Biomedical subjects

N Mizuno

Publications and source records attributed to N Mizuno.

At least 55 records · Page 3Linked to original sources

PubMed2000

The relationship between neurokinin-1 receptor and substance P in the medullary dorsal horn: a light and electron microscopic immunohistochemical study in the rat.

The synaptic relationship between substance P (SP) and its receptor, i.e. neurokinin-1 receptor (NK1R), was examined in the superficial laminae of the caudal subnucleus of the spinal trigeminal nucleus (medullary dorsal horn; MDH) of the rat. For confocal laser-scanning microscopy, double-immunofluorescence histochemistry for NK1 and SP was performed. In electron microscopic double-immunolabeling study, immunoreactivity for NK1R was detected with the silver-intensified gold method, while immunoreactivity for SP was detected with peroxidase immunohistochemistry. SP-immunoreactive axon terminals were observed to be in synaptic (mostly asymmetric) contact with NK1R-immunoreactive neuronal profiles in lamina I and lamina IIo. Although some SP-immunoreactive axon terminals were in synaptic contact with NK1R-immunoreactive sites of plasma membranes, NK1R-immunoreactivity was observed at both synaptic and non-synaptic sites of plasma membrane. Thus, SP released from axon terminals might not only act on NK1Rs facing the SP-containing axon terminals, but also diffuse in the extracellular fluid for distances larger than the synaptic cleft to act on NK1Rs at some distances from the synaptic sites.

Animals↗

PubMed2000

Serotonergic innervation of mesencephalic trigeminal nucleus neurons: a light and electron microscopic study in the rat.

Neurons of the mesencephalic trigeminal nucleus (MTN) are considered to be homologous to mechanosensitive neurons in the sensory ganglia. The sites of origin of serotonin (5HT)-immunoreactive axons on neuronal cell bodies in the MTN were studied in the rat by combining immunofluorescence histochemical techniques with retrograde tracing of Fluoro-Gold (FG) and anterograde tracing of biotin-conjugated dextran amine (BDA). The tracing studies, which were combined with multiple-labeling immunohistochemistry and confocal microscopy, indicated that 5HT-immunoreactive axon terminals on the cell bodies of MTN neurons originated from the medullary raphe nuclei, such as the nucleus raphes magmus (RMg), alpha part of the nucleus reticularis gigantocellularis (GiA) and nucleus raphes obscurus (ROb), as well as from the mesopontine raphe nuclei, such as the nucleus raphes dorsalis (DR), nucleus raphes pontis (PnR) and nucleus raphes medianus (MnR); mainly from the RMg, GiA and DR, and additionally from the ROb, PnR and MnR. The cell bodies in close apposition to 5HT-immunoreactive axon terminals were found through the whole rostrocaudal extent of the MTN. Electron microscopically a number of axon terminals that were labeled with BDA injected into the raphe nuclei were confirmed to be in asymmetric synaptic contact with the cell bodies of MTN neurons. It was also indicated that substance P existed in some of the 5HT-containing axosomatic terminals arising from the ROb, RMg and GiA. The present results indicated that proprioceptive sensory signals from the muscle spindles or periodontal ligament might be modulated at the level of the primary afferent cell bodies in the MTN by 5HT-containing axons from the mesopontine and medullary raphe nuclei including the GiA.

Animals↗

PubMed2000

Intrinsic and commissural connections within the entorhinal cortex. An anterograde and retrograde tract-tracing study in the cat.

Intrinsic and commissural connections within the entorhinal cortex (EC) were examined in the cat by the anterograde and retrograde tract-tracing methods with Phaseolus vulgaris leucoagglutinin and cholera toxin B subunit. Intrinsic axons to the superficial layers (layers I-III) arose mainly from layers II, III, Vd (deep part of layer V), and VI, were distributed more widely in the superficial layers than in the deep layers, and terminated progressively more densely in more superficial layers; most densely in layer I. In the medial entorhinal area (MEA) and the ventromedial and the ventrolateral divisions of the lateral entorhinal area (VMEA and VLEA), the longitudinal connections through the intrinsic fibers to the superficial layers is often more restricted in rostral direction than in caudal direction. In the dorsolateral division of the lateral EC (DLEA), the longitudinal connections through the intrinsic fibers to the superficial layers extended distantly in both rostral and caudal directions. Intrinsic fibers to the deep layers (layers IV-VI) originated mainly from layers IV and Vs (superficial part of layer V) and were distributed rather sparsely and diffusely; they were distributed more widely in the deep layers than in the superficial layers. Commissural axons to the homotopic EC regions originated from layers II and III of the MEA and DLEA and terminated in all EC layers, most densely in layer I.

Animals↗

PubMed2000

A group of cortical interneurons expressing mu-opioid receptor-like immunoreactivity: a double immunofluorescence study in the rat cerebral cortex.

mu-Opioid receptor-expressing neurons in the rat cerebral neocortex were characterized by an immunolabeling method with an antibody to a carboxyl terminal portion of the receptor. They were small, bipolar, vertically elongated, non-pyramidal neurons, and scattered mainly in layers II-IV. We examined chemical characteristics of mu-opioid receptor-expressing neocortical neurons by the double immunofluorescence method. Almost all neuronal cell bodies expressing mu-opioid receptor-like immunoreactivity showed immunoreactivity for GABA, suggesting that they were cortical inhibitory interneurons. mu-Opioid receptor-immunoreactive neurons were further studied by the double staining method with markers for the subgroups of cortical GABAergic neurons. Immunoreactivities for vasoactive intestinal polypeptide, corticotropin releasing factor, choline acetyltransferase, calretinin and cholecystokinin were found in 92, 79, 67, 35 and 35% of mu-opioid receptor-immunoreactive cortical neurons, respectively. In contrast, less than 10% of mu-opioid receptor-immunoreactive neurons showed immunoreactivity for parvalbumin, calbindin, somatostatin, neuropeptide Y or nitric oxide synthase. Moreover, mu-opioid receptor-immunoreactive neurons very frequently exhibited preproenkephalin immunoreactivity, but not preprodynorphin immunoreactivity. The present results indicate that mu-opioid receptor-expressing neurons belong to a distinct subgroup of neocortical GABAergic neurons, because vasoactive intestinal polypeptide, corticotropin releasing factor, choline acetyltransferase, calretinin and cholecystokinin have often been reported to coexist with one another in single neocortical neurons. Methionine-enkephalin, which is a major product of the preproenkephalin gene, is known to be one of the most potent endogenous ligands for mu-opioid receptor. Thus, the expression of mu-opioid receptor in preproenkephalin-producing neurons suggested that mu-opioid receptor serves as an autoreceptor for the subpopulation of GABAergic interneurons at a single-neuron or population level.

Animals↗

PubMed2000

Sustained release of diclofenac from polymer-containing suppository and the mechanism involved.

Sustained release of diclofenac sodium (DcNa) from suppositories composed of triglycerides and polymer was investigated by dissolution testing through an artificial membrane. DcNa was slowly released from a suppository containing carboxyvinyl polymer (CVP), and the extent of the release decreased with the amount of CVP added. Little effect was noted with the addition of other water-soluble polymers, such as hydroxyethylcellulose (HEC), xanthan gum, and polyvinylalcohol (PVA). When sodium benzoate was used instead of DcNa, a similar result was obtained with the addition of CVP. The result of release rate analysis together with the viscosity and pH in these cases showed that the reduction of solubility and diffusion due to sodium exchange between DcNa and CVP played an important role in the sustained release from the suppository. Also, in comparison with the results when CVP was not used, the plasma concentration profile of diclofenac after the administration of CVP suppository displayed a twofold longer half-life time.

Animals↗

PubMed2000

Effects of phospholipase A2 inhibitors on Ca2+ oscillations in pancreatic acinar cells.

High-affinity cholecystokinin (CCK) receptors were reported to be coupled with phospholipase A2 (PLA2)-arachidonic acid (AA) pathways to mediate Ca2+ oscillations and amylase secretion in rat pancreatic acinar cells. To investigate which types of PLA2 were involved in PLA2-AA pathways, the effects of specific inhibitors for type II and type IV PLA2 on Ca2+ oscillations and amylase secretion were studied in isolated rat pancreatic acini. An inhibitor of type IV (cytosolic) PLA2, AACOCF3 inhibited Ca2+ oscillations elicited by CCK-8 (30 pM) and JMV-180 (100 nM). AACOCF3 inhibited amylase secretion stimulated by JMV-180 and low concentrations of CCK-8 (< or =30 pM). On the other hand, an inhibitor of type II (secretory, nonpancreatic) PLA2 had no effects on Ca2+ oscillations and amylase secretion stimulated by CCK-8 and JMV-180. These results suggest that high-affinity CCK receptors are coupled to cytosolic PLA2 to mediate Ca2+ oscillations and amylase secretion in rat pancreatic acinar cells.

Amylases↗

PubMed2000

Preliminary X-ray crystallographic study of DsrD protein from the sulfate-reducing bacterium Desulfovibrio vulgaris.

DsrD (dissimilatory sulfite reductase D) protein encoded by the dsr operon of the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough has been crystallized using the vapour-diffusion method with ammonium sulfate as a precipitating agent. The crystals diffract to 1.7 A resolution and belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 60.54 (6), b = 65. 20 (4), c = 46.41 (3) A. The crystal contains two DsrD molecules per asymmetric unit, giving a Matthews coefficient (V(M)) of 2.6 A(3) Da(-1). A gold-derivative (NaAuCl(4)) crystal has been successfully prepared.

Crystallization↗

PubMed1999

Calcium-binding protein-immunoreactive projection neurons in the caudal subnucleus of the spinal trigeminal nucleus of the rat.

It has been reported that calcium-binding proteins are good markers for different sets of neurons in various brain regions. We examined expression of the main calcium-binding proteins in projection neurons in the rat medullary dorsal horn (MDH) by combining immunofluorescence histochemistry for calbindin D28k (CB), calretinin (CR) and parvalbumin (PV) with the retrograde tract-tracing method. A fluorescence tracer, tetramethylrhodamine-dextran amine (TMR-DA), was injected into the parabrachial, thalamic or hypothalamic region. After such injections, a number of PV-, CR-, and/or CB-immunoreactive MDH neurons were labeled retrogradely with TMR-DA. Triple-immunofluorescence histochemistry further revealed that a number of CB-, CR-, or PV-immunoreactive TMR-DA-labeled MDH neurons showed immunoreactivity for substance P receptor (NK1), and that they expressed immunoreactivity for c-fos protein in the rats which were injected with formalin into the lips. Thus, it was indicated that some of CB-, CR-, or PV-containing projection neurons in the MDH might be involved in the transmission of nociceptive stimuli.

Animals↗

PubMed1999

Local circuit neurons showing calbindin D28k-immunoreactivity in the substantia gelatinosa of the medullary dorsal horn of the rat. An immunohistochemical study combined with intracellular staining in slice preparation.

Calbindin D28k (CB)-immunoreactive local circuit neurons in the substantia gelatinosa of the rat medullary dorsal horn were studied in slice preparations; intracellular injection of biocytin was followed by histochemical visualization of biocytin, then CB immunohistochemistry was performed. In six neurons so far examined, overall morphology, including those of dendritic fields, axonal fields, and arborization patterns, was common.

Animals↗

PubMed1999

Substantia gelatinosa neurons in the medullary dorsal horn: An intracellular labeling study in the rat.

Morphologic features and electrical membrane properties of neurons in the substantia gelatinosa (SG) of the caudal spinal trigeminal nucleus (the medullary dorsal horn; MDH) were examined in the rat. Intracellular recording and biocytin-injection combined with histochemical staining were performed in horizontal slices. Twenty-four SG (lamina II) neurons were recorded stably and stained successfully. Both projection neurons (PNs; n = 9) that sent axons to regions outside the MDH and intrinsic neurons (INs; n = 15) that sent axons only to the MDH were observed. The INs were divided into those with dense axonal arborization (INDAs; n = 7) and those with sparse axonal arborization (INSAs; n = 8). In the PNs, the dendrites with spines spread to all MDH layers (laminae I-III). The main axons sent collaterals within the SG and rostrally, caudally, or medially to laminae I and III of the MDH, interpolar spinal trigeminal nucleus, spinal tract of the trigeminal nerve, or upper cervical cord segments. In the INDAs, the dendrites arising from the rostral and caudal pole of the cell bodies mainly extended rostrally and caudally parallel to the rostrocaudal axis of the SG: the dendritic trees were elongated and oval in shape and were confined within the SG. The axonal field of each INDA, a dense mesh of axonal processes, was elongated and oval in shape and almost was confined within the SG. In the INSAs, a small, round cell body was located in the center of each dendritic field, which usually was limited within the SG. Axonal processes ran radially to spread to all layers of the MDH, constituting round or oval axonal fields. The three groups of SG neurons showed more or less different intracellular responses to current injections. In particular, adaptation of spike frequency, hyperpolarizing sag, and rebound excitation were observed in the PNs and INSAs but not in the INDAs. Slow ramp depolarization and slow afterdepolarization were recorded only in INDAs.

Action Potentials↗

PubMed1999

The distribution of substance P receptor (NK1)-like immunoreactive neurons in the newborn and adult human spinal cord.

Substance P receptor (i.e. NK1)-like immunoreactive (SPR-LI) neurons were observed in the newborn and adult human spinal cord. Substance P receptor-like immunoreactive neuronal cell bodies were seen most frequently in lamina I, and were scattered throughout the remaining laminae of the dorsal horn and the area around the central canal. Some neurons in the intermediolateral nucleus also showed weak immunoreactivity. The pattern of distribution of SPR-LI neurons in the adult spinal cord was essentially the same as that in the newborn spinal cord. However, SPR-LI neurons cell bodies were seen much more frequently in the newborn than in the adult dorsal horn, especially in lamina II.

Adult↗

PubMed1999

Preprodynorphin-like immunoreactivity in medullary dorsal horn neurons projecting to the thalamic regions in the rat.

Preprodynorphin (PPD)-like immunoreactive (-LI) neuronal cell bodies in the trigeminal sensory nuclear complex of the rat were found in laminae I and II of the medullary dorsal horn (MDH; caudal spinal trigeminal nucleus) and the paratrigeminal nucleus. A PPD immunofluorescence histochemistry combined with a fluorescence retrograde tract-tracing method revealed that some of the PPD-LI neurons in the MDH and paratrigeminal nucleus projected to the thalamic regions. Nociceptive nature of the PPD-LI MDH neurons projecting to the thalamic regions was also demonstrated by a triple labeling method, using the technique of the noxious stimulus-evoked expression of the immediate-early gene, c-fos. In the rats which were subcutaneously injected with formalin into the upper and lower lips, c-fos protein (Fos) was found in PPD-LI neurons which were labeled with a retrograde tracer injected into the thalamic regions.

Animals↗

PubMed1999

Molecular cloning and characterization of rat trp homologues from brain.

Identification of trp (transient receptor potential) gene from Drosophila photoreceptor and subsequent molecular cloning of the human cDNA homologues suggest its participation in capacitative calcium entry (CCE) or so called store-operated Ca2+ channel (SOC). We identified five different trp-related amplifications of reverse-transcription-polymerase chain reaction (RT-PCR) from rat brain; these corresponded to mouse trp homologues, mtrp1,3,4,5,6 and were distributed in various tissues with multiple expression levels. Two cDNAs, homologous to Drosophila trp from rat brain, designated rtrp3 and rtrp6, were isolated and characterized. By RT-PCR analysis, mRNAs of rtrp3 and rtrp6 were found to be expressed differently in brain and other tissues. In situ hybridization analysis revealed that rtrp6 mRNA was preferentially expressed in hippocampal dentate gyrus and cortical layers II and III. Expression of rat TRP3 and TRP6 in COS cells revealed an increase in CCE, as compared to that in the mock-transfected COS cells of the control. Isolation of cDNAs of rat trp gene family provides a useful model for studying mechanism of CCE.

Animals↗

PubMed1999

Nisoldipine improves the impaired erythrocyte deformability correlating with elevated intracellular free calcium-ion concentration and poor glycaemic control in NIDDM.

AIMS: To explore the mechanisms underlying the impaired erythrocyte deformability (RBC-df) in diabetic patients, the relationship between erythrocyte intracellular free calcium-ion concentration ([Ca2+]i) and RBC-df, and the effects of Ca2+-channel blocker on [Ca2+]i and RBC-df were evaluated. METHODS: Forty-eight patients with NIDDM and 24 control subjects were enrolled in this study. [Ca2+]i was determined using fura-2, and RBC-df by filtration method expressed as Deformability Index (DI). Erythrocytes were treated with nisoldipine to evaluate the effects of a Ca2+-channel blocker. RESULTS: [Ca2+]i was significantly higher (82.6 (78.0-87.2) vs 76.6 (74.3-81.2) nmol lRBC-1, P<0.001), and DI was significantly lower (0. 14 (0.09-0.28) vs 0.22 (0.16-0.28), P<0.01) in NIDDM than in controls. There was a significant correlation between HbA1c and [Ca2+]i (r=0.38, P<0.01), between HbA1c and DI (r=-0.51, P<0.01), and between [Ca2+]i and DI (r=-0.42, P<0.01). Stepwise multiple regression analysis revealed HbA1c and [Ca2+]i as independent determinants for the impaired RBC-df. Nisoldipine treatment in vitro significantly decreased [Ca2+]i, and significantly improved RBC-df. CONCLUSIONS: These data indicate that the impaired RBC-df in NIDDM may at least partly be attributed to the elevated [Ca2+]i and poor glycaemic control. In addition, favorable effects of a Ca2+-channel blocker on both [Ca2+]i and RBC-df have been demonstrated.

Adult↗

PubMed1999

Lens regeneration in Xenopus is not a mere repeat of lens development, with respect to crystallin gene expression.

The spatio-temporal expression of three crystallin genes (alpha A, beta B1 and gamma) in lenses of Xenopus laevis was studied by in situ hybridization to compare the process of lens formation in embryonic development with that of lens regeneration from cornea that occurs in the tadpole. During embryonic lens development, all three crystallin transcripts were initially detected at the same stage of lens placode formation, and subsequently their signals became restricted to the presumptive lens fiber region. At later stages, the three crystallin genes were expressed in primary and secondary lens fibers, but not in lens epithelium. During lens regeneration, alpha A- and beta B1-crystallin signals were first detected in the presumptive lens fiber region of the lens vesicle. The expression of gamma-crystallin, however, appeared later than the other two crystallin genes and was detected only in morphologically discernible lens fibers. In the later stages of lens regeneration, expression of these crystallins was observed only in the lens fiber region, similar to embryonic lens development. These results reveal that lens regeneration from the inner layer of the outer cornea is not simply a repetition of embryonic lens development, when examined at the level of crystallin gene transcription.

Amino Acid Sequence↗

PubMed1999

Pax-6 and Prox 1 expression during lens regeneration from Cynops iris and Xenopus cornea: evidence for a genetic program common to embryonic lens development.

Lens regeneration from non-lens ocular tissues has been well documented in amphibians, from the dorsal iris in the newt and from the outer cornea in Xenopus. To understand the early molecular events which govern lens regeneration, we examined the expression of two early marker genes of normal lens development, Pax-6 and Prox 1. In both Cynops (newt) iris and Xenopus cornea, Pax-6 is expressed soon after lentectomy in a region broader than that giving rise to the regenerating lens, indicative of an important role for Pax-6 in determination of the regeneration potential. Then Prox 1 expression begins within the Pax-6-expressing tissue, and these Prox 1-expressing cells give rise to the regenerating lens. This sequence of events also takes place in the lens placode of the embryo, indicating that the presence of the same genetic program operates in both embryonic lens development and lens regeneration, at least partly. In the Cynops iris, Pax-6 expression occurs initially in the entire marginal region of the iris after lentectomy but then becomes restricted to the dorsal region. Further studies are expected to elucidate the mechanism of this long-standing problem of the dorsal-restriction of lens regeneration from the newt iris.

Amino Acid Sequence↗

PubMed1998

Projections from the caudal spinal trigeminal nucleus to commissural interneurons in the supratrigeminal region: an electron microscope study in the rat.

Electron microscopic double-labeling study in the rat indicated that projection fibers from the caudal spinal trigeminal nucleus (Vc) were distributed ipsilaterally within the supratrigeminal region (STR) capping the trigeminal motor nucleus (Tm) and made synaptic contact with neurons projecting to the contralateral Tm. Nociceptive inputs to the Vc may reflexly control, via interneurons in the STR, the activities of Tm neurons innervating the masticatory, tensor tympani, and/or tensor veli palatine muscles.

Animals↗

PubMed1998

Immunocytochemical localization of mu-opioid receptor in primary afferent neurons containing substance P or calcitonin gene-related peptide. A light and electron microscope study in the rat.

Co-expression of mu-opioid receptor-like immunoreactivity (MOR-LI) with substance P (SP)- or calcitonin gene-related (CGRP)-LI was observed in rat trigeminal and dorsal root ganglion neurons. In particular, MOR-LI was found in axon terminals with SP- or CGRP-LI in laminae I and II of the medullary and spinal dorsal horns. MOR may be implicated in modulation of release of SP and CGRP from primary sensory afferents.

Animals↗