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K Nakadate

Publications and source records attributed to K Nakadate.

18 recordsLinked to original sources
PubMed2006

Cellular and subcellular localization of alpha-1 adrenoceptors in the rat visual cortex.

Noradrenaline is thought to play modulatory roles in a number of physiological, behavioral, and cellular processes. Although many of these modulatory effects are mediated through alpha-1 adrenoceptors, basic knowledge of the cellular and subcellular distributions of these receptors is limited. We investigated the laminar distribution pattern of alpha-1 adrenoceptors in rat visual cortex, using immunohistochemistry at both light and electron microscopic levels. Affinity-purified anti-alpha-1 antibody was confirmed to react only with a single band of about 70-80 kDa in total proteins prepared from rat visual cortex. Alpha-1 adrenoceptors were widely distributed though all cortical layers, but relatively high in density in layers I, II/III, and V. Immunoreactivity was observed in both neuronal perikarya and processes including apical dendrites. In double-labeling experiments with anti-microtubule-associated protein 2, anti-neurofilament, anti-glial fibrillary acidic protein, anti-glutamic acid decarboxylase 65/67, anti-2-3-cyclic nucleotide 3-phosphodiesterase, and anti-tyrosine hydroxylase antibodies, alpha-1 adrenoceptors were found mainly in dendrites and somata of microtubule-associated protein 2-immunopositive neurons. About 20% of alpha-1 adrenoceptors were in GABAergic neurons. A small number of alpha-1 adrenoceptors were also distributed in axons of excitatory neurons, astrocytes, oligodendrocytes and noradrenergic fibers. Using an immunoelectron microscopic technique, numerous regions of alpha-1 adrenoceptor immunoreactivity were found in cell somata, on membranes of dendrites, and in postsynaptic regions. Moreover, a small number of immunoreaction products were also detected in axons and presynaptic sites. These findings provide the first quantitative evidence regarding the cellular and subcellular localization of alpha-1 adrenoceptor immunoreactivity in visual cortex. Moreover, the ultrastructural distribution of alpha-1 adrenoceptor immunoreactivity suggests that alpha-1 adrenoceptors are transported mainly into dendrites and that they exert effects at postsynaptic sites of neurons.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed2005

Identification of adrenoceptor subtype-mediated changes in the density of synapses in the rat visual cortex.

Both serotonin and noradrenaline affect synapse formation and maintenance in the CNS. Although we previously demonstrated that serotonin regulates synaptic density via activation of serotonin(2A) receptor, it was still unclear which receptor subtype mediates the function of noradrenaline. In the present study we tried to identify the noradrenaline receptor (adrenoceptor) subtype, which could regulate the density of synapses in the rat visual cortex. Selective antagonists and/or agonists of adrenoceptor subtypes were administered to six weeks old rats. Changes in the density of axodendritic synapses were quantitatively examined in lamina I, where noradrenaline rather than serotonin is known to regulate the density of synapses. The alpha1 adrenoceptor antagonists (prazosin and 2-{[b-(4-hydroxyphenyl)ethyl]aminomethyl}-1-tetralone) decreased the number of synapses in a dose-dependent manner. In contrast, administrations of the alpha1-agonist (methoxamine) increased the density of synapses. The beta1 adrenoceptor antagonist (atenolol) had no effect on the density of synapses. The alpha2-antagonist (rauwolscine) increased synaptic density, whereas the beta2-antagonist (ICI-118,551) decreased synaptic density. Simultaneous treatments with the alpha1-antagonist and alpha1-agonist caused the alpha1-agonist to competitively block the effect of the alpha1-antagonist and recover the density of synapses to the control values. In addition, the alpha1-antagonist/agonist appeared to show a reverse effect on the changes in synaptic density following alpha2- or beta2-antagonist treatment by acting via the alpha1 receptor. Moreover, decreased synaptic density when a selective noradrenergic neurotoxin (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine) was counterbalanced by the alpha1-agonist. These data suggest that noradrenaline regulates the density of synapses in the rat visual cortex primarily via the alpha1 receptor subtype. Both serotonin(2A) and alpha1 receptors are known to couple with phospholipase C, which has been shown to increase intracellular calcium. It may help us to understand the underlying mechanisms for synaptic plasticity in the CNS.

Adrenergic alpha-Agonists↗
PubMed2003

Synaptic loss following depletion of noradrenaline and/or serotonin in the rat visual cortex: a quantitative electron microscopic study.

Biogenic amines have a trophic-like role for the formation and the maintenance of synapses in the CNS. We examined the changes in the number of synaptic profiles in the developing and adult rat visual cortex following selective depletion of noradrenaline and/or serotonin. By the drug-induced decreases in levels of noradrenaline or serotonin between 1 and 2 weeks after birth, the number of synaptic profiles was decreased by 29-55% compared with that of control animals. The magnitude of reduction in the number of synaptic profiles was virtually the same following simultaneous depletion of both noradrenaline and serotonin compared with the depletion of noradrenaline or serotonin alone. Later in the developmental period, the function of noradrenaline and serotonin in facilitating synapse formation and maintenance became less prominent than that in younger animals. In the control animals, the number of axosomatic synapses was the highest at around 2 weeks after birth, and decreased with development. The number of axodendritic synapses was the highest between 2 and 7 weeks after birth, and decreased to 50% at 11 weeks after birth. These data demonstrate that synapses in the rat visual cortex are overproduced during the early developmental period. We suggest that both serotonin and noradrenaline are necessary for synapse formation during the early stages of development of the rat visual cortex.

Aging↗
PubMed2001

Effects of monocular deprivation on the expression pattern of alpha-1 and beta-1 adrenergic receptors in the kitten visual cortex.

To examine how adrenergic receptors are regulated by experimental manipulation of sensory afferents, we performed immunohistochemical analysis on alpha1-, and beta1-adrenergic receptors in the brain of kittens. In normal development, these receptors were similarly expressed in both hemispheres of the occipital and frontal cortices. Notably, monocular deprivation during the sensitive period of ocular dominance plasticity significantly increased beta1-adrenergic receptor immunoreactivity in the visual cortex ipsilateral to the deprived eye. No increase in the intensity of the immunoreactivity for beta1-adrenergic receptors following monocular deprivation was found in the frontal and parietal regions of the cerebral cortex and subcortical structures, including the lateral geniculate nucleus and superior colliculus. Furthermore, such hemispheric change was not found in the alpha1-adrenergic receptor immunoreactivity following monocular deprivation. Comparisons of images, obtained by double staining for microtubule-associated protein-2 or glial fibrillary acidic protein, indicated that the increased immunoreactivity was localized on both apical dendrites of deep layer neurons and glial cells. These results indicate that the monocular deprivation during the sensitive period of ocular dominance plasticity modified beta1-adrenergic receptor immunoreactivity, including that in glial cells. Therefore, it was suggested that beta1-adrenergic receptors in the glial cells also play important roles in the regulation of ocular dominance plasticity.

Age Factors↗
PubMed2001

N-(2-Chloroethyl)-N-ethyl-2-bromobenzylamine reduces intracellular calcium response to noradrenaline in rat visual cortex.

Using the fluorescent indicator Fura-2, we investigated the effects of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4), a noradrenergic neurotoxin, on intracellular calcium responses to noradrenaline, N-methyl-D-aspartate, and carbamylcholine chloride in brain slices of the rat visual cortex. Noradrenergic depletion in the visual cortex of young rats was induced by DSP-4, and its selectivity was confirmed by two different methods, i.e., immunostaining with anti-dopamine-beta-hydroxylase antibody and biochemical analysis by high-performance liquid chromatography. The treatment with DSP-4 (25 mg/kg i.p., x2) caused disruption of noradrenergic fibers throughout all cortical layers, and reduced the content of noradrenaline to 6.4% of that in the normal control. In the normal cortex, bath-applied noradrenaline (100 microM) increased the intracellular calcium to 123% of the control in terms of the F(340)/F(380) ratio of Fura-2 fluorescence. Quantitative analysis of the F(340)/F(380) ratio was performed in layers II to IV, since the increase was mainly observed in these layers. The intracellular calcium response to noradrenaline was significantly (P<0.0001) reduced in the DSP-4-treated animals to 63.2% of that in the normal control. The response to N-methyl-D-aspartate (100 microM) was also reduced, whereas the response to carbamylcholine chloride, a muscarinic cholinergic agonist (100 microM), was not affected by the DSP-4 treatment. From these findings we suggest that noradrenergic denervation by DSP-4 reduces the intracellular calcium response to noradrenaline through changes in the intracellular signal transduction.

Adrenergic Agents↗
PubMed2001

VCP/p97 in abnormal protein aggregates, cytoplasmic vacuoles, and cell death, phenotypes relevant to neurodegeneration.

Neuronal cell death, abnormal protein aggregates, and cytoplasmic vacuolization are major pathologies observed in many neurodegenerative disorders such as the polyglutamine (polyQ) diseases, prion disease, Alzheimer disease, and the Lewy body diseases, suggesting common mechanisms underlying neurodegeneration. Here, we have identified VCP/p97, a member of the AAA+ family of ATPase proteins, as a polyQ-interacting protein in vitro and in vivo, and report on its characterization. Endogenous VCP co-localized with expanded polyQ (ex-polyQ) aggregates in cultured cells expressing ex-polyQ, with nuclear inclusions in Huntington disease patient brains, and with Lewy bodies in patient samples. Moreover, the expression of VCP mutants with mutations in the 2nd ATP binding domain created cytoplasmic vacuoles, followed by cell death. Very similar vacuoles were also induced by ex-polyQ expression or proteasome inhibitor treatment. These results suggest that VCP functions not only as a recognition factor for abnormally folded proteins but also as a pathological effector for several neurodegenerative phenotypes. VCP may thus be an ideal molecular target for the treatment of neurodegenerative disorders.

Adenosine Triphosphatases↗
PubMed2001

Visual stimulation-induced phosphorylation of neurofilament-L in the visual cortex of dark-reared rats.

In dark-reared animals, visual exposure is expected to induce drastic changes in both the physiology and anatomy of the cortical neurons, including the rearrangement of their cytoskeletal structures. Phosphorylation of neurofilament-L (NF-L) is probably associated with relatively short-term structural plasticity in vivo, because the assembly and disassembly of the filaments are regulated by phosphorylation of the head domain of NF-L. Thus, by using a series of site- and phosphorylation state-specific antibodies against NF-L, we examined how visual activation induces the phosphorylation of NF-L in the rat brain. We found no specific immunoreactivity for phosphorylated NF-L in the brain of naive rats, whereas one-hour ambient light exposure after dark rearing for ten weeks from birth induced marked phosphorylation of NF-L selectively. Also, the NF-L phosphorylation was found to be localized in the primary and secondary visual cortical areas. These findings suggest that the selective phosphorylation of NF-L plays an important role in the structural plasticity related to the visual experience.

Amino Acid Sequence↗
PubMed1999

Developmental regulation of intracellular calcium by N-methyl-D-aspartate and noradrenaline in rat visual cortex.

The effects of N-methyl-D-aspartate and noradrenaline on intracellular Ca2+ concentration in slices of rat visual cortex were studied using a fluorescent indicator, Fura-2. Bath application of N-methyl-D-aspartate (1-100 microM) increased intracellular Ca2+ concentration in a dose-dependent manner, especially in layers II/III. Noradrenaline (1-100 microM) also increased intracellular Ca2+ concentration in a dose-dependent manner, especially in layers I and IV. However, the maximum increase in intracellular Ca2+ concentration after 100 microM noradrenaline application was less than half of that after 100 microM N-methyl-D-aspartate application in slices obtained from animals in the sensitive period. The effect of noradrenaline was most prominent in slices of the sensitive period, whereas the N-methyl-D-aspartate-induced intracellular Ca2+ concentration response decreased with age. Additive effects from application of both N-methyl-D-aspartate and noradrenaline on intracellular Ca2+ concentration were found only in the neonatal stage. Pharmacological experiments showed that alpha1-adrenergic receptors play a major role in the noradrenaline-induced intracellular Ca2+ concentration response, although both alpha2- and beta-adrenergic receptors were also partially involved. The release of Ca2+ from intracellular storage underlay the early phase of the noradrenaline-induced intracellular Ca2+ concentration response, while extracellular Ca2+ influxes contributed to the sustained phase. Experiments using a gliotoxin, fluorocitric acid, suggested that the function of glial cells is involved in the noradrenaline-induced increase of intracellular Ca2+ concentration. The larger intracellular Ca2+ concentration response to noradrenaline during the sensitive period may modulate the increase in intracellular Ca2+ concentration by N-methyl-D-aspartate to maintain a higher level of cortical plasticity during this period.

Adrenergic alpha-Agonists↗
PubMed1999

CNS-specific prostacyclin ligands as neuronal survival-promoting factors in the brain.

Prostacyclin (PGI2) is a critical regulator of the cardiovascular system, via dilatation of vascular smooth muscle and inhibition of platelet aggregation (Moncada, S. 1982, Br. J. Pharmacol., 76, 3). Our previous studies demonstrated that a novel subtype of PGI2 receptor, which is clearly distinct from a peripheral subtype in terms of ligand specificity, is expressed in the rostral region of the brain, e.g. cerebral cortex, hippocampus, thalamus and striatum, and that (15R)-16-m-17,18,19,20-tetranorisocarbacyclin (15R-TIC) and 15-deoxy-16-m-17,18,19,20-tetranorisocarbacyclin (15-deoxy-TIC) specifically bind to the central nervous system (CNS)-specific PGI2 receptor. Here, we report that these CNS-specific PGI2 receptor ligands, including PGI2 itself, prevented the neuronal death. They prevented apoptotic cell death of hippocampal neurons induced by high (50%) oxygen atmosphere, xanthine + xanthine oxidase, and serum deprivation. IC50s for neuronal death were approximately 30 and 300 nM for 15-deoxy-TIC and 15R-TIC, respectively, which well correlated with the binding potency for the CNS-specific PGI2 receptor. 6-Keto-PGF1alpha (a stable metabolite of PGI2), peripheral nervous system-specific PGI2 ligands and other prostaglandins (PGs) than PGI2 did not show such neuroprotective effects. In vivo, 15R-TIC protected CA1 pyramidal neurons against ischaemic damage in gerbils. These results indicate that CNS-specific PGI2 ligands have neuronal survival-promoting activity both in vitro and in vivo, and may represent a new type of therapeutic drug for neurodegeneration.

Animals↗
PubMed1998

Brain endothelial cells express cyclooxygenase-2 during lipopolysaccharide-induced fever: light and electron microscopic immunocytochemical studies.

Cyclooxygenase-2 (COX-2), a key enzyme in the biosynthesis of prostaglandins, is induced in brain blood vessels by pyrogens, and its essential role in fever has been hypothesized. In this study, we determined (1) the type of cells that express cyclooxygenase-2 in brain blood vessels of lipopolysaccharide-treated rats, and (2) the precise relationship between the time course of fever and that of cyclooxygenase-2 protein expression in these cells. Five hours after the lipopolysaccharide injection (100 microg/kg, i.p.), cyclooxygenase-2-like immunoreactive cells were found in the parenchymal and subarachnoidal blood vessels. In these blood vessels, the cyclooxygenase-2-like immunoreactivity was restricted to the perinuclear region of the endothelial cells as revealed by a laser confocal microscopy, double-immunofluorescence staining with an endothelial marker, and immunoelectron microscopy. On the other hand, the cyclooxygenase-2-like immunoreactive cells were distinct from microglia or perivascular/meningeal macrophages as revealed by double immunostaining with macrophage/microglia-specific antibodies. Cyclooxygenase-2-like immunoreactive cells were first found at 1.5 hr after the lipopolysaccharide injection, at which time the fever had not been developed. After that, the number of cyclooxygenase-2-like immunoreactive cells and fever followed a similar time course, both being highest at 5 hr after the lipopolysaccharide injection and both returning to the baseline by 24 hr. These results demonstrate that brain endothelial cells are the primary sites where the activation of arachidonic acid cascade takes place during fever after intraperitoneal injection of lipopolysaccharide.

Animals↗
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↗
PubMed1993

[Trace metal elements in gallstones and their roles].

The concentrations of metal elements in gallstones were measured by absorption spectrometry. Crystallographic analysis by the powder X-ray diffraction method was also performed. For all stones calcium was the major component. In calcium carbonate stones aragonite form, one of the CaCO3 polymorphs and usually unstable in nature, was dominant. As a whole, black-stones contained highest proportions of all metal elements. But these stones were crystallographically grouped into three types; they are calcium carbonate-, calcium phosphate-, and other-one. In each type, the concentration of metal element differed greatly. It is suggested that in black-stones the amount of Mn is remarkable and Cu is highly correlated to black residue. It was true, but Mn was remarkable especially in calcium phosphate-type and Cu was the highest in other-type.

Bilirubin↗
PubMed1986

Chemical and crystallographic studies on 33 cases of calcium carbonate gallstone (so-called limy bile).

Chemical analyses by atomic absorption spectrophotometry and crystallographic studies by the X-ray powder diffraction method and infrared spectrometry (KBr-disk method) were made on 33 cases of calcium carbonate gallstone or so-called limy bile. Chemically, calcium carbonate was the major constituent, ranged from 33.7 to 91.6% and averaged 77.8%. Crystallographically, calcium carbonate has three different polymorphic crystalline forms; calcite, aragonite and vaterite. In nature the most stable calcite (hexagonal) is most commonly found and aragonite (rhombic) is next. On the other hand vaterite, which is unstable hexagonal modification, rarely occurs in biological systems. But in our gallstone series in man, aragonite was most commonly found, with an occurrence rate of 90.6%, while that of calcite was 62.5%. Even vaterite was found in 28.1%. Moreover three cases contained all three forms of calcium carbonate polymorphs; calcite, aragonite and vaterite. This was a very unusual condition. Some environmental factors controlling the growth of these crystals, such as specificity of the bile, are suggested.

Calcium Carbonate↗
PubMed1979

Review of five cases of limy bile--particularly on radiological, chemical and crystallographic studies--.

Incidence of "limy bile" is relatively rare and only 120 cases have been recorded in Japan so far. The present report is to add five more cases operated on at our clinic. On chemical analysis by atomic absorption spectrophotometry calcium carbonate was the major constituent of solid portion and ranged from 73.5 to 88.5%. On crystallographic analyses, the infrared spectra by means of KBr-disk method gave patterns of calcium carbonate in all cases, and the X-ray powder diffraction studies disclosed those of aragonite only in cases 2 and 4, and aragonite-calcite mixture in cases 1 and 3. The exact etiology of formation of limy bile in the gallbladder has not yet been understood completely.

Adult↗