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  • 1
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    German Medical Science; Düsseldorf, Köln
    In:  67. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie, 89. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie und 44. Tagung des Berufsverbandes der Fachärzte für Orthopädie; 20031111-20031116; Berlin; DOC03dguO18-6 /20031111/
    Publication Date: 2003-11-11
    Keywords: ddc: 610
    Language: German
    Type: conferenceObject
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  • 2
    Keywords: PROTEINS ; TYPE-1 ; ORGANIZATION ; FILAMENTS ; POLYMERIZATION ; SPREAD ; HOST-CELLS ; NATURAL-PRODUCT ; CYTOSKELETON DYNAMICS ; HIV-1 PARTICLES
    Abstract: Human immunodeficiency virus type 1 (HIV-1) particles assemble at the plasma membrane, which is lined by a dense network of filamentous actin (F-actin). Large amounts of actin have been detected in HIV-1 virions, proposed to be incorporated by interactions with the nucleocapsid domain of the viral polyprotein Gag. Previous studies addressing the role of F-actin in HIV-1 particle formation using F-actin-interfering drugs did not yield consistent results. Filamentous structures pointing toward nascent HIV-1 budding sites, detected by cryo-electron tomography and atomic force microscopy, prompted us to revisit the role of F-actin in HIV-1 assembly by live-cell microscopy. HeLa cells coexpressing HIV-1 carrying fluorescently labeled Gag and a labeled F-actin-binding peptide were imaged by live-cell total internal reflection fluorescence microscopy (TIR-FM). Computational analysis of image series did not reveal characteristic patterns of F-actin in the vicinity of viral budding sites. Furthermore, no transient recruitment of F-actin during bud formation was detected by monitoring fluorescence intensity changes at nascent HIV-1 assembly sites. The chosen approach allowed us to measure the effect of F-actin-interfering drugs on the assembly of individual virions in parallel with monitoring changes in the F-actin network of the respective cell. Treatment of cells with latrunculin did not affect the efficiency and dynamics of Gag assembly under conditions resulting in the disruption of F-actin filaments. Normal assembly rates were also observed upon transient stabilization of F-actin by short-term treatment with jasplakinolide. Taken together, these findings indicate that actin filament dynamics are dispensable for HIV-1 Gag assembly at the plasma membrane of HeLa cells. Importance: HIV-1 particles assemble at the plasma membrane of virus-producing cells. This membrane is lined by a dense network of actin filaments that might either present a physical obstacle to the formation of virus particles or generate force promoting the assembly process. Drug-mediated interference with the actin cytoskeleton showed different results for the formation of retroviral particles in different studies, likely due to general effects on the cell upon prolonged drug treatment. Here, we characterized the effect of actin-interfering compounds on the HIV-1 assembly process by direct observation of virus formation in live cells, which allowed us to measure assembly rate constants directly upon drug addition. Virus assembly proceeded with normal rates when actin filaments were either disrupted or stabilized. Taken together with the absence of characteristic actin filament patterns at viral budding sites in our analyses, this indicates that the actin network is dispensable for HIV-1 assembly.
    Type of Publication: Journal article published
    PubMed ID: 24789789
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Advances in Space Research 12 (1992), S. 141-147 
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Ultramicroscopy 42-44 (1992), S. 290-297 
    ISSN: 0304-3991
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0304-3991
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Rapid eye movements ; Vertical gaze centre ; Burst neurons ; Reversible inactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The role of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) in generating the vertical and torsional components of rapid eye movements was examined. The on-directions of burst neurons in the riMLF of alert Rhesus monkeys were obtained during quick phase nystagmus in three dimensions. The distinguishing feature of these burst neurons was the torsional component of their on-directions; neurons on the right side exhibited a clockwise component, from the point of view of the subject, while those on the left had a counterclockwise component. Vertical components could have up or down directions. This organization was verified by means of unilateral reversible inactivation of the riMLF using Muscimol. An injection in the right riMLF impaired the generation of quick phases with clockwise components while one on the left impaired counterclockwise components.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1106
    Keywords: Eye movements ; Translational motion ; Ocular following ; Viewing distance ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent experiments on monkeys have indicated that the eye movements induced by brief translation of either the observer or the visual scene are a linear function of the inverse of the viewing distance. For the movements of the observer, the room was dark and responses were attributed to a translational vestibulo-ocular reflex (TVOR) that senses the motion through the otolith organs; for the movements of the scene, which elicit ocular following, the scene was projected and adjusted in size and speed so that the retinal stimulation was the same at all distances. The shared dependence on viewing distance was consistent with the hypothesis that the TVOR and ocular following are synergistic and share central pathways. The present experiments looked for such dependencies on viewing distance in human subjects. When briefly accelerated along the interaural axis in the dark, human subjects generated compensatory eye movements that were also a linear function of the inverse of the viewing distance to a previously fixated target. These responses, which were attributed to the TVOR, were somewhat weaker than those previously recorded from monkeys using similar methods. When human subjects faced a tangent screen onto which patterned images were projected, brief motion of those images evoked ocular following responses that showed statistically significant dependence on viewing distance only with low-speed stimuli (10°/s). This dependence was at best weak and in the reverse direction of that seen with the TVOR, i.e., responses increased as viewing distance increased. We suggest that in generating an internal estimate of viewing distance subjects may have used a confounding cue in the ocular-following paradigm the size of the projected scene -which was varied directly with the viewing distance in these experiments (in order to preserve the size of the retinal image). When movements of the subject were randomly interleaved with the movements of the scene to encourage the expectation of ego-motion -the dependence of ocular following on viewing distance altered significantly: with higher speed stimuli (40°/s) many responses (63%) now increased significantly as viewing distance decreased, though less vigorously than the TVOR. We suggest that the expectation of motion results in the subject placing greater weight on cues such as vergence and accommodation that provide veridical distance information in our experimental situation: cue selection is context specific.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1041
    Keywords: Key words Drug Information Centre ; Primary healthcare
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1106
    Keywords: Vestibular neurectomy ; Velocity storage ; Single cell ; Integrator ; Optokinetic ; Smooth pursuit ; Labyrinthectomy ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary After destruction of the peripheral vestibular system which is not activated by moving large-field visual stimulation, not only labyrinthine-ocular reflexes but also optokinetic-ocular responses related to the “velocity storage” mechanism are abolished. In the normal monkey optokinetic-ocular responses are reflected in sustained activity changes of central vestibular neurons within the vestibular nuclei. To account for the loss of optokinetic responses after labyrinthectomy, inactivation of central vestibular neurons consequent on the loss of primary vestibular activity is assumed to be of major importance. To test this hypothesis we recorded the neural activity within the vestibular nuclear complex in two chronically prepared Rhesus monkeys during a period from one up to 9 and 12 months after both vestibular nerves had been cut. The discharge characteristics of 829 cells were studied in relation to eye fixation, and to a moving small and large (optokinetic) visual stimulus producing smooth pursuit (SP) eye movements and optokinetic nystagmus (OKN). Units were grouped into different subclasses. After chronic bilateral vestibular neurectomy (BVN) we have found: (1) a rich variety of spontaneously active cells within the vestibular nuclear complex, which — as far as comparison before and after BVN is possible — belong to all subclasses of neurons functionally defined in normal monkey; and (2) no sustained activity changes which are related to the activation of the “velocity storage” mechanism; this is especially true for “pure-vestibular”, “vestibular-pause” and “tonic-vestibular-pause” cells in normal monkey which show a “pure”, “pause” and “tonic-pause” firing pattern after BVN. Neurons which are modulated by eye position are, however, modulated with the velocity of slow eye movements with comparable sensitivity during SP and OKN. Retinal slip is extremely rarely encoded. The results of the present study do not directly answer the question why the “velocity storage” mechanism is abolished after BVN but they suggest that only a small number of central vestibular cells may be inactivated by neurectomy.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1076
    Keywords: Key words Breastfeeding ; Supplementary feeding ; Neonatal ; Bottles ; Pacifier use
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To promote breastfeeding, UNICEF/WHO have launched the “baby-friendly hospital initiative” focusing on hospital care routines during delivery and the first days of life. In industrialised countries, two aspects of the initiative have raised controversy: how do restriction of supplemental feedings and ban of bottles and pacifiers affect long-term breastfeeding performance? From ten centres 602 healthy newborns were randomly assigned either to a UNICEF group with restrictive fluid supplements and avoidance of bottles and pacifiers during the first 5 days of life, or to a standard group with conventional feeding practice. Breastfeeding was encouraged in both groups. The main study endpoints were the prevalences of breast-feeding on day 5, and after 2, 4 and 6 months. Of the newborns 46% violated the UNICEF protocol, mostly because of maternal requests to give a pacifier or supplements by bottle. In the standard group, the drop-out rate was 9.7%. No significant differences in breastfeeding frequency and duration could be found: (UNICEF vs standard) day 5: 100% vs 99%; 2 months: 88% vs 88%; 4 months: 75% vs 71%; 6 months: 57% vs 55%. Inclusion of drop-outs due to pacifier use did not alter the results. Conclusion In our study population fluid supplements offered by bottle with or without the use of pacifiers during the first 5 days of life were not associated with a lower frequency or shorter duration of breastfeeding during the first 6 months of life.
    Type of Medium: Electronic Resource
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