Dynamical study of Νaν channel excitability under mechanical stress.

Alteration of [Formula: see text] channel functions (channelopathies) has been encountered in various hereditary muscle diseases. [Formula: see text] channel mutations lead to aberrant excitability in skeletal muscle myotonia and paralysis. In general, these mutations disable inactivation of the [Formula: see text] channel, producing either repetitive action potential firing (myotonia) or electrical dormancy (flaccid paralysis) in skeletal muscles. These "sick-excitable" cell conditions were shown to correlate with a mechanical stretch-driven left shift of the conductance factors of the two gating mechanisms of a fraction of [Formula: see text] channels, which make them firing at inappropriate hyperpolarised (left-shifted) voltages. Here we elaborate on a variant of the Hodgkin-Huxley model that includes a stretch elasticity energy component in the activation and inactivation gate kinetic rates. We show that this model reproduces fairly well sick-excitable cell behaviour and can be used to predict the parameter domains where aberrant excitability or paralysis may occur. By allowing us to separate the incidences of activation and inactivation gate impairments in [Formula: see text] channel excitability, this model could be a strong asset for diagnosing the origin of excitable cell disorders.

[Observation of deaf-mute students' audition examine and otacoustic effect].

OBJECTIVE: To explore the state of the remnant hearing of deaf-mute students and to check the effect of hearing aids to them. METHOD: 38 cases of deaf and dumb students were examined with the pure tone auditometry, acoustic immitance test, auditory brainstem response, and the environmental sound discrimination test. RESULT: In 17 cases, the average threshold of air conduction of speech frequency is below 89 dB HL; In 18 cases, it is between 90 dB and 110 dB; In 3 cases, it is above 110 dB. 33 cases have model A curve and 5 cases have model B curve. When 123 dB peSPL was presented, 24 cases generated the waveform but the others didn't. 16 cases could discriminate the environmental sound and the other 22 cases could not, but if the patients weared the hearing aids, the number of the persons who could discriminate the environmental sound increased to 24, only 14 cases had no effect by this means. CONCLUSION: Examination of deaf-mutes audition can find persons with residual audition. If they wear the hearing aids and go into hearing rehabilitation training at the same time as early as possible, it will improve the environmental sound discrimination rate.