier-Stokes equations. Computed solutions are obtained for an aircraft geometry which includes the fuselage, a wing with deflected leading-edge flap, empennage, and a faired-over engine inlet. The computational slot geometry corresponds to that used in full-scale wind-tunnel tests. Solutions are computed using flight test conditions and jet mass flow ratios equivalent to wind-tunnel test conditions. The effect of slot location is analyzed by computing two nontime-accurate solutions with a 16-in. slot located 3 in. and 11 in. aft of the nose of the aircraft. These computations resolve the trends observed in the full-scale wind-tunnel test data. The flow aft of the leading-edge extension vortex burst is unsteady. A time-accurate solution is obtained to investigate the flow characteristics aft of the vortex burst, including the effect of blowing on tail buffet.
    Keywords: Aerodynamics
    Type: NASA-TM-111779 , NAS 1.15:111779 , AIAA Paper 93-2962 , Journal of Aircraft; 31; 4; 922-928|Fluid Dynamics, Plasmadynamics, and Lasers Conference; Jul 06, 1993 - Jul 09, 1993; Orlando, Fl; United States
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  • 41
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    An Exploratory Study of a Subspace Iteration Method as an Alternative to the QR Method for Floquet Eigenanalysis (1994)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Floquet eigenanalysis requires a few dominant eigenvalues of the Floquet transition matrix (FTM). Although the QR method is used almost exclusively, it is expensive for such partial eigenanalysis; the operation counts and, thereby, the approximate machine-time grow cubically with the matrix order. Accordingly, for Floquet eigenanalysis, the Arnold-Saad method, a subspace iteration method, is investigated as an alternative to the QR method. The two methods are compared for machine-time efficiency and the residual errors of the corresponding eigenpairs. The Arnolds-Saad method takes much less machine-time than the QR method with comparable computational reliability and offers promise fpr large-scale Floquet eigenanalysis.
    Keywords: Aerodynamics
    Type: NASA-CR-203147 , NAS 1.26:203147 , Mathl. Comput. Modelling (ISSN 0895-7177); 19; 4-Mar; 69-73
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  • 42
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    Application of a Third Order Upwind Scheme to Viscous Flow over Clean and Iced Wings (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A 3-D compressible Navier-Stokes solver has been developed and applied to 3-D viscous flow over clean and iced wings. This method uses a third order accurate finite volume scheme with flux difference splitting to model the inviscid fluxes, and second order accurate symmetric differences to model the viscous terms. The effects of turbulence are modeled using a Kappa-epsilon model. In the vicinity of the sold walls the kappa and epsilon values are modeled using Gorski's algebraic model. Sampling results are presented for surface pressure distributions, for untapered swept clean and iced wings made of NACA 0012 airfoil sections. The leading edge of these sections is modified using a simulated ice shape. Comparisons with experimental data are given.
    Keywords: Aerodynamics
    Type: NASA-CR-202616 , NAS 1.26:202616 , AIAA Paper 94-0485 , Aerospace Sciences; Jan 10, 1994 - Jan 13, 1994; Reno, NV; United States
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    An Experimental Simulation of Flap Flow on Multielement Airfoils at High Reynolds Number (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The design of the high lift system has a major impact on the performance of an aircraft yet our understanding of the physics of this flow is still weak. Flow features include interactions between the wakes shed from the upstream elements and the pressure gradients and boundary layers of the downstream elements. Interaction of the turbulent wake of the main element and the flap can cause (1) separation of the flap boundary layer or (2) 'bursting' of the main airfoil wake. Although the first factor is at least partially understood, even the qualitative aspects of (2) remain to be determined. In order to study these phenomena at Reynolds numbers approaching those of flight, a thick high Reynolds number wake is created using a 24 foot flat plate in the long rectangular test section of a 4 ft. by 6 ft subsonic wind tunnel. The design and construction of this test section, plate, and accompanying flap is described. Results obtained in a quarter-scale model were used for design purposes and are also described. Construction of the full scale facility is complete and preliminary results are presented.
    Keywords: Aerodynamics
    Type: NASA-CR-203019 , NAS 1.26:203019 , AIAA Paper 94-2613 , Aerospace Ground Testing; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
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    A Review of Evidence for High Life Coefficients on Propeller and Rotor Blades Under Static Thrust Conditions with Some New Experimental Results (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Interest has increased recently in the thrust-producing capability of rotors at very high collective pitch angles. An early reference noted this behaviour in rotors and offered alternative models for section lift characteristics to explain it. The same phenomenon was coincidentally noted and used in a propeller code, resulting in very good correlation with static thrust data. The proposed paper will present experimental data demonstrating the pronounced persistence of thrust for propellers at increasing collective pitch angles. Comparisons with blade element/momentum theory will be made. These results are expected to point to the need to define (ultimately to explain) aerodynamic lift and drag behaviour in a rotating environment. Experimental measurements made by the U.S. Army Aeroflightdynamics Directorate at the Ames Research Center have shown that locally measured normal force coefficients along the span of a highly twisted rotor blade continue to increase at high values of collective pitch. In some cases these coefficients exceed expected values for the same type of airfoil tested under two dimensional conditions. To date no one to the authors' knowledge has defined the variation of C(n) with pitch for very high angles (to 45 deg) in a rotating environment and for a blade of reasonably high aspect ratio; however, total propeller thrust measurements support the idea that stalling does not occur in the same way as on a wing. This paper will present experimental data in the form of surface pressure distributions as well as flow visualization (microtufts) to explore the aerodynamic behavior of the rotating airfoil at high values of blade incidence. This paper also reviews experimental evidence and infers some high lift coefficient behavior from it. Comparisons between predicted thrust, utilizing modified airfoil characteristics and a blade element model, and measured thrust for both rotors and propellers that cover the extremes of collective pitch are shown and discussed.
    Keywords: Aerodynamics
    Type: AGARD Aerodynamic Conference; Oct 01, 1994; Berlin; Germany
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    Cellular microtubules heterogeneous in their content of microtubule-associated protein 4 (MAP4) (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 133-149 
    Details
    ISSN: 0886-1544
    Keywords: MAP4 depletion ; antibody blocking ; detyrosination ; midbody ; asymmetric cell processes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous immunolocalization studies using many primate cultured cell lines demonstrated that a microtubule-associated protein of Mr ∼210,000 which is now called MAP4, is present along the length of microtubules in interphase and mitotic cells [Bulinski and Borisy (1980) J. Cell Biol. 87:802-808; DeBrabander et al. (1981) J. Cell Biol. 91:438-455]. Since MAP4 has been implicated as a microtubule stabilizer, we asked whether all classes of microtubules possess an equal complement of MAP4. We have reexamined the cellular distribution of MAP4, using both conventional double-label immunofluorescence and an antibody blocking technique [Schulze and Kirschner (1987) J. Cell Biol. 104:277-288] to highlight microtubules lacking, or depleted in, MAP4. These techniques have revealed that thin processes extending from monkey kidney cells (TC-7), and those made by human neuroblastoma cells (IMR-32) in response to retinoic acid, are often deficient in MAP4 immunoreactivity. Since both types of cellular processes contain stable microtubules, which are enriched in detyrosinated (Glu) tubulin, we tested the ability of MAP4 to bind to microtubules made from pure Glu and pure tyrosinated (Tyr) tubulin in vitro. MAP4 bound to both types of microtubules, and the similar saturation level of MAP4 binding to Glu and Tyr microtubules suggested that differential binding to these forms of tubulin does not contribute directly to a mechanism for segregation of MAP4 on microtubules in vivo. In TC-7 cells, we also observed MAP4-depletion on single microtubules, distal regions of broad cytoplasmic extensions, and midbodies of dividing cells. MAP4 depletion may reflect recent, rapid growth of microtubules to which MAP4 has not yet bound, or the presence of other MAPs that may compete with MAP4 for binding sites on the MT. We suggest that different levels of MAP4 on microtubules may directly modulate microtubule dynamics within single cells, as well as other microtubule functions such as those involving microtubule motor activity. © 1994 Wiley-Liss, Inc.
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    Regulation of the Ascaris major sperm protein (MSP) cytoskeleton by intracellular pH (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 193-205 
    Details
    ISSN: 0886-1544
    Keywords: amoeboid motility ; fluorescence ratio imaging ; BCECF ; nematodes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development and locomotion of the amoeboid sperm of the nematode, Ascaris suum, depend on precise control of the assembly of their unique major sperm protein (MSP) filament system. We used fluorescence ratio imaging of cells loaded with BCECF to show that intracellular pH (pHi) is involved in controlling MSP polymerization in vivo. Spermatogenesis is marked by a cycle of MSP assembly-disassembly-reassembly that coincides with changes in pHi. In spermatocytes, which contain MSP in paracrystalline fibrous bodies, pHi was 6.8, 0.6 units higher than in spermatids, which disassemble the fibrous bodies and contain no assemblies of MSP filaments. Activation of spermatids to complete development resulted in rapid increase in pHi to 6.4 and reappearance of filaments. Treatment of spermatocytes with weak acids caused the fibrous bodies to disassemble whereas incubation of spermatids in weak bases induced MSP assembly. The MSP filaments in spermatozoa are organized into fiber complexes that flow continuously rearward from the leading edge of the pseudopod. These cells established a pseudopodial pH gradient with pHi 0.15 units higher at the leading edge, where fiber complexes assemble, than at the base of the pseudopod, where disassembly occurs. Acidification of these cells caused the MSP cytoskeleton to disassemble and abolished the pH gradient. Acid removal resulted in reassembly of the cytoskeleton, re-establishment of the pH gradient, and re-initiation of motility. MSP assembly in sperm undergoing normal development and motility and in cells responding to chemical manipulation of pHi occurs preferentially at membranes. Thus, we propose that filament assembly in sperm is controlled by pH-sensitive MSP-membrane interaction. © 1994 Wiley-Liss, Inc.
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    Different temporal patterns of expression result in the same type, amount, and distribution of filamin (ABP) in cardiac and skeletal myofibrils (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 248-261 
    Details
    ISSN: 0886-1544
    Keywords: myogenesis ; protein isoforms ; muscle types ; Z-disc ; phosphorylation ; chicken muscle ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphogenesis of functional myofibrils in chick skeletal and cardiac muscle occurs in greatly different time spans, in about 7 and 2 days, respectively. In chick skeletal myogenic cells, one isoform of the 250 kD actin-binding protein (ABP) filamin is associated with stress fiber-like structures of myoblasts and early myotubes, then disappears for approximately 4 days, whereupon a second filamin isoform reappears at the Z-disc periphery. We sought to determine if cardiac myogenesis involves this sequence of appearance, disappearance, and reappearance of a new filamin isoform in a compressed time scale. It was known that in mature heart, filamin is localized at the Z-disc periphery as in mature (fast) skeletal muscle, and is also associated with intercalated discs. We find that myocardial filamin has an apparent molecular weight similar to that of adult skeletal muscle filamin and lower than that of smooth muscle filamin, and that both skeletal and cardiac muscle contain roughly 200 filamin monomers per sarcomere. Two-dimensional peptide mapping shows that myocardial filamin is very similar to skeletal muscle filamin. Myocardial, slow skeletal, and fast skeletal muscle filamins are all phosphorylated, as previously shown for filamin of non-striated muscle. Using immunofluorescence, we found that filamin could not be detected in the developing heart until the 14-somite stage, when functional myofibrils exist and the heart has been beating for 3 to 4 hours. We conclude that in cardiac and skeletal myogenesis, different sequences of filamin gene expression result in myofibrils with similar filamin distributions and isoforms. © 1994 Wiley-Liss, Inc.
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    Regulation and evolution of the single alpha-tubulin gene of the ciliate Tetrahymena thermophila (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 272-283 
    Details
    ISSN: 0886-1544
    Keywords: cell cycle ; transcription ; mRNA decay ; autoregulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The single alpha-tubulin gene of Tetrahymena thermophila was isolated from a genomic library and shown to encode a single protein. Comparisons of the rates of evolution of this gene with other alpha-tubulin sequences revealed that it belongs to a group of more evolutionarily constrained alpha-tubulin proteins in animals, plants, and protozoans versus the group of more rapidly evolving fungal and variant animal alpha-tubulins. The single alpha-tubulin of Tetrahymena must be used in a variety of microtubule structures, and we suggest that equivalently conserved alpha-tubulins in other organisms are evolutionarily constrained because they, too, are multifunctional. Reduced constraints on fungal tubulins are consistent with their simpler microtubule systems. The animal variant alpha-tubulins may also have diverged because of fewer functional requirements or they could be examples of specialized tubulins. To analyze the role of tubulin gene expression in regulation of the complex microtubule system of Tetrahymena, alpha-tubulin mRNA amounts were examined in a number of cell states. Message levels increased in growing versus starved cells and also during early stages of conjugation. These changes were correlated with increases in transcription rates. Additionally, alpha-tubulin mRNA levels oscillate in a cell cycle dependent fashion caused by changes in both transcription and decay rates. Therefore, as in other organisms, Tetrahymena adjusts alpha-tubulin message amounts via message decay. However the complex control of alpha-tubulin mRNA during the Tetrahymena life cycle involves regulation of both decay and transcription rates. © 1994 Wiley-Liss, Inc.
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    Microtubule centers and the interphase microtubule cytoskeleton in amoebae of the cellular slime molds (mycetozoans) Acytostelium leptosomum and Protostelium mycophaga (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 45-58 
    Details
    ISSN: 0886-1544
    Keywords: MTOC ; cytoplasmic microtubule complex ; antitubulin ; Immunofluorescence ; ultrastructure ; immunogold ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We investigated the microtubule (MT) cytoskeleton and microtubule centers (MTC) in undifferentiated amoebae by indirect immunofluorescence with six monoclonal antitubulin antibodies, and by transmission electron microscopy and immunogold ultracytochemistry. Interphase amoebae of both species contain a distinct cytoplasmic complex of MTs, which is more elaborate in Protostelium mycophaga. In Acytostelium leptosomum amoebae a single MTC is attached to each interphase nucleus at its pointed end, as in the other dictyostelid cellular slime molds Dictyostelium discoideum and Polysphondylium violaceum. Ultrastructurally, MTCs of A. leptosomum also resemble those of these two species: They consist of an electron-opaque core shaped like a stout rod, which is embedded, together with nodules, in a fuzzy matrix. The nodules are the points of origin of the MTs. In most amoebae of P. mycophaga there are two MTCs on opposite sides of and close to the nucleus, but many amoebae also contain a variable number of MTCs that are remote from the nucleus. Nucleus-associated and “remote” MTCs are structurally identical. They consist of a ring-shaped core with inner and outer diameters of ca. 130 nm and 340 nm. A plug sits in the ring, and satellites are connected to the core by fine fibrils. The satellites are the points of origin of MTs. New MTCs are apparently formed during mitosis, the parent MTC probably serving as a template for the genesis of a new ring. The results support the notion that phylogenetically related organisms have similarly constructed MTCs and that these are dissimilar in less closely related organisms. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970280105
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    Movement of Myzostomum spermatozoa: Calcium ion regulation of swimming direction (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 135-142 
    Details
    ISSN: 0886-1544
    Keywords: bidirectional swimming ; flagellar movement ; helical bends ; 9+0 axoneme ; planar bends ; viscosity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Spermatozoa of the small myzostomid worm Myzostomum cirriferum usually swim with the flagellum foremost but occasionally stop and then swim with the head foremost. The spermatozoa have axoneme of the 9+0 type; thus each lacks the central pair microtubules. The flagellum emerges in the anterior end of the cell body and attaches to it with junctions. To understand the mechanism regulating the swimming direction of the spermatozoa, we recorded the sperm and their flagellar movements using a video camera with a high-speed shutter. The effects of calcium and viscosity on these movements were also examined.The cell body with the flagellum attached to it formed a curved plate during beating, while the free portion of the flagellum beats with small helical bends. Motive force to propel a spermatozoon was mainly due to the bends in the cell body. The spermatozoa reversed the direction of their swimming as a result of a change in the direction of bend propagation. The direction of bend propagation was regulated by calcium; the bends in the cell body propagated from the end of the head toward the free portion of the flagellum at low concentrations of Ca2+, whereas the direction of bend propagation was reversed at high concentrations of this ion. High viscosity of the medium stimulated a change in the direction of bend propagation. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970280205
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  • 51
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    Role of tropomyosin, α-actinin, and actin binding protein 280 in stabilizing triton insoluble f-actin in basal and chemotactic factor activated neutrophils (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 155-164 
    Details
    ISSN: 0886-1544
    Keywords: microfilamentous cytoskeleton ; actin binding proteins ; formyl peptides ; ionic extraction ; immunoblots ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: F-actin is a major component of the neutrophil (PMN) cytoskeleton. In basal PMNs, F-actin exists in two structurally and functionally distinct pools: Triton insoluble F-actin (TIF)-cold insensitive, not depolymerizable by dilution, and distributed in pseudopods and submembranous locations; and Triton soluble F-actin (TSF)-unstable in cold, diffusely distributed, and gelsolin enriched. The element(s) conferring these unique properties to the Triton insoluble F-actin pool are unknown, but logically include distinct actin regulatory proteins. To study the morphologic and functional determinants of the Triton insoluble F-actin pool, the distribution and quantity of three candidate regulatory proteins, α-actinin, tropomyosin (TM), and actin binding protein (ABP-280), were compared in F-actin (Triton insoluble and Triton soluble) and G-actin pools isolated from basal and chemotactic factor activated human PMNs in suspension, using immunoblots and ionic extraction. F-actin content was measured by NBDphallacidin binding and gel scans. The results show that: (1) α-actinin, actin binding protein 280, and tropomyosin are localized to TIF and excluded from TSF; (2) TM, α-actinin, and ABP 280 are required to stabilize fractions of Triton insoluble F-actin in PMNs; and (3) chemotactic factor activation results in release of a fraction of TM from the Triton insoluble F-actin pool in temporal association with F-actin polymerization in the Triton insoluble F-actin pool. Shifts in ABP 280 or α-actinin do not occur. The results suggest that TM, α-actinin, and ABP 280 provide structure to TIF and that TM release from TIF is involved in chemotactic factor induced actin polymerization in PMNs. © 1994 Wiley-Liss, Inc.
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    Characterization of keratin densities in mitotic wish cells (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 165-178 
    Details
    ISSN: 0886-1544
    Keywords: WISH ; Keratin ; 3-D reconstruction ; mitosis ; intermediate filaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Three dimensional (3-D) reconstruction of four mitotic WISH cells from ultrathin sections gave an informative representation of the spatial distribution of keratin densities in these cells. The correspondence between the densities as studied by transmission electron microscopy (TEM) and the Keratin bodies initially revealed by immunoflourescent colabeling of cultures, was confirmed by immunoelectron-microscopy. The smaller, and sometimes more elongated densities, were relatively abundant just beneath the subplasmalemmal microfilament band; and at certain levels of the mitotic cell they were observed to be connected to neighboring densities by intact intermediate filaments (IFs). The larger and more spherical densities appeared to be somewhat more discrete and randomly distributed. Other observed associations of the keratin densities included the telophase contractile ring of microfilaments, chromosomes, the reformed telophase nucleus, and desmosomal junctions with neighboring interphase cells. Cytochalasin D (CD) treatment of cells displaced the peripheral keratin densities toward the cell membrane. The density volume constituted 0.52% to 1.57% of the total cell volume, and the proportional density size was decreased in the cells that had progressed into anaphase and telophase. The observed formation and subsequent dissolution of keratin densities during mitosis may represent a dynamic mechanism of restructuring the keratin cytoskeleton in an unpolymerized form in order to allow for rapid reformation of interphase cell junctions. The physical associations observed between intact IFs and the keratin densities may provide support at certain depths of the mitotic cell, and the juxtaposition of densities with nuclear components suggests a possible source of and role for keratin IFs during nuclear events. © 1994 Wiley-Liss, Inc.
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    Control of flagellar bending: A new agenda based on dynein diversity (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 199-204 
    Details
    ISSN: 0886-1544
    Keywords: axoneme ; cilia ; flagella ; microtubule ; motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Observations that were interpreted to provide evidence for equivalent functions of all axonemal dyneins should be reinterpreted, and models based on this assumption should be abandoned. In the future, attempts to understand the mechanisms for flagellar bending, oscillation, and bend propagation should start from the assumption that each type of axonemal dynein may have a specific function. At least three distinct functions can now be identified: bend initiation, maintenance of the angle of propagating bends, and generation of power to overcome viscous resistances. Only the last of these three functions is an outer arm dynein function. © 1994 Wiley-Liss, Inc.
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    Cloning and sequencing of cDNAs encoding the actin cross-liking protein transgelin defines a new family of actin-associated proteins (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 243-255 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; actin binding ; transgelin sequence ; gelation ; gene family ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have used degenerate oligonucleotides, derived from the amino acid sequence of transgelin peptides [Shapland et al., 1993: J. Cell Biol. 121:1065-1073], to isolate and sequence overlapping cDNA clones encoding this actin gelling protein. Primers with 5′ restriction enzyme sites directed against the N and C terminal amino acids present in these clones were then used to amplify and clone the entire transgelin coding region from reverse transcribed rat small intestine cDNA (RT-PCR). These studies have shown that transgelin is the product of a single gene which is conserved between yeast, Drosophila, molluscs, and humans. Transgelin is expressed as a single message that is regulated at the level of transcription in SV40 transformed 3T3 cells. Our data have shown that transgelin and several other proteins of unknown function, SM22α [Pearlstone et al., 1987: J. Biol. Chem. 262:5985-5991], mouse p27 [Almendral et al., 1989: Exp. Cell Res. 181:518-530], and human WS3-10 [Thweatt et al., 1992: Biochem. Biophys. Res. Commun. 187:1-7], share extensive homology. More limited regions of homology shared between transgelin and other proteins such as rat NP25 (unpublished), chicken calponins α and β [Takahashi and Nadal-Ginard, 1991: J. Biol. Chem. 266:13284-13288], and Drosophila mp20 [Ayme-Southgate et al., 1989: J. Cell Biol. 108:521-531] suggest that all of these proteins may be classified as members of a new transgelin multigene family. © 1994 Wiley-Liss, Inc.
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    Signal transduction and calcium: A suggested role for the cytoskeleton in inositol 1,4,5-trisphosphate action (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 279-284 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970280402
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    Coordinated expression of five tropomyosin isoforms and β-actin in astrocytes treated with dibutyryl cAMP and cytochalasin D (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 303-316 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; cell culture ; gene expression ; Northern blot ; serum-induction ; rat ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytochalasin D and dBcAMP cause cultured astrocytes to change from flat cells to retrated process-bearing cells. F-actin was present throughout cells stimulated with dBcAMP for 16 h, whereas cytochalasin D caused F-actin to form massive aggregates at the tips of the cell processes. The two drugs differently regulated the expression of both β-actin and tropomyosin genes in astrocytes cultured in the presence or absence of serum: dBcAMP caused down-regulation and cytochalasin D caused up-regulation. Northern blot analyses indicated that: (1) serum deprivation halved the concentration of all tropomyosin transcripts (TM-1, TM-2, TM-4, TMBr-1, TMBr-2). Serum induced TM-4 via transcriptional activation, independent of protein synthesis, (2) dBcAMP induced down-regulation of β-actin (-50%) and tropomyosin transcripts (-35 to 52%) even in the presence of serum. The concentration of profilin mRNA decreased in dBcAMP-reactive astrocytes (-46%). The decrease in β-actin mRNA concentration was not blocked by cycloheximide, whereas down-regulation of tropomyosin transcripts was completely reversed when protein synthesis was inhibited, and (3) cytochalasin D induced an increase in the concentration of tropomyosin transcripts (+ 69 to 185%) which was cumulative with serum stimulation. Cytochalasin D induction of both β-actin and TM-4 operated through transcriptional activation, independent of protein synthesis.The production of all tropomyosin transcripts examined here were strictly coordinated with β-actin expression in serum-, dBcAMP- and cytochalasin D-treated astrocytes. This indicates that the differential expression of tropomyosin isoforms occurring during astrocyte maturation is due to more complex regulation than that involved in serum- or cAMP-stimulated astrocytes. © 1994 Wiley-Liss, Inc.
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    Metachronal activity of cultured mucociliary epithelium under normal and stimulated conditions (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 333-345 
    Details
    ISSN: 0886-1544
    Keywords: ciliary beat frequency ; metachronal wave ; ciliary coupling ; extracellular ATP ; acetylcholine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the present work we measured in real time the metachronism and degree of correlation between beating cilia from cultured mucociliary epithelium. The method is based on simultaneous measurement of ciliary beat frequency, phase shifts, and correlation factors in two directions: parallel and perpendicular to the effective stroke direction (ESD). From the phase shifts the lengths of wave components, and consequently the metachronal wavelength and direction, were evaluated.On active ciliary areas of cultured frog esophagus under normal conditions, a relatively high degree of correlation is observed, but cilia are more correlated in direction parallel to ESD which is also the direction of the mucus propulsion. The length of the wave component parallel to ESD is more than twice as large as that of the perpendicular component. The metachronal wavelength was found to be in the range of 5-9 μm, and the direction of the wave propagation was in the range of 90°-125° clockwise to the ESD.When ciliary beat frequency was rapidly increased by extracellular ATP or acetylcholine, only minor effects were observed on the degree of correlation between beating cilia. The length of the wave component parallel to ESD showed the most dramatic effect increasing up to tenfold. The perpendicular to ESD component was not affected by the stimulation. Consequently, the metachronism became more laeoplectic with the angle between the ESD and the wave directions decreasing by 10°-30°, and the metachronal wavelength remained unaltered. © 1994 Wiley-Liss, Inc.
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    Assembly and bundling of marginal band microtubule protein: Role of tau (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 57-71 
    Details
    ISSN: 0886-1544
    Keywords: microtubule bundling ; cytoskeleton ; tau ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubule protein extracted from dogfish erythrocyte cytoskeletons by disassembly of marginal bands at low temperature formed linear microtubule (MT) bundles upon reassembly at 22°C. The bundles, which were readily visible by video-enhanced phase contrast or DIC microscopy, increased in length and thickness with time. At steady state after 1 hour, most bundles were 6-11 μm in length and 2-5 MTs in thickness. No inter-MT cross-bridges were visible by negative staining. The bundles exhibited mechanical stability in flow as well as flexibility, in this respect resembling native marginal bands. As analyzed by SDS-PAGE and immunoblotting, our standard extraction conditions yielded MT protein preparations and bundles containing tau protein but not high molecular weight MAPs such as MAP-2 or syncolin. In addition, late fractions of MT protein obtained by gel filtration were devoid of high molecular weight proteins but still produced MT bundles. The marginal band tau was salt-extractable and heat-stable, bound antibodies to mammalian brain tau, and formed aggregates upon desalting. Antibodies to tau blocked MT assembly, but both assembly and bundling occurred in the presence of antibodies to actin or syncolin. The MTs were “unbundled” by subtilisin or by high salt (0.5-1 M KCl or NaCl), consistent with tau involvement in bundling. High salt extracts retained bundling activity, and salt-induced unbundling was reversible with desalting. However, reversibility was observed only after salt-induced MT disassembly had occurred. Reconstitution experiments showed that addition of marginal band tau to preassembled MTs did not produce bundles, whereas tau presence during MT reassembly did yield bundles. Thus, in this system, tau appears to play a role in both MT assembly and bundling, serving in the latter function as a coassembly factor. © 1994 Wiley-Liss, Inc.
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    Striated fibers in trichomonads: Costa proteins represent a new class of proteins forming striated roots (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 82-93 
    Details
    ISSN: 0886-1544
    Keywords: trichomonads ; cytoskeleton ; antibodies ; electrophoresis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The production of monoclonal antibodies and the use of biochemical techniques revealed that B-type costa proteins in trichomonads are composed of several major polypeptides with molecular weight detected between 100 and 135 kDa similar to those found in the A-type costae. Although differences were observed between the two types in their fine structure, we tested whether proteins composing the two costa types belong to the same protein family. A polyclonal antibody produced against the 118 kDa costa protein of Trichomonas vaginalis also recognized a 118 kDa costa protein in all other trichomonad genera studied so far whether they have A- or B-type costae. Moreover biochemical characteristics of costa proteins indicated that these proteins might represent a novel class of striated root-forming proteins in addition to centrin, giardin, and assemblin. © 1994 Wiley-Liss, Inc.
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    Microtubule associated protein MAP1A is an actin-binding and crosslinking protein (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 110-116 
    Details
    ISSN: 0886-1544
    Keywords: high-molecular weight MAPs ; microfilaments ; microtubules ; low-shear viscometry ; taxol ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: High molecular weight microtubule-associated proteins MAP1A and MAP2 form thin projections from microtubule surfaces and have been implicated in crosslinking microtubules and other cytoskeletal components. We have purified native MAP1A from bovine brain and have studied its interaction with G- and F-actin. Using a solid-phase immunoassay we show that MAP1A binds in a dose-dependent manner to both G-actin and F-actin. Addition of MAP1A to F-actin causes gelation of F-actin and SDS-PAGE analysis shows that MAP1A co-sediments with the gelled network, under conditions where F-actin alone does not pellet. The low apparent viscosity of F-actin is markedly increased in the presence of MAP1A, suggesting that MAP1A can crosslink F-actin. Co-incubation experiments indicate that MAP1A and MAP2 may bind to common or overlapping sites on the actin molecule. The widespread distribution of MAP1A and its interaction with microtubules, actin, and intermediate filaments suggests that it may constitute an important determinant of neuronal and non-neuronal cellular morphology. © 1994 Wiley-Liss, Inc.
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    A model of flagellar and ciliary functioning which uses the forces transverse to the axoneme as the regulator of dynein activation (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 141-154 
    Details
    ISSN: 0886-1544
    Keywords: dynein arms ; nexin links ; radial spokes ; relaxation oscillator ; doublet microtubules ; biological oscillators ; computer model ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ciliary and flagellar motion is driven by the dynein-tubulin interaction between adjacent doublets of the axoneme, and the resulting sliding displacements are converted into axonemal bends that are propagated. When the axoneme is bent in the normal beating plane, force develops across the axoneme in the plane of the bend. This transverse force (t-force) has maximal effect on the interdoublet spacing of outer doublets 2-4 on one side of the axoneme and doublets 7-9 on the opposite side. Episodes of sliding originates as the t-force brings these doublets into closer proximity (allowing dynein bridges to form) and are terminated when these doublets are separated from each other by the t-force. A second factor, the adhesive force of the dynein-tubulin attachments (bridges), also acts to pull neighboring doublets closer together. This force resists termination of a sliding episode once initiated, and acts locally to give the population of dynein bridges a type of excitability. In other words, as bridges form, the probability of nearby bridges attaching is increased by a positive feedback exerted through the interdoublet spacing. A conceptual working hypothesis explaining the behavior of cilia and flagella is proposed based on the above concepts. Additionally, the feasibility of this proposed mechanism is demonstrated using a computer simulation. The simulation uses a Monte Carlo-type algorithm for dynein attachment and adhesive force, together with a geometric evaluation of the t-force on the key microtubule pairs. This model successfully develops spontaneous oscillations from any starting configuration (including a straight position). It is compatible with the physical dimensions, mechanical properties and bridge forces measured in real cilia and flagella. In operation, it exhibits many of the observed actions of cilia and flagella, most notably wave propagation and the ability to produce both cilia-like and flagella-like waveforms. © 1994 Wiley-Liss, Inc.
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    Modulation of fibroblastic cytoskeletal features during pathological situations: The role of extracellular matrix and cytokines (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 195-203 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Characterization of a monoclonal antibody prepared against plant actin (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 339-344 
    Details
    ISSN: 0886-1544
    Keywords: microfilament ; phalloidin ; immunoblotting ; immunocytochemistry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Anti-actin monoclonal antibodies were prepared using phalloidin-stabilized actin that was purified from pea roots by DNase I affinity chromatography. One monoclonal antibody, designated mAb3H11, bound plant actin in preliminary screenings and was further analyzed. Immunoblot analysis showed that this antibody had a high affinity for plant actin in crude and purified preparations but a low affinity for rabbit muscle actin. In immunoblots of plant extracts separated on two-dimensional gels it appeared to bind all actin isoforms recognized by the JLA20 anti-chicken actin antibody. Using immunofluorescent cytochemistry, the antibody was used to observe actin filaments in aldehyde-fixed and methanol-treated tobacco protoplasts. These results indicate that mAb3H11 should be a useful reagent for the study of plant actins. © 1994 Wiley-Liss, Inc.
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    Microtubules restrict plastid sedimentation in protonemata of the moss Ceratodon (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 366-374 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; microfilaments ; cytochalasin ; gravity ; amiprophos-methyl ; tip-growth ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Apical cells of protonemata of the moss Ceratodon purpureus are unusual among plant cells with sedimentation in that only some amyloplasts sediment and these do not fall completely to the bottom of vertical cells. To determine whether the cytoskeleton restricts plastid sedimentation, the effects of amiprophos-methyl (APM) and cytochalasin D (CD) on plastid position were quantified. APM treatments of 30-60 min increased the plastid sedimentation that is normally seen along the length of untreated or control cells. Longer APM treatments often resulted in more dramatic plastid sedimentation, and in some cases almost all plastids sedimented to the lowermost point in the cell. In contrast, the microfilament inhibitor CD did not affect longitudinal plastid sedimentation compared to untreated cells, although it did disturb or eliminate plastid zonation in the tip. These data suggest that microtubules restrict the sedimentation of plastids along the length of the cell and that microtubules are load-bearing for all the plastids in the apical cell. This demonstrates the importance of the cytoskeleton in maintaining organelle position and cell organization against the force of gravity. © 1994 Wiley-Liss, Inc.
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    Occurrence of fibers and their association with talin in the cleavage furrows of PtK2 cells (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 26-40 
    Details
    ISSN: 0886-1544
    Keywords: cleavage furrows ; cytokinesis ; actin ; phalloidin ; myosin ; filamin ; talin ; attachment plaques ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: PtK2 cells of exceptionally large size were microinjected with fluorescently labeled probes for actin, myosin, filamin, and talin in order to follow the assembly of the contractile proteins into the cleavage furrows. Whereas in cells of normal size, there is usually a diffuse pattern of localization of proteins in the cleavage furrow, in these large, flat cells the labeled proteins localized in fibers in the cleavage furrow. Often, the fibers were striated in a pattern comparable to that measured in the stress fibers of the same cell type. The presence of talin in discrete plaques along fibers in the cleavage furrows of the large cells suggests a further similarity between cleavage furrow and stress fiber structure. The presence of filamin in the cleavage furrows also suggests the possibility of an overlapping mechanism in addition to that of a talin mediated mechanism for the attachment of actin filaments to the cell surfaces in the cleavage furrow. A model is presented that emphasizes the interrelationships between stress fibers, myofibrils, and cleavage furrows. © 1994 Wiley-Liss, Inc.
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    Role of MAPs and motors in the bundling and shimmering of native microtubules from insect ovarioles (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 69-78 
    Details
    ISSN: 0886-1544
    Keywords: kinesin ; dynein ; MAP-motor interactions ; microtubule arrays ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Bundles of native microtubules isolated from the ovarioles of hemipteran insects are seen to shimmer when observed using dark-field microscopy. This novel form of microtubule motility becomes even more obvious when the isolated bundles are detergent-extracted and reactivated. We have studied the nucleotide-specificity and the drug-sensitivity of microtubule shimmering in order to obtain information regarding the nature of the motor protein responsible, and to compare its properties with those of previously characterised microtubule motors. The involvement of structural MAPs in the shimmering and in maintenance of microtubule bundles in this system has also been investigated. © 1994 Wiley-Liss, Inc.
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    Role of microtubules in random cell migration: Stabilization of cell polarity (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 88-96 
    Details
    ISSN: 0886-1544
    Keywords: cell movement ; speed ; persistence time ; colcemid ; alveolar macrophage ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The role of microtubules in random cell migration was investigated using time-lapse videomicroscopy to record in vitro the shape and motile behavior of guinea pig alveolar macrophages before and after disrupting microtubules with colcemid. Cell migration was quantified in terms of directional persistence time and speed. Motility was also correlated with morphological polarity: cells having a single lamellipodal region (monopolar cells) migrated, whereas those lacking a lamellipod (apolar cells) or with opposing lamellipodal regions (bipolar cells) did not migrate. Within 2 hours, colcemid caused a shift in polarity from 80% monopolar cells to 40% monopolar and 40% bipolar cells and a corresponding decrease from 80% to 40% in the fraction of migrating cells. Mean persistence time and speed decreased only slightly (approximately 20%) for those cells (still monopolar) which continued to migrate in the presence of colcemid. Persistence time and speed actually increased for many individual cells, indicating that random migration did not require intact microtubules. We conclude that colcemid treatment destabilizes monopolarity, leading to the gradual loss of monopolarity and consequent inhibition of migration. While a cell remains monopolar, it will continue to migrate even in the absence of intact microtubules, but microtubules are required for the long-term maintenance of cellular monopolarity and, thus, for continued motility. © 1994 Wiley-Liss, Inc.
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994) 
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    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Cellular infrared detector appears to be contained in the centrosome (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 262-271 
    Details
    ISSN: 0886-1544
    Keywords: 3T3 cells ; cell motility ; infrared ; phototaxis ; centrosome ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous experiments have suggested that 3T3 cells were able to extend pseudopodia toward latex particles up to 60 μm away from the cell body if the particles were irradiated by an infrared beam in the range of 700-900 nm [Albrecht-Buehler, 1991: J. Cell Biol. 114:493-502]. The present article reports that this response of cells to infrared light can be inhibited if the cell center is simultaneously irradiated with a beam of the same light. In marked contrast, the cells responded normally to the presence of infrared light scattering particles if the second beam irradiated other parts of the cell body. The results imply that the cellular mechanism of infrared detection is located at the cell center. The infrared sensing mechanism remains intact in enucleated cells and in cells which were incubated in monensin to vesiculate their Golgi apparatus and inhibit their Golgi functions. Accordingly, it is proposed that the centrosome which contains the centrioles is the only remaining candidate in the cell center for a cellular detection device for the direction of infrared signal sources. The results support an earlier suggestion that centrioles may be such detection devices [Albrecht-Buehler, 1981: Cell Motil. Cytoskeleton 1:237-245]. © 1994 Wiley-Liss, Inc.
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    Role of cAMP in the reactivation of demembranated ram spermatozoa (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 206-218 
    Details
    ISSN: 0886-1544
    Keywords: sperm motility ; sperm maturation ; flagella ; protein kinases ; protein kinase inhibitor ; cGMP ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ejaculated ram sperm were demembranated with Triton X-100, separated from the detergent-soluble matrix, and reactivated [San Agustin and Witman (1993): Cell Motil. Cytoskeleton 24:264-273]. The percent motility of models prepared from freshly washed sperm was comparable to that of the washed sample before demembranation, regardless of whether cAMP was included in the reactivation medium. However, demembranated models derived from aging or metabolically inhibited sperm exhibited a lower percent reactivation and required cAMP to attain the level of motility of freshly washed sperm. Cyclic AMP was ∼100 times more effective than cGMP. The requirement for cAMP could be bypassed by addition of porcine heart cAMP-dependent protein kinase (PKA) catalytic subunit to the reactivation medium, demonstrating that cAMP was acting via PKA. The cAMP stimulation of reactivation was not affected by inclusion of the PKA inhibitor PKI(5-24) in the reactivation medium, but was decreased when the models were preincubated with PKI(5-24) prior to reactivation. The cytosol-free models retained 〉90% of the sperm PKA activity; therefore, the PKA appears to be anchored to internal sperm structures. This PKA could not be extracted by cAMP or Triton X-100 alone, but only by cAMP and Triton X-100 in combination. We conclude that cAMP-dependent protein phosphorylation is critical for sperm motility, but that the essential protein phosphate sites turn over slowly under our reactivation conditions, so that the cAMP requirement is apparent only in models prepared from sperm having a low internal ATP or cAMP content. Interestingly, reactivation was rapidly blocked by the peptide arg-lys-arg-ala-arg-lys-glu, which has been reported to be a selective inhibitor of cGMP-dependent protein kinase. © 1994 Wiley-Liss, Inc.
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    Announcement (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 286-286 
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    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Physical model of axonemal splitting (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 287-298 
    Details
    ISSN: 0886-1544
    Keywords: cilium ; flagellum ; motility ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A physical model developed to explain microtubule sliding patterns in the trypsintreated ciliary axoneme has been extended to investigate the generation of bending moments by microtubules sliding in an axoneme in which the dublets are anchored at one end. With sliding restricted, a bending moment is developed by the polarized shearing interaction between neighbouring doublets, effected by the activity of dynein arms on doublet N pushing N + 1 in a tipward ( + ) direction. In arrested axonemes in which arms on several contiguous doublets are active, the bending moment causes splitting of the 9 + 2 microtubule array into two or more sets of doublets. In the absence of special constraints, splitting depends only on breaking the circumferential interdoublet links most distorted by the bending moment. The analysis, which permits assignment of arm activity to specific microtubules in each of the observed patterns of splitting, indicates that the axoneme will split between doublet N and N + 1 if arms on doublet N are inactive and arms on either N + 1 or N-1 are active. To produce the observed major splits, dynein arms on the microtubules of roughly one-half of the axoneme are predicted to be active, in a manner consistent with the switch-point hypothesis of ciliary motion. Electron microscopic examination indicates that virtually every set of doublets in the split axonemes retains its cylindrical form. Maintenance of cylindrical symmetry can be ascribed to the mechanical properties of the unbroken links, which may resist both tensile and compressive stress, and to active dynein arms. © 1994 Wiley-Liss, Inc.
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    Cell motility and the cytoskeleton video supplement 4 (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 361-372 
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    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994) 
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    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970280301
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    Microtubule-associated protein function: Lessons from expression in spodoptera frugiperda cells (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 195-198 
    Details
    ISSN: 0886-1544
    Keywords: baculovirus ; tau ; MAP2 ; neuronal cytoskeleton ; growth cones ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The phenotypes induced by the expression of neuronal microtubule-associated proteins (MAPs) in Sf9 cells have provided data on the in situ function of these proteins. Both MAP2 and tau can induce long processes in Sf9 cells, and the processes contain bundles of microtubules. In both cases the microtubules are aligned with their plus ends distal. Tau expression usually induces a single process that is unbranched and of uniform caliber. Processes can form even when the cells are grown in suspension. Microtubules do not extend all the way to the tip; instead the terminal region contains an actin-rich meshwork. Taxol treatment of Sf9 cells also induces the assembly of microtubules into bundles but does not induce process formation in Sf9 cells. Therefore the in vitro properties of tau as a molecule capable of assembling, stabilizing, and bundling microtubules do not fully account for the in vivo ability of tau alone to transduce microtubule assembly into a change in cell shape. The morphological features of the processes induced by MAP2 differ in highly informative ways. © 1994 Wiley-Liss, Inc.
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    Movement of axoplasmic organelles on actin filaments from skeletal muscle (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 231-242 
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    ISSN: 0886-1544
    Keywords: squid axoplasm ; organelle movement ; calmodulin ; actin filaments ; axonal transport ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: It was recently shown that, in addition to the well-established microtubule-dependent mechanism, fast transport of organelles in squid giant axons also occurs in the presence of actin filaments [Kuznetsov et al., 1992, Nature 356:722-725]. The objectives of this study were to obtain direct evidence of axoplasmic organelle movement on actin filaments and to demonstrate that these organelles are able to move on skeletal muscle actin filaments. Organelles and actin filaments were visualized by video-enhanced contrast differential interference contrast (AVEC-DIC) microscopy and by video intensified fluorescence microscopy. Actin filaments, prepared by polymerization of monomeric actin purified from rabbit skeletal muscle, were stabilized with rhodamine-phalloidin and adsorbed to cover slips. When axoplasm was extruded on these cover slips in the buffer containing cytochalasin B that prevents the formation of endogenous axonal actin filaments, organelles were observed to move at the fast transport rate. Also, axoplasmic organelles were observed to move on bundles of actin filaments that were of sufficient thickness to be detected directly by AVEC-DIC microscopy. The range of average velocities of movement on the muscle actin filaments was not statistically different from that on axonal filaments. The level of motile activity (number of organelles moving/min/field) on the exogenous filaments was less than on endogenous filaments probably due to the entanglement of filaments on the cover slip surface. We also found that calmodulin (CaM) increased the level of motile activity of organelles on actin filaments. In addition, CaM stimulated the movement of elongated membranous organelles that appeared to be tubular elements of smooth endoplasmic reticulum or extensions of prelysosomes. These studies provide the first direct evidence that organelles from higher animal cells such as neurons move on biochemically defined actin filaments. © 1994 Wiley-Liss, Inc.
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    A conserved region in the tail domain of vimentin is involved in its assembly into intermediate filaments (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 265-277 
    Details
    ISSN: 0886-1544
    Keywords: intermediate filament proteins ; vimentin ; domain function ; filament assembly ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although the head and rod domains of intermediate filament (IF) proteins are known to play significant roles in filament assembly, the role of the tail domain in this function is unclear and the available information supports contradictory conclusions. We examined this question by comparing transfection of the same cDNA constructs, encoding vimentins with modified tail domains, into cell lines that do and do not contain endogenous IF proteins. By this approach, we were able to distinguish between the ability of a mutant IF protein to initiate assembly de novo, from that of incorporating into existing filament networks. Vimentins with modifications at or near a highly conserved tripeptide, arg-asp-gly (RDG), of the tail domain incorporated into existing IF networks in vimentin-expressing (vim+) cells, but were assembly-incompetent in cells that did not express IF proteins (vim-). The failure of the RDG mutant vimentins to assemble into filament arrays in vim- cells was reversible by re-introducing a wild-type vimentin cDNA, whereupon both wild-type and mutant vimentins coassembled into one and the same IF network. We conclude that the function of the tail domain of type III IF proteins, and possibly of keratins K8 and K18, in IF assembly is distinct from those of other domains; a region encompassing the RDG tripeptide appears to be important in the assembly process. © 1994 Wiley-Liss, Inc.
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    Dynamic instability of microtubules from cold-living fishes (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 327-332 
    Details
    ISSN: 0886-1544
    Keywords: tubulin ; isoforms ; Atlantic cod ; Antarctic fish ; evolutionary aspects ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The dynamic instability of microtubules free of microtubule-associated proteins from two genera of cold-living fishes was measured, by means of video-enhanced differential interference-contrast microscopy, at temperatures near those of their habitats. Brain microtubules were isolated from the boreal Atlantic cod (Gadus morhua; habitat temperature ∽ 2-15°C) and from two austral Antarctic rockcods (Notothenia gibberifrons and N. coriiceps neglecta; habitat temperature ∽ -1.8 to + 2°C). Critical concentrations for polymerization of the fish tubulins were in the neighborhood of 1 mg/ml, consistent with high interdimer affinities. Rates of elongation and frequencies of growth-to-shortening transitions (“catastrophes”) for fish microtubules were significantly smaller than those for mammalian microtubules. Slow dynamics is therefore an intrinsic property of these fish tubulins, presumably reflecting their adaptation to low temperatures. Two-dimensional electrophoresis showed striking differences between the isoform compositions of the cod and the rockcod tubulins, which suggests that the cold-adapted microtubule phenotypes of northern and southern fishes may have arisen independently. © 1994 Wiley-Liss, Inc.
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970290101
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    Novel touch-induced, Ca2+-dependent phobic response in a flagellate green alga (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 97-109 
    Details
    ISSN: 0886-1544
    Keywords: calcium ; flagellar movement ; mechanotransduction ; mechanoshock response ; Spermatozopsis similis ; video analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The biflagellate green alga Spermatozopsis similis exhibits a remarkable avoidance reaction in addition to the photophobic or stop response characteristic of such algae. S. similis normally swims forward with its anteriorly attached flagella directed posteriorly and propagating sine-like waves from base to tip. Upon contact with surfaces or other cells, S. similis responds with rapid backward swimming, covering distances of up to 50 μm in 140 to 220 msec. This reaction, which we term the mechanoshock response, also can be triggered by vigorous mechanical stimulation, but not by physiological light intensities. It consists of 3 phases: (1) a rapid acceleration phase with average duration of 31 msec; (2) a phase of about 66 msec with constant high speed (maximal velocities of 〉 600 μm·sec-1) or slow deceleration; and (3) a deceleration phase of ∼ 83 msec, followed by a stop or short period of circling. The cells then resume forward swimming in a random direction. Prior to the mechanoshock response the flagella rapidly are brought together into a close parallel configuration extending anteriorly of the cell body. They then appear to propel the cell by undulatory beating, while the cell describes a pronounced helical path. Small decreases in the extracellular Ca2+ concentration, as well as low concentrations of Ba2+, strongly suppress the probability of this phobic reaction. We conclude that this mechanoshock response involves large Ca2+ influxes, probably mediated by mechanosensitive and/or stretch-activated ion-channel(s). © 1994 Wiley-Liss, Inc.
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    Kinesin-related polypeptide is associated with vesicles from Corylus avellana pollen (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 155-166 
    Details
    ISSN: 0886-1544
    Keywords: Golgi vesicles ; pollen ; pollen tube ; microtubules ; kinesin-related protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A 100-kDa polypeptide with microtubule-interacting properties was identified in a Golgi vesicle-enriched fraction from Corylus avellana pollen. The k71s23 antibody (directed to the kinesin heavy chain from bovine brain) [Tiezzi et al., 1992: Cell Motil. Cytoskeleton 21:132-137] localized the polypeptide on the external surface of membrane-bounded organelles. Some 100-kDa-containing vesicles co-pelleted with microtubules (polymerized from purified bovine brain tubulin) either in presence or absence of 5 mM AMPPNP, but they could be released by 10 mM ATP or 0.5 M KCl. The pollen microtubule-interacting protein, salt-extracted from membranes and partially purified by gel filtration, exhibited an ATPase activity (16.2 nmolPi/mg/min) which could be stimulated about 2-fold (32.5 nmolPi/mg/min) by addition of bovine brain microtubules. We suppose that the 100-kDa polypeptide is part of a molecular complex showing properties of the kinesin class. © 1994 Wiley-Liss, Inc.
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    Nanometer scale vibration in mutant axonemes of Chlamydomonas (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 177-185 
    Details
    ISSN: 0886-1544
    Keywords: flagella ; Chalamydomonas ; mutant ; high-frequency vibration ; nanometer scale measurement ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Flagellar axonemes of sea urchin sperm display high frequency (200-400 Hz) vibration with nanometer scale amplitudes in the presence of ATP [Kamimura and Kamiya, 1992: J. Cell Biol. 116:1443-1454]. To investigate how various axonemal components affect the vibration, we examined vibration in wild-type and mutant axonemes of Chlamydomonas. At 1 mM ATP, wild-type axonemes underwent vibration at 100-650 Hz with amplitudes of 4-40 nm. This vibration was similar to, but less regular than, that in sea urchin sperm. Axonemes of the mutants ida1 and ida4 lacking part of the inner arm dynein underwent vibrations indistinguishable from that of wild-type. The mutant oda1 lacking the entire outer arm underwent vibration at about half the wild-type frequency. Unexpectedly, the paralyzed mutants pf18 lacking the central pair and pf14 lacking the radial spokes displayed vibration with significantly higher frequencies and smaller amplitudes than those in the wild-type vibration. These results indicate that the high-frequency vibration is common to many kinds of mutant axonemes that lack various axonemal substructures, but that its manner is sensitive to the presence of outer arm dynein and the central pair/radial spoke system. Simultaneous measurements of amplitude and frequency in wild-type and mutant axonemes suggest that the velocity of microtubule sliding in vibrating axonemes is lower than the velocity of sliding under load-free conditions. The velocity is particularly low in pf18. A possible mechanism is proposed to explain the lower sliding velocity and vibration amplitude in the pf18 axoneme, based on an assumption that central pair/radial spoke system may work to regulate the switching of two antagonizing forces within the axoneme. © 1994 Wiley-Liss, Inc.
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    22S axonemal dynein is preassembled and functional prior to being transported to and attached on the axonemes (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 215-224 
    Details
    ISSN: 0886-1544
    Keywords: cytoplasmic dynein ; Paramecium ; monoclonal antibody ; 12S dynein ; microtubule gliding ; Km and Vmax ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In an earlier study we reported the isolation of a cytoplasmic dynein from the cytosol of Paramecium multimicronucleatum. In this study we report the isolation and characterization of two cytosolic axonemal dyneins (22S and 12S) as well as a 19S cytoplasmic dynein from the cytosol of whole or deciliated cells using preformed bovine brain microtubules. These three dynein species were characterized according to mass, morphology, vanadate photocleavage patterns, CTPase/ATPase ratios, Km and Vmax values, temperature optima and reactivity with a mAb. For comparison, 22S and 12S axonemal dyneins (ADs) were also isolated and purified from the demembranated axonemes. The 22S and 12S soluble dyneins appear to be related to ciliary ADs in that the 22S soluble dynein is three-headed while the 12S is a one-headed dynein, as determined by negative staining. Ciliary ADs and their corresponding 22S and 12S soluble dyneins isolated from the cytosol also have similar Km and Vmax values as well as vanadate photocleavage patterns and temperature optima. A mAb raised against the soluble 22S dynein reacted with the 22S ciliary dyneins but not the 12S axonemal or the 19S cytoplasmic dynein. All isolated dyneins supported similar microtubule gliding rates but had different ionic requirements for the translocation buffer. These results suggest that: (i) the two soluble 22S and 12S dyneins are precursor molecules of the ciliary dyneins, (ii) the subunits of the outer arm dynein are already assembled in the cytosol as a three-headed bouquet, and (iii) the 22S and 12S soluble dyneins are functional prior to being transported and attached to the axonemes of the cilia. © 1994 Wiley-Liss, Inc.
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970290301
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    Phosphoprotein phosphatase 1 (PP1) is a component of the isolated sea urchin mitotic apparatus (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 280-290 
    Details
    ISSN: 0886-1544
    Keywords: mitosis ; phosphorylation ; protein phosphatase ; okadaic acid ; mitotic apparatus ; sea urchin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A protein component of isolated mitotic apparatus having a relative molecular mass of 62,000 (p62) is a substrate of a calcium/calmodulin dependent protein kinase, and the phosphorylation of p62 in vitro correlates directly with microtubule disassembly. In vivo experiments have determined the phosphorylation of p62 increases after fertilization; maximum incorporation of phosphate occurs during late metaphase/early anaphase and decreases thereafter. Because the level of p62 is constant throughout the cell cycle [Johnston and Sloboda, 1992: J. Cell Biol. 119:843-54] the decrease in phosphorylation of p62 observed after anaphase onset is most likely due to the action of a phosphatase. By examination of the relative amount of phosphorylated p62 which remained radiolabeled as a function of time using a standard in vitro phosphorylation assay, the activity of a phosphoprotein phosphatase capable of dephosphorylating p62 in the isolated mitotic apparatus was observed. To characterize the p62 phosphatase, okadaic acid and calyculin A were used to inhibit the dephosphorylation of p62 in vitro. It was found that specific concentrations of okadaic acid (50-500 nM) and of calyculin A (10-100 nM) were effective at inhibiting the dephosphorylation of p62 in vitro. Lower concentrations of either inhibitor had a negligible effect on dephosphorylation of p62. These data indicate the presence of phosphoprotein phosphatase type 1 activity associated with mitotic apparatus isolated from sea urchin embryos using the procedures described here. The implications of these findings relative to our understanding of the regulation of mitosis and cytokinesis are discussed. © 1994 Wiley-Liss, Inc.
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    Gain setting in Chlamydomonas reinhardtii: Mechanism of phototaxis and the role of the photophobic response (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 225-230 
    Details
    ISSN: 0886-1544
    Keywords: Weber's Law ; retinal ; retinal analogs ; photoreception ; alga ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The unicellular green alga Chlamydomonas reinhardtii maintains sensitivity of its phototaxis response (alignment of swimming direction along the axis of a light beam) over several orders of magnitude of light intensities. It is widely accepted that the rotation of the swimming cell provides temporal comparisons of light intensities via periodic contrast generated by its asymmetrically positioned refractile eyespot organelle. The cells also exhibit a second behavioral response to light called the photophobic (or stop) response, which is a brief cessation of swimming caused by a temporal change in light intensity. The cells are desensitized to photophobic stimuli by light exposure. Through comparative measurements of both responses, we explain the behavioral basis of the large dynamic range of phototaxis in terms of precise desensitization of the photophobic response. The basis of the explanation is that the flagellar beat changes which cause phototactic orientation are the residual of the photophobic response after desensitization (i.e., “mini-photophobic” reactions which cause brief reorienting motions without a full stop). This interpretation predicts quantitatively the dependence of the extent of desensitization on light intensity and the dependence of onset and maintenance of phototaxis on extent of desensitization. These predictions are tested and confirmed in this report. © 1994 Wiley-Liss, Inc.
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    Switching of the dominant calcium sequestering protein during skeletal muscle differentiation (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 259-270 
    Details
    ISSN: 0886-1544
    Keywords: calsequestrin ; calreticulin ; sarcoplasmic reticulum ; skeletal muscle ; myofibril ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A major Ca2+-storing protein in endoplasmic reticulum (ER) of non-muscle cells is calreticulin (CR), which is considered to be functionally homologous to calsequestrin. Calsequestrin is a Ca2+-binding protein in sarcoplasmic reticulum (SR) of striated muscle, which stores Ca2+ during muscle relaxation. In order to investigate the expression and distribution of calsequestrin and calreticulin during skeletal muscle differentiation, cultured chick embryonic skeletal muscles were observed by immunofluorescence using anti-calsequestrin, anti-calreticulin, antidesmin, and anti-sarcomeric myosin antibodies and rhodamine-phalloidin. Within 6 hours in culture, myoblasts started to express desmin. Desmin-positive cells demonstrated the reticular staining of calreticulin, as did desmin-negative cells. Around fusion, calsequestrin and sarcomeric myosin started to appear in desmin-positive cells. The expression of calsequestrin slightly preceded that of sarcomeric myosin. As the myotubes matured, the fluorescent dots of calsequestrin increased and spread to the cell periphery along the myofibrils, while the reticular pattern of calreticulin gradually disappeared. Double labeling showed that calsequestrin colocalized with calreticulin. In mature myotubes, anti-calsequestrin staining demonstrated many dots along myofibrils, whereas calreticulin was barely seen except at the perinuclear region. These results suggest that the expression of calsequestrin and calreticulin are switched during skeletal muscle differentiation. © 1994 Wiley-Liss, Inc.
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    Interactions among endoplasmic reticulum, microtubules, and retrograde movements of the cell surface (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 291-300 
    Details
    ISSN: 0886-1544
    Keywords: endoplasmic reticulum ; DiOC6(3) ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Relationships among the endoplasmic reticulum (ER), microtubules, and bead movements on the cell surface were investigated in the thin peripheral region of A6 cells, a frog kidney cell line. ER tubules were often aligned with microtubules, as shown by double-labeling with DiOC6(3) and anti-tubulin in fixed cells. In living cells stained with DiOC6(3) and observed in time lapse, there were frequent extensions, but few retractions, of ER tubules. In addition, there was a steady retrograde (towards the cell center) movement of all of the ER at ∼0.3 μm/min. Since microtubules are often aligned with the ER, microtubules must also be moving retrogradely. By simultaneous imaging, it was found that the ER moves retrogradely at the same rate as aminated latex beads on the cell surface. This indicates that the mechanisms for ER and bead movement are closely related. Cytochalasin B stopped bead and ER movement in most of the cells, providing evidence that actin is involved in both retrograde movements. The ER retracted towards the cell center in nocodazole while both ER and microtubules retracted in taxol. Time lapse observations showed that for both drugs, the retraction of the ER is the result of retrograde movement in the absence of new ER extensions. Presumably, ER extensions do not occur in nocodazole because of the absence of microtubules, and do not occur in taxol because taxol-stabilized microtubules move retrogradely and there is no polymerization of new microtubule tracks for ER elongation. © 1994 Wiley-Liss, Inc.This Article is a US Government work and, as such, is in the public domain in the United States of America.
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    β-actin specific monoclonal antibody (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 108-116 
    Details
    ISSN: 0886-1544
    Keywords: smooth muscle ; fibroblasts ; lamellipodia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using a synthetic peptide mimicking the NH2-terminus of β-actin we have raised a monoclonal antibody specific for this cytoplasmic actin isoform. Specificity of the antibody was demonstrated by its labelling of the actin polypeptide only in tissues containing the β isoform, by its exclusive recognition of the synthetic β-actin peptide amongst those mimicking all six vertebrate isoactins, and by its selective recognition of the β-actin spot in two-dimensional electrophoresis gels of smooth muscle extracts. The antibody bound to actin filaments in both living and fixed fibroblasts where it labelled the stress fiber bundles and, more predominantly, the peripheral actin rich lamellipodia. The characteristics of the antibody indicate that it should serve as a useful tool for studying isoactin distribution and function. © 1994 Wiley-Liss, Inc.
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    Axonemes paralyzed by the presence of dyneins unable to use ribose-modified ATP (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 161-168 
    Details
    ISSN: 0886-1544
    Keywords: fluorescent nucleotide analogs ; methylanthraniloyl ATP ; anthraniloyl ATP ; Chlamydomonas ; axonemal mutants ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Substrate analogs are useful for studying the structures of active sites and for distinguishing between similar enzyme activities. Fluorescent ribose-modified ATP analogs were used to investigate the functional differences between dynein ATPases. These analogs reactivate (support the movement of) sea urchin sperm axonemes, yet they do not reactivate wild-type Chalmydomonas axonemes. Surprisingly, the analogs reactivate the axonemes of mutants completely missing the outer arm dyneins. Competition experiments using ATP and these analogs provide strong evidence that the analogs bind to all dynein active sites but fail to release a subset of dyneins from rigor. We suggest that this subset of Chlamydomonas outer arm dyneins unable to use the analogs remains in rigor in the presence of the analogs and paralyzes the axoneme. © 1994 Wiley-Liss, Inc.
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    ATP-induced sliding of microtubules on tracks of 22S dynein molecules aligned with the same polarity (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 180-191 
    Details
    ISSN: 0886-1544
    Keywords: sliding movement ; 22S dynein ; Tetrahymena cilia ; dynein-track ; singlet microtubule ; ATP ; polarity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chlamydomonas and Tetrahymena axonemal dyneins have previously been found to bind to porcine brain microtubules to produce a microtubule-dynein complex. At appropriate microtubule:dynein concentration, microtubules in the complex became covered to saturation by dynein arms of the same polarity and at a spacing of 24 nm [Haimo et al., 1979; Haimo and Fenton, 1988; Haimo, 1989; Porter and Johnson, 1983a].In the present study, two different types of microtubule-dynein complexes (α-and β-complexes) were prepared from Tetrahymena ciliary 22S dynein and porcine brain tubulin. The characteristics of the adenosine triphosphate (ATP)-induced extrusion of microtubules from these complexes were analyzed, as a simple and direct in vitro assay for the ATP-induced extrusion of single microtubules. The α-complex prepared by adding dynein to microtubules showed an interrupted sliding movement, which would stop and start several times following the addition of ATP. In the β-complex, prepared by adding dynein bound to DEAE-tubulin to pre-assembled microtubules, microtubules became covered with dynein molecules whose orientation and binding were uniform with respect to microtubule polarity. The microtubules in the β-complex extruded at 12 μm/second following the addition of ATP. Dark-field and electron microscopy indicated that the extruded microtubules had undergone sliding on a dynein-track that had become detached from the complexes and had been absorbed onto the surface of the glass slide. At higher light intensity under a dark-field microscope, the dynein-track was seen to be composed of rows of dynein molecules arranged densely. The orientation of dynein molecules in rows appeared to be uniform considering the images of bound dynein in the β-complex under electron microscope. The higher sliding velocity of the microtubules on these dynein-tracks compared to that seen on slides coated at random with dynein [Vale and Toyoshima, 1988, 1989], may be due to more efficient force generation by this dense arrangement of dynein molecules with the same polarity on the tracks. © 1994 Wiley-Liss, Inc.
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    Antisense MAP-2 oligonucleotides induce changes in microtubule assembly and neuritic elongation in pre-existing neurites of rat cortical neurons (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 234-247 
    Details
    ISSN: 0886-1544
    Keywords: microtubule-associated protein 2 ; neurons ; microtubule-associated proteins ; cytoskeleton ; dendrites ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubule-associated protein 2 (MAP-2) is an abundant component of the cytoskeleton present in dendrites and cell bodies of neurons of the CNS. To examine the biological function of MAP-2, two MAP-2 antisense (AS) oligonucleotides complementary to the 5′ region of the rat MAP-2 cDNA were added to rat primary embryonic day 17-18 (E17-18) cultured cortical neurons 24 h after plating and neurite outgrowth and morphology studied. The treatment of primary cortical cultures with either of the two MAP-2 AS oligonucleotides resulted in decreased MAP-2 and reduction in the number of neuritic processes relative to the control or MAP-2 sense-treated cultures. By immunostaining and light microscopy the AS-treated neurons appeared smaller, more rounded, and less intensely stained for MAP-2 than the untreated or the MAP-2 sense-treated cultures. By electron microscopy disorganized microtubules and a reduction in the number of microtubules within neurites of the AS-treated cultures were observed. We conclude that MAP-2 continues to be required for microtubule spacing and stability within neurites once they have formed. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270305
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994) 
    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.970270401
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    Functional analysis of a cardiac myosin rod in Dictyostelium discoideum (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 313-326 
    Details
    ISSN: 0886-1544
    Keywords: myosin II ; cardiac ; sarcomeric ; cytoplasmic myosin ; LMM ; Dd ; heterologous expression ; ConA ; receptor capping ; aggregation ; filament assembly region ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Manipulation of the single conventional myosin heavy chain (mhc) gene in Dictyostelium discoideum (Dd) has delineated an essential role for the filament-forming, or light meromyosin (LMM) domain of the myosin molecule in cyto-kinesis, development, and in the capping of cell surface receptors (see Spudich: Cell Regulation 1:1-11, 1989; Egelhoff et al.: Journal of Cell Biology, 112:677-688, 1991a). In order to assess the functional relationship between sarcomeric and cytoplasmic myosins, a chimeric gene encoding the Dd myosin head and subfragment 2 fused to rat β cardiac LMM was transfected into both wild-type and Dd mhc null cells. Chimeric myosin was organized into dense cortical patches in the cytoplasm of both wild-type and Dd mhc null cells. Although null cells expressing chimeric mhc at ∼10% of Dd mhc levels were unable to grow in shaking suspension or to complete development, chimeric myosin was able to rescue capping of cell surface receptors, to associate with filamentous actin, and to localize to the correct subcellular position during aggregation. Deletion of 29 amino acids in the rod corresponding to a previously defined filament assembly competent region eliminated the cortical patches and the posterior localization during chemotaxis. Taken together, these observations suggest that sarcomeric and cytoplasmic myosin rods are functionally interchangeable in several aspects of nonmuscle motility. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270404
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    Glutamylated tubulin probed in ciliates with the monoclonal antibody GT335 (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 337-349 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; glutamylation ; Paramecium ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubular networks are extensively developped in many ciliate species. In several of them, we investigate the occurrence of the post-translational glutamylation of tubulin [Eddé et al., 1990: Science 247:82-85; Eddé et al., 1991: J. Cell. Biochem. 46:134-142] using as a probe for such modified tubulin, the monoclonal antibody GT335 [Wolff et al., 1992: Eur. J. Cell Biol. 59:425-432]. Results obtained in Paramecium strongly suggest that both axonemal and cytoplasmic tubulin are glutamylated. As in the vertebrate brain tubulin so far tested, the GT335 epitope is located at the carboxy-terminal fragment of cytoplasmic tubulin removed by subtilisin treatment. Immunoblotting and immunofluorescence experiments reveal that, unlike tubulin acetylation, glutamylation is not restricted to cold-resistant microtubules. In addition, immunofluorescence studies performed on dividing cells show that glutamylation takes place soon after the polymerization of microtubules.Finally, glutamylated tubulin is also detected in the ciliate species Euplotes, Tetrahymena, and Paraurostyla. Together with results obtained on flagellate species, this suggests that tubulin glutamylation came out early in the course of eukaryotic evolution and has been widely exploited in various cellular strategies. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270406
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    Actin cytoskeleton and motility in rat sarcoma cell populations with different metastatic potential (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 25-33 
    Details
    ISSN: 0886-1544
    Keywords: actin structures ; vinculin ; focal contacts ; spontaneous metastasis ; extracellular pH ; cell motility ; malignancy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have studied the organisation of the actin cytoskeleton in three related rat sarcoma cell populations of differing malignancy. They were derived by neoplastic progression from a population which had transformed spontaneously in vitro, and were distinguished by their ability to give rise to reproducibly different numbers of metastases, ranging from 10% to 80% of the animals inoculated. We found characteristic differences in the arrangement of the actin cytoskeleton. Confocal three-dimensional microscopy showed that nearly all of the least malignant population contained conspicuous actin stress fibres lying in the lower part of the cell parallel to the substratum and no other actin structures. Actin in the intermediate population was typically situated in a diffuse layer underlying the whole plasma membrane, in which no fibres could be seen. Two thirds of the most malignant population consisted of more rounded cells filled with a three-dimensional network of fine oblique actin fibres. There were focal contacts in all these cells; their area showed a regular decrease from 1.3 μm2 to 0.4 μm2. The differences in actin distribution were accompanied by differences in motility, which increased as malignancy increased. When individual cells were fixed after they had been tracked by time-lapse, their cytoskeleton type correlated with the speed at which they had moved. All these differences were enhanced at low pH. These findings point to the possibility that the three-dimensional network of fine actin fibres in acid culture could be a measure of the malignant potential of transformed cells in vitro. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970280103
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994) 
    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.970280201
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    Purification of microtubule proteins from Xenopus egg extracts: Identification of a 230K MAP4-like protein (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 108-118 
    Details
    ISSN: 0886-1544
    Keywords: Xenopus MAPs ; microtubule cycling ; 230 kDa heat-stable MAP ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We describe the purification of microtubule proteins from Xenopus egg extracts by temperature-dependent assembly and disassembly in the presence of dimethyl sulfoxide and identify a number of presumptive microtubule-associated proteins (MAPs). One of these proteins has a molecular weight of 230 kDa and is immunologically related to HeLa MAP4. We show that this MAP is heat stable and phosphorylated, and that it promotes elongation of microtubules from axonemes. © 1994 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970280203
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    Orientation, assembly, and stability of microtubule bundles induced by a fragment of tau protein (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 143-154 
    Details
    ISSN: 0886-1544
    Keywords: microtubule-associated proteins ; microtubule nucleation ; tubulin ; cytoskeleton ; axon ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The neuronal microtubule-associated protein tau has been implicated in the development of axonal morphology including the organization of microtubules into a uniformly oriented array of microtubules commonly referred to as “bundle.” Determination of the functional organization of tau has revealed that regions of tau protein which flank the microtubule-binding domain affect the bundling of microtubules in vitro with a microtubule-binding fragment of tau being most effective [Brandt and Lee, 1993: J. Biol. Chem. 268:3414-3419]. In order to study the relation of microtubule bundles that form in vitro to those observed in the axon, we determined the orientation of individual microtubules in bundles and the effects of bundling on microtubule assembly and stability in cell-free assembly reactions. Here we report that bundles induced by a microtubule-binding fragment of tau contain randomly oriented microtubules as determined by using the difference in growth rates at microtubule plus and minus ends. We demonstrate that in vitro bundling increases microtubule growth (about 30%), stabilizes microtubules against dilution- and cold-induced disassembly, and allows microtubule nucleation despite the absence of a tau region which has previously been shown to be required for tau-dependent microtubule nucleation. We conclude that conditions that stabilize microtubules can lead to bundle formation and allow microtubule assembly by a mechanism different from that employed by microtubule-associated proteins. The data also support the view that additional mechanisms besides the action of tau and tubulin exist in order to organize microtubules in the axon. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970280206
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    Cytoplasmic dynein binds to phospholipid vesicles (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 205-212 
    Details
    ISSN: 0886-1544
    Keywords: microtubule motor ; organelle transport ; vesicle transport ; liposomes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytoplasmic dynein is the putative motor protein for retrograde organelle transport along microtubules in cells and, thus, must be capable of binding to organelle membranes. Such an attachment may occur via receptor proteins or through a direct interaction of dynein with the membrane phospholipids. We show here that cytoplasmic dynein-synaptic membrane binding does not require a receptor protein and that this binding is mediated by an electrostatic interaction with acidic phospholipids. The properties of cytoplasmic dynein binding to NaOH-extracted synaptic membranes are not significantly affected when those membranes are treated with trypsin to digest endogenous integral membrane proteins. Moreover, purified cytoplasmic dynein is capable of binding to liposomes composed of pure phospholipids. Dynein binds to liposomes with a profile remarkably similar to that of dynein binding to native membranes. Dynein-liposome binding is dependent upon the presence of acidic phospholipids and is disrupted by NaCl. Thus, these studies suggest that electrostatic interactions can effect dynein-membrane binding. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970280304
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