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J Tanaka

Publications and source records attributed to J Tanaka.

At least 73 records · Page 4Linked to original sources
PubMed2001

Hemorrhage activates catecholaminergic neurons sensitive to GABA in the nucleus of the solitary tract with ascending projections to the subfornical organ in rats.

The activity of neurons in the region of the nucleus of the solitary tract (NTS) that were antidromically identified by electrical stimulation of the rat subfornical organ (SFO) was tested for a response to microiontophoretic application of gamma-aminobutyric acid (GABA), hemorrhage (10 ml/kg b.w.t.), or local administration of the chemical neurotoxin, 6-hydroxydopamine (6-OHDA), into the SFO stimulation site. Microiontophoretically (MIPh) applied GABA caused a decrease excitability in 22 out of 24 neurons tested, and the inhibition was blocked by MIPh-applied bicuculline, a GABAA antagonist, but not by phaclofen, a GABAB antagonist. Of these neurons that responded to GABA, 17 displayed an increase in neural firing in response to hemorrhage, while 5 were unresponsive. The occurrence of both antidromic spikes and post-stimulus inhibition of 9 out of 13 neurons tested was completely abolished by the injection of 6-OHDA into the SFO. These results suggest that neurons in the region of the NTS, which carry peripheral baroreceptor information to the SFO, receive GABAergic inhibitory inputs via a GABAA receptor mechanism, and imply that part of these neurons are catecholaminergic.

Action Potentials↗
PubMed2001

Estrogen decreases the responsiveness of subfornical organ neurons projecting to the hypothalamic paraventricular nucleus to angiotensin II in female rats.

Extracellular single-unit activity was recorded from subfornical organ (SFO) neurons antidromically identified as projecting to the hypothalamic paraventricular nucleus (PVN) in urethane-anesthetized ovariectomized female rats that were treated with either propylene glycol (PG) vehicle or estradiol benzoate (EB). No significant differences were observed between the PG- and EB-treated rats in the latency, conduction velocity, or threshold of antidromic activation. The mean spontaneous firing rate was significantly lower and the refractory period was significantly longer in the EB-treated rats. In the identified units that were activated by angiotensin II (ANG II) applied iontophoretically, the amount of excitatory response to intracarotid administration of ANG II was much greater in the PG-treated than in the EB-treated rats. These results suggest that estrogen may decrease the responsiveness of SFO neurons projecting to the PVN to circulating ANG II.

Action Potentials↗
PubMed2001

The role of nitric oxide in the gastric acid secretion induced by ischemia-reperfusion in the pylorus-ligated rat.

In a rat model of the ischemia-reperfusion with pylorus ligation, gastric ulcer was formed, although gastric acid secretion was reduced. When the polymorphonuclear leukocytes were inactivated in advance, gastric ulcer was not formed, but acid secretion was increased, indicating that gastric acid is not a cause of the ulcer formation in this model. The mechanism of gastric acid suppression accompanied by ischemia-reperfusion was examined in relation to the role of oxygen-free radicals in this rat model. Prior administration of superoxide dismutase did not modulate acid secretion, but N-nitro-L-arginine methyl ester (L-NAME) increased acid secretion. The action of L-NAME was antagonized specifically by L-arginine, but not by D-arginine. S-nitroso-N-acetylpenicillamine did not inhibit basal acid secretion but antagonized the action of L-NAME. Aminoguanidine increased significantly the gastric acid output that was suppressed by ischemia-reperfusion. When polymorphonuclear leukocytes were inactivated by treatment with their antibody, the gastric acid output recovered to the level in the pylorus-ligated rat without ischemia-reperfusion. These results suggested that nitric oxide (NO) produced by the infiltrated polymorphonuclear leukocytes plays an important role in the suppression of acid secretion induced by ischemia-reperfusion.

Animals↗
PubMed2001

Zinc-induced activation of the human cytomegalovirus major immediate-early promoter is mediated by metallothionein and nuclear factor-kappaB.

We previously reported that major immediate-early promoter (MIEP) activity was regulated by intercellular zinc levels. In this report, we elucidate the mechanisms involved in this phenomenon. In luciferase reporter assays, zinc-induced activation of MIEP (-735/+62) was decreased with deletion of the promoter in stages, and MIEP (-117/+62) did not respond to zinc. The time course of the activity of MIEP responding to diethylenetriamine pentaacetic acid and zinc was not parallel with metallothionein (MT) promoter, which contains metal responsive elements. SV40 promoter that contains AP-1 binding sites, a candidate for the zinc-responsive motif in the MIEP, was not affected by zinc under our conditions. The activation of MIEP (-735/+62) by zinc was prevented with NF-kappaB decoy. When three kappaB motifs from the enhancer in the MIEP were inserted in the front of the zinc-nonresponsive MIEP (-117/+62), it became responsive to zinc. Moreover, overexpression of MT up-regulates the DNA binding of NF-kappaB and NF-kappaB-induced activation of transcription. These findings strongly suggest that MT and NF-kappaB act as mediator/regulator in zinc-induced activation of MIEP.

Antigens, Viral↗
PubMed2001

Capillary electrophoresis of sialic acid-containing glycoprotein. Effect of the heterogeneity of carbohydrate chains on glycoform separation using an alpha1-acid glycoprotein as a model.

alpha1-Acid glycoprotein (AGP) showed multiple peaks on separation using capillary electrophoresis in a chemically modified capillary with dimethylpolysiloxane at slightly acidic conditions. We analyzed glycoforms of AGP species after separation by ion-exchange chromatography, Con A affinity chromatography, and Cu(II)-chelating affinity chromatography. The AGP species thus obtained were digested with N-glycosidase F, and the released carbohydrate chains were analyzed by high-performance liquid chromatography after labeling with 3-aminobenzoic acid. The results afforded basic information on the contribution of carbohydrate chains to the separation mechanism of glycoforms of AGP by capillary electrophoresis. In addition, we describe an easy method for AGP analysis in serum samples using the electrokinetic injection.

Carbohydrate Sequence↗
PubMed2001

L-Serine regulates the activities of microglial cells that express very low level of 3-phosphoglycerate dehydrogenase, an enzyme for L-Serine biosynthesis.

Microglia are well known to become activated during various kinds of neuropathological events. The factors that are responsible for the activation, however, are not fully determined. In the present study, L-Ser was shown to enhance production of nitric oxide (NO), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF alpha) by lipopolysaccharide (LPS)-stimulated cultured rat microglial cells. L-Ser, however, did not enhance the expression of mRNAs encoding inducible NO synthase, IL-6 and TNF alpha. On the other hand, astrocytes did not depend on L-Ser for release of IL-6 and TNF alpha. The expression of an enzyme 3-phosphoglycerate dehydrogenase (3PGDH), which is essential for L-Ser biosynthesis from a glycolytic intermediate 3-phosphoglycerate, was investigated. As revealed by Western blotting and immunocytochemical staining, 3PGDH-protein expression in vitro was the highest in astrocytes, intermediate in neurons and the lowest in microglial cells. Semiquantitative RT-PCR showed that microglial cells expressed 3PGDH-mRNA at a lower level than astrocytes. In frozen sections from rat forebrain, only astrocytes were immunoreactive for 3PGDH. The present study suggested that L-Ser is able to modulate microglial function mainly at the translation level because microglial cells cannot synthesize sufficient amount of L-Ser due to the scarce expression of 3PGDH.

Animals↗
PubMed2001

The role of color in high-level vision.

Traditional theories of object recognition have emphasized the role of shape information in high-level vision. However, the accumulating behavioral, neuroimaging and neuropsychological evidence indicates that the surface color of an object affects its recognition. In this article, we discuss the research that examines the conditions under which color influences the operations of high-level vision and the neural substrates that might mediate these operations. The relationship between object color and object recognition is summarized in the 'Shape+Surface' model of high-level vision.

Journal Article↗
PubMed2001

The biocompatibility and osteoconductive activity of a novel hydroxyapatite/collagen composite biomaterial, and its function as a carrier of rhBMP-2.

A hydroxyapatite/type I collagen (HAp/Col) composite, in which the hydroxyapatite nanocrystals align along the collagen molecules, has been prepared. The biocompatibility, osteoconductive activity, and efficacy as a carrier of recombinant human bone morphogenetic proteins (rhBMPs) of this novel biomaterial were examined. The composite material was implanted in the backs of Wistar rats, and specimens were collected for histological observations until week 24. In a second experiment, other samples of the composite material (5 x 5 x 10 mm3) were drilled and immersed in a solution of rhBMP-2 (0, 200, 400 microg/mL), and subsequently grafted in radii and ulnae in beagle dogs. As a control, three unfilled holes were left in one radius and ulna. X-ray images were prepared, and specimens collected for histological observation at weeks 8 and 12. Histological findings of the composites grafted in rats showed that the surface of the material was eroded as a result of macrophage infiltration. X-ray images and histological findings for the composites implanted in dogs support the idea that HAp/ Col has a high osteoconductive activity and is able to induce bone-remodeling units. In cases where the implants are grafted at weight bearing sites, treatment with rhBMP-2 at a dose of 400 microg/mL may be useful to shorten the time needed until bone union has occurred.

Animals↗
PubMed2001

Activation of the subfornical organ enhances extracellular noradrenaline concentrations in the hypothalamic paraventricular nucleus in the rat.

Experiments were carried out to investigate whether angiotensinergic efferent pathways from the subfornical organ (SFO) regulate the noradrenergic system in the region of the hypothalamic paraventricular nucleus (PVN). Intracerebral microdialysis techniques were utilized to quantify the extracellular content of noradrenaline (NA) in the PVN area. In urethane-anaesthetized male rats, electrical stimulation (5-20 Hz, 600 microA) of the SFO significantly increased the NA concentration in the region of the PVN, and the increase was significantly prevented by pretreatment with the angiotensin II (ANG II) antagonist saralasin (Sar, 5 microg), into the third ventricle (3V). Injections of ANG II (5 microg) into the 3V significantly enhanced NA release in the PVN area. These results suggest that the angiotensinergic pathways from the SFO to the PVN may act to enhance NA release in the region of the PVN.

Angiotensin II↗
PubMed2001

Angiotensinergic and noradrenergic mechanisms in the hypothalamic paraventricular nucleus participate in the drinking response induced by activation of the subfornical organ in rats.

The present study was done to investigate the contribution of the hypothalamic paraventricular nucleus (PVN) to the drinking response caused by activation of the subfornical organ (SFO) following angiotensin II (ANG II) injections in the awake rat. Microinjection of ANG II into the SFO elicited the drinking response. Previous injections of either saralasin, an ANG II antagonist, or phentolamine, an alpha-adrenoceptor antagonist, bilaterally into the PVN resulted in the significant attenuation of the drinking response to ANG II. Similar injections of any of the beta-adrenoceptor antagonist timolol, the muscarinic antagonist atropine, or saline vehicle into the PVN had no significant effect on the drinking response. In an attempt to clarify the neural mechanisms in the PVN involved in the drinking response to ANG II injected into the SFO, the effect of microinjection of ANG II into the SFO on noradrenaline (NA) release in the PVN was examined using intracerebral microdialysis techniques. The injection of the ANG II, but not saline vehicle, significantly enhanced the NA release in the region of the PVN. These results indicate the involvement of both the angiotensinergic and alpha-adrenergic systems in the PVN in the drinking response caused by angiotensinergic activation of the SFO, and imply that the angiotensinergic projections from the SFO to the PVN may serve to increase NA release which results in mediating water intake.

Adrenergic alpha-Antagonists↗
PubMed2001

Dipsogenic response induced by angiotensinergic pathways from the lateral hypothalamic area to the subfornical organ in rats.

Experimental observations in several species have suggested that angiotensinergic neural circuits from the lateral hypothalamic area (LHA) to the subfornical organ (SFO) may participate in the control of drinking behavior in the rat. In an attempt to verify this possibility, experiments were undertaken to investigate whether activation of LHA neurons following microinjection of angiotensin II (ANG II) into the LHA elicits drinking. Injections of ANG II (10(-11) mol) into the LHA caused drinking in 25 out of 36 rats having the tips of cannulas in the LHA. The efficacy of ANG II was potentiated by increasing the dose of the drug. To clarify the contribution of angiotensinergic neurons in the LHA with efferent projections to the SFO to the drinking induced by ANG II, the effects of pretreatment with saralasin (Sar), a specific ANG II antagonist, in the SFO or its surrounding region on the drinking to ANG II were examined. Previous injections of Sar into the SFO significantly reduced the water intake caused by ANG II injected into the LHA, whereas treatment with Sar in the ventral hippocampal commissure (VHC) or third ventricle (3V) was without effect. These findings provide the evidence for the involvement of the angiotensinergic pathways from the LHA to the SFO in the dipsogenic action.

Angiotensin II↗
PubMed2001

GABAergic modulation of neurons in the nucleus of the solitary tract with ascending projections to the subfornical organ in the rat.

Twenty-five neurons in the region of the nucleus of the solitary tract (NTS) were antidromically activated by electrical stimulation of the subfornical organ (SFO) in male rats under urethane anesthesia. Microiontophoretically applied bicuculline, a gamma-aminobutyric acid (GABA)(A) antagonist, but not phaclofen, a GABA(B) antagonist, attenuated the post-antidromic inhibitory response evoked by SFO stimulation of approximately two-third (n=17) of identified neurons, indicating the existence of recurrent inhibitory systems through GABA(A) receptors. Iontophoretically applied GABA decreased the spontaneous activity of all identified neurons, and the GABA-induced inhibition was prevented by simultaneously applied bicuculline, but not by phaclofen. Activation of peripheral baroreceptors, achieved by rising arterial blood pressure with an intravenous infusions of phenylepherine, suppressed the activity of the majority (n=20) of identified neurons. The inhibitory response of identified neurons (n=7) to baroreceptor activation was partially antagonized by iontophoretically applied bicuculline, but not by phaclofen. These results imply that GABAergic mechanisms may modulate the baroreceptor reflex acting on GABA(A) receptors of NTS neurons with ascending projections to the SFO in the region of the NTS.

Animals↗
PubMed2001

Preparation and microstructure analysis of chitosan/hydroxyapatite nanocomposites.

Chitosan/hydroxyapatite (HAp) composites with a homogeneous nanostructure have been prepared by a co-precipitation method. According to TEM observations, HAp crystallites in the composites formed elliptic aggregations 230 nm in length and 50 nm in width. The typical length of the aggregations corresponded approximately to that of a chitosan molecule. The size of the constituent HAp crystallites was found to be predominantly 30 nm in length and 10 nm in width, and the c-axes were well aligned in parallel with the chitosan molecules in the respective aggregations. The growth of the HAp crystallites is considered to occur at nucleation sites, most probably forming the complexes with amino groups on chitosan with calcium ions. The compact composites obtained have been found to be mechanically flexible, and this flexibility has been improved further by heating at 120 degrees C for 20 min in an autoclave with saturated steam pressure.

Biocompatible Materials↗
PubMed2001

A hydroxyapatite coating covalently linked onto a silicone implant material.

A novel composite consisting of hydroxyapatite (HAp) microparticles covalently coupled onto a silicone sheet was developed. Initially, an acrylic acid (AAc) -grafted silicone sheet with a 16.7 microg/cm(2) surface graft density was prepared by corona-discharge treatment. The surface of sintered, spherical, carbonated HAp particles with an average diameter of 2.0 microm was subsequently modified with amino groups. The amino group surface density of the HAp particles was calculated to be approximately one amino molecule per 1.0 nm(2) of particle surface area. These samples were characterized with Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. After the formation of ammonium ionic bonds between both samples under aqueous conditions, they were reacted at 180 degrees C for 6 h in vacuo to form covalent bonds through a solid-phase condensation. The HAp particles were coupled to the AAc-grafted silicone surface by a covalent linkage. Further improvements in the adhesive and bioactive properties of the HAp-coated silicone material are expected.

Acrylates↗
PubMed2001

In vivo evaluation of a novel porous hydroxyapatite to sustain osteogenesis of transplanted bone marrow-derived osteoblastic cells.

Biosynthetic bone grafts are considered to contain one or more of three critical components: osteoprogenitor cells, an osteoconductive matrix, and osteoinductive growth factors. The basic requirements of the scaffold material are biocompatibility, mechanical integrity, and osteoconductivity. A major design problem is satisfying these requirements with a single composite. In this study, we hypothesize that one composite that combines bone marrow-derived osteoblasts and a novel mechanical reinforced porous hydroxyapatite with good biocompatibility and osteoconductivity (HA/BMO) can reach these requirements. A novel sintered porous hydroxyapatite (HA) was prepared by the following procedures. The HA slurry was foamed by adding polyoxyethylenelaurylether (PEI) and mixing. The pores were fixed by crosslinking PEI with diepoxy compounds and the HA porous body was sintered at 1200 degrees C for 3 h. The HA sintered porous body had a high porosity (77%), and was completely interconnected. Average pore diameter was 500 microm and the interconnecting path 200 microm in diameter. The compressive (17 MPa) and three-point bending (7 MPa) strengths were high. For in vivo testing, the 2-week subcultured HA/BMO (+) composites were implanted into subcutaneous sites of syngeneic rats until 8 weeks after implantation. These implants were harvested at different time points and prepared for the biochemical analysis of alkaline phosphatase activity (ALP) and bone osteocalcin content (OCN), and histological analysis. ALP and OCN in the HA/BMO group were much higher than those in the HA without BMOs control group 1 week after implantation (p < 0.001). Light microscopy revealed mature bone formation in the HA/BMO composite 4 weeks after implantation. In the SEM study, mineralized collagenous extracellular matrix was noted in HA/BMO composite 2 weeks after implantation with numbers of active osteoblasts. We conclude that the composite of the novel HA and cultured BMOs has osteogenic ability in vivo. These results provide a basis for further studies on the use of this composite as an implant in orthopaedic surgery.

Alkaline Phosphatase↗
PubMed2001

Activation of serotonergic pathways from the midbrain raphe system to the subfornical organ by hemorrhage in the rat.

The role of serotonergic neural pathways from the midbrain raphe nuclei to the subfornical organ (SFO) in the central regulation of cardiovascular function and body fluid balance was investigated in adult male rats under urethane anesthesia. Eleven neurons in the dorsal raphe nucleus (DR) were antidromically activated by electrical stimulation of the SFO. Of these neurons, 6 displayed an excitatory response following hemorrhage (10 ml/kg bwt) while the remaining 5 neurons were unresponsive. Ninety-four neurons in the SFO were tested for a response to electrical stimulation of the DR or hemorrhage. Electrical stimulation of the DR caused orthodromic excitation (19%) or inhibition (5%) of the activity of SFO neurons. In 14 of 18 SFO neurons that displayed the excitation to the stimulation of the DR, hemorrhage (30 to 50 mm Hg suppression in mean arterial pressure) produced an increase of their discharge, while the stimulus was without effect in the remaining neurons responsive to the stimulation of the DR. The effects of hemorrhage on serotonin (5-HT) release in the region of the SFO were examined using intracerebral microdialysis techniques. Hemorrhage significantly increased 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the region of the SFO. The present data suggest that the serotonergic pathways from the DR to the SFO may relay activation of the peripheral baroreceptors to SFO neurons which result in enhanced excitability, indicating the involvement of the pathways in the regulation of cardiovascular function.

Action Potentials↗
PubMed2001

Estrogen decreases the responsiveness of subfornical organ neurons to angiotensinergic neural inputs from the lateral hypothalamic area in the female rat.

Twenty-eight subfornical organ (SFO) neurons in ovariectomized (OVX) female rats that were treated with propylene glycol (PG) vehicle and 26 SFO neurons in OVX female rats that were treated with estrogen benzoate (EB) were antidromically activated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN) under urethane anesthesia. No significant differences were observed between the PG-treated and EB-treated OVX animals in the latency, conduction velocity, or threshold of antidromic activation. The mean spontaneous discharge rate was significantly lower in the EB-treated than in the PG-treated OVX animals. In both groups, the activity of the majority (86% in the PG-treated animals and 88% in the EB-treated animals) of identified SFO neurons were activated by microiontophoretic application of angiotensin II (ANG II). Electrical stimulation of the lateral hypothalamic area (LHA) increased the excitability of these ANG II-sensitive SFO neurons (58% in the PG-treated animals and 52% in the EB-treated animals). The excitatory response to either ANG II or LHA stimulation was blocked by microiontophoretic application of the ANG II antagonist saralasin (Sar), suggesting that the excitatory response to LHA stimulation may be mediated by angiotensinergic LHA projections to the SFO. The magnitude of excitatory response to either ANG II or the LHA stimulation was much greater in the PG-treated than in the EB-treated animals. These results suggest that estrogen decreases the responsiveness of SFO neurons projecting to the PVN to angiotensinergic inputs from the LHA.

Angiotensin II↗