Biomedical subjects

N Okado

Publications and source records attributed to N Okado.

At least 37 records · Page 2Linked to original sources

PubMed1999

The central distribution pattern of primary afferent fibers innervating the thigh muscle posterior iliotibialis in the chicken.

The anatomical relationship between motoneuron dendrites and primary afferent fibers innervating the same muscle were examined by using a modified cholera toxin tracing method. The cholera toxin B subunit conjugated with latex beads was injected into the posterior iliotibial muscle (PIT) of chicken. Both motoneuron dendrites and primary afferent fibers were intensely labeled. Labeled primary afferent fibers innervating the PIT were mainly located in laminae I (ventral part), V (lateral part), VI, VII (except ventromedial part) and lateral motor column (LMC, lamina IX) of the lumbar spinal cord. Numerous labeled primary afferent fibers were observed in proximity to the motoneuron pool of the PIT located in the dorsolateral region of the LMC; primary afferent fibers were closely apposed to somatic profiles of the PIT motoneurons.

Afferent Pathways↗

PubMed1999

[Mechanisms for formation and maintenance of synapses mediated by biogenic amines: pathogenesis and therapy of mental retardation and developmental disabilities by genetic and epigenetic factors].

Fibers of the global projection system ramify tremendously and distribute in the diverse region of the brain. Biogenic amines in the global projection system have been shown to facilitate formation and maintenance of synapses in the developing and adult brain. In terms of serotonin 5-HT2A receptor was shown to mediate the function of serotonin. We raised specific antibodies against 5-HT2A receptor protein. Virtually all the neurons in the cerebral cortex expressed 5-HT2A receptor. By using the function of biogenic amines to facilitate synapse formation and maintenance a novel approach can be developed in the neuroscience. That is to perturb biogenic amines, to change synaptic density, and to examine changes in the ability of learning and memory. Removing serotonin and acetylcholine for a week, at the maximum 58% of synapses are decreased in the hippocampus. The animals losing synapses spent a longer latency compared to intact animals in Morris water maze. The level of biogenic amines in the developing brain has been known to decrease tremendously by genetic diseases such as phenylketonuria, Down syndrome and autism as well as environmental factors such as nutrition and stress. In those situations synapses in the brain are suggested to be decreased. Synaptic mechanism for mental retardation and developmental disability by the cascade appears to contribute for understanding pathophysiology and a new therapy.

Animals↗

PubMed1998

Serotonin2A receptor-like immunoreactivity in rat cerebellar Purkinje cells.

In the present study we examined the distribution pattern of serotonin2A (5-HT2A) receptors in the rat cerebellum. A strong immunoreaction against 5-HT2A receptor protein was observed in Purkinje cells. A dense cluster of immunopositive dendritic profiles of Purkinje cells was located beneath the pia matter of cerebellar cortex. Somal profiles in the cerebellar nuclei had weak to moderate immunoreactions.

Animals↗

PubMed1998

The cellular localization of 5-HT2A receptors in the spinal cord and spinal ganglia of the adult rat.

The localization of serotonin2A (5-HT2A) receptors in the adult rat spinal cord and dorsal root ganglia was examined by using a polyclonal antibody that recognizes the C-terminus peptides of the mouse 5-HT2A receptor. Positive cell bodies of 5-HT2A receptor were found in several regions of the spinal cord. Generally, large-to-intermediate sized neuronal cell bodies were intensely immunolabeled. Motoneurons in the ventral horn were the most intensely labeled. Dot-like immunoreactive profiles were located beneath the cell membrane of motoneurons. Neuronal somata in the intermediolateral nucleus of the thoracic spinal cord were moderately labeled. The immunoreactivity in the dorsal horn was weak. A considerable number of glial cell bodies in the white matter were immunostained. The majority of both small and large sized neurons were 5-HT2A immunopositive in the dorsal root ganglion.

Age Factors↗

PubMed1998

Localization of 5-HT2A receptor in rat cerebral cortex and olfactory system revealed by immunohistochemistry using two antibodies raised in rabbit and chicken.

Serotonin 2A receptor (5-HT2A receptor) is widely distributed in the central nervous system, and has been suggested to be involved in a variety of behavioral conditions and neuropsychiatric disorders. Two polyclonal antibodies were raised against the N-terminus peptide of rat 5-HT2A receptor in chickens (5-HT2A-N) and a glutathione S-transferase fusion protein that contained the C-terminus of the mouse 5-HT2A receptor in rabbits (5-HT2A-C). Affinity-purified 5-HT2A-N and -C antibodies reacted strongly with a single band of 77-78 kDa in postsynaptic density proteins prepared from the rat cortex. The distribution pattern of immunoreactive structures in the rat brain was virtually the same for the two antibodies. The highest levels of immunoreactivity were observed in the olfactory bulb, neocortex, claustrum, piriform cortex, mamillary bodies, pontine nuclei, red nucleus and cranial motor nuclei. In the olfactory bulb, mitral cells were intensely labeled. In the neocortex, many immunoreactive neurons were found in layers II-VI. In layer IV of the neocortex, strong neuropil labeling was observed. In a double-labeling study using chicken 5-HT2A-N and rabbit anti-glial fibrillary acidic protein (GFAP) antibody, a considerable number of GFAP positive cells also showed 5-HT2A immunoreactivity. By using an immunoelectron microscopic technique, 5-HT2A receptor immunoreaction was shown to be localized just beneath the postsynaptic membrane thickening of asymmetric synapses.

Amino Acid Sequence↗

PubMed1997

Serotonin and acetylcholine are crucial to maintain hippocampal synapses and memory acquisition in rats.

Treatment with serotonin and acetylcholine depletors reduced the number of synapses in the rat hippocampus. Animals that received the drug treatment lost a substantial number of synapses and showed an apparent impairment in memory acquisition. Although the animals were behaviorally impaired following the treatment, spatial memory was nonetheless eventually attained despite the disappearance of long-term potentiation. These data suggest that synapses in the hippocampus that are normally maintained by serotonin and acetylcholine are crucial for normal acquisition of spatial memory. The number of synapses maintained by biogenic amines may be a basic mechanism for neurobehavioral plasticity.

Acetylcholine↗

PubMed1995

Regulation of synapse density by 5-HT2A receptor agonist and antagonist in the spinal cord of chicken embryo.

Identification of mechanisms that regulate the number of synapses in the brain has been a key issue for understanding the mechanism of plasticity. Here, we report that the density of synapses can be changed using an antagonist and/or an agonist of serotonin (5-HT) type 2A receptors in the chicken spinal cord. Because of the widespread distribution pattern of 5-HT fibers and 5-HT2A receptors in the central nervous system, 5-HT is thought to play a role in the formation and maintenance of synapses that are involved in normal brain function and mechanism of plasticity.

Amphetamines↗

PubMed1995

Oxytocinergic innervation to the upper thoracic sympathetic preganglionic neurons in the rat. A light and electron microscopical study using a combined retrograde transport and immunocytochemical technique.

A combination of retrograde cell body labeling and immunohistochemistry was employed to elucidate how oxytocinergic fibers make contact with sympathetic preganglionic neurons (SPNs) in the rat spinal cord from T1 to T4. SPNs were labeled retrogradely using cholera toxin subunit B (CTb) or horseradish peroxidase-conjugated CTb. Oxytocin-immunoreactive (ir) fibers were found in the intermediate zone, including the sympathetic preganglionic subnuclei. In the central autonomic nucleus and the intercalated nucleus, brown-stained oxytocin-ir varicosities or terminals were frequently observed to stud black-stained dendrites of SPNs. Electron microscopical observations showed that oxytocin-ir terminals form synapses with dendrites or soma of the sympathetic preganglionic neurons. The terminals contained numerous small clear round vesicles and a few large, cored vesicles. These results clearly show that a large proportion of SPNs are innervated by oxytocin-containing fibers. The origin of these fibers is discussed, and it is concluded that they are probably descending fibers from the paraventricular nucleus of the hypothalamus.

Animals↗

PubMed1995

Immunohistochemical examination of intraspinal serotonin neurons and fibers in the chicken lumbar spinal cord and coexistence with Leu-enkephalin.

Intraspinal serotonin-positive cells and fibers were examined in the chicken lumbar spinal cord following removal of descending serotonin fibers by spinal transection. Co-localization of Leu-enkephalin immunoreactivity in intraspinal serotonin cells was also examined using a double immunofluorescence labeling technique. By one or two weeks after spinal transection, virtually all supraspinal serotonin fibers were eliminated. Intraspinal serotonin cells were located ventral or ventrolateral to the central canal corresponding to laminae VII, VIII, and IX, and the anterior funiculus. Intraspinal serotonin cells sent fibers to (1) the pia mater on the ventral or ventrolateral surface of the spinal cord; (2) vessels in the spinal cord; (3) sympathetic preganglionic column of Terni; (4) other intraspinal serotonin neurons; (5) the central canal. Some 30%-50% of the intraspinal serotonin cells co-localized with Leu-enkephalin. Intraspinal serotonin fibers co-containing Leu-enkephalin were observed in the pia mater located on the most lateral surface of the spinal cord.

Animals↗

PubMed1994

Fyn expression during early neurogenesis in mouse embryos.

Fyn is a member of the Src family of tyrosine kinases which are thought to play important roles in cell to cell interactions during morphogenesis. The developmental profile of Fyn expression was examined using mutant mice in which lacZ gene was introduced into this locus. The expression was characteristic in the neural system. Though at low levels, it was detected in the headfold at embryonic day (E) 7.5 and in the luminal surface of neuroectoderm along the entire neural groove at E8.5. The expression appeared regional in rhombomeres at E8.5 and E9.5. Consistent expression was also found at a low level in the notochord. The expression was high in later stages of the neural tube which consists of three layers; it was in the marginal layer but not in the germinal layer. High expression was also found in developing dorsal root filaments of neural crest origin. Non-expression in dividing neuroepithelial cells and expression in developing neural fibers appeared ubiquitous features of Fyn expression throughout the entire brain.

Animals↗

PubMed1993

Synaptic loss following removal of serotoninergic fibers in newly hatched and adult chickens.

Neurotransmitters such as serotonin (5HT) may have nontransmitter, trophic-like functions in the developing and adult nervous system. In order to examine this possibility in the avian spinal cord, we have quantified synapse numbers on spinal neurons following treatment with drugs that result in the destruction of 5HT positive axons. Either p-chlorophenylalanine or reserpine was injected into newly hatched or adult chickens. Following treatment for 7 days the density of nonserotoninergic synapses was considerably decreased in the targets of 5HT fibers. By contrast, neither change was observed in the dendritic structures of spinal motoneurons or in the distribution of substance P and enkephalin positive fibers. These data suggest that 5HT may play an important role in the normal increase and maintenance of synapses in developing and adult animals. A lesion of 5HT neurons may not only alter neurochemistry but also alter the general synaptic structures of the brain. While 5HT containing fibers were depleted in a dose-dependent fashion we cannot rule out the possibility that other neurotransmitter systems were depleted at higher dose of PCPA and reserpine.

Animals↗

PubMed1993

Serotonin innervation patterns differ among the various medullary motoneuronal groups involved in upper airway control.

The purpose of this study was to test our hypothesis that the serotoninergic system plays a significant role in airway obstruction during sleep, by focusing on patterns of serotoninergic innervation of the medullary motoneurons involved in upper airway control. We used the combined techniques of retrograde labelling of motoneurons with unconjugated cholera toxin B and immunohistochemistry with antiserum against serotonin (5-HT). The retrograde tracers were injected into posterior cricoarytenoid (PCA), cricothyroid (CT), and genioglossal (GG) muscles of the cat. Motoneurons retrogradely labelled from PCA were identified ipsilateral to the injection site in the caudal part of nucleus ambiguus (NA). Serotonin immunoreactive terminals surrounded their somata and proximal dendrites, suggesting a strong influence of serotonin on the PCA-labelled motoneurons. Motoneurons retrogradely labelled from CT were located ipsilaterally in two distinct groups in the rostral NA and in the retrofacial nucleus (RFN). Selective peripheral nerve section revealed that the CT-labelled motoneurons in the NA had axons in the recurrent laryngeal nerve, whereas the other CT-labelled motoneurons in the RFN were innervated through the superior laryngeal nerve. In the RFN, the pattern of 5-HT innervation in relation to the CT-labelled motoneurons was analogous to that observed with the PCA-labelled motoneurons. In the NA, however, 5-HT terminals made few contacts with the CT-labelled motoneurons, although a dense network of 5-HT terminals was present in the surrounding region. In the GG-labelled motoneuron region of the hypoglossal nucleus, 5-HT terminals were apposed to distal dendrites, not to the soma, indicating less effect of serotonin on GG than on PCA activity. The present results demonstrated that the patterns of 5-HT innervation vary according to the type of motoneurons and their projections to the upper airway.

Animals↗

PubMed1993

Development of descending fibers to the rat embryonic spinal cord.

Onset and development of descending pathways to the rat embryonic spinal cord was examined by the use of retrograde transport of horseradish peroxidase (HRP). HRP was injected in the lower thoracic segments of the spinal cord of embryos ranging in age from embryonic day (E)14.5 to E20.5. A small number of labelled cells were found in the brain stem nuclei on E14.5: they were located in medullary as well as pontine reticular formation, lateral vestibular nucleus and interstitial nucleus of the medial longitudinal fasciculus. By E15.5 labelled cells were observed in the reticular formation of the caudal part of the medulla oblongata, medullary raphe nuclei, locus coeruleus, subcoeruleus nucleus, Barrington's nucleus and central gray of the midbrain. Cells in the red nucleus and in the nucleus of the solitary tract were labelled by E 16.5 and E17.5, respectively. Thereafter, labelled cells were first found in a few other nuclei: the gracile nucleus on E19.5 and the paraventricular nucleus on E20.5. The present study demonstrated that all the major supraspinal inputs except corticospinal fibers project to the lower thoracic spinal cord by E20.5.

Animals↗

PubMed1993

Regional localization of Fyn in adult brain; studies with mice in which fyn gene was replaced by lacZ.

Mutant mice in which beta-galactosidase gene (lacZ) was inserted into fyn locus were generated by homologous recombination in embryonic stem cells to examine the Fyn expression in the central nervous system. In adult brain, intensive beta-galactosidase activity was observed in olfactory bulb, cerebellum and hippocampus of the limbic system; the subcellular distribution of the activity was apparent not only in cell body but also in neural processes, and homozygous mutant mice live-born displayed an anatomical abnormality in the neural cell layer of the hippocampal formation. In spinal cord it was specifically expressed in dorsal horn, and in brain stem it was more characteristic in the sensory pathway, suggesting roles of Fyn in the sensory nervous network. In the white matter area, it was intense at postnatal day 10 but not detectable in adult, suggesting Fyn's role in myelinization.

Animals↗

PubMed1992

Immunohistochemical study on development of serotonin-, substance P-, and enkephalin-positive fibers in the rat spinal motor nucleus.

Developmental changes in the coexistence of serotonin and substance P/enkephalin within single fibers of lamina IX of the rat lumbar spinal cord were examined by the use of a double-labelling immunohistochemical technique. On postnatal day (P) 0, 65.0% of immunoreactive varicosities contained only serotonin, and 21.3% of them had both serotonin and substance P. The coexistent ratio of serotonin and substance P in single fibers increased with development: 61.9% of serotonin positive varicosities co-contained substance P on P28, similar to the ratio found in adult animals (67.4%). The ratios of varicosities containing only substance P remained the same from P0 to adult stage (about 15%). Enkephalin positive immunoreactivity was not co-localized with serotonin positive varicosities at any stage of development. Although numerous serotonin positive fibers were found in lamina IX, only a few substance P and enkephalin positive fibers were observed in the same area on P0. The density of serotonin positive varicosities increased slightly by P28, whereas substance P and enkephalin positive fibers increased considerably by this age. Between P28 and the adult stage, the density of serotonin positive fibers decreased by about 50%. The cross sectional area of axonal varicosities containing serotonin- and substance P-like immunoreactivity was similar in both P0 and adult animals, whereas that of enkephalin positive fibers was different. We also examined the coexistence of serotonin and substance P within single neurons of the caudal raphe nuclei in P7 and adult animals, and found that the coexistent ratio significantly increased with development.

Aging↗

PubMed1992

Morphology of sympathetic preganglionic neurons innervating the superior cervical ganglion in the chicken: an immunohistochemical study using retrograde labeling of cholera toxin subunit B.

Preganglionic sympathetic neurons (SPNs) in the chicken were demonstrated immunohistochemically using cholera toxin subunit B (CTb) as a retrograde tracer. After injection of CTb-solution into the superior cervical ganglion, labeled SPNs were mainly found in the ipsilateral sympathetic preganglionic column of Terni (the column of Terni), with only a few in the intermediate zone. They were observed from the caudal half of the 15th cervical segment to the rostral tip of the 3rd thoracic segment. Cell somata of SPNs were loosely packed within the column of Terni, where they had an elliptic shape with the long axis oriented rostrocaudally. In the horizontal plane three kinds of dendrites could be discriminated on the basis of their orientation. Longitudinally oriented dendrites emanated from the rostral and the caudal poles of the SPNs. Medially oriented dendrites were observed to cross the midline and enter the contralateral column of Terni, where they further branched to form a loose dendritic plexus; some extended beyond the lateral limit of the contralateral column of Terni to reach the intermediate zone. Laterally oriented dendrites formed periodically arranged dendritic bundles projecting into the intermediate zone. The present findings provide a detailed account of the dendritic organization of SPNs in the chicken, and suggest that avian SPNs share certain structural features in common with mammalian SPNs.

Animals↗

PubMed1992

Development of serotoninergic system in the brain and spinal cord of the chick.

(1) Development of serotonin positive cells and fibers was immunohistochemically studied by the use of an antibody against serotonin. (2) Serotoninergic neurons were first observed in the immature rohmbencephalon raphe nuclei on embryonic day (E)4, where two clusters of serotonin positive neurons were located: one observed at the rostral part of the rohmbencephalon corresponding to the dorsal raphe nuclei had many serotonin positive cells: the other located at the caudal part of the rohmbencephalon corresponding to the medullary raphe nuclei of the adult animals had only a small number of serotoninergic cells. (3) By E8 the number of serotonin positive cells in the brain stem increased, and virtually all the raphe nuclei found in an adult animal were located. (4) Serotonin positive fibers in the marginal layer reached up to the diencephalon and telencephalon on E6 and E8, respectively. (5) Serotonin positive cells were found beside the midline regions in the ventral part of the spinal cord of the embryonic as well as posthatching chick. (6) Because almost all the serotoninergic fibers in the spinal cord originated from the brain stem raphe nuclei, propriospinal serotonin positive cells were considered as phylogenetic vestiges. (7) Serotoninergic fibers were first found in the marginal layer of the cervical and lumbar spinal cord on E6 and E8, respectively. (8) There was a waiting period of a few days before they penetrated into the mantle layer. (9) Terminal arbolization of the serotoninergic fibers started from late embryonic periods (E16 less than), and was maximized within one week of hatching. (10) Thereafter the density of serotonin positive fibers decreased in all the regions of the spinal cord. (11) Developmental changes of the density of serotonin determined with a high performance liquid chromatography were the same as those determined through immunohistochemistry. Namely the density of serotonin increased linearly from E6 to hatching period, and reached the maximum value one week posthatching. (12( The density of the serotonin in the adult spinal cord was about half of the maximum value. (13) It is to say that the densities of serotonin and serotoninergic fibers transiently increased around one week posthatching. (14) Following the transient increase serotoninergic fibers were eliminated from the neuropil, the fibers were localized in the specific regions of the motor nucleus: motor neuron pools of extensor muscles of the hip joint in the lumbosacral spinal cord.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Identification of Pseudomonas aeruginosa by using a disk of phenanthroline and 9-chloro-9-[4-(diethylamino)phenyl]-9,10-dihydro-10-phenylacridine hydrochloride and by cell agglutination testing with monoclonal antibodies.

To establish a simple identification procedure for Pseudomonas aeruginosa, we developed a disk consisting of phenanthroline and 9-chloro-9-[4-(diethylamino)phenyl]-9,10-dihydro-10- phenylacridine hydrochloride (PC disk). Nine of 248 P. aeruginosa isolates and all other oxidase-positive gram-negative isolates (143 isolates) had clear inhibition zones around the PC disk. Of these nine P. aeruginosa isolates, seven produced a blue, blue-green, or green pigment on Mueller-Hinton agar after 24 h of incubation. The sensitivity and specificity of the PC disk susceptibility test in combination with pyocyanin production were 99 and 100%, respectively. Ten P. aeruginosa isolates showed no agglutination reactions with monoclonal antibodies against P. aeruginosa (96% sensitivity and 100% specificity).

Acridines↗