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Biomedical subjects

K Konno

Publications and source records attributed to K Konno.

At least 91 records · Page 5Linked to original sources
PubMed1997

Alpha-pompilidotoxin (alpha-PMTX), a novel neurotoxin from the venom of a solitary wasp, facilitates transmission in the crustacean neuromuscular synapse.

A new neurotoxin, named alpha-pompilidotoxin (alpha-PMTX) has been found in the venom of the solitary wasp Anoplius safnariensis. In the neuromuscular synapse of the lobster walking leg preparation, alpha-PMTX (10-100 micro/M) caused great enhancement of both the excitatory and inhibitory postsynaptic potentials. Recordings of the excitatory post synaptic currents (EPSCs) at the synaptic sites showed that alpha-PMTX reversibly and dose-dependently potentiates EPSCs. Alpha-PMTX may act primarily on the presynaptic membrane but the mode of action of the toxin is clearly different from other known facilitatory neurotoxins, such as alpha-latrotoxin, apamin or charybdotoxin. This novel toxin will serve as a useful tool in the research field of neuroscience.

Animals↗
PubMed1997

Novel hepatitis C virus protease inhibitors: thiazolidine derivatives.

This study evaluated the inhibitory effects of thiazolidine derivatives on hepatitis C virus (HCV) protease and other human serine proteases. The inhibition efficacy was tested with a reversed-phase high-performance liquid chromatography (HPLC) assay system using a NS3-NS4A fusion protein as the HCV protease and a synthetic peptide substrate that mimics the NS5A-5B junction. Nine thiazolidine derivatives showed more than 50% inhibition at 50 microg/ml. The most potent derivative was RD4-6250, with 50% inhibition at a concentration of 2.3 microg/ml; this concentration was lower than those of other protease inhibitors reported previously. The most selective derivative was RD4-6205, with 50% inhibition at a concentration of 6.4 microg/ml, a lower concentration than those on other serine proteases (chymotrypsin, trypsin, plasmin, and elastase). These results suggest that the RD4-6205 skeleton is an important structure for inhibitory activity on the HCV protease NS3-NS4A.

Enzyme Inhibitors↗
PubMed1997

The pathway of ammonia assimilation in the silkworm, Bombyx mori.

Ammonia can easily be assimilated into amino acids and used for silk-protein synthesis in the silkworm, Bombyx mori. To determine the metabolic pathway of ammonia assimilation, silkworm larvae were injected with methionine sulfoximine (MS), a specific inhibitor of glutamine synthetase (GS). Activity of GS in the fat body 2h after treatment with 400&mgr;g MS decreased to less than 10% of the control activity, whereas MS had no effect on the activity of glutamate dehydrogenase (GDH), another enzyme which could possibly be responsible for ammonia assimilation. Glutamine concentration in the hemolymph rapidly decreased after MS treatment, while the ammonia level in the hemolymph sharply increased. Glutamine concentration in the hemolymph 4h after injection decreased with increasing doses of MS, whereas ammonia concentration increased in proportion to the MS dose. MS strongly blocked the incorporation of (15)N label into silk-protein in larvae injected with (15)N ammonia acetate, while it slightly inhibited the incorporation of (15)N-amide glutamine into silk-protein. These results suggest that ammonia is mainly assimilated into glutamine via the action of GS and then converted into other amino acids for silk-protein synthesis and that GDH does not play a major role in ammonia assimilation in B. mori.

Journal Article↗
PubMed1997

Histamine H2 receptor-mediated airway goblet cell secretion and its modulation by histamine-degrading enzymes.

BACKGROUND: Airway goblet cell hypersecretion may contribute to the pathophysiology of asthma. However, it is unknown whether histamine affects goblet cell secretion and, if so, which subtype of histamine receptor is involved and whether endogenous histamine-degrading enzymes modulate these actions. METHODS: We morphometrically assessed goblet cell secretion in the guinea pig trachea stained with alcian blue and periodic acid Schiff stains by measuring the mucus score, which was inversely related to the degree of mucus glycoprotein discharge. RESULTS: Inhalation of histamine caused a dose-dependent decrease in mucus score, an effect that was inhibited by pretreatment with the H2-receptor antagonist cimetidine but not with the H1-receptor antagonist mepyramine or the H3-receptor antagonist thioperamide. Inhaled Dimaprit, a selective H2-receptor agonist, likewise decreased mucus score; whereas stimulation of H1- and H3-receptors with 2-methylhistamine and (R)-alpha-methylhistamine, respectively, had no effect. Pretreatment with the histamine N-methyltransferase inhibitor SKF 91488, but not the diamine oxidase inhibitor aminoguanidine, potentiated the dose-dependent effect of histamine on goblet cell secretion, causing a decrease in the concentration of inhaled histamine required to produce a half-maximal effect from 0.80 +/- 0.12 to 0.48 +/- 0.09 mg/ml (p < 0.01). The histamine methyltransferase activity in the tracheal mucosa was 29 times higher than diamine oxidase activity. CONCLUSION: These findings suggest that histamine stimulates airway goblet cell secretion through H2-receptors and that this effect may be modulated principally by endogenous histamine methyltransferase through a degradation of histamine.

Amine Oxidase (Copper-Containing)↗
PubMed1997

Role of Ca(2+)-activated K+ channel in epithelium-dependent relaxation of human bronchial smooth muscle.

1. To elucidate whether K+ channels play a role in the action of epithelium-dependent bronchodilatation, we studied responses in human bronchial strips in the presence of indomethacin and NG-nitro-L-arginine methylester under isometric conditions, in vitro. 2. Mechanical removal of the epithelium increased the contractile responses to acetylcholine; the pD2 values increased from 5.0 +/- 0.2 to 5.9 +/- 0.3 (P < 0.001). This potentiation was abolished by iberiotoxin but not by apamin or glibenclamide. 3. In cascade bioassay, application of the bathing medium from dispersed, bronchial epithelial cells to epithelium-denuded bronchial strips decreased acetylcholine-induced contraction by 44 +/- 6%. This effect was reduced to 10 +/- 3% (P < 0.01) when the epithelial cells were pretreated with iberiotoxin, and to 4 +/- 1% (P < 0.001) when the epithelial cells were incubated with Ca(2+)-free medium containing [1,2-bis(2) aminophenoxy] ethane N,N,N',N'-tetraacetic acid-acetomethoxy ester. 4. In contrast, the bronchodilator effect of the medium bathing epithelial cells was not altered by the direct addition of iberiotoxin to epithelium-denuded tissues. 5. These results suggest that the Ca(2+)-activated K+ channel may play a role in the synthesis and/or release of smooth muscle relaxing factor, which is neither nitric oxide nor a cyclo-oxygenase product, from airway epithelial cells.

Acetylcholine↗
PubMed1997

Risk of cytomegalovirus infection after peripheral blood stem cell transplantation.

From 1992 to 1995, 105 patients received PBSCT in our hospitals and we observed no incidence of CMV-pneumonia. To clarify whether activation of CMV occurs in these patients shell vial cultures, CMV antigenemia and PCR (DNA-PCR and RT-PCR) were used as detection methods for CMV. Bronchoalveolar lavage (BAL) samples, MNC and PMN samples from peripheral blood leukocytes, and urine samples were taken from 17 patients on day 35 after PBSCT. CMV was detected in one urine specimen but not detected in any of the BAL, MNC or PMN specimens by shell vial culture. CMV antigenemia provided no positive data. Nine of the 74 samples taken from the 17 patients proved positive by DNA-PCR, but all CMV-mRNA results were negative by RT-PCR. We performed CMV antigenemia and PCR on MNC and PMN specimens from six patients every 1 to 2 weeks after transplantation to determine whether and when CMV was activated. Two patients tested positive transiently by DNA-PCR but negative throughout by both antigenemia and RT-PCR. These results suggest that the risk of CMV infection is low because the incidence of CMV activation in patients receiving PBSCT is low.

Adolescent↗
PubMed1997

Thiadiazole derivatives: highly potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) replications in vitro.

We have recently reported that thiadiazole (TDA) derivatives are highly potent inhibitors of human immunodeficiency virus type 1 (HIV-1) replication. These compounds belong to the family of nonnucleoside reverse transcriptase inhibitors (NNRTIs). In an attempt to develop more effective and pharmacologically favorable compounds, novel TDA derivatives have been synthesized and examined for their anti-HIV-1 activity in vitro. Among them, RD4-2217 was found to be the most potent inhibitor of HIV-1 replication. It inhibited replication of the HTLV-IIIB strain in MT-4 cells at a concentration of 6 nM. RD4-2217 was also inhibitory to clinical isolates and zidovudine-resistant mutants of HIV-1. The combination of RD4-2217 with zidovudine or the protease inhibitor A-75925 synergistically inhibited HIV-1 replication. Studies on the emergence of drug-resistant mutants revealed that, although much higher concentrations (1-10 microM) were required, RD4-2217 completely suppressed the breakthrough of HIV-1 in the supernatants during long-term culturing of infected cells. Furthermore, RD4-2217 at low concentrations (10 or 100 nM), in combination with zidovudine, also completely inhibited viral breakthrough. In addition, RD4-2217 had lower lipophilicity and improved protein binding as compared to its congener RD4-2024 and loviride. These results suggest that RD4-2217, one of the TDA derivatives, is worth pursuing as a candidate drug for the treatment of HIV-1 infections.

Anti-HIV Agents↗
PubMed1997

Effect of adenosine on adrenergic neurotransmission and modulation by endothelium in canine pulmonary artery.

To determine the effect of adenosine on adrenergic neurotransmission in pulmonary vasculature and its modulation by endothelial cells, we studied canine pulmonary arteries under isometric conditions in vitro. Adenosine decreased the contractile responses to electrical field stimulation but had no effect on those to norepinephrine. This inhibitory effect was concentration dependent, with a rank order of potency of NECA > 2-chloroadenosine > adenosine >> APNEA (an A3-adenosine-receptor agonist) > CGS-21680 (an A2a agonist) > CCPA (an A1 agonist). Adenosine reduced the electrical field stimulation-evoked 3H overflow in superfused pulmonary artery previously soaked in [3H]norepinephrine. Pretreatment with the adenosine uptake blocker dipyridamole or the adenosine deaminase inhibitor deoxycoformycin enhanced the adenosine action, and this enhancement was not observed in the endothelium-denuded tissues. Adenosine deaminase activity was found in endothelial cells. Therefore, adenosine inhibits norepinephrine release via an A2b-receptor mechanism, an effect that may be modulated by uptake and metabolism by endothelial cells.

Adenosine↗
PubMed1997

Lipopolysaccharide-induced goblet cell hypersecretion in the guinea pig trachea: inhibition by macrolides.

We studied the effects of macrolides on lipopolysaccharide (LPS)-induced airway goblet cell secretion in the guinea pig trachea. The goblet cell secretion was assessed in histological sections of the tracheal mucosa stained with alcian blue and periodic acid Schiff by arbitrarily determining mucus score, which is inversely related to the magnitude of mucus discharge. Inhalation of Escherichia coli LPS (5 mg/kg) caused a time-dependent decrease in mucus score, with the maximal response being from 542 +/- 49 to 92 +/- 20 arbitrary units (P < 0.001) after 3 h, which was accompanied by an increase in the number of neutrophils in the tracheal mucosa. The LPS-induced mucus discharge was inhibited by oral clarithromycin and erythromycin in a dose-dependent manner (5 and 10 mg/kg), whereas amoxicillin and cefaclor had no effect. Each dose of clarithromycin and erythromycin, but not amoxicillin or cefaclor, likewise attenuated the LPS-induced recruitment of neutrophils. These results suggest that LPS stimulates goblet cell secretion and neutrophil accumulation in the airways and that macrolides may be of value in protecting against neutrophil-associated airway hypersecretion.

Animals↗
PubMed1997

Invasive thymoma with CD4+CD8+ double-positive T cell lymphocytosis.

Lymphocytosis in the peripheral blood is a very rare manifestation of thymoma. A 45-year-old man presented with a giant mediastinal mass involving pleural dissemination and peripheral T cell lymphocytosis. Biopsy of the mediastinal mass revealed invasive thymoma, and two-color analysis of peripheral lymphocytes showed a marked increase in CD4+CD8+ double-positive cells. Both thymoma and lymphocytosis were improved by a combination of chemotherapy and mediastinal irradiation.

CD4 Antigens↗
PubMed1997

Leukotriene antagonist prevents exacerbation of asthma during reduction of high-dose inhaled corticosteroid. The Tokyo Joshi-Idai Asthma Research Group.

To test whether the leukotriene antagonist ONO-1078 (pranlukast) prevents asthma exacerbations during reduction of high-dose inhaled corticosteroid, we conducted a randomized, double-blind, placebo-controlled study in 79 asthma patients requiring high doses (1,500 microg/d or more) of inhaled beclomethasone dipropionate (BDI) for clinical control (duration of asthma, 11.0 +/- 3.1 yr; duration of BDI treatment, 0.5 +/- 0.3 yr; FEV1 percentage of predicted, 80.7 +/- 2.0%). After a 2-wk run-in period, the doses of BDI were halved, while the patients were assigned to receive orally ONO-1078, 450 mg twice daily, or placebo. In the placebo group FEV1 decreased by 0.33 +/- 0.20 L after 6 wk (p < 0.001). Likewise, morning and evening PEF decreased by 46 +/- 7 L/min and 18 +/- 6 L/min, respectively. By contrast these variables were sustained above baseline in the ONO-1078 group. The number of daytime and nighttime asthma symptoms and the use of beta2-agonist increased in the placebo group, whereas they remained unchanged in the ONO-1078 group. In the placebo group concentrations of serum eosinophil cationic protein and exhaled nitric oxide increased (p = 0.007 and p = 0.025, respectively), compared with no change in the ONO-1078 group. Therefore, the leukotriene antagonist ONO-1078 prevents the asthma deterioration provoked by a 6-wk reduction of the dose of inhaled BDI into half.

Administration, Inhalation↗
PubMed1997

Increased oxidative metabolism in cow tracheal epithelial cells cultured at air-liquid interface.

Airway epithelial cells cultured at the air-liquid interface possess highly differentiated functions and structures compared with the cells cultured under immersion. We examined the oxidative metabolism and glycolysis in cow tracheal epithelial cells on Days 3, 6, 10, and 13, cultured under three different conditions: (1) immersion culture on porous filters with apical and basolateral feeding (IM), (2) air-exposed culture on porous filters with basolateral feeding, i.e., air-liquid interface culture (AI), and (3) conventional immersion culture in plastic dishes with apical feeding (DI). Lactate production was less in AI than in IM and DI on Day 3 through Day 13, whereas cellular adenosine triphosphate content and basal O2 consumption were greater. Ouabain-sensitive and ouabain-insensitive O2 consumption, and the uncoupled O2 consumption were also greater in AI. Cytosolic lactate dehydrogenase activities on Day 10 were lower in AI, whereas alpha-ketoglutarate dehydrogenase activities were higher. The increased oxidative metabolism in AI was more pronounced at the late phase of culture (Days 10 and 13). In contrast, glycolysis remained elevated during the experiment in IM and DI. These data suggest that (I) AI begins to promote oxidative metabolism from growth phase by the provision of adequate oxygenation, and then further shifts to oxidative metabolism with differentiation; and (2) apical feeding may be responsible for the disturbance of the development of the oxidative metabolism.

Adenosine Triphosphate↗
PubMed1997

Synthesis and biological activity of a 1 alpha,25-dihydroxyvitamin D2 analog bearing an amide group in the side-chain.

Synthesis of a 1 alpha,25-dihydroxyvitamin D2 analog (3), in which the double bond in the side-chain is replaced by an amide group, is described. Condensation of a carboxylic acid (8) with an amine (6) gave an amide (9), which in turn led to 3 via several steps. The analog (3) could not bind to the chick cytosol vitamin D receptor, which indicated the importance of the hydrophobic interaction of the C(22)-C(23) double bond in 1 alpha,25-dihydroxyvitamin D2 (2) with the vitamin D receptor.

Ergocalciferols↗
PubMed1997

Isolated splenic metastases.

We analyzed the primary tumors, sonographic findings, clinical manifestations, and prognosis in five cases of isolated splenic metastases to determine in what situations these rare metastases should be suspected. The metastases were detected by ultrasonography in all five patients, and the primary tumors were colonic cancer in four patients and renal cancer in one patient. Splenectomy was performed and the postoperative course was uneventful in all patients. We conclude that preoperative and follow-up examinations must be performed with special attention given to the spleen in colonic or renal cancer patients.

Adult↗
PubMed1997

Temocaprilat, a novel angiotensin-converting enzyme inhibitor, is excreted in bile via an ATP-dependent active transporter (cMOAT) that is deficient in Eisai hyperbilirubinemic mutant rats (EHBR).

Temocapril x HCl (alpha-((2S,6R)-6-[(1S)-1-ethoxy-carbonyl-3-phenyl-propyl]amino-5-oxo-2- (2-thienyl)perhydro-1,4-thiazepin-4-yl)acetic acid hydrochloride) is a novel prodrug of an angiotensin-converting enzyme (ACE) inhibitor. Unlike many other ACE inhibitors, its pharmacologically active metabolite,temocaprilat, is excreted predominantly in bile. To investigate the mechanism for the biliary excretion of temocaprilat, we performed in vivo and in vitro experiments using mutant Eisai hyperbilirubinemic rats EHBR) whose canalicular multispecific organic anion transporter (cMOAT) is hereditarily defective. Biliary clearance of temocaprilat after i.v. administration of [14C]temocapril x HCl (1.0 mg/kg) in EHBR was significantly lower than that in Sprague-Dawley rats (5.00 ml/min/kg for Sprague-Dawley rats vs. 0.25 ml/min/kg for EHBR). The uptake of temocaprilat into canalicular membrane vesicles (CMVs) prepared from Sprague-Dawley rats was stimulated in the presence of ATP, whereas little stimulation was observed in CMVs from EHBR. The initial uptake rate of ATP-dependent transport of temocaprilat showed saturation kinetics; we obtained an apparent V(max) value of 1.14 nmol/min/mg protein and a K(m) value 92.5 microM. ATP-dependent transport of temocaprilat was competitively inhibited by 2,4-dinitrophenyl-S-glutathione, a typical substrate for cMOAT with an inhibition constant (K(i)) of 25.8 microM. The K(m) value for the uptake of 2,4-dinitrophenyl-S-glutathione into CMVs (K(m) = 29.6 microM) was consistent with this K(i) value. In addition, the ATP-dependent uptake of 2,4-dinitrophenyl-S-glutathione was inhibited by temocaprilat in a concentration-dependent manner. Active forms of some ACE inhibitors (benazepril, cilazapril, delapril, enalapril and imidapril) did not affect the transport of temocaprilat into CMVs even at concentrations as high as 200 microM. These data suggest that temocaprilat is effectively excreted in bile via cMOAT that is deficient in EHBR and that many of other ACE inhibitors have low affinity for cMOAT.

Adenosine Triphosphate↗
PubMed1997

[Effect of heparin on the increase in intracellular calcium caused by inositol 1,4,5-triphosphate in airway epithelial cells].

We studied the effect of heparin on the inositol 1,4,5-triphosphate (IP3)-dependent increase in intracellular calcium (Ca2+) caused by ATP. The Ca2+ concentration ([Ca2+]i) in cultured epithelial cells from cow tracheas was measured by the fura-2 method. ATP (10(-4) M) stimulated IP3 production and caused a biphasic increase in [Ca2+]i a transient response and a subsequent sustained response. Heparin (l 100 U/ml) dose-dependently inhibited the ATP-induced increase in [Ca2+]i but had no effect on IP3 production. Dextran sulfate, a polysaccharide with negative charge density, had a similar inhibitory effect on the ATP-induced increase in [Ca2+]i. These data suggest that heparin inhibits intracellular Ca2+ mobilization by acting at a site "distal to" IP3 production, and that the mechanism of action of heparin may be related to its negative charge.

Adenosine Triphosphate↗
PubMed1997

Stimulation of airway mucociliary transport and epithelial ciliary motility by the triazolopyridazin derivative TAK-225.

To elucidate whether a newly developed antiallergic drug, the triazolopyridazin derivative TAK-225, alters airway mucociliary clearance and, if so, what the mechanism of action is, we measured mucociliary transport in the rabbit tracheal mucosa ex vivo and ciliary motility of the tracheal epithelium in vitro. Mucociliary transport function was determined by the transport rate of Evans blue dye that had been placed on the mucosal surface above the carina. Oral administration of TAK-225 (0.3-30 mg/kg) increased Evans blue transport toward the larynx in a dose-dependent manner. Addition of TAK-225 caused a rapid and sustained increase in the ciliary beat frequency of tracheal epithelium, as assessed by photoelectric method; the maximal increase from the base-line value was 25.1 +/- 4.6% (P < .01), and the concentration required to produce a half-maximal effect (EC50) was 3.1 +/- 0.8 x 10(-7) M. This effect was greatly attenuated by pretreatment with the cAMP antagonist adenosine 3',5'-cyclic monophosphorothioate, but not by Ca++-free medium containing ethylene glycol-bis [3-aminoethyl ether] N,N,N',N'-tetraacetic acid and [1,2-bis(2)aminophenoxy]ethane N,N,N',N'-tetraacetic acid-acetomethoxy ester. Incubation of tracheal epithelium with TAK-225 increased intracellular cAMP contents in a concentration-dependent manner. These results suggest that TAK-225 enhances airway mucociliary clearance probably through cAMP-mediated stimulation of ciliary motility of airway epithelium.

Animals↗