Masato Sibuya

Sensory reinnervation of muscle receptor in human

This report describes sensory reinnervation of muscle receptors in humans. In this study, sensory function was investigated in fourteen patients with brachial plexus injury, whose musculocutaneous nerve was surgically sutured with intercostal nerves for reconstruction of elbow flexion. Tapping the intercostal nerve-reinnervated brachial biceps muscle (IC-biceps) induced somatosensory evoked potentials (IC-biceps SEP) in four patients. Tapping also induced reflex IC-biceps activity in all IC-biceps SEP (+) patients, but not in eight out of nine IC-biceps SEP (-) patients. Results show that muscle afferent fibers in the intercostal nerves reinnervated mechanoreceptors in IC-biceps, and induced both cortical sensory activity and muscle activity that indicated the classical stretch reflex.

Reconstruction of tonic vibration reflex in the biceps brachii reinnervated by transferred intercostal nerves in patients with brachial plexus injury

The transfer of intercostal nerves to musculocutaneous nerves has been performed to reconstruct elbow flexion in patients with brachial plexus injury. In nine of 15 such patients, 2-3 Hz tapping of the distal tendon of the biceps muscle reinnervated by the transferred intercostal nerves (IC-biceps) induced a mode in the correlogram between tap and EMG pulse of IC-biceps. In five of the mode-positive patients, tapping of various frequencies induced gradual augmentation of integrated EMG of IC-biceps. This reflex was consistent with the tonic vibration reflex (TVR) in normal controls. Conduction velocity and frequency property of the reflex were compatible with the speculation that rapid-conducting muscle afferents (group Ia or II or both) reinnervate mechanoreceptors, such as muscle spindles. The clinical significance of muscle sensory reinnervation is not clear; however, the reconstruction of TVR following this operation is worthy in that it confirms the specific sensory reinnervation of denervated muscle in humans.

Two different types of apnea induced by focal cold block of ventral medulla in rabbits

The respiratory effects of unilateral focal cold block of ventral medulla were examined in rabbits. Focal cooling of the paraolivar region in the caudal area of ventral medulla induced prolongation of the expiratory time, with little change in the tidal inspiratory activity amplitude, leading to temporal apnea. Whereas focal cooling of the region ventral to the retrofacial nucleus in the rostral part of the ventral medulla induced depression of tidal phrenic nerve activity amplitude, leading to suppression apnea. Thus, two different types and regions of apnea were demonstrated in rabbits.

Inhibitory effect of acupuncture on the finger flexion reflex induced by finger tip vibration

The effect of acupuncture on finger flexion reflex, caused by mechanical vibration applied to the finger tip, was studied by using the cross-correlation function. A stainless steel acupuncture needle was inserted into the acupuncture point called Wai-Kuan for 10 min. Acupuncture inhibited the reflex and suppressed the two modes seen in the cross-correlogram between unitary EMG activity of the muscle flexor digitorum superficialis and finger tip vibration with random frequency. The recovery of the primary mode, which may be via the spinal monosynaptic reflex loop, was significantly earlier than the recovery of the secondary mode, which may be via the supraspinal reflex long loop. This suggests that the distinct inhibitory effect of acupuncture takes place on the reflex at spinal and supraspinal levels.

Difference in electromyographic response of finger flexion muscles between tonic vibration reflex and finger flexion reflex induced by finger tip vibration

Vibratory stimulus applied to the skin of the finger tip induced flexion reflex in that finger. By using the cross-correlation function, characteristics of this reflex were compared to those of tonic vibration reflex (TVR). In the cross-correlogram between unitary electromyogram (EMG) activity in the muscle flexor digitorum superficialis and vibratory stimulus with random frequency, one mode was seen in TVR, and two modes in finger flexion reflex. The secondary mode was significantly wider than the primary mode. Thus it may originate from skin mechanoreceptors and manifest via a reflex center involving a long loop.

Cross-correlation between vagal afferent impulses from pulmonary mechanoreceptors and high-frequency inflation (HFI) and deflation (HFD) in rabbits

The effects of high-frequency airway inflation (HFI) and high-frequency airway deflation (HFD) generated by a triangular pressure pulse generator on pulmonary mechanoreceptors were examined. The cross-correlograms between vagal afferent impulses from the slowly adapting (SAR) and the rapidly adapting receptors (RAR) and the HFI or the HFD pulses were analysed. HFI stimulated SAR and RAR and HFD stimulated RAR, but inhibited SAR. The time lag of the mode in the correlogram between SAR and HFI was shorter than that of the mode in the correlogram between RAR and HFI. The span of the mode and the trough of SAR was shorter than the span of the mode of RAR. This may indicate that the time to peak of the generator potential of RAR is longer than that of SAR.

Pre-inspiratory burst in the caudal medulla of rabbits

The activity of 48 respiratory units in the paraolivary region from the middle to the rostral end of the hypoglossal cranial nerve root, and the effect of electrical stimulation and L-glutamate applied to the region on phrenic nerve activity was investigated in 14 rabbits. Electrical stimulation (50 Hz, 0.2 ms current pulses at intensities 5-20 microA) and L-glutamate (30-100 ng) shortened the expiratory time and increased the respiratory rhythm with no change in tidal phrenic nerve activity. Rhythmic activity preceding the phrenic nerve activity (pre-inspiratory burst) was recorded in the paraolivary region. The temporal relationship between the pre-inspiratory (pre-I) burst and the phrenic activity remained constant even when the respiratory frequency was altered by passive lung inflation. These results suggest that structures in the paraolivary region may influence the respiratory rhythm in rabbits and that pre-I burst neurons may play a role in triggering periodic phrenic activity.

Expiratory Activity Recorded During Exercise from Human M. Biceps Brachii Reinnervated by Internal Intercostal Nerves

In 1972, Clark and von Euler1 proposed the inspiratory off-switch theory to explain the relationship between inspiratory activity and duration. It was proposed that the inspiratory activity is terminated, and inspiratory duration (TI) is determined when the tidal inspiratory activity reaches a certain off-switch level. One major difference between the study of inspiratory and expiratory activities is that the volume curve does not give as much information on expiratory activity as it does on inspiratory activity. Thus, direct measurements from the expiratory neuromuscular units are necessary to study the relationship between expiratory activity and duration. This is possible in brachial plexus injury (root avulsion type) patients who have undergone the intercostal transfer operation.2 From the studies of the expiratory activity in both humans and lab animals, an “expiratory off-switch mechanism” has been proposed. This mechanism is considered to be an independent system from the inspiratory off-switch system.2,3,4 Another substage within the second stage of expiration (E2 stage)5 has been defined from the onset of the tidal expiratory activity to the suppression of the expiratory activity by the off-switch mechanism. Masato Sibuya would like to dedicate this paper to his grandmother, Raku Sibuya, who passed away during the time of the Oxford Meeting. This was designated the stage of active expiration (Ea stage).2