Biomedical subjects

N Okado

Publications and source records attributed to N Okado.

At least 55 records · Page 3Linked to original sources

PubMed1991

Species differences in the distribution and coexistence ratio of serotonin and substance P in the monkey, cat, rat and chick spinal cord.

Serotoninergic raphe-spinal motor neuron projections exhibit wide species differences in both innervation pattern and coexistence of serotonin and substance P. The coexistence ratios vary widely ranging from more than 80% (rat) to less than 1% (chick). Serotonin and substance P positive fibers are also unevenly distributed in the ventral horn of different species: dense clusters of serotonin and substance P positive fibers were preferentially located in the motor neuron pools of extensor muscles of the hip joint (chick) as well as antigravity muscles of the forelimb (cat and rat).

Animals↗

PubMed1991

Serotonin-positive fibers within the spinal motor nucleus of the newborn rat, with special reference to co-localization of substance P.

Developmental changes of serotonin-positive fibers with special reference to co-localization with substance P was examined immunohistochemically in the ventral horn of rat lumbar spinal cord. Only about 20% of serotonin-positive fibers co-labelled with substance P on postnatal day (P) 0. The ratio of co-localization gradually increased, and reached the adult value by P28 (60-70%). Enkephalin-positive fibers were not co-localized with serotonin at any age examined. Although the densities of serotonin, substance P and enkephalin per unit area of the ventral horn gradually increased with development up to P28, the density of serotonin in the adult was decreased compared to P28 animals.

Afferent Pathways↗

PubMed1991

Descending input from the hypothalamic paraventricular nucleus to sympathetic preganglionic neurons in the rat.

The descending projection of the hypothalamic paraventricular nucleus (PVN) to the sympathetic preganglionic neurons (SPNs) in the upper thoracic cord of the rat was studied. PVN-fibers were labeled by anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA-L), while SPNs were retrogradely labeled with cholera toxin subunit B (CTb) which was injected into the superior cervical ganglion. SPNs labeled with CTb were mainly observed in the nucleus intermediolateralis (IML) pars principalis and pars funicularis, and a small number of them were in the nucleus intercalatus (IC) and central autonomic nucleus (CA). SPNs found in the IML had dendrites that projected in various directions. Five types of dendritic projections were noted: medial, rostral, caudal, lateral (including dorsolateral) and ventral. Longitudinal dendritic bundles interconnected each cell cluster in the IML. Medial dendrites of the IML, together with dendrites of the IC and CA, formed transverse dendritic bundles extending from the IML to the central canal. The transverse dendritic bundles disentangled near the midline and formed a loose dendritic plexus in the region just dorsal to the central canal. PVN-fibers labeled with PHA-L were observed primarily in lamina I and intermediate gray (lamina VII). Although varicose PVN-fibers and SPNs coexisted in the IML, the tight packing of the dendritic bundles prevented any clear demonstration of direct contacts between them. On the other hand, PVN-fibers were occasionally found to appose and wind around the primary or secondary dendrites of some SPNs of the CA and IC. These dendrites were studied with varicosities of PVN-fibers for a short length, and terminal boutons of PVN-fibers were also seen to make contact directly with the dendrities. The results of this study substantiated a direct connection between the PVN and SPNs, using a combination of immunohistochemical techniques for PHA-L and CTb. The possible involvement of a direct pathway from the PVN to SPNs in cardiovascular regulation is discussed.

Animals↗

PubMed1991

Coincidence of "ladder-like patterns" in distributions of monoaminergic terminals and sympathetic preganglionic neurons in the rat spinal cord.

A ladder-like pattern of distribution of sympathetic preganglionic neurons (SPNs) was compared with that of monoaminergic terminals in the upper thoracic spinal cord of the rat. SPNs were identified by a retrograde labeling with cholera toxin subunit B (CTb) injected into the superior cervical ganglia of both sides. Monoaminergic terminals were stained immunohistochemically by using antisera raised against 5-hydroxy-tryptamine (5-HT) or dopamine-beta-hydroxylase (DBH). SPNs showing full dendritic arbors were found in all of the sympathetic preganglionic nuclei. They formed a ladder in the horizontal plane. The nucleus intermediolateralis was connected with the central autonomic nucleus by many transverse dendritic bundles. Photomontages of serial sections of material stained alternatively with antisera against CTb and 5-HT or DBH clearly showed a close correlation between SPNs and monoaminergic terminals. There is no transverse dendritic bundle of SPNs without the accompaniment of monoaminergic terminals.

Animals↗

PubMed1991

Immunohistochemical study of tyrosine-hydroxylase-positive cells and fibers in the chicken spinal cord.

Tyrosine hydroxylase (TH)-positive cells and fibers were examined by immunohistochemistry in the chick spinal cord. TH-positive cells, which were located in laminae I, V and X, were most frequently found in the rostral part of the cervical spinal cord, with fewer cells being found in more caudal levels of the spinal cord. TH-positive cells located in lamina X, which were bipolar in shape, were mainly found in regions lateral as well as just ventral to the central canal. They had processes reaching to the central canal. The terminals of these cerebrospinal-fluid-contacting cells were oval in shape, and were most frequently found at the ventral wall of the central canal. There were dense clusters of TH-positive fibers in lamina X. A meshwork-like structure of TH-positive fibers was found over the lateral wall of the central canal. A high density of TH-positive fibers was also found in the medial part of laminae V-VII. In lamina IX, small numbers of TH-positive fibers were observed in the lateral motor column of the brachial spinal cord, and in the medial and lateral motor columns of the lumbosacral spinal cord. However, within the medial motor column of the brachial spinal cord TH-positive fibers were densely distributed around somal as well as dendritic profiles. Similar to our previous observations on serotoninergic fibers. TH-positive fibers were also differentially distributed in the ventral horn of the chicken spinal cord: a high density of TH-positive fibers was localized to specific regions of the spinal motor nucleus.

Animals↗

PubMed1990

Retrograde neuronal labelling by E. coli enterotoxin subunit B.

The present communication reports that subunit B of Escherichia coli heat-labile enterotoxin (LTB) can be utilized as a powerful tracer in neuroanatomical studies. LTB was injected into the limb muscle of the chick, or into the superior cervical ganglion of the rat. Sections were processed with an immunohistochemical technique using an antibody against LTB. After the LTB injection into the muscle, retrogradely labelled motoneurons were found: the entire extent of dendritic arborizations appeared labeled. After the LTB injection into the ganglion, virtually all of the preganglionic neurons were retrogradely labelled in the rat spinal cord.

Afferent Pathways↗

PubMed1990

Distribution patterns of dendrites in motor neuron pools of lumbosacral spinal cord of the chicken.

The morphology of dendritic trees (dendroarchitecture) of motor neurons innervating specific hindlimb muscles (motoneuron pools, MNP) was studied in the chick spinal cord. Motoneurons were labelled by intramuscular injections of horseradish peroxidase conjugated with cholera toxin subunit B. MNPs of posterior iliotibial and femorotibial muscles were located at the dorsolateral part of lateral motor column of lumbosacral segments (LS) 1-4 and 1-3, respectively. Although the dendritic profiles of femorotibialis motoneurons were fewer than those of posterior iliotibialis, these two MNPs had a similar distribution pattern of dendrites. Dendritic profiles were about equally distributed in the gray and white matter. Dendrites from the MNP of posterior iliotibialis radiated in all directions. A large number of dendrites penetrated into the white matter, and some even reached to the subpial regions of the lateral funiculus. One array of dendrites that projected dorsomedialwards extended to the base of the posterior horn. MNPs of both the iliofibularis (LS 4-7) and caudilioflexorius (LS 6-8) had dendritic trees with similar distribution patterns. There were two main arrays of dendritic extensions; one along the dorsal, and another along the ventral border of the lateral motor column. Dendrites from the iliofibularis and caudilioflexorius motoneurons were located more frequently in the white matter than in the gray matter. A large number of dendrites extended in all directions from the MNP of the adductor muscle, which was located in the medial region of lateral motor column of LS 1-2. The distribution of dendrites from a few other MNPs was also examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Evidence for two kinds of serotoninergic fibers in the ventral horn of spinal cord of the newly hatched chick.

We observed two types of serotonin-positive (5-HT) fibers in the ventral horn of the lumbar spinal cord of the newly hatched chicken: the first was composed of fine 5-HT fibers, which were increased transiently in the neuropil at 1 week after hatching (transient type); the second type consisted of thick fibers, which were densely localized around motoneuron somata in the motoneuron pools innervating extensor muscles of the hip joint (adult type). Pharmacological perturbation experiments demonstrated that these two types of 5-HT fibers may have different functions: the adult type of fibers may act to maintain an erect standing posture, whereas the transient type may act to induce or facilitate dendrogenesis (or dendritic elongation) of motoneurons. Thus, we concluded that 5-HT fibers may modulate neuronal transmission and serve as a kind of inductive agent for dendritic development in the chick spinal cord.

5,6-Dihydroxytryptamine↗

PubMed1989

Developmental changes in serotonin levels in the chick spinal cord and brain.

Developmental changes in 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in the developing chick spinal cord and brain were examined using high-performance liquid chromatography with electrochemical detection and immunohistochemistry. On embryonic day (E)6 only small amounts of 5-HT (0.086 ng) and 5-HIAA (0.0144 ng) were found in the spinal cord. By contrast, large amounts of 5-HT (x30) and 5-HIAA (x60) were detected in non-neuronal tissue outside the spinal cord; a similar distribution of 5-HT was also detected by immunohistochemistry. Up to E10, the highest concentrations of 5-HT in the spinal cord were found in the cervical region, followed by the thoracic and lumbar regions. In embryos older than E16, as well as in posthatched chicks, however, the highest and lowest concentrations of 5-HT were found in the lumbar and thoracic spinal cord, respectively. The concentration of spinal cord 5-HT reached maximal values on posthatching day (P)7, after which there was a marked decrease. By P120, 5-HT levels in the spinal cord decreased to the same level as on E10-E16. Concentrations in the brain, however, gradually increased with development. The basic pattern of development of 5-HIAA was similar to that of 5-HT.

Aging↗

PubMed1989

Cell death of motoneurons in the chick embryo spinal cord. X. Synapse formation on motoneurons following the reduction of cell death by neuromuscular blockade.

Chronic treatment of chick embryos with neuromuscular blocking agents, such as curare, rescues motoneurons from naturally occurring cell death. In the present study, embryos treated with curare from E6 to E9 had 35% more motoneurons than controls on E10 and 42% more than controls on E16. Previous studies have shown that several aspects of motoneuron differentiation occur normally in curare-treated embryos. We report here that dendrite growth and arborization is also unaltered on E10 and E16 following curare treatment. A quantitative analysis of afferent synapses on motoneurons shows that the packing density of both axosomatic and axodendritic synapses is also normal on E10 in curare-treated embryos, despite the greater number of motoneurons present. This indicates that the interneurons that provide presynaptic input to motoneurons are able to compensate for the increased number of synaptic sites made available by curare treatment. However, by E16 the packing density of synapses is reduced by about half. Because motoneurons and their dendrites continue to grow between E10 and E16, the further increase in synaptic sites made available in curare-treated embryos apparently exceeds the compensatory capacity of presynaptic interneurons on E16. One can conclude from these results that the increased survival of motoneurons in curare-treated embryos is not owing to an increase in afferent synapses. Motoneurons in these embryos continue to survive in the face of either no change (E10) or a reduction (E16) in the number of axodendritic and axosomatic synapses. Therefore, increased motoneuron survival in this situation is very likely regulated primarily by motoneuron-target interactions.

Animals↗

PubMed1988

Differential innervation of specific motor neuron pools by serotoninergic fibers in the chick spinal cord.

A new technique in which cholera toxin subunit B conjugated to horseradish peroxidase is injected in chick muscles followed by perfusion with Zamboni's fixative for serotonin immunocytochemistry allows one to visualize immunoreactive fibers and retrogradely labelled motoneurons in alternate sections. Using these procedures, we have found that there is a differential innervation by serotoninergic fibers of motoneuron pools that project to specific muscles or muscle groups. Dense clusters of serotonin-positive fibers were located in the motoneuron pools of extensors of the hip joint consisting of the lateral iliotibialis, ischioflexorius, iliofibularis, accessorius and caudilioflexorius muscles.

Animals↗

PubMed1988

Developmental changes in density and distribution of serotoninergic fibers in the chick spinal cord.

Developmental changes of serotoninergic innervation in the chick spinal cord (third lumbosacral segment) were examined with an immunohistochemical technique using an antiserum to serotonin. In the 1-day-old hatched chick, serotoninergic fibers were located in laminae I, II, VII, IX, and X. A large number of serotonin-positive fibers and terminals were found around somal profiles of large neurons and in the neuropil of the medial and lateral parts of the lateral motor column (LMC). In the 1-week-old chick, the density of serotoninergic fibers was greatly increased in the posterior columns, and serotoninergic fibers were most densely aggregated in the dorsolateral part of the LMC. In the 2-week-old chick, a considerable decrease in the density of serotoninergic fibers was observed in the lateral funiculus and the gray matter (laminae I, II, VII, IX, and X). In the LMC, serotonin-positive fibers and terminals were largely absent from the neuropil, but were found preferentially around the somal profiles of large neurons. Between 1 and 2 weeks after hatching the density of varicosities and terminals in the neuropil of the dorsolateral and medial parts of the LMC decreased by 33% and 56%, respectively. In the 3-month-old chick, the density of serotoninergic fibers in laminae I, II, V, VII, and X had increased compared to younger ages. Serotonin-positive fibers were not evenly distributed in the LMC of the adult chicken; rather, they were densely aggregated around the soma and proximal dendrites of motoneurons in the dorsolateral LMC. Many neuronal soma in the medial and intermediate regions of the LMC lacked serotoninergic fibers.

Animals↗

PubMed1988

The pattern of distribution of serotoninergic fibers in the anterior horn of the chick spinal cord.

The pattern of distribution of serotonin positive fibers in the motor nuclei of the chick spinal cord was examined immunohistochemically by using an antiserum against serotonin. A dense aggregation of serotoninergic fibers was located around anterior horn cells in the cervical spinal cord. In the brachial spinal cord, serotoninergic fibers were densely aggregated in the medial motor column and in the parts of the lateral motor column. There were two regions of serotonin immunoreactivity in the lateral motor column of the brachial spinal cord; one located in the ventromedial regions where a dense aggregation of serotoninergic fibers was found, and the reminder of the lateral motor column where only a few serotoninergic fibers were observed. The region containing a dense cluster of serotoninergic fibres around profiles of motoneuron somata and proximal dendrites appears to correspond to motor neuron pools of flexor muscles. In the thoracic spinal cord a high density of serotoninergic fibers was found in the motor nucleus. In the lumbosacral spinal cord (segments LS1-LS8) serotoninergic fibers were not observed in the medial motor column. However, there were five regions in the lateral motor column, where a high density of serotoninergic fibers was found. These very likely correspond to motor neuron pools of muscles which extend the hip joint.

Animals↗

PubMed1987

Pathway formation and the terminal distribution pattern of the spinocerebellar projection in the chick embryo.

Pathway formation and the terminal distribution pattern of spinocerebellar fibers in the chick embryo were examined by means of an anterograde labelling technique with wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP). Spinocerebellar fibers, which originate in the lumbar spinal cord and are located in the marginal layer of the spinal cord, reach the dorsal part of the cerebellar plate on embryonic day (E)8. On the way to the cerebellum the fibers form one distinct bundle, that suggests that gross projection errors probably do not occur during the formation of the spinocerebellar pathway. On E10, labelled fibers are located mostly in the medullary zone of the anterior lobe. By E12, the number of labelled fibers increases greatly in the inner granular and molecular layers. In transverse sections labelling was distributed throughout the mediolateral extent of the medullary zone. By E14, sagittal strips of labelling were clearly recognized in lobules II-IV; however, labelled terminals were present throughout lobule I. Although the adult pattern of terminal distribution is attained by E14, the mossy fiber terminals are still quite immature. The density of labelling decreased greatly by E16, and small terminal varicosities were first recognized. Structural differentiation of mossy fiber terminals continues to the end of the embryonic or the newly posthatched period.

Afferent Pathways↗

PubMed1987

The terminal distribution pattern of spinocerebellar fibers. An anterograde labelling study in the posthatching chick.

The terminal fields of spinocerebellar fibers from different levels (cervical, thoracic and lumbar) of the spinal cord in the chick were determined by using wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP), an anterograde labelling technique. More terminals were found in the anterior lobe than in the posterior lobe. Following injections in the lumbar spinal cord, mossy fiber terminals were found mostly in the anterior lobe (lobules I-V). The highest density of labelled terminals was found in lobule I, and labelled terminals were found in all parts of the lobule. However in lobules II-IV, labelled fibers were mediolaterally arranged in three longitudinal strips on both sides of the midline, and formed a distinct zonal distribution pattern. Labelled terminals were distributed evenly from the apical to basal regions of lobules I-V. A large number of mossy fiber terminals originating from the thoracic spinal cord were located in the anterior lobe and lobule VI; some labelled terminals were found in lobule IX. Three less distinct longitudinal strips, compared to those following WGA-HRP injections in the lumbar spinal cord, were recognized on each side of the midline. Labelled mossy terminals were observed in lobules II-IX following WGA-HRP injections in the cervical spinal cord. In transverse sections two longitudinal strips were found at the apical parts of lobules II and III, whereas four thin longitudinal strips were located in lobules IV and V. The present study showed that the terminal fields of spinocerebellar fibers from each level of the spinal cord have different distribution patterns.

Afferent Pathways↗

PubMed1986

Immunohistochemical study on the development of serotoninergic neurons in the chick: I. Distribution of cell bodies and fibers in the brain.

The ontogenetic development of the serotoninergic system in the embryonic as well as in posthatching chick brain was studied with an indirect immunohistochemical technique with the aid of a specific antibody to serotonin (5-hydroxytryptamine). By embryonic day 4, rostral and caudal groups of serotonin-immunoreactive cell populations appeared in the mesencephalon and rostral and caudal rhombencephalon. At this stage, the rostral group had a considerable number of labelled cells that sent axons toward more rostral parts of brain, whereas the caudal group consisted of a small number of scattered serotonin-immunoreactive cells. The number of serotonin-positive cells increased with development, such that by embryonic day 8 almost all the serotoninergic cell groups found in the adult chick were already present. Serotoninergic-positive cells appeared in the paraventricular organ of the diencephalon as early as embryonic day 10. Judging from the cytoarchitectural organization of serotonin-immunoreactive cells, all of the serotoninergic cell groups in the chick brain seemed to be fully developed by embryonic day 16. On embryonic day 4, serotonin-immunoreactive fibers were found to enter into the marginal layer of the mesencephalon. Subsequently, serotonin-positive fibers ascended in the marginal layer of the brainstem up to the levels of the diencephalon and to the telencephalon on embryonic day 6 and 8, respectively. Serotonin-positive fibers, which first began to penetrate into the mantle layer on embryonic day 8, reached to the rostral pole of the telencephalon by embryonic day 10. In general, serotonin fibers were found in almost all brain regions by embryonic day 16. However, "terminal formation" in some nuclei did not seem to begin until the late embryonic or posthatching period. These observations indicate that the initial development of serotoninergic cell groups occurs during the first half of the 20th day of the incubation period of the chick. However, a longer time, ranging from early embryonic to posthatching stages, is necessary for the complete development of the serotoninergic projections.

Animals↗

PubMed1986

Immunohistochemical study on the development of serotoninergic neurons in the chick: II. Distribution of cell bodies and fibers in the spinal cord.

Developmental changes of serotonin (5-hydroxytryptamine) neurons and fibers in the spinal cord of the embryo and posthatching chick were studied with immunohistochemical techniques with the aid of an antibody against serotonin. The first serotonin-immunoreactive fibers were found in the marginal layer of the cervical and lumbar spinal cord on embryonic days 6 and 8, respectively. There was a time lag of a few days between the first appearance of serotonin fibers in the marginal layer (embryonic days 6-8) and the time of penetration of serotonin fibers into the mantle layer (embryonic day 8 or older). The developments of serotonin innervation in the rostral parts of the spinal cord precedes that of caudal regions. Serotonin fibers penetrating into the mantle layer of the lumbar spinal cord were first found in lamina VII on embryonic day 8, whereas there were no serotonin-immunoreactive fibers in lamina IX by embryonic day 10. Large differences were found between embryonic day 16 and posthatching day 5 with regard to the density of serotonin varicosities and fibers in lamina IX, where profiles of soma and large-sized dendrites were heavily covered with varicosities. Laminae I and II first received serotonin fibers on embryonic day 16 and had a much denser innervation by posthatching day 5. There were no traces of serotonin fibers in lamina III in the stages examined up to posthatching day 5. Serotonin fibers were located in the lateral and ventral marginal layers in all specimens examined; only a few fibers were found in the dorsal marginal layer. Although few, serotonin-immunoreactive cell bodies were found in an area around the central canal of all animals from embryonic day 8 to adult. Some of these were located in the ependymal layer and sent processes toward the central canal; there were a small number of cells with long, fine processes. Serotonin-immunoreactive fibers in the spinal cord were not altered in regions rostral to the spinal transection, whereas all the serotoninergic fibers of the supraspinal origin were eliminated in the spinal cord caudal to the gap.

Animals↗

PubMed1986

Distribution and development of proenkephalin-like immunoreactivity in the lumbar spinal cord of the chicken.

Met5-enkephalin- (Met-ENK), Leu5-enkephalin-, Met5-enkephalin-Arg6-Phe7-, metorphamide- and BAM 22P-like peptides could be detected in the lumbar spinal cord of the chicken by immunocytochemistry and/or high performance liquid chromatography. However, a peptide identical to Met5-enkephalin-Arg6-Gly7-Leu8 could not be detected in the lumbar spinal cord of the chicken using an antiserum that was capable of detecting the octapeptide in mammalian tissues. Nerve fiber- and terminal-like processes containing proenkephalin-derived peptides were concentrated in the superficial laminae of the dorsal horn and along the midline rostral to the central canal. A lesser concentration of processes containing proenkephalin-derived peptides occurred in the medial and lateral motor columns of the ventral horn. The level of total radioimmunoassayable Met-ENK in the lumbar spinal cord of the chicken embryo increased more than 1000-fold between day 4.5 and day 18. A schedule of curare administration that had previously been shown to prevent naturally occurring somatic motoneuron death in the chicken lumbar spinal cord resulted in a two-fold increase in total radioimmunoassayable Met-ENK in the lumbar spinal cord.

Animals↗