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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 54 (1984), S. 437-445 
    ISSN: 1432-1106
    Keywords: Rat ; Spinal motoneurones ; Recurrent discharge ; Electrical synapse ; In vitro study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The excitatory interaction between spinal motoneurones was investigated by means of electromyogram (EMG) recordings from hindlimb muscles as well as intracellular ones from their innervating motoneurones in the isolated preparation of immature rats. Stimulation of the muscle nerve to biceps femoris or medial gastrocnemius or of the L5 ventral root evoked early and late EMG responses in the muscle of the preparations with the dorsal roots cut. The early response was produced directly by volleys in the motor nerve. The late response was of spinal origin, since it disappeared after the severance of the ventral root. The thresholds and the conduction velocities of nerve fibres, which conducted the centripetal impulse causing the late response, were compatible with those of motor nerve fibres. The amplitude of the late response was 5–10% of that of the maximum early EMG response. Intracellular recordings from spinal motoneurones revealed that stimulation of the ventral root elicited the double discharge composed of antidromic and delayed spike potentials. The delayed spike was never evoked after the spike potential elicited directly by a short depolarizing pulse. The double discharge was observed in about 6% of the motoneurones examined. The threshold of the stimulus intensity evoking the double discharge was in the range of those of motor nerve fibres. The latencies of the delayed excitation were 7.0–9.0 ms, comparable to the intraspinal delays of the late EMG response. Stimulation of the ventral root at intensities subthreshold for antidromic activation was found to produce a small depolarizing potential in about 60% of the motoneurones examined. The amplitudes were 0.5–5.0 mV, and the onset and the peak latencies 2.0–7.0 ms and 5.0–8.0 ms, respectively. The potential was unaffected by the deficiency of calcium ions in the perfusing medium and persisted after the degeneration of the afferent fibres in the ventral root. It was thus concluded that the depolarizing potential was generated by electrical synapses between motoneurones. In a few motoneurones the electrical synaptic potential was found to elicit spike potentials. Latencies of these spikes were similar to those of the delayed excitation in motoneurones with the double discharge. The time course of changes in the excitability in these motoneurones showed that the delayed excitation, hence the late EMG response, was also caused by the electrical synaptic potential.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 29 (1987), S. 389-392 
    ISSN: 1432-1920
    Keywords: Lymphoma ; Limbic system ; Metastasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two cases of metastatic malignant lymphoma confined to the limbic-hypothalamic region are presented. The non-specific nature of the neurological symptoms associated with these lesions such as memory loss, impotence and confusion made neurological localization of the disease process difficult. While non-contrast computed tomography (CT) was unremarkable, contrast CT was diagnostic, showing bilateral homogenous enhancement of specific limbic-hypothalamic structures without significant mass effect. Since lymphomatous involvement of the limbic-hypothalamic area tends to be infiltrative without attendant mass effect, detection of metastasis may be elusive unless special attention is directed to this region. As lymphoma is often chemoresponsive and highly radiosensitive, early recognition of limbic-hypothalamic involvement of this disease is important.
    Type of Medium: Electronic Resource
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