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Biomedical subjects

Y Uchino

Publications and source records attributed to Y Uchino.

At least 55 records · Page 3Linked to original sources
PubMed1998

Morphology of single afferents of the saccular macula in cats.

The morphology of single saccular afferents was studied by the intracellular horseradish peroxidase (HRP) method. Four neurons were sufficiently stained to allow reconstruction of their axonal arborizations. The main axon of these neurons bifurcated into an ascending and a descending branch at the level of the lateral nucleus. The ascending branches of two axons gave off collaterals with boutons in the caudal part of the superior nucleus, while the other two ascending branches lacked such terminations. By contrast, characteristics of the descending axonal arborization patterns of all the four neurons were substantially the same. The descending branches coursed caudally through the lateral part of the descending nucleus, and gave off up to 14 collaterals with boutons that extended throughout this nucleus. These collaterals also reached the ventral part of the lateral nucleus, the lateral border of the medial nucleus, and group f. A few axon collaterals ramified even outside the border of the vestibular nuclei into the spinal trigeminal nucleus and the reticular formation surrounding it. Axon collaterals from the stem axon also terminated in the interstitial nucleus of the vestibular nerve. There was a noticeable absence of any projection to the y group.

Action Potentials↗
PubMed1998

Addition and deletion of objects on memory for composition of scenes.

The present study examined the effect of addition and deletion of stimuli to the current environment on perceivers' performance of memory task. Further, the robustness of the asymmetric effects of addition and deletion was investigated. 48 objects in a room were grouped into four schematically consistent or inconsistent conditions. In the experiment, participants viewed a series of an original scene and a target scene with the placement of an object changed from the original scene before the recall and the recognition tasks. Participants were asked whether they noticed change from the original scene to the target scene. The recall tasks were performed both verbal and written. In the recognition task, each of the 24 objects (17 objects were actually present in the scene, but seven were not) was visually presented on the computer display along with confidence ratings. Analysis showed that participants were more likely to recall placement of objects classified as highly expected and highly salient according to an hypothesized schema of placement. There was also a significant effect of addition on recall performance when objects were classified as low in expectation but highly salient were added to the target scene. The effects of addition on schema-inconsistent information were discussed in terms of informativeness of the information.

Adult↗
PubMed1997

Excitatory connections between neurons of the central cervical nucleus and vestibular neurons in the cat.

The central cervical nucleus (CCN) of the cat receives input from upper cervical muscle afferents, particularly primary spindle afferents. Its axons cross in the spinal cord, and while in the contralateral restiform body give off collaterals to the vestibular nuclei. In order to study the connections between CCN axons and vestibular neurons, we stimulated the area of the CCN in decerebrate cats while recording intra- or extracellularly from neurons in the contralateral vestibular nuclei. CCN stimulation evoked excitatory postsynaptic potentials (EPSPs) or extracellularly recorded firing in the lateral, medial and descending vestibular nuclei. The latency of EPSPs (mean 1.6 ms) was on average 0.4 ms longer than the latency of antidromic spikes evoked in the CCN by stimulation of the contralateral vestibular nuclei (mean 1.2 ms), demonstrating that the excitation was typically monosynaptic. The results provide further evidence that the CCN is an important excitatory relay between upper cervical muscle afferents and neurons in the contralateral vestibular nuclei.

Animals↗
PubMed1997

Properties of saccular nerve-activated vestibulospinal neurons in cats.

Axonal pathways, projection levels, conduction velocities, and locations of the cell bodies of saccular nerve-activated vestibulospinal neurons were studied in decerebrated cats and anesthetized cats, using a collision test of orthodromic and antidromic spikes. The saccular nerve was selectively stimulated by bipolar tungsten electrodes. Three monopolar electrodes were inserted into the left and right lateral vestibulospinal tract (LVST) and medial vestibulospinal tract (MVST) of the C1 segment, to determine the pathway of axons. Three pairs of similar electrodes were positioned bilaterally in the C3-4, T1, and L3 segments to examine projection levels. Another monopolar electrode was placed in the oculomotor nucleus to determine whether saccular nerve-activated vestibulospinal neurons have branches ascending to the oculomotor nucleus. Of 145 vestibular neurons orthodromically activated by stimulation of the saccular nerve, 46 were activated from the C1 segment antidromically. Forty-three were second-order vestibulospinal neurons and 3 were third-order vestibulospinal neurons. Four saccular nerve-activated vestibulospinal neurons were also antidromically activated from the oculomotor nucleus. Sixty-three percent of the saccular nerve-activated vestibulospinal neurons descended through the MVST; one-third of these terminated in the upper cervical segments, one-third reached the lower cervical segments and the remaining one-third reached the upper thoracic segments. Thirty percent of the saccular nerve-activated vestibulospinal neurons descended through the ipsilateral LVST; most of these reached the upper thoracic segments. Seven percent of the saccular nerve-activated vestibulospinal neurons descended through the contralateral vestibulospinal tracts terminating in the upper cervical segments. Most of the saccular nerve-activated vestibulospinal neurons originated in the caudal part of the lateral nucleus and rostral part of the descending nucleus.

Animals↗
PubMed1997

Synchronous and metachronous carcinomas of the esophagus and head and neck.

We retrospectively analyzed the clinicopathologic findings, treatment and outcome of 22 patients with synchronous or metachronous carcinomas of the esophagus and head and neck. The patients with metachronous cancers in whom esophageal cancer occurred first had either an early-stage esophageal carcinoma or only one positive lymph node. Similarly, five of 10 patients with metachronous cancers in whom head and neck cancer was the first tumor had early-stage esophageal carcinomas. The esophageal lesion was mucosal carcinoma in four patients which was found by endoscopy with the iodine dye method. In the patients with synchronous cancers either one or both carcinomas were advanced, and the prognosis of these patients was poor compared with those of patients with metachronous carcinomas. Accordingly, endoscopic surveillance for early detection of metachronous lesions are encouraged.

Adult↗
PubMed1997

Sacculocollic reflex arcs in cats.

Neuronal connections and pathways underlying sacculocollic reflexes were studied by intracellular recordings from neck extensor and flexor motoneurons in decerebrate cat. Bipolar electrodes were placed within the left saccular nerve, whereas other branches of the vestibular nerve were removed in the inner ear. To prevent spread of stimulus current to other branches of the vestibular nerve, the saccular nerve and the electrodes were covered with warm semisolid paraffin-Vaseline mixture. Saccular nerve stimulation evoked disynaptic (1.8-3.0 ms) excitatory postsynaptic potentials (EPSPs) in ipsilateral neck extensor motoneurons and di- or trisynaptic (1.8-4.0 ms) EPSPs in contralateral neck extensor motoneurons, and di- and trisynaptic (1.7-3.6 ms) inhibitory postsynaptic potentials (IPSPs) in ipsilateral neck flexor motoneurons and trisynaptic (2.7-4.0 ms) IPSPs in contralateral neck flexor motoneurons. Ipsilateral inputs were about twice as strong as contralateral ones to both extensor and flexor motoneurons. To determine the pathways mediating this connectivity, the lateral part of the spinal cord containing the ipsilateral lateral vestibulospinal tract (i-LVST) or the central part of the spinal cord containing the medial vestibulospinal tracts (MVSTs) and possibly reticulospinal fibers (RSTs) were transected at the caudal end of the C1 segment. Subsequent renewed intracellular recordings following sacculus nerve stimulation indicated that the pathway from the saccular nerve to the ipsilateral neck extensor motoneurons projects though the i-LVST, whereas the pathways to the contralateral neck extensors and to the bilateral neck flexor motoneurons descend in the MVSTs/RSTs. Our data show that sacculo-neck reflex connections display a qualitatively bilaterally symmetrical innervation pattern with excitatory connections to both neck extensor motoneuron pools, and inhibitory connections to both neck flexor motoneuron pools. This bilateral organization contrasts with the unilateral innervation scheme of the utriculus system. These results suggest a different symmetry plane along which sacculus postural reflexes are organized, thus supplementing the reference planes of the utriculus system and allowing the gravistatic system to represent all three translational spatial degrees of freedom. We furthermore suggest that the sacculocollic reflex plays an important role in maintaining the relative position of the head and the body against the vertical linear acceleration of gravity.

Afferent Pathways↗
PubMed1997

Excitatory and inhibitory inputs from saccular afferents to single vestibular neurons in the cat.

Connections from saccular afferents to vestibular neurons were studied by means of intracellular recordings of excitatory (E) and inhibitory (I) postsynaptic potentials (PSPs) in vestibular neurons after focal stimulation of the saccular macula in decerebrated cats. Focal stimulation was given to the saccular macula in two ways, in which the polarity of stimulus current via a pair of electrodes was changed. In group A, one of the electrodes was inserted into the ventral and the other into the dorsal edge of the saccular macula. The focal stimulation was across the striola so that the reversal of morphological polarization in hair cells was bridged by the pulse stimulus. In 22/36 vestibular neurons tested, the stimulation of the saccular macula evoked monosynaptic (</=1.2 ms) EPSPs, including EPSP-IPSP sequences, with one polarity of stimulation, and disynaptic (>/=1.5 ms) IPSPs when the polarity of the stimulus current was changed. In 14/36 neurons, the response pattern was the same regardless of the stimulus polarity; EPSPs (12/36) or IPSPs (2/36). In group B, a pair of electrodes was inserted into the dorsal edge of the saccular macula, so that the striola was not bridged by the current stimulus. In all of the vestibular neurons tested, the response pattern was always the same regardless of the polarity: mono- (22/31) and disynaptic (3/31) EPSPs or disynaptic IPSPs (6/31). In addition, the saccular nerve was stimulated after removing the macula in some cats (group C). The stimulation of the saccular nerve evoked EPSPs in 62 vestibular neurons (including EPSP-IPSP sequences in 31 neurons) and IPSPs in 19 vestibular neurons. Convergence between the saccular nerve and other vestibular nerves was studied by the intracellular recording of PSPs. Fifty-six percent (18/32) of the saccular-activated neurons had excitatory and/or inhibitory potentials evoked after stimulation of the utricular nerve and the horizontal and anterior semicircular canal nerves, and 44% (19/43) of the neurons received inputs from the posterior semicircular canal nerve. The results support the hypothesis that saccular afferents from one population of hair cells activate vestibular neurons monosynaptically and that afferents from another population of hair cells located on the opposite side of the striola appear to project to the same vestibular neurons disynaptically via inhibitory interneurons. Neural circuits from saccular afferents to vestibular neurons, which we term cross-striolar inhibition, thus may provide a mechanism for increasing the sensitivity to vertical linear acceleration. The circuit described is provided not only with high sensitivity but also with input noise-resistant characteristics.

Afferent Pathways↗
PubMed1997

Utricular input to cat extraocular motoneurons.

Intracellular recordings from 200 identified extraocular motoneurons in the bilateral III, IV and VI cranial nuclei were studied to determine the connectivities between the utricular nerve and the extraocular motoneurons in cats. Stimulating electrodes were placed within the left utricular nerve, while other branches of the vestibular nerve were removed. Monosynaptic and disynaptic connections between the utricular nerve and the ipsilateral abducens motoneurons and interneurons were recorded as described previously. Stimulation of the utricular nerve evoked longer latency depolarizing and hyperpolarizing potentials in contra- and ipsilateral medial rectus motoneurons, respectively. Depolarizing and hyperpolarizing potentials with longer latencies were also recorded in the ipsilateral inferior oblique and contralateral trochlear motoneurons. The short and longer latency circuits between the utricular nerve and extraocular motoneurons may play a role in stabilizing the retinal image during head tilt and horizontal linear acceleration.

Abducens Nerve↗
PubMed1997

Connections between otolith receptors and neck motoneurons.

Intracellular recordings from ipsilateral and contralateral neck extensor and flexor motoneurons were studied to determine the connections between the utricular nerve and neck motoneurons and between saccular nerves and neck motoneurons in cats. Stimulating electrodes were placed within the left utricular nerve or saccular nerve. Electrical stimulation of the utricular nerve evoked excitatory postsynaptic potentials (EPSPs) with disynaptic latency in almost all ipsilateral extensor motoneurons and disynaptic EPSPs in all ipsilateral flexor motoneurons. In contralateral extensor and flexor motoneurons, the initial response to utricular stimulation was usually inhibitory postsynaptic potentials (IPSPs) with trisynaptic linkage. Thus, the utriculo-neck connectivities essentially differentiated between the left and right side. In response to stimulation of the saccular nerve, the initial response in bilateral extensor motoneurons ws EPSPs. Ipsilateral projections were always disynaptic; contralateral projections could be di- or trisynaptic. IPSPs were evoked in almost all bilateral flexor motoneurons with di- or trisynaptic latencies. The sacculo-neck motoneuron relationship thus has a qualitatively, bilaterally symmetric organization with regard to flexors and extensors.

Animals↗
PubMed1996

Properties of utricular nerve-activated vestibulospinal neurons in cats.

The axonal pathway, conduction velocities, and locations of the cell bodies of utricular nerve-activated vestibulospinal neurons were studied in decerebrated or anesthetized cats using the collision test of orthodromic and antidromic spikes. For orthodromic stimulation, bipolar tungsten electrodes were placed on the utricular nerve and the other vestibular nerve branches were transected. Monopolar tungsten electrodes were positioned on both sides of the upper cervical segments (C2-4), caudal end of the cervical enlargement (C7-T1), and from the lower thoracic to the upper lumbar segments (T12-L3) and were used for antidromic stimulation of the spinal cord. Another monopolar electrode was also placed in the oculomotor nucleus to study whether utricular nerve-activated vestibulospinal neurons have ascending branches to the oculomotor nucleus. Of the 173 vestibular neurons orthodromically activated by the stimulation of the utricular nerve, 46 were second-order vestibulospinal neurons and 5 were third-order neurons. The majority of the utricular nerve-activated vestibulospinal neurons were located in the rostral part of the descending vestibular nucleus and the caudal part of the ventral lateral nucleus. Seventy-three percent of the utricular nerve-activated vestibulospinal neurons descended through the ipsilateral lateral vestibulospinal tract. Approximately 80% of these neurons reached the cervico-thoracic junction, but a few reached the upper lumbar spinal cord. Twenty-seven percent of the utricular nerve-activated vestibulospinal neurons descended through the medial vestibulospinal tract or the contralateral vestibulospinal tracts. Those axons terminated mainly in the upper cervical segments. Almost none of the utricular nerve-activated vestibular neurons had ascending branches to the oculomotor nucleus.

Afferent Pathways↗
PubMed1996

Utriculoocular reflex arc of the cat.

1. Intracellular recordings of synaptic potentials in extraocular motoneurons were studied to determine the connectivities between the utricular nerve and the extraocular motoneurons in cats. 2. Stimulating electrodes were placed within the left utricular nerve, while other branches of the vestibular nerve were removed. Subsequently, the N1 field potentials evoked by utricular nerve stimulation were recorded in the vestibular nuclei. The potential typically grew until reaching a plateau (submaximal stimulation). Stimulus spread to the other nerve branches appeared as an additional increase in N1 amplitude after the plateau discontinued (supramaximal stimulation). 3. Intracellular recordings were made from 200 identified motoneurons in the bilateral III, IV, and VI cranial nuclei. 4. Stimulation of the utricular nerve at submaximal intensity evoked a longer latency depolarizing and hyperpolarizing potentials in contra- and ipsilateral medial rectus motoneurons, respectively. Complex potentials with longer latencies also were recorded in ipsilateral inferior oblique and contralateral trochlear motoneurons after stimulation of the utricular nerve at a submaximal intensity. Monosynaptic and disynaptic connections between the utricular nerve and ipsilateral abducens motoneurons and interneurons were recorded as described previously. 5. The results of the present study confirm our initial findings that a disynaptic pathway from the utricular nerve to contralateral trochlear motoneurons is absent or very poorly developed, whereas polysynaptic circuits from the utricular nerve to inferior oblique and trochlear motoneurons may play a role in eye rotation during head tilt.

Animals↗
PubMed1995

Axonal projections of utricular afferents to the vestibular nuclei and the abducens nucleus in cats.

Axonal projections of utricular (UT) afferents in cats were examined by three approaches: recordings of field potentials, labelling of UT nerve fibres by localized infusion of horseradish peroxidase (HRP) and intraaxonal infusion of HRP into a single UT afferent. UT afferents project principally into the rostral part of the descending nucleus and the ventral part of the lateral nucleus. Projection into the superior and the medial nuclei and the ipsilateral abducens nucleus were also observed.

Abducens Nerve↗
PubMed1994

Axon branching of medullary expiratory neurons in the lumbar and the sacral spinal cord of the cat.

Intraspinal axon collaterals of expiratory (E) neurons in the caudal nucleus retroambigualis extending their desending spinal axons to the lower lumbar (L6-L7) and the sacral (S1-S3) segments were investigated in anesthetized cats. To search for axon collaterals of single E neurons in the lumbar segments, the spinal gray matter was microstimulated from the dorsal to the ventral sites at 100 microns intervals with an intensity of 150-250 microA at 1 mm intervals rostrocaudally along the spinal cord, and effective stimulating sites of antidromic activation in axon collaterals were systematically mapped. In addition, the detailed trajectory of collaterals in the upper lumbar (L1-L3), the middle lumbar (L4-L5), and the sacral (S1-S3) spinal cord was examined by microstimulation at a matrix of points 100-200 microns apart with a maximum stimulus intensity of 50 microA. The trajectory of axon collaterals was reconstructed on the basis of the location of low-threshold foci and the latency of antidromic spikes. Virtually all E neurons examined had 1-7 collaterals at widely separated segments of the lumbar cord. Many axon collaterals were found in the upper lumbar spinal cord as compared to the middle and the lower lumbar spinal cord. The locations of axon collaterals in the upper lumbar spinal cord overlapped with those of abdominal motoneurons. Axon collaterals in the sacral gray matter were found in 3 of 9 E neurons. Axon collaterals were found within the nucleus of Onuf, in the region dorsal to the nucleus of Onuf, and in the intermediate region. The functional significance of the divergent distribution of multiple axon collaterals of single E neurons in different spinal levels of the lumbar and the sacral spinal cord is discussed in relation to the respiratory function of E neurons and other spinal motor activities.

Animals↗
PubMed1994

Connections between utricular nerve and neck flexor motoneurons of decerebrate cats.

We studied the circuitry between the utricular (UT) nerve and ventral neck motoneurons innervating the longus capitis (LC), a neck flexor muscle, in decerebrate cats. We recorded intracellularly from 63 LC (ipsilateral 37, contralateral 26) motoneurons in C1 and C2 segments. UT nerve stimulation evoked disynaptic, excitatory postsynaptic potentials in all ipsilateral LC motoneurons, and inhibitory postsynaptic potentials that were at least trisynaptic in almost all contralateral LC motoneurons. UT effects on neck motoneurons innervating muscles involved in flexion and lateral turning are similar to the connections between the UT nerve and neck extensor motoneurons. These neuron circuits may play a role in fixing the head and the neck to the body during horizontal linear acceleration.

Action Potentials↗
PubMed1994

Second-order vestibular neuron morphology of the extra-MLF anterior canal pathway in the cat.

Second-order vestibular neurons form the central links of the vestibulo-oculomotor three-neuron arcs that mediate compensatory eye movements. Most of the axons that provide for vertical vestibulo-ocular reflexes ascend in the medial longitudinal fasciculus (MLF) toward target neurons in the oculomotor and trochlear nuclei. We have now determined the morphology of individual excitatory second-order neurons of the anterior semicircular canal system that course outside the MLF to the oculomotor nucleus. The data were obtained by the intracellular horseradish peroxidase method. Cell somata of the extra-MLF anterior canal neurons were located in the superior vestibular nucleus. The main axon ascended through the deep reticular formation beneath the brachium conjunctivum to the rostral extent of the nucleus reticularis tegmenti pontis, where it crossed the midline. The main axon continued its trajectory to the caudal edge of the red nucleus from where it coursed back toward the oculomotor nucleus. Within the oculomotor nucleus, collaterals reached superior rectus and inferior oblique motoneurons. Some axon branches recrossed the midline within the oculomotor nucleus and reached the superior rectus motoneuron subdivision on that side. Since these neurons did not give off a collateral toward the spinal cord, they were classified as being of the vestibulo-oculomotor type and are thought to be involved exclusively in eye movement control. The signal content and spatial tuning characteristics of this anterior canal vestibulo-oculomotor neuron class remain to be determined.

Animals↗
PubMed1994

Monosynaptic and disynaptic connections in the utriculo-ocular reflex arc of the cat.

1. Connections from the utricular (UT) nerve to motoneurons and interneurons in the ipsilateral abducens (AB) nucleus were studied in anesthetized and decerebrated cats. Bipolar electrodes were fixed on the left UT nerve under visual observation. The other branches of the vestibular nerve and the facial nerve were transected in the left inner ear. 2. Stimulation of the UT nerve evoked a small positive-negative (P/N) deflection and a negative (N1) potential in the vestibular nuclei, with mean latencies of 0.56 and 0.84 ms, respectively. In the AB nucleus a small P/N deflection with a mean latency of 0.72 ms was recorded, which was considered as a incoming volley of the UT nerve. 3. Excitatory postsynaptic potentials (EPSPs) were recorded from AB motoneurons with short latencies after UT nerve stimulation. They were classified into two types, M and D. M-type EPSPs, which followed repetitive high-frequency stimuli and were recorded from the majority of AB motoneurons, had latencies ranging from 0.9 to 1.2 ms. Double shocks to the UT nerve evoked EPSPs that had the same latency. It was suggested that the AB motoneurons had monosynaptic connections with the UT nerve. D-type EPSPs, which were recorded from most of the AB motoneurons, had slightly longer latencies ranging from 1.2 to 1.8 ms. They showed temporal facilitation when double shocks were provided to the UT nerve. They did not follow repetitive high-frequency stimuli (< or = 2.5-ms interval). It was suggested that D-type EPSPs were di-synaptically evoked via secondary vestibular neurons. Interneurons in the AB nucleus had the same characteristics as AB motoneurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Abducens Nerve↗
PubMed1994

A case of a primary hepatic tumor causing segmental changes on imaging and its relation to Zahn's infarct.

A 69-year-old female was admitted to our hospital for further examination of an intrahepatic mass which had been found while undergoing a complete physical examination. The mass measured 4 cm in size and was located in the medial segment (S4) of the liver. On computed tomography (CT), S4 was observed to be 'atrophied' and was well enhanced segmentally. A celiac angiogram showed segmental staining, and a transarterial portogram demonstrated portal stoppage of S4 from the left branch. However, no segmental intensity difference was seen on magnetic resonance imaging (MRI). An aspiration biopsy showed adenocarcinoma and thus an operation was performed under a tentative diagnosis of intrahepatic cholangiocarcinoma. The postoperative diagnosis of the tumor was combined hepatocellular and cholangiocellular carcinoma. However, no histological abnormality was seen in S4, contrary to the expectation of Zahn's infarct. In this study, we discuss the mechanism and imaging findings of Zahn's infarct, the possible reasons as to why no pathological change was seen in S4, as well as stress the rarity of reports on Zahn's infarct in cases of portal thrombus due to hepatocellular carcinoma.

Aged↗