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  • Acoustic startle response  (2)
  • Intravital microscopy  (2)
  • 1
    ISSN: 1432-2277
    Keywords: Key words Xenogeneic liver hemoperfusion ; Intravital microscopy ; Fucoidin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Since the main feature of hyperacute rejection is a disturbance of the xenograft's microcirculation, we analyzed microhemodynamic parameters during xenogeneic hemoperfusion of the guinea pig (GP) liver and investigated the contribution of leukocytes to the rejection process using intravital fluorescence microscopy. Isolated GP livers were hemoperfused via the portal vein in a recirculating system with a constant flow of 1 ml/min per g liver. In contrast to isogeneic perfusion with heparinized GP blood, a disturbance in the microcirculation was observed during xenogeneic perfusion using heparinized rat blood, with significantly higher values of perfusion pressure, reduced sinusoidal perfusion rates, and a larger number of stagnant leukocytes. A complete breakdown of the microcirculation, with the highest values of perfusion pressure and the smallest perfusion index, was associated with 100 % accumulated leukocytes when rat blood was anticoagulated with sodium citrate. Almost isogeneic perfusion values were obtained when fucoidin, which inhibits L-selectin-dependent cell interaction, was added to heparinized rat blood. These data indicate that leukocyte-endothelial cell interaction contributes to xenogeneic rejection.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2277
    Keywords: Key words Xenotransplantation ; liver ; intravital microscopy ; Liver transplantation ; xenografting ; hemoperfusion ; intravital microscopy ; Intravital microscopy ; liver transplantation ; xenografting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The main targets of xenogeneic rejection mechanisms are the endothelial cells of the graft. Their activation and the consequent alteration of the organ's microcirculation lead to the destruction of the xenograft. Microhemodynamic changes occurring during this process are still poorly characterized. The aim of this study was to analyze the microcirculation during xenogeneic ex vivo hemoperfusion of rat livers and to monitor the impact of treatment strategies using intravital fluorescence microscopy. In contrast to the isogeneic control group, blood flow almost completely stopped within the first minutes of xenoperfusion. Simultaneously, perfusion pressure increased and bile production was reduced. Acetylsalicylate (Aspisol) and the platelet-activating factor antagonist WEB 2170 improved the microcirculation and function of the xenoperfused liver. The combination showed a synergistic effect. After apheresis of preformed xenogeneic antibodies, the parameters measured were comparable with those seen in isogeneic experiments. Complement degradation with cobra venom factor revealed a minor improvement in perfusion. A rapid, extensive, and irreversible leukocyte accumulation in terminal portal vessels was observed in all xenogeneic experiments. Blood counts of the perfusate confirmed the early trapping of leukocytes and platelets in the xenoperfused liver, indicating nonimmunological, cellular involvement in this rejection process.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-3297
    Keywords: Acoustic startle response ; sensitization ; amygdala ; Roman high- and low-avoidance rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract To investigate the emotional reactions of two rat strains selectively bred for good and poor two-way avoidance acquisition (RHA/Verh and RLA/Verh), male animals of both strains were tested in an acoustic startle response test. They received 40 acoustic stimuli followed by 10 electric foot shocks and another 30 acoustic stimuli. RLA/Verh rats showed a significantly higher startle response compared to RHA/Verh animals, indicating a stronger emotional reaction to acoustic stimuli. In addition, the former showed a stronger response to foot shocks. Combined with earlier findings, we conclude that selection for two-way avoidance learning does not result in cognitive defects in the RLA/Verh strain but, rather, in stronger emotional reactions to fearful stimuli.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-3297
    Keywords: Acoustic startle response ; habituation ; sensitization ; fear ; genetic differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract An increase in general responsiveness after aversive stimulation has provided a most widely accepted and well-understood sensitization paradigm. According to a second paradigm (based on the dual process theory of habituation and sensitization), not only additional aversive stimuli, but also the response-eliciting stimuli themselves, induce sensitization. To relate these two sensitization paradigms, we compared the course of startle response parameters during repetitive acoustic stimulation with the change in startle amplitude after electric footshocks in outbred Wistar and Sprague–Dawley rats. Compared to the Wistar rats used, the Sprague–Dawley rats showed a lower response decrement and a shortened latency during repetitive stimulation, both of which are indicators of increased sensitization by the startle-eliciting stimuli. In addition, the Sprague–Dawley rats also demonstrated a reduced increase in startle amplitude following footshock. This was postulated to be a consequence of the strong sensitization by startle-eliciting stimuli, which interferes with sensitization elicited by footshock. Because our Wistar and Sprague–Dawley rats did not differ in initial startle amplitude, but mainly in susceptibility to sensitization, further comparisons of these genetically different stocks of rats seem to be of potential value in studying differences in fear-motivated behavior.
    Type of Medium: Electronic Resource
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