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  • Electromyographic activity  (2)
  • AUTOIMMUNE DISEASES  (1)
  • 1
    ISSN: 1432-1106
    Schlagwort(e): Postural reflexes ; Unexpected postural perturbations ; Electromyographic activity ; Muscle synergies ; Motor control ; Hindlimb muscles ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effect of the direction of unexpected horizontal perturbations of stance on the organization of automatic postural responses was studied in cats. We recorded EMG activity in eight proximal and distal muscles of the hindlimb along with vertical forces imposed by the limbs in awake behaving cats while they stood on an hydraulic platform. Postural responses to motion of the platform in 16 different horizontal directions were recorded. Vertical force changes were consistent with passive shifts of the center of mass and active correction of stance by the animals. When the perturbation was in the sagittal plane, vertical force changes began about 65 ms following initial platform movement. When the perturbation contained a component in the lateral direction, latency for vertical force changes was about 25 ms and an inflection in the vertical force trace was observed at 65 ms. No EMG responses were observed with latencies that were short enough to account for the early force component and it was concluded that this force change was due to passive shifts of the center of mass. The amplitude of the EMG responses of each muscle recorded varied systematically as perturbation direction changed. The directions for which an individual muscle showed measurable EMG activity were termed the muscle's “angular range of activation.” No angular range of activation was oriented strictly in the A-P or lateral directions. Most muscles displayed angular ranges of activation that encompassed a range of less than 180°. Onset latencies of EMG responses also varied systematically with perturbation direction. The amplitude and latency relationships between muscles, which made up the organization of postural responses, also varied systematically as perturbation direction was changed. This result suggests that direction of perturbation determines organizational makeup of postural responses, and for displacements in the horizontal plane, is considered a continuous variable by the nervous system.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 73 (1988), S. 648-658 
    ISSN: 1432-1106
    Schlagwort(e): Unexpected postural perturbations ; Electromyographic activity ; Muscle synergies ; Motor control ; Human ; Automatic postural responses
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effect of the direction of unexpected horizontal perturbations of stance on the organization of automatic postural responses was studied in human subjects. We recorded EMG activity from eight proximal and distal muscles acting on joints of the legs and hip known to be involved in postural corrections, while subjects stood on an hydraulic platform. Postural responses to horizontal motion of the platform in 16 different directions were recorded. The amplitude of the EMG responses of each muscle studied varied continuously as perturbation direction was changed. The directions for which an individual muscle showed measurable EMG activity were termed the muscle's “angular range of activation”. There were several differences in the response characteristics of the proximo-axial muscles as opposed to the distal ones. Angular ranges of activity of the distal muscles were unipolar and encompassed a range of less than 180°. These muscles responded with relatively constant onset latencies when they were active. Proximo-axial muscles, acting on the upper leg and hip showed larger angular ranges of activation with bimodal amplitude distributions and/ or onset latency shifts as perturbation direction changed. While there were indications of constant temporal relationships between muscles involved in responses to perturbations around the sagittal plane, the onset latency relationships for other directions and the response amplitude relationships for all directions varied continuously as perturbation direction was changed. Responses were discrete in that for any particular perturbation direction there appeared to be a single unique response. Thus, while the present results do not refute the hypothesis that automatic postural responses may be composed of mixtures of a few elemental synergies, they suggest that composition of postural responses is a complex process that includes perturbation direction as a continuous variable.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Digestive diseases and sciences 43 (1998), S. 2149-2155 
    ISSN: 1573-2568
    Schlagwort(e): AUTOIMMUNE DISEASES ; FEMALE GENDER ; IMMUNE PHENOTYPE
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Immune disorders in chronic liver disease mayreflect common host propensities or diseasespecificfactors. Our aim was to determine the principal basesfor these expressions. Four hundred fifty-one patients with various chronic liver diseases wereassessed prospectively for concurrent immune disorders.Individuals with immune diseases were more frequentlywomen (73% vs 60%, P = 0.02) and they had HLA DR4 more often than counterparts with other HLA(46% vs 23%, P = 0.000008). The association between HLADR4 and immune disease was apparent within individualliver diseases and within different categories of liver disease. Women with HLA DR4 had ahigher frequency of immune disease than women withoutHLA DR4 (52% vs 22%, P ≤ 0.000001), and they also hadimmune diseases more commonly than DR4-positive men (52% vs 31%, P = 0.03). DR4-positive men,however, had higher frequencies of immune disease thanDR4-negative men, especially in the nonimmune types ofliver disease (26% vs 4%, P = 0.002). We conclude that HLA DR4 and female gender constitute animmune phenotype that is an important basis forautoimmune expression in chronic liverdisease.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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