Biomedical subjects
I Homma
Publications and source records attributed to I Homma.
[Contractile dysfunction and alteration of PKC activity in gastric smooth muscle of diabetic rats].
Explore the source record for details and available documents.
Central mediation of tracheal pressure through H1 and H2 receptors after histamine administration to the fourth ventricle of anesthetized rabbit.
Administration of 1.5, 5.0 and 15 nmol histamine (HA) into the fourth ventricle (IVth) decreased tracheal pressure (PT) dose-dependently in anesthetized rabbits. Maximum decrease of PT occurred 0.9 +/- 0.1 min (mean +/- S.E.M., n = 9) after administration of 15 nmol, and recovery occurred at 4.5 +/- 1.0 min (n = 9). The decrease of PT was blocked by the H1 receptor antagonist, pyrilamine administration into the IVth, or intravenous injection of the alpha-adrenoceptor antagonist, phentolamine. Recovery from the PT decrease was delayed by the H2 receptor antagonist, cimetidine. The results suggest that HA centrally decreases PT through H1 receptors, which action is mediated by the sympathetic nervous system, and this decrease may be modulated through H2 receptors.
Contractile hyperreactivity and alteration of PKC activity in gastric fundus smooth muscle of diabetic rats.
Contraction dose dependently induced in gastric smooth muscle of diabetic rats by Bay K 8644 in the presence of 20 mM KCl was about two times that induced in controls, and was inhibited more than 50% by 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7). Contraction was caused in diabetics but usually not in controls by 10(-5) M phorbol 12-myristate 13-acetate (PMA). In diabetics, this contraction was about 2.5 times that in controls. Protein kinase C (PKC) activity in the soluble fraction was depressed by H-7 or staurosporine, and depended on PMA concentration, but was greater in diabetics than in controls at any PMA concentration. PKC activity in the soluble fraction was inhibited by lower Ca2+ concentration, and was greater in diabetics than in controls. Affinity and density of binding sites of a Ca2+ channel antagonist ligand, [3H]PN200-110, were the same in plasma membrane-enriched fractions isolated from either controls or diabetic preparations. Thus, hyperreactivity in diabetic fundus may depend, in part, on alteration of PKC properties, but not on the density of Ca2+ channels.
Effect of chest wall vibration on dyspnea in patients with chronic respiratory disease.
The effect of chest wall vibration on dyspnea at rest was investigated in 15 patients with severe chronic respiratory diseases. The magnitude of their baseline dyspnea was 17.9 +/- SE 3.3 mm on a 150-mm visual analog scale. One hundred hertz out-of-phase vibration (OPV; inspiratory intercostal muscles vibrated during expiration and expiratory intercostal muscles vibrated during inspiration) increased dyspnea an average of 21.9 +/- SE 7.8 mm (p < 0.05). One hundred hertz in-phase vibration (IPV; inspiratory intercostal muscles vibrated during inspiration and expiratory intercostal muscles vibrated during expiration) decreased dyspnea an average of 6.9 +/- SE 2.8 mm (p < 0.05). Changes in the respiratory pattern and arterial blood gas determinations elicited by 5-min IPV were investigated in eight of the 15 patients. Tidal volume was significantly increased in all eight of these patients. Respiratory frequency was decreased in seven patients and increased in one. Functional residual capacity, measured before and during the application of IPV for a period of about 10 breaths, was increased in one patient and decreased in the remaining seven. PaCO2 decreased by 1.3 +/- 1.0 mm Hg (p < 0.05), from 49.6 +/- 8.4 mm Hg; PaO2 increased by 3.4 +/- 2.3 mm Hg (p < 0.05), from 67.7 +/- 12.7 mm Hg. The results indicate that in-phase chest wall vibration decreased pathologic dyspnea in patients with chronic respiratory disease and suggest that the effects on respiratory sensation are mediated by afferent information from chest wall respiratory muscles to supraspinal centers.
[Clinical usefulness of visual analog scale for assessment of dyspnea at rest in patients with chronic respiratory diseases].
To evaluate the validity and clinical usefulness of the visual analog scale (VAS) for the measurement of dyspnea at rest, we employed the 150 mm VAS in 29 chronic respiratory disease patients who were clinically stable, and repeated the measurement 4 weeks and 8 weeks later for the evaluation of reproducibility. For the 8-week period, the individual medical treatments remained generally unchanged in all patients. Two patients were excluded from the study due to infection and pneumothorax. Dyspnea at rest was detected on VAS in 23 patients at the first measurement. The VAS measurement was 23.9 +/- 28.4 (mean +/- SD) mm at the first time, 22.0 +/- 23.1 mm at the 4th week, and 22.4 +/- 26.0 mm at the 8th week. There was no significant change among the three measurements. Twenty among the 23 patients with VAS indicative of dyspnea at rest were categorized into grades 4 and 5 of the Fletcher dyspnea category. However, the intensity of dyspnea was distributed widely within each Fletcher category. These results lead to the conclusion that VAS shows good reproducibility over a period of as long as 8 weeks and that VAS measurements can reveal patient-to-patient individual differences in dyspnea intensity which cannot be detected by the Fletcher dyspnea category. We propose that measuring dyspnea at rest using VAS is a useful method to obtain a valid clinical parameter.
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.
Relations of contractile hyperreactivity to tachykinins in rabbit trachea.
Explore the source record for details and available documents.
Effects of cAMP on respiratory rhythm generation in brainstem-spinal cord preparation from newborn rat.
Involvement of cAMP in the generation of respiratory rhythm was studied in newborn rat brainstem-spinal cord preparations. The respiratory rhythm was monitored by C4 inspiratory activity and/or pre-inspiratory (Pre-I) activity of neurons in the rostral ventrolateral medulla; previously suggested to be primary rhythm generating neurons which have pacemaker properties. The effects of four cAMP-increasing agents (forskolin, IBMX, Db-cAMP, and 8-Br-cAMP) on this neuronal activity were examined. Perfusion with forskolin (3-10 microM) increased the burst rate of C4 inspiratory activity in 20 of 32 preparations, but in 8 of those the increase was preceded by transient depression. The facilitation of the respiratory rhythm was greater whenever the burst rate before forskolin treatment was lower. The Pre-I neuron burst rate, which was recorded together with C4 activity, predominantly increased with forskolin treatment. The effects of IBMX, Db-cAMP and 8-Br-cAMP were similar to those of forskolin, but they were slightly less potent. Long-lasting depression of the respiratory rhythm (C4 and Pre-I activity) by clonidine, which might decrease intracellular cAMP level via alpha 2-receptors, was reversed by forskolin. To investigate the direct effects of the cAMP-increasing agents on Pre-I neurons, Pre-I activity was isolated by blocking the chemical synaptic transmission by incubation in a low Ca solution (0.2 mM Ca2+, 5 mM Mg2+). Forskolin (5-10 microM), IBMX (5-10 microM), Db-cAMP (0.2-0.4 mM), and 8-Br-cAMP (0.4-0.75 mM) all enhanced the burst rate of isolated Pre-I neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
Possible mutual excitatory couplings between inspiratory neurons in caudal ventrolateral medulla of brainstem-spinal cord preparation isolated from newborn rat.
In in vitro brainstem-spinal cord preparations, projection of inspiratory neurons in the caudal ventrolateral medulla (CVL) was examined electrophysiologically, and connectivity between bilateral inspiratory neurons in the CVL was analyzed by pulse-cross correlation (PCC) analysis. CVL inspiratory neurons were found to project to the contralateral CVL and/or mainly ipsilateral spinal cord. PCC analysis revealed significant peaks with different latency on both sides of time zero in 3 of 8 pairs. Results were consistent with mono- or oligo-synaptic excitatory connections between bilateral inspiratory neurons in the CVL.
Correlation analysis of respiratory neuron activity in ventrolateral medulla of brainstem-spinal cord preparation isolated from newborn rat.
Cross-correlation analysis was used to study functional connections between one inspiratory (I) neuron and another, and between one pre-inspiratory (Pre-I) neuron and another, in 54 brainstem-spinal cord preparations isolated from newborn rats. Pre-I neurons usually fired in the pre- and post-inspiratory phases. Neurons were recorded extracellularly with pairs of microelectrodes placed on the same or opposite sides of the brainstem. Fourteen pairs of Pre-I neurons recorded bilaterally in the rostral ventrolateral medulla (RVL), 14 pairs of ipsilateral Pre-I neurons in the RVL, 14 pairs of bilateral I neurons in the RVL and 12 pairs of ipsilateral I neurons in the ventrolateral medulla were studied. Cross-correlation histograms (CCHs) were computed. Significantly high peak bin counts were detected in 24 of 54 pairs. Peaks on one side of the origin of the CCHs were observed for one pair of ipsilateral Pre-I neurons, four pairs of bilateral I neurons and five pairs of ipsilateral I neurons. These findings suggest mono- or oligo-synaptic excitatory connections between paired neurons or shared inputs. Only one trough suggesting an oligo-synaptic inhibitory connection was evident in a CCH obtained from the pair of bilateral I neurons. This CCH revealed the peak and the trough on opposite sides of the origin, which was consistent with reciprocal excitatory and inhibitory connections between recorded neurons. Peaks on both sides of the origin were observed for three pairs of bilateral I neurons. From auto-correlation analysis and the latencies of these peaks, two of the three CCHs were consistent with reciprocal excitatory connections between recorded neurons, whereas the other CCH suggests shared inputs. Peaks at the origin were observed for two pairs of ipsilateral Pre-I neurons, four pairs of bilateral I neurons and five pairs of ipsilateral I neurons. These results suggest shared inputs. For Pre-I neurons recorded in opposite sides, no significant bin counts were detected. Peaks on one side were detected for three pairs. Present results suggest short-term synchronisation of I neurons, and of Pre-I neurons via excitatory coupling, and the likelihood of comparatively strong interaction between I neurons, which may be important in maintaining the I burst.
Histamine immunoreactive neurons in the brain stem of the rabbit.
Distribution of histamine-like immunoreactive (HA-LI) neurons in the rabbit brain stem was demonstrated by histamine antiserum. A number of HA-LI cell bodies were localized in the tuberomammillary nucleus of the posterior hypothalamus. A dense to moderate amount of HA-LI fibers was found distributed in the raphe nuclei, the inferior olive, the nucleus of the solitary tract, vestibular nuclei, and the paragigantocellular reticular nucleus in the medulla oblongata, and the parabrachial nuclei, the Klliker-Fuse nucleus, the pontine nuclei, and the locus coeruleus in the pons. HA-LI axons synapsed on dendrites of neurons in the nucleus of the solitary tract. This evidence suggests that histaminergic neurons control neuronal activity through synaptic transmission in the lower brain stem.
Effects of NMDA on respiratory neurons in newborn rat medulla in vitro.
In 30 brain stem-spinal cord preparations isolated from newborn rats, we examined effects of 10 microM N-methyl-D-aspartate (NMDA) on 21 pre-inspiratory (Pre-I) and 26 inspiratory (I) neurons during perfusion in a synaptic blockade (low Ca2+, high Mg2+) bath, referred to here as low Ca. Application of NMDA to 9 Pre-I neurons that burst rhythmically by NMDA. Application of NMDA had no effect on 20 I neurons out of 26 tested. NMDA made one I neuron that was otherwise silent burst rhythmically in low Ca. The results suggest that, in this preparation, activation of NMDA receptors could contribute to induction or facilitation of burst activity by respiratory neurons, especially Pre-I neurons.
Effect of acupuncture at the right Hoku point on bilateral vibration-induced finger flexion reflex in man: comparison between in-situ and Sparrow Pecking technique.
The purpose of this study was to compare the effect of the Sparrow Pecking (SP) technique with that of the In-Situ (IS) technique of acupuncture on vibration-induced finger flexion reflex (VFR). Subjects were 30 healthy adults. VFR, flexion movement of the vibrated finger, was induced by vibrating the volar side of the middle finger tip. The acupuncture point was the right Hoku point. Both techniques of acupuncture inhibited VFR in the ipsilateral and contralateral sides, but inhibition with SP was significantly greater than that with IS (percentage control force of VFR, mean +/- SD: with SP right, 62.1 +/- 24.6%, left, 60.6 +/- 27.9%, with IS right, 74.9 +/- 26.6%, left, 78.1 +/- 29.5%, P < 0.0005). The results suggest that SP suppresses facilitation of VFR in the reflex arcs more than IS does.
Inspiratory prolongation by vagal afferents from pulmonary mechanoreceptors in rabbits.
Graded inflation and deflation pressures were transiently applied to the airway, and the effects on the inspiratory (TI) and expiratory (TE) durations were studied in twelve Japanese white rabbits tracheotomized and anesthetized with urethane and chloralose. Without vagal cooling, lung inflation prolonged TE, whereas changes in TI were small and inconsistent. The bilateral vagus nerves were cooled to 7 degrees C to block myelinated fibers, and to study the effects of C-fiber afferents. During vagal cooling to 7 degrees C, inflation dose dependently prolonged the first TI with no consistent change in TE. Without vagal cooling, lung deflation shortened TE of the first and succeeding breaths, and prolonged TI of the first breath to manifest apneusis. Deflation applied at the vagal temperature of 7 degrees C induced slight shortening of TI and TE in 6 of the 12 rabbits. All these changes were blocked when the vagus nerves were cooled to 1 degree C. The results may indicate that vagal afferents from irritant receptors shorten TE, and C-fiber afferents prolong TI. High irritant afferent activity may markedly shorten TE, causing tidal inspiratory activities to merge and manifest apneusis. Capsaicin, which is suggested to be a "selective" stimulant of C-fiber receptors was injected into the right atrium in 4 of the 12 rabbits. The chief changes were TE shortening without vagal cooling, and TI prolongation during cooling to 7 degrees C. This suggests that capsaicin injected into the pulmonary circulation stimulates both the irritant and C-fiber receptors and the C-fiber afferents may prolong TI even when stimulated chemically.
Effect of substance P on respiratory rhythm and pre-inspiratory neurons in the ventrolateral structure of rostral medulla oblongata: an in vitro study.
The pre-inspiratory (Pre-I) neurons which fire in the pre- and usually also during the post-inspiratory phase are located in the ventrolateral structures of the rostral medulla. They are suggested as primary rhythm generating neurons for respiration. These have been studied in isolated brainstem-spinal cord preparations from newborn 0-5-day-old rats. We have found that application of substance P (SP) enhanced the respiratory rhythm as measured by C4 ventral root and pre-I neuronal activities. Furthermore, the effect of SP was dependent on basal respiratory rate. An increase of the Pre-I and C4 burst rate by SP was clearer when the basal respiratory rhythm was somewhat lower. Moreover, long lasting depression of respiratory rate after the application of the alpha 2-agonist clonidine was reversed by SP. On the other hand, an inhibitory effect appeared in preparations with a higher basal respiratory rate, while the Pre-I burst rate tended to increase during SP perfusion. During chemical synaptic transmission blockade by perfusion with low Ca2+, high Mg2+ solution, a pre-I burst retained or completely blocked was found to be enhanced or reactivated by SP perfusion. The results suggest a direct postsynaptic action of SP, which could strongly stimulate burst generating properties of Pre-I neurons.
Recent studies of surface dynamic processes by reflection electron microscopy.
Reflection electron microscope studies of surface dynamic processes are reviewed and illustrated with recent new observations. They include: surface electromigration and current dependent structures of Si surfaces; surface etching by oxidation of Si surface; and growth of two dimensional alloyed adsorbate by co-deposition of metals on Si surface. The observations revealed details of the surface dynamic processes, which are difficult to obtain with other surface analysis techniques.
Whole cell recordings from respiratory neurons in the medulla of brainstem-spinal cord preparations isolated from newborn rats.
In brainstem-spinal cord preparations isolated from newborn rats, a whole cell recording technique was applied to record membrane potentials of inspiratory (Insp) and pre-inspiratory (Pre-I) neurons in the ventrolateral medulla. Labelling of these respiratory neurons with Lucifer Yellow allowed analysis of their locations and morphology. Intracellular membrane potentials from 25 Insp neurons were recorded. Average resting membrane potential was -49 mV (n = 25) and input resistance was 306 M omega. Insp neurons were classified into three types from the patterns of synaptic potentials. Type I neurons (n = 11) had a high probability of excitatory postsynaptic potentials (EPSPs) in the pre- and post-inspiratory phases. Type II neurons (n = 7) showed abrupt transition to the burst phase from the resting potential level without increased EPSPs in the preinspiratory phase. Type III neurons (n = 7) were hyperpolarized by inhibitory postsynaptic potentials (IPSPs) in the pre- and post-inspiratory phases. These Insp neurons, located in the ventrolateral medulla 80-490 microns from the ventral surface, were 10-30 microns in diameter, and had various soma shapes (pyramidal, spherical or fusiform). Intracellular membrane potentials from 24 Pre-I neurons were recorded. The average resting membrane potential was -45 mV (n = 24), and the input resistance was 320 M omega. Typical Pre-I neurons showed fairly great depolarization accompanied by action potentials during their burst phase and repolarization during the inspiratory phase. Most Pre-I neurons appeared to have a high level of synaptic activity.(ABSTRACT TRUNCATED AT 250 WORDS)