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Biomedical subjects

K Konno

Publications and source records attributed to K Konno.

At least 109 records · Page 6Linked to original sources
PubMed1997

5-Hydroxytryptamine inhibits Na absorption and stimulates Cl secretion across canine tracheal epithelial sheets.

BACKGROUND: 5-Hydroxytryptamine (5-HT) can be released from mast cells and platelets through an IgE-dependent mechanism and may play a role in the pathogenesis of allergic bronchoconstriction. However, the effect of 5-HT on ion transport by airway epithelium remains uncertain. OBJECTIVE: To determine whether 5-HT alters electrical and ion transport properties of Cl-secreting epithelia and, if so, what subtype of 5-HT receptors is involved, we studied canine tracheal epithelium under short-circuit conditions in vitro. METHODS: Canine tracheal mucosa was mounted in Lucite half-chambers and the responses of short-circuit current (lsc), transepithelial potential difference (PD) and tissue conductance (G) were measured. In addition, ion fluxes were directly measured using 22Na and 36Cl. RESULTS: Mucosal addition of 5-HT caused a rapid increase in lsc, which was accompanied by the increases in PD and G, whereas submucosal 5-HT had no effect. In the presence of amiloride, 5-HT and its receptor agonists dose-dependently increased lsc, with the rank order of potency being 5-HT > alpha-methyl-5-HT > 2-methyl-5HT > 5-carboxamidotryptamine. The effect of 5-HT was inhibited by ketanserin and spiperone but not by ondansetron. 5-HT increased Cl flux from the submucosa to the mucosa with a slight inhibition of Na flux to the opposite direction. CONCLUSION: 5-HT inhibits airway epithelial Na absorption and stimulates Cl secretion. The latter action predominates the former and is mediated by 5-HT2 receptors. These effects may result in the increase in water movement toward the airway lumen.

Amiloride↗
PubMed1997

Effect of ultraviolet radiation on the infectivity of Taenia taeniaeformis eggs.

The effect of ultraviolet (UV) radiation on the infectivity of Taenia taeniaeformis eggs was observed. The eggs were exposed to various UV doses and orally inoculated to rats. The number of cysts and lesions decreased dose-dependently, and neither cyst nor lesion was observed from rats infected with eggs exposed to a total dose of 2,880 mJ/cm2 or more. For evaluation of protective role of embryophore against UV radiation, the onchospheres with/without embryophore were exposed to UV radiation. Remarkably lower numbers of cyst and lesions were observed in rats inoculated with eggs which were exposed to a total dose of 30 mJ/cm2 or more after removal of embryophore. These results suggested an importance of the protective function of the embryophore in the protection against UV radiation.

Animals↗
PubMed1997

[Pharmacokinetic studies of all-trans retinoic acid (ATRA) and pilot study of intermittent schedule of ATRA and chemotherapy in childhood acute promyelocytic leukemia. Children's Cancer and Leukemia Study Group].

A pharmacokinetic study of all-trans retinoic acid (ATRA) was performed in 8 patients with various types of leukemia and MDS. After oral administration at a dose of 30 mg/m2, the mean peak plasma concentration was 430 ng/ml and was reached at 150 min. In one patient who failed to respond a very low plasma ATRA level was seen. Though the plasma ATRA exposure decreased significantly with daily drug administration, an intermittent schedule of ATRA administration would yield higher plasma drug concentrations. We treated 2 patients with refractory acute promyelocytic leukemia (APL) in a pilot study of ATRA followed by intensive chemotherapy (APL-ATRA protocol). Two patients successfully achieved complete remission with ATRA after failing under conventional chemotherapy. Based on the pharmacokinetic study of ATRA, an intermittent schedule of ATRA in addition to chemotherapy suggests an effective regimen for children with APL. Phase II trials to evaluate the role of intermittent schedules of ATRA are planned in Children's Cancer and Leukemia Study Group.

Administration, Oral↗
PubMed1996

Establishment of an in vitro assay system for screening hepatitis C virus protease inhibitors using high performance liquid chromatography.

The hepatitis C virus (HCV) genome contains the code for a conserved, serine-type protease, called NS3, for the processing of the non-structural protein region of the viral polyproteins. Furthermore, a related protein, NS4A, is an effector or cofactor of NS3 protease activity in the cleavage of NS3-4A, NS4A-4B, NS4B-5A and NS5A-5B junctions. To establish an in vitro assay system for the screening of those enzyme inhibitors that inhibit the protease NS3-4A, we prepared a maltose-binding protein-NS3-NS4A fusion protein and a synthetic peptide substrate that mimics the NS5A-5B junction. Cleavage of the synthetic peptide was analyzed by reversed-phase high performance liquid chromatography (HPLC). We showed that the enzymatic activity of the NS3-NS4A fusion protein was enhanced in comparison to the NS3 protein alone. The assay conditions for optimum NS3-4A protease activity were determined to be pH 7.6 and 37 degrees C. In addition, we evaluated several protease inhibitors using the same HPLC assay system. The activity of HCV protease NS3-4A was inhibited by 2714.4 microM diisopropyl fluorophosphate, 270.8 microM N-tosyl-L-lysyl chloromethyl ketone, and 825.5 microM chymostatin. The results of the present study indicated that the synthetic peptide substrate and HPLC assay system are suitable for studying HCV protease activity and may facilitate the development of anti-HCV therapeutic reagents.

Amino Acid Sequence↗
PubMed1996

Antiviral activities of nucleotide heterodimers against human immunodeficiency virus type 1 in vitro.

Nucleotide heterodimers were synthesized and examined for their inhibitory effects on the replication of human immunodeficiency virus type 1 (HIV-1), including HIV-1 reverse transcriptase (RT) inhibitor-resistant mutants. 3'-Azido-3'-deoxythymidilyl-(5')-phospho-(5')-6-[(3', 5'-dimethylphenyl)thio]-5-ethyl-1-[(2-hydroxyethoxy)methyl]uracil (AZT-P-E-HEPU-dM) and 3'-azido-3'-deoxythymidilyl-(5')-phospho-(5')-2', 3'-dideoxyinosine (AZT-P-ddI) proved to be highly potent and selective inhibitors of HIV-1 (IIIB strain) in MT-4 cells. The mechanism of inhibition by these heterodimers may be attributed to their degradation and the formation of each constituent. AZT-P-E-HEPU-dM was also markedly inhibitory to an AZT-resistant mutant (HIV-1-IIIB/AZT) and an E-HEPU-dM-resistant mutant (HIV-1-IIIB-R). However, AZT-P-ddI was found to have a less inhibitory effect on HIV-1-IIIB/AZT than on HIV-1-IIIB. The heterodimers of (5',5') AZT and ribavirin (AZT-P-Ribavirin) and (5',5') ddI and ribavirin (ddI-P-Ribavirin) were also synthesized: AZT-P-Ribavirin inhibited HIV-1 replication, but ddI-P-Ribarvirin did not.

Anti-HIV Agents↗
PubMed1996

Anti-HIV-1 activity of thiadiazole derivatives: structure-activity relationship, reverse transcriptase inhibition, and lipophilicity.

The structure-activity relationship of the non-nucleoside HIV-1-specific reverse transcriptase (RT) inhibitors 4-phenyl-1,2,5-thiadiazol-3-yl N,N-dialkylcarbamate (TDA) derivatives was investigated with respect to their anti-HIV-1 activity, RT inhibition, and lipophilicity. 4-Phenyl-1,2,5-thiadiazol-3-yl N,N-dimethylcarbamate inhibited HIV-1-induced cytopathic effect (CPE) by 50% at a concentration of 28.8 microM in MT-4 cells. The activity increased more than 100-fold when the hydrogens at the 2-position and the 6-position in phenyl moiety were substituted by chlorines. However, the derivative with a chlorine at the 4-position of phenyl moiety did not show any inhibition of HIV-1 replication at its non-toxic concentrations. All of the 4-(2,6-dichlorophenyl)-1,2,5-thiadiazol-3-yl N-methyl-N-alkylcarbamates proved inhibitory to HIV-1 replication in the nanomolar concentration range. The TDA derivatives that showed anti-HIV-1 activity also inhibited RT activity in an enzymatic assay. However, the TDA derivatives did not show any specific inhibition of a non-nucleoside RT inhibitor (NNRTI)-resistant mutant and its RT activity. When the TDA derivatives were examined for their inhibitory effect on HIV-1 replication in the presence of 50% human serum, the activity significantly decreased depending on-their lipophilicity.

Anti-HIV Agents↗
PubMed1996

Nicotine prolongs neutrophil survival by suppressing apoptosis.

Neutrophil accumulation in the lung is implicated in the pathogenesis of pulmonary emphysema and chronic bronchitis associated with cigarette smoking. To determine whether nicotine contributes to this accumulation through the prolongation of neutrophil survival, we examined the survival rates of isolated neutrophils cultured with or without nicotine. We found that nicotine prolonged neutrophil survival in a dose-dependent fashion, with a maximum effect at 10(-6) mol/L. The survival rate at 72 hours was 35.6% +/- 1.2% in medium with 10(-6) mol/L nicotine, compared with 15.5% +/- 0.5% in control medium (mean +/- SEM; p < 0.01), as determined by trypan blue dye exclusion. This prolongation was brought about by suppression of apoptosis, as evidenced by both transmission electron and fluorescence microscopy, and was associated with the preservation of neutrophil functions such as chemotaxis and O2- generation. The prolongation of survival caused by nicotine was abrogated by the addition of Pro-Lys-Arg-NH2, a competitive inhibitor of the specific binding of nicotine to noncholinergic receptors on neutrophils. However, the prolongation of survival caused by nicotine was not suppressed in the presence of K-252b, an inhibitor of protein kinase C. These findings suggest that nicotine prolongs neutrophil survival through noncholinergic nicotine receptors and new protein synthesis, without activation of protein kinase C.

Analysis of Variance↗
PubMed1996

Inhibitory effect of 4-(2, 6-dichlorophenyl)-1, 2, 5-thiadiazol-3-yl-N-methyl, N-ethylcarbamate on replication of human immunodeficiency virus type 1 and the mechanism of action.

In the search for effective antiviral agents, we have found 4-(2, 6-dichlorophenyl)-1, 2, 5-thiadiazol-3-yl-N-methyl, N-ethylcarbamate (RD4-2025) to be a highly potent and selective inhibitor of human immunodeficiency virus type 1 (HIV-1) in vitro. The 50% effective concentration of RD4-2025 for HIV-1-induced cytopathic effect in MT-4 cells was 37 nM, yet no antiviral activity was observed against HIV-2. In HIV-1 reverse transcriptase (RT) assays, RD4-2025 inhibited both RNA-dependent and DNA-dependent DNA polymerase activities of a recombinant HIV-1 RT with 50% inhibitory concentrations of 0.11 and 3.5 microM, respectively. However, the compound did not affect the activity of human DNA polymerase alpha. Kinetic studies revealed that the inhibition was noncompetitive with respect to dGTP as the substrate and poly(C)/(dG) 12-18 as the template/primer. These results were in accordance with those of nonnucleoside RT inhibitors (NNRTIs), such as R89439 (an alpha-anilinophenylacetamide derivative) and nevirapine, indicating that RD4-2025 also belongs to the family of NNRTIs.

Carbamates↗
PubMed1996

Effect of ciprofloxacin on ciliary motility of rabbit airway epithelium.

To determine the effect of the new quinolone ciprofloxacin on airway ciliary motility, we studied ciliary beat frequency (CBF) of rabbit tracheal epithelium using an in-vitro microphoto-oscillation method. Incubation of the cells with ciprofloxacin increased CBF in a concentration-dependent manner, the maximal increase from the baseline value and the EC50 being 17.1 +/- 2.0% (P < 0.01) and 10(-7.25) M, respectively. This ciliary stimulatory effect was not affected by propranolol or indomethacin but was nullified by verapamil. These results suggest that ciprofloxacin probably increases airway epithelial ciliary motility by facilitating Ca2+ influx through a voltage-dependent channel.

Animals↗
PubMed1996

Different properties of wild type and drug-resistant mutants of human immunodeficiency virus type 1 reverse transcriptase in vitro.

Drug-resistant mutants of human immunodeficiency virus type 1 (HIV-1) emerge during treatment with various reverse transcriptase (RT) inhibitors in vitro and in vivo. However, the virological nature and pathogenic importance of these mutants have not been fully elucidated. In this study, we have examined HIV-1 mutants resistant to 3'-azido-3'-deoxythymidine (AZT) and nonnucleoside RT inhibitors (NNRTIs) for their infectivity, RT activity, and replication in MT-4 cells. Although the infectivity of AZT- and NNRTI-resistant mutants was similar, the RT activity of AZT-resistant mutants was much higher than that of NNRTI-resistant mutants and their wild types. Furthermore, the RT activity of NNRTI-resistant mutants was significantly lower than that of the wild types. In contrast, the replication of NNRTI-resistant mutants was found to be greater than that of AZT-resistant mutants and the wild types. When HIV-1 proviral DNA (cDNA) synthesis was examined by PCR in MT-4 cells infected with the wild type, AZT-resistant mutant, or NNRTI-resistant mutant, the PCR signal of the NNRTI-resistant mutant was found to be much higher than those of the wild type and AZT-resistant mutant. These results suggest that the drug-resistant mutants differ from their corresponding wild types not only in drug sensitivity but also in other virological properties.

Antiviral Agents↗
PubMed1996

Colorimetric assay system for screening antiviral compounds against hepatitis B virus.

A highly sensitive, rapid, and accurate assay system was developed for the in vitro evaluation of anti-hepatitis B virus (anti-HBV) agents. Chronic HBV-producing HB611 cells were used in combination with immunoaffinity purification, polymerase chain reaction (PCR), and hybrid capture detection. HB611 cells were incubated with putative anti-HBV agents for 7 days in 96-well microtiter plates. HBV was purified from HB611 cell culture media using immunoaffinity purification. The HBV DNA was extracted, amplified with PCR, and assayed using a hybrid capture colorimetric method. This assay provided quantitative detection of extracellular HBV DNA from 25 microliters of cell culture media. Using the colorimetric method, we found that 50% effective concentration levels of several known anti-HBV agents (HPMPA, PMEDAP, PMEA and others) were similar to those reported in studies using Southern blot analysis. These results demonstrate that this new and easily automated colorimetric assay system can be used for the rapid and accurate assessment of anti-HBV compound selectivity.

Adenine↗
PubMed1996

[Effect of macrolide antibiotics on airway goblet hypersecretion in guinea pigs].

Although macrolide antibiotics have now been widely used in the treatment of chronic airway infections including diffuse panbronchiolitis and chronic bronchitis, the mechanism of the efficacy remains uncertain. Because the increased mucus glycoprotein secretion from airway goblet cells may play a significant role in the development of such diseases, to determine the effects of macrolides on airway goblet cell secretion, we studied guinea pig airways by a semiquantitative morphometric method. The goblet cell secretion was assessed in histological sections of the trachea and main bronchi stained with Alcian blue and PAS by determining mucus score, which is inversely related to the magnitude of mucus discharge. Intravenous IL-8 decreased mucus score in a dose-dependent manner and increased the number of neutrophils present in bronchoalveolar lavage fluid. Oral administration of clarithromycin at a daily dose of 1-10 mg/day for 2 weeks dose-dependently inhibited IL-8 (5 mg/ kg)-induced decrease in mucus score, with the maximal inhibition being 54 +/- 11% (p < 0.001) in the trachea and 48 +/- 8% (p < 0.01) in the main bronchi. This effect was accompanied by the inhibition of neutrophil accumulation into bronchoalveolar lavage fluid. Erythromycin produced similar inhibitory effects on IL-8-induced goblet cell secretion and neutrophil accumulation, whereas amoxicillin and cefaclor had no effect. These results suggest that macrolides protect against goblet cell hypersecretion probably through an inhibition of recruitment of neutrophils into the airway mucosa.

Animals↗
PubMed1996

Mechanism of selective inhibition of human immunodeficiency virus by ingenol triacetate.

Ingenol 3,5,20-triacetate (ITA), one of the ingenol derivatives, is a selective inhibitor of human immunodeficiency virus (HIV) replication in vitro. ITA inhibited the replication of HIV strains in MT-4 cells at concentrations of 0.051 to 0.65 microM. This concentration was approximately 10(3)-fold lower than its cytotoxic threshold. The mechanism of action of ITA is primarily attributed to the inhibition of viral adsorption to the host cells, but it is distinct from the mechanism of inhibition by other adsorption inhibitors.

Antiviral Agents↗
PubMed1996

Effects of roxithromycin and erythromycin on interleukin 8-induced neutrophil recruitment and goblet cell secretion in guinea pig tracheas.

Inhaled interleukin 8 caused an increase in goblet cell secretion in guinea pig tracheas, which was accompanied by mucosal infiltration of neutrophils. These responses were inhibited by pretreatment with roxithromycin or erythromycin in a dose-dependent fashion. Macrolides may thus be a value in protecting against neutrophil-associated airway hypersecretion.

Animals↗
PubMed1996

Hypoxia impairs nitrovasodilator-induced pulmonary vasodilation: role of Na-K-ATPase activity.

To elucidate the effect of hypoxia on nitrovasodilator-induced pulmonary vasodilation, we studied canine pulmonary arterial rings under isometric conditions in vitro. Exposure to hypoxia inhibited the relaxant responses of KCl-contracted tissues to sodium nitroprusside (SNP), so that the maximal relaxation (Emax) and the negative logarithm of molar concentration required to produce 50% relaxation (pD2) were decreased from 92 +/- 7 to 62 +/- 5% and from 5.8 +/- 0.2 to 4.7 +/- 0.3, respectively (means +/- SE, P < 0.01 for each). This effect was likewise observed when 8-bromoguanosine-3',5'-cyclic monophosphate was used as a relaxant. The impairment of SNP-induced relaxation of endothelium-denuded rings under hypoxia was abolished by ouabain or K(+)-free solution. Incubation with SNPincreased intracellular cGMP contents in a dose dependent manner, an effect that was not altered by hypoxia. SNP also increased ouabain-sensitive 86Rb uptake, and this effect was inhibited by hypoxia. These results suggest that hypoxia reduces nitrovasodilator-induced relaxation of pulmonary artery, probably through an inhibition of cGMP-dependent sarcolemmal Na-K-adenosine triphosphatase activity.

Animals↗
PubMed1996

Alveolar destruction in guinea pigs chronically exposed to diesel engine exhaust. A light- and electron-microscopic morphometry study.

Guinea pigs were exposed 16 h a day, 6 d a week, for 6, 12, 18, or 24 mo to filtered air or diesel-exhaust at low (NO2 = 0.22 +/- 0.03 ppm; SO2 = 0.60 +/- 0.19 ppm; particles = 0.21 +/- 0.07 mg/m3), medium (NO2 = 1.07 +/- 0.09; SO2 = 2.83 +/- 0.73; particles = 1.14 +/- 0.26) or high (NO2 = 2.88 +/- 0.29; SO2 = 6.49 +/- 1.75; particles = 2.94 +/- 0.69) concentrations, or at a medium concentration without particles (NO2 = 1.01 +/- 0.09; SO2 = 2.66 +/- 0.64; particles = 0.01 +/- 0.01). We quantitated the holes in the alveolar wall and alveolar size by using scanning electron microscopy (SEM). After 12 mo of exposure, the ratio of the area of alveolar holes to that of the alveolar wall, and the number of holes per alveolus, rose as the concentration and duration of exposure increased. There were no differences in alveolar size between the study groups. Animals exposed to the medium concentration of diesel exhaust without particles showed less of an increase in the development of holes than animals exposed to the same concentration of diesel exhaust with particles. These findings suggest that diesel exhaust causes alveolar destruction (alveolar holes) without an enlargement in alveolar size in a concentration- and duration-dependent manner. Particulate matter in diesel exhaust may play some role in the development of these lesions.

Animals↗
PubMed1996

Effect of oxitropium bromide on histamine-induced airway goblet cell secretion.

To determine whether histamine affects airway goblet cell secretion and, if so, whether cholinergic mechanism is involved, we studied guinea pig airways by a semiquantitative morphometric method. The goblet cell secretion was assessed in histologic sections of the tracheal mucosa stained with Alcian blue and periodic acid-Schiff (PAS) by determining the mucus score, which is inversely related to the magnitude of mucus discharge. Inhaled or intravenously administrated histamine dose dependently decreased the mucus score, an effect that was similarly observed in cartilaginous and muscular portions. Inhalation of the anticholinergic agent oxitropium bromide at doses of 1.5 micrograms and higher greatly attenuated the decrease in mucus score produced by intravenous histamine but not by inhaled histamine. Likewise, cutting of bilateral vagus nerves or atropine abolished intravenous histamine-induced goblet cell secretion. The response of the mucus score to inhaled histamine was abolished by cimetidine, whereas the response to intravenous histamine was reduced by mepyramine but not by cimetidine or thioperamide. These results suggest that inhaled histamine increases airway goblet secretion, probably by stimulating histamine H2-receptors on goblet cells, and that intravenous histamine produces a similar effect through a stimulation of histamine H1-receptor-mediated release of acetylcholine from cholinergic nerve terminals, presumably involving vagal reflex.

Administration, Inhalation↗