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C Takayama

Publications and source records attributed to C Takayama.

At least 19 recordsLinked to original sources
PubMed2006

Developmental localization of potassium chloride co-transporter 2 in granule cells of the early postnatal mouse cerebellum with special reference to the synapse formation.

In the adult CNS, GABA is the predominant inhibitory neurotransmitter, mediating the hyperpolarization of membrane potential and regulating the glutamatergic activity. In the immature CNS, on the other hand, GABA mediates depolarization and is involved in controlling morphogenesis. This developmental shift in GABA actions from depolarization to hyperpolarization occurs as a result of decreasing the intracellular chloride ion (Cl(-)) concentration ([Cl(-)](i)) which is regulated by the potassium (K(+))-Cl(-) co-transporter 2 (KCC2). To clarify the time-course of changes in the GABA actions during development, we examined the developmental localization of the KCC2 in the granule cells of the postnatal mouse cerebellum using specific antibodies against KCC2. The granule cell precursors and migrating granule cells were devoid of immunoreactivity against KCC2 antibodies. At postnatal day 3 (P3), the KCC2-immunolabeling was negative in the internal granular layer, although synaptophysin-positive mossy fiber terminals were detected. At P5, we first detected the KCC2-immunolabeling at the somata of granule cells and their dendrites before granule cells received inhibitory input from Golgi cells. Almost all KCC2-positive dendrites (more than 98%) attached to and formed synapses with mossy fiber terminals. As development proceeded, the number of KCC2-positive granule cells increased, and all granule cells became positive by P21. These results suggested that GABAergic transmission on granule cells might shift from excitation to inhibition after the synapse formation, and the excitatory synapse-formation and related factors might be the triggers for the expression and localization of the KCC2 in the granule cells. Furthermore, it was also suggested that formation of the GABAergic synapses and GABAergic transmission were not necessary for the KCC2-expression in the mouse cerebellar granule cells in vivo.

Age Factors↗
PubMed2000

The postmitotic growth suppressor necdin interacts with a calcium-binding protein (NEFA) in neuronal cytoplasm.

Necdin, a growth suppressor expressed predominantly in postmitotic neurons, interacts with viral oncoproteins and cellular transcription factors E2F1 and p53. In search of other cellular targets of necdin, we screened cDNA libraries from neurally differentiated murine embryonal carcinoma P19 cells and adult rat brain by the yeast two-hybrid assay. We isolated cDNAs encoding partial sequences of mouse NEFA and rat nucleobindin (CALNUC), which are Ca(2+)-binding proteins possessing similar domain structures. Necdin interacted with NEFA via a domain encompassing two EF hand motifs, which had Ca(2+) binding activity as determined by (45)Ca(2+) overlay. NEFA was widely distributed in mouse organs, whereas necdin was expressed predominantly in the brain and skeletal muscle. In mouse brain in vivo, NEFA was localized in neuronal perikarya and dendrites. By immunoelectron microscopy, NEFA was localized to the cisternae of the endoplasmic reticulum and nuclear envelope in brain neurons. NEFA-green fluorescent protein (GFP) fusion protein expressed in neuroblastoma N1E-115 cells was retained in the cytoplasm and partly secreted into the culture medium. Necdin enhanced the cytoplasmic retention of NEFA-GFP and potentiated the effect of NEFA-GFP on caffeine-evoked elevation of cytosolic Ca(2+) levels. Thus, necdin and NEFA might be involved in Ca(2+) homeostasis in neuronal cytoplasm.

Animals↗
PubMed1997

Impaired parallel fiber-->Purkinje cell synapse stabilization during cerebellar development of mutant mice lacking the glutamate receptor delta2 subunit.

The glutamate receptor delta2 subunit (GluRdelta2) is specifically expressed in cerebellar Purkinje cells (PCs) from early developmental stages and is selectively localized at dendritic spines forming synapses with parallel fibers (PFs). Targeted disruption of the GluRdelta2 gene leads to a significant reduction of PF-->PC synapses. To address its role in the synaptogenesis, the morphology and electrophysiology of PF-->PC synapses were comparatively examined in developing GluRdelta2 mutant and wild-type cerebella. PCs in GluRdelta2 mutant mice were normally produced, migrated, and formed spines, as did those in wild-type mice. At the end of the first postnatal week, 74-78% of PC spines in both mice formed immature synapses, which were characterized by small synaptic contact, few synaptic vesicles, and incomplete surrounding by astroglial processes, eliciting little electrophysiological response. During the second and third postnatal weeks when spines and terminals are actively generated, the percentage of PC spines forming synapses attained 98-99% in wild type but remained as low as 55-60% in mutants, and the rest were unattached to any nerve terminals. As a result, the number of PF synapses per single-mutant PCs was reduced to nearly a half-level of wild-type PCs. Parallelly, PF stimulation less effectively elicited EPSCs in mutant PCs than in wild-type PCs during and after the second postnatal week. These results suggest that the GluRdelta2 is involved in the stabilization and strengthening of synaptic connectivity between PFs and PCs, leading to the association of all PC spines with PF terminals to form functionally mature synapses.

Animals↗
PubMed1997

Altered intracellular localization of the glutamate receptor channel delta 2 subunit in weaver and reeler Purkinje cells.

The glutamate receptor (GluR) channel delta 2 subunit is expressed abundantly and specifically in cerebellar Purkinje cells. Our previous study demonstrated that the GluR is expressed as early as embryonic day 15 prior to Purkinje cell synaptogenesis, and its protein product accumulates in dendritic spines during normal Purkinje cell maturation. In this study, we examined expression and distribution of the GluR delta 2 in the weaver and reeler mutant cerebelli, which show abnormal cytoarchitecture and neural circuitry. In situ hybridization analysis showed that GluR delta 2 mRNA was expressed in entire Purkinje cells in both mutant mice. Immunohistochemical analysis revealed that intracellular localization of GluR delta 2 was altered in some region of mutant cerebelli. In the cortical surface where Purkinje cells from synapses with parallel fibers, GluR delta 2-immunoreactivity was restricted to dendritic spines of Purkinje cells as observed in normal mice. In contrast, in the subcortical region where granule cells and parallel fibers are absent, the immunoreactivity was found widely in Purkinje dendrites. Thus, the GluR delta 2 protein did not accumulate to the dendritic spines of Purkinje cells lacking synaptic contact with parallel fibers. These results suggest that the expression of both GluR delta 2 mRNA and protein is independent of abnormalities in the mutant cerebelli, but relocalization of the GluR delta 2 protein might depend on the formation of synapses between Purkinje cells and parallel fibers.

Animals↗
PubMed1997

Identification of cell types producing RANTES, MIP-1 alpha and MIP-1 beta in rat experimental autoimmune encephalomyelitis by in situ hybridization.

The chemokines RANTES, macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta are members of the beta-family of chemokines and potent chemoattractants for lymphocytes and monocytes. To investigate the factors which regulate lymphocyte traffic in experimental autoimmune encephalomyelitis (EAE), we studied, by in situ hybridization analysis, the kinetics of mRNA expression and the potent cellular sources of RANTES, MIP-1 alpha and MIP-1 beta in the central nervous system (CNS) during the course of EAE. RANTES-positive cells appeared in the subarachnoid space and infiltrated the subpial region at around day 10, increased to a peak at days 12-13 and then decreased following the resolution of the acute phase of EAE, though elevated RANTES message expressions still remained on chronic subclinical stage. Most of RANTES positive cells were identified as T-lymphocytes located mainly around blood vessels, by combined studies of in situ hybridization and immunohistochemistry. The remainder of the RANTES-positive cells were astrocytes and macrophages/microglia. MIP-1 alpha and MIP-1 beta mRNA-positive cells appeared around day 10, increased further on days 12-13 and then gradually decreased. Most of the MIP-1 alpha- and MIP-1 beta-positive mononuclear cells were located around blood vessels. The kinetics of RANTES, MIP-1 alpha and MIP-1 beta expression paralleled those of the recruitment of infiltrating inflammatory cells and disease severity. Our observations support the possibility that chemokine production by T-cells, macrophages and astrocytes lead to the infiltration of inflammatory cells into the CNS parenchyma during the acute phase of EAE.

Animals↗
PubMed1997

Appearance of a fast inactivating voltage-dependent K+ currents in developing cerebellar granule cells in vitro.

To elucidate the molecular mechanisms that regulate the maturation of action potential, we began by examining voltage-dependent K+ currents, known to contribute to the maturation of action potential, of developing granule cells in mouse cerebellar microexplant cultures. The migration of developing granule cells in this culture is reported to mimic the in vivo process, but their specific identification is still incomplete. In this study, we identified and characterized granule cells in this culture. Immunocytochemical analysis found that granule cells migrated radially out from explants and subsequently formed small clusters and also that their morphology changed from a bipolar to a T shape during migration. Moreover, in the electrophysiological study, the GABA response of granule cells in this culture clarified that the electrophysiological properties of granule cells were normally maintained. We therefore have concluded, that this culture system is a powerful tool for investigating the differentiation of cerebellar granule cells. Based on these findings, we recorded voltage-dependent K+ currents of developing granule cells in this culture, while concurrently observing their morphology. Our results show that voltage-dependent K+ currents of developing granule cells change from delayed rectifier to A current in parallel with their morphological changes from bipolar to T-shaped cells.

Animals↗
PubMed1996

Developmental changes in expression and distribution of the glutamate receptor channel delta 2 subunit according to the Purkinje cell maturation.

The glutamate receptor (GluR) channel delta 2 subunit is considered to be a functional molecule involved in motor coordination, Purkinje cell synapse formation and cerebellar long-term depression. We examined developmental changes in expression and distribution of the GluR delta 2 in the mouse cerebellum by in situ hybridization and immunohistochemistry. The GluR delta 2 mRNA was detected as early as embryonic day 15 (E15) in a cell mass consisting of Purkinje neuroblasts in the posterior cerebellum. During late embryonic and postnatal periods, the GluR delta 2 mRNA was expressed abundantly and specifically in Purkinje cells. By immunohistochemistry, immunoreactivity of the GluR delta 2 was found in both shafts and spines of Purkinje dendrites at early postnatal period. By P21, however, the intense immunoreactivity became restricted to the dendritic spines, especially along the postsynaptic membrane in contact with parallel fiber terminals. These findings suggested that the transcription of the GluR delta 2 subunit occurs in the Purkinje cells from fetal through adult stage, but the intracellular localization of the protein products undergoes an alteration from non-synaptic to synaptic site when active synaptogenesis takes place.

Animals↗
PubMed1996

Impairment of suckling response, trigeminal neuronal pattern formation, and hippocampal LTD in NMDA receptor epsilon 2 subunit mutant mice.

Multiple epsilon subunits are major determinants of the NMDA receptor channel diversity. Based on their functional properties in vitro and distributions, we have proposed that the epsilon 1 and epsilon 2 subunits play a role in synaptic plasticity. To investigate the physiological significance of the NMDA receptor channel diversity, we generated mutant mice defective in the epsilon 2 subunit. These mice showed no suckling response and died shortly after birth but could survive by hand feeding. The mutation hindered the formation of the whisker-related neuronal barrelette structure and the clustering of primary sensory afferent terminals in the brainstem trigeminal nucleus. In the hippocampus of the mutant mice, synaptic NMDA responses and longterm depression were abolished. These results suggest that the epsilon 2 subunit plays an essential role in both neuronal pattern formation and synaptic plasticity.

Animals↗
PubMed1995

Impairment of motor coordination, Purkinje cell synapse formation, and cerebellar long-term depression in GluR delta 2 mutant mice.

Of the six glutamate receptor (GluR) channel subunit families identified by molecular cloning, five have been shown to constitute either the AMPA, kainate, or NMDA receptor channel, whereas the function of the delta subunit family remains unknown. The selective localization of the delta 2 subunit of the GluR delta subfamily in cerebellar Purkinje cells prompted us to examine its possible physiological roles by the gene targeting technique. Analyses of the GluR delta 2 mutant mice reveal that the delta 2 subunit plays important roles in motor coordination, formation of parallel fiber-Purkinje cell synapses and climbing fiber-Purkinje cell synapses, and long-term depression of parallel fiber-Purkinje cell synaptic transmission. These results suggest a close relationship between synaptic plasticity and synapse formation in the cerebellum.

Animals↗
PubMed1995

Light- and electron-microscopic localization of the glutamate receptor channel delta 2 subunit in the mouse Purkinje cell.

The localization of the glutamate receptor channel delta 2 subunit was investigated by immunohistochemistry. The delta 2-immunoreactivity was observed exclusively in the molecular layer of the cerebellar cortex. The electron microscopic analysis showed that the delta 2 subunit was localized in the dendritic spines of the Purkinje cells. The immunopositive spines often formed synaptic contacts with parallel fiber varicosities. As for the Purkinje cells ectopically localized in the cerebellar nuclei and brain stem, the dendritic shafts and cell bodies were strongly labeled. These ectopic Purkinje cells also formed asymmetrical synapses at the delta 2-immunopositive dendritic spines. Considering the specific localization of the delta 2 subunit in the postsynaptic site of the Purkinje cells, the subunit is suggested to be involved in the excitatory synaptic transmission in the cells, as a component of the glutamate receptor channel.

Animals↗
PubMed1995

[Clinical assessment of brain oxygen metabolism and function during cardiopulmonary bypass with induced hypothermia].

This study was designed to demonstrate the changes in brain metabolism/function, and to clarify the reason for assessing brain dysfunction during cardiopulmonary bypass (CPB) with systemic hypothermia. Fifteen patients, who received high-dose fentanyl anesthesia, for cardiac surgery under CPB were analysed concerning systemic hemodynamics, brain oxygen extraction, internal jugular venous oxygen saturation (SjVO2), glucose uptake, and compressed spectral array EEG for brain function. Internal jugular venous temperature decreased from 35.4 +/- 1.0 degrees C (mean +/- SD) at pre-CPB, to 22.3 +/- 1.6 degrees C during CPB. Systemic oxygen delivery decreased by 43% (P < 0.01) with coincided decrease in brain oxygen extraction by 31% (P < 0.01) during CPB. SjVO2 rose from 64.5 +/- 6.3% of pre-CPB level to 78.7 +/- 2.2% during CPB (P < 0.01). Glucose uptake decreased 71% during CPB (P < 0.01). EEG frequency slowed down from 9.0 +/- 0.6 Hz of pre-CPB level to 3.5 +/- 0.3 Hz during CPB (P < 0.01). No patient showed neurological complications during and after surgery. The predictable changes in the variables during brain ischemia/hypoxia may be increase in oxygen extraction, decrease in SjVO2, inhibition of metabolism and low EEG activity. During CPB, EEG activity exhibited identical trend as during ischemia/hypoxia, while the changes in brain oxygen extraction and SjVO2 did not. In conclusion, detection of brain dysfunction by monitoring brain oxygen metabolism or EEG is controversial during CPB using hypothermia.

Aged↗
PubMed1995

Reduced hippocampal LTP and spatial learning in mice lacking NMDA receptor epsilon 1 subunit.

The NMDA (N-methyl-D-aspartate) receptor channel is important for synaptic plasticity, which is thought to underlie learning, memory and development. The NMDA receptor channel is formed by at least two members of the glutamate receptor (GluR) channel subunit families, the GluR epsilon (NR2) and GluR zeta (NR1) subunit families. The four epsilon subunits are distinct in distribution, properties and regulation. On the basis of the Mg2+ sensitivity and expression patterns, we have proposed that the epsilon 1 (NR2A) and epsilon 2 (NR2B) subunits play a role in synaptic plasticity. Here we show that targeted disruption of the mouse epsilon 1 subunit gene resulted in significant reduction of the NMDA receptor channel current and long-term potentiation at the hippocampal CA1 synapses. The mutant mice also showed a moderate deficiency in spatial learning. These results support the notion that the NMDA receptor channel-dependent synaptic plasticity is the cellular basis of certain forms of learning.

Animals↗
PubMed1995

Cerebellum of the adult reeler mutant mouse contains two Purkinje cell populations with respect to gene expression for the N-methyl-D-aspartate receptor channel.

Recent studies have identified five NMDA receptor subunits, which exhibit distinct cellular expressions in the normal rodent brain. The purpose of this investigation is to clarify the molecular-anatomical organization in the cerebellum of the reeler mutant mouse, in which various categories of the Purkinje cells are present as to the cell position and synaptic connectivity. In comparison with the distribution of the inositol 1,4,5-trisphosphate receptor mRNA, a molecular marker specific to the Purkinje cells, the epsilon 1 subunit mRNA of the NMDA receptor channel was found in the adjacent sections to be expressed in a subset of the Purkinje cells. In the rostrocaudal extent, the Purkinje cells expressing the epsilon 1 subunit mRNA were distributed preferentially in the rostral cerebellum, irrespective of the normal and heterotopic positions. In the mediolateral extent, they formed segregated cell clusters, interposed by epsilon 1 subunit mRNA-negative clusters. Hybridizing signals for the zeta 1 subunit mRNA were found in all the Purkinje cell population, whereas those for the epsilon 2, epsilon 3, and epsilon 4 subunit mRNAs were not detected in the cells. These findings suggest that the reeler cerebellum is topographically compartmentalized by two subpopulations of the Purkinje cells, one expressing the epsilon 1 and zeta 1 subunit mRNAs, and the other expressing the zeta 1 subunit mRNA alone.

Animals↗
PubMed1995

Reduced spontaneous activity of mice defective in the epsilon 4 subunit of the NMDA receptor channel.

In an attempt to examine the functional significance of the molecular diversity of the N-methyl-D-aspartate (NMDA) receptor channel, we generated mutant mice defective in the epsilon 4 subunit by gene targeting technique. The epsilon 4 subunit mutant mice grew and mated normally. No epsilon 4 subunit protein was detected in the homozygous mutant mice, and the amount of the epsilon 4 subunit protein of 155 kDa was reduced in the heterozygous mice. The expressions of the other NMDA receptor channel subunit mRNAs were not appreciably affected by the mutation. The mutant mice exhibited no obvious histological abnormalities in the various brain regions and in the formation of whisker-related neuronal patterns (barrels, barreloids and barrelettes). In an open field test, however, the epsilon 4 subunit mutant mice showed a reduced spontaneous activity. No significant difference was found between the heterozygous and mutant mice in motor activity and anxiety tests. These results suggest that the epsilon 4 subunit of the NMDA receptor channel plays a role in vivo in controlling the spontaneous behavioral activity.

Analysis of Variance↗
PubMed1994

Altered distribution of inhibitory synaptic terminals in reeler cerebellum with special reference to malposition of GABAergic neurons.

In immunohistochemical reactions against glutamic acid decarboxylase (GAD), gamma-aminobutyric acid (GABA) and glycine (Gly), neurons in the mouse cerebellum showed the following reactivities: (1) the dendrites and cell bodies of the Purkinje cells were only GAD-positive, but their axonal terminals were GABA- and GAD-positive; (2) in both stellate and basket cells, the cell bodies and terminals were GABA- and GAD-positive but Gly-negative; (3) the Golgi cells were GABA-, GAD- and Gly-positive; (4) the granule cells were negative with all antibodies. Based on the populations of each type of neuron, identified by the properties mentioned above, the reeler cerebellum was divided into four regions, namely, (1) the molecular and Purkinje cell layers covering the surface of the cerebellum, where the stellate and basket cells were present as in normal mouse, (2) the granule cell layer, where the heterotopic Purkinje and stellate-type cells (including both stellate and basket cells) were present together with the granule and Golgi cells, (3) the region beneath the granule cell layer where Purkinje cells were present as clusters of several neurons, and in addition, the superficial zone of the central cell mass, where the stellate-type and Golgi cells were present among the Purkinje cells, and (4) the deep zone of the central cell mass, where the Golgi cells were exclusively present among the Purkinje cells. The heterologous synapses originating from inhibitory interneurons were formed on the Purkinje cells closely related to the distribution of these neurons.

Amino Acids↗
PubMed1993

Selective expression of the glutamate receptor channel delta 2 subunit in cerebellar Purkinje cells.

The primary structure of a putative subunit of the mouse glutamate receptor channel, designated as the delta 2 subunit, has been deduced by cloning and sequencing the cDNA. The delta 2 subunit has four putative transmembrane segments characteristic for neurotransmitter-gated ion channels, and shares 56% amino acid sequence identity with the delta 1 subunit of the mouse glutamate receptor channel and 14-24% identity with the subunits of the AMPA-, kainate- or NMDA-selective glutamate receptor channel. RNA blot and in situ hybridization analyses show that the delta 2 subunit mRNA is localized in cerebellar Purkinje cells. Furthermore, immunoblot and immunohistochemical analyses suggest that the delta 2 subunit protein is actually expressed in vivo in Purkinje neurons. The selective localization of the delta 2 subunit in Purkinje cells may imply a role of the delta 2 subunit in Purkinje cell-specific function such as the cerebellar LTD.

Amino Acid Sequence↗
PubMed1993

Abnormal synaptic architecture in the cerebellar cortex of a new dystonic mutant mouse, Wriggle Mouse Sagami.

The 'Wriggle Mouse Sagami (WMS)' is a new neurological mutant with severe dystonic movements of the trunk and extremities whose pathological characters are transmitted by an autosomal recessive gene (wri). Manifestations first appear at 10 days to 2 weeks after birth and progress until 12 weeks of age. In spite of the severe dystonic movements, no marked abnormalities had been found in the cyto- or myeloarchitecture of the central nervous system or that of the peripheral nerves, except for the impaired development of the dendritic trees of the Purkinje cells. In this study we quantitatively demonstrated decreased synaptic connections of parallel fibers on the dendritic spines of the Purkinje cells as early as 2 weeks after birth. On the other hand, synaptic boutons on the dendritic shafts and somata of the Purkinje cells and synaptic bouton-like structures which contained synaptic vesicles but without synaptic membrane specialization, were significantly increased in the molecular layer at 9 weeks of age. Glutamic acid decarboxylase immunohistochemistry suggested that some of these increased synaptic boutons and other bouton-like structures may have originated in GABA interneurons, such as stellate cells, basket cells and Golgi cells, and in the cerebellar nuclei. Because of the severity of the manifestations, it appears that synaptic alteration in interneurons also occurs in the other parts of the CNS.

Animals↗