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C Akazawa

Publications and source records attributed to C Akazawa.

28 records · Page 2Linked to original sources
PubMed1994

Differential expression of five N-methyl-D-aspartate receptor subunit mRNAs in the cerebellum of developing and adult rats.

Five N-methyl-D-aspartate (NMDA) receptor subunits have been identified thus far: NR1, NR2A, NR2B, NR2C, and NR2D. Here, we have analyzed the expression patterns of mRNAs for the NMDA receptor subunits in the developing and adult rats by in situ hybridization. The developmental changes of the expression patterns were most salient in the cerebellum. In the external granular layer, hybridization signals of mRNAs for NR1, NR2A, NR2B, and NR2C appeared by postnatal day 3, but no NR2D mRNA was expressed at any developmental stage examined. The NR1 mRNA was expressed in all cerebellar neurons at all developmental stage examined. The NR1 mRNA was expressed in all cerebellar neurons at all developmental stages examined. The signals for the NR2A mRNA appeared in Purkinje cells and granule cells during the second postnatal week. The signals for the NR2B mRNA in granule cells were seen transiently during the first 2 weeks after birth. The signals for NR2C mRNA appeared in granule cells and glial cells during the second postnatal week. The signals for NR2D mRNA appeared transiently in Purkinje cells during the first 8 postnatal days; in adult rats, these were seen in stellate and Golgi cells. In the cerebellar nuclei, mRNAs for NR1, NR2A, NR2B, and NR2D were more or less expressed on postnatal day 0, while expression signals for the NR2C mRNA were first detected in postnatal day 14. Thus, the most conspicuous changes of expression patterns were observed in the cerebellar cortex during the first 2 weeks after birth, when development and maturation of the cerebellum proceed most rapidly.

Animals↗
PubMed1994

Expression of mRNAs of L-AP4-sensitive metabotropic glutamate receptors (mGluR4, mGluR6, mGluR7) in the rat retina.

Expression patterns of mRNAs of L-AP4-sensitive metabotropic glutamate receptors (mGluR4, mGluR6, mGluR7) in the rat retina were examined by northern blot analysis and in situ hybridization histochemistry. Expression patterns of mGluR4 and mGluR7 mRNAs were quite different from that of mGluR6 mRNA which was expressed at the outer part of the inner nuclear layer. The mGluR4 mRNA was expressed on the cell bodies of the ganglion cells, but not in the inner or outer nuclear layer. The expression of mGluR7 mRNA was observed throughout the entire region of the inner nuclear layer and on the cell bodies of the ganglion cells.

Aminobutyrates↗
PubMed1994

Molecular characterization of a new metabotropic glutamate receptor mGluR7 coupled to inhibitory cyclic AMP signal transduction.

A cDNA clone for a new rat metabotropic glutamate receptor termed mGluR7 was isolated through polymerase chain reaction-mediated DNA amplification by using primer sequences conserved among the metabotropic receptor (mGluR) family and by the subsequent screening of a rat forebrain cDNA library. The cloned mGluR7 subtype consists of 915 amino acid residues and exhibits a structural architecture common to the mGluR family with a large extracellular domain preceding the seven putative membrane-spanning domains. mGluR7 shows the highest sequence similarity to mGluR4 and mGluR6 among the members of the mGluR family. Similar to mGluR4 and mGluR6, mGluR7 inhibits forskolin-stimulated cyclic AMP accumulation in response to agonist interaction and potently reacts with L-2-amino-4-phosphonobutyrate and L-serine-O-phosphate in Chinese hamster ovary cells transfected with the cloned cDNA. RNA blot and in situ hybridization analyses of mGluR7 mRNA indicated that it is widely expressed in many neuronal cells of the central nervous system and is thus different from the more limitedly expressed mGluR4 or mGluR6 mRNA. mGluR7 together with mGluR4 thus corresponds to the putative L-2-amino-4-phosphonobutyrate receptor which plays an important role in modulation of glutamate transmission in the central nervous system.

Amino Acid Sequence↗
PubMed1993

Molecular characterization of NMDA and metabotropic glutamate receptors.

Our molecular studies have revealed the existence of a large number of different subunits or subtypes for the NMDA and metabotropic glutamate receptors. The individual receptors show functional variabilities and distinct expression patterns in the CNS. The NMDA receptors belong to the ligand-gated ion channel family and consist of a key subunit NMDAR1 and four accessory subunits NMDAR2A-NMDAR2D. The combination of NMDAR1 and NMDAR2 in heteromeric configurations potentiates glutamate response and produces a functional variability. All the NMDAR subunits have an asparagine residue at the corresponding position of the second transmembrane segments, and these residues are thought to be responsible for controlling Ca2+ permeation and the channel blockade by Mg2+ and cationic channel blockers. Individual NMDAR subunit mRNAs are different in their expression patterns during development and in the adult brain. The mGluR family consists of at least six different subtypes. These subtypes are divided into three subgroups according to their sequence similarities, signal transduction mechanisms, and pharmacological properties. Although their physiological roles largely remain to be elucidated, the retinal L-AP4-sensitive mGluR may have a specific function that mediates excitatory neurotransmission in the visual system. It is thus undoubtedly important to investigate specific functions of different combinations of the NMDA receptor subunits and different subtypes of mGluRs and to explore the molecular mechanisms of glutamate receptor-mediated neuronal plasticity and neurotoxicity.

Animals↗
PubMed1993

Molecular characterization of a novel retinal metabotropic glutamate receptor mGluR6 with a high agonist selectivity for L-2-amino-4-phosphonobutyrate.

A cDNA clone for a new metabotropic glutamate receptor, termed mGluR6, was isolated from a rat retinal cDNA library by cross-hybridization with the previously isolated cDNA clone for a metabotropic glutamate receptor. The cloned mGluR6 subtype consists of 871 amino acid residues and exhibits a structural architecture common to the metabotropic receptor family, possessing a large extracellular domain preceding the seven putative membrane-spanning domains. mGluR6 shows the highest sequence similarity to mGluR4 among the metabotropic receptor subtypes and inhibits the forskolin-stimulated cyclic AMP accumulation in Chinese hamster ovary cells transfected with the cloned cDNA. mGluR6 potently reacts with L-2-amino-4-phosphonobutyrate (L-AP4) and L-serine-O-phosphate, and the potencies of these compounds are one order of magnitude greater than that of L-glutamate. Blot and in situ hybridization analyses indicated that mGluR6 mRNA is restrictedly expressed in the inner nuclear layer of the retina where ON-bipolar cells are distributed. The metabotropic receptor that responds strongly to L-AP4 and L-serine-O-phosphate in ON-bipolar cells is known to mediate glutamate synaptic transmission between photoreceptor cells and ON-bipolar cells. On the basis of the agonist selectivity of mGluR6 and its specific expression in retinal cells, the physiological role of this receptor subtype in the visual system is discussed.

Amino Acid Sequence↗
PubMed1993

Molecular characterization of the family of the N-methyl-D-aspartate receptor subunits.

cDNA clones for four different N-methyl-D-aspartate (NMDA) receptor subunits (NMDAR2A-NMDAR2D) were isolated through polymerase chain reactions followed by molecular screening of a rat brain cDNA library. These subunits are only about 15% identical with the key subunit of the NMDA receptor (NMDAR1) but are highly homologous (approximately 50% homology) with one another. They also commonly possess large hydrophilic domains at both amino- and carboxyl-terminal sides of the four putative transmembrane segments. NMDAR2A and NMDAR2C expressed individually in Xenopus oocytes showed no electrophysiological response to agonists. However, these subunits in combined expression with NMDAR1 markedly potentiated the NMDAR1 activity and produced functional variability in the affinity of agonists, the effectiveness of antagonists, and the sensitivity to Mg2+ blockade. Thus, NMDAR1 is essential for the function of the NMDA receptor, and multiple NMDAR2 subunits potentiate and differentiate the function of the NMDA receptor by forming different heteromeric configurations with NMDAR1. Northern blotting and in situ hybridization analyses revealed that the expressions of individual mRNAs for the NMDAR2 subunits overlap in some brain regions but are also specialized in many other regions. This investigation demonstrates the anatomical and functional differences of the NMDAR2 subunits, which provide the molecular basis for the functional diversity of the NMDA receptor.

Amino Acid Sequence↗
PubMed1992

Molecular characterization of a rat negative regulator with a basic helix-loop-helix structure predominantly expressed in the developing nervous system.

We report here the cDNA cloning and characterization of a rat basic helix-loop-helix (HLH) factor, designated HES-5. This factor has a distant sequence homology to Drosophila hairy and Enhancer-of-split proteins, both of which are required for normal neurogenesis. DNase I footprinting analyses show that HES-5 binds to the sequence CACNAG (called N box), a recognition sequence of Enhancer-of-split proteins. Although HES-5 does not bind to the sequence CANNTG (called E box) recognized by other HLH factors, it attenuates the binding of E47, an HLH activator, to E box by forming a hetero-oligomer. In cotransfection analyses using NIH 3T3 cells, HES-5 significantly represses transcription originating from the promoter containing the N box sequences. Furthermore, HES-5 also partially inhibits the E47-induced expression from the promoter containing E boxes. Northern blot, RNase protection, and in situ hybridization analyses demonstrate that the HES-5 mRNA is specifically expressed in the nervous system. Prominent expression is observed in the ventricular zones of the embryonal brain vesicles and the outer nuclear layer of the neural retina. These results suggest that the negative regulator HES-5 may play an important role in neural development.

3T3 Cells↗
PubMed1992

Delineation of structural domains involved in the subtype specificity of tachykinin receptors through chimeric formation of substance P/substance K receptors.

The mammalian tachykinin receptors belong to the family of G protein-coupled receptors and consist of the substance P, substance K and neuromedin K receptors (SPR, SKR and NKR). We constructed 14 chimeric receptors in which seven transmembrane segments were sequentially exchanged between the rat SPR and SKR and examined the subtype specificity of the chimeric receptors by radioligand binding and inositol phosphate measurements after transfection into COS cells. All chimeric receptors showed maximum responses in agonist-induced inositol phosphate stimulation. Detailed analysis of five receptors with agonist selectivity similar to SPR indicated that the selectivity is mainly determined by the region extending from transmembrane segment II to the second extracellular loop together with a minor contribution of the extracellular N-terminal portion. This conclusion was more directly confirmed by an additional chimeric formation in which the introduction of the above middle portion of SPR into the corresponding region of SKR conferred a high affinity binding to substance P. The tachykinin receptors can thus be divided into two functional domains: the region covering transmembrane segments V-VII and responsible for fundamental recognition of the common tachykinin sequence; and its preceding portion involved in evoking subtype specificity by interacting with the divergent sequences of the peptides.

Animals↗
PubMed1989

Treatment of the scalp using photon and electron beams.

Many problems arise when treating superficial malignancies along the entire scalp. Some techniques will irradiate too much of the underlying brain while others are highly complex and may involve field junction problems. One approach to circumvent such difficulties is to use lateral opposed photon fields and adjoining electron fields as described in this paper. Sufficient dose coverage throughout the entire scalp is achieved, the normal brain tissues receives minimal dosages, the complexities of simulation and treatment are greatly eased, and the ambiguities of doses at field junction regions are diminished.

Electrons↗