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Biomedical subjects

I Homma

Publications and source records attributed to I Homma.

At least 91 records · Page 5Linked to original sources
PubMed1988

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.

Animals↗
PubMed1988

Primary respiratory rhythm generator in the medulla of brainstem-spinal cord preparation from newborn rat.

It has been previously demonstrated that rhythmically firing neurons (Pre-I neurons) preceding cervical root (C4 or C5) inspiratory activity, localized in the rostral ventrolateral medulla (RVL), are important in the generation of the basic respiratory rhythm in brainstem-spinal cord preparations from newborn rats. We examined the effects of single and continuous electrical stimulation applied to the RVL on Pre-I and C4 activities in these preparations. We verified that the phase of respiratory rhythm was reset when Pre-I firing was induced in both right and left RVL by single shock stimulation, whether C4 activity appeared or not. Lower frequency and intensity of continuous pulse train stimulation in the RVL enhanced Pre-I activity, and hence C4 activity, whereas higher frequency and intensity inhibited both. The results suggest that synchronous burst activity between the right and left Pre-I neurons must be above a certain level (in its intraburst firing rate) to trigger C4 inspiratory activity and, therefore, that cooperation among Pre-I neurons is important for induction of rhythmic inspiratory drive. After bilateral lesions of the caudal ventrolateral medulla, Pre-I neurons retained their rhythmic activity, while C4 activity disappeared. Present results further confirmed our hypothesis that Pre-I neurons are the primary generator of respiratory rhythm. We propose a hypothetical model of the generation of rhythmic respiratory activity.

Animals↗
PubMed1988

Thermode for deep focal cooling.

A cooling thermode is described that can be used to reversibly lesion deep structures with minimal penetration damage. Construction, associated equipment, and use of this thermode are simpler and less expensive, and it can be made smaller in size, than previously described thermodes. The user has a choice of a simple, inexpensive control arrangement that is somewhat more complicated to use, or a more expensive control system that is simpler to use. The diameter of this thermode can be at least as small as 0.3 mm, which is smaller than any previously described thermode. The cooling agent, Co2, is used in such small quantities that toxicity is no problem.

Animals↗
PubMed1988

Effects of high-frequency inflation (HFI) on expiratory activity.

It has been reported that triangular-shaped positive pressure pulses applied to the airway (high-frequency inflation, HFI) stimulates pulmonary stretch receptors and prolongs expiratory duration. In the present experiment, changes in the integrated curve of expiratory activity induced by HFI were investigated. Duration until the onset of the expiratory activity (E1 stage) was unchanged. In the E2 stage, the initial ascending slope became steeper and higher peaks were reached during HFI stimulation. The period from the onset of the slope to the peak, previously designated the stage of active expiration (Ea stage), showed no consistent change in duration and remained unchanged on average. The period after the peak until the onset of the following inspiratory activity was consistently prolonged. This period was designated the declining stage of expiration (Ed stage).

Afferent Pathways↗
PubMed1987

Localization of respiratory rhythm-generating neurons in the medulla of brainstem-spinal cord preparations from newborn rats.

We describe the location of Pre-I neurons, which are important to respiratory rhythm generation, in the rostral medulla of brainstem-spinal cord preparations isolated from newborn rats. This neuronal group was delimited in the reticular formation slightly medial to the caudal area of the facial nucleus and near the ventral surface. The effects of electrical stimulation and lesions in that region were also examined with respect to respiratory rhythm generation. Single shock stimulation induced Pre-I neuron firing and reset the phase of the respiratory rhythm. Electrolytic lesions in the Pre-I neuron region reduced the respiratory rate.

Animals↗
PubMed1987

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.

Adaptation, Physiological↗
PubMed1987

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.

Adult↗
PubMed1987

Respiratory rhythm generator neurons in medulla of brainstem-spinal cord preparation from newborn rat.

Rhythmic neuronal activity preceding C4 inspiratory activity (Pre-I neuron activity) was recorded in rostral ventrolateral (near ventral surface) medulla of brainstem-spinal cord preparation isolated from newborn rat. Vagal stimulation inhibited C4 activity but not Pre-I neuron activity. Rhythmic Pre-I neuron-like activity was still recorded in the block of rostral medulla after transection. Results suggest that Pre-I neurons generate the basic respiratory rhythm and trigger inspiratory activity.

Animals↗
PubMed1987

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.

Action Potentials↗
PubMed1987

Expiratory activity in transferred intercostal nerves in brachial plexus injury patients.

Involuntary activity of transferred intercostal motor units was examined in patients with brachial plexus injury. Since the internal intercostal nerves were detached from the thorax to reinnervate the musculus biceps brachii, it was possible to record pure intercostal motor activity in humans. Respiratory activity was seen in the latter part of the expiratory phase, thus dividing the phase into two substages (E1 and E2) by the onset of the activity. CO2 rebreathing prolonged the duration of the intercostal motor activity and increased the tidal activity as determined from the integration curve. There was a close linear correlation between these two variables. These observations indicate that expiratory activity and its duration are actively controlled in humans.

Adult↗
PubMed1985

The effects of high-frequency inflation and high-frequency deflation on respiration in rabbits.

High-frequency inflating and deflating triangular pulses of pressure were applied to air in the trachea of urethane-chloralose-anesthetized rabbits. Expiratory time was increased by high-frequency inflation (HFI) and decreased by high-frequency deflation (HFD). Both had little effect on inspiratory time or tidal phrenic nerve activity. HFD provoked more tonic type phrenic activity, with discharges being evident during the expiratory phase. It was demonstrated that HFI, which probably stimulates pulmonary stretch receptors, inhibits the initiation of inspiration and HFD, which probably stimulates irritant receptors, facilitates inspiration.

Animals↗
PubMed1985

Cardiorespiratory arrest in a patient with advanced diabetic autonomic neuropathy.

A 53-year-old diabetic woman who had been diabetic for 14 years had recurrent episodes of cardiorespiratory arrest, which were easily resuscitated by a few chest massages. In 2 of 4 episodes a radial pulse was detected, so respiratory arrest was thought to be a primary event. Pentazocine was injected several hours prior to each of the 3 episodes. This was considered to be a precipitating factor. From the first episode of cardiorespiratory arrest, she received oxygen inhalation. When oxygen inhalation was withdrawn for 5-10 min, she became cyanotic. This was considered to be a sign of lack of hypoxic drive mediated by peripheral chemoreceptors. Ventilatory responses to hypercapnia was markedly decreased, indicating impaired central chemosensitivity. The possibility that impaired chemosensitivity could be a cause of respiratory arrest was suggested.

Autonomic Nervous System Diseases↗
PubMed1984

Effects of histamine inhalation and airway vibration on phrenic nerve activity in rabbits.

Experiments were performed on 8 rabbits under urethane-chloralose anesthesia. Histamine aerosol (5%) administered into the trachea by a cannula produced tonic activity of the phrenic nerve, with discharges also being evident during the expiratory phase. Airway vibration (100 Hz) inhibited this tonic activity and caused silence during the expiratory phase.

Adaptation, Physiological↗
PubMed1984

Facilitation of inspiration by intracerebroventricular injection of thyrotropin-releasing hormone in rabbits.

Effects of fourth cerebroventricular injection of thyrotropin-releasing hormone (TRH) on respiration were studied in vagotomized rabbits. Phrenic neural activity was recorded and integrated. TRH (1.0 microgram) injection facilitated phrenic neural activity and increased respiratory rate. Peak phrenic nerve activity increased slightly or showed no apparent changes when tonic activity appeared. Tidal phrenic neural activity either increased or decreased, depending on relations between peak phrenic activity and tonic activity. Results suggest that TRH facilitates central respiratory activity to induce tonic activity and increase respiratory rate.

Animals↗
PubMed1984

Gate mechanism in breathlessness caused by chest wall vibration in humans.

The effects of bilateral alternating out-of-phase vibrations were studied in 10 normal healthy subjects and five asthmatic patients. The second or third intercostal spaces were vibrated during expiration, and the seventh to ninth intercostal spaces were vibrated during inspiration. Most subjects sensed breathlessness during such vibrations, and 100 Hz was most effective. The degree of breathlessness correlated positively with increased respiratory rate. Respiratory rate increased from 14.1 +/- 3.78 (mean +/- SD) to 22.3 +/- 7.14 breaths/min (P less than 0.05) during relatively severe breathlessness and to 20.39 +/- 5.66 breaths/min (P less than 0.05) during less uncomfortable sensation. Slight or negligible breathlessness induced no significant increase in rate (15.33 +/- 4.19 breaths/min). All asthma patients described the sensations during vibration as similar to those during asthma attacks, and their respiratory rates increased 20.7 +/- 11.03% during 100 Hz vibration (P less than 0.01). It is suggested that the uncomfortable sensation of breathlessness may be induced by muscle spindles in the intercostal muscles being activated out of phase with the respiratory cycle. The central mechanism that receives the intercostal afferents may have a certain gate that operates in relation to the sensation of breathlessness.

Adult↗
PubMed1983

Reinforcement of tonic vibration reflex and exteroceptive vibration-induced flexion reflex in finger flexion muscles by forced respiration.

The effects of forced respiration on tonic vibration reflex (TVR) and exteroceptive vibration-induced flexion reflex (VFR) were studied in healthy man. vibration (100 Hz) applied to finger flexion muscles or the volar side of the middle finger induced a slowly augmenting facilitation of the TVR, which has mono-and polysynaptic components, and VFR, which is polysynaptic. Forced inspiration and forced expiration facilitated these slowly augmenting processes in both reflexes. Respiration reinforces both proprioceptive and exteroceptive reflexes elicited by vibration.

Adult↗