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  • Other Sources  (32)
  • 2000-2004  (6)
  • 1985-1989  (26)
  • 1
    Publication Date: 2011-08-24
    Description: Myotonic dystrophy protein kinase (DMPK) is a serine-threonine protein kinase encoded by the myotonic dystrophy (DM) locus on human chromosome 19q13.3. It is a close relative of other kinases that interact with members of the Rho family of small GTPases. We show here that the actin cytoskeleton-linked GTPase Rac-1 binds to DMPK, and coexpression of Rac-1 and DMPK activates its transphosphorylation activity in a GTP-sensitive manner. DMPK can also bind Raf-1 kinase, the Ras-activated molecule of the MAP kinase pathway. Purified Raf-1 kinase phosphorylates and activates DMPK. The interaction of DMPK with these distinct signals suggests that it may play a role as a nexus for cross-talk between their respective pathways and may partially explain the remarkable pleiotropy of DM.
    Keywords: Life Sciences (General)
    Type: FEBS letters (ISSN 0014-5793); Volume 475; 3; 273-7
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  • 2
    Publication Date: 2011-08-24
    Description: DMPK, the product of the DM locus, is a member of the same family of serine-threonine protein kinases as the Rho-associated enzymes. In DM, membrane inclusions accumulate in lens fiber cells producing cataracts. Overexpression of DMPK in cultured lens epithelial cells led to apoptotic-like blebbing of the plasma membrane and reorganization of the actin cytoskeleton. Enzymatically active DMPK was necessary for both effects; inactive mutant DMPK protein did not produce either effect. Active RhoA but not constitutive GDP-state mutant protein produced similar effects as DMPK. The similar actions of DMPK and RhoA suggest that they may function in the same regulatory network. The observed effects of DMPK may be relevant to the removal of membrane organelles during normal lens differentiation and the retention of intracellular membranes in DM lenses. Copyright 2000 Wiley-Liss, Inc.
    Keywords: Life Sciences (General)
    Type: Cell motility and the cytoskeleton (ISSN 0886-1544); Volume 45; 2; 133-48
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  • 3
    Publication Date: 2011-08-24
    Description: Muscle thick filaments are highly organized supramolecular assemblies of myosin and associated proteins with lengths, diameters and flexural rigidities characteristic of their source. The cores of body wall muscle thick filaments of the nematode Caenorhabditis elegans are tubular structures of paramyosin sub-filaments coupled by filagenins and have been proposed to serve as templates for the assembly of native thick filaments. We have characterized alpha- and gamma-filagenins, two novel proteins of the cores with calculated molecular masses of 30,043 and 19,601 and isoelectric points of 10.52 and 11.49, respectively. Western blot and immunoelectron microscopy using affinity-purified antibodies confirmed that the two proteins are core components. Immunoelectron microscopy of the cores revealed that they assemble with different periodicities. Immunofluorescence microscopy showed that alpha-filagenin is localized in the medial regions of the A-bands of body wall muscle cells whereas gamma-filagenin is localized in the flanking regions, and that alpha-filagenin is expressed in 1.5-twofold embryos while gamma-filagenin becomes detectable only in late vermiform embryos. The expression of both proteins continues throughout later stages of development. C. elegans body wall muscle thick filaments of these developmental stages have distinct lengths. Our results suggest that the differential assembly of alpha- and gamma-filagenins into thick filaments of distinct lengths may be developmentally regulated.
    Keywords: Life Sciences (General)
    Type: Journal of cell science (ISSN 0021-9533); Volume 113 ( Pt 22); 4001-12
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  • 4
    Publication Date: 2011-08-24
    Description: In the thick filaments of body muscle in Caenorhabditis elegans, myosin A and myosin B isoforms and a subpopulation of paramyosin, a homologue of myosin heavy chain rods, are organized about a tubular core. As determined by scanning transmission electron microscopy, the thick filaments show a continuous decrease in mass-per-length (MPL) from their central zones to their polar regions. This is consistent with previously reported morphological studies and suggests that both their content and structural organization are microdifferentiated as a function of position. The cores are composed of a second distinct subpopulation of paramyosin in association with the alpha, beta, and gamma-filagenins. MPL measurements suggest that cores are formed from seven subfilaments containing four strands of paramyosin molecules, rather than the two originally proposed. The periodic locations of the filagenins within different regions and the presence of a central zone where myosin A is located, implies that the cores are also microdifferentiated with respect to molecular content and structure. This differentiation may result from a novel "induced strain" assembly mechanism based upon the interaction of the filagenins, paramyosin and myosin A. The cores may then serve as "differentiated templates" for the assembly of myosin B and paramyosin in the tapering, microdifferentiated polar regions of the thick filaments.
    Keywords: Life Sciences (General)
    Type: Journal of molecular biology (ISSN 0022-2836); Volume 305; 5; 1035-44
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  • 5
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 24; 1802-181
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  • 6
    Publication Date: 2011-08-19
    Description: The application of layered synthetic microstructures (LSMs) to figured mirrors suitable for normal incidence solar EUV telescopes is considered, and initial studies for a single mirror telescope consisting of an f/18, 200-cm focal length off-axis paraboloid demonstrate the feasibility of LSM coatings for moderate sized mirrors. Analytical studies on broadband designs comprised of five layers show a seven percent reflectance at 256 A and reflectivities of over 12 percent for wavelengths above 300 A. Deposition considerations are also discussed.
    Keywords: ASTRONOMY
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  • 7
    Publication Date: 2011-08-19
    Description: The wakes of highly loaded compressor blades are generally considered to be turbulent flows. Recent work has suggested that the blade wakes are dominated by a vortex streetlike structure. The experimental evidence supporting the wake vortex structure is reviewed. This structure is shown to redistribute thermal energy within the flowfield. The effect of the wake structure on conventional aerodynamic measurements of compressor performance is noted. A two-dimensional, time-accurate, viscous numerical simulation of the flow exhibits both vortex shedding in the wake and a lower-frequency flow instability that modulates the shedding. The numerical results are shown to agree quite well with the measurement from transonic compressor rotors.
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 4; 236-244
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  • 8
    Publication Date: 2017-10-02
    Description: The wakes of highly loaded axial compressor blades were often considered to be turbulent, unstructured flows. Recent work has suggested that the blade wakes are in fact dominated by a vortex street-like structure. The work on the wake structure at MIT is reviewed, the results of a viscous numerical simulation are presented, the blade wake vortices are compared to those shed from a cylinder, and the implications of the wake structure on compressor performance are discussed. In particular, a two-dimensional, time accurate, viscous calculation shows both a periodic wake structure and time variations in the passage shock strength. The numerical calculations are compared to laser anemometer and high frequency response probe data. The effect of the wake structure on the entropy production and apparent adiabatic efficiency of the compressor rotor is discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AGARD Transonic and Supersonic Phenomena in Turbomachines; 13 p
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  • 9
    Publication Date: 2019-06-28
    Description: A strategy is proposed for controlling aerodynamic instabilities which limit the useful range of both axial and centrifugal turbomachines. Both local and global instabilities (incipient rotating stall and surge) are analyzed. A theory is developed which shows how an additional disturbance, driven from real time data measured within the machine, can be generated so as to realize a device with characteristics fundamentally different from those of the turbomachine without control; for the particular compressor analyzed, the control led to a 20 percent increase in the extent of the stable operating range. The use of structural dynamics to enhance stability is also discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-1914
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  • 10
    Publication Date: 2019-06-28
    Description: High-frequency response probes which had previously been used exclusively in the MIT Blowndown Facility were successfully employed in two conventional steady state axial flow compressor facilities to investigate the unsteady flowfields of highly loaded transonic compressors at design point operation. Laser anemometry measurements taken simultaneously with the high response data were also analyzed. The time averaged high response data of static and total pressure agreed quite well with the conventional steady state instrumentation except for flow angle which showed a large spread in values at all radii regardless of the type of instrumentation used. In addition, the time resolved measurements confirmed earlier test results obtained in the MIT Blowdown Facility for the same compressor. The results of these tests have further revealed that the flowfields of highly loaded transonic compressors are heavily influenced by unsteady flow phenomena. The high response measurements exhibited large variations in the blade to blade flow and in the blade passage flow. The observed unsteadiness in the blade wakes is explained in terms of the rotor blades' shed vorticity in periodic vortex streets. The wakes were modeled as two-dimensional vortex streets with finite size cores. The model fit the data quite well as it was able to reproduce the average wake shape and bi-modal probability density distributions seen in the laser anemometry data. The presence of vortex streets in the blade wakes also explains the large blade to blade fluctuations seen by the high response probes which is simply due to the intermittent sampling of the vortex street as it is swept past a stationary probe.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-176879 , NAS 1.26:176879
    Format: application/pdf
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