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N Iwahori

Publications and source records attributed to N Iwahori.

At least 19 recordsLinked to original sources
PubMed1992

Differentiation of the brain stem structures in the salamander, Hynobius nebulosus.

Differentiation of the internal structure of the brain stem was analyzed in the salamander with special reference to neurons distributed in the marginal layer. It was found that the salamander brain stem was at first composed exclusively of the mantle layer. The marginal layer later differentiated peripherally. In these developmental stages, the mantle and marginal layers were clearly differentiated: the former was made up exclusively of the somata, while the latter was composed mainly of nerve fibers. As the development proceeded, these organization patterns were modified: a few cells migrated into the marginal layer. Cells migrating into the marginal layer formed various nuclei and layers such as the raphe nuclei, reticular formation and superficial cellular layers of the optic tectum. In later development stages, fibers in the marginal layer were myelinated, and neurons in the marginal layer were observed to become embedded among numerous myelinated fibers. Cytologically, the majority of neurons in early developmental stages were unipolar, extending a process peripherally into the marginal layer. In later developmental stages, neurons in a deep zone of the mantle layer remained unipolar, whereas those in the marginal layer and in the superficial zone of the mantle layer differentiated into multipolar cells. Thus, (1) the marginal layer differentiated peripherally as a cell free region; (2) cells in the mantle layer later migrated into the marginal layer, changing into multipolar neurons; (3) cells in the marginal layer formed reticular formation as well as various nuclei and layers in the peripheral white matter; and (4) as development proceeded, fibers in the marginal layer became myelinated.

Aging↗
PubMed1992

A Golgi study on the olfactory bulb in the red stingray, Dasyatis akajei.

The intrinsic organization of the olfactory bulb (OB) was studied in the red stingray using the rapid Golgi method. The OB is horse shoe-shaped, surrounding the equator region of the nasal capsule. As seen in the sagittal sections, the OB is round with the long olfactory peduncle extending from the dorsocaudal region and the olfactory fibers in a thick bundle entering from the rostroventral aspect. Although not so distinct, the following areas are distinguished. A rostroventral ovoid area adjacent to the entrance of the olfactory fibers consists exclusively of the olfactory fibers running in various directions. Dorsocaudal to the olfactory fiber area is a wide crescent region containing thin bundles of olfactory fibers, olfactory glomeruli, mitral cells and a few disseminated granule cells. A narrow crescent area made up of scattered granule cells is located dorsocaudally to the above wide crescent area. The outermost region consists of a fiber layer encapsulating the dorsal to caudal aspect of the OB. Thus, while the major constituents of the vertebrate OB are recognized, the lamination is very obscure.

Animals↗
PubMed1991

A Golgi study on the red nucleus in the mouse.

The intrinsic organization of the red nucleus (RN) was studied in the mouse using the rapid Golgi method. Cytoarchitecturally, the RN was divided into the magnocellular (RNmc) and parvocellular parts (RNpc). The former occupied the caudal one-third and the latter formed the rostral two-thirds of the RN. Based primarily on the size of somata, the RN neurons were classified into four types: giant, large, medium-sized and small neurons. Of these, the former two types of neurons were distributed mainly in the RNmc, while the latter two types of neurons were seen mainly in the RNpc. Axons of the RN neurons, at least those of the former three types of neurons, ran medially or caudomedially. Some axons ran across the mesencephalic raphe region to be lost in the medial region of the contralateral tegmentum. Two groups of afferent fibers to the RN were distinguished. Group I afferents were fibers composing the superior cerebellar peduncle. After crossing in the decussation of the superior cerebellar peduncle, these fibers entered the RN from the caudomedial aspect, ran rostrally in the nucleus emitting numerous collaterals. Group II afferents reached the RN from the ventrolateral aspect and traveled mediodorsally to be distributed totally within this nucleus.

Animals↗
PubMed1991

A Golgi study on the neuronal organization of the habenular ganglion in the red stingray, Dasyatis akajei.

The neuronal organization of the habenular ganglion (HG) was studied in the red stingray using the rapid Golgi method. The HG was made up of the medial (MH) and lateral habenular nucleus (LH), and the former nucleus was further divided into a dorsal, intermediate and ventral subnucleus. Only one type of neurons were observed in the MH, while the LH was composed of two types of neurons. In the left HG cut at the rostrocaudal middle of the ganglion, the LH was located in the dorsolateral region, while the dorsal, intermediate and ventral subnuclei of the MH occupied the dorsomedial, intermediate and ventral portions of the ganglion, respectively. In contrast, the right ganglion seen at this level was composed exclusively of the MH, with the dorsal, intermediate and ventral subnuclei located in the dorsomedial, intermediate and ventral portions, respectively. In the caudal level of the left ganglion, each nucleus was seen almost in the same region as in the level of the rostrocaudal middle, however, three subnuclei of the MH fused with the same subnuclei of the opposite side. In the right ganglion at the caudal level, the LH appeared in the intermediate area. The right LH was far smaller and was located more ventrocaudally than the left LH. On account of the LH, the intermediate subnucleus of the MH was divided into a dorsal and ventral part. The dorsal and ventral subnuclei of the MH remained in the same region as in the rostral level. Thus, the HG of the red stingray exhibited a striking left-right asymmetry, the most remarkable aspect of which was considered to be differences of the size, form and location of the LH between the left and right HG.

Animals↗
PubMed1991

A Golgi study on the afferent fibers to the habenular ganglion in the red stingray, Dasyatis akajei.

Afferent fibers to the habenular ganglion (HG) were derived mainly from the stria medullaris thalami (SM), which was roughly divided into a dorsal and ventral bundle. In the left ganglion seen at the level of the rostrocaudal middle, the dorsal bundle gave off collaterals to the lateral habenular nucleus (LH) and dorsal subnucleus of the medial habenular nucleus (MH), while the ventral bundle innervated the intermediate and ventral subnuclei of the MH. On the other hand, in the right ganglion at the level of the rostrocaudal middle, the dorsal subnucleus of the MH was innervated by collaterals from the dorsal bundle of the SM, whereas in the intermediate and ventral subnucleus fibers from the ventral bundle were seen. In the left ganglion at the caudal level, the dorsal and ventral bundle extended medially and joined the same bundle of the opposite side to constitute a dorsal and intermediate component of the habenular commissure, respectively. A third component of the HC, a ventral component, was seen to run between the fasciculus retroflexus of both sides. As in the case of the rostral level, the dorsal bundle of the SM emitted collaterals to the LH and dorsal subnucleus of the MH, while the intermediate and ventral subnuclei of the MH were projected upon by collaterals from the ventral bundle of the SM. At the caudal level of the right ganglion, the dorsal bundle gave off collaterals to the dorsal subnucleus of the MH. In contrast, the LH and the intermediate and ventral subnuclei of the MH were innervated by fibers from the ventral bundle. With regard to terminal patterns of the SM, fibers to the MH gave off many short fine branchlets forming the glomerular structures, whereas those to the LH branched out into numerous terminals to form a dense fiber plexus. Thus, the afferent fibers to the HG in the red stingray exhibited a striking left-right asymmetry.

Afferent Pathways↗
PubMed1990

Differentiation of the brain stem reticular formation in the triturus, Triturus pyrrhogaster.

The brain stem of the triturus was observed to be initially composed exclusively of the mantle layer. A few days before hatching, a narrow marginal layer differentiated peripherally. At the time of hatching, the marginal layer was clearly visible throughout the brain stem, except for in a medial region of the optic tectum. Approximately one week after hatching, a few cells migrated into the marginal layer, and almost simultaneously, a few fibers in that layer were myelinated. Cells migrating into the marginal layer formed reticular neurons as well as the raphe nuclei and superficial cellular layers of the optic tectum. As the development proceeded, the number of myelinated fibers in the marginal layer increased, and cells in that layer, especially reticular neurons, were seen to be embedded among numerous myelinated fibers, assuming the characteristic features of the reticular formation.

Animals↗
PubMed1989

A Golgi study on the main olfactory bulb in the snake Elaphe quadrivirgata.

The intrinsic organization of the main olfactory bulb in the snake was studied using the rapid Golgi method. A distinct laminar structure was recognized. From the periphery inward, the following layers were distinguished: the layer of the olfactory fibers, the olfactory glomeruli, the mitral cells, the deep fiber plexus, the granule cells and the ependymal cells. Olfactory fibers derived from the nasal cavity reached the entire surface of the bulb, forming a dense fiber plexus, then swung deeply and terminated in the olfactory glomeruli which were arranged in 2-4 rows. The mitral cell layer occupied a wide zone and was composed of scattered mitral cells. The mitral cells had 2-9 primary dendrites proceeding externally to terminate in the olfactory glomeruli and 2-4 secondary dendrites extending tangentially in the mitral cell layer to be distributed therein. The axons of the mitral cells travelled deeply and entered the layer of the deep fiber plexus. The deep fiber plexus was the path for the bulbar efferent and afferent fibers and could be traced caudally as the main olfactory tract, up to the anterior olfactory nucleus and vicinity. The granule cell layer was composed of small cells, the granule cells, packed closely with no special arrangement. The granule cells had long processes which extended superficially to be distributed mainly in the mitral cell layer. The ependymal cells were located at the deepest layer forming the wall of the olfactory ventricle and generated a long process which extended towards the surface to terminate in the peripheral portion of the bulb. In the snake bulb, the well-documented external and internal plexiform layers were considered to be included in the wide mitral cell layer. Thus, while several specific structures were observed, the fundamental organization of the main olfactory bulb in the snake seemed to be identical to that of the main olfactory bulb in various other vertebrate species.

Animals↗
PubMed1989

A Golgi study on the accessory olfactory bulb in the snake, Elaphe quadrivirgata.

The intrinsic organization of the accessory olfactory bulb (AOB) in the snake was studied using the rapid Golgi method. A distinct laminar organization was observed in the snake AOB. Beginning with the most superficial surface, the following layers were distinguished: the layer of the vomeronasal fibers, the olfactory glomeruli, the mitral cells, the deep fiber plexus, the granule cells and the ependymal cells. While the general organizational pattern of the snake AOB resembles that of the main olfactory bulb (MOB) and the AOB reported in various vertebrate species, the present study shows that: (1) the external and internal plexiform layers cannot be identified as independent layers and are considered to be included in the mitral cell layer; (2) the afferent and efferent paths, which are disseminated in the granule cell layer in the mammalian MOB, accumulate external to the granule cell layer to form the layer of the deep fiber plexus: and (3) as a result of accumulation of the afferent and efferent paths in the layer of the deep fiber plexus, the granule cell layer is very fiber-sparse. These structural patterns are quite similar to those of the snake MOB.

Animals↗
PubMed1987

A Golgi study on the inferior olivary nucleus in the red sting ray, Dasyatis akajei.

The intranuclear organization of the inferior olivary nucleus (ION) was studied in the red sting ray, using the rapid Golgi method. The ION neurons had polygonal, triangular or spindle cell bodies which generated 3-5 primary dendrites. These dendrites were relatively straight, sparsely spinous, and distributed mainly within the ION. The axons of the ION neurons extended medially and joined fiber bundles which ran transversely in the ION. Three groups of olivary afferents were distinguished: fibers derived from the tegmental area travelled ventrally and ended totally in the ION, composing a dense fiber plexus; collaterals of fibers which extended in a longitudinal direction in and around the ION distributed mainly in the lateral portion of the ION; and collaterals of fibers which ran transversely in the ION also ended in the ION. Some fibers from these 3 afferent groups converged to form pericellular baskets. Thus, the fundamental organization of the ION in the red sting ray was similar to that of the ION in mammals.

Afferent Pathways↗
PubMed1987

A Golgi study on the olfactory bulb in the lamprey, Lampetra japonica.

The intrinsic organization of the olfactory bulb in the lamprey was studied using the rapid Golgi method. Although not as discrete as in many vertebrates, a laminar organization was recognized. From the periphery inward, the following layers were discernible: the layer of the olfactory fibers, the olfactory glomeruli with the mitral cells, the granule cells, and the ependymal cells. Just beneath the surface of the olfactory bulb, the olfactory fibers extended over the entire bulb forming a dense fiber plexus terminating in the olfactory glomeruli which were arranged in one to two layers internally to the layer of the olfactory fibers. The mitral cells formed no discrete layer and were located mainly around the olfactory glomeruli. The mitral cells in the lamprey were lacking in secondary dendrites, but had two or more primary dendrites which terminated in the olfactory glomeruli. The axons of the mitral cells proceeded inwardly and accumulated diffusely in the granule cell layer which occupied a wide area internally to the layer of the olfactory glomeruli with the mitral cells. The granule cell layer was composed of densely packed small spindle or fusiform axonless cells, the processes of which extended superficially to be distributed in the olfactory glomeruli. At the deepest region of the bulb was a layer of the ependymal cells lining the surface of the olfactory ventricle. The external and internal plexiform layers were not evident. Thus, while the major constituents of the olfactory bulb of the vertebrate could be identified in that of the lamprey, the general laminar organization seemed indiscrete.

Animals↗
PubMed1987

A Golgi study on the neuronal organization of the neostriatum in the mouse.

The neuronal organization of the neostriatum in mice was studied, using the rapid Golgi method. Based on the size of the somata, the neostriatal neurons were divided into groups of large, medium-sized and small cells, and the neurons of each group were further divided into 2-5 types, according to the shape of the somata and dendritic morphology. Three types of large neurons were recognized. Large type I neurons were triangular, piriform or fusiform cells with a few thick dendrites, whereas large type II and type III neurons were round or polygonal cells with numerous slender dendrites. The dendrites of the large type II neurons were far longer than those of large type III. Medium-sized neurons were grouped into 5 types. Medium type I neurons were round with spiny dendrites and were found mainly in the caudal portion of the neostriatum. Medium type II neurons had numerous thin dendrites and were predominant in the rostral portion of the neostriatum. Some medium type II neurons were arranged in cell chains extending perpendicular to Wilson's pencils. The cell bodies of medium type III neurons were triangular, and generated long spiny dendrites. Medium type IV neurons were polygonal, and dendrites with numerous short branchlets were evidenced. Medium type V neurons had poorly branched and sparsely spinous dendrites. The small neurons were of two types: small type I had piriform cell bodies, which gave rise to very thin dendrites, while small type II had dendrites with irregular contours and filiform appendages. Of these, the large type I and type II, the medium type I-V, and the small type I neurons seemed to be the projection neurons, whereas the large type III and small type II neurons were merely internuncials. Thus, the neostriatum in the mouse was shown to be composed of a wide variety of projection neurons and only two types of interneurons.

Animals↗
PubMed1986

A Golgi study on the dorsal nucleus of the lateral lemniscus in the mouse.

The dorsal nucleus of the lateral lemniscus (DLL) in the mouse was studied using the rapid Golgi method. Three types of neurons were observed in the DLL. Type I neurons had a piriform or triangular cell body with a mean diameter of 14 by 19 micron, and emitted 3-5 primary dendrites. The cell bodies of type II neurons were either spindle or piriform in shape and were, on the average, 17 by 26 micron in diameter with 2-4 primary dendrites. Type III neurons had polygonal or triangular cell bodies which were 24 by 31 micron in average diameter and there were 4-6 primary dendrites. The axons of the DLL neurons most frequently traveled medially or ventromedially, and only a few could be followed dorsally among the fibers composing the lateral lemniscus (LL). The afferent fibers of the DLL were separated into three groups: ascending afferents, descending afferents and afferents from the medial aspect. The ascending afferents were collaterals of the LL fibers distributed mainly in the inferior colliculus. The descending afferents were also collaterals arising from the descending LL fibers. The afferents from the medial aspect ran across the tegmental area to distribute in the DLL. In addition, numerous LL fibers gave off terminal collaterals to the DLL. The ascending or descending nature of these LL fibers was not determined. Thus, the DLL is considered to be one of the commissural relay nuclei in the auditory system.

Afferent Pathways↗
PubMed1981

A Golgi analysis of the accessory optic fibers terminating in the medial terminal nucleus of the mouse accessory optic system.

Fibers of the accessory optic tract (AOT) terminating in the medial terminal nucleus (MTN) were observed in the mouse by the rapid Golgi method. The AOT fibers, which entered the MTN from its ventromedial aspect, were divided into thick and fine fiber groups, the thick fibers emitting many terminal collaterals of various calibers, and the fine ones generating fine terminal branches. The possibility exists that the retinal neurons sending AOT fibers to the MTN might be heterogeneous in nature.

Animals↗
PubMed1981

A Golgi study on the globus pallidus of the mouse.

The globus pallidus (GP) of the mouse was studied by the rapid Golgi silver impregnation method. The GP was composed of large and medium-sized neurons. The large neurons had stellate cell bodies with a mean diameter of 25 micron by 28 micron and five to seven primary dendrites. The somata of the medium-sized neurons were spindle or fusiform in shape, measured 19 micron by 27 micron in average and emitted three to five primary dendrites. The large neurons were located mainly in the central part of the GP, whereas the medium-sized neurons were observed in the peripheral part of the GP. Some GP neurons extended their dendrites into the caudatoputamen complex, sublenticular region or internal capsule. The axons of the GP neurons were seen most frequently to course medially or mediocaudally and to enter the internal capsule or fiber bundles traversing the GP; they were rarely observed to run laterally and to travel into the caudatoputamen complex. Some axons of the GP neurons were also observed to emit intra- or extra-nuclear collaterals extending into the sublenticular region. Four groups of afferent fibers to the GP were observed; (1) fibers descending within the internal capsule or caudatoputamen complex to terminate or to give axon-collaterals to the GP; (2) fibers ascending within the internal capsule or fiber bundles traversing the GP to enter the GP from its medial aspects; (3) fibers traversing the internal capsule laterally to terminate in the GP; and (4) fibers running dorsally through the sublenticular region to terminate in the GP. In addition to these four groups of afferent fibers, terminal branches were seen to arise numerously from many fibers running through the GP.

Afferent Pathways↗
PubMed1981

A Golgi study on the bed nucleus of the ansa lenticularis in the mouse.

The bed nucleus of the ansa lenticularis (BNAL) was studied by the rapid Golgi method in the mouse. It was composed of large and small neurons; the latter were the main constituents. Dendrites of the BNAL neurons were distributed only within the confines of the ansa lenticularis (AL). Axons of BNAL neurons ran ventromedially or dorsolaterally along the AL. Terminal fibers in the BNAL arose from fine collaterals of fibers running in the ventral portions of the lentiform nucleus.

Animals↗