Mutual oligosynaptic inhibition of group Ia afferents between the anterior and posterior parts of the deltoid in humans.

The anterior (DA) and posterior parts of the deltoid (DP) show alternating contraction during shoulder flexion and extension movements. It is expected that an inhibitory spinal reflex between the DA and DP exists. In this study, spinal reflexes between the DA and DP were examined in healthy human subjects using post-stimulus time histogram (PSTH) and electromyogram averaging (EMG-A). Electrical conditioning stimulation was delivered to the axillary nerve branch that innervates the DA (DA nerve) and DP (DP nerve) with the intensity below the motor threshold. In the PSTH study, the stimulation to the DA and DP nerves inhibited (decrease in the firing probability) 31 of 54 DA motor units and 31 of 51 DP motor units. The inhibition was not provoked by cutaneous stimulation. The central synaptic delay of the inhibition between the DA and DP nerves was 1.5 ± 0.5 ms and 1.4 ± 0.4 ms (mean ± SD) longer than those of the homonymous facilitation of the DA and DP, respectively. In the EMG-A study, conditioning stimulation to the DA and DP nerves inhibited the rectified and averaged EMG of the DP and DA, respectively. The inhibition diminished with tonic vibration stimulation to the DA and DP and recovered 20-30 min after vibration removal. These findings suggest that oligo(di or tri)-synaptic inhibition mediated by group Ia afferents between the DA and DP exists in humans.

Monosynaptic facilitation of motoneurons innervating intrinsic hand muscles mediated by group Ia afferents from the extensor carpi radialis in humans.

The projection pattern of low-threshold afferents from the extensor carpi radialis (ECR) to motoneurons supplying intrinsic hand muscles was investigated using the post-stimulus time-histogram (PSTH) and electromyogram-averaging (EMG-A) methods. Electrical conditioning stimulation was applied to the radial nerve branch innervating the ECR. In the PSTH study, changes in the firing probability of single motor units following the stimulation were examined. An early and significant peak (facilitation) was induced in the motoneurons innervating the muscles, but the facilitation was induced infrequently. The central latency of the facilitation was equivalent to that of homonymous facilitation through monosynaptic path in the spinal cord. In the EMG-A study, changes in the rectified and averaged electromyograms following the conditioning stimulation were examined. An early and significant peak (facilitation) was also induced. The facilitation disappeared after withdrawal of the vibration to the ECR muscle belly. Cutaneous nerve stimulation overlaying ECR never induced such facilitation in the PSTH and EMG-A studies. These findings suggest that monosynaptic facilitation mediated by group Ia afferents of ECR to the motoneurons supplying intrinsic hand muscles exists in humans, but the connection seems to be weak. This weakness might allow manipulatory movements of the hand.

Monosynaptic facilitation of flexor digitorum superficialis motoneurons mediated by Group Ia afferents from the extensor carpi radialis in humans.

Wrist position is known to affect the grip strength. We focused on the spinal reflex arc, which would support the movement, and investigated the effects of low-threshold afferents from the extensor carpi radialis (ECR) on the excitability of the flexor digitorum superficialis (FDS) motoneurons using the post-stimulus time-histogram (PSTH) and electromyogram-averaging (EMG-A) methods. Electrical conditioning stimulation of an intensity below the motor threshold was applied to the radial nerve branch innervating the ECR. In the PSTH study, changes in the firing probability of single motor units after electrical conditioning stimulation were investigated in seven subjects. An early and significant peak (increase in the firing probability: facilitation) was recorded for 36/60 FDS motor units. The remaining 24 motor units did not show any effects. Weak mechanical conditioning stimulation of the ECR muscle belly induced a similar peak. The central latency of the facilitation was equivalent to that of the homonymous monosynaptic facilitation. In the EMG-A study, changes in the rectified and averaged electromyograms of FDS induced by conditioning stimulation were examined in 12 subjects. An early and significant peak (facilitation) was induced by both electrical and mechanical conditioning stimulations. The facilitation decreased after withdrawal of the vibration to the ECR muscle belly. The facilitation was never induced by cutaneous nerve stimulation in the PSTH and EMG-A studies. These findings suggest that Group Ia afferents from the ECR increase the excitability of FDS motoneurons through a monosynaptic path in the spinal cord. These reflex arcs likely facilitate hand grasping movements.

Monosynaptic facilitation mediated by group Ia afferents from deltoid to biceps brachii motoneurons in humans.

Effects of low-threshold afferents from the anterior (DA), middle (DM) and posterior parts of the deltoid (DP) on the excitability of biceps brachii (BB) motoneurons in humans were studied. We evaluated the effects on individual motor units and motoneuron pool using a post-stimulus time-histogram (PSTH) and an electromyogram-averaging (EMG-A) methods, respectively, in 11 healthy human subjects. Electrical conditioning stimulation was delivered to the axillary nerve branch innervating DA (DA nerve), DM (DM nerve) and DP (DP nerve) with the intensity below the motor threshold. In the PSTH study, stimulation to the DA, DM and DP nerves produced a significant peak (facilitation) in 26/40 (65%), 28/47 (59%) and 0/32 (0%) of BB motor units, respectively. Since the central latency of the facilitation from the DA and DM nerves was 0.1 ± 0.3 and 0.1 ± 0.2 ms (mean ± S.D.) longer than that of the homonymous monosynaptic Ia facilitation of BB, respectively, the facilitation thus being compatible with monosynaptic path. In the EMG-A study, stimulation to the DA and DM nerves produced a significant peak (facilitation) for the BB motoneuron pool in all the subjects, whereas stimulation to the DP nerve produced no effect on BB. The facilitation diminished by vibration stimulation, and the suppression lasted for 30-40 min after removal of the vibration. Therefore, group Ia afferents should be responsible for the facilitation. These findings suggest that monosynaptic facilitation mediated by group Ia afferents from the DA and DM nerves to BB motoneurons exists in humans.

Vibration decreases the responsiveness of Ia afferents and spinal motoneurons in humans.

After vibration, Hoffmann reflex (H reflex) amplitude is depressed; however, the mechanisms underlying these phenomena remain unknown. This study investigated the influence of frequency and duration of vibration on the H reflex amplitude, heteronymous facilitation of the tendon jerk (T wave) mediated by group Ia afferents, and cervicomedullary motor evoked potential (CMEP) amplitude in 18 healthy human subjects. The H reflex of the flexor carpi radialis (FCR) was induced by median nerve stimulation at the elbow, and the conditioning FCR stimulation enhanced the T wave of the biceps brachii (BB). After vibration was applied to the FCR muscle belly, the amplitudes of the H reflex and heteronymous facilitation of the T wave were depressed; these influences persisted after the removal of vibration in all subjects. For the H reflex, there was no difference in the amount of depression among the frequencies of vibration used (57, 77, and 100 Hz). Higher frequencies of vibration were associated with longer recovery times of postvibration depression, and a longer duration of vibration was associated with a longer recovery time of the depression. Similar results were observed for heteronymous facilitation of the T wave, suggesting that the depression is caused by a decrease in postsynaptic potentials evoked by Ia afferents in spinal motoneurons; it was probably due to reduction in the number of Ia afferents recruited by the median nerve stimulation. Moreover, because the FCR CMEP amplitude was depressed after vibration, vibration should affect the responsiveness of spinal motoneurons. These mechanisms are considered to contribute to the H reflex depression after vibration.NEW & NOTEWORTHY Vibration decreased the responsiveness of Ia afferents from the muscle exposed to vibration, and the duration of depressive effect was modulated by the duration and frequency of the vibration: a longer duration and a higher frequency of vibration led to a longer recovery time of the depression. In addition to this presynaptic effect, it also depressed the responsiveness of spinal motoneurons, indicating postsynaptic inhibition through specific circuits triggered by Ia impulses.

Oligosynaptic inhibition mediated by group Ia afferents from flexor digitorum superficialis to wrist flexors in humans.

Effects of low-threshold afferents from the flexor digitorum superficialis (FDS) to the flexor carpi radialis (FCR), flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) motoneurons were examined using a post-stimulus time-histogram (PSTH) and electromyogram-averaging (EMG-A) methods in seven healthy human subjects. Electrical conditioning stimulation to the median nerve branch innervating FDS with the intensity immediately below the motor threshold was delivered. In the PSTH study, the stimulation produced a trough (inhibition) in 19/44 (43%) of FCR and 17/41 (41%) of FCU motor units. Remaining motor units received no facilitatory and inhibitory effects. The central latency of the inhibition was 1.1 ± 0.6 ms (mean ± SD) and 0.6 ± 0.4 ms longer than that of the homonymous monosynaptic Ia facilitation of FCR and FCU, respectively. In the EMG-A study, the stimulation produced a trough (inhibition) in EMG-A of FCR and FCU in all the seven subjects. Amount of the inhibition was 14.5 ± 3.8% (FCR) and 17.9 ± 2.5% (FCU). Since the inhibition diminished after withdrawal of tonic vibration stimuli to the FDS muscle belly, group Ia afferents should be responsible for the inhibition. The stimulation did not produce facilitatory or inhibitory effect on ECU motoneurons in both the PSTH and EMG-A studies. These findings suggest that group Ia afferents from FDS inhibit excitability of motoneurons supplying FCR and FCU through an oligo (di- or tri-) synaptic path in the spinal cord. The reflex arcs would function to prevent wrist flexion during hand grasping movements.

Inhibition of Group Ia Afferents Between Brachioradialis and Flexor Carpi Radialis in Humans: A Study Using an Electromyogram-Averaging Method.

PURPOSE: Our previous studies using a poststimulus time histogram method demonstrated inhibitory spinal reflex arcs (inhibition) between the brachioradialis (BR) and flexor carpi radialis (FCR) in humans. Group I afferents mediated the inhibition through an oligosynaptic path. In this study, effects of the inhibition on excitability of the motoneuron pools were examined, and we tried to clarify which afferents of group Ia or Ib are responsible for the inhibition. METHODS: We evaluated the effects of low-threshold afferents between BR and FCR on FCR and BR motoneuron pools, respectively, using an electromyogram-averaging method in 14 healthy human subjects. Changes of rectified and averaged electromyogram of BR by electrical conditioning stimulation with the intensity below the motor threshold to the median nerve branch innervating FCR (FCR nerve) and those of FCR by the stimulation to the radial nerve branch innervating BR (BR nerve) were evaluated. RESULTS: The stimulation to the FCR and BR nerves produced an early and significant trough of rectified and averaged electromyogram of BR and FCR, respectively, in all the subjects. The amount of inhibition of BR and FCR was 13.2 ± 3.4% (mean ± SD) and 14.2 ± 1.4%, respectively. The trough of BR and FCR diminished by tonic vibration stimuli to a respective FCR and BR. Such a trough was never provoked by cutaneous stimulation. CONCLUSIONS: The inhibition between BR and FCR depresses excitability of the FCR and BR motoneuron pools, respectively. Group Ia afferents should mediate the inhibition.

Oligosynaptic inhibition of group Ia afferents from brachioradialis to triceps brachii motor neurons in humans.

INTRODUCTION: This study examines effects of low-threshold afferents from the brachioradialis (BR) on excitability of triceps brachii (TB) motor neurons in humans. METHODS: We evaluated the effects using a post stimulus time histogram (PSTH) and electromyogram averaging (EMG-A) methods in 13 healthy human participants. Electrical conditioning stimulation to the radial nerve branch innervating BR with the intensity below the motor threshold was delivered. RESULTS: In the PSTH study, the stimulation produced a trough (inhibition) in 36/69 TB motor units for all the participants. A cutaneous stimulation never provoked such inhibition. The central latency of the inhibition was 1.5 ± 0.5 ms longer than that of the homonymous facilitation. In the EMG-A study, the stimulation produced inhibition in EMG-A of TB in all participants. The inhibition diminished with a tonic vibration stimulation to BR. DISCUSSION: These findings suggest that oligosynaptic inhibition mediated by group Ia afferents from BR to TB exists in humans. Muscle Nerve 57: 122-128, 2018.

Monosynaptic facilitation of group I afferents between brachioradialis and extensor carpi radialis in humans.

Spinal reflex arcs mediated by low-threshold (group I) afferents from muscle spindles and Golgi tendon organs modulate motoneuron excitabilities to coordinate smooth movements. In this study, the reflex arcs between the brachioradialis (BR) and extensor carpi radialis muscles (ECR) were examined in nine healthy human subjects using a post-stimulus time-histogram method. Electrical conditioning stimuli (ES) to the radial nerve branches innervating BR (BR nerve) and ECR (ECR nerve) with the intensity just below the motor threshold were delivered and firings of the ECR and BR motor units were recorded in 6 and 7 of the nine subjects, respectively. ES to the BR and ECR nerves induced a peak (facilitation) in 27/59 ECR and 22/68 BR motor units, respectively, in every subject. Such facilitation was never provoked by pure cutaneous stimulation. The remaining motor units received no effects by ES. The central synaptic delay of the facilitation was almost equal to that of the homonymous facilitation. These findings suggest that facilitation between BR and ECR exists in humans. Group I afferents should mediate the facilitation through a monosynaptic path in the spinal cord.

Oligosynaptic inhibition of group I afferents between the brachioradialis and flexor carpi radialis in humans.

Spinal reflex arcs mediated by low threshold afferents between the brachioradialis (BR) and flexor carpi radialis (FCR) were studied in eleven healthy human subjects using a post-stimulus time-histogram method. Electrical conditioning stimuli (ES) to the radial nerve branch innervating BR with the intensity below the motor threshold (MT) induced an early and significant trough (inhibition) in 32/85 FCR motor units (MUs) in 9/9 subjects. Such inhibition was never provoked by cutaneous stimulation. The central synaptic delay (CSD) of the inhibition was approximately 1.1ms longer than that of the homonymous FCR facilitation. ES to the median nerve branch innervating FCR with the intensity below MT induced an inhibition in 27/71 BR-MUs in 10/10 subjects. CSD of the inhibition was about 1.1ms longer than that of the homonymous BR facilitation. These findings suggest that inhibition between BR and FCR exists in humans. Group I afferents seem to mediate the inhibition through an oligo(di or tri)-synaptic path.

Facilitation from flexor digitorum superficialis to extensor carpi radialis in humans.

Effects of low-threshold afferents from the flexor digitorum superficialis (FDS) to the extensor carpi radialis (ECR) motoneurons were examined using a post-stimulus time-histogram (PSTH) and electromyogram-averaging (EMG-A) methods in eight healthy human subjects. In the PSTH study in five of the eight subjects, electrical conditioning stimuli (ES) to the median nerve branch innervating FDS with the intensity below the motor threshold induced excitatory effects (facilitation) in 39 out of 92 ECR motor units. In 11 ECR motor units, the central synaptic delay of the facilitation was -0.1 ± 0.3 ms longer than that of the homonymous facilitation of ECR. Mechanical conditioning stimuli (MS) to FDS with the intensity below the threshold of the tendon(T)-wave-induced facilitation in 51 out of 51 ECR motor units. With the EMG-A method, early and significant peaks were produced by ES and MS in all the eight subjects. The difference between latencies of the peaks by ES and MS was almost equivalent to that of the Hoffmann- and T-waves of FDS by ES and MS. The peak was diminished by tonic vibration stimuli to FDS. These findings suggest that a facilitation from FDS to ECR exists in humans and group Ia afferents mediate the facilitation through a monosynaptic path.

Complete Genome Sequence of the Porcine Epidemic Diarrhea Virus Variant Tottori2/JPN/2014.

Porcine epidemic diarrhea virus (PEDV) is a cause of diarrhea outbreaks at swine farms, causing vomiting, severe diarrhea, and mortality in piglets. We sequenced and analyzed the complete genome of recently isolated strains. Tottori2/JPN/2014, one of the sequenced PEDV strains, had a unique large deletion in the S gene.

Strict actions of the human wrist flexors: A study with an electrical neuromuscular stimulation method.

In order to elucidate strict actions of the human wrist flexors, motion and force produced by electrical neuromuscular stimulation (ENS) to each of musculus (m.) flexsor carpi radialis (FCR) and m. flexsor carpi ulnaris (FCU) with the prone, semiprone, and supine forearm were studied in ten healthy human subjects. Abduction, extension, adduction, and flexion directions were represented by, respectively, 0°, 90°, 180°, and 270°. ENS to FCR and FCU produced motion in direction of, respectively, 273° (mean) and 265° with the prone, 249° and 232° with the semiprone, and 242° and 229° with the supine forearm to the maximal range. Direction/strength (Nm) of force by ENS to FCR and FCU were, respectively, 298°/1.16 and 239°/1.70 with the prone, 279°/1.30 and 241°/1.62 with the semiprone, and 267°/1.24 and 227°/2.04 with the supine forearm. ENS to FCR exhibited force of 20-29% of maximal flexion and 7-15% of maximal abduction or 1-4% of maximal adduction and that to FCU force of 24-28% of maximal flexion and 15-25% of maximal adduction. The force study results suggest that FCU is a flexor rather than an adductor with every forearm position. FCR should be a flexor rather than an abductor with the prone and semiprone and a flexor with the supine forearm. The action of FCR as the abductor should diminish with supinating the forearm.

Identification of region-specific transcription factor genes in the adult mouse brain by medium-scale real-time RT-PCR.

We established a medium-scale real-time RT-PCR system focusing on transcription factors and applied it to their expression profiles in the adult mouse 11 brain regions (http://genome.gsc.riken.jp/qRT-PCR/). Almost 90% of the examined genes showed significant expression in at least one region. We successfully extracted 179 region-specific genes by clustering analysis. Interestingly, the transcription factors involved in the development of the pituitary were still expressed in the adult pituitary, suggesting that they also play important roles in maintenance of the pituitary. These results provide unique molecular markers that may account for the molecular basis of the unique functions of specific brain regions.