Biomedical subjects

R Arai

Publications and source records attributed to R Arai.

At least 73 records · Page 4Linked to original sources

PubMed1996

Aromatic L-amino acid decarboxylase is present in serotonergic fibers of the striatum of the rat. A double-labeling immunofluorescence study.

The aim of the present study is to examine whether serotonergic fibers of the striatum of the rat contain aromatic L-amino acid decarboxylase (AADC). By use of a double-labeling immunofluorescence method, we showed that AADC was localized in serotonergic fibers of the striatum and cerebral cortex as well as in serotonergic cell bodies of the midbrain raphe nuclei. We previously demonstrated that serotonergic fibers of the rat striatum contained dopamine after intraperitoneal injection of L-dopa. These findings suggest that dopamine is produced from the injected L-dopa in serotonergic fibers of the rat striatum.

Animals↗

PubMed1995

L-DOPA is converted to dopamine in serotonergic fibers of the striatum of the rat: a double-labeling immunofluorescence study.

The aim of the present study is to examine whether serotonergic terminals of the rat brain are induced to contain dopamine by L-DOPA administration. In rats that received intraperitoneally L-DOPA plus a peripheral decarboxylase inhibitor, we showed by use of a double-labeling immunofluorescence method that dopamine was localized in serotonergic fibers of the striatum and cerebral cortex as well as in serotonergic cell bodies of the midbrain raphe nuclei. In normal rats, no dopamine was detected in the serotonergic fibers or cell bodies. The finding suggests that a part of the administered L-DOPA may enter the serotonergic terminals and be converted to dopamine in the rat brain.

Animals↗

PubMed1995

Enhanced expression of tyrosine hydroxylase and aromatic L-amino acid decarboxylase in cerebellar Purkinje cells of mouse after hyperosmotic stimuli.

We examined by immunohistochemistry the effect of salt loading on the expression of tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC), and GTP cyclohydrolase I (GCH) in Purkinje cells of the mouse cerebellum. In control mice, only a few Purkinje cells were positive for TH or AADC. No Purkinje cells were stained for GCH. Drinking 2% sodium chloride for 2 weeks resulted in an increase in the number of TH- or AADC-positive Purkinje cells in the caudal vermis, paraflocculus and flocculus of the cerebellum. In contrast, no Purkinje cells were immunoreactive to GCH or L-DOPA after the salt loading. The present findings suggest that the salt loading differentially affects the expression of TH, AADC and GCH in Purkinje cells of the mouse cerebellum.

Animals↗

PubMed1995

Up-regulation of calretinin in the supraoptic nucleus of the rat after chronic salt loading.

We immunocytochemically examined the effect of chronic salt loading on the content of calretinin, a calcium-binding protein, in both the supraoptic nucleus and the magnocellular parts of the hypothalamic paraventricular nucleus. In control rats that were given water for drinking, the supraoptic nucleus contained a cluster of calretinin-stained cells. Drinking 2% sodium chloride solution for 7 days resulted in an increase of the staining intensity of calretinin in cells of the suprasoptic nucleus. In both the control and salt-loaded rats, the magnocellular parts of the paraventricular nucleus were almost devoid of calretinin-labeled cells. It is suggested that expression of calretinin in cells of the supraoptic nucleus is up regulated by chronic salt loading.

Animals↗

PubMed1995

Exogenous L-5-hydroxytryptophan is decarboxylated in neurons of the substantia nigra pars compacta and locus coeruleus of the rat.

The aim of the present study is to examine by immunohistochemistry whether exogenous L-5-hydroxytryptophan (L-5HTP) is decarboxylated in neurons of the substantia nigra pars compacta (SNC) and locus coeruleus (LC) of the rat. In normal rats, neurons of the SNC and LC stained intensely for aromatic L-amino acid decarboxylase (AADC). No serotonin (5HT)-positive cells were found in the two regions of the normal rats. In rats that were intraperitoneally injected with L-5HTP alone, the SNC neurons stained deeply for 5HT, but the LC neurons showed only a faint staining for 5HT. In rats that intraperitoneally received both a monoamine oxidase (MAO) inhibitor and L-5HTP, when compared with the L-5HTP-injected rats, the LC neurons became much darker in 5HT staining, but the SNC neurons showed only a slight increase in 5HT staining. The present findings suggest that (i) AADC in dopaminergic neurons of the SNC and in noradrenergic neurons of the LC can catalyze the in vivo decarboxylation of exogenous L-5HTP to produce 5HT, and (ii) most of the newly produced 5HT in the LC neurons is rapidly degraded by endogenous MAO.

5-Hydroxytryptophan↗

PubMed1995

Chemical features of monoaminergic and non-monoaminergic neurons in the brain of laboratory shrew (Suncus murinus) are changed by systemic administration of monoamine precursors.

5-Hydroxy-L-tryptophan (5-HTP) and L-3,4-dihydroxyphenylalanine (L-DOPA) were injected intraperitoneally (i.p.) into the laboratory shrew (Suncus murinus). Immunocytochemical and immunofluorescence studies were carried out on serial or same sections of the brain, which were reacted with specific antisera to dopamine (DA) or serotonin (5-HT) produced in our laboratory. We observed that cell bodies and nerve terminals of many catecholaminergic (CAnergic) neurons exhibited 5-HTP uptake and conversion of the precursor into 5-HT. However, the locus ceruleus showed scarcely any 5-HT immunoreactivity. This suggests that the precursor uptake mechanism may be different among various CAnergic groups. In contrast to these findings on CAnergic neurons, all serotoninergic (5-HTnergic) neurons after L-DOPA administration showed DA immunopositive reaction in their cell bodies and nerve terminals, suggesting that 5-HTnergic neurons may have the same capacity for precursor uptake. On the other hand, we observed that all aromatic L-amino acid decarboxylase (AADC)-only-positive neuron groups showed both DA and 5-HT immunoreactions after L-DOPA and 5-HTP administration, respectively, in the double-staining immunofluorescence method. From these results, AADC-only-positive neurons may be considered to belong to the amine precursor uptake and decarboxylation (APUD) system.

5-Hydroxytryptophan↗

PubMed1995

Distribution of nitric oxide synthase in the central nervous system of Macaca fuscata: subcortical regions.

The distribution of nitric oxide synthase-immunoreactive neurons was studied in the Macaca fuscata by immunohistochemistry using antiserum against nitric oxide synthase. In the macaque lower brainstem, many nitric oxide synthase-containing cell bodies were found in the gigantocellular and parvocellular reticular nuclei, the nucleus of the spinal tract of trigeminal nerve, the cochlear nucleus, the prepositus hypoglossi and the nucleus of the solitary tract. Many nitric oxide synthase-immunoreactive perikarya were observed in the laterodorsal-pedunculopontine tegmental nucleus complex of the macaque pontine and midbrain tegmentum. In addition, there were many highly immunoreactive cell bodies in the superficial layers of the inferior and superior colliculi. In the forebrain, numerous cell bodies were observed in the caudate nucleus, putamen, nucleus accumbens, nucleus of the diagonal band, anterior perforated substance and amygdaloid complex. Whereas most of these neurons were labeled highly intense for nitric oxide synthase, there were also many lightly labeled nitric oxide synthase-immunoreactive neurons in the substantia innominata, globus pallidus, ansa peduncularis and lateral hypothalamic nucleus. The present observation indicated some species difference in the distribution of central nitric oxide synthase-containing neurons. Furthermore, the present neuroanatomical evidence that nitric oxide synthase is distributed in a variety of specific neuronal systems, with some differences in the patterns of cytoplasmic localization, further indicates the neural messenger role of nitric oxide in the central nervous system.

Amino Acid Oxidoreductases↗

PubMed1995

Axonal transport of protein products of the bacterial reporter gene in the brain of transgenic mice.

The aim of the present study was to examine the intracellular localization of ectopically expressed proteins of the bacterial reporter gene in neurons of transgenic mice. In the brain of transgenic mice that carry a chimeric gene composed of the human tyrosine hydroxylase gene promoter and the bacterial gene encoding chloramphenicol acetyltransferase (CAT), the expressed CAT protein was previously found in catecholaminergic neurons as well as in non-catecholaminergic neurons expressing CAT ectopically. In the gene-expressing catecholaminergic neurons, the CAT protein was formerly detected in the axon terminals. In the present study, we immunocytochemically showed that the ectopically expressed protein was localized in cell bodies and axon terminals of the granule cells of the dentate gyrus. This suggests that the ectopically expressed protein of the bacterial gene is transported in the axons to their terminals.

Animals↗

PubMed1994

Immunohistochemical evidence that central serotonin neurons produce dopamine from exogenous L-DOPA in the rat, with reference to the involvement of aromatic L-amino acid decarboxylase.

The aim of the present study is to examine whether aromatic L-amino acid decarboxylase (AADC) catalyzes the conversion of exogenous L-3,4-dihydroxyphenylalanine (L-DOPA) to dopamine in serotonin neurons of the rat dorsal raphe nucleus. First, in order to confirm the localization of AADC in central serotonin neurons, we used an immunoperoxidase method for AADC and demonstrated that the distribution of AADC-containing neurons in the dorsal raphe nucleus corresponds very closely to the previous description on the distribution of serotonin-immunoreactive neurons. Second, in the rat that received intraperitoneally L-DOPA plus a peripheral AADC inhibitor, we used a double-labeling immunofluorescence method and showed that serotonin-stained neurons of the dorsal raphe nucleus were also immunoreactive to dopamine. The present result suggests that AADC decarboxylating L-5-hydroxytryptophan to serotonin in physiological conditions is also able to catalyze the in vivo decarboxylation of exogenous L-DOPA.

Animals↗

PubMed1994

Phenotypic changes of AADC-only immunopositive premammillary neurons in the brain of laboratory shrew Suncus murinus by systemic administration of monoamine precursors.

After 5-hydroxy-L-tryptophan (5-HTP) and L-3,4-dihydroxyphenylalanine (L-DOPA) were injected i.p. in the laboratory shrew Suncus murinus, immunocytochemical and immunofluorescence studies were conducted on continuous or same sections of the brain, using specific anti-tyrosine hydroxylase (TH), anti-aromatic L-amino acid decarboxylase (AADC), anti-dopamine (DA) and anti-serotonin (5-HT) antisera which were produced in our laboratory. The results of double-staining by the immunofluorescence method as well as immunoelectron microscopy strongly indicate that the cells of the premammillary nucleus of the laboratory shrew brain (AADC-only-positive neurons) are capable of synthesizing DA and 5-HT simultaneously upon simultaneous administration of L-dopa and 5-HTP.

Animals↗

PubMed1994

D-amino-acid oxidase is confined to the lower brain stem and cerebellum in rat brain: regional differentiation of astrocytes.

Based on enzymatic activity, the localization and the identification of D-amino-acid oxidase-containing cells in rat whole brain was systematically studied in serial fixed sections. The oxidase activity was absent or scarce in the forebrain, was confined to the brain stem (midbrain, pons and medulla oblongata) and cerebellum, and its localization was extended to the spinal cord. In the brain stem the oxidase was mainly localized in the tegmentum, particularly in the reticular formation. The intense oxidase reactions were present in the red nucleus, oculomotor nucleus, trochlear nucleus, ventral nucleus of the lateral lemniscus, dorsal and ventral cochlear nuclei, vestibular nuclei, nuclei of posterior funiculus, nucleus of the spinal tract of the trigeminal nerve, lateral reticular nucleus, inferior olivary nucleus, and hypoglossal nucleus. In the cerebellum the activity in the cortex was much more intense than that in the medulla. In all the fields described above, the oxidase-containing cells were exclusively astrocytes including Bergmann glial cells, and neither neuronal components, endothelial cells, oligodendrocytes nor ependymal cells showed oxidase activity. These results indicated that the astrocytes regionally differentiated into two distinct types, one of which expressed oxidase in the midbrain, rhombencephalon and spinal cord, and the other which did not in the forebrain. The localization of the oxidase was inversely correlated with the distribution of free D-serine in mammalian brains (Nagata, Y., Horiike, K. and Maeda, T., Brain Res., 634 (1994) 291-295). Based on the characteristic localization of the oxidase-containing astrocytes, we discussed the physiological role of the oxidase.

Animals↗

PubMed1994

Protein products of the bacterial reporter gene are found within axon terminals in the brain of transgenic mice.

The aim of this study is to examine whether protein products of the bacterial reporter gene are localized within axon terminals in transgenic mice. We have previously created transgenic mice carrying a chimeric gene composed of the human tyrosine hydroxylase gene promoter and the bacterial gene encoding chloramphenicol acetyltransferase (CAT). In the present study, we used an antiserum that detects specifically CAT, and examined immunocytochemically the brain of the transgenic mice. At a light microscopic level, CAT immunoreactivity was found in a dense plexus of fibers in the central nucleus of the amygdala, and in cell bodies of the ventral tegmental area. At an electron microscopic level, in the central nucleus of the amygdala, CAT immunoreactivity was observed in axon terminals. In the ventral tegmental area, the immunoreactivity was found in the perikaryal cytoplasm and on the microtubule of dendrites. The present findings suggest that protein products of the bacterial gene may be transported in axons up to their terminals, and also moved along the microtubules of dendrites.

Amygdala↗

PubMed1994

Heterogeneity in calbindin-D28k expression in oxytocin-containing magnocellular neurons of the rat hypothalamus.

We have used a double-labeling immunofluorescence method to examine whether oxytocin-containing magnocellular neurons possess a calcium-binding protein, calbindin-D28k, in the hypothalamus of the rat. In the supraoptic nucleus, most oxytocin-immunoreactive cells were also stained for calbindin-D28k. However, in the magnocellular part of the paraventricular nucleus nearly all oxytocin-labeled cells were devoid of calbindin-D28k. In the anterior commissural nucleus, approximately one-third of oxytocin-stained cells were also calbindin-D28k-immunoreactive, but the other cells were negative for calbindin-D28k. This study indicates that there may be distinct chemical features between oxytocin-containing magnocellular neurons of the supraoptic nucleus compared to those of the paraventricular nucleus.

Animals↗

PubMed1994

Expression of human tyrosine hydroxylase-chloramphenicol acetyltransferase (CAT) fusion gene in the brains of transgenic mice as examined by CAT immunocytochemistry.

We have produced transgenic (Tg) mice carrying 5.0-kb fragment from the 5'-flanking region of the human tyrosine hydroxylase (hTH) gene fused to a reporter gene, chloramphenicol acetyltransferase (CAT) [Sasaoka et al. (1992) Mol Brain Res 16: 274-286]. In the brain of the Tg mice, CAT expression has been observed in catecholaminergic (CAnergic) neurons and also in non-CAnergic neurons. The aim of the present study is to examine in detail the cell-type specific expression of the hTH-CAT fusion gene in the brain of the Tg mice, by use of immunohistochemistry for CAT, TH, and aromatic L-amino acid decarboxylase (AADC). CAT-immunoreactive cells were found in CAnergic brain regions which contained TH-positive cells, and also in non-CAnergic brain regions which contained no TH-labeled cells. The non-CAnergic brain regions that represented CAT-stained cells were further divided into two groups: (i) regions containing AADC-labeled cells, for example, bed nucleus of the stria terminalis, nucleus suprachiasmaticus, mammillary body, nucleus raphe dorsalis, inferior colliculus, and nucleus parabrachialis, and (ii) regions containing no AADC-positive cells, for example, main olfactory bulb (except A16), accessory olfactory bulb, nucleus olfactorius anterior, caudoputamen, septum, nucleus accumbens, hippocampus, medial nucleus of the amygdala, entorhinal cortex, nucleus supraopticus, and parasubiculum. The results indicate that the 5.0-kb DNA fragment flanking the 5' end of the hTH gene may contain the element(s) specific for neuron-specific TH expression but which may be insufficient to attenuate ectopic expression.

Animals↗

PubMed1994

Distribution of calretinin, calbindin-D28k, and parvalbumin in the rat thalamus.

The localization of three calcium-binding proteins, calretinin, calbindin-D28k, and parvalbumin, in the rat thalamus was immunohistochemically examined. a) Some thalamic regions revealed cells almost exclusively containing one of the calcium-binding proteins. For example, almost only calretinin-stained cells were found in the central medial and paraventricular nuclei. Calbindin-D28k-stained cells were mostly found in the centrolateral, interanteromedial, anteromedial, and posterior nuclei. Only parvalbumin-positive cells were found in the central part of the reticular nucleus. b) Other regions expressed overlap between the distributions of two cell components composed of different calcium-binding proteins. For example, both calretinin-stained cells and calbindin-D28k-labeled cells were found in the lateroposterior, intermediodorsal, rhomboid, and reuniens nuclei. c) Other regions showed no cells stained for any of the calcium-binding proteins. For example, generally no calcium-binding protein was detected in neurons of the anterodorsal, anteroventral, ventrolateral, ventral posterolateral, ventral posteromedial, or gelatinosus nuclei, or of the central part of the mediodorsal nucleus. These three proteins serve as useful marker for localizing subpopulations of neurons within the thalamus.

Animals↗

PubMed1993

Colocalization of calbindin-D28k with vasopressin in hypothalamic cells of the rat: a double-labeling immunofluorescence study.

By use of a double-labeling immunofluorescence method, we examined whether vasopressin-containing cells possess a calcium-binding protein, calbindin-D28k, in the hypothalamus of the rat. Subpopulations of vasopressin-containing cells varied in their ability to possess calbindin-D28k immunoreactivity in different regions. In the supraoptic nucleus, most vasopressin-immunoreactive cells were also stained for calbindin-D28k. By contrast, in the magnocellular part of the hypothalamic paraventricular nucleus, all vasopressin-labeled cells lacked calbindin-D28k. In the suprachiasmatic nucleus, no calbindin-D28k was found in vasopressin-stained cells. This study shows a further characterization of vasopressin-containing cells of the rat hypothalamus.

Animals↗

PubMed1993

Evidence for localization of the transgene product within axon terminals in the dentate gyrus of transgenic mice expressing human phenylethanolamine N-methyltransferase. A light and electron microscopic immunocytochemical study.

The aim of this study was to examine whether protein products of a transgene are localized within axon terminals in transgenic mice. We have previously created transgenic mice containing a chimeric gene composed of the human dopamine beta-hydroxylase gene promoter and the human phenylethanolamine N-methyltransferase (PNMT) cDNA. In the present study, we used an antiserum that detects specifically human PNMT but not mouse PNMT, and examined immunocytochemically the hippocampal formation of the transgenic mice. At a light microscopic level, immunoreactivity of human PNMT was found in fiber plexuses in the outer molecular layer of the dentate gyrus, and in cell bodies of layer 2 of the entorhinal cortex. At an electron microscopic level, in the outer molecular layer of the dentate gyrus, human PNMT immunoreactivity was observed in axon terminals that formed synapses with dendritic spines. The present study provides the evidence for localization of the transgene's protein products in axon terminals, suggesting axonal transport of the products.

Animals↗

PubMed1993

Immunohistochemical localization of calretinin-, calbindin-D28k- and parvalbumin-containing cells in the hypothalamic paraventricular and supraoptic nuclei of the rat.

The localization of three calcium-binding proteins, calretinin, calbindin-D28k and parvalbumin, in the hypothalamic paraventricular and supraoptic nuclei of the rat was immunohistochemically examined on adjacent sections and their distribution patterns were compared. Overlap between the distribution of calretinin-immunoreactive cells and that of calbindin-D28k-immunostained cells was found in the rostrodorsal part of the supraoptic nucleus, and the caudoventral part of this nucleus contained predominantly calbindin-D28k-stained cells. Cells of the medial and lateral magnocellular subdivisions of the paraventricular nucleus were almost devoid of the calcium-binding proteins examined. No parvalbumin-immunostained cells were observed in either nucleus. This study provides a further characterization of cell bodies in the hypothalamic paraventricular and supraoptic nuclei.

Animals↗