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Sample records for beta-aminoethyl isothiourea

  1. Gas-phase lithium cation basicity of histamine and its agonist 2-([beta]-aminoethyl)-pyridine

    Science.gov (United States)

    Hallmann, M.; Raczynska, E. D.; Gal, J. F.; Maria, P. C.

    2007-11-01

    The gas-phase lithium cation basicities (LCBs) were obtained for histamine (HA) and its agonist 2-([beta]-aminoethyl)-pyridine (AEP) from collision-induced dissociation of lithium adducts using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). For measurements, MeO(CH2)2OMe, Et3PO and (Me2N)3PO (HMPA) were used as the reference compounds. The experimental LCB of AEP was located between those of Et3PO and (Me2N)3PO. The experimental LCB of HA was found to be higher than those of AEP and HMPA by more than 2 kcal mol-1 clearly indicating that the LCB of HA is higher than any LCB for a neutral base yet measured (crown-ethers excepted). The experimental LCBs of the parent bases (pyridine and imidazole) are lower by more than 10 kcal mol-1. In parallel, DFT calculations {B3LYP/6-31G*//B3LYP/6-31G* and B3LYP/6-311+G**//B3LYP/6-31G*} were performed for HA, AEP and their lithium adducts. Among the 22 reasonable conformations of the HA-Li+ adduct, only one appears to be significantly more stable than the others. This is also the case for one structure among seven conformations of the AEP-Li+ adduct. These two stable structures have the [`]scorpion' conformation, in which the Li+ cation is almost equally chelated by two basic nitrogen atoms, the ring N-aza and the chain N-amino. Other HA-Li+ and AEP-Li+ conformations have noticeably higher energies than the [`]scorpion' structures. The difference between the DFT calculated LCBs of HA and AEP (about 4 kcal mol-1) is in agreement with that experimentally obtained (>2 kcal mol-1). The high experimental and theoretical values of LCB for HA and AEP militate in favor of a strong chelation of Li+ by both ligands in the gas-phase. This chelation effect was also evidenced previously for the proton gas-phase basicity.

  2. Isothiourea-catalysed enantioselective pyrrolizine synthesis: synthetic and computational studies.

    Science.gov (United States)

    Stark, Daniel G; Williamson, Patrick; Gayner, Emma R; Musolino, Stefania F; Kerr, Ryan W F; Taylor, James E; Slawin, Alexandra M Z; O'Riordan, Timothy J C; Macgregor, Stuart A; Smith, Andrew D

    2016-10-14

    The catalytic enantioselective synthesis of a range of cis-pyrrolizine carboxylate derivatives with outstanding stereocontrol (14 examples, >95 : 5 dr, >98 : 2 er) through an isothiourea-catalyzed intramolecular Michael addition-lactonisation and ring-opening approach from the corresponding enone acid is reported. An optimised and straightforward three-step synthetic route to the enone acid starting materials from readily available pyrrole-2-carboxaldehydes is delineated, with benzotetramisole (5 mol%) proving the optimal catalyst for the enantioselective process. Ring-opening of the pyrrolizine dihydropyranone products with either MeOH or a range of amines leads to the desired products in excellent yield and enantioselectivity. Computation has been used to probe the factors leading to high stereocontrol, with the formation of the observed cis-steroisomer predicted to be kinetically and thermodynamically favoured.

  3. Strategy for designing selective α-l-rhamnosidase inhibitors: Synthesis and biological evaluation of l-DMDP cyclic isothioureas.

    Science.gov (United States)

    Miyawaki, Shota; Hirokami, Yuki; Kinami, Kyoko; Hoshino, Masako; Minehira, Daisuke; Miyamoto, Daiki; Nash, Robert J; Fleet, George W J; Adachi, Isao; Toyooka, Naoki; Kato, Atsushi

    2017-01-01

    This study shows that the cyclization of l-DMDP thioureas to bicyclic l-DMDP isothioureas improved α-l-rhamnosidase inhibition which was further enhanced by increasing the length of the alkyl chain. The addition of a long alkyl chain, such as decyl or dodecyl, to the nitrogen led to the production of highly potent inhibitors of α-l-rhamnosidase; it also caused broad inhibition spectrum against β-glucosidase and β-galactosidase. In contrast, the corresponding N-benzyl-l-DMDP cyclic isothioureas display selective inhibition of α-l-rhamnosidase; 3',4'-dichlorobenzyl-l-DMDP cyclic isothiourea (3r) was found to display the most potent and selective inhibition of α-l-rhamnosidase, with IC50 value of 0.22μM, about 46-fold better than the positive control 5-epi-deoxyrhamnojirimycin (5-epi-DRJ; IC50=10μM) and occupied the active-site of this enzyme (Ki=0.11μM). Bicyclic isothioureas of ido-l-DMDP did not inhibit α-l-rhamnosidase. These new mimics of l-rhamnose may affect other enzymes associated with the biochemistry of rhamnose including enzymes involved in progression of tuberculosis.

  4. Vasoactive and radioprotective properties of isothiourea derivatives having NOS-inhibitory activity

    Energy Technology Data Exchange (ETDEWEB)

    Filimonova, Marina V.; Shevchenko, Ludmila I.; Ulyanenko, Stepan E.; Makarchuk, Victorya M.; Kuznetsova, Mary N.; Shevchuk, Aza S.; Lushnikova, Galina A.; Chesnakova, Ekaterina A. [Medical Radiological Research Center Health Ministry of Russia, 4, Korolev street, Obninsk, 249036, Kaluga region (Russian Federation)

    2014-07-01

    We studied vasoactive and radioprotective properties of new original N-acyl, S-alkyl isothiourea derivatives which are potent inhibitors of nitric oxide synthases (preferably eNOS and iNOS). These compounds have a moderate toxicity (LD50 - 400-550 mg/kg), and are stable in aqueous solutions. In hemodynamic studies, these compounds exhibited high vasotropic activity. The use of these compounds in doses of 5-15 mg/kg (0,01-0,03 LD{sub 50}) in the experimental animals in a state of the severe hemorrhagic or endo-toxic shock causes a potent vasopressor effect, accompanied by a significant and continuous rise in blood pressure. The increasing of vascular tone developed over 2-5 min after injection and persisted for at least 60-90 minutes, excelling at least 3-5 times the duration of α1-adreno-mimetic vasopressor action. The rapid increase in vascular tone under the influence of these compounds in normo-tonic animals caused protective baroreflex to prevent high blood pressure. At doses of 10-15 mg/kg the reflex reaction was mild, but at higher doses (30-40 mg/kg) the reaction was fierce and prolonged, and was accompanied by severe bradycardia, decreasing of the cardiac output and a significant weakening of the peripheral blood flow. In all cases, the hemodynamic response was reflexive and easily eliminated by atropine. The ability of these compounds to induce circulatory hypoxia was the basis for the study of their radioprotective properties. The study of radioprotective effect on the survival of animals exposed to lethal doses of γ-radiation (10 Gy) and on the survival of hematopoietic clonogenic cells showed that these compounds in doses of 80-150 mg/kg (0,2-0,3 LD50) have considerable radioprotective action, which is comparable with the protective effect of the maximum tolerated dose of cystamine. The factor of change in dose for γ-radiation, estimated by the LD{sub 50}, was 1,42-1,58. We also investigated the ability of the test compounds, due to their hypoxic

  5. [Hypertensive action of 5-(beta-aminoethyl)aminoisoxazoles: synthesis and screening of isoxazolopyrazines and isoxazolodiazepines].

    Science.gov (United States)

    Dannhardt, G; Dominiak, P; Laufer, S

    1991-03-01

    The 5-aminoisoxazole 1 is converted via the 4-nitro derivative to the 4,5-diamino compound 4, which cyclises with glyoxal to yield the isoxazolo[4,5-b)pyrazine 5. Decomposition of the isoxazole moiety is always observed in experiments to hydrogenate partially the pyrazine ring and to phenylate the N-atom, respectively. Therefore, the corresponding tetrahydro derivative 6 is prepared from 4 and 1,2-ethandiol ditosylate. Starting with benzohydroxamic acid chloride and a cyanoacetic acid amide the tetrahydro isoxazolo[5,4-e]1,4-diazepinone-4 18 is synthesized. All new compounds are characterized by their spectroscopic data, the reaction mechanisms are discussed. Using the model of the pithed and the anaesthetized rat, resp., the pyrazino- and diazepino-isoxazoles (compounds 5, 6, 13, 18) have less or no hypertensive activity as compared to the corresponding derivatives with fully flexible side chains.

  6. Isothiourea-catalysed enantioselective pyrrolizine synthesis: synthetic and computational studies† †Electronic supplementary information (ESI) available: NMR spectra, HPLC analysis and computational co-ordinates. Data available.12 CCDC 1483759. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6ob01557c Click here for additional data file. Click here for additional data file. Click here for additional data file.

    Science.gov (United States)

    Stark, Daniel G.; Williamson, Patrick; Gayner, Emma R.; Musolino, Stefania F.; Kerr, Ryan W. F.; Taylor, James E.; Slawin, Alexandra M. Z.; O'Riordan, Timothy J. C.

    2016-01-01

    The catalytic enantioselective synthesis of a range of cis-pyrrolizine carboxylate derivatives with outstanding stereocontrol (14 examples, >95 : 5 dr, >98 : 2 er) through an isothiourea-catalyzed intramolecular Michael addition-lactonisation and ring-opening approach from the corresponding enone acid is reported. An optimised and straightforward three-step synthetic route to the enone acid starting materials from readily available pyrrole-2-carboxaldehydes is delineated, with benzotetramisole (5 mol%) proving the optimal catalyst for the enantioselective process. Ring-opening of the pyrrolizine dihydropyranone products with either MeOH or a range of amines leads to the desired products in excellent yield and enantioselectivity. Computation has been used to probe the factors leading to high stereocontrol, with the formation of the observed cis-steroisomer predicted to be kinetically and thermodynamically favoured. PMID:27489030

  7. Renin release from permeabilized juxtaglomerular cells is stimulated by chloride but not by low calcium

    DEFF Research Database (Denmark)

    Jensen, B L; Skøtt, O

    1994-01-01

    technique, superfused, and permeabilized by 20 microM digitonin for 12 min. The calcium concentration was varied with Ca ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) buffers [0 (5 MM EGTA without calcium), 17, 73, 170, 440, or 700 nM and 1.5, 15 or 150 micro...

  8. Obtention and Characterization of Silane based Films for the Protection of Galvanized Steel

    OpenAIRE

    2011-01-01

    Se presenta un estudio del comportamiento de películas de silanos Gamma-Aminopropyl tirethoxysilano y del N-(Beta-Aminoethyl)-Gamma-Aminopropyl trimethoxysilano aplicados por el proceso de revestimiento por inmersión (dip-coating) sobre el acero galvanizado. Se usan los mecanismos de curado térmico y curado por irradiación ultravioleta. Los substratos y revestimientos a base de zinc reciben normalmente un tratamiento de superficie para mejorar la resistencia a la corrosión, pero usan cromo he...

  9. Clay Functionalization with Different Aminosilanes for Nanocomposites Preparation

    Science.gov (United States)

    Piscitelli, F.; Callegaro, G.; Lavorgna, M.; Amendola, E.; Mensitieri, G.; Acierno, D.

    2008-08-01

    This is study describes the preparation and the characterization of nanocomposites obtained by dispersion of amino-functionalised clays in DGEBA based adhesives. The amino-functionalised clays were obtained through silylation of Na+ Cloisite with three different aminosilanes such as A1100 (3-aminopropyltriethoxysilane), A1120 (N(beta-aminoethyl)Y-aminopropyltrimethoxy-silane) and A1130 (Triaminofunctional silane). The presence of amino moieties on the layered silicates was confirmed by FTIR, thermal gravimetric and X-ray diffraction analysis. In particular it was evidenced that the d-spacing between platelets constituting the tactoid filler increases as shorter is the organic chains of the different silanes. The nanocomposites obtained by dispersing the amino functionalised clays into a commercial epoxy adhesive were characterised in terms of thermal and mechanical behaviour.

  10. Nitric oxide synthase inhibitors containing the carboxamidine group or its isosteres

    Energy Technology Data Exchange (ETDEWEB)

    Proskuryakov, Sergei Ya; Konoplyannikov, Anatoly G; Skvortzov, Valery G [Medical Radiological Research Centre, Russian Academy of Medical Sciences (Russian Federation); Mandrugin, Andrey A; Fedoseev, Vladimir M [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

    2005-09-30

    The review summarises structures, activities and selectivity of NO-synthase (NOS) inhibitors belonging to various classes of chemical compounds. Linear, cyclic and heterocyclic structures containing guanidine, amidine and/or isothiourea fragments are considered. The structure-activity relationships for these inhibitors were analysed in relation to their action on the inducible NOS isoform. This analysis can provide the basis for the synthesis of new more efficient compounds.

  11. NO-inhibiting and vasotropic activity of some compounds with thioamidine group.

    Science.gov (United States)

    Proskuryakov, S Ya; Kucherenko, N G; Trishkina, A I; Filimonova, M V; Shevchuk, A G; Shtein, L V; Verkhovskii, Yu G; Konoplyannikov, A G; Mandrugin, A A; Fedoseev, V M; Skvortsov, V G

    2002-10-01

    Using the method of electron paramagnetic spectroscopy we demonstrated that thiazine-thiazoline compounds and aminoethyl isothiourea containing the thioamidine group inhibit NO production in the liver of endotoxin-treated mice. Injection of these agents to anesthetized rats increased arterial pressure and enhanced respiration rate. This effect probably reflects inhibition of not only inducible, but also the constitutive synthesis of NO by compounds with thioamidine group.

  12. Obtención y Caracterización de Revestimientos Protectores a Base de Silanos para la Protección de Aceros Galvanizados Obtention and Characterization of Silane based Films for the Protection of Galvanized Steel

    Directory of Open Access Journals (Sweden)

    Sandra R Kunst

    2011-01-01

    Full Text Available Se presenta un estudio del comportamiento de películas de silanos Gamma-Aminopropyl tirethoxysilano y del N-(Beta-Aminoethyl-Gamma-Aminopropyl trimethoxysilano aplicados por el proceso de revestimiento por inmersión (dip-coating sobre el acero galvanizado. Se usan los mecanismos de curado térmico y curado por irradiación ultravioleta. Los substratos y revestimientos a base de zinc reciben normalmente un tratamiento de superficie para mejorar la resistencia a la corrosión, pero usan cromo hexavalente que presenta un elevado grado de toxicidad. Las películas poliméricas conteniendo silanos organofuncionales surgen como alternativa para la pasivación de substratos a base de zinc. Los revestimientos de silano obtenidos fueron evaluados a partir de ensayos electroquímicos y ángulos de mojabilidad y la morfología fue caracterizada por microscopía electrónica de barrido. Los resultados muestran que las películas elaboradas presentan una cobertura homogénea y que el tipo de silano empleado tiene influencia en la formulación y en los parámetros de curado.This work presents a study on the behavior of silane films Gamma-Aminopropyl triethoxysilane and N-(beta-aminoethyl-gamma-Aminopropyl trimethoxysilane, obtained by dip-coating process on galvanized steel. The films were cured by thermal and ultraviolet irradiation cure processes. The substrates and zinc-based coatings are usually employed as surface treatment to improve the corrosion resistance but they employ hexavalent chromium that has a high degree of toxicity. Polymer films containing organofunctional silanes have been studied as an alternative to the passivation of zinc-based substrates. The silane coatings were evaluated by electrochemical tests and contact angle. The film morphology was characterized by scanning electron microscopy. The results showed that the films obtained presented a homogeneous coverage and that the influence of silane employed in the formulation was evident

  13. Calcium-regulated in vivo protein phosphorylation in Zea mays L. root tips

    Science.gov (United States)

    Raghothama, K. G.; Reddy, A. S.; Friedmann, M.; Poovaiah, B. W.

    1987-01-01

    Calcium dependent protein phosphorylation was studied in corn (Zea mays L.) root tips. Prior to in vivo protein phosphorylation experiments, the effect of calcium, ethyleneglycol-bis-(beta-aminoethyl ether)-N-N' -tetraacetic acid (EGTA) and calcium ionophore (A-23187) on phosphorus uptake was studied. Calcium increased phosphorus uptake, whereas EGTA and A-23187 decreased it. Consequently, phosphorus concentration in the media was adjusted so as to attain similar uptake in different treatments. Phosphoproteins were analyzed by two-dimensional gel electrophoresis. Distinct changes in phosphorylation were observed following altered calcium levels. Calcium depletion in root tips with EGTA and A-23187 decreased protein phosphorylation. However, replenishment of calcium following EGTA and ionophore pretreatment enhanced phosphorylation of proteins. Preloading of the root tips with 32P in the presence of EGTA and A-23187 followed by a ten minute calcium treatment, resulted in increased phosphorylation indicating the involvement of calcium, calcium and calmodulin-dependent kinases. Calmodulin antagonist W-7 was effective in inhibiting calcium-promoted phosphorylation. These studies suggest a physiological role for calcium-dependent phosphorylation in calcium-mediated processes in plants.

  14. Sensing of EGTA Mediated Barrier Tissue Disruption with an Organic Transistor

    Directory of Open Access Journals (Sweden)

    Scherrine Tria

    2013-01-01

    Full Text Available Barrier tissue protects the body against external factors by restricting the passage of molecules. The gastrointestinal epithelium is an example of barrier tissue with the primary purpose of allowing the passage of ions and nutrients, while restricting the passage of pathogens and toxins. It is well known that the loss of barrier function can be instigated by a decrease in extracellular calcium levels, leading to changes in protein conformation and an increase in paracellular transport. In this study, ethylene glycol-bis(beta-aminoethyl ether-N,N,N',N'-tetra acetic acid (EGTA, a calcium chelator, was used to disrupt the gastrointestinal epithelial barrier. The effect of EGTA on barrier tissue was monitored by a novel label-free method based on an organic electrochemical transistor (OECT integrated with living cells and validated against conventional methods for measuring barrier tissue integrity. We demonstrate that the OECT can detect breaches in barrier tissue upon exposure to EGTA with the same sensitivity as existing methods but with increased temporal resolution. Due to the potential of low cost processing techniques and the flexibility in design associated with organic electronics, the OECT has great potential for high-throughput, disposable sensing and diagnostics.

  15. Mechanism of blue-light-induced plasma-membrane depolarization in etiolated cucumber hypocotyls

    Science.gov (United States)

    Spalding, E. P.; Cosgrove, D. J.

    1992-01-01

    A large, transient depolarization of the plasma membrane precedes the rapid blue-light (BL)-induced growth suppression in etiolated seedlings of Cucumis sativus L. The mechanism of this voltage transient was investigated by applying inhibitors of ion channels and the plasma-membrane H(+)-ATPase, by manipulating extracellular ion concentrations, and by measuring cell input resistance and ATP levels. The depolarizing phase was not affected by Ca(2+)-channel blockers (verapamil, La3+) or by reducing extracellular free Ca2+ by treatment with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). However, these treatments did reduce the rate of repolarization, indicating an inward movement of Ca2+ is involved. No effects of the K(+)-channel blocker tetraethylammonium (TEA+) were detected. Vanadate and KCN, used to inhibit the H(+)-ATPase, reduced or completely inhibited the BL-induced depolarization. Levels of ATP increased by 11-26% after 1-2 min of BL. Input resistance of trichrome cells, measured with double-barreled microelectrodes, remained constant during the onset of the depolarization but decreased as the membrane voltage became more positive than -90 mV. The results indicate that the depolarization mechanism initially involves inactivation of the H(+)-ATPase with subsequent transient activation of one or more types of ion channels.

  16. A sequential injection system for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples.

    Science.gov (United States)

    Mesquita, Raquel B R; Rangel, António O S S

    2004-08-01

    A sequential injection methodology for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples is proposed. A single manifold is used for the determination of the three analytes, and the same protocol sequence allows the sequential determination of calcium and magnesium (the sum corresponds to the water hardness). The determination of both metals is based on their reaction with cresolphtalein complexone; mutual interference is minimized by using 8-hydroxyquinoline for the determination of calcium and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for the determination of magnesium. Alkalinity determination is based on a reaction with acetic acid, and corresponding color change of Bromcresol Green. Working ranges of 0.5 - 5 mg dm(-3) for Ca, 0.5 - 10 mg dm(-3) for Mg, and 10 - 100 mg HCO3- dm(-3), for alkalinity have been achieved. The results for water samples were comparable to those of the reference methods and to a certified reference water sample. RSDs lower than 5% were obtained, a low reagent consumption and a reduced volume of effluent have been accomplished. The determination rate for calcium and magnesium is 80 h(-1), corresponding to 40 h(-1) per element, while 65 determinations of alkalinity per hour could be carried out.

  17. In vitro and in vivo protein phosphorylation in Avena sativa L. coleoptiles: effects of Ca2+, calmodulin antagonists, and auxin

    Science.gov (United States)

    Veluthambi, K.; Poovaiah, B. W.

    1986-01-01

    In vitro and in vivo protein phosphorylations in oat (Avena sativa L.) coleoptile segments were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by two-dimensional gel electrophoresis. In vitro phosphorylation of several polypeptides was distinctly promoted at 1 to 15 micromolar free Ca2+ concentrations. Ca2(+)-stimulated phosphorylation was markedly reduced by trifluoperazine, chlorpromazine, and naphthalene sulfonamide (W7). Two polypeptides were phosphorylated both under in vitro and in vivo conditions, but the patterns of phosphorylation of several other polypeptides were different under the two conditions indicating that the in vivo phosphorylation pattern of proteins is not truly reflected by in vitro phosphorylation studies. Trifluoperazine, W7, or ethylene glycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) + calcium ionophore A23187 treatments resulted in reduced levels of in vivo protein phosphorylation of both control and auxin-treated coleoptile segments. Analysis by two-dimensional electrophoresis following in vivo phosphorylation revealed auxin-dependent changes of certain polypeptides. A general inhibition of phosphorylation by calmodulin antagonists suggested that both control and auxin-treated coleoptiles exhibited Ca2+, and calmodulin-dependent protein phosphorylation in vivo.

  18. Application of Fragment-Based NMR Screening, X-ray Crystallography, Structure-Based Design, and Focused Chemical Library Design to Identify Novel [mu]M Leads for the Development of nM BACE-1 ([beta]-Site APP Cleaving Enzyme 1) Inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu-Sen; Strickland, Corey; Voigt, Johannes H.; Kennedy, Matthew E.; Beyer, Brian M.; Senior, Mary M.; Smith, Elizabeth M.; Nechuta, Terry L.; Madison, Vincent S.; Czarniecki, Michael; McKittrick, Brian A.; Stamford, Andrew W.; Parker, Eric M.; Hunter, John C.; Greenlee, William J.; Wyss, Daniel F. (SPRI)

    2010-10-18

    Fragment-based NMR screening, X-ray crystallography, structure-based design, and focused chemical library design were used to identify novel inhibitors for BACE-1. A rapid optimization of an initial NMR hit was achieved by a combination of NMR and a functional assay, resulting in the identification of an isothiourea hit with a K{sub d} of 15 {micro}M for BACE-1. NMR data and the crystal structure revealed that this hit makes H-bond interactions with the two catalytic aspartates, occupies the nonprime side region of the active site of BACE-1, and extends toward the S3 subpocket (S3sp). A focused NMR-based search for heterocyclic isothiourea isosteres resulted in several distinct classes of BACE-1 active site directed compounds with improved chemical stability and physicochemical properties. The strategy for optimization of the 2-aminopyridine lead series to potent inhibitors of BACE-1 was demonstrated. The structure-based design of a cyclic acylguanidine lead series and its optimization into nanomolar BACE-1 inhibitors are the subject of the companion paper (J. Med. Chem. 2010, 53, DOI:10.1021/jm901408p).

  19. Determination of risedronate in human urine by column-switching ion-pair high-performance liquid chromatography with ultraviolet detection.

    Science.gov (United States)

    Vallano, P T; Shugarts, S B; Kline, W F; Woolf, E J; Matuszewski, B K

    2003-08-25

    An HPLC assay for the determination of risedronate in human urine was developed and validated. Risedronate and the internal standard were isolated from 5-ml urine samples in a two-part procedure. First, the analytes were precipitated from urine along with endogenous phosphates as calcium salts by the addition of CaCl(2) at alkaline pH. The precipitate was then dissolved in 0.05 M ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and subjected to ion-pair solid-phase extraction using a Waters HLB cartridge (1 ml, 30 mg) with 1-octyltriethylammonium phosphate as the ion-pair reagent. Following extraction, the analytes were initially separated from the majority of co-extracted endogenous components on a Waters X-Terra RP18 (4.6 x 50 mm, 3.5 microm) column. The effluent from the X-Terra was "heart-cut" onto a Phenomenex Synergi Polar RP (4.6 x 150 mm, 4 microm) column for final separation. UV detection (lambda=262 nm) was used to quantitate risedronate in the concentration range of 7.5-250 ng/ml. Mean recovery was 83.3% for risedronate and 86.5% for the internal standard. The intra-day precision of the assay, as assessed by replicate (n=5) standard curves, was better than 6% RSD for all points on the standard curve. Within-day accuracy for the standards ranged from 96.3 to 106.1% of nominal. Inter-day precision for quality controls assayed over a 3-week period was better than 5%, while inter-day accuracy was within 90% of nominal. The assay was employed to analyze samples collected during a clinical pharmacokinetics study.

  20. A sensitive post-column photochemical derivatization/fluorimetric detection system for HPLC determination of bisphosphonates.

    Science.gov (United States)

    Pérez-Ruiz, Tomás; Martínez-Lozano, Carmen; García-Martínez, María Dolores

    2009-02-27

    A new reversed-phase ion-pair high-performance liquid chromatographic (HPLC) method has been developed for the determination of the following bisphosphonic acids: alendronic acid (ALEN), etidronic acid (ETID), ibandronic acid (IBAN) and risedronic acid (RISE). Separation was achieved on a C(18) column using a mixture of 50 mmol L(-1) borate buffer pH 9.0 containing 0.25 mmol L(-1) tetrabutylammonium chloride and 0.5 mmol L(-1) EDTA and acetonitrile (97:3) as the mobile phase. The sensitive detection of the above bisphosphonic acids was based on their oxidation to orthophosphate by the on-line peroxydisulfate-assisted photolysis followed by post-column reaction with molybdate to yield phosphomolybdate. This subsequently reacted with thiamine to generate thiochrome and, finally, the fluorescence of thiochrome was measured at 440 nm with excitation at 375 nm. The developed method is precise with a mean relative standard deviation of 1.3%, sensitive (with a detection limit at the nmol L(-1) level), accurate, specific, rapid (analysis time approximately 13 min) and inexpensive because to the low cost of the reagents. The assay was applied to the analysis of the four bisphosphonic acids in commercial dosage formulations, in which the excipients did not interfere with the determination. The method was also applied to the determination of etidronate, risedronate and ibandronate in human urine. Sample preparation involves precipitation of the analytes from urine along with endogenous phosphates such as calcium salts by addition of calcium chloride at alkaline pH and dissolution of the precipitate in 0.05 mol L(-1) ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid.

  1. Role of calcium in insulin-stimulated NaC1 transport in medullary thick ascending limb.

    Science.gov (United States)

    Ito, O; Kondo, Y; Takahashi, N; Omata, K; Abe, K

    1995-08-01

    It has been reported that insulin stimulates directly NaCl transport in the rabbit medullary thick ascending limb (MTAL) [O. Ito, Y. Kondo, N. Takahashi, K. Kudo, Y. Imai, K. Omata, and K. Abe. Am. J. Physiol. 267 (Renal Fluid Electrolyte Physiol. 36): F265-F270, 1994]. In the present investigation, we evaluated the role of Ca2+ in insulin-stimulated NaCl transport in rabbit MTAL by in vitro microperfusion methods. In control experiments, insulin increases transepithelial voltage (Vte) and net lumen-to-bath Cl-flux (JCl). The effects of insulin on Vte and JCl in a Ca2+ -free solution containing ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N' -tetraacetic acid did not differ from those in a Ca2+ -containing control solution. Direct measurements of cytosolic free Ca2+ ([Ca2+]i) with fura 2 fluorescence showed that insulin caused no detectable change in [Ca2+]i in MTAL cells. Chelation of intracellular Ca2+ with the acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid inhibited the actions of insulin in Vte and JCl without affecting basal values. We examined further whether calmodulin is also involved in insulin-stimulated NaCl transport in MTAL using two dissimilar inhibitors of calmodulin, trifluoperazine (TFP) and N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7). TFP and W-7 inhibited the action of insulin in a dose-dependent manner, with maximal inhibition of both agents of > 90%. The half-maximal inhibition by TFP and W-7 was approximately 50 and 100 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Essential features of the P-glycoprotein pharmacophore as defined by a series of reserpine analogs that modulate multidrug resistance.

    Science.gov (United States)

    Pearce, H L; Safa, A R; Bach, N J; Winter, M A; Cirtain, M C; Beck, W T

    1989-07-01

    We have shown previously that reserpine is an effective "modulator" of P-glycoprotein-associated multidrug resistance (MDR). In addition to enhancing drug cytotoxicity in our multidrug-resistant human leukemia cell line, CEM/VLB100, reserpine strongly competes with a photoactivatible analog of vinblastine, N-(p-azido-3-[125I]iodosalicyl)-N'-(beta-aminoethyl)vindesine, for binding to P-glycoprotein. We also demonstrated previously that there are three substructural domains present in many compounds that modulate P-glycoprotein-associated MDR: a basic nitrogen atom and two planar aromatic rings. In the present study, we wished to test more rigorously the hypothesis that not only are these domains necessary for modulators of MDR but also they must exist in an appropriate conformation. Reserpine is a modulator of MDR in which these domains are present in a well-defined conformation. Accordingly, we prepared eight compounds that vary the spatial orientation of these domains, using either naturally occurring reserpine or yohimbine as chemical templates. When tested for their ability to enhance the cytotoxic activity of natural product antitumor drugs in CEM/VLB100 cells, five compounds that retained the pendant benzoyl function in an appropriate spatial orientation all modulated MDR. By contrast, compounds lacking this moiety failed to do so. These active modulators competed strongly with the 125I-labeled vinblastine analog for binding to P-glycoprotein in plasma membrane vesicles prepared from these cells. Conformational analysis using molecular mechanics revealed the structural similarities of the active modulators. Our results support the hypothesis that the relative disposition of aromatic rings and basic nitrogen atom is important for modulators of P-glycoprotein-associated MDR, and they suggest a ligand-receptor relationship for these agents. These results also provide direction for the definition of an MDR "pharmacophore."

  3. Adenosine actions on CA1 pyramidal neurones in rat hippocampal slices.

    Science.gov (United States)

    Greene, R W; Haas, H L

    1985-09-01

    Intracellular recordings with a bridge amplifier of CA1 pyramidal neurones in vitro were employed to study the mechanisms of action of exogenously applied adenosine in the hippocampal slice preparation of the rat. Adenosine enhanced the calcium-dependent, long-duration after-hyperpolarization (a.h.p.) at least in part by a reduction in the rate of decay of the a.h.p. Both the reduced rate of decay and that of the control can be described with a single exponential. Antagonism of the calcium-dependent potassium current (and as a result, the a.h.p.) by bath application of CdCl2 or intracellular injection of EGTA (ethyleneglycolbis-(beta-aminoethyl ether)N,N'-tetraacetic acid) did not reduce the adenosine-evoked hyperpolarization or decrease in input resistance. Similarly, TEA (tetraethylammonium), which antagonizes both the voltage- and calcium-sensitive, delayed, outward rectification, had no effect on the adenosine-evoked changes in resting membrane properties. Adenosine did not affect the early, transient, outward rectification. During exposure to 4-aminopyridine (4-AP) in concentrations sufficient to antagonize this early rectification, the changes in resting membrane properties evoked by adenosine were unaffected. We conclude that the enhancement of the a.h.p. and accommodation by adenosine may be mediated by a change in the regulation of intracellular calcium. However, the mechanism responsible for the hyperpolarization and decrease in input resistance evoked by adenosine is both calcium and voltage insensitive. Thus, it appears distinct from that mediating the enhancement of the a.h.p. and accommodation.

  4. Carbon monoxide increases inducible NOS expression that mediates CO-induced myocardial damage during ischemia-reperfusion.

    Science.gov (United States)

    Meyer, Grégory; André, Lucas; Kleindienst, Adrien; Singh, François; Tanguy, Stéphane; Richard, Sylvain; Obert, Philippe; Boucher, François; Jover, Bernard; Cazorla, Olivier; Reboul, Cyril

    2015-04-01

    We investigated the role of inducible nitric oxide (NO) synthase (iNOS) on ischemic myocardial damage in rats exposed to daily low nontoxic levels of carbon monoxide (CO). CO is a ubiquitous environmental pollutant that impacts on mortality and morbidity from cardiovascular diseases. We have previously shown that CO exposure aggravates myocardial ischemia-reperfusion (I/R) injury partly because of increased oxidative stress. Nevertheless, cellular mechanisms underlying cardiac CO toxicity remain hypothetical. Wistar rats were exposed to simulated urban CO pollution for 4 wk. First, the effects of CO exposure on NO production and NO synthase (NOS) expression were evaluated. Myocardial I/R was performed on isolated perfused hearts in the presence or absence of S-methyl-isothiourea (1 μM), a NOS inhibitor highly specific for iNOS. Finally, Ca(2+) handling was evaluated in isolated myocytes before and after an anoxia-reoxygenation performed with or without S-methyl-isothiourea or N-acetylcystein (20 μM), a nonspecific antioxidant. Our main results revealed that 1) CO exposure altered the pattern of NOS expression, which is characterized by increased neuronal NOS and iNOS expression; 2) cardiac NO production increased in CO rats because of its overexpression of iNOS; and 3) the use of a specific inhibitor of iNOS reduced myocardial hypersensitivity to I/R (infarct size, 29 vs. 51% of risk zone) in CO rat hearts. These last results are explained by the deleterious effects of NO and reactive oxygen species overproduction by iNOS on diastolic Ca(2+) overload and myofilaments Ca(2+) sensitivity. In conclusion, this study highlights the involvement of iNOS overexpression in the pathogenesis of simulated urban CO air pollution exposure.

  5. Calcium ion requirement for acetylcholine-stimulated breakdown of triphosphoinositide in rabbit iris smooth muscle.

    Science.gov (United States)

    Akhtar, R A; Abdel-Latif, A A

    1978-03-01

    Previous studies from this laboratory have established that addition of acetylcholine (ACh) or norepinephrine to 32P-labeled rabbit iris smooth muscle increases significantly the breakdown of triphosphoinositide (TPI) and that these stimulatory effects are blocked by atropine and phentolamine, respectively. The present studies were undertaken in order to show the effect of Ca++ on the ACh-stimulated breakdown of TPI ("TPI effect") in this tissue. Paired iris smooth muscles were prelabeled with 32Pi for 30 minutes at 37 degrees C in Ca++-free iso-osmotic salt medium. The prelabeled irises were then washed and incubated for 10 minutes in nonradioactive Ca++-free medium which contained 10 mM 2-deoxyglucose under various conditions. The phospholipids were isolated by means of two-dimensional thin-layer chromatography and their radioactivities were determined. In the absence of Ca++, 50 micrometer ACh increased TPI breakdown and phosphatidic acid (PA) labeling by 16 and 38%, respectively. In the absence of ACh, 0.75 micrometer Ca++ increased TPI breakdown and PA labeling by 11 and 20%, respectively. When both ACh and Ca++ were added, the increase in TPI breakdown and PA labeling rose to 32 and 74%, respectively. The labeling of phosphatidylinositol was found to be insensitive to the presence of Ca++. Ca++ was determined in the iris smooth muscle and it was found to contain 3.13 mumol of Ca++ per g of tissue. This was reduced by 80% after the muscle was washed and incubated in a medium which contained 0.25 micrometer ethyleneglycol bis (beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA). The TPI effect was abolished by 0.25 micrometer EGTA and restored when excess Ca++ (1.25 micrometer) was added. Concentrations of Ca++ as low as 50 micrometer provoked a TPI effect. Sr++ (2 micrometer), but not Ba++ or Mn++, was found to substitute partially for Ca++. Ionophore A-23187 (20 micrometer) was found to increase the breakdown of TPI and labeling of PA by 11 and 24

  6. Is it possible to study the kinetic parameters of interaction between PNA and parallel and antiparallel DNA by stopped-flow fluorescence?

    Science.gov (United States)

    Barbero, N; Cauteruccio, S; Thakare, P; Licandro, E; Viscardi, G; Visentin, S

    2016-10-01

    Peptide nucleic acids (PNAs) are among the most interesting and versatile artificial structural mimics of nucleic acids and exhibit peculiar and important properties (i.e. high chemical stability, and a high resistance to cellular enzymes and nucleases). Despite their unnatural structure, they are able to recognize and bind DNA and RNA in a very high, specific and selective manner. One of the most popular, easy and reliable method to measure the stability of PNA-DNA hybrid systems is the melting temperature but the thermodynamic data are obtained using a big quantity of materials failing to provide information on the kinetics of the interaction. In the present work, the PNA decamer 6, with the TCACTAGATG sequence of nucleobases, and the corresponding fluorescent PNA-FITU (fluorescein isothiourea) decamer 8 were synthesized with standard manual Boc-based chemistry. The interaction of the PNA-FITU with parallel and antiparallel DNA has been studied by stopped-flow fluorescence, which is proposed as an alternative technique to obtain the kinetic parameters of the binding. The great advantage of using the stopped-flow technique is the possibility of studying the kinetics of the PNA-DNA duplex formation in a physiological environment. In particular, fluorescence stopped-flow technique has been exploited to compare the affinity of two PNA-DNA duplexes since it can discriminate between parallel and antiparallel DNA binding.

  7. Involvement of Nitric Oxide in a Rat Model of Carrageenin-Induced Pleurisy

    Directory of Open Access Journals (Sweden)

    Masahiro Iwata

    2010-01-01

    Full Text Available Some evidence indicates that nitric oxide (NO contributes to inflammation, while other evidence supports the opposite conclusion. To clarify the role of NO in inflammation, we studied carrageenin-induced pleurisy in rats treated with an NO donor (NOC-18, a substrate for NO formation (L-arginine, and/or an NO synthase inhibitor (S-(2-aminoethyl isothiourea or NG-nitro-L-arginine. We assessed inflammatory cell migration, nitrite/nitrate values, lipid peroxidation and pro-inflammatory mediators. NOC-18 and L-arginine reduced the migration of inflammatory cells and edema, lowered oxidative stress, and normalized antioxidant enzyme activities. NO synthase inhibitors increased the exudate formation and inflammatory cell number, contributed to oxidative stress, induced an oxidant/antioxidant imbalance by maintaining high O−2, and enhanced the production of pro-inflammatory mediators. L-arginine and NOC-18 reversed the proinflammatory effects of NO synthase inhibitors, perhaps by reducing the expression of adhesion molecules on endothelial cells. Thus, our results indicate that NO is involved in blunting—not enhancing—the inflammatory response.

  8. KINETICS OF POLYMERIZATION OF ACRYLONITRILE INITIATED BY VANADIUM(V) - THIOUREA REDOX SYSTEM

    Institute of Scientific and Technical Information of China (English)

    WU Jinyuan; YANG Chaoxiong; WU Yuxian

    1990-01-01

    The kinetics of polymerization of acrylonitrile (AN) initiated by quinquevalent vanadium (V5+ )-thiourea (TU) redox system has been investigated in aqueous nitric acid in the temperature range from 30 to 50 ℃ . The polymerization rate (Rp) can be expressed as follows:Rp= 2.80×105e- 14,200/RT[AN] 2,2[V5+] 0~1/3[TU] 0~4/3[HNO3] 0.2. In the copolymerization of acrylonitrile with methyl acrylate (MA), the reactivity ratios were found to be 1.0 and 1.1, respectively. The experimental observations suggest that the initiating species is probably a complex consisting of a central ion of Lewis acid-VO+2 and the ligands of Lewis bases-acrylonitrile, thiourea, and nitrate anions, while the initiating system in lower concentration, the polymerization of acrylonitrile does not occur if the thiourea is acidified prior to its reaction with quinquevalent vanadium. This indicates that the primary radicals (or the monomeric radicals in the present article) are produced by associated thiourea rather than isothiourea.

  9. Possible involvement of NO in the stimulating effect of pifithrins on survival of hemopoietic clonogenic cells.

    Science.gov (United States)

    Proskuryakov, S Ya; Konoplyannikov, A G; Konoplyannikova, O A; Shevchenko, L I; Verkhovskii, Yu G; Tsyb, A F

    2009-02-01

    Pifithrin alpha (PFTalpha), one of the first known low molecular weight modulators of activity of tumor suppressor p53, increases survival of hemopoietic clonogenic cells (evaluated by the criterion of formation of endogenous spleen CFU-C8 colonies in irradiated animals). This effect appeared when PFTalpha was administered either before or after irradiation. Increase in CFU-C8 was also observed after administration of two PFTalpha analogs, derivatives of 2-amino-4,5,6,7-tetrahydrobenzothiazole. These included a parent compound, 2-ATBT (2-amino-4,5,6,7-tetrahydrobenzothiazole), which is used for synthesis of PFTalpha, and a product of its intramolecular cyclization under physiological conditions, cyclo-PFT (2-(4-methylphenyl)imidazo[2,1-b]-5,6,7,8-tetrahydrobenzothiazole). Earlier we found that many low molecular weight compounds increasing number of CFU-C8 (e.g. isothiourea derivatives) demonstrate NO inhibitory activity. Such activity was also found in 2-ATBT and cyclo-PFT by means of EPR spectroscopy of NO. These compounds caused more than twofold inhibition of NO production in vivo. Thus, it has been demonstrated that PFTalpha and its structural analogs increase survival of hemopoietic clonogenic cells in vivo, and NO may play a role in the mechanism of this effect.

  10. Thiodisaccharides with galactofuranose or arabinofuranose as terminal units: synthesis and inhibitory activity of an exo beta-D-galactofuranosidase.

    Science.gov (United States)

    Repetto, Evangelina; Marino, Carla; Uhrig, M Laura; Varela, Oscar

    2009-04-01

    Thiodisaccharides having beta-D-Galf or alpha-L-Araf units as non-reducing end have been synthesized by the SnCl(4)- or MoO(2)Cl(2)-promoted thioglycosylation of per-O-benzoyl-D-galactofuranose (1), its 1-O-acetyl analogue 4, or per-O-acetyl-alpha-L-arabinofuranose (16) with 6-thioglucose or 6-thiogalactose derivatives. After convenient removal of the protecting groups, the free thiodisaccharides having the basic structure beta-D-Galf(1-->6)-6-thio-alpha-D-Glcp-OMe (5) or beta-D-Galf(1-->6)-6-thio-alpha-D-Galp-OMe (15) were obtained. The respective alpha-L-Araf analogues 18 and 20 were prepared similarly from 16. Alternatively, beta-D-Galf(1-->4)-4-thio-3-deoxy-alpha-L-Xylp-OiPr was synthesized by Michael addition to a sugar enone of 1-thio-beta-d-Galf derivative, generated in situ from the glycosyl isothiourea derivative of 1. The free S-linked disaccharides were evaluated as inhibitors of the beta-galactofuranosidase from Penicillium fellutanum, being 15 and 20 the more active inhibitors against this enzyme.

  11. Fungal lectin of Peltigera canina induces chemotropism of compatible Nostoc cells by constriction-relaxation pulses of cyanobiont cytoskeleton.

    Science.gov (United States)

    Díaz, Eva Maria; Vicente-Manzanares, Miguel; Sacristan, Mara; Vicente, Carlos; Legaz, Maria-Estrella

    2011-10-01

    A glycosylated arginase acting as a fungal lectin from Peltigera canina is able to produce recruitment of cyanobiont Nostoc cells and their adhesion to the hyphal surface. This implies that the cyanobiont would develop organelles to motility towards the chemoattractant. However when visualized by transmission electron microscopy, Nostoc cells recently isolated from P. canina thallus do not reveal any motile, superficial organelles, although their surface was covered by small spindles and serrated layer related to gliding. The use of S-(3,4-dichlorobenzyl)isothiourea, blebbistatin, phalloidin and latrunculin A provide circumstantial evidence that actin microfilaments rather than MreB, the actin-like protein from prokaryota, and, probably, an ATPase which develops contractile function similar to that of myosin II, are involved in cell motility. These experimental facts, the absence of superficial elements (fimbriae, pili or flagellum) related to cell movement, and the appearance of sunken cells during of after movement verified by scanning electron microscopy, support the hypothesis that the motility of lichen cyanobionts could be achieved by contraction-relaxation episodes of the cytoskeleton induced by fungal lectin act as a chemoattractant.

  12. Reactive nitrogen species in acetaminophen-induced mitochondrial damage and toxicity in mouse hepatocytes.

    Science.gov (United States)

    Burke, Angela S; MacMillan-Crow, Lee Ann; Hinson, Jack A

    2010-07-19

    Acetaminophen (APAP) toxicity in primary mouse hepatocytes occurs in two phases. The initial phase (0-2 h) occurs with metabolism to N-acetyl-p-benzoquinoneimine which depletes glutathione, and covalently binds to proteins, but little toxicity is observed. Subsequent washing of hepatocytes to remove APAP and reincubating in media alone (2-5 h) results in toxicity. We previously reported that the reincubation phase occurs with mitochondrial permeability transition (MPT) and increased oxidative stress (dichlorodihydrofluorescein fluorescence) (DCFH(2)). Since DCFH(2) may be oxidized by multiple oxidative mechanisms, we investigated the role of reactive nitrogen species (RNS) leading to 3-nitrotyrosine in proteins by ELISA and by immunoblots. Incubation of APAP with hepatocytes for 2 h did not result in toxicity or protein nitration; however, washing hepatocytes and reincubating in media alone (2-5 h) resulted in protein nitration which correlated with toxicity. Inclusion of the MPT inhibitor, cyclosporine A, in the reincubation media eliminated toxicity and protein nitration. The general nitric oxide synthase (NOS) inhibitor L-NMMA and the neuronal NOS (NOS1) inhibitor, 7-nitroindazole, added in the reincubation media decreased toxicity and protein nitration; however, neither the inducible NOS (NOS2) inhibitors L-NIL (N6-(1-iminoethyl)-L-lysine) nor SAIT (S-(2-aminoethyl)isothiourea) decreased protein nitration or toxicity. The RNS scavengers, N-acetylcysteine, and high concentrations of APAP, added in the reincubation phase decreased toxicity and protein nitration. 7-Nitroindazole and cyclosporine A inhibited the APAP-induced loss of mitochondrial membrane potential when added in the reincubation phase. The data indicate a role for RNS in APAP induced toxicity.

  13. The novel Na+/Ca2+ exchange inhibitor KB-R7943 also blocks native and expressed neuronal nicotinic receptors

    Science.gov (United States)

    Pintado, Antonio J; Herrero, Carlos J; García, Antonio G; Montiel, Carmen

    2000-01-01

    We studied the effects of the novel Na+/Ca2+ exchange inhibitor KB-R7943, 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methanesulphonate, on the native nicotinic receptors present at the bovine adrenal chromaffin cells, as well as on rat brain α3β4 and α7 nicotinic acetylcholine receptors (AChRs) expressed in Xenopus oocytes.As expected, KB-R7943 blocked the Na+-gradient dependent 45Ca2+ uptake into chromaffin cells (IC50 of 5.5 μM); but in addition, the compound also inhibited the 45Ca2+ entry and the increase of cytosolic Ca2+ concentration, [Ca2+]c, stimulated by 5 s pulses of ACh (IC50 of 6.5 and 1.7 μM, respectively).In oocytes expressing α3β4 and α7 nicotinic AChRs, voltage-clamped at −60 mV, inward currents elicited by 1 s pulses of 100 μM ACh (IACh) were blocked by KB-R7943 with an IC50 of 0.4 μM and a Hill coefficient of 0.9.Blockade of α3β4 currents by KB-R7943 was noncompetitive; moreover, the blocker (0.3 μM) became more active as the ACh concentration increased (34 versus 66% blockade at 30 μM and 1 mM ACh, respectively).Inhibition of α3β4 currents by 0.3 μM KB-R7943 was more pronounced at hyperpolarized potentials. If given within the ACh pulse (10 μM), the inhibition amounted to 33, 64 and 80% in oocytes voltage-clamped at −40, −60 and −100 mV, respectively. The onset of blockade was faster and the recovery slower at −100 mV; the reverse was true at −40 mV.In conclusion, KB-R7943 is a potent blocker of nicotinic AChRs; moreover, it displays many features of an open-channel blocker at the rat brain α3β4 AChR. These results should be considered when KB-R7943 is to be used to study Ca2+ homeostasis in cells expressing nicotinic AChRs and the Na+/Ca2+ exchanger. PMID:10952680

  14. Efficient Synthesis and Crystal Structure of 2-Amino-4-thiazolinones%2-氨基-4-噻唑啉酮的高效合成和晶体结构

    Institute of Scientific and Technical Information of China (English)

    孟祥武; 陆丰平; 赵华绒

    2011-01-01

    In this paper,a simple,environment-friendly and efficient one-pot way to synthesize 2-amino-4-thiazolinones at room temperature was reported.Ethyl 2-thiocyanatoacetate was formed by sub-stitution reaction of ethyl chloroacetate with thiocyanate in SCN.After that,when HOAc was em-ployed as a catalyst,2-amino-4-thiazolinones were produced in high yields through the nucleophilic attack of amines to ethyl 2-thiocyanatoacetate following ring-closing reaction of intermediate product S-alkyl isothioureas.As a task-specific ionic liquid,SCN plays a role of a solvent as well as a reactant.And it can be recycled.The crystal structure of 2-(4-ethylpiperzin-1-yl)-4-thiazolinone(3i) was confirmed by X-ray diffraction study.%研究了室温下一锅法高效合成2-氨基-4-噻唑啉酮的绿色方法.在[Bmim]SCN体系中,硫氰酸根取代氯乙酸乙酯中的氯可得到2-硫氰酸根乙酸乙酯.而后,在醋酸催化下,通过各种胺对2-硫氰酸根乙酸乙酯的亲核进攻以及中间产物S-烃基异硫脲的关环反应,以较高的产率合成得到2-氨基-4-噻唑啉酮.功能化离子液体[Bmim]SCN既作为第一步反应原料,又作为反应介质,并可回收利用.同时通过对产物2-(4-乙基-1-哌嗪基)-4-噻唑啉酮(3i)晶体进行X单晶衍射和结构解析证实其结构.

  15. Nitric oxide mediates the fungal elicitor-induced Taxol biosynthesis of Taxus chinensis suspension cells through the reactive oxygen species-dependent and-independent signal pathways

    Institute of Scientific and Technical Information of China (English)

    XU Maojun; DONG Jufang

    2006-01-01

    Nitric oxide and reactive oxygen species are two important signal molecules that play key roles in plant defense responses. Nitric oxide generation and oxidative burst and accumulation of reactive oxygen species are the early reactions of Taxus chinensis suspension cells to fungal elicitor prepared from the cell walls of Penicillium citrinum. In order to investigate the relationship and/or interactions of nitric oxide and reactive oxygen species in the elicitor-induced Taxol biosynthesis of T. chinensis suspension cells, we treated the cells with nitric oxide specific scavenger 2-4-carboxyphenyl-4,4,5,5-tetra- methylimidazoline-1-oxyl-3-oxide (cPITO), nitric oxide synthase inhibitor S,S(-1,3-phenylene-bis(1,2-eth- anediyl)-bis-isothiourea (PBITU), membrane NAD(P) H oxidase inhibitor diphenylene iodonium (DPI), superoxide dismutases (SOD) and catalase. The results show that pretreatment of T. chinensis cells with cPITO and DPI inhibited not only the elicitor-induced nitric oxide biosynthesis and oxidative burst, but also the elicitor-induced Taxol production, suggesting that both nitric oxide and reactive oxygen species are involved in elicitor-induced Taxol biosynthesis. Furthermore, pretreatment of the cells with cPITO and PBITU suppressed the elicitor-induced oxidative burst, indicating that the oxidative burst might be dependent on NO. Application of nitric oxide via its donor sodium nitroprusside (SNP) triggered Taxol biosynthesis of T. chinensis cells. The nitric oxide-induced Taxol production was suppressed by DPI, showing that the oxidative burst is involved in NO-triggered Taxol biosynthesis. However, nitric oxide and the fungal elicitor induced Taxol biosynthesis even though the accumulation of reactive oxygen species wass completely abolished in T. chinensis cells. Our data show that nitric oxide may mediate the elicitor-induced Taxol biosynthesis of T. chinensis suspension cells through both reactive oxygen species-dependent and -independent signal

  16. Signal interaction between nitric oxide and hydrogen peroxide in heat shock-induced hypericin production of Hypericum perforatum suspension cells

    Institute of Scientific and Technical Information of China (English)

    XU MaoJun; DONG JuFang; ZHANG XinBo

    2008-01-01

    Heat shock (HS, 40℃, 10 min) induces hypericin production, nitric oxide (NO) generation, and hydrogen peroxide (H2O2) accumulation of Hypericum perforatum suspension cells. Catalase (CAT) and NO spe-cific scavenger 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) suppress not only the HS-induced H2O2 generation and NO burst, but also the HS-triggered hypericin produc-tion. Hypericin contents of the cells treated with both NO and H2O2 are significantly higher than those of the cells treated with NO alone, although H2O2 per se has no effects on hypericin production of the cells, which suggests the synergistic action between H2O2 and NO on hypericin production. NO treatmentenhances H2O2 levels of H. perforatum cells, while external application of H2O2 induces NO generation of cells. Thus, the results reveal a mutually amplifying action between H2O2 and NO in H. perforatum cells. CAT treatment inhibits both HS-induced H2O2 accumulation and NO generation, while cPTIO can also suppress H2O2 levels of the heat shocked cells. The results imply that H2O2 and NO may enhance each other's levels by their mutually amplifying action in the heat shocked cells. Membrane NAD(P)H oxidase inhibitor diphenylene iodonium (DPI) and nitric oxide synthase (NOS) inhibitor S,S'-1,3-phenylene-bis(1,2-ethanediyl)-bis-isothiourea (PBITU) not only inhibit the mutually amplifying action between H2O2 and NO but also abolish the synergistic effects of H2O2 and NO on hypericin production, showing that the synergism of H2O2 and NO on secondary metsbolite biosynthesis might be dependent on their mutual amplification. Taken together, data of the present work demonstrate that both H2O2 and NO are essential for HS-induced hypericin production of H. perforatum suspension cells. Furthermore, the results reveal a special interaction between the two signal molecules in mediating HS-triggered secondary metabolite biosynthesis of the cells.