Biomedical subjects

A Mitani

Publications and source records attributed to A Mitani.

89 records · Page 5Linked to original sources

PubMed1987

Distribution and size of thalamic neurons projecting to layer I of the auditory cortical fields of the cat compared to those projecting to layer IV.

The distribution of thalamocortical neurons projecting to layer I of the cat auditory cortical fields was examined by the horseradish peroxidase (HRP) method. After HRP injection into layer I of the primary auditory cortex (AI), HRP-labeled neuronal cell bodies were distributed mainly in the medial, dorsal, and ventrolateral divisions of the medial geniculate nucleus (MGN) and suprageniculate nucleus (Sg), and additionally in the lateral and medial divisions of the posterior group of the thalamus (Pol and Pom), lateroposterior thalamic nucleus (Lp), and nucleus of the brachium of the inferior colliculus (BIN). After HRP injection into layer I of the second auditory cortex (AII), labeled neurons were seen mainly in the medial, dorsal, and ventrolateral divisions of the MGN and Sg and additionally in the Pom, Lp, and BIN. After HRP injection into layer I of the anterior auditory field (AAF), labeled neurons were located mainly in the medial and dorsal divisions of the MGN, Sg, Pol, and BIN, and additionally in the ventrolateral divisions of the MGN, Pom, and Lp. After HRP injection into layer I of the dorsal part of the posterior ectosylvian gyrus (Epd), labeled neurons were observed chiefly in the medial and dorsal divisions of the MGN, Sg, and Lp and additionally in the ventrolateral division of the MGN, Pom, and BIN. After HRP injection into layer I of the ventral part of the posterior ectosylvian gyrus (Epv), labeled neurons were distributed chiefly in the medial and dorsal divisions of the MGN and Pol and additionally in the ventrolateral division of the MGN, Sg, and BIN. Thus no labeled neurons were found in the ventral division of the MGN after HRP injection into layer I of all auditory cortical fields examined in the present study. The average soma diameters of neurons that were labeled after HRP injection into layer I were statistically smaller than those of neurons that were labeled after HRP injection into layer IV.

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PubMed1987

Direct projections from the dorsal column nuclei and the spinal trigeminal nuclei to the cochlear nuclei in the cat.

A retrograde and anterograde wheat germ agglutinated horseradish peroxidase WGA-HRP study in the cat indicated that some neurons in the dorsal column nuclei and the interpolar and caudal spinal trigeminal nuclei send fibers to the dorsal and ventral cochlear nuclei; to the pyramidal cell layer of the dorsal cochlear nucleus and to the cochlear granule cell domain, bilaterally with an ipsilateral dominance.

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PubMed1987

Primary repair of interrupted aortic arch and severe aortic stenosis in neonates.

Two infants, aged 36 days old (Case 1) and 18 days old (Case 2) with interrupted aortic arch types B and A, respectively, and with severe aortic stenosis, were successfully operated on by use of pulsatile cardiopulmonary bypass. The great arteries were normally related in Case 1 and were transposed in Case 2. Repair involved the following procedure: ligation of the patent ductus arteriosus, restoration of aortic continuity with an 8 mm polytetrafluoroethylene graft, placement of an internal patch to tunnel all left ventricular blood from the left ventricle through the ventricular septal defect into the pulmonary artery in Case 1 and patch closure of the ventricular septal defect in Case 2, transection of the main pulmonary artery, anastomosis between the proximal pulmonary artery and the ascending aorta, and interposition of a valved conduit between the right ventricle and the distal pulmonary artery. The operative field could be approached easily through a median sternotomy. Postoperative cardiac catheterization revealed satisfactory anatomical and hemodynamic results in both cases.

Aorta↗

PubMed1986

Dual mode of projections from the parietal to the motor cortex in the cat.

The cortico-cortical projection from area 5 to area 4 gamma was studied in anesthetized cats. Intracortical microstimulation of area 5 produced EPSPs in pyramidal tract (PT) cells in area 4 gamma. Such EPSPs were analysed in a total of 54 fast PT cells. The rising phase of these EPSPs was often composed of fast and slow components. Fast-rising EPSPs (fast component) were produced predominantly by stimulation within layer III of area 5 while slow-rising EPSPs (slow component) were evoked predominantly by stimulation within layer V of area 5. The amplitudes of the fast and slow components of EPSPs produced during repetitive stimulation within layers III and V of area 5 decreased and increased, respectively, with an increase in the stimulus frequency without any appreciable changes in their latency and time-to-peak. The slow component was much less influenced by membrane hyperpolarization than the fast component. Retrogradely labeled neurons were found not only in layer III but also in layer V of area 5 following HRP injection centered on superficial layers (I-III) of area 4 gamma. It is suggested that there are two groups of cortico-cortical neurons in layers III and V of area 5, which may make monosynaptic contact with the proximal and distal sites of fast PT cells in area 4 gamma, respectively.

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PubMed1985

Cerebral cortical projections to the reticular regions around the trigeminal motor nucleus in the cat.

Cerebral cortical regions which send projection fibers to the reticular regions around the trigeminal motor nucleus were identified in the cat by the horseradish peroxidase (HRP) method. The reticular region around the trigeminal motor nucleus are known to contain many interneurons for masticatory motoneurons. After injections of HRP into the reticular regions around the trigeminal motor nucleus, HRP-labeled neuronal cell bodies in the cerebral cortex were found in layer V. They were distributed bilaterally in the orbitofrontal cortical regions, mainly in the rostral extension of the orbital gyrus close to the presylvian sulcus; more were located in the floor and lateral bank of the presylvian sulcus than in the crown of the orbital gyrus. After injections of HRP conjugated with wheat germ agglutinin (WGA-HRP) into these cortical regions, many labeled presumed axon terminals were distributed bilaterally in the reticular regions around the trigeminal motor nucleus; mainly in the region ventral to the trigeminal motor nucleus and in the intertrigeminal region between the main sensory trigeminal nucleus and the trigeminal motor nucleus. Terminal labeling in these regions was more prominent after WGA-HRP injection into the lateral bank of the presylvian sulcus than after WGA-HRP injection into the crown of the orbital gyrus. Thus, the present results indicate that the main part of the cortical region projecting directly to the reticular regions around the trigeminal motor nucleus in the cat is folded into the presylvian sulcus.

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PubMed1985

Neuronal connections in the primary auditory cortex: an electrophysiological study in the cat.

Neuronal connections in the primary auditory cortex (AI) of the cat were studied electrophysiologically by using intracellular recording techniques. Fast-conducting fibers from the medial geniculate nucleus (MG) projected monosynaptically onto AI neurons in layers III-VI (mainly in layer IV), whereas slow-conducting MG-fibers projected monosynaptically onto AI neurons in layer I. AI neurons which received monosynaptic inputs from the auditory association cortices (AII and Ep) and/or from the contralateral AI were distributed in all layers of the AI; the commissural fibers from the contralateral AI were divided into fast- and slow-conducting ones. AI neurons were categorized into seven types: type I neurons which received monosynaptic inputs from slow-conducting MG-fibers were located in layer I. Type II neurons which received polysynaptic inputs from the MG were located in layers II-VI. Type III neurons which sent their axons to the AII or Ep were mainly located in layer III. Type IV neurons which sent their axons to the contralateral AI were located mainly in layer III. Type V neurons which received monosynaptic inputs from fast-conducting MG-fibers were located mainly in layer IV. Type VI neurons which projected onto the inferior colliculus were located in the upper part of the layer V. Type VII neurons which projected onto the MG were located in layers V and VI.

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PubMed1985

Morphology and laminar organization of electrophysiologically identified neurons in the primary auditory cortex in the cat.

The morphology of electrophysiologically identified neurons was examined in the primary auditory cortex (AI) of the cat. After stimulation of the medial geniculate nucleus (MG), second auditory cortex, posterior ectosylvian gyrus, contralateral AI, or corpus callosum, intracellular potentials were recorded from AI neurons, which were then injected intracellularly with horseradish peroxidase and recovered. Layer IV neurons, which receive MG fibers monosynaptically, are spiny and nonspiny stellate cells, small and medium-sized nonspiny tufted cells, and fusiform cells. They send their axons to layer III of the AI. Corticocortical AI neurons are medium-sized pyramidal cells in layer III. They receive axons from layer IV neurons of the AI and send their axons to layers I, II, IV, and V of the AI. Horizontal cells in layer I receive slow-conducting MG fibers monosynaptically, and send their axons to layer II of the AI. Stellate cells and small pyramidal cells in layer II receive afferent inputs polysynaptically from the MG. Layer II pyramidal cells receive afferent inputs from the MG via AI neurons in layers I and III, and send their axons to layers V and VI. The axons of layer II stellate cells were distributed within layer II. Pyramidal cells which send their axons to the MG are located in layers V and VI, distributing their axon collaterals to layers III-VI of the AI.

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PubMed1985

Multipolar neurons and axodendritic synapses in the mesencephalic trigeminal nucleus of the cat.

In the mesencephalic trigeminal nucleus (MTN) of the adult cat, multipolar neurons with 1-9 smooth dendritic processes were labeled with horseradish peroxidase which was applied to central cut ends of the masseter, deep temporal, medial pterygoid, superior alveolar and inferior alveolar nerves. These constituted 40% of the total population of MTN neurons; most of them were jaw-closing muscle afferent neurons and located mainly at the levels of the superior colliculus. Axon terminals were found electron microscopically to make synaptic contacts upon horseradish peroxidase-labeled dendritic profiles of MTN neurons.

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PubMed1985

Direct cortical projections to the parabrachial nucleus in the cat.

Direct projections from the cerebral cortex to the parabrachial nucleus in the cat were examined by the horseradish peroxidase (HRP)method. When HRP was injected into the parabrachial nucleus, retrogradely labeled neuronal cell bodies were seen, bilaterally with an ipsilateral predominance, mainly in the orbital gyrus, the lateral bank of the presylvian sulcus, and a restricted region in the infralimbic cortex on the medial surface of the frontal lobe (stereotaxic coordinates; Fr: 22, L: 1, H: -1); all labeled neurons were in deep pyramidal cell layer. After injecting HRP conjugated to wheat germ agglutinin (WGA-HRP) into the cortical regions where retrogradely labeled neurons were found after injecting HRP into the parabrachial nucleus, anterogradely labeled cortical fibers were traced to the parabrachial nucleus. Corticoparabrachial fibers originating from the orbital gyrus and the lateral bank of the presylvian sulcus ran ipsilaterally through the internal capsule and the cerebral peduncle down to the lower brainstem, whereas those from the infralimbic cortex coursed down ipsilaterally through the medial forebrain bundle. These cortical fibers to the parabrachial nucleus were distributed bilaterally with an ipsilateral predominance. Cortical fiber terminals in the parabrachial nucleus were topographically arranged: Corticoparabrachial fibers from the lateral bank of the presylvian sulcus ended most massively in the dorsal part of the lateral parabrachial nucleus. Corticoparabrachial fibers from the orbital gyrus ended most heavily in the medial parabrachial nucleus and less heavily in the lateral parabrachial nucleus. Corticoparabrachial fibers from the infralimbic cortex ended mostly in the parabrachial regions surrounding the brachium conjunctivum.

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PubMed1984

An anterograde-retrograde transneuronal transport of conjugates of wheat germ agglutinin with horseradish peroxidase (WGA-HRP): labeling of neurons in the reticular nucleus of the thalamus with WGA-HRP injected into the posterior column nuclei in the cat.

Neuronal cell bodies in the reticular thalamic nucleus (R) were labeled with wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) which was injected contralaterally into the posterior column nuclei (PCN) in the cat. The tracer was assumed to be transported to the posterolateral ventral thalamic nucleus (VPL), where it could escape from axon terminals of the PCN neurons and then be taken up by axon terminals of R neurons to label retrogradely the cell bodies of the R neurons.

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PubMed1984

Distribution of premotor neurons for the hypoglossal nucleus in the cat.

After injecting horseradish peroxidase into the hypoglossal nucleus, labeled neuronal cell bodies were constantly seen bilaterally with a slight ipsilateral dominance in the parvocellular reticular formation and reticular regions around the hypoglossal nucleus, ipsilaterally in the nucleus of Kölliker-Fuse, and contralaterally within the hypoglossal nucleus. A few labeled neurons were often found bilaterally with an ipsilateral dominance in the inter- and supratrigeminal regions around the motor trigeminal nucleus, parabrachial nucleus, ventral portions of the medial reticular formation of the pons and medulla oblongata, and dorsal tegmental regions and central gray of the midbrain.

Animals↗

PubMed1984

Thalamocortical projections to layer I of the primary auditory cortex in the cat: a horseradish peroxidase study.

HRP injected into layer I of the primary auditory cortex (AI) in the cat labeled neuronal cell bodies ipsilaterally in the medial, dorsal and ventrolateral divisions of the medial geniculate nucleus (MGN), suprageniculate nucleus, and nucleus of the brachium of the inferior colliculus. MGN neurons labeled after HRP injected into layer I were statistically smaller than those labeled after HRP injected into layer IV.

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PubMed1984

Distribution of premotor neurons for orbicularis oculi motoneurons in the cat, with particular reference to possible pathways for blink reflex.

After injecting horseradish peroxidase into the facial nucleus regions containing orbicularis oculi motoneurons, labeled neuronal cell bodies were found in the lateral medullary reticular formation, pretectal olivary nucleus, sensory trigeminal nuclei, lateral and medial parabrachial nuclei, ventromedial reticular formation medial to the facial nucleus, red nucleus and its surroundings, anterior horn of the upper cervical cord, medullary raphe nuclei, oculomotor nucleus and its surroundings, nuclei of Darkschewitsch, Cajal and Edinger-Westphal, ventral part of the midbrain central gray, pontine tegmentum, lateral vestibular nucleus and deep layers of the superior colliculus.

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PubMed1984

Identification of motoneurons innervating the tensor tympani muscle in the rabbit: a retrograde horseradish peroxidase study.

After injecting horseradish peroxidase into the tensor tympani muscle in the rabbit, neuronal cell bodies labeled retrogradely with the enzyme were seen in the ventrolateral regions of the pontine tegmentum. These tensor tympani motoneurons were located in the 'nucleus n' as well as in the rostrodorsal part of the medial 'cell group k' of Meessen and Olszewski [4].

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PubMed1983

Effects of stimulation of the primary auditory cortex upon colliculogeniculate neurons in the inferior colliculus of the cat.

Electrical stimulation of the primary auditory cortex (AI) of the cat was found to evoke EPSPs, IPSPs or EPSP-IPSP sequences in colliculogeniculate (CG) neurons in the inferior colliculus (IC) which responded antidromically to stimulation of the medial geniculate nucleus. The CG neurons responding to the AI stimulation with short-latency EPSPs (1.0-1.4 msec) were located in the dorsomedial portion of the central nucleus of the IC. On the other hand, latencies of IPSPs elicited in CG neurons by AI stimulation ranged from 2.0 to 4.5 msec.

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PubMedDate not supplied

Ischemic neuronal damage. How does mild hypothermia modulate it?

The significance of mild hypothermia as a therapeutic measure for ischemic brain damage is presented on the basis of different experimental results. An extracellular glutamate surge, a sustained activation of N-methyl-D-aspartate (NMDA) receptors, and an enhancement of DNA binding activity to transcription factor AP-1, all being key items directly linked to excitotoxic neuronal damage, are deeply affected by slightly lowering temperature (mild hypothermia [MH]). The cellular mechanism of MH seems rather nonspecific but tends to collectively involve these key items rendering neurons resistant to ischemic damage. Clinical application of MH should be a great challenge to relieve deadly effects on central neurons.

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PubMedDate not supplied

Optimal timing for application of ventricular assist devices in patients who cannot be weaned from cardiopulmonary bypass. An experimental study.

Missing the moment for application of ventricular assist devices (VAD) may be one of the major causes of multiple organ failure in patients who are to be weaned from cardiopulmonary bypass (CPB) with the aid of VAD. To determine the optimal timing for application of VAD in such patients, we examined the effect of a CPB assist on cardiac functional recovery from severe global ischemia using an experimental canine system. In the present study we created myocardial ischemia by clamping the aorta for 20 minutes (Group I; N = 7) or 45 minutes (Group II; N = 11) under normothermic CPB. The reliability of the method in creating severe cardiac failure was confirmed by testing the levels of adenosine triphosphate (ATP), creatine phosphate (CP), and lactate. After reperfusion of the myocardium, the heart was assisted by a totally vented CPB. The left ventricular end-systolic pressure-volume relationship (Emax), which is a load-independent index of contractility, was obtained every 15 minutes for up to 120 minutes of reperfusion. The Emax revealed that the function of the damaged heart recovers exponentially with time after reperfusion. From curves of the functional recovery of the heart, CPB support appeared to be beneficial for the first 60 minutes after reperfusion, and aided in the recovery of cardiac function in hearts damaged by global myocardial ischemia. However, CPB assist thereafter may not be effective in further improving cardiac function. We therefore concluded that the decision to use VAD should be determined by cardiac function by 60 minutes of reperfusion to avoid prolonging CPB time.

Adenosine Triphosphate↗