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Biomedical subjects

N Yamamoto

Publications and source records attributed to N Yamamoto.

At least 361 records · Page 20Linked to original sources
PubMed1998

Telencephalic ascending gustatory system in a cichlid fish, Oreochromis (Tilapia) niloticus.

Central fiber connections of the gustatory system were examined in a percomorph fish Oreochromis (Tilapia) niloticus by means of the horseradish peroxidase (HRP), biocytin, and carbocyanine dye tracing methods. The primary gustatory areas in tilapia are the facial, glossopharyngeal, and vagal lobes of the medulla. The secondary gustatory nucleus (SGN) is a dumb-bell-shaped structure located in the isthmic region. In the SGN, there are two or three layers of neurons lining the ventromedial periphery of the nucleus and a molecular layer constituting of the major part of the nucleus. The SGN receives bilateral projections from the facial lobes and ipsilateral projections from the glossopharyngeal and vagal lobes. Ascending fibers originating from the SGN form the ipsilateral tertiary gustatory tract. A major part of the tract courses rostrally and terminates ipsilaterally in several diencephalic nuclei: the preglomerular tertiary gustatory nucleus (pTGN), the posterior thalamic nucleus, the nucleus diffusus lobi inferioris, the nucleus centralis of inferior lobe, and the nucleus recessus lateralis. The remaining small fiber bundle enters the medial and lateral forebrain bundles and terminates directly in two telencephalic regions; the area ventralis pars intermedia (Vi) and the area dorsalis pars posterior (Dp). Ascending fibers from the pTGN pass through the lateral forebrain bundle and terminate ipsilaterally in the dorsal region of area dorsalis pars medialis (dDm) of the telencephalon. Following biocytin injections into the dDm, small, round cells were labeled in the pTGN. After biocytin injections into the Vi and Dp of the telencephalon, retrogradely labeled cells were found in the ipsilateral SGN. The results show that the ascending fiber connections of the central gustatory system in the percomorph teleost tilapia are essentially similar to those of mammals. That is, the pathway from the primary gustatory areas (facial, glossopharyngeal, and vagal lobes) through the SGN and pTGN to the dDm in tilapia corresponds with the mammalian gustatory pathway from the solitary nucleus through the pontine taste areas (nucleus parabrachialis) and the thalamic relay nucleus (ventral posteromedial nucleus) to gustatory neocortices. In addition, the pathway from the primary gustatory areas through the SGN to the Vi and Dp in tilapia corresponds with the pathway from the solitary nucleus through the pontine taste areas to the amygdala in mammals.

Afferent Pathways↗
PubMed1998

Human T-cell leukemia virus type 1 Tax protein induces the expression of lymphocyte chemoattractant SDF-1/PBSF.

We investigated the mechanism of lymphocyte infiltration into tissues infected with human T-cell leukemia virus type 1 (HTLV-1). The cytokine SDF-1/PBSF is a highly efficient chemoattractant for lymphocytes. Reverse transcription-PCR analysis showed that among various human T-cell lines, those infected with HTLV-1 selectively expressed the SDF-1 gene. Expression of the viral protein Tax in a human T-cell line induced the expression of the SDF-1 gene, indicating that the constitutive expression of SDF-1 in virus-infected cell lines is at least in part mediated by Tax. HTLV-1-infected T-cell lines also expressed CXCR-4, a receptor for SDF-1. Moreover, chemotaxis assay showed that a HTLV-1-infected cell line migrated toward synthetic SDF-1. Thus, HTLV-1-infected cells are themselves responders for SDF-1. Our results suggest that SDF-1 induced by Tax may alter the distribution of HTLV-1-infected cells in vivo; hence it may contribute to their infiltration into affected tissues in HTLV-1-associated inflammatory diseases.

Animals↗
PubMed1998

Expression of FAP-1 (Fas-associated phosphatase) and resistance to Fas-mediated apoptosis in T cell lines derived from human T cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis patients.

Human T cell leukemia virus type 1 (HTLV-I) is the etiologic agent of HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) with an autoimmune condition. We examined the sensitivity of HTLV-I-infected T cell lines to Fas-mediated apoptosis, which plays a critical role in the elimination of self-reactive T cells. Among 13 human T-cell lines, all 4 HAM-derived T cell lines and 4 of 6 non-HAM/HTLV-I T cell lines were resistant to apoptosis induced by anti-Fas antibody, whereas only 1 of 3 uninfected cell lines was resistant to apoptosis. The cell lines resistant to apoptosis expressed the viral tax gene and/or the cellular FAP-1 (Fas-associated phosphatase) gene, both of which inhibit Fas-mediated apoptosis in T cell lines. Although Tax is a transcriptional activator of a number of cellular genes, the expression of Tax in a T cell line did not induce the expression of FAP-1, suggesting that these two antiapoptotic proteins independently function in HTLV-I-infected cells. Seven of 10 HTLV-I-infected cell lines, compared with only 1 of 3 virus-negative cell lines, expressed FAP-1. All four HAM cell lines expressed the FAP-1 gene, and its level in these cells was higher than in other T cell lines. Our results suggest that virus-infected T cells escape Fas-mediated immune surveillance by the function of Tax and FAP-1, and this escape may be involved in the autoimmune condition observed in HAM/TSP patients.

Apoptosis↗
PubMed1998

Inhibition of human T-cell leukemia virus type 1 replication by antisense env oligodeoxynucleotide.

Human T-cell leukemia virus type 1 (HTLV-1) infection is associated with adult T-cell leukemia and HTLV-associated myelopathy/tropical spastic paraparesis. Inhibition of HTLV-1 transmission is important to prevent the above HTLV-1-associated diseases. We used the antisense oligodeoxynucleotides (oligos) complementary to the first splice junction, rex responsive site, gag, env, tax, rex, and p21 and evaluated the effects on the syncytium formation between HTLV-1 producing human T-cell line, C9/PL cells, and HTLV-1-uninfected human glioma cell line, U251-MG cells. The syncytium formation was significantly inhibited the virion production assayed by antisense oligos to env, tax, gag, p21, and rex, with antisense oligo to env being the most inhibitory. Antisense oligos to env and tax also inhibited reverse transcriptase activity. Antisense oligo to env may have a potential as a preventive measure of HTLV-1 replication and transmission in vivo.

Base Sequence↗
PubMed1998

Gonadotropin-releasing hormone neurons in the gourami midbrain: a double labeling study by immunocytochemistry and tracer injection.

There are three groups of gonadotropin-releasing hormone (GnRH) neurons in the teleost brain. Midbrain GnRH neurons in the dwarf gourami send axons to various areas of the central nervous system. However, it is not clear whether midbrain GnRH neurons form a cell cluster separate from the nucleus of the medial longitudinal fasciculus (nMLF), which has been reported to project to the spinal cord. Thus, we performed a double labeling study. GnRH neurons were immunostained but were very faintly labeled with biocytin injected into the spinal cord. In contrast, nMLF neurons were strongly labeled with biocytin but were GnRH-immunonegative. GnRH neurons are distributed at almost the same rostrocaudal levels as nMLF neurons, but they constitute a separate cell group dorsocaudal to nMLF neurons.

Animals↗
PubMed1998

Shedding of the soluble IL-6 receptor is triggered by Ca2+ mobilization, while basal release is predominantly the product of differential mRNA splicing in THP-1 cells.

The soluble IL-6 receptor (sIL-6R) is generated through either proteolytic shedding of the cognate receptor (PC-sIL-6R), or released as the product of differential mRNA splicing (DS-sIL-6R). Using monocytic THP-1 cells, we demonstrate that both mechanisms are independently regulated, and that each process contributes to sIL-6R production. Shedding of the IL-6R was activated by the Ca2+ ionophore, ionomycin, and inhibited by the TNF-alpha protease inhibitor (TAPI). In contrast, basal sIL-6R release was unaffected by Ca2+ depletion and largely insensitive to TAPI. Moreover, although IL-6R shedding was inactivated by serum starvation, non-stimulated production remained intact. Basal sIL-6R production via differential mRNA splicing was shown through the inhibitory action of brefeldin A and an enzyme-linked immunosorbent assay specific for DS-sIL-6R. Release of this isoform was unaffected by ionomycin or TAPI, indicating that Ca2+ mobilization activates PC-sIL-6R generation, but not DS-sIL-6R. The divergent control of these sIL-6R isoforms indicates that they may independently influence the inflammatory response.

Animals↗
PubMed1998

GnRH-immunoreactive neuronal system in the presumptive ancestral chordate, Ciona intestinalis (Ascidian).

Gonadotropin-releasing hormone (GnRH) of the vertebrate brain, which has originally been identified as a peptidergic hypophysiotropic hormone, is now believed to act also as a neuromodulator. It has recently been shown that a vertebrate-like GnRH-gonadotropin system occurs in the urochordates, which are considered to be the presumptive ancestral chordate. In this paper, we examined the morphology of the GnRH neuronal system of ascidian, Ciona intestinalis, by immunocytochemistry and found many GnRH-immunoreactive neuronal cells and fibers in a specific surface area of the cerebral ganglion, along the inner wall of the dorsal blood sinus, as well as on the anterior surface of the ovary.

Animals↗
PubMed1998

Nine-year survivor after resection of cholangiocellular carcinoma with tumor thrombi in the main portal trunk.

We report a patient with cholangiocellular carcinoma with tumor thrombi in the main portal trunk who has survived for 9.5 years after hepatic resection. A 57-year-old woman underwent an extended left lobectomy, and resection of the caudate lobe plus the main portal trunk for a liver tumor that had a portal tumor thrombus in the main portal trunk. The portal vein was reconstructed with an autologous vein graft obtained from the external iliac vein. Histological examination of the resected specimen revealed moderately differentiated tubular adenocarcinoma compatible with cholangiocellular carcinoma. Factors contributing to the patient's long-term survival are discussed. Aggressive surgical resection can be effective even for such an advanced case of cholangiocellular carcinoma.

Bile Duct Neoplasms↗
PubMed1998

Interleukin-6 and development of vasospasm after subarachnoid haemorrhage.

The authors characterized the role of interleukins in the cerebrospinal fluid (CSF) in the development of vasospasm after subarachnoid haemorrhage (SAH), particularly interleukin-6 (IL-6). Concentrations of interleukin-1 beta (IL-1 beta), IL-6, and interleukin-8 (IL-8) were measured serially in CSF of 24 patients and in serum of 9 patients with SAH and correlated clinically. Additionally, the effects of the same cytokines on the cerebral arteries of dogs were analyzed on angiograms after intracisternal injection. Changes in levels of eicosanoids, angiogenic factors, and soluble cell adhesion molecules were investigated in the CSF of injected dogs. CSF concentrations of IL-6 and IL-8 were elevated significantly above control levels from the acute stage of SAH until the chronic stage. Patients with symptomatic vasospasm had significantly higher levels of IL-6 as well as IL-8 in CSF on days 5 and 7. Intracisternal injection of IL-6 induced long-lasting vasoconstriction in five out of eight dogs, while IL-8 did not. The diameter of canine basilar artery after IL-6 was reduced 29 +/- 5% from pretreatment diameter at 8 hours. Prostaglandins E2 and I2 were elevated in CSF for the first 4.5 hour of this IL-6-induced vasospasm. Neither angiogenic factors such as platelet-derived growth factor-AB and vascular endothelial growth factor nor soluble cell adhesion molecules were significantly elevated in CSF. IL-6, which increases to very high concentrations in CSF after SAH, may be important in inducing vasospasm, as IL-6 produced long-lasting vasoconstriction in the canine cerebral artery, which may be partly related to activation of the prostaglandin cascade.

Animals↗
PubMed1998

Effects of kynurenine metabolites on the electrocorticographic activity in the rat.

We examined the effects of kynurenine metabolites administered into the right cerebroventricle (1 micromol) on the electrocorticogram (ECoG) of rats to establish the role of kynurenines on brain function. Kynurenine, anthranilic acid, quinaldic acid, xanthurenic acid or 8-hydroxyquinaldic acid showed no effect on ECoG throughout the recording period of 4 hours. 3-Hydroxykynurenine had a transient suppressive effect on the ECoG, while kynurenic acid caused a slight suppression of ECoG activity. 3-Hydroxyanthranilic acid (3-OH-An), a metabolite of 3-hydroxykynurenine, induced spike discharges with a long latency (60-230 min). 3-OH-An is thought to be metabolized to o-aminophenol, 3-methoxyanthranilic acid, quinolinic acid, 2-ketoadipic acid and picolinic acid. Among 3-OH-An metabolites, only o-aminophenol induced spike discharges several minutes after administration, lasting for 60 min. On the other hand, quinolinic acid suppressed ECoG, though 3-methoxyanthranilic acid, 2-ketoadipic acid and picolinic acid had no effects on ECoG. These electrocorticographic findings suggest that 3-OH-An may induce spike discharges after it is metabolized in the brain to o-aminophenol.

3-Hydroxyanthranilic Acid↗
PubMed1998

Evidence of vascular growth associated with laser treatment of normal canine myocardium.

BACKGROUND: Transmyocardial laser revascularization is a new therapy for patients with refractory angina. Although clinical studies suggest that transmyocardial laser revascularization decreases angina and may improve regional blood flow, the underlying mechanisms are not elucidated. We hypothesized that one mechanism may relate to stimulation of vascular growth in laser-treated regions. METHODS: Transmyocardial laser revascularization channels were made with holmium:yttrium-aluminum garnet or carbon dioxide lasers in eight normal canine hearts; animals were sacrificed 2 to 3 weeks later and examined for vascular density and for evidence of smooth muscle proliferation. RESULTS: The original channels were infiltrated by granulation tissue with associated vascularity. Vascular growth was stimulated immediately surrounding the channel remnant as evidenced by an increase in the number of vessels (approximately twice that of the control region) and an increase in the number of vascular cells staining positive for markers of cellular proliferation. CONCLUSIONS: Transmyocardial laser revascularization leads to local vascular growth as early as 2 weeks after treatment. It remains to be determined whether this mechanism contributes to increased regional blood flow or to clinical benefits associated with this novel form of therapy.

Aluminum Silicates↗
PubMed1998

Regioselective syntheses of sulfated polysaccharides: specific anti-HIV-1 activity of novel chitin sulfates.

A novel and convenient method for the regioselective syntheses of sulfated analogs of chitin and chitosan is described in relation to studies on structure-biological activity. Fully protected, soluble derivatives of chitosan were found to be useful intermediates for the syntheses of a novel class of sulfated polysaccharides, 2-acetamido-2-deoxy-3-O-sulfo-(1-->4)-beta-D-glucopyranan (3-sulfate, 3S, 4) and (1-->4)-2-deoxy-2-sulfoamido-3-O-sulfo-(1-->4)-beta-D-glucopyranan (2,3-disulfate, 23-S, 3). These compounds were tested for their activities in (i) inhibiting HIV-1 replication in vitro and (ii) inhibiting blood coagulation. The results reveal that the selective sulfation at O-2 and/or O-3 affords potent antiretroviral agents showing a much higher inhibitory effect on the infection of AIDS virus in vitro than that by the known 6-O-sulfated derivative (6-sulfate, 6S). Moreover, the 23-S product completely inhibited the infection of AIDS virus to T lymphocytes at concentrations as low as 0.28 microgram/mL without significant cytotoxicity. The regioselective introduction of sulfate group(s) at O-2 and/or O-3 had little effect on generating anticoagulant activity, whereas 6-O-sulfated chitin strongly inhibits blood coagulation. These results suggest that the specific interaction of these new types of chitin sulfates with gp 120 of the AIDS virus depends significantly on the sites of sulfation rather than on the total degree of substitution on sugar residues.

Animals↗
PubMed1998

Synthesis of sulfonated amino-polysaccharides having anti-HIV and blood anticoagulant activities.

Sulfonated 3-amino-3-deoxy-(1-->6)-alpha-D-allopyranans were synthesized to elucidate the relationship between structure and such specific biological activities as anti-HIV and blood anticoagulant activities. Ring-opening copolymerization of 1,6-anhydro-3-azido-2,4-di-O-benzyl-3-deoxy-beta-D-allopyranose 1 with 1,6-anhydro- 2,3,4-tri-O-benzyl-beta-D-allopyranose 2 with PF5 catalyst gave copolymers having various proportions of the 1 unit. 13C NMR spectroscopy showed the resulting copolymers to have alpha-(1-->6)-stereoregularity, and the monomer reactivity ratios were calculated to be r1 = 0.92 and r2 = 1.11 by the Kelen-Tüdös method. Reduction of the azido groups and subsequent debenzylation of the copolymers afforded new amino-polysaccharides consisting of 3-amino-3-deoxy-allose and allose units. Sulfonation of 3-amino-3-deoxy-(1-->6)-alpha-D-allopyranan and copolysaccharides consisting of 3-amino-allose and allose or glucose units was performed with piperidine-N-sulfonic acid to give polysaccharides containing sulfoamido and sulfonate groups in good yields. The sulfoamido-copolysaccharides containing of 3-amino-3-deoxy-allose and glucose units exhibited high anti-HIV activities manifested by the 50% protecting concentration (EC50) of 0.2-0.5 mg/mL and low cytotoxicity shown by a 50% cytotoxic concentration (CC50) of > 1000 micrograms/mL. The sulfoamido-copolysaccharides containing 3-amino-allose and allose units had somewhat lower anti-HIV activities (EC50 = 0.8-0.9 microgram/mL) and slightly higher cytotoxicities (CC50 = 740-797 micrograms/mL). In addition, it was found that the blood anti-coagulant activity increased, with increasing proportion of the amino-allose unit, from 30 to 58 unit/mg (standard dextran sulfate, 22.7 unit/mg). These results suggest that the sulfonated 3-amino-3-deoxyallose unit plays important roles on both anti-HIV and blood anticoagulant activities.

Animals↗
PubMed1998

Coronary sinus pacing initiates counterclockwise atrial flutter while pacing from the low lateral right atrium initiates clockwise atrial flutter. Analysis of episodes of direct initiation of atrial flutter.

INTRODUCTION: Rapid atrial pacing in sinus rhythm may directly induce atrial flutter without provoking intervening atrial fibrillation, or initiate atrial flutter indirectly, by a conversion from an episode of transient atrial fibrillation provoked by rapid atrial pacing. The present study was performed to examine whether or not the direct induction of clockwise or counterclockwise atrial flutter was pacing-site (right or left atrium) dependent. METHODS AND RESULTS: We analyzed the mode of direct induction of atrial flutter by rapid atrial pacing. In 46 patients with a history of atrial flutter, rapid atrial pacing with 3 to 20 stimuli (cycle length = 500 - 170 ms) was performed in sinus rhythm to induce atrial flutter from 3 atrial sites, including the high right atrium, the low lateral right atrium, and the proximal coronary sinus, while recording multiple intracardiac electrograms of the atria. Direct induction of atrial flutter by rapid atrial pacing was a rare phenomenon and was documented only 22 times in 15 patients: 3, 11, and 8 times during stimulation, respectively, from the high right atrium, low lateral right atrium, and the proximal coronary sinus. Counterclockwise atrial flutter (12 times) was more frequently induced with stimulation from the proximal coronary sinus than from the low lateral right atrium (8 vs 1, P = .0001); clockwise atrial flutter (10 times) was induced exclusively from the low lateral right atrium (P = .0001 for low lateral right atrium vs proximal coronary sinus, P = .011 for low lateral right atrium vs high right atrium). CONCLUSIONS: Direct induction of either counterclockwise or clockwise atrial flutter was definitively pacing-site dependent; low lateral right atrial pacing induced clockwise, while proximal coronary sinus pacing induced counterclockwise atrial flutter. Anatomic correlation between the flutter circuit and the atrial pacing site may play an important role in the inducibility of counterclockwise or clockwise atrial flutter.

Adult↗
PubMed1998

Influenza A virus infection increases IgE production and airway responsiveness in aerosolized antigen-exposed mice.

BACKGROUND: Respiratory viral infection is known clinically to promote sensitization to antigen inhalation and the development of asthma. OBJECTIVE: The purpose of this investigation was to determine whether influenza type A virus infection enhances inhalation sensitization and increases airway responsiveness in mice. METHODS: Mice were infected by intranasal inoculation with influenza A viruses (strains: H1N1 and H3N2) or PBS. Animals were exposed to aerosols of ovalbumin on day 3. Two weeks after ovalbumin sensitization, mice were challenged with ovalbumin aerosols; 24 hours later, airway responsiveness (AR) to inhaled methacholine, levels of ovalbumin-specific IgE, and bronchoalveolar lavage fluid (BALF) were examined. RESULTS: Neither influenza A virus (H1N1 nor H3N2) alone nor ovalbumin sensitization alone caused changes in AR or IgE. However, ovalbumin sensitization after inoculation with either influenza A virus increased AR and levels of ovalbumin-specific IgE. On BALF-cell analysis, ovalbumin sensitization after inoculation with influenza virus A increased the number of lymphocytes but not the number of eosinophils. No difference in AR or IgE levels was observed between the 2 strains of influenza A viruses. Immmunostaining of BALF cells showed an increase in T cells, especially CD8(+) cells, with ovalbumin sensitization after inoculation with influenza virus A. CONCLUSION: Infection by influenza A virus enhances sensitization to inhaled antigens and airway responsiveness in mice by means of mechanisms including CD8(+) cells and antigen-specific IgE.

Acute-Phase Reaction↗
PubMed1998

Preoptic gonadotropin-releasing hormone (GnRH) neurons innervate the pituitary in teleosts.

In most teleosts, there are three groups of gonadotropin-releasing hormone (GnRH) neurons. In this study we addressed the question of GnRH neuronal innervation of the pituitary in the dwarf gourami and the tilapia using immunocytochemistry combined with biocytin tract tracing. Biocytin was applied to the pituitary attached to the brain in vitro. Similar results were obtained in both species. GnRH neurons retrogradely labeled with biocytin were observed only in the preoptic area. These results indicate that preoptic GnRH neurons innervate the pituitary. Negative labeling of biocytin in the terminal-nerve and midbrain GnRH neurons suggests that these two GnRH neuronal populations do not project to the pituitary. Biocytin-positive but GnRH-negative neurons were also observed in the preoptic area and the ventromedial parts of the hypothalamus, suggesting neuropeptidergic and aminergic innervation of the pituitary besides GnRH.

Animals↗
PubMed1998

Service use by family caregivers in Japan.

This paper presents a conceptual framework for understanding how Japanese family caregivers make decisions about the use of formal services such as adult day care, short term hospital stays, and long-term institutionalization. Using grounded theory methodology, 26 Japanese daughters or daughters-in-law who were caring for an elderly demented parent or parent-in-law were interviewed. From these data, an overall process of "navigating among endorsed options" evolved. This process was set in motion when caregivers reached the limit of their tolerance, a point at which they felt they could not continue caregiving under the given arrangement. Caregivers then began to assess three issues which determined whether or not they used formal services: the availability of services; their authority level within the family; and whether or not they could justify their tolerance limit. The availability of a service was determined by the quality of the service, the distance to the service, the sanctions that would incur as a result of using the service, information about the service, and the quantity of the service. The caregivers' authority within the family varied depending on such factors as how much the caregiver was accepted by her married family or the type of family business. This authority level determined whether and how the caregivers could approach other family members in order to obtain their consent to use formal services. Finally, whether the caregivers could justify their tolerance limit depended on the internalization of the societal norm regarding family caregiving, attachment to the care recipient, and the caregiver's belief on how care should be given. Justification of their limit included re-prioritizing the needs of family members, acting in defiance of societal norm, and redefining reality. Each of the three issues was assessed in relation to the others with the final decision to use or not use formal services based on the balance of forces.

Adult↗