RESUMEN
Objective To explore the resonant frequencies of human spinal motor neurons.Methods Twenty healthy college students were recruited as the subjects.Each was put in a supine position and administered vibratory stimulation at 20 Hz,30 Hz,40 Hz,50 Hz and 60 Hz on the left distal fibula just above the lateral malleolus for 5 minutes.M-waves and F-waves were recorded before each intervention.F-waves were also recorded immediately after each intervention.Results The F-wave amplitude and the F/Mmax ratio after the 30 Hz stimulation were significantly larger than those at baseline and after stimulation at 50 or 60 Hz.However,20 Hz,30 Hz and 40 Hz stimulation produced no significantly different F-wave amplitudes or F/Mmax.Conclusion Human spinal motor neurons may have a resonant frequency around 30 Hz.
RESUMEN
To evaluate the effect of midkine (MK), neurotrophic factor on cultured mouse spinal motor neuron, NSC-19 which was inhibited by glucose oxidase (GO)-induced oxygen radicals, MTT assay and neurofilament enzymeimmunoassay were carried out after NSC-19 cells were preincubated with various concentrations of midkine for 2 hours prior to exposure of glucose oxidase. The results were as follows : 1. MK increased the rate of cell viability and neurofilamental development in a dose-dependent manner on motoneurons inhibited by glucose oxidase-induced oxygen radicals. 2. MTT50 value was 25 mU/ml GO. 3. GO-induced oxygen radicals were toxic on cultured motor neurons in a time and dose-dependent manner. 4. GO-induced oxygen radicals induced the decrease of cells in number and the loss of neurites in cultured mouse spinal motor neurons. From above the results, it is concluded that oxygen radicals are toxic in cultured mouse spinal motor neurons, and selective neurotrophic factors such as MK enhance the viability of motor neurons inhibited by oxygen radicals.