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  • 1
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: p25, a degradation product of p35, has been reported to accumulate in the forebrain of patients with Alzheimer's disease. p25 as well as p35 are activators of cyclin-dependent kinase 5 (Cdk5) although p25/Cdk5 and p35/Cdk5 complexes have distinct properties. Several mouse models with high levels of p25 expression exhibit signs of neurodegeneration. On the contrary, we have shown that low levels of p25 expression do not cause neurodegeneration and are even beneficial for particular types of learning and memory [Angelo et al., (2003) Eur J. Neurosci., 18, 423–431]. Here, we have studied the influence of low-level p25 expression in hippocampal synaptic plasticity and in learning and memory for each sex separately in two different genetic backgrounds (129B6F1 and C57BL/6). Surprisingly, we found that low-level p25 expression had different consequences in male and female mutants. In the two genetic backgrounds LTP induced by a strong stimulation of the Schaffer's collaterals (four trains, 1-s duration, 5-min interval) was severely impaired in male, but not in female, p25 mutants. Furthermore, in the two genetic backgrounds spatial learning in the Morris water maze was faster in female p25 mutants than in male transgenic mice. These results suggest that, in women, the production of p25 in Alzheimer's disease could be a compensation for some early learning and memory deficits.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 267 (1977), S. 717-719 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A total of 54 single motor units were studied in the first interosseus muscle of the hand in five normal adult subjects. Highly selective bipolar electrodes were inserted through the skin and carefully positioned in the muscle belly so as to pick up selectively the action potentials of two to five ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Human Movement Science 5 (1986), S. 217-233 
    ISSN: 0167-9457
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine , Sports Science
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 77 (1989), S. 94-102 
    ISSN: 1432-1106
    Keywords: Eye movement ; Brainstem ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study maps the eye movements evoked by microstimulations in the medulla of 9 alert cats. Trains of square waves (20 μA amplitude, 0.2 msec duration, 200 Hz) were delivered through glass-covered tungsten microelectrodes (0.5–1 MΩ). Movements of both eyes were recorded by the magnetic field/eye coil technique. Stimulation of the prepositus hypoglossi nucleus (PH) evoked nystagmus with ipsilaterally-directed slow phases followed by after-nystagmus with contralaterally-directed slow phases. Stimulation of the medial vestibular nucleus (MVN) induced nystagmus whose slow phases were more often ipsilaterally-directed but at time contralaterally-directed. At nearly all sites where we stimulated the reticular formation underlying prepositus and vestibular nuclei (from P4.5 to P12), we recorded versional conjugate movements. They were most often ipsilaterally-directed. Some microstimulations in the region of the medial longitudinal fasciculus evoked recentering eye movements: regardless of the initial position of the gaze (to the left as well as to the right), microstimulations given at the same place induced a movement of both eyes toward their neutral position. The amplitude of this movement was proportional to the eccentricity of the pre-stimulation position of the gaze.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 49 (1983), S. 28-34 
    ISSN: 1432-1106
    Keywords: Vestibular ; Ocular ; Optokinetic ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ocular movements of naive and adapted cats were recorded by classical electronystagmography techniques during: (1) sinusoidal vestibular stimulation, (2) sinusoidal optokinetic stimulation, (3) sinusoidal additive visual-vestibular stimulation, and (4) sinusoidal conflicting visual-vestibular stimulation. Adaptation of the horizontal vestibulo-ocular reflex (VOR) was produced in adult cats by sustained combined sinusoidal rotation of the cat and its surroundings (fixed-field conditions). This procedure was applied for four hours for four consecutive days. On the fifth day the VOR in darkness, the OKR, the VOR in the light and the visual suppression of the VOR were studied. VOR gain decreased from day to day and some relative frequency-specificity emerged. The gain of the visually inhibited VOR also diminished after training. This change was also frequency-specific. OKN gain, tested by a set of sinusoidal rotations, was found to be virtually unchanged. In the naive cat, VOR modified by the visual stimulus (fixed or moving) could be computed by an algebraic summation of the VOR and OKR eye movement compensations. After training, the gain of the VOR in situations where the VOR was interacting with the OKR remained easily predictable by the algebraic summation of the isolated VOR and OKR compensations.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Key words Vestibular system ; Labyrinthectomy ; Vestibular compensation ; Neck muscles ; Vestibulocollic reflex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In the guinea pig, lateral deviation of the head is a cardinal symptom of the vestibular syndrome caused by unilateral labyrinthectomy. In the course of recovery from this syndrome (vestibular compensation), lateral deviation of the head disappears completely in 2–3 days. Because this symptom is known to be due to the lesion of the horizontal semicircular canal system, and since obliquus capitis inferior (OCI) muscle is activated predominantly by yaw rotation (horizontal vestibulocollic reflex), we hypothesized that changes in the activity of this muscle could be at least in part responsible for the lateral head deviation caused by unilateral labyrinthectomy. In order to test this hypothesis, electromyographic (EMG) activities of the right and left OCI muscles, as well as eye movements, were recorded in 12 head-fixed alert guinea pigs at various times after left surgical labyrinthectomy (performed with the animals under halothane anesthesia). After the operation, a decrease in tonic EMG activity was observed in the right (contralateral to the lesion) OCI muscle while an increase in tonic EMG activity was detected in the left (ipsilateral) OCI muscle. In addition, phasic changes in EMG activity associated with ocular nystagmic beats occurred in the OCI muscles. These phasic changes were in the opposite direction to those of the tonic changes. There were bursts of activity in the right OCI and pauses in the left OCI. From measurements of rectified averaged EMG activities which took into account both parts (tonic and phasic) of the phenomenon, it was concluded that the labyrinthectomy-induced asymmetry between the activities of the left and right OCI muscles was high enough and lasted long enough to be an important mechanism in the lateral deviation of the head caused by unilateral labyrinthectomy.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 50 (1984), S. 135-141 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract After a brief comparative review of the dynamic characteristics of the optokinetic reflex (OKR) in different species and after a brief description of the main anatomical structures involved in this reflex, a mathematical model of the OKR in the cat is presented. The experimental results obtained by Godaux and Vanderkelen (1984) in the normal and in the totally cerebellectomized cat were used to validate the model and to obtain an estimation of its parameters.
    Type of Medium: Electronic Resource
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