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R Arai

Publications and source records attributed to R Arai.

At least 55 records · Page 3Linked to original sources
PubMed1998

Dopamine-degrading activity of monoamine oxidase in locus coeruleus and dorsal raphe nucleus neurons. A histochemical study in the rat.

Dopamine-degrading activity of monoamine oxidase (MAO) was detected in the rat using a new histochemical method, with dopamine as the substrate. Our new method, designed to minimise the non-enzymatic oxidation of dopamine, was applied in combination with tyrosine hydroxylase (TH) and serotonin immunohistochemistry. We showed that the distribution pattern of MAO neurons was similar to that of TH-immunoreactive neurons (i.e. noradrenergic neurons) in the locus coeruleus (LC) and to that of serotonergic neurons in the dorsal raphe nucleus (DR). Since LC neurons form dopamine during noradrenaline biosynthesis, and DR neurons produce dopamine from exogenously administered L-dopa, our results indicate that dopamine produced in LC and DR neurons may be degraded, at least in part, by MAO.

Animals↗
PubMed1998

Phenylethanolamine-N-methyltransferase - immunoreactive nerve terminals afferent to the mouse substantia nigra.

In the substantia nigra pars compacta, many phenylethanolamine-N-methyltransferase immunoreactive (PNMT-ir) terminals as well as serotonin-ir terminals were observed for the first time to be very closely situated to the tyrosine hydroxylase (TH)-ir, aromatic L-amino acid decarboxylase-ir, and GTP cyclohydrolase I (GCH)-ir dopaminergic cells [Nagatsu, I., Arai, R., Sakai, M., Yamawaki, Y., Takeuchi, T., Karasawa, N. and Nagatsu, T., Neurosci. Lett., 224 (1997) 185-188]. Immunohistochemical colocalization of TH with GCH or PNMT in the somata and dendrites of TH-positive neurons in the rostral ventrolateral reticular formation of the medulla oblongata (C1 region, [Hokfelt, T., Fuxe, K., Goldstein, M. and Johansson, O., Brain Res., 66 (1974) 235-251]) was proved by a double-labeling immunofluorescence method with a confocal laser-scanning microscope, indicating that the neurons are adrenergic. These results suggest that dopaminergic neurons in the substantia nigra receive PNMT-ir, adrenergic afferents from the C1 region of the medulla oblongata.

Animals↗
PubMed1998

A dopamine-synthesizing cell group demonstrated in the human basal forebrain by dual labeling immunohistochemical technique of tyrosine hydroxylase and aromatic L-amino acid decarboxylase.

The human basal forebrain has been known to contain many neurons immunoreactive (ir) to tyrosine hydroxylase (TH; the first dopamine-synthesizing enzyme). We examined whether these neurons might contain aromatic L-amino acid decarboxylase (AADC; the second step dopamine-synthesizing enzyme) by dual labeling immunohistochemistry and confocal laser-scanning microscopy. Neurons dually-labeled for TH and AADC were found in the anterior olfactory nucleus, olfactory tubercle and the ventral margin of the rostral nucleus accumbens. The examination in the basal forebrain of the macaque monkey also gave substantially the same results. These neurons appear to constitute an independent dopaminergic cell group in the primate basal forebrain.

Adult↗
PubMed1998

Structure of the Chlorella Zepp retrotransposon: nested Zepp clusters in the genome.

Zepp elements found in the telomeric region of Chlorella chromosomes show the characteristic features of non-viral (LINE-like) retrotransposons, including a poly(A) tail, 5' truncations, a retroviral reverse transcriptase-like ORF and flanking target duplications. We have isolated and characterized a full-length Zepp element (8943 bp long) from Chlorella chromosome V. Some peculiar features of this element, including nested integration, two ORF structures, a long 3' noncoding region and a possible promoter region are compared with those of the Drosophila telomeric retrotransposons HeT-A and TART. The Chlorella chromosome-Zepp system appears to represent an intermediate stage between canonical telomerase-telomeres and Drosophila retrotransposon-telomeres.

Amino Acid Sequence↗
PubMed1998

Subcellular localization and possible function of actin, tropomyosin and actin-related protein 3 (Arp3) in the fission yeast Schizosaccharomyces pombe.

We investigated subcellular localizations and interactions of actin and two actin cytoskeleton-related proteins, Cdc8 tropomyosin and actin-related protein 3, Arp3, in the fission yeast Schizosaccharomyces pombe, using specific antibodies and by gene disruption. Actin was localized to the medial microfilamentous ring in the region of the septum during cytokinesis and to cortical patches by immunoelectron microscopy. F-actin cables were detected throughout the cell cycle by fluorescent staining with Bodipy-phallacidin. Cables were often linked to the patches and to the medial ring during its formation. Tropomyosin was localized to the medial ring and the cables. It was also distributed in the cell as patches, although co-localization with F-actin was not frequent. In cdc8ts mutant cells, F-actin cables were not observed although the F-actin patches were detected and cell polarity was maintained. These observations suggest that the F-actin cables may be involved in the formation of the medial ring, and that tropomyosin plays an important role in organizing both the ring and the cable, but is not involved in the F-actin patch formation or maintenance of cell polarity. Binding of Arp3 to actin was revealed by immunoprecipitation as well as by DNase I column chromatography. Arp3 seemed to form a complex with several proteins in the cell extracts, as previously reported for other organisms. Contrary to a previous report (McCollum et al., EMBO J. 15, 6438-6446, 1996), Arp3 was found to be concentrated in the medial region from early anaphase to late cytokinesis. Following arp3 gene disruption, F-actin patches were delocalized throughout the cell and cells did not undergo polarized growth, suggesting that Arp3 influences the proper localization of the actin patches in the cell and thereby controls the polarized growth of the cell.

Actin-Related Protein 3↗
PubMed1998

[Two cases of true hermaphrodite: the usefulness of laparoscopic gonadectomy in childhood. A case report].

Laparoscopic operation has been an alternative method in not only adults but children. We presented two children with true hermaphroditism who were performed by open gonadectomy and laparoscopic gonadectomy respectively. Both patients at the age of 4, and 2 years showed karyotypes of 46, XX, and were raised as girls. In the first case left ovary and right ovotestis were revealed by open gonadal biopsy and right ovotestis was removed by open surgery. In another case bilateral ovotestes were revealed by laparoscopic gonadal biopsy and resected by laparoscopic procedure. Laparoscopy was very useful for detecting the gonadal structures to confirm the diagnosis in intersex patients. True hermaphrodite is one of uncommon intersex anomalies, therefore the diagnosis should be made to demonstrate the coexistence of both ovarian and testicular tissues definitely. We estimated laparoscopic gonadectomy in pediatric true hermaphrodite and concluded that laparoscopic gonadectomy was as profitable as open gonadectomy.

Child, Preschool↗
PubMed1997

Demonstration of L-dopa decarboxylating neurons specific to human striatum.

In the human striatum, we immunohistochemically demonstrated many neurons that were immunoreactive for aromatic L-amino acid decarboxylase (AADC; the second step dopamine-synthesizing enzyme) but not for tyrosine hydroxylase (TH; the first step dopamine-synthesizing enzyme). The number of AADC-positive neurons was especially large in the ventral striatum including the nucleus accumbens. The significance of AADC-positive neurons are discussed in relation to the acting sites of L-dopa and antipsychotic drugs.

Adult↗
PubMed1997

Tyrosine hydroxylase (TH)-only-immunoreactive non-catecholaminergic neurons in the brain of wild mice or the human TH transgenic mice do not contain GTP cyclohydrolase I.

We previously reported the presence of transiently tyrosine hydroxylase (TH)-only-immunoreactive (ir), non-catecholaminergic (non-CAnergic) neurons in some brain regions of postnatal mice; anterior olfactory nucleus, medial geniculate nucleus, and spinal trigeminal nucleus, where CAnergic terminals but not cell bodies are present in the adult wild mouse. These transiently TH-ir brain regions of the postnatal wild mouse showed stable TH-immunoreactivity in the adult brain of the human TH transgenic (hTHTg) mice. TH expression was also observed in the nucleus parabigeminalis of the hTHTg mice. Using the antiserum against GTP cyclohydrolase I (GCH), first rate-limiting enzyme of the biosynthesis of tetrahydrobiopterin (BH4), the cofactor for TH, we proved that these TH-only-ir neurons in the wild mice and in the hTHTg mice were not stained with the antiserum against GCH. The results indicate that these TH-only-ir neurons which do not synthesize the BH4 cofactor do not produce dihydroxyphenylalanine, suggesting a new unknown function of TH in these neurons.

Adult↗
PubMed1997

Immunohistochemical colocalization of GTP cyclohydrolase I in the nigrostriatal system with tyrosine hydroxylase.

Immunohistochemical colocalization of GTP cyclohydrolase I (GCH) in the mouse nigrostriatal system with tyrosine hydroxylase or aromatic L-amino acid decarboxylase in the somata and terminals of GCH-positive catecholaminergic neurons are proved for the first time by a double-labeling immunofluorescence method with a confocal laser-scanning microscope. GCH-immunoreactive somata in the mouse substantia nigra have synaptic contacts with monoaminergic and non-monoaminergic terminals.

Animals↗
PubMed1997

Coexistence of tyrosine hydroxylase and serotonin in the raphe nucleus of the laboratory shrew (Suncus murinus) during postnatal life.

Immunoreactivity (IR) of tyrosine hydoroxylase (TH), which is the rate-limiting enzyme of catecholamine (CA) synthesis, was observed in the serotonergic neurons of the raphe nucleus (RN) of the newborn laboratory shrew from postnatal day (P) 0 to P14. Using an immunohistochemical method involving highly specific antibodies produced in our laboratory, we found that these RN neurons were TH-, GTP cyclohydrolase I-, aromatic L-amino acid decarboxylase-immunoreactive, but DOPA- and dopamine-immunonegative. In addition, they were tryptophan-, 5-hydroxytryptophan- and serotonin-immunoreactive. These results suggest that TH in serotonergic neurons of RN of laboratory shrew has no function as a CA-synthesizing enzyme but may play some role as a regulator or a subsidiary factor in the postnatal development of serotonergic neurons.

Animals↗
PubMed1997

Preferential localization of monoamine oxidase type A activity in neurons of the locus coeruleus and type B activity in neurons of the dorsal raphe nucleus of the rat: a detailed enzyme histochemical study.

Using enzyme histochemistry for monoamine oxidase (MAO) activity, we have examined whether MAO type A or type B or both are localized in neurons of the locus coeruleus (LC) and dorsal raphe nucleus (DR) of the rat. After pretreatment with various concentrations of the MAO type A inhibitor clorgyline or the type B inhibitor deprenyl, non-fixed frozen sections of the brain were histochemically stained for MAO activity with tyramine as a common substrate for the two types. MAO activity of the stained neuron was determined by measuring optical density of the staining. Percentage inhibition of the control MAO activity was plotted against increasing concentrations of the inhibitors. MAO activity of LC neurons was inhibited by low concentrations of clorgyline with a monophasic dose-response curve but not with a biphasic curve. Higher concentrations of deprenyl were needed to inhibit of LC neurons. MAO activity of DR neurons was inhibited by low concentrations of deprenyl with a monophasic dose-response curve. Clorgyline inhibited the MAO activity of DR neurons at only higher concentrations. When the sections without inhibitor pretreatment were incubated with the type A preferential substrate serotonin, the MAO activity was strongly stained in LC neurons but very weakly in DR neurons. With the type B preferential substrate beta-phenylethylamine, the staining was intense in DR neurons while very faint in LC neurons. These findings suggest that (i) almost all the MAO activity in LC neurons is of type A, and (ii) the MAO activity in DR neurons is predominantly of type B.

Animals↗
PubMed1997

The small GTP-binding protein Rho1 is a multifunctional protein that regulates actin localization, cell polarity, and septum formation in the fission yeast Schizosaccharomyces pombe.

BACKGROUND: The small GTP-binding protein Rho has been shown to regulate the formation of the actin cytoskeleton in animal cells. We have previously isolated two rho genes, rho1+ and rho2+, from the fission yeast Schizosaccharomyces pombe in order to investigate the function of Rho using genetic techniques. In this paper, we report the cellular function of Rho1. RESULTS: We found that Rho1 is essential for cell viability and cell polarity using gene disruption and by exogenous expression of botulinum C3 ADP-ribosyltransferase. In cells expressing either a constitutively active Rho1 or a dominant-negative Rho1, actin patches were delocalized. Both the cell wall and secondary septum were thick and stratified in cells expressing the constitutively active Rho1, while the cell wall of cells expressing the dominant-negative Rho1 seemed to be loosely organized. Furthermore, inactivation of Rho1 is apparently required for the separation of daughter cells. Cell fractionation studies suggested that Rho1 is predominantly membrane-bound. Moreover, we observed that Rho1 is localized to the cell periphery and to the septum. CONCLUSIONS: Rho1 is involved in actin patch localization, the control of cell polarity, the regulation of septation, and cell wall synthesis.

ADP Ribose Transferases↗
PubMed1997

Designing of plant artificial chromosome (PAC) by using the Chlorella smallest chromosome as a model system.

As a model for plant-type chromosomes, we have been characterizing molecular organization of the Chlorella vulgaris C-169 chromosome I. To identify chromosome structural elements including the centromeric region and replication origins, we constructed a chromosome I specific cosmid library and aligned each cosmid clones to generate contigs. So far, more than 80% of the entire chromosome I has been covered. A complete clonal physical reconstitution of chromosome I provides information on the structure and genomic organization of plant genome. We propose our strategy to construct an artificial chromosome by assembling the functional chromosome structural elements identified on Chrorella chromosome I.

Centromere↗
PubMed1996

Calretinin is differentially localized in magnocellular oxytocin neurons of the rat hypothalamus. A double-labeling immunofluorescence study.

By use of a double-labeling immunofluorescence method with a confocal laser scanning microscope, we have examined whether a calcium-binding protein, calretinin, is localized in magnocellular oxytocin and vasopressin neurons of the rat hypothalamus. In the supraoptic nucleus, all oxytocin-labeled cells were stained for calretinin. However, in the magnocellular part of the paraventricular nucleus, almost all oxytocin-stained cells were devoid of calretinin immunoreactivity. All vasopressin-positive cells of both the supraoptic nucleus and the magnocellular part of the paraventricular nucleus lacked calretinin immunoreactivity. No calretinin immunoreactivity was found in oxytocin-labeled cells of the the anterior commissural nucleus or in vasopressin-labeled cells of the suprachiasmatic nucleus. We previously showed that another calcium-binding protein, calbindin-D28k, was localized in magnocellular oxytocin neurons of the supraoptic nucleus but not in those of the paraventricular nucleus. These findings suggest that, in general, magnocellular oxytocin neurons of the supraoptic nucleus and those of the paraventricular nucleus can be chemically distinguished, that is, the former contain both calretinin and calbindin-D28k but the latter lack the two calcium-binding proteins.

Animals↗
PubMed1996

Transient appearance of GTP cyclohydrolase I--positive non-monoaminergic neurons in the ventral lateral geniculate nucleus of postnatal mice.

The transient appearance of GTP cyclohydrolase I (GCH)-immunoreactive (ir) cells in the ventral lateral geniculate nuclear region of mice was detected by use of an avidin-biotin peroxidase complex method with an antibody specific for an oligopeptide of rat GCH (residues from 12 to 23, GFPERELPRPGA). In this brain region, we found for the first time novel GCH-ir cells already at postnatal day 1 (P1). The numbers reached maximum at P14 and decreased until P29, and they had mostly disappeared by P56. These cells were tyrosine hydroxylase negative and aromatic L-amino acid decarboxylase negative, indicating a lack of dopamine or serotonin production, and thus do not belong to the monoaminergic neuron system.

Age Factors↗
PubMed1996

Transient appearance of tyrosine hydroxylase-immunoreactive non-catecholaminergic neurons in the medial geniculate nucleus of postnatal mice.

Tyrosine hydroxylase-immunoreactive (TH-ir) cells were found to appear transiently in the medial geniculate nuclear region of mice at postnatal day 7 (P7) by use of an avidin-biotin peroxidase complex (ABC) method for the first time. The numbers of TH-ir cells reached maximum between P14 and P21 and decreased until P29. These cells were GTP cyclohydrolase I-negative, aromatic L-amino acid decarboxylase-negative, and dopamine-negative. Thus, they do not belong to the catecholaminergic neuron system, because they lack dopamine production. The results suggest that TH in the cells in the medial geniculate nuclear region of mice has some new functions besides catecholamine biosynthesis.

Animals↗
PubMed1996

Dopamine produced from L-DOPA is degraded by endogenous monoamine oxidase in neurons of the dorsal raphe nucleus of the rat: an immunohistochemical study.

The aim of the present study is to examine by immunohistochemistry whether dopamine produced from L-DOPA in serotonin neurons of the rat brain is degraded by endogenous monoamine oxidase (MAO). In rats that received intraperitoneally L-DOPA plus a peripheral decarboxylase inhibitor, carbidopa, a cluster of dopamine-immunoreactive neurons was found in the dorsal raphe nucleus (DR). In L-DOPA/carbidopa-injected rats that were pretreated with an intraperitoneal injection of a MAO inhibitor, pargyline, when compared with the L-DOPA/carbidopa-injected rats without the pargyline pretreatment, neurons of the cluster of the DR became much darker in dopamine staining. The distribution of dopamine-stained neurons in the DR of these rats corresponded very closely to the previously reported distribution of serotonin-immunoreactive neurons of normal rats. In normal or only pargyline-injected rats, dopamine-stained neurons were scarcely observed in the DR. We previously showed that serotonin neurons of the rat DR were induced to contain dopamine by the injection of L-DOPA plus carbidopa. These findings suggest that the newly produced dopamine from L-DOPA in serotonin neurons of the rat DR is degraded by endogenous MAO.

Animals↗