Sample records for calcium-and-magnesium ion-dependent adenosine

  1. Effects of calcium and magnesium on strontium distribution coefficients

    USGS Publications Warehouse

    Bunde, R.L.; Rosentreter, J.J.; Liszewski, M.J.; Hemming, C.H.; Welhan, J.

    1997-01-01

    The effects of calcium and magnesium on the distribution of strontium between a surficial sediment and simulated wastewater solutions were measured as part of an investigation to determine strontium transport properties of surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. The investigation was conducted by the U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy. Batch experimental techniques were used to determine strontium linear sorption isotherms and distribution coefficients (K(d)'s) using simulated wastewater solutions prepared at pH 8.0??0.1 with variable concentrations of calcium and magnesium. Strontium linear sorption isotherm K(d)'s ranged from 12??1 to 85??3 ml/g, increasing as the concentration of calcium and magnesium decreased. The concentration of sorbed strontium and the percentage of strontium retained by the sediment were correlated to aqueous concentrations of strontium, calcium, and magnesium. The effect of these cation concentrations on strontium sorption was quantified using multivariate least-squares regression techniques. Analysis of data from these experiments indicates that increased concentrations of calcium and magnesium in wastewater discharged to waste disposal ponds at the INEL increases the availability of strontium for transport beneath the ponds by decreasing strontium sorption to the surficial sediment.

  2. Increased renal calcium and magnesium transporter abundance in streptozotocin-induced diabetes mellitus

    Microsoft Academic Search

    C-T Lee; Y-H H Lien; L-W Lai; J-B Chen; C-R Lin; H-C Chen

    2006-01-01

    Diabetes is associated with renal calcium and magnesium wasting, but the molecular mechanisms of these defects are unknown. We measured renal calcium and magnesium handling and investigated the effects of diabetes on calcium and magnesium transporters in the thick ascending limb and distal convoluted tubule in streptozotocin (STZ)-induced diabetic rats. Rats were killed 2 weeks after inducing diabetes, gene expression

  3. Automatic photometric titrations of calcium and magnesium in carbonate rocks

    USGS Publications Warehouse

    Shapiro, L.; Brannock, W.W.

    1955-01-01

    Rapid nonsubjective methods have been developed for the determination of calcium and magnesium in carbonate rocks. From a single solution of the sample, calcium is titrated directly, and magnesium is titrated after a rapid removal of R2O3 and precipitation of calcium as the tungstate. A concentrated and a dilute solution of disodium ethylenediamine tetraacetate are used as titrants. The concentrated solution is added almost to the end point, then the weak solution is added in an automatic titrator to determine the end point precisely.

  4. Effects of thyroid status on renal calcium and magnesium handling.

    PubMed Central

    McCaffrey, C; Quamme, G A

    1984-01-01

    Renal calcium and magnesium handling was studied in rats with chronic thyroid hormone deficiency or excess, hyperthyroidism. Mean kidney weight of the thyroid deficient rats was 42% of age matched, euthyroid and hyperthyroid animals and glomerular filtration rate was 71% of normal. Fractional sodium excretion was consistently elevated in thyroid deficient rats (0.26%) as compared to euthyroid (0.07%) and hyperthyroid animals (0.07%). Urinary calcium excretion (0.39%) was also elevated and parallel to sodium excretion in thyroid deficiency. Despite this renal leak of sodium and calcium, thyroid deficient animals conserved magnesium much more efficiently than either euthyroid or hyperthyroid rats (5.7% vs 17.4% respectively). Plasma magnesium concentration was elevated by acute MgCl2 infusions to determine the reabsorptive capacity of magnesium. Thyroid deficient rats reabsorbed 15-30% more of the filtered magnesium at any given plasma concentration. Although these effects on electrolyte reabsorption are modest compared to the hemodynamic alterations, the data suggest that thyroid hormone has a direct effect on the tubule which if chronically absent results in subtle sodium and calcium wasting and renal retention of magnesium. Administration of thyroid hormone to euthyroid or thyroid deficient rats twenty-four hours prior to experimentation had no effect on calcium and magnesium handling. PMID:6713257

  5. An examination of the relationship between calcium and magnesium and hypertension 

    E-print Network

    Georghiades, Mary Elizabeth

    1988-01-01

    !ae thr ee blood parameter s best corre)ated with the dietary intake of calcium and magnesium. No i gni f i cant cor r el at i ons (p (0. 05) were ob . , envs d between the calcium, magnesium, or ca)cium/magnesium ratio of the diet and blood tissues... with diastolic blood pressure. Calcium and magnesium were correlated with each other in all tissues studied. These results suggest a complex interaction between calcium and magnesium in their effects on blood pressure exists, which is reflected...

  6. Impact of Testosterone, Zinc, Calcium and Magnesium Concentrations on Sperm Parameters in Subfertile Men

    NASA Astrophysics Data System (ADS)

    Aydemir, Birsen; Kiziler, Ali Riza; Onaran, Ilhan; Alici, Bülent; Özkara, Hamdi; Akyolcu, Mehmet Can

    2007-04-01

    To investigate the impact of testosterone, zinc, calcium and magnesium concentrations in serum and seminal plasma on sperm parameters. There were significant decrease in sperm parameters, serum and seminal plasma zinc levels in subfertile males. It indicates zinc has a essential role in male infertility; the determination the level of zinc during infertility investigation is recommended.

  7. Extraction of phosphorus, potassium, calcium, and magnesium from soils by an ion?exchange resin procedure

    Microsoft Academic Search

    B. van Raij; J. A. Quaggio; N. M. da Silva

    1986-01-01

    A procedure for the simultaneous extraction of phosphorus, potassium, calcium and magnesium from soils, by an ion?exchange resin procedure applicable to large?scale advisory soil testing, is described. The important steps are the disaggregation of soil by shaking in water during 15 minutes with a glass marble, the transference of the elements from the soil to a sodium bicarbonate treated mixture

  8. A field method for the determination of calcium and magnesium in limestone and dolomite

    USGS Publications Warehouse

    Shapiro, Leonard; Brannock, Walter Wallace

    1957-01-01

    The method is an adaptation of a procedure described by Betz and Noll1 in 1950. Calcium and magnesium are determined by visual titration using Versene (disodium ethylenediamine tetraacetate) with Murexide (ammonium purpurate) as the indicator for calcium and Eriochrome Black T as the indicator for magnesium.

  9. Original article Effect of calcium and magnesium ions on the intestinal

    E-print Network

    Paris-Sud XI, Université de

    Original article Effect of calcium and magnesium ions on the intestinal absorption of oleic acid; The effect of Ca++ and Mg++ upon intestinal absorption of oleic acid was investigated using two in vitro synthesis in rat isolated intestinal loops or by the increase in triacylglycerols recovered from

  10. The initial phases of calcium and magnesium phosphates precipitated from solutions of high to medium concentrations

    NASA Astrophysics Data System (ADS)

    Abbona, F.; Madsen, H. E. Lundager; Boistelle, R.

    1986-04-01

    The precipitation of calcium and magnesium phosphates is performed at 25°C by mixing solutions of ammonium phosphate and solutions of calcium and magnesium chlorides under the condition [ P] = [ Ca] + [ Mg] in large pH intervals. Before any nucleation the phosphate concentration ranges from 0.50M to 0.01M. The phases first precipitated are CaHPO 4·2H 2O (brushite), CaHPO 4 (monetite), Ca 3(PO 4) 2· xH 2O (amorphous calcium phosphate), MgNH 4PO 4·6H 2O (struvite), and MgHPO 4·3H 2O (newberyite). The precipitation fields of each phase are determined and discussed as a function of pH, composition and supersaturation. The solutions are even supersaturated with respect to several other calcium phosphates but they never occur first even if their supersaturation is the highest.

  11. Deep SDSS optical spectroscopy of distant halo stars II. Iron, calcium, and magnesium abundances

    E-print Network

    Fernández-Alvar, E; Schlesinger, K J; Beers, T C; Robin, A C; Schneider, D P; Lee, Y S; Bizyaev, D; Ebelke, G; Malanushenko, E; Malanushenko, V; Oravetz, D; Pan, K; Simmons, A

    2015-01-01

    We analyze a sample of 3,944 low-resolution (R ~ 2000) optical spectra from the Sloan Digital Sky Survey (SDSS), focusing on stars with effective temperatures 5800 calcium, and magnesium at large distances from the Galactic center. The median abundances for the halo stars analyzed are fairly constant up to a Galactocentric distance r ~ 20 kpc, rapidly decrease between r ~ 20 and r ~ 40 kpc, and flatten out to significantly lower values at larger...

  12. Production and bioavailability of calcium and magnesium salts of omega-3 fatty acids

    Microsoft Academic Search

    Jaroslav A. Kralovec; H. Stephen Ewart; Jeffrey H. D. Wright; Lynn V. Watson; Dorothy Dennis; Colin J. Barrow

    2009-01-01

    In order to provide an alternative to traditional liquid fish oil gelatin capsules, we developed a solid, powdered form of omega-3 fish oil concentrate by forming calcium- and magnesium-fatty acid salts. These salts were produced using a concentrated fish oil ethyl ester that contained in excess of 60% omega-3 fatty acids. The bioavailability of these omega-3 salts was compared with

  13. Improved methods for reducing calcium and magnesium concentrations in tissue culture medium: Application to studies of lymphoblast proliferation in vitro

    Microsoft Academic Search

    James K. Brennan; James Mansky; Geraldine Roberts; Marshall A. Lichtman

    1975-01-01

    Summary  We have compared several methods for reducing calcium and magnesium concentrations in tissue culture medium, with the objective\\u000a of producing selective deficiency effects on the growth of mouse (L5178Y) and human (P1R) lymphoblasts. In experiments in\\u000a which calcium- and magnesium-“free” McCoy’s medium was supplemented with 15% horse or fetal calf serum, enough calcium and\\u000a magnesium was provided by serum to

  14. Effects of dietary vitamin D on calcium and magnesium levels in mice with abnormal calcium metabolism

    SciTech Connect

    Spurlock, B.G.; West, W.L.; Knight, E.M. (Howard Univ., Washington, DC (United States))

    1991-03-11

    In previous studies vitamin D has been used to induce cardiac calcium overload in laboratory animals. Interrelationships between calcium and magnesium metabolism are also documented. The authors have investigated the effect of varying vitamin D in the diet on calcium and magnesium levels in plasma, kidney and heart of DBA mice which exhibit genetic abnormalities in cardiac calcium metabolism. Weanling DBA mice were maintained for 28 days on an AIN-76 diet containing either 1,000 I.U. of vitamin D{sub 3} per kg of diet (control); 4,000 I.U. of vitamin D{sub 3} per kg of diet; or no vitamin D. When compared to controls, supplemented animals showed significantly higher plasma magnesium, kidney calcium and kidney magnesium levels; animals receiving the vitamin D-deficient diet exhibited increases in cardiac calcium levels. The authors results support previous findings that vitamin D deficiency increases cardiac calcium uptake and suggest a possible role of vitamin D in magnesium metabolism.

  15. [Simultaneous determination of calcium and magnesium in urines by flame atomic absorption spectrometry].

    PubMed

    Bai, Yu; Ouyang, Jian-Ming; Bai, Yan; Chen, Mei-Luan

    2004-08-01

    The contents of calcium and magnesium in urines were simultaneously determined by flame atomic absorption spectrometry. The optimized working conditions were ascertained. For the determination of calcium, the used wavelength was 422.8 nm, and the current of HCL(Hollow Cathode Lamp) was 3 mA; for the determination of magnesium, the used wavelength was 285.2 nm, and the current of HCL (Hollow Cathode Lamp) was 4 mA. The height of burner and the air-acetylene ratio were 8 mm and 6:1, respectively, for the determination of both calcium and magnesium. In order to remove the disturbance of phosphate, sulphate and silicate on the determination of calcium, a releasing reagent can be used. Lanthanum chloride (LaCl3) was tested as a better releasing reagent than strontium chloride (SrCl2). The disturbance of urinary substrate could be avoided after the urines were diluted to 1:100 with distilled water. The concentrations of Ca and Mg in 15 urines were determined under the optimized conditions. The obtained results were consistent with the archived data. The recovery was 96%-104%, the relative standard deviation for a sample was 1.8% with P < 0.05. PMID:15766134

  16. Quality of 4-hourly ejaculates--levels of calcium and magnesium.

    PubMed

    Valsa, J; Skandhan, K P; Gusani, P H; Sahab Khan, P; Amith, S

    2013-02-01

    A four-hourly ejaculation study was conducted in which eleven normal healthy subjects participated. Five of them discontinued after submitting three samples. One alone was present for submission at the end of 16 h (fifth ejaculate), which was his last submission. Physical exhaustion was the sole reason for all participants for their discontinuation from the study. The result showed a decrease in semen volume and sperm count from first to last ejaculate. The increase in motility was probably due to reduction in exposure time to sperm motility inhibitory factors. In general, total motile spermatozoa as well as actively motile spermatozoa progressively increased from first to last ejaculate at the cost of sluggish spermatozoa. A significant increase in seminal plasma calcium and magnesium was seen as well as a significant increase in magnesium inside the cell from the first to the fourth ejaculate. Considering the quality of semen, which was good in sperm count and excellent in motility, calcium and magnesium may be helpful in cleaning motility inhibitory factors of spermatozoa. PMID:22540387

  17. Calcium and Magnesium Levels in Agricultural Soil and Sewage Sludge in an Industrial Area from Southeastern Spain: Relationship with Plant (Saccharum officinarum) Disposition

    Microsoft Academic Search

    A. M. Jodral-Segado; M. Navarro-Alarcón; H. López-G De La Serrana; M. C. López-Martínez

    2006-01-01

    This investigation was initiated to assess the following objectives: (1) to measure the total calcium and magnesium content in agricultural soil and sewage sludge from the Mediterranean coastal area of Motril (southeastern Spain); (2) to determine the pH values of indicated samples in order to evaluate first their influence on calcium and magnesium content, and second on levels of these

  18. Studying the effects of calcium and magnesium on size-distributed nitrate and ammonium with EQUISOLV II

    Microsoft Academic Search

    Mark Z. Jacobson

    1999-01-01

    A chemical equilibrium code was improved and used to show that calcium and magnesium have a large yet different effect on the aerosol size distribution in different regions of Los Angeles. In the code, a new technique of solving individual equilibrium equations was developed. The technique, the analytical equilibrium iteration (AEI) method, gives the same solutions (to at least 7

  19. STUDYING THE EFFECTS OF CALCIUM AND MAGNESIUM ON SIZE-DISTRIBUTED NITRATE AND AMMONIUM WITH EQUISOLV II. (R823186)

    EPA Science Inventory

    Abstract A chemical equilibrium code was improved and used to show that calcium and magnesium have a large yet different effect on the aerosol size distribution in different regions of Los Angeles. In the code, a new technique of solving individual equilibrium equation...

  20. Indirect Determination of Potassium Calcium and Magnesium in Blood Plasma by High Perf ormance Capillary Electrophoresis with UV2Detection

    Microsoft Academic Search

    ZHENG Na

    Potassium sodium calcium and magnesium in blood plasma were separated by high performance capillary elect rop ho resis ( HPCE) in a buffer medium of p H 5. 5 , using tartaric acid as complexing agent . Imidazole was used as backgro und reagent in t he UV2detectio n. Various conditio ns fo r t he CE separation and UV2detection

  1. Chronic dietary fiber supplementation with wheat dextrin does not inhibit calcium and magnesium absorption in premenopausal and postmenopausal women

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This placebo-controlled, randomized, crossover clinical study examined the effect of chronic wheat dextrin intake on calcium and magnesium absorption. Forty premenopausal and post menopausal women (mean +/- SD age 49.9 +/- 9.8 years)consumed wheat dextrin or placebo (15 g/day) for 2 weeks prior to 4...

  2. Anhydrobiosis in yeast: influence of calcium and magnesium ions on yeast resistance to dehydration-rehydration.

    PubMed

    Trofimova, Yuliya; Walker, Graeme; Rapoport, Alexander

    2010-07-01

    The influence of calcium and magnesium ions on resistance to dehydration in the yeast, Saccharomyces cerevisiae, was investigated. Magnesium ion availability directly influenced yeast cells' resistance to dehydration and, when additionally supplemented with calcium ions, this provided further significant increase of yeast resistance to dehydration. Gradual rehydration of dry yeast cells in water vapour indicated that both magnesium and calcium may be important for the stabilization of yeast cell membranes. In particular, calcium ions were shown for the first time to increase the resistance of yeast cells to dehydration in stress-sensitive cultures from exponential growth phases. It is concluded that magnesium and calcium ion supplementations in nutrient media may increase the dehydration stress tolerance of S. cerevisiae cells significantly, and this finding is important for the production of active dry yeast preparations for food and fermentation industries. PMID:20487021

  3. The final phases of calcium and magnesium phosphates precipitated from solutions of high to medium concentration

    NASA Astrophysics Data System (ADS)

    Abbona, Francesco; Lundager Madsen, Hans Erik; Boistelle, Roland

    1988-07-01

    The phases of calcium and magnesium phosphates, which are obtained by evolution at 25°C of the first precipitates in their mother solutions, are described in terms of pH and composition of solutions. The initial conditions were: 0.050M ? [P] ? 0.500M; [P] = [Ca] + [Mg]; 0 ? [Mg]/[Ca] ? 1. The most abundant final phases are brushite, CaHPO 4·2H 2O; monetite, CaHPO 4; newberyite, MgHPO 4·3H 2O and struvite, MgNH 4PO 4·6H 2O. At low concentration whitlockite, Ca 9MgH(PO 4) 7, occurs with the amorphous phase previously precipitated, Ca 3(PO 4) 2·nH 2O. The conditions for stability are discussed and the changes observed are interpreted.

  4. Revised model of calcium and magnesium binding to the bacterial cell wall.

    PubMed

    Thomas, Kieth J; Rice, Charles V

    2014-12-01

    Metals bind to the bacterial cell wall, yet the binding mechanisms and affinity constants are not fully understood. The cell wall of gram positive bacteria is characterized by a thick layer of peptidoglycan and anionic teichoic acids anchored in the cytoplasmic membrane as lipoteichoic acid or covalently bound to the cell wall as wall teichoic acid. The polyphosphate groups of teichoic acid provide one-half of the metal binding sites for calcium and magnesium, which contradicts previous reports that calcium binding is 100 % dependent on teichoic acid. The remaining binding sites are formed with the carboxyl units of peptidoglycan. In this work we report equilibrium association constants and total metal binding capacities for the interaction of calcium and magnesium ions with the bacterial cell wall. Metal binding is much stronger than previously reported. Curvature of Scatchard plots from the binding data and the resulting two regions of binding affinity suggest the presence of negative cooperative binding, which means that the binding affinity decreases as more ions become bound to the sample. For Ca(2+), Region I has a KA = (1.0 ± 0.2) × 10(6) M(-1) and Region II has a KA = (0.075 ± 0.058) × 10(6) M(-1). For Mg(2+), KA1 = (1.5 ± 0.1) × 10(6) and KA2 = (0.17 ± 0.10) × 10(6). A binding capacity (?) is reported for both regions. However, since binding is still occurring in Region II, the total binding capacity is denoted by ?2, which are 0.70 ± 0.04 and 0.67 ± 0.03 µmol/mg for Ca(2+) and Mg(2+) respectively. These data contradict the current paradigm of only a single metal affinity value that is constant over a range of concentrations. We also find that measurement of equilibrium binding constants is highly sample dependent. This suggests a role for diffusion of metals through heterogeneous cell wall fragments. As a result, we are able to reconcile many contradictory theories that describe binding affinity and the binding mode of divalent metal cations. PMID:25315444

  5. In vivo degradation of low temperature calcium and magnesium phosphate ceramics in a heterotopic model.

    PubMed

    Klammert, Uwe; Ignatius, Anita; Wolfram, Uwe; Reuther, Tobias; Gbureck, Uwe

    2011-09-01

    Bone replacement using synthetic and degradable materials is desirable in various clinical conditions. Most applied commercial materials are based on hydroxyapatite, which is not chemically degradable under physiological conditions. Here we report the effect of a long-term intramuscular implantation regime on the dissolution of various low temperature calcium and magnesium phosphate ceramics in vivo. The specimens were analysed by consecutive radiographs, micro-computed tomography scans, compressive strength testing, scanning electron microscopy and X-ray diffractometry. After 15months in vivo, the investigated materials brushite (CaHPO(4)·2H(2)O), newberyite (MgHPO(4)·3H(2)O), struvite (MgNH(4)PO(4)·6H(2)O) and hydroxyapatite (Ca(9)(PO(4))(5)HPO(4)OH) showed significant differences regarding changes of their characteristics. Struvite presented the highest loss of mechanical performance (95%), followed by newberyite (67%) and brushite (41%). This was accompanied by both a distinct extent of cement dissolution as well as changes of the phase composition of the retrieved cement implants. While the secondary phosphate phases (brushite, newberyite, struvite) completely dissolved, re-precipitates of whitlockite and octacalcium phosphate were formed in either particulate or whisker-like morphology. Furthermore, for the first time the possibility of a macropore-free volume degradation mechanism of bioceramics was demonstrated. PMID:21658480

  6. Calcium and magnesium interference studies for the binding of heavy metal ions in solution by Medicago sativa (alfalfa)

    SciTech Connect

    Gardea-Torresdey, J.L.; Tiemann, K.J.; Gonzalez, J.H. [Univ. of Texas, El Paso, TX (United States). Dept. of Chemistry; Henning, J.A.; Townsend, M.S. [New Mexico State Univ., Las Cruces, NM (United States). Dept. of Agronomy and Horticulture

    1996-12-31

    Previous batch laboratory experiments performed to determine the potential ability of seven different varieties of Medicago sativa (alfalfa) revealed that the African shoots population was able to efficiently bind copper(II) and nickel(II) from aqueous solutions. Batch laboratory interference studies were performed with various calcium and magnesium concentrations (0.1 mM to 1 M) in order to ascertain the effects of these ions on the heavy metal binding ability of African alfalfa shoots. Results from these studies have shown that calcium and magnesium did not seriously reduce the binding of copper(II) and lead(II) to African alfalfa shoots. However, high concentrations of calcium and magnesium significantly reduced chromium(III), cadmium(II), nickel(II), and zinc(II) binding to African shoots. In addition, all these experiments were repeated maintaining the ionic strength constant, and similar results were obtained. Interference studies were also conducted in order to determine the effects of hard cations under flow conditions with silica-immobilized African alfalfa shoots. The information obtained from these studies will be useful for an innovative method of heavy metal ion removal and recovery from contaminated waters.

  7. Calcium and magnesium in exocrine secretion--an X-ray microanalytical study

    SciTech Connect

    Roomans, G.M.; Barnard, T.

    1982-01-01

    Calcium and magnesium distribution in mammalian exocrine glands under resting, stimulated and pathological conditions was investigated by X-ray microanalysis of thick and ultrathin cryosections. Ultrathin sections were cut from tissue frozen in the presence of a polymer cryoprotectant, dextran. The effect of this treatment on isolated rabbit pancreas. Dextran caused a disturbance in water and ion transport, partly due to an osmotic effect and the impermeability of the pancreatic epithelium to dextran; this does, however, not necessarily invalidate intracellular measurements on frozen-dried sections. Cholinergic stimulation of the rat pancreas caused a change of Ca distribution from the basal to the apical part of the cell; this may be a component of the secretory Ca flux. Kinetic considerations make a significant Ca movement via the ER-Golgi endomembrane space less likely. The mitochondrial Ca concentration is low, and not significantly changed by cholinergic stimulation. X-ray microanalysis was carried out on submandibular glands of rats after chronic treatment with reserpin and/or isoproterenol (an animal model for cystic fibrosis, CF). The acinar cells had elevated Mg and Ca and lowered K concentrations. Analysis of ultrathin cryosections showed high levels of Ca and Mg in secretory granules, mucus globules and the ER. Ca and Mg in the ER may be transported intracellularly with secretory proteins to secretion granules or mucus globules. The decrease in cell K may be due to efflux of K caused by elevated cytoplasmic Ca levels. A similar decrease in cell K was caused by incubation of rat salivary glands with diluted serum from CF patients, a treatment which has been reported to mimic the effect of a rise in cytoplasmic Ca.

  8. Synthesis and Structural Studies of Calcium and Magnesium Phosphinate and Phosphonate Compounds

    NASA Astrophysics Data System (ADS)

    Bampoh, Victoria Naa Kwale

    The work presented herein describes synthetic methodologies leading to the design of a wide array of magnesium and calcium based phosphinate and phosphonates with possible applications as bone scaffolding materials or additives to bone cements. The challenge to the chemistry of the alkaline earth phosphonate target compounds includes poor solubility of compounds, and poorly understood details on the control of the metal's coordination environment. Hence, less is known on phosphonate based alkaline earth metal organic frameworks as compared to transition metal phosphonates. Factors governing the challenges in obtaining crystalline, well-defined magnesium and calcium solids lie in the large metal diameters, the absence of energetically available d-orbitals to direct metal geometry, as well as the overall weakness of the metal-ligand bonds. A significant part of this project was concerned with the development of suitable reaction conditions to obtain X-ray quality crystals of the reaction products to allow for structural elucidation of the novel compounds. Various methodologies to aid in crystal growth including hydrothermal methods and gel crystallization were employed. We have used phosphinate and phosphonate ligands with different number of phosphorus oxygen atoms as well as diphosphonates with different linker lengths to determine their effects on the overall structural features. An interesting correlation is observed between the dimensionality of products and the increasing number of donor oxygen atoms in the ligands as we progress from phosphinic acid to the phosphorous acids. As an example, monophosphinate ligand only yielded one-dimensional compounds, whereas the phosphonates crystallize as one and two-dimensional compounds, and the di- and triphosphonate based compounds display two or three-dimensional geometries. This thesis provides a selection of calcium and magnesium compounds with one-dimensional geometry, as represented in a calcium phosphinate to novel two-dimensional sheets of magnesium and pillared calcium phosphonates. The preparation of these novel compounds has led to the establishment of synthetic protocols that allow for the direct preparation of compounds with defined structural features.

  9. Deep SDSS optical spectroscopy of distant halo stars. II. Iron, calcium, and magnesium abundances

    NASA Astrophysics Data System (ADS)

    Fernández-Alvar, E.; Allende Prieto, C.; Schlesinger, K. J.; Beers, T. C.; Robin, A. C.; Schneider, D. P.; Lee, Y. S.; Bizyaev, D.; Ebelke, G.; Malanushenko, E.; Malanushenko, V.; Oravetz, D.; Pan, K.; Simmons, A.

    2015-05-01

    Aims: We analyze a sample of 3944 low-resolution (R ~ 2000) optical spectra from the Sloan Digital Sky Survey (SDSS), focusing on stars with effective temperatures 5800 ? Teff ? 6300 K, and distances from the Milky Way plane in excess of 5 kpc, and determine their abundances of Fe, Ca, and Mg. Methods: We followed the same methodology as in the previous paper in this series, deriving atmospheric parameters by ?2 minimization, but this time we obtained the abundances of individual elements by fitting their associated spectral lines. Distances were calculated from absolute magnitudes obtained by a statistical comparison of our stellar parameters with stellar-evolution models. Results: The observations reveal a decrease in the abundances of iron, calcium, and magnesium at large distances from the Galactic center. The median abundances for the halo stars analyzed are fairly constant up to a Galactocentric distance r ~ 20 kpc, rapidly decrease between r ~ 20 and r ~ 40 kpc, and flatten out to significantly lower values at larger distances, consistent with previous studies. In addition, we examine [Ca/Fe] and [Mg/Fe] as a function of [Fe/H] and Galactocentric distance. Our results show that the most distant parts of the halo show a steeper variation of [Ca/Fe] and [Mg/Fe] with iron. We found that at the range -1.6 < [Fe/H] < -0.4, [Ca/Fe] decreases with distance, in agreement with earlier results based on local stars. However, the opposite trend is apparent for [Mg/Fe]. Our conclusion that the outer regions of the halo are more metal-poor than the inner regions, based on in situ observations of distant stars, agrees with recent results based on inferences from the kinematics of more local stars, and with predictions of recent galaxy formation simulations for galaxies similar to the Milky Way. Table 1 and beginning of Tables 2 and 3 are available in electronic form at http://www.aanda.orgFull Tables 2 and 3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A81

  10. Surface properties of calcium and magnesium oxide nanopowders grafted with unsaturated carboxylic acids studied with inverse gas chromatography.

    PubMed

    Maciejewska, Magdalena; Krzywania-Kaliszewska, Alicja; Zaborski, Marian

    2012-09-28

    Inverse gas chromatography (IGC) was applied at infinite dilution to evaluate the surface properties of calcium and magnesium oxide nanoparticles and the effect of surface grafted unsaturated carboxylic acid on the nanopowder donor-acceptor characteristics. The dispersive components (?(s)(D)) of the free energy of the nanopowders were determined by Gray's method, whereas their tendency to undergo specific interactions was estimated based on the electron donor-acceptor approach presented by Papirer. The calcium and magnesium oxide nanoparticles exhibited high surface energies (79 mJ/m² and 74 mJ/m², respectively). Modification of nanopowders with unsaturated carboxylic acids decreased their specific adsorption energy. The lowest value of ?(s)(D) was determined for nanopowders grafted with undecylenic acid, approximately 55 mJ/m². The specific interactions were characterised by the molar free energy (?G(A)(SP)) and molar enthalpy (?H(A)(SP)) of adsorption as well as the donor and acceptor interaction parameters (K(A), K(D)). PMID:22907042

  11. Chelatometric determination of calcium and magnesium in iron ores, slags, anorthosite, limestone, copper-nickel-lead-zinc ores and divers materials.

    PubMed

    Hitchen, A; Zechanowitsch, G

    1980-03-01

    Chelatometric methods for the determination of calcium and magnesium in iron ores, slags, anorthosite, copper-nickel-lead-zinc ores and various other materials are described. Potential interfering elements are masked with triethanolamine and potassium cyanide. In one aliquot calcium is titrated at pH > 12, with calcein and thymolphthalein mixed indicator and in another aliquot calcium and magnesium are titrated in ammonia buffer, with o-cresolphthalein complexone screened with Naphthol Green B as indicator. The results compare favourably with certified values for reference materials of diverse nature. PMID:18962661

  12. Measurement and calculation of the Stark-broadening parameters for the resonance lines of singly ionized calcium and magnesium.

    NASA Technical Reports Server (NTRS)

    Jones, W. W.; Sanchez, A.; Greig, J. R.; Griem, H. R.

    1972-01-01

    The electron-impact-broadened profiles of the resonance lines of singly ionized calcium and magnesium have been measured using an electromagnetically driven shock tube and a rapid-scanning Fabry-Perot spectrometer. For an electron density of 10 to the 17th power per cu cm and a temperature of 19,000 K, we found the Lorentzian half-width of the Ca+ line to be 0.086 A plus or minus 10% and of the Mg+ line to be 0.044 A plus or minus 10%. Using the quantum-mechanical theory of Barnes and Peach and our semiclassical calculation for the calcium lines, we found that the temperature dependence of the theoretical curves is close to that measured, although both theories predict actual values which are somewhat large.

  13. Changes in Sodium, Calcium, and Magnesium Ion Concentrations That Inhibit Geobacillus Biofilms Have No Effect on Anoxybacillus flavithermus Biofilms.

    PubMed

    Somerton, B; Lindsay, D; Palmer, J; Brooks, J; Flint, S

    2015-08-01

    This study investigated the effects of varied sodium, calcium, and magnesium concentrations in specialty milk formulations on biofilm formation by Geobacillus spp. and Anoxybacillus flavithermus. The numbers of attached viable cells (log CFU per square centimeter) after 6 to 18 h of biofilm formation by three dairy-derived strains of Geobacillus and three dairy-derived strains of A. flavithermus were compared in two commercial milk formulations. Milk formulation B had relatively high sodium and low calcium and magnesium concentrations compared with those of milk formulation A, but the two formulations had comparable fat, protein, and lactose concentrations. Biofilm formation by the three Geobacillus isolates was up to 4 log CFU cm(-2) lower in milk formulation B than in milk formulation A after 6 to 18 h, and the difference was often significant (P ? 0.05). However, no significant differences (P ? 0.05) were found when biofilm formations by the three A. flavithermus isolates were compared in milk formulations A and B. Supplementation of milk formulation A with 100 mM NaCl significantly decreased (P ? 0.05) Geobacillus biofilm formation after 6 to 10 h. Furthermore, supplementation of milk formulation B with 2 mM CaCl2 or 2 mM MgCl2 significantly increased (P ? 0.05) Geobacillus biofilm formation after 10 to 18 h. It was concluded that relatively high free Na(+) and low free Ca(2+) and Mg(2+) concentrations in milk formulations are collectively required to inhibit biofilm formation by Geobacillus spp., whereas biofilm formation by A. flavithermus is not impacted by typical cation concentration differences of milk formulations. PMID:26002898

  14. Chronic dietary fiber supplementation with wheat dextrin does not inhibit calcium and magnesium absorption in premenopausal and postmenopausal women.

    PubMed

    Armas, L A G; Rafferty, K; Hospattankar, A; Abrams, S A; Heaney, R P

    2011-01-01

    This placebo-controlled, randomized, crossover clinical study examined the effect of chronic wheat dextrin intake on calcium and magnesium absorption. Forty premenopausal and post menopausal women (mean ± SD age 49.9 ± 9.8 years) consumed wheat dextrin or placebo (15 g/day) for 2 weeks prior to (45)calcium ((45)Ca) and (26)magnesium ((26)Mg) absorption testing. After a standardized breakfast, serial blood and urine samples were obtained. The mean ± SD area under the curve from 0 to 9 h for (45)Ca specific activity was 0.81 ± 0.21 for wheat dextrin and 0.82 ± 0.22 for placebo, showing that wheat dextrin had no effect on calcium absorption. The mean ± SD percentage excess of (26)Mg/(24)Mg was 7.8% ± 2.1% for wheat dextrin and 7.9% ± 2.6% for placebo, showing that wheat dextrin had no effect on magnesium absorption. In conclusion, chronic wheat dextrin consumption did not inhibit calcium or magnesium absorption from the gastrointestinal tract in women. PMID:22117983

  15. Short term spatio-temporal variability of soil water-extractable calcium and magnesium after a low severity grassland fire in Lithuania.

    NASA Astrophysics Data System (ADS)

    Pereira, Paulo; Martin, David

    2014-05-01

    Fire has important impacts on soil nutrient spatio-temporal distribution (Outeiro et al., 2008). This impact depends on fire severity, topography of the burned area, type of soil and vegetation affected, and the meteorological conditions post-fire. Fire produces a complex mosaic of impacts in soil that can be extremely variable at small plot scale in the space and time. In order to assess and map such a heterogeneous distribution, the test of interpolation methods is fundamental to identify the best estimator and to have a better understanding of soil nutrients spatial distribution. The objective of this work is to identify the short-term spatial variability of water-extractable calcium and magnesium after a low severity grassland fire. The studied area is located near Vilnius (Lithuania) at 54° 42' N, 25° 08 E, 158 masl. Four days after the fire, it was designed in a burned area a plot with 400 m2 (20 x 20 m with 5 m space between sampling points). Twenty five samples from top soil (0-5 cm) were collected immediately after the fire (IAF), 2, 5, 7 and 9 months after the fire (a total of 125 in all sampling dates). The original data of water-extractable calcium and magnesium did not respected the Gaussian distribution, thus a neperian logarithm (ln) was applied in order to normalize data. Significant differences of water-extractable calcium and magnesium among sampling dates were carried out with the Anova One-way test using the ln data. In order to assess the spatial variability of water-extractable calcium and magnesium, we tested several interpolation methods as Ordinary Kriging (OK), Inverse Distance to a Weight (IDW) with the power of 1, 2, 3 and 4, Radial Basis Functions (RBF) - Inverse Multiquadratic (IMT), Multilog (MTG), Multiquadratic (MTQ) Natural Cubic Spline (NCS) and Thin Plate Spline (TPS) - and Local Polynomial (LP) with the power of 1 and 2. Interpolation tests were carried out with Ln data. The best interpolation method was assessed using the cross validation method. Cross-validation was obtained by taking each observation in turn out of the sample pool and estimating from the remaining ones. The errors produced (observed-predicted) are used to evaluate the performance of each method. With these data, the mean error (ME) and root mean square error (RMSE) were calculated. The best method was the one which had the lower RMSE (Pereira et al. in press). The results shown significant differences among sampling dates in the water-extractable calcium (F= 138.78, p< 0.001) and extractable magnesium (F= 160.66; p< 0.001). Water-extractable calcium and magnesium was high IAF decreasing until 7 months after the fire, rising in the last sampling date. Among the tested methods, the most accurate to interpolate the water-extractable calcium were: IAF-IDW1; 2 Months-IDW1; 5 months-OK; 7 Months-IDW4 and 9 Months-IDW3. In relation to water-extractable magnesium the best interpolation techniques were: IAF-IDW2; 2 Months-IDW1; 5 months- IDW3; 7 Months-TPS and 9 Months-IDW1. These results suggested that the spatial variability of these water-extractable is variable with the time. The causes of this variability will be discussed during the presentation. References Outeiro, L., Aspero, F., Ubeda, X. (2008) Geostatistical methods to study spatial variability of soil cation after a prescribed fire and rainfall. Catena, 74: 310-320. Pereira, P., Cerdà, A., Úbeda, X., Mataix-Solera, J. Arcenegui, V., Zavala, L. Modelling the impacts of wildfire on ash thickness in a short-term period, Land Degradation and Development, (In Press), DOI: 10.1002/ldr.2195

  16. The effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid/base chemistry: Implications for Eocene and Cretaceous ocean carbon chemistry and buffering

    NASA Astrophysics Data System (ADS)

    Hain, Mathis P.; Sigman, Daniel M.; Higgins, John A.; Haug, Gerald H.

    2015-05-01

    Reconstructed changes in seawater calcium and magnesium concentration ([Ca2+], [Mg2+]) predictably affect the ocean's acid/base and carbon chemistry. Yet inaccurate formulations of chemical equilibrium "constants" are currently in use to account for these changes. Here we develop an efficient implementation of the MIAMI Ionic Interaction Model to predict all chemical equilibrium constants required for carbon chemistry calculations under variable [Ca2+] and [Mg2+]. We investigate the impact of [Ca2+] and [Mg2+] on the relationships among the ocean's pH, CO2, dissolved inorganic carbon (DIC), saturation state of CaCO3 (?), and buffer capacity. Increasing [Ca2+] and/or [Mg2+] enhances "ion pairing," which increases seawater buffering by increasing the concentration ratio of total to "free" (uncomplexed) carbonate ion. An increase in [Ca2+], however, also causes a decline in carbonate ion to maintain a given ?, thereby overwhelming the ion pairing effect and decreasing seawater buffering. Given the reconstructions of Eocene [Ca2+] and [Mg2+] ([Ca2+]~20 mM; [Mg2+]~30 mM), Eocene seawater would have required essentially the same DIC as today to simultaneously explain a similar-to-modern ? and the estimated Eocene atmospheric CO2 of ~1000 ppm. During the Cretaceous, at ~4 times modern [Ca2+], ocean buffering would have been at a minimum. Overall, during times of high seawater [Ca2+], CaCO3 saturation, pH, and atmospheric CO2 were more susceptible to perturbations of the global carbon cycle. For example, given both Eocene and Cretaceous seawater [Ca2+] and [Mg2+], a doubling of atmospheric CO2 would require less carbon addition to the ocean/atmosphere system than under modern seawater composition. Moreover, increasing seawater buffering since the Cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and CO2 concentration mechanisms that aid photosynthesis.

  17. Molecular Structure of Adenosine

    NSDL National Science Digital Library

    2002-08-19

    Adenosine is an endogenous nucleoside occurring in all of the cells of the body. It is chemically 6-amino-9-B-D-ribofuanosyl-9-H-purine and has the chemical formula of C10H13N5O4. Adenosine naturally hydrogen bonds to thymidine by two hydrogen bonds to construct a stable structure. Adenosine is a purine, meaning that it is a single ring structure. A carbon sugar ring attaches to nitrogen in the base to form an N-glycosylic bond. The nitrogenous bases, which are primarily nonpolar, pack tightly enough to exclude water and form a stable, primarily nonpolar environment in the helix interior.

  18. Glucose enhancement of LDL oxidation is strictly metal ion dependent

    Microsoft Academic Search

    Hiro-Omi Mowri; Balz Frei; John F Keaney Jr.

    2000-01-01

    Recent evidence suggests that lipoprotein oxidation is increased in diabetes, however, the mechanism(s) for such observations are not clear. We examined the effect of glucose on low-density lipoprotein (LDL) oxidation using metal ion–dependent and –independent oxidation systems. Pathophysiological concentrations of glucose (25 mM) enhanced copper-induced LDL oxidation as determined by conjugated diene formation or relative electrophoretic mobility (REM) on agarose

  19. Adenosine and Bone Metabolism

    PubMed Central

    Mediero, Aránzazu; Cronstein, Bruce N.

    2013-01-01

    Bone is a dynamic organ that undergoes continuous remodeling whilst maintaining a balance between bone formation and resorption. Osteoblasts, which synthesize and mineralize new bone, and osteoclasts, the cells that resorb bone, act in concert to maintain bone homeostasis. In recent years, there has been increasing appreciation of purinergic regulation of bone metabolism. Adenosine, released locally, mediates its physiologic and pharmacologic actions via interactions with G-protein coupled receptors and recent work has indicated that these receptors are involved in the regulation of osteoclast differentiation and function, as well as osteoblast differentiation and bone formation. Moreover, adenosine receptors also regulate chondrocyte and cartilage homeostasis. These recent findings underscore the potential therapeutic importance of adenosine receptors in regulating bone physiology and pathology. PMID:23499155

  20. Glucose enhancement of LDL oxidation is strictly metal ion dependent.

    PubMed

    Mowri, H O; Frei, B; Keaney, J F

    2000-11-01

    Recent evidence suggests that lipoprotein oxidation is increased in diabetes, however, the mechanism(s) for such observations are not clear. We examined the effect of glucose on low-density lipoprotein (LDL) oxidation using metal ion-dependent and -independent oxidation systems. Pathophysiological concentrations of glucose (25 mM) enhanced copper-induced LDL oxidation as determined by conjugated diene formation or relative electrophoretic mobility (REM) on agarose gels. Similarly, iron-induced LDL oxidation was stimulated by glucose resulting in 4- to 6-fold greater REM than control incubations without glucose. In contrast, glucose had no effect on metal ion-independent LDL oxidation by aqueous peroxyl radicals. The effect of glucose on metal ion-dependent LDL oxidation was associated with enhanced reduction of metal ions, and in the case of iron-induced LDL oxidation, was completely inhibited by superoxide dismutase. The effect of glucose was mimicked by other reducing sugars, such as fructose and mannose, and the extent to which each sugar enhanced LDL oxidation was closely linked to its metal ion-reducing activity. Thus, promotion of LDL oxidation by glucose is specific for metal ion-dependent oxidation and involves increased metal ion reduction. These results provide one potential mechanism for enhanced LDL oxidation in diabetes. PMID:11063907

  1. Regulation of Inflammation by Adenosine

    PubMed Central

    Haskó, György; Cronstein, Bruce

    2013-01-01

    Adenosine, a purine nucleoside generated by the dephosphorylation of adenine nucleotides, is a potent endogenous physiologic and pharmacologic regulator of many functions. Adenosine was first reported to inhibit the inflammatory actions of neutrophils nearly 30?years ago and since then the role of adenosine and its receptors as feedback regulators of inflammation has been well established. Here we review the effects of adenosine, acting at its receptors, on neutrophil and monocyte/macrophage function in inflammation. Moreover, we review the role of adenosine in mediating the anti-inflammatory effects of methotrexate, the anchor drug in the treatment of Rheumatoid Arthritis and other inflammatory disorders. PMID:23580000

  2. Spectrophotometric Titration of a Mixture of Calcium and Magnesium.

    ERIC Educational Resources Information Center

    Fulton, Robert; And Others

    1986-01-01

    Describes a spectrophotometric titration experiment which uses a manual titration spectrophotometer and manually operated buret, rather than special instrumentation. Identifies the equipment, materials, and procedures needed for the completion of the experiment. Recommends the use of this experiment in introductory quantitative analysis…

  3. Urinary excretion of calcium and magnesium in children

    Microsoft Academic Search

    S. Ghazali; T. M. Barratt

    1974-01-01

    Urine calcium excretion in healthy children was 2·38±0·66 (SD; no. = 52) mg\\/kg per 24 hr and urinary magnesium excretion was 2·82±0·79 (SD; no. = 23). The 24-hour urine calcium excretion could be predicted with reasonable confidence from the calcium\\/creatinine concentration ratio of the second urine specimen passed in the morning. In this specimen the urine calcium\\/creatinine concentration ratio was

  4. Tropical Andean forest derives calcium and magnesium from Saharan dust

    Microsoft Academic Search

    Jens Boy; Wolfgang Wilcke

    2008-01-01

    We quantified base metal deposition to Amazonian montane rain forest in Ecuador between May 1998 and April 2003 and assessed the response of the base metal budget of three forested microcatchments (8–13 ha). There was a strong interannual variation in deposition of Ca [4.4–29 kg ha?1 a?1], Mg [1.6–12], and K [9.8–30]). High deposition changed the Ca and Mg budgets

  5. The taste of calcium and magnesium salts and anionic modifications

    Microsoft Academic Search

    Harry T. Lawless; Frank Rapacki; John Horne; April Hayes

    2003-01-01

    Taste properties of divalent salts are complex. The first study examined the taste profiles of calcium chloride, magnesium chloride and magnesium sulfate. These divalent cation salts were characterized primarily by bitter taste, with additional sensations described as salty, metallic, astringent, sour and sweet, generally in decreasing order of intensity. A second study examined the taste properties of calcium salts other

  6. Adenosine and sleep–wake regulation

    Microsoft Academic Search

    Radhika Basheer; Robert E. Strecker; Mahesh M. Thakkar; Robert W. McCarley

    2004-01-01

    This review addresses three principal questions about adenosine and sleep–wake regulation: (1) Is adenosine an endogenous sleep factor? (2) Are there specific brain regions\\/neuroanatomical targets and receptor subtypes through which adenosine mediates sleepiness? (3) What are the molecular mechanisms by which adenosine may mediate the long-term effects of sleep loss? Data suggest that adenosine is indeed an important endogenous, homeostatic

  7. Extracellular guanosine regulates extracellular adenosine levels

    PubMed Central

    Cheng, Dongmei; Jackson, Travis C.; Verrier, Jonathan D.; Gillespie, Delbert G.

    2013-01-01

    The aim of this investigation was to test the hypothesis that extracellular guanosine regulates extracellular adenosine levels. Rat preglomerular vascular smooth muscle cells were incubated with adenosine, guanosine, or both. Guanosine (30 ?mol/l) per se had little effect on extracellular adenosine levels. Extracellular adenosine levels 1 h after addition of adenosine (3 ?mol/l) were 0.125 ± 0.020 ?mol/l, indicating rapid disposition of extracellular adenosine. Extracellular adenosine levels 1 h after addition of adenosine (3 ?mol/l) plus guanosine (30 ?mol/l) were 1.173 ± 0.061 ?mol/l, indicating slow disposition of extracellular adenosine. Cell injury increased extracellular levels of endogenous adenosine and guanosine, and the effects of cell injury on endogenous extracellular adenosine were modulated by altering the levels of endogenous extracellular guanosine with exogenous purine nucleoside phosphorylase (converts guanosine to guanine) or 8-aminoguanosine (inhibits purine nucleoside phosphorylase). Extracellular guanosine also slowed the disposition of extracellular adenosine in rat preglomerular vascular endothelial cells, mesangial cells, cardiac fibroblasts, and kidney epithelial cells and in human aortic and coronary artery vascular smooth muscle cells and coronary artery endothelial cells. The effects of guanosine on adenosine levels were not mimicked or attenuated by 5-iodotubericidin (adenosine kinase inhibitor), erythro-9-(2-hydroxy-3-nonyl)-adenine (adenosine deaminase inhibitor), 5-aminoimidazole-4-carboxamide (guanine deaminase inhibitor), aristeromycin (S-adenosylhomocysteine hydrolase inhibitor), low sodium (inhibits concentrative nucleoside transporters), S-(4-nitrobenzyl)?6-thioinosine [inhibits equilibrative nucleoside transporter (ENT) type 1], zidovudine (inhibits ENT type 2), or acadesine (known modulator of adenosine levels). Guanosine also increases extracellular inosine, uridine, thymidine, and cytidine, yet decreases extracellular uric acid. In conclusion, extracellular guanosine regulates extracellular adenosine levels. PMID:23242185

  8. Adenosine Receptors and Cancer

    PubMed Central

    Fishman, P.; Bar-Yehuda, S.; Synowitz, M.; Powell, J.D.; Klotz, K.N.; Gessi, S.; Borea, P.A.

    2013-01-01

    The A1, A2A, A2B and A3 G-protein-coupled cell surface adenosine receptors (ARs) are found to be upregulated in various tumor cells. Activation of the receptors by specific ligands, agonists or antagonists, modulates tumor growth via a range of signaling pathways. The A1AR was found to play a role in preventing the development of glioblastomas. This antitumor effect of the A1AR is mediated via tumor-associated microglial cells. Activation of the A2AAR results in inhibition of the immune response to tumors via suppression of T regulatory cell function and inhibition of natural killer cell cytotoxicity and tumor-specific CD4+/CD8+ activity. Therefore, it is suggested that pharmacological inhibition by specific antagonists may enhance immunotherapeutics in cancer therapy. Activation of the A2BAR plays a role in the development of tumors via upregulation of the expression levels of angiogenic factors in microvascular endothelial cells. In contrast, it was evident that activation of A2BAR results in inhibition of ERK1/2 phosphorylation and MAP kinase activity, which are involved in tumor cell growth signals. Finally, A3AR was found to be highly expressed in tumor cells and tissues while low expression levels were noted in normal cells or adjacent tissue. Receptor expression in the tumor tissues was directly correlated to disease severity. The high receptor expression in the tumors was attributed to overexpression of NF-?B, known to act as an A3AR transcription factor. Interestingly, high A3AR expression levels were found in peripheral blood mononuclear cells (PBMCs) derived from tumor-bearing animals and cancer patients, reflecting receptor status in the tumors. A3AR agonists were found to induce tumor growth inhibition, both in vitro and in vivo, via modulation of the Wnt and the NF-?B signaling pathways. Taken together, A3ARs that are abundantly expressed in tumor cells may be targeted by specific A3AR agonists, leading to tumor growth inhibition. The unique characteristics of these A3AR agonists make them attractive as drug candidates. PMID:19639290

  9. Adenosine triphosphate treatment for supraventricular tachycardia in infants

    Microsoft Academic Search

    D. Wolf; G. Rondia; H. Verhaaren; D. Matthys

    1994-01-01

    Adenosine is an endogenous nucleoside acting on coronary perfusion and myocardial conduction. Although the anti-arrhythmic effects of adenosine have been known for decades, interest in the use of adenosine or adenosine triphosphate (ATP- a precursor of adenosine) in termination of supraventricular tachycardia (SVT) has been renewed. We studied the use of Striadyne (ATP and a mixture of other nucleosides including

  10. Guanosine regulates adenosine levels in the kidney

    PubMed Central

    Jackson, Edwin K.; Cheng, Dongmei; Mi, Zaichuan; Gillespie, Delbert G.

    2014-01-01

    Abstract In cell culture, extracellular guanosine increases extracellular adenosine by attenuating the disposition of extracellular adenosine (American Journal of Physiology – Cell Physiology 304: C406–C421, 2013). The goal of this investigation was to determine whether this “guanosine–adenosine mechanism” is operative in an intact organ. Twenty?seven isolated, perfused mouse kidneys were subjected to metabolic poisons (iodoacetate plus 2,4?dinitrophenol) to cause energy depletion and thereby stimulate renal adenosine production. Adenosine levels in the renal venous perfusate increased from a baseline of 36 ± 8 to 499 ± 96, 258 ± 50, and 71 ± 13 nmol/L at 15, 30, and 60 min, respectively, after administering metabolic poisons (% of basal; 1366 ± 229, 715 ± 128, and 206 ± 33, respectively). Changes in renal venous levels of guanosine closely mirrored the time course of changes in adenosine: baseline of 15 ± 2 to 157 ± 13, 121 ± 8, and 50 ± 5 nmol/L at 15, 30, and 60 min, respectively (% of basal; 1132 ± 104, 871 ± 59, and 400 ± 51, respectively). Freeze?clamp experiments in 12 kidneys confirmed that metabolic poisons increased kidney tissue levels of adenosine and guanosine. In eight additional kidneys, we examined the ability of guanosine to reduce the renal clearance of exogenous adenosine; and these experiments revealed that guanosine significantly decreased the renal extraction of adenosine. Because guanosine is metabolized by purine nucleoside phosphorylase (PNPase), in another set of 16 kidneys we examined the effects of 8?aminoguanine (PNPase inhibitor) on renal venous levels of adenosine and inosine (adenosine metabolite). Kidneys treated with 8?aminoguanine showed a more robust increase in both adenosine and inosine in response to metabolic poisons. We conclude that in the intact kidney, guanosine regulates adenosine levels. PMID:24872359

  11. Guanosine regulates adenosine levels in the kidney.

    PubMed

    Jackson, Edwin K; Cheng, Dongmei; Mi, Zaichuan; Gillespie, Delbert G

    2014-05-01

    In cell culture, extracellular guanosine increases extracellular adenosine by attenuating the disposition of extracellular adenosine (American Journal of Physiology - Cell Physiology 304: C406-C421, 2013). The goal of this investigation was to determine whether this "guanosine-adenosine mechanism" is operative in an intact organ. Twenty-seven isolated, perfused mouse kidneys were subjected to metabolic poisons (iodoacetate plus 2,4-dinitrophenol) to cause energy depletion and thereby stimulate renal adenosine production. Adenosine levels in the renal venous perfusate increased from a baseline of 36 ± 8 to 499 ± 96, 258 ± 50, and 71 ± 13 nmol/L at 15, 30, and 60 min, respectively, after administering metabolic poisons (% of basal; 1366 ± 229, 715 ± 128, and 206 ± 33, respectively). Changes in renal venous levels of guanosine closely mirrored the time course of changes in adenosine: baseline of 15 ± 2 to 157 ± 13, 121 ± 8, and 50 ± 5 nmol/L at 15, 30, and 60 min, respectively (% of basal; 1132 ± 104, 871 ± 59, and 400 ± 51, respectively). Freeze-clamp experiments in 12 kidneys confirmed that metabolic poisons increased kidney tissue levels of adenosine and guanosine. In eight additional kidneys, we examined the ability of guanosine to reduce the renal clearance of exogenous adenosine; and these experiments revealed that guanosine significantly decreased the renal extraction of adenosine. Because guanosine is metabolized by purine nucleoside phosphorylase (PNPase), in another set of 16 kidneys we examined the effects of 8-aminoguanine (PNPase inhibitor) on renal venous levels of adenosine and inosine (adenosine metabolite). Kidneys treated with 8-aminoguanine showed a more robust increase in both adenosine and inosine in response to metabolic poisons. We conclude that in the intact kidney, guanosine regulates adenosine levels. PMID:24872359

  12. Xanthines as Adenosine Receptor Antagonists

    Microsoft Academic Search

    Christa E. Müller; Kenneth A. Jacobson

    \\u000a The natural plant alkaloids caffeine and theophylline were the first adenosine receptor (AR) antagonists described in the\\u000a literature. They exhibit micromolar affinities and are non-selective. A large number of derivatives and analogues were subsequently\\u000a synthesized and evaluated as AR antagonists. Very potent antagonists have thus been developed with selectivity for each of\\u000a the four AR subtypes.

  13. 21 CFR 864.7040 - Adenosine triphosphate release assay.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... false Adenosine triphosphate release assay. 864.7040 Section 864.7040 Food...7040 Adenosine triphosphate release assay. (a) Identification. An adenosine triphosphate release assay is a device that measures the...

  14. Genetics Home Reference: Adenosine deaminase deficiency

    MedlinePLUS

    ... providers. American Society of Gene and Cell Therapy: Gene Therapy for Genetic Disorders Baby's First Test: Severe Combined Immunodeficiency Gene Review: Adenosine Deaminase Deficiency Genetic Testing Registry: Severe ...

  15. Clinical application of adenosine and ATP for pain control

    Microsoft Academic Search

    Masakazu Hayashida; Ken-ichi Fukuda; Atsuo Fukunaga

    2005-01-01

    This review summarizes clinical application of adenosine and adenosine 5?-triphosphate (ATP) in pain conditions. Investigations have been performed in patients with acute perioperative pain or chronic neuropathic pain treated with intravenous adenosine or ATP, or intrathecal adenosine. Characteristic central adenosine A1 receptor-mediated pain-relieving effects have been observed after intravenous adenosine infusion in human inflammation\\/sensitization pain models and in patients with

  16. Adenosine-tri-phosphate treatment for supraventricular tachycardia in infants

    Microsoft Academic Search

    D. De Wolf; G. Rondia; H. Verhaaren; D. Matthys

    1994-01-01

    Adenosine is an endogenous nucleoside acting on coronary perfusion and myocardial conduction. Although the anti-arrhythmic effects of adenosine have been known for decades, interest in the use of adenosine or adenosine-tri-phosphate (ATP) (a precursor of adenosine) in termination of supraventricular tachycardia (SVT) has been renewed. We studied the use of striadyne (ATP and a mixture of other nucleosides including adenosine)

  17. Regulation of Atherosclerosis and Associated Risk Factors by Adenosine and Adenosine Receptors

    PubMed Central

    Koupenova, Milka; Johnston-Cox, Hillary; Ravid, Katya

    2013-01-01

    Adenosine is an endogenous metabolite that has an anti-inflammatory effect across the vasculature. Extracellular adenosine activates four G-protein coupled receptors (A1, A3, A2A, and A2B) whose expression varies in different cells and tissues, including the vasculature and blood cells. Higher levels of adenosine are generated during stress, inflammation, and upon tissue damage. Some of the adenosine receptors (AR), such as the A2BAR, are further upregulated following such stresses. This review will discuss the role of adenosine and adenosine receptors in the development of atherosclerosis and some of the risk factors associated with this pathology. These include adenosine receptor-regulated changes in atherosclerosis, blood pressure, thrombosis, and myocardial infarction. PMID:22850979

  18. Adenosine kinase from bovine adrenal medulla.

    PubMed

    Rotllan, P; Miras Portugal, M T

    1985-09-01

    Adenosine kinase from bovine adrenal medulla was purified 1600-fold by using ammonium sulfate precipitation, gel filtration and affinity chromatography. Gel filtration yielded a relative molecular mass around 42000 and Michaelis constants were 0.2 microM for adenosine and 20 microM for MgATP. The enzyme showed a broad specificity for purine nucleoside triphosphate as phosphate donors. Both free Mg2+ and ATP were inhibitors. AMP was a competitive inhibitor with regard to adenosine and a non-competitive inhibitor versus MgATP, while ADP was a uncompetitive inhibitor with regard to adenosine and a non-competitive inhibitor versus MgATP. Adenosine kinase was strongly inhibited by the bis(adenylyl) polyphosphates Ap4A and Ap5A. These compounds inhibited the enzyme competitively versus MgATP (Ki = 0.06 microM for Ap4A and 0.4 microM for Ap5A) and uncompetitively with regard to adenosine. The results of the kinetic analysis suggest an ordered bi-bi mechanism, adenosine being the first substrate. The phosphorylation of adenosine was unaffected in the presence of vanadate ions. PMID:2992963

  19. Adenosine receptor antagonism in acute tacrolimus toxicity

    Microsoft Academic Search

    Gwenn E. McLaughlin; Maria D. Alva; Marcelo Egea

    2006-01-01

    Background. Calcineurin inhibitors induce renal vasoconstriction and oliguria during acute toxicity. We previously demonstrated that the non- specific adenosine receptor antagonist theophylline improved glomerular filtration rate (GFR) and renal blood flow in the setting of acute tacrolimus (TAC) toxicity. This study was undertaken to deter- mine which of the known adenosine receptor sub- types is responsible for the observed effect

  20. Adenosine postsynaptically modulates supraoptic neuronal excitability.

    PubMed

    Ponzio, Todd A; Hatton, Glenn I

    2005-01-01

    Effects of adenosine on the excitability of supraoptic nucleus neurons were investigated in whole cell patch-clamp experiments conducted in horizontal slices of rat hypothalamus. Adenosine (10-100 muM) inhibited all neurons tested by reducing or abolishing spontaneous or evoked discharge. Large hyperpolarizations were seen, averaging -6.08 +/- 0.83 mV below resting membrane potential, and action potential durations were significantly reduced by 134 +/- 41 mus in the presence of 100 muM adenosine. The A(1) receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 1 muM) blocked these effects, whereas the A(1) agonists N(6)-cyclopentyladenosine (CPA) and N(6)-cyclohexyladenosine (CHA) mimicked the actions of adenosine. A(2) receptor contributions to excitability were assessed by application of an A(2) agonist, carboxamidoadenosine (CPCA). This resulted in membrane depolarizations (3.56 +/- 0.65 mV) and maintenance of firing. The presence of endogenous adenosine in the slice was revealed by both the application of the adenosine uptake inhibitor dilazep (1-100 muM), which resulted in a strong inhibition of firing activity, and the application of DPCPX, which induced firing in cells silenced by negative current injection. We tested for postsynaptic actions of adenosine by blocking G protein activation via GDP-beta-S infusion into recorded neurons. Under these conditions, the adenosinergic inhibition of firing and reduction of spike duration were blocked, suggesting the effects were mediated by postsynaptic adenosine receptors. That the effects on excitability could be due to direct activation of adenosine A(1) receptors on supraoptic neurons was further explored immunocytochemically via the co-labeling of magnocellular neurons with polyclonal antibodies raised against the A(1) receptors. It is concluded that adenosine, acting at postsynaptic A(1) receptors, exhibits a powerful inhibitory influence on supraoptic magnocellular activity and is an important endogenous regulator of magnocellular neuroendocrine function. PMID:15356187

  1. Homeostatic Control of Synaptic Activity by Endogenous Adenosine is Mediated by Adenosine Kinase

    PubMed Central

    Diógenes, Maria José; Neves-Tomé, Raquel; Fucile, Sergio; Martinello, Katiuscia; Scianni, Maria; Theofilas, Panos; Lopatá?, Jan; Ribeiro, Joaquim A.; Maggi, Laura; Frenguelli, Bruno G.; Limatola, Cristina; Boison, Detlev; Sebastião, Ana M.

    2014-01-01

    Extracellular adenosine, a key regulator of neuronal excitability, is metabolized by astrocyte-based enzyme adenosine kinase (ADK). We hypothesized that ADK might be an upstream regulator of adenosine-based homeostatic brain functions by simultaneously affecting several downstream pathways. We therefore studied the relationship between ADK expression, levels of extracellular adenosine, synaptic transmission, intrinsic excitability, and brain-derived neurotrophic factor (BDNF)-dependent synaptic actions in transgenic mice underexpressing or overexpressing ADK. We demonstrate that ADK: 1) Critically influences the basal tone of adenosine, evaluated by microelectrode adenosine biosensors, and its release following stimulation; 2) determines the degree of tonic adenosine-dependent synaptic inhibition, which correlates with differential plasticity at hippocampal synapses with low release probability; 3) modulates the age-dependent effects of BDNF on hippocampal synaptic transmission, an action dependent upon co-activation of adenosine A2A receptors; and 4) influences GABAA receptor-mediated currents in CA3 pyramidal neurons. We conclude that ADK provides important upstream regulation of adenosine-based homeostatic function of the brain and that this mechanism is necessary and permissive to synaptic actions of adenosine acting on multiple pathways. These mechanistic studies support previous therapeutic studies and implicate ADK as a promising therapeutic target for upstream control of multiple neuronal signaling pathways crucial for a variety of neurological disorders. PMID:22997174

  2. Halobacterial adenosine triphosphatases and the adenosine triphosphatase from Halobacterium saccharovorum

    NASA Technical Reports Server (NTRS)

    Kristjansson, Hordur; Sadler, Martha H.; Hochstein, Lawrence I.

    1986-01-01

    Membranes prepared from various members of the genus Halobacterium contained a Triton X-l00 activated adenosine triphosphatase. The enzyme from Halobacterium saccharovorum was unstable in solutions of low ionic strength and maximally active in the presence of 3.5 M NaCl. A variety of nucleotide triphosphates was hydrolyzed. MgADP, the product of ATP hydrolysis, was not hydrolyzed and was a competitive inhibitor with respect to MgATP. The enzyme from H. saccharovorum was composed of at least 2 and possibly 4 subunits. The 83-kDa and 60-kDa subunits represented about 90 percent of total protein. The 60-kDa subunit reacted with dicyclohexyl-carbodiimide when inhibition was carried out in an acidic medium. The enzyme from H. saccharovorum, possesses properties of an F(1)F(0) as well as an E(1)E(2) ATPase.

  3. Regulation of cell proliferation by the guanosine–adenosine mechanism: role of adenosine receptors

    PubMed Central

    Jackson, Edwin K; Gillespie, Delbert G

    2013-01-01

    A recent study (American Journal of Physiology – Cell Physiology 304:C406–C421, 2013) suggests that extracellular guanosine increases extracellular adenosine by modifying the disposition of extracellular adenosine (“guanosine–adenosine mechanism”) and that the guanosine–adenosine mechanism is not mediated by classical adenosine transport systems (SLC28 and SLC29 families) nor by classical adenosine-metabolizing enzymes. The present investigation had two aims (1) to test the hypothesis that the “guanosine–adenosine mechanism” affects cell proliferation; and (2) to determine whether the transporters SLC19A1, SLC19A2, SLC19A3, or SLC22A2 (known to carrier guanosine analogs) might be responsible for the guanosine–adenosine mechanism. In the absence of added adenosine, guanosine had little effect on the proliferation of coronary artery vascular smooth muscle cells (vascular conduit cells) or preglomerular vascular smooth muscle cells (vascular resistance cells). However, in the presence of added adenosine (3 or 10 ?mol/L), guanosine (10–100 ?mol/L) decreased proliferation of both cell types, thus resulting in a highly significant (P < 0.000001) interaction between guanosine and adenosine on cell proliferation. The guanosine–adenosine interaction on cell proliferation was abolished by 1,3-dipropyl-8-(p-sulfophenyl)xanthine (adenosine receptor antagonist). Guanosine (30 ?mol/L) increased extracellular levels of adenosine when adenosine (3 ?mol/L) was added to the medium. This effect was not reproduced by high concentrations of methotrexate (100 ?mol/L), thiamine (1000 ?mol/L), chloroquine (1000 ?mol/L), or acyclovir (10,000 ?mol/L), archetypal substrates for SLC19A1, SLC19A2, SLC19A3, and SLC22A2, respectively; and guanosine still increased adenosine levels in the presence of these compounds. In conclusion, the guanosine–adenosine mechanism affects cell proliferation and is not mediated by SLC19A1, SLC19A2, SLC19A3, or SLC22A2. PMID:23956837

  4. Adenosine receptors as drug targets — what are the challenges?

    PubMed Central

    Chen, Jiang-Fan; Eltzschig, Holger K.; Fredholm, Bertil B.

    2014-01-01

    Adenosine signalling has long been a target for drug development, with adenosine itself or its derivatives being used clinically since the 1940s. In addition, methylxanthines such as caffeine have profound biological effects as antagonists at adenosine receptors. Moreover, drugs such as dipyridamole and methotrexate act by enhancing the activation of adenosine receptors. There is strong evidence that adenosine has a functional role in many diseases, and several pharmacological compounds specifically targeting individual adenosine receptors — either directly or indirectly — have now entered the clinic. However, only one adenosine receptor-specific agent — the adenosine A2A receptor agonist regadenoson (Lexiscan; Astellas Pharma) — has so far gained approval from the US Food and Drug Administration (FDA). Here, we focus on the biology of adenosine signalling to identify hurdles in the development of additional pharmacological compounds targeting adenosine receptors and discuss strategies to overcome these challenges. PMID:23535933

  5. Mast Cell Adenosine Receptors Function: A Focus on the A3 Adenosine Receptor and Inflammation

    PubMed Central

    Rudich, Noam; Ravid, Katya; Sagi-Eisenberg, Ronit

    2012-01-01

    Adenosine is a metabolite, which has long been implicated in a variety of inflammatory processes. Inhaled adenosine provokes bronchoconstriction in asthmatics or chronic obstructive pulmonary disease patients, but not in non-asthmatics. This hyper responsiveness to adenosine appears to be mediated by mast cell activation. These observations have marked the receptor that mediates the bronchoconstrictor effect of adenosine on mast cells (MCs), as an attractive drug candidate. Four subtypes (A1, A2a, A2b, and A3) of adenosine receptors have been cloned and shown to display distinct tissue distributions and functions. Animal models have firmly established the ultimate role of the A3 adenosine receptor (A3R) in mediating hyper responsiveness to adenosine in MCs, although the influence of the A2b adenosine receptor was confirmed as well. In contrast, studies of the A3R in humans have been controversial. In this review, we summarize data on the role of different adenosine receptors in mast cell regulation of inflammation and pathology, with a focus on the common and distinct functions of the A3R in rodent and human MCs. The relevance of mouse studies to the human is discussed. PMID:22675325

  6. The partial purification of sodium-plus-potassium ion-dependent adenosine triphosphatase from the gills of Anguilla anguilla and its inhibition by orthovanadate.

    PubMed Central

    Bell, M V; Sargent, J R

    1979-01-01

    1. (Na+ +K+)-dependent ATPase was partially purified from eel gills by a procedure in which the microsomal fraction of crude preparations of chloride cells was selectively extracted with sodium dodecyl sulphate. 2. The microsomal specific activity was increased 2-fold during optimal treatment with detergent. 3. The final preparation (56% pure) had a specific activity of 341 mumol of ATP hydrolysed/h per mg of protein and a turnover number of 3560 min-1. The number of ouabain-binding sties equalled the number of sites phosphorylated by ATP. 4. Both sodium orthovanadate and ouabain inhibited the purified preparation more than the microsomal fraction, vanadate being more effective on an equimolar basis than ouabain. 5. Inhibition by orthovanadate was not enhanced at 28 mM-as compared with 1mM-MgCl2 and was not reversed by beta-adrenergic agonists (cf. Josephson & Cantley (1977) Biochemistry 16, 4572--4578). 6. Of various other metallic oxyanions tested only niobate proved an effective inhibitor of the enzyme although this anion was less effective than orthovanadate. 7. Orthovanadate partially inhibited phosphorylation of the enzyme by ATP in the presence of 28 mM-MgCl2. PMID:39542

  7. Methodologies for the determination of adenosine phosphates

    Microsoft Academic Search

    W. D. Bostick; B. S. Ausmus

    1978-01-01

    Measures of adenosine trichosphate (ATP) and other adenosine phosphate compounds are useful indices of microbial biomass and microbiological activity. Various photometric procedures for the determination of these compounds are compared. A modification in the well-known hexokinase--glucose-6-phosphate dehydrogenase procedure for ATP, which permits a very sensitive kinetic measurement of ATP + ADP (approximately 3.1 pmole), is presented. The procedure utilizes phosphoenol

  8. Role of adenosine receptors in caffeine tolerance

    SciTech Connect

    Holtzman, S.G.; Mante, S.; Minneman, K.P. (Emory Univ. School of Medicine, Atlanta, GA (USA))

    1991-01-01

    Caffeine is a competitive antagonist at adenosine receptors. Receptor up-regulation during chronic drug treatment has been proposed to be the mechanism of tolerance to the behavioral stimulant effects of caffeine. This study reassessed the role of adenosine receptors in caffeine tolerance. Separate groups of rats were given scheduled access to drinking bottles containing plain tap water or a 0.1% solution of caffeine. Daily drug intake averaged 60-75 mg/kg and resulted in complete tolerance to caffeine-induced stimulation of locomotor activity, which could not be surmounted by increasing the dose of caffeine. 5'-N-ethylcarboxamidoadenosine (0.001-1.0 mg/kg) dose dependently decreased the locomotor activity of caffeine-tolerant rats and their water-treated controls but was 8-fold more potent in the latter group. Caffeine (1.0-10 mg/kg) injected concurrently with 5-N-ethylcarboxamidoadenosine antagonized the decreases in locomotor activity comparably in both groups. Apparent pA2 values for tolerant and control rats also were comparable: 5.05 and 5.11. Thus, the adenosine-antagonist activity of caffeine was undiminished in tolerant rats. The effects of chronic caffeine administration on parameters of adenosine receptor binding and function were measured in cerebral cortex. There were no differences between brain tissue from control and caffeine-treated rats in number and affinity of adenosine binding sites or in receptor-mediated increases (A2 adenosine receptor) and decreases (A1 adenosine receptor) in cAMP accumulation. These results are consistent with theoretical arguments that changes in receptor density should not affect the potency of a competitive antagonist. Experimental evidence and theoretical considerations indicate that up-regulation of adenosine receptors is not the mechanism of tolerance to caffeine-induced stimulation of locomotor activity.

  9. Adenosine Receptors, Cystic Fibrosis, and Airway Hydration

    Microsoft Academic Search

    J. P. Clancy

    \\u000a Adenosine (Ado) regulates diverse cellular functions in the lung through its local production, release, metabolism, and subsequent\\u000a stimulation of G-protein-coupled P1 purinergic receptors. The A2B adenosine receptor (A2BAR) is the predominant P1 purinergic receptor isoform expressed in surface airway epithelia, and Ado is an important regulator\\u000a of airway surface liquid (ASL) volume through its activation of the cystic fibrosis transmembrane

  10. Regulation of Lymphocyte Function by Adenosine

    PubMed Central

    Linden, Joel; Cekic, Caglar

    2014-01-01

    Adenosine regulates the interaction between lymphocytes and the vasculature and is important for controlling lymphocyte trafficking in response to tissue injury or infection. Adenosine can blunt the effects of T cell receptor (TCR) activation primarily by activating adenosine A2A receptors (A2AR) and signaling via cyclic AMP and protein kinase A (PKA). PKA reduces proximal TCR signaling by phosphorylation of C-terminal Src kinase (Csk), nuclear factor of activated T cells (NF-AT) and cyclic AMP response element binding protein (CREB). PKA activation can either enhance or inhibit the survival of T cells depending on the strength and duration of signaling. Inducible enzymes such as CD73 and CD39 regulate adenosine formation and degradation in vivo. The extravasation of lymphocytes through blood vessels is influenced by A2AR-mediated suppression of Intercellular Adhesion Molecule 1 (ICAM) expression on lymphocytes and diminished production of IFN? and IFN?-inducible chemokines that are chemotactic to activated lymphocytes. Adenosine also decreases the barrier function of vascular endothelium by activating A2BRs. In sum, adenosine signaling is influenced by tissue inflammation and injury through induction of receptors and enzymes and has generally inhibitory effects on lymphocyte migration into inflamed tissues due to PKA-mediated effects on adhesion molecules, IFN? production and endothelial barrier function. PMID:22772752

  11. Adenosine hypothesis of schizophrenia –opportunities for pharmacotherapy

    PubMed Central

    Boison, Detlev; Singer, Philipp; Shen, Hai-Ying; Feldon, Joram; Yee, Benjamin K.

    2011-01-01

    Pharmacotherapy of schizophrenia based on the dopamine hypothesis remains unsatisfactory for the negative and cognitive symptoms of the disease. Enhancing N-methyl-d-aspartate receptors (NMDAR) function is expected to alleviate such persistent symptoms, but successful development of novel clinically effective compounds remains challenging. Adenosine is a homeostatic bioenergetic network modulator that is able to affect complex networks synergistically at different levels (receptor dependent pathways, biochemistry, bioenergetics, and epigenetics). By affecting brain dopamine and glutamate activities it represents a promising candidate for restoring the functional imbalance in these neurotransmitter systems believed to underlie the genesis of schizophrenia symptoms, as well as restoring homeostasis of bioenergetics. Suggestion of an adenosine hypothesis of schizophrenia further posits that adenosinergic dysfunction might contribute to the emergence of multiple neurotransmitter dysfunctionscharacteristic of schizophrenia via diverse mechanisms. Given the importance of adenosine in early brain development and regulation of brain immune response, it also bears direct relevance to the aetiology of schizophrenia. Here, we provide an overview of the rationale and evidence in support of the therapeutic potential of multiple adenosinergic targets, including the high-affinity adenosine receptors (A1R and A2AR), and the regulatory enzyme adenosine kinase (ADK). Key preliminary clinical data and preclinical findings are reviewed. PMID:21315743

  12. Adenosine Signalling and Function in Glial Cells

    PubMed Central

    Boison, Detlev; Chen, Jiang-Fan; Fredholm, Bertil B.

    2009-01-01

    Despite major advances in a variety of neuroscientific research fields, the majority of neurodegenerative and neurological diseases are poorly controlled by currently available drugs, which are largely based on a neurocentric drug design. Research from the past five years has established a central role of glia to determine how neurons function and – consequently – glial dysfunction is implicated in almost every neurodegenerative and neurological disease. Glial cells are key regulators of the brain’s endogenous neuroprotectant and anticonvulsant adenosine. This review will summarize how glial cells contribute to adenosine homeostasis and how glial adenosine receptors affect glial function. We will then move on to discuss how glial cells interact with neurons and the vasculature and outline new methods to study glial function. We will discuss how glial control of adenosine-function affects neuronal cell death and its implications for epilepsy, traumatic brain injury, ischemia, and Parkinson’s disease. Eventually, glial adenosine-modulating drug targets might be an attractive alternative for the treatment of neurodegenerative diseases. There are, however, several major open questions that remain to be tackled. PMID:19763139

  13. Pain-relieving prospects for adenosine receptors and ectonucleotidases

    PubMed Central

    Zylka, Mark J.

    2010-01-01

    Adenosine receptor agonists have potent antinociceptive effects in diverse preclinical models of chronic pain. In contrast, the efficacy of adenosine or adenosine receptor agonists at treating pain in humans is unclear. Two ectonucleotidases that generate adenosine in nociceptive neurons were recently identified. When injected spinally, these enzymes have long-lasting adenosine A1 receptor (A1R)-dependent antinociceptive effects in inflammatory and neuropathic pain models. Furthermore, recent findings indicate that spinal adenosine A2A receptor activation can enduringly inhibit neuropathic pain symptoms. Collectively, these studies suggest the possibility of treating chronic pain in humans by targeting specific adenosine receptor subtypes in anatomically defined regions with agonists or with ectonucleotidases that generate adenosine. PMID:21236731

  14. Adenosine in vertebrate retina: Localization, receptor characterization, and function

    Microsoft Academic Search

    Christine Blazynski; Maria-Thereza R. Perez

    1991-01-01

    1.The uptake of [3H] adenosine into specific populations of cells in the inner retina has been demonstrated. In mammalian retina, the exogenous adenosine that is transported into cells is phosphorylated, thereby maintaining a gradient for transport of the purine into the cell.2.Endogenous stores of adenosine have been demonstrated by localization of cells that are labeled for adenosine-like immunoreactivity. In the

  15. INTERACTIONS OF FLAVONES AND OTHER PHYTOCHEMICALS WITH ADENOSINE RECEPTORS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Adenosine receptors are involved in the homeostasis of the immune, cardiovascular, and central nervous systems, and adenosine agonists/ antagonists exert many similar effects. The affinity of flavonoids to adenosine receptors suggests that a wide range of natural substances in the diet may potentia...

  16. Anesthetic Cardioprotection: The Role of Adenosine

    PubMed Central

    Bonney, Stephanie; Hughes, Kelly; Eckle, Tobias

    2014-01-01

    Brief periods of cardiac ischemia and reperfusion exert a protective effect against subsequent longer ischemic periods, a phenomenon coined ischemic preconditioning. Similar, repeated brief episodes of coronary occlusion and reperfusion at the onset of reperfusion, called post-conditioning, dramatically reduce infarct sizes. Interestingly, both effects can be achieved by the administration of any volatile anesthetic. In fact, cardio-protection by volatile anesthetics is an older phenomenon than ischemic pre- or post-conditioning. Although the mechanism through which anesthetics can mimic ischemic pre- or post-conditioning is still unknown, adenosine generation and signaling are the most redundant triggers in ischemic pre- or postconditioning. In fact, adenosine signaling has been implicated in isoflurane-mediated cardioprotection. Adenosine acts via four receptors designated as A1, A2a, A2b, and A3. Cardioprotection has been associated with all subtypes, although the role of each remains controversial. Much of the controversy stems from the abundance of receptor agonists and antagonists that are, in fact, capable of interacting with multiple receptor subtypes. Recently, more specific receptor agonists and new genetic animal models have become available paving way towards new discoveries. As such, the adenosine A2b receptor was shown to be the only 1 of the adenosine receptors whose cardiac expression is induced by ischemia in both mice and humans and whose function is implicated in ischemic pre- or post-conditioning. In the current review, we will focus on adenosine signaling in the context of anesthetic cardioprotection and will highlight new discoveries, which could lead to new therapeutic concepts to treat myocardial ischemia using anesthetic preconditioning. PMID:24502579

  17. Adenosine metabolism in phytohemagglutinin-stimulated human lymphocytes.

    PubMed Central

    Snyder, F F; Mendelsohn, J; Seegmiller, J E

    1976-01-01

    The association of a human genetic deficiency of adenosine deaminase activity with combined immunodeficiency prompted a study of the effects of adenosine and of inhibition of adenosine deaminase activity on human lymphocyte transformation and a detailed study of adenosine metabolism throughout phytohemagglutinin-induced blastogenesis. The adenosine deaminase inhibitor, coformycin, at a concentration that inhibited adenosine deaminase activity more than 95%, or 50 muM adenosine, did not prevent blastogenesis by criteria of morphology or thymidine incorporation into acid-precipitable material. The combination of coformycin and adenosine, however, substantially reduced both the viable cell count and the incorporation of thymidine into DNA in phytohemagglutinin-stimulated lymphocytes. Incubation of lymphocytes with phytohemagglutinin for 72 h produced a 12-fold increase in the rate of deamination and a 6-fold increase in phosphorylation of adenosine by intact lymphocytes. There was no change in the apparent affinity for adenosine with either deamination or phosphorylation. The increased rates of metabolism, apparent as early as 3 h after addition of mitogen, may be due to increased entry of the nucleoside into stimulated lymphocytes. Increased adenosine metabolism was not due to changes in total enzyme activity; after 72 h in culture, the ratios of specific activities in extracts of stimulated to unstimulated lymphocytes were essentially unchanged for adenosine kinase, 0.92, and decreased for adenosine deaminase, 0.44. As much as 38% of the initial lymphocyte adenosine deaminase activity accumulated extracellularly after a 72-h culture with phytohemagglutinin. In phytohemagglutinin-stimulated lymphocytes, the principal route of adenosine metabolism was phosphorylation at less than 5 muM adenosine, and deamination at concentrations greater than 5 muM. In unstimulated lymphocytes, deamination was the principal route of adenosine metabolism over the range of adenosine concentrations studied (0.5-250 muM). These studies demonstrate the dependence of both the unstimulated and stimulated lymphocyte on adenosine and may account for the observed sensitivity of mitogen-stimulated lymphocytes to the toxic effects of exogenously supplied adenosine in the presence of the adenosine deaminase inhibitor coformycin. A single case of immunodeficiency disease has been reported in association with purine nucleoside phosphorylase deficiency. The catabolism of guanosine was also found to be enhanced in stimulated normal lymphocytes; phosphorolysis of guanosine to guanine by intact lymphocytes increased six fold after 72-h culture with phytohemagglutinin. The specific activity of purine nucleoside phosphorylase in extracts, with guanosine as substrate, was essentially the same in stimulated and unstimulated lymphocytes after 72 h of culture. PMID:956393

  18. Biochemical Characterization of Putative Central Purinergic Receptors by Using 2-chloro[3H]adenosine, a Stable Analog of Adenosine

    Microsoft Academic Search

    Michael Williams; Edwin A. Risley

    1980-01-01

    After pretreatment of rat brain synaptic membranes with adenosine deaminase to remove endogenous adenosine, 2-chloro[3H]adenosine, a stable analog of adenosine, binds to two sites with Kd values of 1.3 and 16 nM and corresponding Bmax values of 207 and 380 fmol\\/mg of protein. Binding is reversible, and the highest density of sites occurs in enriched synaptosomal fractions. In peripheral tissue,

  19. Two distinct adenosine-sensitive sites on adenylate cyclase.

    PubMed Central

    Londos, C; Wolff, J

    1977-01-01

    The effects of adenosine and adenosine analogs on adenylate cyclases from several tissues have been examined. Two adenosine-reactive sites have been identified: (i) the "R" site, occupancy of which usually leads to activation of cyclase and which requires integrity of the ribose ring for activity, and (ii) the "P" site, which mediates inhibition and requires integrity of the purine ring for activity. Biphasic effects of adenosine are explained by the presence of both sites on a single adenylate cyclase. Comparison of these data with those in the literature indicates that adenosine-reactive "P" and "R" sites are present generally. PMID:271970

  20. Haemodynamic deterioration after treatment with adenosine.

    PubMed Central

    Cowell, R. P.; Paul, V. E.; Ilsley, C. D.

    1994-01-01

    A 26 year old woman presented with a narrow complex tachycardia with a rate of 210 beats/min. Adenosine converted this to atrial fibrillation with a rate of 280 beats/min with associated haemodynamic deterioration that needed electrical cardioversion. Images PMID:8043341

  1. Folding Study of Venus Reveals a Strong Ion Dependence of Its Yellow Fluorescence under Mildly Acidic Conditions*S

    E-print Network

    Jackson, Sophie

    Folding Study of Venus Reveals a Strong Ion Dependence of Its Yellow Fluorescence under Mildly- cencethatisrelativelyinsensitivetochangesinpHandionconcen- trations. Here, we present a detailed study of the stability and fold- ing of Venus. By following hydrogen-deuterium exchange of 15 N-labeled Venus using NMR spectroscopy over 13 months, residue

  2. Characterization of adenosine receptors in isolated cerebral arteries of cat.

    PubMed Central

    Edvinsson, L.; Fredholm, B. B.

    1983-01-01

    The effect of some adenosine analogues and xanthine derivatives were studied on isolated cerebral arteries from cats. The adenosine analogues caused an almost complete relaxation of cerebral arteries contracted by prostaglandin F2 alpha (PGF2 alpha, 30 microM). The order of potency was: 5-N-ethylcarboxamide adenosine (NECA) greater than 2-chloroadenosine greater than adenosine greater than L-N6-phenylisopropyl adenosine (L-PIA). The analogue D-PIA was very weak and its maximum effect was small. NECA and L-PIA enhanced [3H]-cyclic AMP accumulation in [3H]-adenine labelled feline pial vessels with similar absolute and relative potency to their relaxant effects. The relaxant effects of adenosine and of NECA were competitively antagonized by 8-phenyl-theophylline (pA2 = 6.5). The effect of theophylline and enprofylline could not be tested in higher concentrations than 30 or 10 microM because they affected the vessels directly. At these concentrations they were essentially inactive as adenosine antagonists. The non-xanthine phosphodiesterase inhibitor rolipram (0.1 and 100 microM) caused a slight but non-significant potentiation of the relaxant effect of adenosine. The results are compatible with the opinion that adenosine relaxes cerebral vessels by an action on adenosine A2-receptors. The effect may be linked to adenylate cyclase and can be antagonized by 8-phenyl-theophylline. PMID:6100842

  3. Involvement of adenosine in the neurobiology of schizophrenia and its therapeutic implications

    Microsoft Academic Search

    Diogo R. Lara; Oscar P. Dall'Igna; Eduardo S. Ghisolfi; Miriam G. Brunstein

    2006-01-01

    Based on the neuromodulatory and homeostatic actions of adenosine, adenosine dysfunction may contribute to the neurobiological and clinical features of schizophrenia. The present model of adenosine dysfunction in schizophrenia takes into consideration the dopamine and glutamate hypotheses, since adenosine exerts neuromodulatory roles on these systems, and proposes that adenosine plays a role in the inhibitory deficit found in schizophrenia. Given

  4. Calcium and magnesium contents and volume of the terminal cisternae in caffeine-treated skeletal muscle

    PubMed Central

    1984-01-01

    (a) The effects of caffeine on the composition and volume of the terminal cisternae (TC) of the sarcoplasmic reticulum (SR) in frog skeletal muscle were determined with rapid freezing, electron microscopy, and electron probe analysis. (b) Caffeine (5 mM) released approximately 65% of the Ca content of the TC in 1 min and 84% after 3 min. The release of Ca from the TC was associated with a highly significant increase in its Mg content. This increase in Mg was not reduced by valinomycin. There was also a small increase in the K content of the TC at 1 min, although not after 3 min of caffeine contracture. (c) On the basis of the increase in Mg content during caffeine contracture and during tetanus (Somlyo, A. V., H. Gonzalez- Serratos, H. Shuman, G. McClellan, and A. P. Somlyo, 1981, J. Cell Biol., 90:577-594), we suggest that both mechanisms of Ca release are associated with an increase in the Ca and Mg permeability of the SR membranes, the two ions possibly moving through a common channel. (d) There was a significant increase in the P content of the TC during caffeine contracture, while in tetanized muscle (see reference above) there was no increase in the P content of the TC. (e) Mitochondrial Ca content was significantly increased (at 1 and at 3 min) during caffeine contracture. Valinomycin (5 microM) blocked this mitochondrial Ca uptake. (f) The sustained Ca release caused by caffeine in situ contrasts with the transient Ca release observed in studies of fragmented SR preparations, and could be explained by mediation of the caffeine-induced Ca release by a second messenger produced more readily in intact muscle than in isolated SR. (g) The TC were not swollen in rapidly frozen, caffeine-treated muscles, in contrast to the swelling of the TC observed in conventionally fixed, caffeine-treated preparation, the latter finding being in agreement with previous studies. (h) The fractional volume of the TC in rapidly frozen control (resting) frog semitendinosus muscles (approximately 2.1%) was less than the volume (approximately 2.5%) after glutaraldehyde-osmium fixation. PMID:6611338

  5. Relationship of Cotton Fiber Calcium and Magnesium Contents on Dye Uptake

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton from a single bale was processed into knit fabrics and prepared for dyeing. Following scouring, fabrics were soaked in either a metal sequestering solution or a water solution, bleached and dyed using 5 dye shades from both reatice and direct dye classes. Results indicate that removal of re...

  6. Effects of calcium and magnesium hardness on acute copper toxicity to juvenile channel catfish, Ictalurus punctatus

    Microsoft Academic Search

    Peter W. Perschbacher; William A. Wurts

    1999-01-01

    Two experiments were conducted to evaluate the effects of calcium or magnesium hardness on the acute toxicity of copper sulfate to juvenile channel catfish (Ictalurus punctatus) in low alkalinity environments. A preliminary bioassay determined the 48-h LC50 of copper sulfate to be 1.25 mg l?1 for juvenile catfish placed in water with calcium hardness and total alkalinity set at 20

  7. Nitrogen and phosphorus leaching as affected by gypsum amendment and exchangeable calcium and magnesium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The movement of N and P from the soil by leaching contributes to losses from agricultural land and represents an important environmental and human health concern. The objective of this study was to evaluate the effect of gypsum amendment and the resultant impact of different levels of exchangeable C...

  8. Effects of calcium and magnesium ions and host viability on growth of bdellovibrios

    Microsoft Academic Search

    J. C.-C. Huang; M. P. Starr

    1973-01-01

    Bdellovibrio spp. strains 6-5-S, 100, 109 (Davis), and A3.12 multiply in the presence of viable but non-proliferating or heat-killed (70\\u000a or 100 C, 10 min; 121 C, 5 min) cells ofSpirillum serpens strain VHL suspended in buffers supplemented with Ca++ and\\/or Mg++. Ca++ (optimal, 2 × 10?3\\u000a m) and Mg++ (optimal, 2 × 10?5\\u000a m) independently stimulate the groth of

  9. The effect of external calcium and magnesium ions on the response of denervated muscle to acetylcholine.

    PubMed Central

    Gordon, T

    1976-01-01

    1. The effect of external Ca and Mg on the membrane depolarization and contracture of rat denervated muscle in response to acetylcholine, ACh, was studied. 2. Raising external Ca concentration reduced the rate of rise and the amplitude of the ACh contracture, and prolonged its time course. 3. Increasing external Ca reduced the membrane depolarization in response to ACh. The dose increment required to elicit depolarization in high Ca concentration increased with external Ca, and was greater for depolarization than for contracture. 4. External Mg was less effect than Ca in reducing ACh depolarization but was more effective in reducing contracture. In contrast to Ca, Mg did not alter the time course of relaxation. 5. It is concluded that external Ca has two opposing effects on the ACh contracture: one of stabilizing the membrane and the other of increasing intracellular Ca concentration. External Mg may interfere with Ca influx and hence reduce contractility. PMID:1263137

  10. Treatment of cooling tower blowdown water containing silica, calcium and magnesium by electrocoagulation.

    PubMed

    Liao, Z; Gu, Z; Schulz, M C; Davis, J R; Baygents, J C; Farrell, J

    2009-01-01

    This research investigated the effectiveness of electrocoagulation using iron and aluminium electrodes for treating cooling tower blowdown (CTB) waters containing dissolved silica (Si(OH)(4)), Ca(2 + ) and Mg(2 + ). The removal of each target species was measured as a function of the coagulant dose in simulated CTB waters with initial pH values of 5, 7, and 9. Experiments were also performed to investigate the effect of antiscaling compounds and coagulation aids on hardness ion removal. Both iron and aluminum electrodes were effective at removing dissolved silica. For coagulant doses < or =3 mM, silica removal was a linear function of the coagulant dose, with 0.4 to 0.5 moles of silica removed per mole of iron or aluminium. Iron electrodes were only 30% as effective at removing Ca(2 + ) and Mg(2 + ) as compared to silica. There was no measurable removal of hardness ions by aluminium electrodes in the absence of organic additives. Phosphonate based antiscaling compounds were uniformly effective at increasing the removal of Ca(2 + ) and Mg(2 + ) by both iron and aluminium electrodes. Cationic and amphoteric polymers used as coagulation aids were also effective at increasing hardness ion removal. PMID:19901466

  11. Nitrogen, phosphorus, potassium, calcium and magnesium release from two compressed fertilizers: column experiments

    NASA Astrophysics Data System (ADS)

    Fernández-Sanjurjo, M. J.; Alvarez-Rodríguez, E.; Núñez-Delgado, A.; Fernández-Marcos, M. L.; Romar-Gasalla, A.

    2014-07-01

    We used soil columns to study nutrients release from two compressed NPK fertilizers. The columns were filled with soil material from the surface horizon of a granitic soil. Tablets of two slow-release NPK fertilizers (11-18-11 or 8-8-16) were placed into the soil, and then water was percolated through the columns in a saturated regime. Percolates were analyzed for N, P, K, Ca and Mg. These nutrients were also determined in soil and fertilizer tablets at the end of the trials. Nutrient concentrations were high in the first percolates, reaching a steady state when 1426 mm water have percolated, which is equivalent to approximately 1.5 years of rainfall in the geographic area. In the whole trial, both tablets lost more than 80% of their initial N, P and K contents. However, K, Ca and Mg were the most leached, whereas N and P were lost in leachates to a lesser extent. Nutrient release was slower from the tablet with composition 8-8-16 than from the 11-18-11 fertilizer. In view of that, the 8-8-16 tablet can be considered more adequate for crops with a nutrient demand sustained over time. At the end of the trial, the effects of these fertilizers on soil chemical parameters were still evident.

  12. Experimental study of aluminum-, calcium-, and magnesium-acetate complexing at 80 degree C

    SciTech Connect

    Fein, J.B. (Illinois State Water Survey, Champaign, IL (USA))

    1991-04-01

    The stabilities of Al-, Ca-, and Mg-acetate complexes were determined separately at 80{degree}C by measuring the solubilities of gibbsite, portlandite, and brucite as functions of acetate concentrations. The experiments were conducted using geologically realistic acetate concentrations in order to observe the acetate complexes that are important in sedimentary basin fluids. The experimental measurements are used to calculate the stoichiometries and thermodynamic properties of the important Al-, Ca-, and Mg-acetate complexes. The data indicate that Al(OAc){sup 2+} and Al(OAc){sup +}{sub 2} are the important Al-acetate complexes in the gibbsite system. Ca(OAc){sup +} and Mg(OAc){sup +} are the dominant acetate complexes in the portlandite and the brucite systems, respectively. The calculated values of the log of the dissociation constants for Al(OAc){sup +}{sub 2}, Al (OAc){sup 2+}, Ca(OAc){sup +}, and Mg(OAc){sup +} are -4.8 {plus minus} 0.2, -2.9 {plus minus} 0.1, -1.2 {plus minus} 0.2, and -1.3 {plus minus} 0.3, respectively. Thermodynamic models that incorporate these results indicate that the presence of acetate in sedimentary basin fluids can not markedly enhance rock porosity through mineral dissolution.

  13. Decadal changes in potassium, calcium, and magnesium in a deciduous forest soil

    SciTech Connect

    Mulholland, Patrick J [ORNL; Johnson, Dale W. [University of Nevada, Reno; Todd Jr, Donald E [ORNL; Trettin, Carl [USDA Forest Service

    2008-01-01

    Decadal changes in soil exchangeable K{sup +}, Ca{sup 2+}, and Mg{sup 2+} concentrations and contents from 1972 to 2004 in eight intensively monitored plots on Walker Branch Watershed were compared with estimates of increments or decrements in vegetation and detritus. The results from these eight plots compared favorably with those from a more extensive set from 24 soil sampling plots sampled in 1972 and 2004. Increases in exchangeable K{sup +} were noted between 1972 and 1982, but few changes were noted between 1982 and 2004 despite significant increments in vegetation and detritus and significant potential losses by leaching. Total K contents of soils in the 0- to 60-cm sampling depth were very large and a slight amount of weathering could have replenished the K{sup +} lost from exchanges sites. With one notable exception, exchangeable Ca{sup 2+} and Mg{sup 2+} concentrations and contents decreased continuously during the sampling period. Decreases in exchangeable Ca{sup 2+} could be attributed mostly to increments in biomass and detritus, whereas decreases in exchangeable Mg{sup 2+} could not and were attributed to leaching. The major exception to these patterns was in the case of exchangeable Ca{sup 2+}, where significant increases were noted in one plot and attributed to Ca release from the decomposition of Ca-rich coarse woody debris from oak (Quercus spp.) mortality. With minor exceptions, soils and changes in soils among the eight intensively sampled core plots were similar to those in a more extensive set of plots distributed across the watershed. This study shows that averaging among plots can mask significant and important spatial patterns in soil change that must be taken into account in assessing long-term trends.

  14. Models of thermospheric sodium, calcium and magnesium at the magnetic equator

    Microsoft Academic Search

    William J McNeil; Shu T Lai; Edmond Murad

    1998-01-01

    In attempting to interpret recent observations of metals in the lower thermosphere, we have developed several comprehensive models. These models explicitly include the deposition of the metal atoms from ablation of cosmic dust, time-dependant chemical reactions, and transport both by diffusion and by electric fields. The modeling presented here focuses on the depletion of the mesospheric column density of calcium

  15. Structures and stability of calcium and magnesium carbonates at mantle pressures

    E-print Network

    Pickard, Chris J.; Needs, Richard J.

    2015-03-02

    al.19. The most stable struc- 6tures of each compound at the relevant pressures are used, as provided by DFT studies. We use the Pa3¯, P42/mnm, and I 4¯2d structures of CO235, the stishovite, CaCl2 and pyrite structures of SiO236, the rocksalt struc...

  16. Effect of Calcium and Magnesium on Phosphatidylserine Membranes: Experiments and All-Atomic Simulations

    PubMed Central

    Martín-Molina, Alberto; Rodríguez-Beas, César; Faraudo, Jordi

    2012-01-01

    It is known that phosphatidylserine (PS?) lipids have a very similar affinity for Ca2+ and Mg2+ cations, as revealed by electrokinetic and stability experiments. However, despite this similar affinity, experimental evidence shows that the presence of Ca2+ or Mg2+ induces very different aggregation behavior for PS? liposomes as characterized by their fractal dimensions. Also, turbidity measurements confirm substantial differences in aggregation behavior depending on the presence of Ca2+ or Mg2+ cations. These puzzling results suggest that although these two cations have a similar affinity for PS? lipids, they induce substantial structural differences in lipid bilayers containing each of these cations. In other words, these cations have strong ion-specific effects on the structure of PS? membranes. This interpretation is supported by all-atomic molecular-dynamics simulations showing that Ca2+ and Mg2+ cations have different binding sites and induce different membrane hydration. We show that although both ions are incorporated deep into the hydrophilic region of the membrane, they have different positions and configurations at the membrane. Absorbed Ca2+ cations present a peak at a distance ?2 nm from the center of the lipid bilayer, and their most probable binding configuration involves two oxygen atoms from each of the charged moieties of the PS molecule (phosphate and carboxyl groups). In contrast, the distribution of absorbed Mg2+ cations has two different peaks, located a few angstroms before and after the Ca2+ peak. The most probable configurations (corresponding to these two peaks) involve binding to two oxygen atoms from carboxyl groups (the most superficial binding peak) or two oxygen atoms from phosphate groups (the most internal peak). Moreover, simulations also show differences in the hydration structure of the membrane: we obtained a hydration of 7.5 and 9 water molecules per lipid in simulations with Ca2+ and Mg2+, respectively. PMID:22824273

  17. An examination of the relationship between calcium and magnesium and hypertension

    E-print Network

    Georghiades, Mary Elizabeth

    1988-01-01

    and Nutrition Examination Survey II (NHANES II) (79). The data for height and weight are not complete, as certain physical measurements could not be done. One subject, confined to a wheelchair, did not have measures taken for height or weight. One subject...

  18. Calcium and magnesium in plant cytokinesis and their antagonism with caffeine

    Microsoft Academic Search

    J. Becerra

    1977-01-01

    Summary The efficiency of caffeine at different concentration on the induction of binucleate cells in onion root-tip was studied. The drug effect is strongly depressed in the Ca++ and\\/or Mg++ presence at half-rate of maximum efficiency (0.04%), about 2 mM). We therefore conclude that both cations must play a role in plant cytokinesis.

  19. Effects of ion pairing with calcium and magnesium on selenate availability to higher plants

    Microsoft Academic Search

    David R. Parker; Kathy R. Tice; David N. Thomason

    1997-01-01

    The effects of solution speciation on the bioavailability of trace metals are well documented, but the role of speciation in the bioavailability of oxyanionic trace elements that may form significant ion pairs with Ca and Mg in saline media has not been investigated. The authors assessed the effects of such ion pairing on the availability of selenate to representative monocotyledonous

  20. A study of the role of calcium and magnesium in casein micellar structure in human milk 

    E-print Network

    Gallaway, Sheila Ann

    1988-01-01

    A STUDY OF THE ROLE OF CALCIUM AND MAGNESIUN IN CASEIN MICELLAR STRUCTURE IN HUNAN MILK A Thesis by SHEILA ANN GALLAWAY Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1988 Major Subject: Nutrition A STUDY OF THE ROLE OF CALCIUM AND MAGNESIUN IN CASEIN MICELLAR STRUCTURE IN HUMAN MILK A Thesis by SHEILA ANN GALLAWAY Approved as to style and content by; C. . Dil (Chair of Committee...

  1. Spatial variability of plant analysis calcium and magnesium levels before and after liming

    Microsoft Academic Search

    David W. Franzen; Ted R. Peck

    1995-01-01

    Plant samples were taken in an 82.5 ft grid at an early and late sampling date in both 1991 and 1992 from a forty acre field in Illinois. Calcium (Ca) and magnesium (Mg) were analyzed on each sample and maps were made showing the levels of each nutrient within the field. Soil pH measurements were also made from each of

  2. Use of Ultrafiltration Probes in Sheep to Collect Interstitial Fluid for Measurement of Calcium and Magnesium

    Microsoft Academic Search

    ELSA M. JANLE; JANICE E. SOJKA

    2000-01-01

    Blood and urine are usually sampled when studying the con- centrations of chemical constituents of the living animal. Drugs, hormones, ions, nutrients, and metabolites or other small mol- ecules are sampled in this way. However, the concentrations obtained may not reflect tissue levels. Concentrations may differ between tissues because of differences in distribution, protein binding, or metabolism. By using ultrafiltration

  3. Adenosine-induced worsening of supraventricular tachycardia.

    PubMed

    Kunnumpuram, Georgey Koshy; Patel, Ashfaq

    2012-01-01

    An approximately 20-year-old to 30-year-old patient presented with a haemodynamically stable supraventricular tachycardia . The patient was managed with intravenous adenosine primarily, with two bolus doses of 6 and 12 mg. This, however, caused a rare paradoxical surge of tachycardia with mild haemodynamic compromise. The patient further required a combination of Metoprolol and Verapamil administration to slow down and reverse the arrhythmia. Following this the patient remained stable with no further episodes till discharge. PMID:23230260

  4. Role of adenosine in oligodendrocyte precursor maturation

    PubMed Central

    Coppi, Elisabetta; Cellai, Lucrezia; Maraula, Giovanna; Dettori, Ilaria; Melani, Alessia; Pugliese, Anna Maria; Pedata, Felicita

    2015-01-01

    Differentiation and maturation of oligodendroglial cells are postnatal processes that involve specific morphological changes correlated with the expression of stage-specific surface antigens and functional voltage-gated ion channels. A small fraction of oligodendrocyte progenitor cells (OPCs) generated during development are maintained in an immature and slowly proliferative or quiescent state in the adult central nervous system (CNS) representing an endogenous reservoir of immature cells. Adenosine receptors are expressed by OPCs and a key role of adenosine in oligodendrocyte maturation has been recently recognized. As evaluated on OPC cultures, adenosine, by stimulating A1 receptors, promotes oligodendrocyte maturation and inhibits their proliferation; on the contrary, by stimulating A2A receptors, it inhibits oligodendrocyte maturation. A1 and A2A receptor-mediated effects are related to opposite modifications of outward delayed rectifying membrane K+ currents (IK) that are involved in the regulation of oligodendrocyte differentiation. Brain A1 and A2A receptors might represent new molecular targets for drugs useful in demyelinating pathologies, such as multiple sclerosis (MS), stroke and brain trauma. PMID:25964740

  5. Adenosine Receptors: The Contributions by John W. Daly

    PubMed Central

    Jacobson, Kenneth A.

    2015-01-01

    John Daly played an important role in defining adenosine receptors as an important target for drug discovery. His systematic work characterized the effects of adenosine analogues on cyclic AMP in the brain that were antagonized by methylxanthines. He also played a decisive role in establishing these receptors as bona fide biochemical entities and contributed to the discovery of receptor heterogeneity. This brief review will cover some of his important early discoveries in the pharmacology and medicinal chemistry of adenosine receptors.

  6. Measurement of plasma adenosine concentration: methodological and physiological considerations

    SciTech Connect

    Gewirtz, H.; Brown, P.; Most, A.S.

    1987-05-01

    This study tested the hypothesis that measurements of plasma adenosine concentration made on samples of blood obtained in dipyridamole and EHNA (i.e., stopping solution) may be falsely elevated as a result of ongoing in vitro production and accumulation of adenosine during sample processing. Studies were performed with samples of anticoagulated blood obtained from anesthesized domestic swine. Adenosine concentration of ultra filtrated plasma was determined by HPLC. The following parameters were evaluated: (i) rate of clearance of (/sup 3/H)adenosine added to plasma, (ii) endogenous adenosine concentration of matched blood samples obtained in stopping solution alone, stopping solution plus EDTA, and perchloric acid (PCA), (iii) plasma and erythrocyte endogenous adenosine concentration in nonhemolyzed samples, and (iv) plasma adenosine concentration of samples hemolyzed in the presence of stopping solution alone or stopping solution plus EDTA. We observed that (i) greater than or equal to 95% of (/sup 3/H)adenosine added to plasma is removed from it by formed elements of the blood in less than 20 s, (ii) plasma adenosine concentration of samples obtained in stopping solution alone is generally 10-fold greater than that of matched samples obtained in stopping solution plus EDTA, (iii) deliberate mechanical hemolysis of blood samples obtained in stopping solution alone resulted in substantial augmentation of plasma adenosine levels in comparison with matched nonhemolyzed specimens--addition of EDTA to stopping solution prevented this, and (iv) adenosine content of blood samples obtained in PCA agreed closely with the sum of plasma and erythrocyte adenosine content of samples obtained in stopping solution plus EDTA.

  7. Adenosine Regulates Tissue Factor Expression on Endothelial Cells

    Microsoft Academic Search

    Hiroshi Deguchi; Hiroyuki Takeya; Hajime Urano; Esteban C Gabazza; Hong Zhou; Koji Suzuki

    1998-01-01

    The aim of this study was to evaluate the inhibitory activity of adenosine on tumor necrosis factor-? (TNF), thrombin-, or phorbol 12-myristate 13-acetate (PMA)-induced tissue factor (TF) expression on human umbilical vein endothelial cells (HUVECs). This inhibitory effect of adenosine was found to be counteracted by the non-selective adenosine receptor (AR) antagonist, 8-(p-sulfophenyl) theophylline. To clarify the role of ARs

  8. Ion-dependent Inactivation of Barium Current through L-type Calcium Channels

    PubMed Central

    Ferreira, Gonzalo; Yi, Jianxun; Ríos, Eduardo; Shirokov, Roman

    1997-01-01

    It is widely believed that Ba2+ currents carried through L-type Ca2+ channels inactivate by a voltage- dependent mechanism similar to that described for other voltage-dependent channels. Studying ionic and gating currents of rabbit cardiac Ca2+ channels expressed in different subunit combinations in tsA201 cells, we found a phase of Ba2+ current decay with characteristics of ion-dependent inactivation. Upon a long duration (20 s) depolarizing pulse, IBa decayed as the sum of two exponentials. The slow phase (? ? 6 s, 21°C) was parallel to a reduction of gating charge mobile at positive voltages, which was determined in the same cells. The fast phase of current decay (? ? 600 ms), involving about 50% of total decay, was not accompanied by decrease of gating currents. Its amplitude depended on voltage with a characteristic U-shape, reflecting reduction of inactivation at positive voltages. When Na+ was used as the charge carrier, decay of ionic current followed a single exponential, of rate similar to that of the slow decay of Ba2+ current. The reduction of Ba2+ current during a depolarizing pulse was not due to changes in the concentration gradients driving ion movement, because Ba2+ entry during the pulse did not change the reversal potential for Ba2+. A simple model of Ca2+-dependent inactivation (Shirokov, R., R. Levis, N. Shirokova, and E. Ríos. 1993. J. Gen. Physiol. 102:1005–1030) robustly accounts for fast Ba2+ current decay assuming the affinity of the inactivation site on the ?1 subunit to be 100 times lower for Ba2+ than Ca2+. PMID:9101404

  9. Adenosine analogs inhibit fighting in isolated male mice

    SciTech Connect

    Palmour, R.M.; Lipowski, C.J.; Simon, C.K.; Ervin, F.R.

    1989-01-01

    The potent adenosine analogs N-ethylcarboxamide adenosine (NECA) and phenylisopropyladenosine (PIA) inhibit fighting and associated agonistic behaviors in isolated male mice. These effects are reversed by methylxanthines; moderate doses of NECA which inhibit fighting have minimal effects on spontaneous locomotor activity. At very low doses, both NECA and PIA increase fighting in parallel with previously reported increases of motor activity. Brain levels of (/sup 3/H)-NECA and (/sup 3/H)-PIA achieved at behaviorally effective doses suggest an involvement of adenosine receptors. The biochemical mechanism of adenosine receptor action with respect to fighting is unknown, but may include neuromodulatory effects on the release of other, more classical neurotransmitters.

  10. Synthesis and Binding Affinity of Homologated Adenosine Analogues as A3 Adenosine Receptor Ligands

    PubMed Central

    Lee, Hyuk Woo; Choi, Won Jun; Jacobson, Kenneth A.; Jeong, Lak Shin

    2015-01-01

    Homologated analogues 3a and 3b of potent and selective A3 adenosine receptor ligands, IB-MECA and dimethyl-IB-MECA were synthesized from commercially available 1-O-acetyl-2,3,5-tri-O-benzoyl-?-d-ribofuranose (4) via Co2(CO)8-catalyzed siloxymethylation as a key step. Unfortunately, homologated analogues 3a and 3b did not show significant binding affinities at three subtypes of adenosine receptors, indicating that free rotation, resulting from homologation, induced unfavorable interactions in the binding site of the receptor maybe due to the presence of many conformations.

  11. Adenosine signaling in normal and sickle erythrocytes and beyond.

    PubMed

    Zhang, Yujin; Xia, Yang

    2012-08-01

    Sickle cell disease (SCD) is a debilitating hemolytic genetic disorder with high morbidity and mortality affecting millions of individuals worldwide. Although SCD was discovered more than a century ago, no effective mechanism-based prevention and treatment are available due to poorly understood molecular basis of sickling, the fundamental pathogenic process of the disease. SCD patients constantly face hypoxia. One of the best-known signaling molecules to be induced under hypoxic conditions is adenosine. Recent studies demonstrate that hypoxia-mediated elevated adenosine signaling plays an important role in normal erythrocyte physiology. In contrast, elevated adenosine signaling contributes to sickling and multiple life threatening complications including tissue damage, pulmonary dysfunction and priapism. Here, we summarize recent research on the role of adenosine signaling in normal and sickle erythrocytes, progression of the disease and therapeutic implications. In normal erythrocytes, both genetic and pharmacological studies demonstrate that adenosine can enhance 2,3-bisphosphoglycerate (2,3-BPG) production via A(2B) receptor (ADORA2B) activation, suggesting that elevated adenosine has an unrecognized role in normal erythrocytes to promote O(2) release and prevent acute ischemic tissue injury. However, in sickle erythrocytes, the beneficial role of excessive adenosine-mediated 2,3-BPG induction becomes detrimental by promoting deoxygenation, polymerization of sickle hemoglobin and subsequent sickling. Additionally, adenosine signaling via the A(2A) receptor (ADORA2A) on invariant natural killer T (iNKT) cells inhibits iNKT cell activation and attenuates pulmonary dysfunction in SCD mice. Finally, elevated adenosine coupled with ADORA2BR activation is responsible for priapism, a dangerous complication seen in SCD. Overall, the research reviewed here reveals a differential role of elevated adenosine in normal erythrocytes, sickle erythrocytes, iNK cells and progression of disease. Thus, adenosine signaling represents a potentially important therapeutic target for the treatment and prevention of disease. PMID:22634345

  12. Adenosine signaling promotes hematopoietic stem and progenitor cell emergence.

    PubMed

    Jing, Lili; Tamplin, Owen J; Chen, Michael J; Deng, Qing; Patterson, Shenia; Kim, Peter G; Durand, Ellen M; McNeil, Ashley; Green, Julie M; Matsuura, Shinobu; Ablain, Julien; Brandt, Margot K; Schlaeger, Thorsten M; Huttenlocher, Anna; Daley, George Q; Ravid, Katya; Zon, Leonard I

    2015-05-01

    Hematopoietic stem cells (HSCs) emerge from aortic endothelium via the endothelial-to-hematopoietic transition (EHT). The molecular mechanisms that initiate and regulate EHT remain poorly understood. Here, we show that adenosine signaling regulates hematopoietic stem and progenitor cell (HSPC) development in zebrafish embryos. The adenosine receptor A2b is expressed in the vascular endothelium before HSPC emergence. Elevated adenosine levels increased runx1(+)/cmyb(+) HSPCs in the dorsal aorta, whereas blocking the adenosine pathway decreased HSPCs. Knockdown of A2b adenosine receptor disrupted scl(+) hemogenic vascular endothelium and the subsequent EHT process. A2b adenosine receptor activation induced CXCL8 via cAMP-protein kinase A (PKA) and mediated hematopoiesis. We further show that adenosine increased multipotent progenitors in a mouse embryonic stem cell colony-forming assay and in embryonic day 10.5 aorta-gonad-mesonephros explants. Our results demonstrate that adenosine signaling plays an evolutionary conserved role in the first steps of HSPC formation in vertebrates. PMID:25870200

  13. Adenosine receptor signaling in the brain immune system

    Microsoft Academic Search

    György Haskó; Pál Pacher; E. Sylvester Vizi; Peter Illes

    2005-01-01

    The brain immune system, which consists mainly of astrocytes, microglia and infiltrating immune cells, is quiescent normally, but it is activated in response to pathophysiological events such as ischemia, trauma, inflammation and infection. Adenosine is an endo- genous purine nucleoside that is generated at sites that are subjected to these 'stressful' conditions. Adenosine interacts with specific G-protein-coupled receptors on astrocytes,

  14. Effect of theophylline on adenosine production in the canine myocardium

    SciTech Connect

    McKenzie, J.E.; Steffen, R.P.; Haddy, F.J.

    1987-01-01

    Adenosine is thought to participate in local regulation of coronary blood flow. However, competitive antagonists of adenosine fail to block myocardial active hyperemia. The authors examined the effect of locally administered theophylline on active hyperemia and myocardial adenosine production during intracoronary isoproterenol infusion in the dog heart. Isoproterenol decreased coronary resistance and increased myocardial adenosine production. Infusion of theophylline at a rate that attenuated the vasodilator response to exogenously administered adenosine failed to attenuate the increase in coronary blood flow produced by isoproterenol. However, theophylline plus isoproterenol production greater increases in myocardial adensine production than isoproterenol alone. The curves relating resistance and adenosine in the presence of theophylline fell to the right of those in the absence of theophylline. These findings suggest that the failure of theophylline to attenuate isoproterenol hyperemia in the dog heart results at least in part from an increase in adenosine concentration at the arteriole to a level beyond that blocked by this competitive antagonist and that adenosine may in fact play a role in isoproterenol-induced active hyperemia.

  15. Electrophysiological effects of adenosine and adenosine triphosphate on sheep Purkinje fibres under normal and simulated ischaemic conditions.

    PubMed Central

    Boachie-Ansah, G.; Kane, K. A.; Parratt, J. R.

    1989-01-01

    1. The electrophysiological effects of adenosine and adenosine triphosphate (ATP) were examined in sheep Purkinje fibres, superfused in vitro with either a normal or a hypoxic, hyperkalaemic and acidotic physiological salt solution (PSS). The ability of adenosine to modify the effects of noradrenaline on action potential characteristics was also investigated. 2. The only statistically significant effects of adenosine (10(-6)-10(4) M) and of ATP (10(-6)-10(-4) M) on normal action potential characteristics were a slight dose-dependent shortening of the action potential by adenosine and a depolarization by ATP, 10(-4) M. 3. Superfusion with a hypoxic, hyperkalaemic and acidotic PSS caused marked reductions in resting membrane potential, upstroke and duration of the action potential. 4. Both adenosine and ATP attenuated the reduction in the rate of rise of the upstroke and the amplitude of the action potential caused by the modified PSS. 5. Adenosine did not alter the noradrenaline-induced effects on automaticity or on action potentials of normal or depressed Purkinje fibres. 6. Adenosine and ATP had electrophysiological effects on Purkinje fibres, exposed to conditions in vitro that mimic mild myocardial ischaemia, that were different from those observed on normally polarized fibres. PMID:2720309

  16. Chaperoning of the A1-Adenosine Receptor by Endogenous Adenosine—An Extension of the Retaliatory Metabolite Concept*

    PubMed Central

    Kusek, Justyna; Yang, Qiong; Witek, Martin; Gruber, Christian W.; Nanoff, Christian; Freissmuth, Michael

    2015-01-01

    Cell-permeable orthosteric ligands can assist folding of G protein–coupled receptors in the endoplasmic reticulum (ER); this pharmacochaperoning translates into increased cell surface levels of receptors. Here we used a folding-defective mutant of human A1-adenosine receptor as a sensor to explore whether endogenously produced adenosine can exert a chaperoning effect. This A1-receptor-Y288 A was retained in the ER of stably transfected human embryonic kidney 293 cells but rapidly reached the plasma membrane in cells incubated with an A1 antagonist. This was phenocopied by raising intracellular adenosine levels with a combination of inhibitors of adenosine kinase, adenosine deaminase, and the equilibrative nucleoside transporter: mature receptors with complex glycosylation accumulated at the cell surface and bound to an A1-selective antagonist with an affinity indistinguishable from the wild-type A1 receptor. The effect of the inhibitor combination was specific, because it did not result in enhanced surface levels of two folding-defective human V2-vasopressin receptor mutants, which were susceptible to pharmacochaperoning by their cognate antagonist. Raising cellular adenosine levels by subjecting cells to hypoxia (5% O2) reproduced chaperoning by the inhibitor combination and enhanced surface expression of A1-receptor-Y288 A within 1 hour. These findings were recapitulated for the wild-type A1 receptor. Taken together, our observations document that endogenously formed adenosine can chaperone its cognate A1 receptor. This results in a positive feedback loop that has implications for the retaliatory metabolite concept of adenosine action: if chaperoning by intracellular adenosine results in elevated cell surface levels of A1 receptors, these cells will be more susceptible to extracellular adenosine and thus more likely to cope with metabolic distress. PMID:25354767

  17. Chaperoning of the A1-adenosine receptor by endogenous adenosine - an extension of the retaliatory metabolite concept.

    PubMed

    Kusek, Justyna; Yang, Qiong; Witek, Martin; Gruber, Christian W; Nanoff, Christian; Freissmuth, Michael

    2015-01-01

    Cell-permeable orthosteric ligands can assist folding of G protein-coupled receptors in the endoplasmic reticulum (ER); this pharmacochaperoning translates into increased cell surface levels of receptors. Here we used a folding-defective mutant of human A1-adenosine receptor as a sensor to explore whether endogenously produced adenosine can exert a chaperoning effect. This A1-receptor-Y(288)A was retained in the ER of stably transfected human embryonic kidney 293 cells but rapidly reached the plasma membrane in cells incubated with an A1 antagonist. This was phenocopied by raising intracellular adenosine levels with a combination of inhibitors of adenosine kinase, adenosine deaminase, and the equilibrative nucleoside transporter: mature receptors with complex glycosylation accumulated at the cell surface and bound to an A1-selective antagonist with an affinity indistinguishable from the wild-type A1 receptor. The effect of the inhibitor combination was specific, because it did not result in enhanced surface levels of two folding-defective human V2-vasopressin receptor mutants, which were susceptible to pharmacochaperoning by their cognate antagonist. Raising cellular adenosine levels by subjecting cells to hypoxia (5% O2) reproduced chaperoning by the inhibitor combination and enhanced surface expression of A1-receptor-Y(288)A within 1 hour. These findings were recapitulated for the wild-type A1 receptor. Taken together, our observations document that endogenously formed adenosine can chaperone its cognate A1 receptor. This results in a positive feedback loop that has implications for the retaliatory metabolite concept of adenosine action: if chaperoning by intracellular adenosine results in elevated cell surface levels of A1 receptors, these cells will be more susceptible to extracellular adenosine and thus more likely to cope with metabolic distress. PMID:25354767

  18. THE ROLE AND REGULATION OF ADENOSINE IN THE CENTRAL NERVOUS SYSTEM

    Microsoft Academic Search

    Thomas V. Dunwiddie; Susan A. Masino

    2001-01-01

    ? Abstract Adenosine is a modulator that has a pervasive and generally inhibitory effect on neuronal activity. Tonic activation of adenosine receptors by adenosine that is normally present in the extracellular space in brain tissue leads to inhibitory effects that appear to be mediated by both adenosine A1 and A2A receptors. Relief from this tonic inhibition by receptor antagonists such

  19. Adenosine 2A receptors in acute kidney injury.

    PubMed

    Vincent, I S; Okusa, M D

    2015-07-01

    Acute kidney injury (AKI) is an important clinical problem that may lead to death and for those who survive, the sequelae of AKI include loss of quality of life, chronic kidney disease and end-stage renal disease. The incidence of AKI continues to rise without clear successes in humans for the pharmacological prevention of AKI or treatment of established AKI. Dendritic cells and macrophages are critical early initiators of innate immunity in the kidney and orchestrate inflammation subsequent to ischaemia-reperfusion injury. These innate cells are the most abundant leucocytes present in the kidney, and they represent a heterogeneous population of cells that are capable of responding to cues from the microenvironment derived from pathogens or endogenous inflammatory mediators such as cytokines or anti-inflammatory mediators such as adenosine. Lymphocyte subsets such as natural killer T cells and Tregs also play roles in regulating ischaemic injury by promoting and suppressing inflammation respectively. Adenosine, produced in response to IR, is generally considered as a protective signalling molecule and elicits its physiological responses through four distinct adenosine receptors. However, its short half-life, lack of specificity and rapid metabolism limit the use of adenosine as a therapeutic agent. These adenosine receptors play various roles in regulating the activity of the aforementioned hematopoietic cells in elevated levels of adenosine such as during hypoxia. This review focuses on the importance of one receptor, the adenosine 2A subtype, in blocking inflammation associated with AKI. PMID:25877257

  20. Role of adenosine signalling and metabolism in ?-cell regeneration

    SciTech Connect

    Andersson, Olov, E-mail: olov.andersson@ki.se

    2014-02-01

    Glucose homeostasis, which is controlled by the endocrine cells of the pancreas, is disrupted in both type I and type II diabetes. Deficiency in the number of insulin-producing ? cells – a primary cause of type I diabetes and a secondary contributor of type II diabetes – leads to hyperglycemia and hence an increase in the need for insulin. Although diabetes can be controlled with insulin injections, a curative approach is needed. A potential approach to curing diabetes involves regenerating the ?-cell mass, e.g. by increasing ?-cell proliferation, survival, neogenesis or transdifferentiation. The nucleoside adenosine and its cognate nucleotide ATP have long been known to affect insulin secretion, but have more recently been shown to increase ?-cell proliferation during homeostatic control and regeneration of the ?-cell mass. Adenosine is also known to have anti-inflammatory properties, and agonism of adenosine receptors can promote the survival of ?-cells in an inflammatory microenvironment. In this review, both intracellular and extracellular mechanisms of adenosine and ATP are discussed in terms of their established and putative effects on ?-cell regeneration. - Highlights: • A potential way to cure diabetes is to regenerate the ?-cell mass by promoting cell survival, proliferation or neogenesis. • Adenosine may promote ?-cell regeneration through several cellular mechanisms. • Adenosine and its cognate nucleotide ATP can each promote ?-cell proliferation. • Do adenosine and ATP interact in promoting ?-cell proliferation?.

  1. Extracellular adenosine controls NKT-cell-dependent hepatitis induction.

    PubMed

    Subramanian, Meenakshi; Kini, Radhika; Madasu, Manasa; Ohta, Akiko; Nowak, Michael; Exley, Mark; Sitkovsky, Michail; Ohta, Akio

    2014-04-01

    Extracellular adenosine regulates inflammatory responses via the A2A adenosine receptor (A2AR). A2AR deficiency results in much exaggerated acute hepatitis, indicating nonredundancy of adenosine-A2AR pathway in inhibiting immune activation. To identify a critical target of immunoregulatory effect of extracellular adenosine, we focused on NKT cells, which play an indispensable role in hepatitis. An A2AR agonist abolished NKT-cell-dependent induction of acute hepatitis by concanavalin A (Con A) or ?-galactosylceramide in mice, corresponding to downregulation of activation markers and cytokines in NKT cells and of NK-cell co-activation. These results show that A2AR signaling can downregulate NKT-cell activation and suppress NKT-cell-triggered inflammatory responses. Next, we hypothesized that NKT cells might be under physiological control of the adenosine-A2AR pathway. Indeed, both Con A and ?-galactosylceramide induced more severe hepatitis in A2AR-deficient mice than in WT controls. Transfer of A2AR-deficient NKT cells into A2AR-expressing recipients resulted in exaggeration of Con A-induced liver damage, suggesting that NKT-cell activation is controlled by endogenous adenosine via A2AR, and this physiological regulatory mechanism of NKT cells is critical in the control of tissue-damaging inflammation. The current study suggests the possibility to manipulate NKT-cell activity in inflammatory disorders through intervention to the adenosine-A2AR pathway. PMID:24448964

  2. Molecular Cloning and Characterization of an Adenosine Receptor: The A3 Adenosine Receptor

    Microsoft Academic Search

    Qun-Yong Zhou; Chuanyu Li; Mark E. Olah; Robert A. Johnson; Gary L. Stiles; Olivier Civelli

    1992-01-01

    We have previously reported the selective amplification of several rat striatal cDNA sequences that encode guanine nucleotide-binding regulatory protein (G protein)-coupled receptors. One of these sequences (R226) exhibited high sequence identity (58%) with the two previously cloned adenosine receptors. A full-length cDNA clone for R226 has been isolated from a rat brain cDNA library. The cDNA clone encodes a protein

  3. Adenosine in the spinal cord and periphery: release and regulation of pain

    Microsoft Academic Search

    Jana Sawynok; Xue Jun Liu

    2003-01-01

    In the central nervous system (CNS), adenosine is an important neuromodulator and regulates neuronal and non-neuronal cellular function (e.g. microglia) by actions on extracellular adenosine A1, A2A, A2B and A3 receptors. Extracellular levels of adenosine are regulated by synthesis, metabolism, release and uptake of adenosine. Adenosine also regulates pain transmission in the spinal cord and in the periphery, and a

  4. Immunosuppression via adenosine receptor activation by adenosine monophosphate released from apoptotic cells

    PubMed Central

    Yamaguchi, Hiroshi; Maruyama, Toshihiko; Urade, Yoshihiro; Nagata, Shigekazu

    2014-01-01

    Apoptosis is coupled with recruitment of macrophages for engulfment of dead cells, and with compensatory proliferation of neighboring cells. Yet, this death process is silent, and it does not cause inflammation. The molecular mechanisms underlying anti-inflammatory nature of the apoptotic process remains poorly understood. In this study, we found that the culture supernatant of apoptotic cells activated the macrophages to express anti-inflammatory genes such as Nr4a and Thbs1. A high level of AMP accumulated in the apoptotic cell supernatant in a Pannexin1-dependent manner. A nucleotidase inhibitor and A2a adenosine receptor antagonist inhibited the apoptotic supernatant-induced gene expression, suggesting AMP was metabolized to adenosine by an ecto-5’-nucleotidase expressed on macrophages, to activate the macrophage A2a adenosine receptor. Intraperitoneal injection of zymosan into Adora2a- or Panx1-deficient mice produced high, sustained levels of inflammatory mediators in the peritoneal lavage. These results indicated that AMP from apoptotic cells suppresses inflammation as a ‘calm down’ signal. DOI: http://dx.doi.org/10.7554/eLife.02172.001 PMID:24668173

  5. Serum adenosine deaminase activity in cutaneous anthrax

    PubMed Central

    Sunnetcioglu, Mahmut; Karadas, Sevdegul; Aslan, Mehmet; Ceylan, Mehmet Resat; Demir, Halit; Oncu, Mehmet Resit; Karahocagil, Mustafa Kas?m; Sunnetcioglu, Aysel; Aypak, Cenk

    2014-01-01

    Background Adenosine deaminase (ADA) activity has been discovered in several inflammatory conditions; however, there are no data associated with cutaneous anthrax. The aim of this study was to investigate serum ADA activity in patients with cutaneous anthrax. Material/Methods Sixteen patients with cutaneous anthrax and 17 healthy controls were enrolled. We measured ADA activity; peripheral blood leukocyte, lymphocyte, neutrophil, and monocyte counts; erythrocyte sedimentation rate; and C reactive protein levels. Results Serum ADA activity was significantly higher in patients with cutaneous anthrax than in the controls (p<0.001). A positive correlation was observed between ADA activity and lymphocyte counts (r=0.589, p=0.021) in the patient group. Conclusions This study suggests that serum ADA could be used as a biochemical marker in cutaneous anthrax. PMID:24997584

  6. Effect of A2B Adenosine Receptor Gene Ablation on Proinflammatory Adenosine Signaling in Mast Cells1

    PubMed Central

    Ryzhov, Sergey; Zaynagetdinov, Rinat; Goldstein, Anna E.; Novitskiy, Sergey V.; Dikov, Mikhail M.; Blackburn, Michael R.; Biaggioni, Italo; Feoktistov, Igor

    2013-01-01

    Pharmacological studies suggest that A2B adenosine receptors mediate proinflammatory effects of adenosine in human mast cells in part by up-regulating production of Th2 cytokines and angiogenic factors. This concept has been recently challenged by the finding that mast cells cultured from bone marrow-derived mast cells (BMMCs) of A2B knockout mice display an enhanced degranulation in response to Fc?RI stimulation. This finding was interpreted as evidence of anti-inflammatory functions of A2B receptors and it was suggested that antagonists with inverse agonist activity could promote activation of mast cells. In this report, we demonstrate that genetic ablation of the A2B receptor protein has two distinct effects on BMMCs, one is the previously reported enhancement of Ag-induced degranulation, which is unrelated to adenosine signaling; the other is the loss of adenosine signaling via this receptor subtype that up-regulates IL-13 and vascular endothelial growth factor secretion. Genetic ablation of A2B receptors had no effect on A3 adenosine receptor-dependent potentiation of Ag-induced degranulation in mouse BMMCs, but abrogated A2B adenosine receptor-dependent stimulation of IL-13 and vascular endothelial growth factor secretion. Adenosine receptor antagonists MRS1706 and DPCPX with known inverse agonist activity at the A2B subtype inhibited IL-13 secretion induced by the adenosine analog NECA, but did not mimic the enhanced Ag-induced degranulation observed in A2B knockout BMMCs. Thus, our study confirmed the proinflammatory role of adenosine signaling via A2B receptors and the anti-inflammatory actions of A2B antagonists in mouse BMMCs. PMID:18490720

  7. 21 CFR 864.7040 - Adenosine triphosphate release assay.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...adenosine triphosphate (ATP) from platelets following aggregation. This measurement is made on platelet-rich plasma using a photometer and a luminescent...Simultaneous measurements of platelet aggregation and ATP release...

  8. 21 CFR 864.7040 - Adenosine triphosphate release assay.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7040 Adenosine triphosphate release assay. (a)...

  9. 21 CFR 864.7040 - Adenosine triphosphate release assay.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7040 Adenosine triphosphate release assay. (a)...

  10. 21 CFR 864.7040 - Adenosine triphosphate release assay.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7040 Adenosine triphosphate release assay. (a)...

  11. PHOTOLABILE A1-ADENOSINE RECEPTOR AGONISTS AS “CAGED” ELECTROPHYSIOLOGICAL PROBES+

    PubMed Central

    Maillard, Michel C.; Arlinghaus, Lauren; Glashofer, Marc; Lee, Kevin S.; Jacobson, Kenneth A.

    2012-01-01

    5'-Ether derivatives of the potent adenosine agonist N6-cyclopentyladenosine (CPA) were designed as “caged” ligands for the activation of A1-adenosine receptors following in situ photolysis. The synthesis involved a 2',3'-diol protection scheme using the acid labile ethoxymethynyl group. Generation of CPA was demonstrated chromatographically and in a bioassay measuring the inhibition of synaptic potentials in the rat hippocampus.

  12. [Sleep-wake regulation by prostaglandin D2 and adenosine].

    PubMed

    Nagata, Nanae; Urade, Yoshihiro

    2012-06-01

    Prostaglandin (PG) D2 and adenosine are potent endogenous somnogens that accumulate in the brain during prolonged wakefulness. Lipocalin-type PGD synthase (L-PGDS) catalyzes the isomerization of PGH2, a common precursor of various prostanoids, to produce PGD2. L-PGDS is localized in the leptomeninges, choroid plexus, and oligodendrocytes of the central nervous system. PGD2 stimulates DP1 receptors localized in the basal forebrain and increases the local extracellular concentration of adenosine, a paracrine signaling molecule, to promote sleep. Adenosine activates adenosine A2A receptor-expressing neurons in the basal forebrain and ventrolateral preoptic area (VLPO) and inhibits adenosine A1 receptor-possessing arousal neurons. Sleep-promoting neurons in the VLPO send inhibitory signals to suppress the histaminergic neurons in the tuberomammillary nucleus (TMN); the histaminergic neurons contribute to arousal through histamine H1 receptors. GABAergic inhibition of TMN is involved in the induction of non-rapid eye movement (non-REM) sleep by PGD2 and adenosine A2A agonists. The neural network between the VLPO and TMN is considered to play a key role in regulation of vigilance states. Administering an L-PGD inhibitor (SeCl4), DP1 antagonist (ONO-4127Na), or adenosine A2A receptor antagonist (caffeine) suppresses both non-REM and REM sleep, indicating that the PGD2-adenosine system is crucial for maintaining physiological sleep. Selective gene-deletion strategies based on Cre/loxP technology and focal RNA interference have been used for silencing the expression of the A2A receptor by local infection with adeno-associated virus carrying Cre-recombinase or short hairpin RNA. The results of these studies have shown that the A2Asubreceptors in the shell region of the nucleus accumbens are responsible for the effect of caffeine on wakefulness. PMID:22647469

  13. Adenosine pathway and cancer: where do we go from here?

    PubMed

    Antonioli, Luca; Haskó, György; Fornai, Matteo; Colucci, Rocchina; Blandizzi, Corrado

    2014-09-01

    Increasing evidence supports the occurrence of an intriguing link between tumor onset and development with the microenvironment in which cancer cells are embedded. In this context, a critical role of CD73, in calibrating the duration, magnitude and composition of adenosine signaling in cancer development and progression, has been identified. Adenosine levels are increased in cancer tissues as the result of genetic alterations that occur during tumor progression. Indeed, a rearrangement of the adenosine metabolic machinery has been described within the neoplastic milieu with the aim of amplifying adenosine generation, thereby creating an immune tolerant microenvironment suitable for tumor onset and development. At the same time, adenosine, through the engagement of receptors expressed on neoplastic cells, finely tunes the growth and dissemination of tumor mass, thus interfering with cancer proliferation, apoptosis and metastasis. Based on current knowledge, an improved understanding of how and to what extent adenosine participates to the molecular mechanisms underlying cancer development and diffusion will pave the way toward new therapeutic advances. The discovery and development of drugs targeted on this system might lead to substantial improvements in the clinical management of various cancers. PMID:24958495

  14. Myocardial perfusion scintigraphy during maximal coronary artery vasodilation with adenosine

    SciTech Connect

    Verani, M.S.; Mahmarian, J.J. (Baylor College of Medicine, Houston, TX (USA))

    1991-05-21

    Pharmacologic coronary vasodilation as an adjunct to thallium-201 myocardial perfusion scintigraphy provides an important alternative form of stress that has been increasingly used in patients unable to perform an exercise stress test. Although dipyridamole has traditionally been used for this purpose, there are several compelling reasons why adenosine may be a preferable agent. First, dipyridamole acts by blocking the reuptake and transport of adenosine, which is the effective substance responsible for coronary vasodilation. Second, exogenous adenosine has a very short half-life (less than 2 seconds), which explains its very short duration of action as well as the brief, self-limiting duration of its side effects. Third, the adenosine infusion is controllable and may be increased or decreased as desired. Fourth, the coronary vasodilation induced by the doses of adenosine we recommend (140 micrograms/kg/min) may be more profound than that induced by the standard dipyridamole dose. Our experience to date, with nearly 1,000 patients studied, shows the adenosine thallium-201 test to be practical and well tolerated, with high sensitivity (87%) and specificity (94%) for detecting coronary artery disease.

  15. Modulation of sensory irritation responsiveness by adenosine and malodorants.

    PubMed

    Willis, Daniel N; Morris, John B

    2013-01-01

    Respiratory tract reflex responses are an important defense mechanism against noxious airborne materials. This study was aimed at defining the effects of adenosine on sensory irritation responsiveness and its role in odorant-irritant interactions. These experiments were aimed at testing the hypothesis that adenosine, through the A2 receptor, enhances trigeminal nerve responses to multiple irritants and that odorants enhance responsiveness to irritants through A2 pathways in the female C57Bl/6 mouse. The adenosine precursor, AMP, immediately and markedly increased the sensory irritation response to capsaicin, cyclohexanone, and styrene, irritants that activate chemosensory nerves through differing receptor pathways. The neuromodulatory effect was blocked by the general adenosine receptor antagonist theophylline and by the A2 receptor-specific antagonist DMPX. Multiple odorants were examined, including R-carvone (spearmint), linalool (lavender), trimethylamine (rotting fish), mercaptoethanol, and ethyl sulfide (stench and rotten eggs). Of these, only mercaptoethanol and ethyl sulfide exhibited neuromodulatory effects, enhancing the sensory irritation response to styrene or cyclohexanone. This effect was blocked by theophylline and DMPX indicating the importance of adenosine A2 receptor pathways in this effect. These results highlight that trigeminal chemosensory responsiveness is not static, but can be quickly modulated by adenosine and select odors resulting in hyperresponsive states. PMID:23162088

  16. Cell type-specific effects of adenosine on cortical neurons.

    PubMed

    van Aerde, Karlijn I; Qi, Guanxiao; Feldmeyer, Dirk

    2015-03-01

    The neuromodulator adenosine is widely considered to be a key regulator of sleep homeostasis and an indicator of sleep need. Although the effect of adenosine on subcortical areas has been previously described, the effects on cortical neurons have not been addressed systematically to date. To that purpose, we performed in vitro whole-cell patch-clamp recordings and biocytin staining of pyramidal neurons and interneurons throughout all layers of rat prefrontal and somatosensory cortex, followed by morphological analysis. We found that adenosine, via the A1 receptor, exerts differential effects depending on neuronal cell type and laminar location. Interneurons and pyramidal neurons in layer 2 and a subpopulation of layer 3 pyramidal neurons that displayed regular spiking were insensitive to adenosine application, whereas other pyramidal cells in layers 3-6 were hyperpolarized (range 1.2-10.8 mV). Broad tufted pyramidal neurons with little spike adaptation showed a small adenosine response, whereas slender tufted pyramidal neurons with substantial adaptation showed a bigger response. These studies of the action of adenosine at the postsynaptic level may contribute to the understanding of the changes in cortical circuit functioning that take place between sleep and awakening. PMID:24108800

  17. The A2B adenosine receptor colocalizes with adenosine deaminase in resting parietal cells from gastric mucosa.

    PubMed

    Arin, R M; Vallejo, A I; Rueda, Y; Fresnedo, O; Ochoa, B

    2015-01-01

    The A2B adenosine receptor (A2BR) mediates biological responses to extracellular adenosine in a wide variety of cell types. Adenosine deaminase (ADA) can degrade adenosine and bind extracellularly to adenosine receptors. Adenosine modulates chloride secretion in gastric glands and gastric mucosa parietal cells. A close functional link between surface A2BR and ADA has been found on cells of the immune system, but whether this occurs in the gastrointestinal tract is unknown. The goal of this study was to determine whether A2BR and ADA are coexpressed at the plasma membrane of the acid-secreting gastric mucosa parietal cells. We used isolated gastric parietal cells after purification by centrifugal elutriation. The membrane fraction was obtained by sucrose gradient centrifugation. A2BR mRNA expression was analyzed by RT-PCR. The surface expression of A2BR and ADA proteins was evaluated by Western blotting, flow cytometry and confocal microscopy. Our findings demonstrate that A2BR and ADA are expressed in cell membranes isolated from gastric parietal cells. They show a high degree of colocalization that is particularly evident in the surface of contact between parietal cells. The confocal microscopy data together with flow cytometry analysis suggest a tight association between A2BR and ADA that might be specifically linked to glandular secretory function. PMID:25754047

  18. Adenosine 5'-tetraphosphate and adenosine 5'-pentaphosphate are synthesized by yeast acetyl coenzyme A synthetase.

    PubMed Central

    Guranowski, A; Günther Sillero, M A; Sillero, A

    1994-01-01

    Yeast (Saccharomyces cerevisiae) acetyl coenzyme A (CoA) synthetase (EC 6.2.1.1) catalyzes the synthesis of adenosine 5'-tetraphosphate (P4A) and adenosine 5'-pentaphosphate (p5A) from ATP and tri- or tetrapolyphosphate (P3 or P4), with relative velocities of 7:1, respectively. Of 12 nucleotides tested as potential donors of nucleotidyl moiety, only ATP, adenosine-5'-O-[3-thiotriphosphate], and acetyl-AMP were substrates, with relative velocities of 100, 62, and 80, respectively. The Km values for ATP, P3, and acetyl-AMP were 0.16, 4.7, and 1.8 mM, respectively. The synthesis of p4A could proceed in the absence of exogenous acetate but was stimulated twofold by acetate, with an apparent Km value of 0.065 mM. CoA did not participate in the synthesis of p4A (p5A) and inhibited the reaction (50% inhibitory concentration of 0.015 mM). At pH 6.3, which was optimum for formation of p4A (p5A), the rate of acetyl-CoA synthesis (1.84 mumol mg-1 min-1) was 245 times faster than the rate of synthesis of p4A measured in the presence of acetate. The known formation of p4A (p5A) in yeast sporulation and the role of acetate may therefore be related to acetyl-CoA synthetase. Images PMID:7910605

  19. Effect of adenosine on the growth of human T-lymphocyte leukemia cell line MOLT-4.

    PubMed

    Streitová, Denisa; Weiterová, Lenka; Hofer, Michal; Holá, Jirina; Horváth, Viktor; Kozubík, Alois; Znojil, Vladimír

    2007-09-01

    Adenosine has been observed to suppress the growth of MOLT-4 human leukemia cells in vitro. Changes in the cell cycle, especially increased percentage of cells in S phase, prolonged generation time, and induction of apoptosis at higher adenosine concentrations have been found to be responsible for the growth suppression. Dipyridamole, a drug inhibiting the cellular uptake of adenosine, reversed partially but significantly the adenosine-induced growth suppression. It follows from these results that the action of adenosine on the MOLT-4 cells comprises its cellular uptake and intracellular operation. These findings present new data on anticancer efficacy of adenosine. PMID:17882653

  20. Interactions of flavones and other phytochemicals with adenosine receptors.

    PubMed

    Jacobson, Kenneth A; Moro, Stefano; Manthey, John A; West, Patrick L; Ji, Xiao-Duo

    2002-01-01

    Dietary flavonoids have varied effects on animal cells, such as inhibition of platelet binding and aggregation, inhibition of inflammation, and anticancer properties, but the mechanisms of these effects remain largely unexplained. Adenosine receptors are involved in the homeostasis of the immune, cardiovascular, and central nervous systems, and adenosine agonists/antagonists exert many similar effects. The affinity of flavonoids and other phytochemicals to adenosine receptors suggests that a wide range of natural substances in the diet may potentially block the effects of endogenous adenosine. We used competitive radioligand binding assays to screen flavonoid libraries for affinity and a computational CoMFA analysis of flavonoids to compare steric and electrostatic requirements for ligand recognition at three subtypes of adenosine receptors. Flavone derivatives, such as galangin, were found to bind to three subtypes of adenosine receptors in the microM range. Pentamethylmorin (Ki 2.65 microM) was 14- to 17-fold selective for human A3 receptors than for A1 and A2A receptors. An isoflavone, genistein, was found to bind to A1 receptors. Aurones, such as hispidol (Ki 350 nM) are selective A1 receptor antagonists, and, like genistein, are present in soy. The flavones, chemically optimized for receptor binding, have led to the antagonist, MRS 1067 (3,6-dichloro-2'-(isopropoxy)4'-methylflavone), which is 200-fold more selective for human A3 than A1 receptors. Adenosine receptor antagonism, therefore, may be important in the spectrum of biological activities reported for the flavonoids. PMID:12083460

  1. Detecting adenosine triphosphate in the pericellular space.

    PubMed

    Falzoni, Simonetta; Donvito, Giovanna; Di Virgilio, Francesco

    2013-06-01

    Release of adenosine triphosphate (ATP) into the extracellular space occurs in response to a multiplicity of physiological and pathological stimuli in virtually all cells and tissues. A role for extracellular ATP has been identified in processes as different as neurotransmission, endocrine and exocrine secretion, smooth muscle contraction, bone metabolism, cell proliferation, immunity and inflammation. However, ATP measurement in the extracellular space has proved a daunting task until recently. To tackle this challenge, some years ago, we designed and engineered a novel luciferase probe targeted to and expressed on the outer aspect of the plasma membrane. This novel probe was constructed by appending to firefly luciferase the N-terminal leader sequence and the C-terminal glycophosphatidylinositol anchor of the folate receptor. This chimeric protein, named plasma membrane luciferase, is targeted and localized to the outer side of the plasma membrane. With this probe, we have generated stably transfected HEK293 cell clones that act as an in vitro and in vivo sensor of the extracellular ATP concentration in several disease conditions, such as experimentally induced tumours and inflammation. PMID:23853707

  2. An adenosine nucleoside inhibitor of dengue virus.

    PubMed

    Yin, Zheng; Chen, Yen-Liang; Schul, Wouter; Wang, Qing-Yin; Gu, Feng; Duraiswamy, Jeyaraj; Kondreddi, Ravinder Reddy; Niyomrattanakit, Pornwaratt; Lakshminarayana, Suresh B; Goh, Anne; Xu, Hao Ying; Liu, Wei; Liu, Boping; Lim, Joanne Y H; Ng, Chuan Young; Qing, Min; Lim, Chin Chin; Yip, Andy; Wang, Gang; Chan, Wai Ling; Tan, Hui Pen; Lin, Kai; Zhang, Bo; Zou, Gang; Bernard, Kristen A; Garrett, Christine; Beltz, Karen; Dong, Min; Weaver, Margaret; He, Handan; Pichota, Arkadius; Dartois, Veronique; Keller, Thomas H; Shi, Pei-Yong

    2009-12-01

    Dengue virus (DENV), a mosquito-borne flavivirus, is a major public health threat. The virus poses risk to 2.5 billion people worldwide and causes 50 to 100 million human infections each year. Neither a vaccine nor an antiviral therapy is currently available for prevention and treatment of DENV infection. Here, we report a previously undescribed adenosine analog, NITD008, that potently inhibits DENV both in vitro and in vivo. In addition to the 4 serotypes of DENV, NITD008 inhibits other flaviviruses, including West Nile virus, yellow fever virus, and Powassan virus. The compound also suppresses hepatitis C virus, but it does not inhibit nonflaviviruses, such as Western equine encephalitis virus and vesicular stomatitis virus. A triphosphate form of NITD008 directly inhibits the RNA-dependent RNA polymerase activity of DENV, indicating that the compound functions as a chain terminator during viral RNA synthesis. NITD008 has good in vivo pharmacokinetic properties and is biologically available through oral administration. Treatment of DENV-infected mice with NITD008 suppressed peak viremia, reduced cytokine elevation, and completely prevented the infected mice from death. No observed adverse effect level (NOAEL) was achieved when rats were orally dosed with NITD008 at 50 mg/kg daily for 1 week. However, NOAEL could not be accomplished when rats and dogs were dosed daily for 2 weeks. Nevertheless, our results have proved the concept that a nucleoside inhibitor could be developed for potential treatment of flavivirus infections. PMID:19918064

  3. Effect of Adenosine on Melanogenesis in B16 Cells and Zebrafish

    PubMed Central

    Kim, Mi Yoon; Lee, Hae-Eul; Im, Myung; Lee, Young; Kim, Chang-Deok; Lee, Jeung-Hoon

    2014-01-01

    Background Adenosine is a nucleoside, in which an adenine molecule is attached to a ribofuranose sugar moiety. It can be released into the microenvironment by metabolically active cells, and then fulfills a multitude of functions in regulation of cell proliferation, by activating four subtypes of G protein-coupled adenosine receptors. Objective In this study, we investigated the effect of adenosine on melanogenesis, using B16 melanoma cells. Methods The toxic effects of adenosine on B16 melanoma cells were assessed. To understand the mechanism of the effect of adenosine on melanogenesis in B16 cells, melanin content and tyrosinase activity were measured. Tyrosinase, tyrosinase-related protein-1, and dopachrome tautomerase were monitored by Western blotting. Finally, adenosine was applied to zebrafish embryos, and its in vivo effect on pigmentation investigated. Results At a low concentration, adenosine increased melanin content and tyrosinase activity, while a high dose of adenosine resulted in inhibition of tyrosinase activity. Western blotting showed that adenosine increased tyrosinase protein levels slightly, while high-dose adenosine decreased the expression of tyrosinase. In zebrafish tests, adenosine slightly inhibited body pigmentation. Conclusion In this study, we investigated the effect of adenosine on melanogenesis, using the well-established B16 melanoma cell and zebrafish models. The results suggest that adenosine may inhibit pigmentation, through negative regulation of tyrosinase. PMID:24882976

  4. Prehospital use of adenosine by ambulance services in the Netherlands

    PubMed Central

    Adams, R.; Bon, V.

    2003-01-01

    Background The prehospital use of adenosine in the treatment of supraventricular arrhythmias has recently been implemented in standard ambulance care. However, establishing the origin and nature of the arrhythmia with certainty is an absolute requirement for using adenosine. Methods The ability of the ambulance nurse to predict supraventricular arrhythmias and the necessity of prehospital treatment of arrhythmias in general was evaluated. To do this, cardiologists at the Academic Medical Centre of Amsterdam were consulted and a literature search by means of an electronic search in Pubmed was performed. The search was complemented by a second survey concerning antagonists of adenosine using the keywords: adenosine and theophylline. Moreover, the Ambulance Nurse textbook, the National Protocol for Ambulance Care as well as the explanatory memorandum to the protocol were consulted. Results No strong indication for the prehospital use of adenosine was found, while detrimental effects of the drug can occur. There is no literature showing the ability of ambulance staff to correctly interpret complex cardiac arrhythmias in the Netherlands; the current ambulance protocol does not prevent an incorrect choice of therapy and medication. Conclusion It is strongly advised against using antiarrhythmic medication for the treatment of tachycardias in a prehospital setting if this treatment can be postponed to the hospital environment. PMID:25696211

  5. Selective adenosine-A 2A activation reduces lung reperfusion injury following transplantation

    Microsoft Academic Search

    Scott D Ross; Curtis G Tribble; Joel Linden; James J Gangemi; Brendan C Lanpher; Andrew Y Wang; Irving L Kron

    1999-01-01

    Background: The adenosine-A2A receptor on the neutrophil is responsible for several anti-inflammatory actions. We hypothesized that DWH-146e, a selective adenosine-A2A agonist, would reduce lung reperfusion injury following transplantation.

  6. Adenosine Released by Astrocytes Contributes to Hypoxia-Induced Modulation of Synaptic Transmission

    E-print Network

    Newman, Eric A.

    -specific metabolic inhibitor fluorocitrate (FC) was as effective as the A1 adenosine receptor antagonist CPT a comprehensive definition of gliotrans- mitter, see Volterra and Meldolesi, 2005). Adenosine is a powerful

  7. Subclasses of adenosine receptors in the central nervous system: Interaction with caffeine and related methylxanthines

    Microsoft Academic Search

    John W. Daly; Pamela Butts-Lamb; William Padgett

    1983-01-01

    1.The potencies of caffeine and related methylxanthines as adenosine antagonists were assessed with respect to three apparent subtypes of adenosine receptors in rat brain preparations: (i) the A1-adenosine receptor which binds with a very high affinity the ligand [3H]cyclohexyladenosine (KD, 1 nM) in rat brain membranes; (ii) a ubiquitous low-affinity A2-adenosine receptor which activates cyclic AMP accumulation in rat brain

  8. The role of intraspinal adenosine A 1 receptors in sympathetic regulation

    Microsoft Academic Search

    Shu-Chun Peng; Chiu-Ming Ho; Shung-Tai Ho; Shen-Kou Tsai; Chun-Kuei Su

    2004-01-01

    Using a splanchnic nerve-spinal cord preparation in vitro, we have previously demonstrated that tonic sympathetic activity is generated from the thoracic spinal cord. Here, we sought to determine if adenosine receptors play a role in modulating this spinally generated sympathetic activity. Various adenosine analogs were applied. N6-Cyclopentyladenosine (CPA, adenosine A1 receptor agonist) and 5?-N-ethylcarboxamidoadenosine (NECA, adenosine A1\\/A2 receptor agonist) reduced,

  9. Plasma Concentration of Adenosine during Normoxia and Moderate Hypoxia in Humans

    Microsoft Academic Search

    HIROSHI SAITO; MASAHARU NISHIMURA; HIDEKI SHINANO; HIRONI MAKITA; ICHIZO TSUJINO; EIJI SHIBUYA; FUMIHIKO SATO; KENJI MIYAMOTO; YOSHIKAZU KAWAKAMI

    Adenosine, a purine nucleoside, plays a variety of roles in cardiovascular and ventilatory control, and may be a marker of tissue hypoxia. There is, however, no direct evidence of an increase in plasma or in tissue levels of adenosine during moderate hypoxia in humans. We measured the plasma concen- trations of adenosine in an artery and the median cubital vein

  10. Role of adenosine in the hypoxia-induced hypothermia of toads

    E-print Network

    Tattersall, Glenn

    Role of adenosine in the hypoxia-induced hypothermia of toads LUIZ G. S. BRANCO,1 ALEXANDRE A, Glenn J. Tattersall, and Stephen C. Wood. Role of adenosine in the hypoxia-induced hypothermia of toads remain unclear. We tested the hypothesis that adenosine mediates hypoxia-induced hypothermia in toads

  11. Adenosine induces expression of glial cell line-derived neurotrophic factor (GDNF) in primary rat astrocytes.

    PubMed

    Yamagata, Kazuo; Hakata, Kumiko; Maeda, Aya; Mochizuki, Chiemi; Matsufuji, Hiroshi; Chino, Makoto; Yamori, Yukio

    2007-12-01

    Adenosine, which accumulates rapidly during ischemia due to the breakdown of ATP, has beneficial effects in many tissues. We examined whether adenosine induces the production of glial cell line-derived neurotrophic factor (GDNF) in cultured astrocytes. We evaluated GDNF mRNA expression and GDNF production in astrocytes cultured with adenosine and the adenosine selective receptor agonists 5-(N-ethylcarboxamido) adenosine (NECA), N(6)-cyclopentyladenosine (CPA) and 2-p-(2-carboxyethyl) phenethylamino-5'-N-ethylcarboxamindo-adenosine hydrochloride (CGS 21680). Moreover, we examined the possibility that the expression of GDNF is regulated differently in cultured astrocytes from the stroke-prone spontaneously hypertensive rat (SHRSP) than in those from Wistar Kyoto rats (WKY). In this study, we confirmed that adenosine and the selective A(2B) adenosine receptor agonist NECA induced the expression of GDNF in cultured astrocytes. The A(2B) receptor antagonist alloxazine was able to inhibit the increase in extracellular GDNF produced by adenosine. Furthermore, the amounts of GDNF produced were significantly reduced in astrocytes of the adenosine-treated SHRSP compared with those of WKY. These results indicate that adenosine induces the expression of GDNF, and adenosine A(2B) receptors participate in the regulation of GDNF levels in astrocytes. This expression was attenuated in astrocytes of SHRSP compared with those of WKY. PMID:17920149

  12. Harnessing an endogenous cardioprotective mechanism: Cellular sources and sites of action of adenosine

    Microsoft Academic Search

    Kevin Mullane; David Bullough

    1995-01-01

    Endogenous adenosine is produced by the heart during ischemia-reperfusion as a natural cardioprotectant. The benefits of this local protective mechanism can be harnessed by ischemic preconditioning and amplified by drugs such as acadesine, that augment extracellular adenosine levels specifically during an ischemic event. Classically, adenosine production by cardiomyocytes, and measured in the interstitial fluid, is considered the relevant source of

  13. Neuronal transporter and astrocytic ATP exocytosis underlie activity-dependent adenosine release in the hippocampus

    PubMed Central

    Wall, Mark J; Dale, Nicholas

    2013-01-01

    The neuromodulator adenosine plays an important role in many physiological and pathological processes within the mammalian CNS. However, the precise mechanisms of how the concentration of extracellular adenosine increases following neural activity remain contentious. Here we have used microelectrode biosensors to directly measure adenosine release induced by focal stimulation in stratum radiatum of area CA1 in mouse hippocampal slices. Adenosine release was both action potential and Ca2+ dependent and could be evoked with low stimulation frequencies and small numbers of stimuli. Adenosine release required the activation of ionotropic glutamate receptors and could be evoked by local application of glutamate receptor agonists. Approximately 40% of stimulated-adenosine release occurred by translocation of adenosine via equilibrative nucleoside transporters (ENTs). This component of release persisted in the presence of the gliotoxin fluoroacetate and thus results from the direct release of adenosine from neurons. A reduction of adenosine release in the presence of NTPDase blockers, in slices from CD73?/? and dn-SNARE mice, provides evidence that a component of adenosine release arises from the extracellular metabolism of ATP released from astrocytes. This component of release appeared to have slower kinetics than the direct ENT-mediated release of adenosine. These data suggest that activity-dependent adenosine release is surprisingly complex and, in the hippocampus, arises from at least two distinct mechanisms with different cellular sources. PMID:23713028

  14. Sporulation of the yeast Saccharomyces cerevisiae is accompanied by synthesis of adenosine 5'-tetraphosphate and adenosine 5'-pentaphosphate.

    PubMed Central

    Jakubowski, H

    1986-01-01

    Two-dimensional TLC analysis of 32P-labeled nucleotides extracted from the yeast Saccharomyces cerevisiae reveals that two highly phosphorylated nucleotides are synthesized during sporulation. These nucleotides have been identified as adenosine 5'-tetraphosphate (ppppA) and adenosine 5'-pentaphosphate (pppppA). The synthesis of ppppA and pppppA commences late in sporulation and follows formation of ascospores. The maximum concentration of ppppA and pppppA in sporulating yeast cultures was 2% and 1.5%, respectively, that of ATP. Adenosine 5'-tetraphosphate and 5'-pentaphosphate are unique to this stage of yeast development and are absent in vegetative yeast cells. Since these nucleotides are also absent in asporogenous a/a and alpha/alpha cells, it is reasonable to propose that they are signal nucleotides marking one of the stages of yeast development--i.e., ascospore formation. Images PMID:3517867

  15. Acetate supplementation modulates brain adenosine metabolizing enzymes and adenosine A2A receptor levels in rats subjected to neuroinflammation

    PubMed Central

    2014-01-01

    Background Acetate supplementation reduces neuroglia activation and pro-inflammatory cytokine expression in rat models of neuroinflammation and Lyme neuroborreliosis. Because single-dose glyceryl triacetate (GTA) treatment increases brain phosphocreatine and reduces brain AMP levels, we postulate that GTA modulates adenosine metabolizing enzymes and receptors, which may be a possible mechanism to reduce neuroinflammation. Methods To test this hypothesis, we quantified the ability of GTA to alter brain levels of ecto-5’-nucleotidase (CD73), adenosine kinase (AK), and adenosine A2A receptor using western blot analysis and CD73 activity by measuring the rate of AMP hydrolysis. Neuroinflammation was induced by continuous bacterial lipopolysaccharide (LPS) infusion in the fourth ventricle of the brain for 14 and 28 days. Three treatment strategies were employed, one and two where rats received prophylactic GTA through oral gavage with LPS infusion for 14 or 28 days. In the third treatment regimen, an interventional strategy was used where rats were subjected to 28 days of neuroinflammation, and GTA treatment was started on day 14 following the start of the LPS infusion. Results We found that rats subjected to neuroinflammation for 28 days had a 28% reduction in CD73 levels and a 43% increase in AK levels that was reversed with prophylactic acetate supplementation. CD73 activity in these rats was increased by 46% with the 28-day GTA treatment compared to the water-treated rats. Rats subjected to neuroinflammation for 14 days showed a 50% increase in levels of the adenosine A2A receptor, which was prevented with prophylactic acetate supplementation. Interventional GTA therapy, beginning on day 14 following the induction of neuroinflammation, resulted in a 67% increase in CD73 levels and a 155% increase in adenosine A2A receptor levels. Conclusion These results support the hypothesis that acetate supplementation can modulate brain CD73, AK and adenosine A2A receptor levels, and possibly influence purinergic signaling. PMID:24898794

  16. 2-(1-Hexyn-1-yl)adenosine-induced intraocular hypertension is mediated via K + channel opening through adenosine A 2A receptor in rabbits

    Microsoft Academic Search

    Takashi Konno; Takehiro Uchibori; Akihiko Nagai; Kentaro Kogi; Norimichi Nakahata

    2005-01-01

    The present study was performed to clarify the mechanism of change in intraocular pressure by 2-(1-hexyn-1-yl)adenosine (2-H-Ado), a selective adenosine A2 receptor agonist, in rabbits. 2-H-Ado (0.1%, 50 ?l)-induced ocular hypertension (Emax: 7.7 mm Hg) was inhibited by an adenosine A2A receptor antagonist 1,3,7-trimethyl-8-(3-chlorostyryl)xanthine, ATP-sensitive K+ channel blocker glibenclamide or 5-hydroxydecanoic acid, but not by an adenosine A1 receptor antagonist

  17. Feed-Forward Inhibition of CD73 and Upregulation of Adenosine Deaminase Contribute to the Loss of Adenosine Neuromodulation in Postinflammatory Ileitis

    PubMed Central

    Magalhães-Cardoso, Maria Teresa; Ferreirinha, Fátima; Dias, Ana Sofia; Pelletier, Julie

    2014-01-01

    Purinergic signalling is remarkably plastic during gastrointestinal inflammation. Thus, selective drugs targeting the “purinome” may be helpful for inflammatory gastrointestinal diseases. The myenteric neuromuscular transmission of healthy individuals is fine-tuned and controlled by adenosine acting on A2A excitatory receptors. Here, we investigated the neuromodulatory role of adenosine in TNBS-inflamed longitudinal muscle-myenteric plexus of the rat ileum. Seven-day postinflammation ileitis lacks adenosine neuromodulation, which may contribute to acceleration of gastrointestinal transit. The loss of adenosine neuromodulation results from deficient accumulation of the nucleoside at the myenteric synapse despite the fact that the increases in ATP release were observed. Disparity between ATP outflow and adenosine deficit in postinflammatory ileitis is ascribed to feed-forward inhibition of ecto-5?-nucleotidase/CD73 by high extracellular ATP and/or ADP. Redistribution of NTPDase2, but not of NTPDase3, from ganglion cell bodies to myenteric nerve terminals leads to preferential ADP accumulation from released ATP, thus contributing to the prolonged inhibition of muscle-bound ecto-5?-nucleotidase/CD73 and to the delay of adenosine formation at the inflamed neuromuscular synapse. On the other hand, depression of endogenous adenosine accumulation may also occur due to enhancement of adenosine deaminase activity. Both membrane-bound and soluble forms of ecto-5?-nucleotidase/CD73 and adenosine deaminase were detected in the inflamed myenteric plexus. These findings provide novel therapeutic targets for inflammatory gut motility disorders. PMID:25210228

  18. Quantitative changes in adenosine deaminase isoenzymes in human colorectal adenocarcinomas.

    PubMed

    ten Kate, J; Wijnen, J T; van der Goes, R G; Quadt, R; Griffioen, G; Bosman, F T; Khan, P M

    1984-10-01

    Several reports have suggested that a decrease or absence of adenosine deaminase complexing protein (ADCP) is consistently associated with cancer. However, in other studies, decreased as well as increased ADCP levels were found. In the present study, we investigated ADCP levels in 37 colorectal adenocarcinomas and correlated the results with clinicopathological characteristics in individual carcinomas. The levels of adenosine deaminase (EC 3.5.4.4) and soluble ADCP were determined in tissue samples by, respectively, a spectrophotometric assay and an ADCP specific radioimmunoassay. The values in the individual tumors were compared with their histological characteristics, such as degree of differentiation, nuclear grading, and the preoperative plasma carcinoembryonic antigen levels in the patients. It was found that ADCP was decreased in about a third of the tumors but unaltered or even increased in others. However, there was an overall 40% increase of the adenosine deaminase activity in the tumors compared to normal tissue. There seems to be no simple correlation between any of the clinicopathological parameters and the ADCP or adenosine deaminase levels. Methods detecting ADCP at single cell level might be helpful in exploring its potential use as a cancer-associated marker. PMID:6147190

  19. Adenosine 3',5'Monophosphate in Reproducing and Differentiated Trypanosomes

    Microsoft Academic Search

    James E. Strickler; Curtis L. Patton

    1975-01-01

    Trypanosoma lewisi, a blood protozoan of rats, undergoes differentiation from a rapidly reproducing form to a nonreproducing form in response to the host antibody ablastin. Intracellular concentrations of adenosine 3',5'-monophosphate (cyclic AMP), which has been implicated in controlling reporduction in cultured mammalian cells, was measured in the two developmental forms of T. lewisi. The concentrations were significantly different, and the

  20. Danger Signal Adenosine via Adenosine 2a Receptor Stimulates Growth of P. gingivalis in Primary Gingival Epithelial Cells

    PubMed Central

    Spooner, Ralee; DeGuzman, Jefferson; Lee, KyuLim; Yilmaz, Özlem

    2014-01-01

    SUMMARY Extracellular signaling during inflammation and chronic diseases involves molecules referred to as ‘Danger Signals’ (DS), including the small molecule adenosine. We demonstrate that primary gingival epithelial cells (GECs) express a family of G-protein coupled receptors known as adenosine receptors, including the high affinity receptors A1 and A2a and low affinity receptors A2b and A3. Treatment of Porphyromonas gingivalis-infected GECs with A2a receptor-specific agonist CGS-21680 resulted in elevated intracellular bacterial replication as determined by fluorescence microscopy and antibiotic protection assay. Additionally, A2a receptor antagonism and knockdown via RNA interference significantly reduced metabolically active intracellular P. gingivalis. Furthermore, analysis of anti-inflammatory mediator cyclic AMP (cAMP) following A2a receptor selective agonist CGS-21680 stimulation induced significantly higher levels of cAMP during P. gingivalis infection, indicating adenosine signaling may attenuate inflammatory processes associated with bacterial infection. This study reveals that the GECs express functional A2a receptor and P. gingivalis may utilize the A2a receptor coupled DS Adenosine signaling as a means to establish successful persistence in the oral mucosa, possibly via down-regulation of pro-inflammatory response. PMID:24517244

  1. Evaluation of calcium and magnesium in scalp hair samples of population consuming different drinking water: risk of kidney stone.

    PubMed

    Panhwar, Abdul Haleem; Kazi, Tasneem Gul; Afridi, Hassan Imran; Shaikh, Haffeezur Rehman; Arain, Salma Aslam; Arain, Sadaf Sadia; Brahman, Kapil Dev

    2013-12-01

    The objective of this study was to examine the relationship between calcium (Ca) and magnesium (Mg) in underground water (UGW), bottled mineral water (BMW), and domestic treated water (DTW) with related to risk of kidney stones. The water samples were collected from different areas of Sindh, Pakistan. The scalp hair samples of both genders, age ranged 30-60 years, consuming different types of water, have or have not kidney disorders, were selected. The Ca and Mg concentrations were determined in scalp hair of study subjects and water by flame atomic absorption spectroscopy. The Ca and Mg contents in different types of drinking water, UGW, DTW, and BMW, were found in the range of 79.1-466, 23.7-140, and 45-270 mg/L and 4.43-125, 5.23-39.6, and 7.16-51.3 mg/L, respectively. It was observed that Ca concentration in the scalp hair samples of kidney stone patients consuming different types of drinking water was found to be higher (2,895-4721 ?g/g) while Mg level (84.3-101 ?g/g) was lower as compare to referents subjects (2,490-2,730 ?g/g for Ca, 107-128 ?g/g for Mg) in both genders. The positive correlation was found between Ca and Mg levels in water with related to kidney stone formations in population, especially who consumed underground water. A relative risk and odd ratio were calculated; the relative risk had a strong positive association with incidence of kidney stone which depends on types of drinking water. PMID:24218227

  2. A national survey for cadmium, chromium, copper, lead, zinc, calcium, and magnesium in canadian drinking water supplies

    Microsoft Academic Search

    Jean C. Meranger; Kunnath S. Subramanian; Chantal Chalifoux

    1979-01-01

    A national survey was conducted to determine the levels of cadmium, zinc, magnesium, calcium, lead, chromium, and copper in Canadian drinking water supplies. Samples of raw, treated, and distributed water, obtained from 70 municipalities throughout Canada, were analyzed by atomic absorption spectrometry. Concentrations of trace metals found were essentially the same for all three types of water samples. Median and

  3. Extracellular Calcium and Magnesium, but Not Iron, Are Needed for Optimal Growth of Blastomyces dermatitidis Yeast Form Cells In Vitro

    Microsoft Academic Search

    Steven S. Giles; Charles J. Czuprynski

    2004-01-01

    Iron is an essential nutrient for virtually all microorganisms. Although the human body contains an abundance of iron, the majority is bound to hemoglobin, myoglobin, and cytochromes and thus is not available in a form that can be used to support the growth of microorganisms (16). The availability of ferric iron is further limited by transferrin, a high-affinity iron-bind- ing

  4. Novel sensors for potassium, calcium and magnesium ions based on a silicon transducer as a light-addressable potentiometric sensor

    Microsoft Academic Search

    Atsushi Seki; Kentaro Motoya; Sinya Watanabe; Izumi Kubo

    1999-01-01

    Potentiometric cation sensors using a silicon transducer, light-addressable potentiometric sensor (LAPS) and ion-recognition elements are described, and their performance are discussed. In the silicon transducer, an Al2O3 layer was used as an insulating layer. On the surface of the Al2O3 layer, ion-recognition element such as valinomycin, 18-crown-6 ether, bis[di(n-octylphenyl)phosphato]calcium(II) and ETH1117 were immobilized in the matrix of poly(vinyl chloride) film.

  5. Estimation of calcified tissues hardness via calcium and magnesium ionic to atomic line intensity ratio in laser induced breakdown spectra

    NASA Astrophysics Data System (ADS)

    Abdel-Salam, Z. A.; Galmed, A. H.; Tognoni, E.; Harith, M. A.

    2007-12-01

    Calcified tissues representing three different matrices, namely enamel of human teeth, shells and eggshell, have been studied via Laser Induced Breakdown Spectroscopy (LIBS) technique. The experimental CaII/CaI and MgII/MgI ratios have been measured, in view of the expected correlation between the extent of ionization caused by the laser induced shock wave (SW) and the hardness of the target. The ratio CaII/CaI between the ionic calcium line at 373.69 nm and the neutral line at 428.9 nm is obtained for enamel, shells and eggshell spectra, as well as the ratio MgII/MgI between the ionic magnesium line at 280.26 nm and the neutral line at 285.22 nm. The results show that such spectral lines intensities ratio differs for different matrices and is indeed related to the target materials hardness. It is also found that the MgII/MgI ratio is preferable as an indicator of hardness since these lines are less affected by self absorption. The SW front speed has been measured in the three cases and the obtained values confirm the proportionality to the target hardness. The results here obtained suggest the feasibility of the quantitative estimation of hardness for any other calcified tissues.

  6. Removal of hardness agents, calcium and magnesium, by natural and alkaline modified pumice stones in single and binary systems

    NASA Astrophysics Data System (ADS)

    Sepehr, Mohammad Noori; Zarrabi, Mansur; Kazemian, Hossein; Amrane, Abdeltif; Yaghmaian, Kamiar; Ghaffari, Hamid Reza

    2013-06-01

    Natural and alkaline modified pumice stones were used for the adsorption of water hardening cations, Ca2+ and Mg2+. The adsorbents were characterized using XRF, XRD, SEM and FTIR instrumental techniques. At equilibrium time and for 150 mg/L of a given cation, removal efficiencies were 83% and 94% for calcium and 48% and 73% for magnesium for raw and modified pumices, respectively. The optimal pH for raw and modified pumices were found to be 6.0, leading to the removal of 79 and 96% of calcium and 51 and 93% of magnesium by 10 g/L of raw and modified pumice adsorbents, respectively. Maximum adsorption capacities were 57.27 and 62.34 mg/g for Ca2+ and 44.53 and 56.11 mg/g for Mg2+ on the raw and modified pumices, respectively. Ca2+ and Mg2+ adsorption capacities of the pumice adsorbents decreased in the presence of competing cations. Less than 300 min were needed to achieve 99 and 92% desorption of the adsorbed Ca2+ and 100 and 89% of the adsorbed Mg2+ from the natural and modified pumices, respectively. After treating synthetic water solution simulating an actual water stream with the alkali-modified pumice, total hardness of the treated sample met the required standard for drinking water, namely below 300 mg/L of CaCO3 (297.5 mg/L). The studied pumice adsorbents, and especially the treated pumice, can be therefore considered as promising low cost adsorbents, suitable for the removal of hardness ions from drinking water.

  7. Broiler Litter as a Sole Nutrient Source for Cotton: Nitrogen, Phosphorus, Potassium, Calcium, and Magnesium Concentrations in Plant Parts

    Microsoft Academic Search

    H. Tewolde; K. R. Sistani; D. E. Rowe

    2005-01-01

    The ability of poultry litter to support plant growth by supplying essential plant nutrients in the absence of other sources of the nutrients has not been studied thoroughly. The objectives of this research were to (1) determine the ability of poultry litter, as the sole nutrient source, to provide macronutrients and support growth of cotton (Gossypium hirsutum L.) (2) evaluate

  8. Effect of dietary modifications of calcium and magnesium on reducing solubility of phosphorus in feces from lactating dairy cows.

    PubMed

    Herrera, D; Harris, W G; Nair, V D; Josan, M; Staples, C R

    2010-06-01

    Unintentional movement of P from dairy cow manure to off-farm locations has been an environmental concern for some time. The objective of this study was to evaluate the effects of increasing the dietary concentration and solubility of Ca and the dietary concentration of Mg on lactation performance and solubility of fecal P from lactating dairy cows receiving diets formulated to the same concentration of P (0.38% of dry matter). Eight dietary treatments were evaluated in a 2 x 2 x 2 factorial arrangement involving 2 dietary sources of Ca (CaCO(3) having a moderate solubility of Ca vs. CaCl(2) having an excellent solubility of Ca) and 2 dietary concentrations of Ca (average of 0.64 and 0.95% of dry matter) and Mg (0.25 and 0.4% of dry matter). Twenty-four multiparous cows in mid lactation were fed the 8 diets in three 21-d periods. Dry matter intake and milk production were measured daily, and milk composition was measured on the last 6 milkings of each period. Fecal samples were collected twice a day during the last 5 d of each period, composited within cow, dried at 55 degrees C, and subjected to 10 successive water extractions, and soluble P, Ca, and Mg were determined. Excretion of fecal P (g/d) was correlated positively with intake of P but not with intake of Ca or Mg. A smaller proportion of fecal P was extracted when dietary concentration of Ca increased (37.5 vs. 47.7%) and when CaCl(2) instead of CaCO(3) was fed (40.3 vs. 44.9%). Feeding more Mg reduced water-soluble P in feces but only when CaCO(3) and not CaCl(2) was fed. Increasing the amount of soluble Ca in the diet produced a relatively stable Ca-phosphate compound (hydroxylapatite) in ashed fecal samples, whereas feeding less soluble Ca resulted in a more soluble P phase (Mg-substituted whitlockite). Energy-dispersive X-ray elemental spectroscopy in conjunction with scanning electron microscopy showed spatial association between Ca-Mg and P. A reduction of approximately 5 g of soluble P/cow per d was detected when dietary concentration of Ca increased from an average of 0.64 to 0.95% of dry matter. Supplemental CaCO(3) would be a preferred source of Ca over CaCl(2) because cows fed CaCO(3) tended to produce more 4% fat-corrected milk, more milk fat, and milk with a greater concentration of fat and protein. Current prices would also favor feeding CaCO(3) over CaCl(2). Increasing dietary intakes of Ca and Mg beyond current recommendations may increase formation of insoluble phosphate complexes (Ca-P rather than Ca-Mg-P associations), which result in decreased solubility of P in dairy-cow feces and reduce losses of P from agricultural areas where feces are applied. PMID:20494169

  9. Calcium and magnesium isotope systematics in rivers draining the Himalaya-Tibetan-Plateau region: Lithological or fractionation control?

    Microsoft Academic Search

    Edward T. Tipper; Albert Galy; Mike J. Bickle

    2008-01-01

    In rivers draining the Himalaya-Tibetan-Plateau region, the 26Mg\\/24Mg ratio has a range of 2‰ and the 44Ca\\/42Ca ratio has a range of 0.6‰. The average ?26Mg values of tributaries from each of the main lithotectonic units (Tethyan Sedimentary Series (TSS), High Himalayan Crystalline Series (HHCS) and Lesser Himalayan Series (LHS)) are within 2 standard deviation analytical uncertainty (0.14‰). The consistency

  10. Effects of calcium and magnesium hardness on the fertilization and hatching success of channel X blue hybrid catfish eggs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aquifer used for hybrid catfish hatcheries is less than 10 mg/L of calcium hardness and 1- 25 mg/L of magnesium hardness. Embryonic development is deemed to be the most sensitive stage in the life cycle of a teleost. As egg development takes outside the fish’s body, water hardness is one abioti...

  11. Evaluation of the content and bioaccessibility of iron, zinc, calcium and magnesium from groats, rice, leguminous grains and nuts.

    PubMed

    Suliburska, Joanna; Krejpcio, Zbigniew

    2014-03-01

    The objective of this study was to determine the content and the bioaccessibility of minerals (Fe, Zn, Ca and Mg) in commonly consumed food products, such as cereal groats, rice, leguminous grains and nuts purchased from the local market. The contents of Fe, Zn, Ca and Mg in foods were assayed after dry ashing of samples, while the bioaccessibility of these minerals after enzymatic in vitro digestion, was determined by flame atomic absorption spectrometry. A relatively high content of Fe was found in cashew nuts and green lentils, while cashew nuts and buckwheat groats had the highest concentration of Zn. It was found that the highest amount of macro-elements was generally in nuts, in particular: brazil nuts (Ca and Mg), cashews (Mg) and hazelnuts (Ca and Mg). Concerning the mineral bioaccessibility, the highest values for Fe were obtained in cashew nuts and green lentils (2.8 and 1.7 mg/100 g), for Zn in green lentils (2.1 mg/100 g), for Ca in brazil nuts and shelled pea (32.6 and 29.1 mg/100 g), while for Mg in shelled peas and green lentils (43.4 and 33.9 mg/100 g). Generally, the best sources of bioaccessible minerals seem to be leguminous grains and nuts. PMID:24587537

  12. Antiadrenergic effects of adenosine on His-Purkinje automaticity. Evidence for accentuated antagonism.

    PubMed Central

    Lerman, B B; Wesley, R C; DiMarco, J P; Haines, D E; Belardinelli, L

    1988-01-01

    The effects of adenosine on the human His-Purkinje system (HPS) were studied in nine patients with complete atrioventricular (AV) block. Adenosine had minimal effect on the control HPS cycle length, but in the presence of isoproterenol increased it from 906 +/- 183 to 1,449 +/- 350 ms, P less than 0.001. Aminophylline, a competitive adenosine antagonist, completely abolished this antiadrenergic effect of adenosine. In isolated guinea pig hearts with surgically induced AV block, isoproterenol decreased the HPS rate by 36%, whereas in the presence of 1,3-dipropyl-8-phenyl-xanthine, a potent adenosine antagonist, the HPS rate decreased by 48% and was associated with an increased release of adenosine. Therefore, by blocking the effects of adenosine at the receptor level, the physiologic negative feedback mechanism by which adenosine antagonizes the effects of catecholamines was uncoupled. The results of this study indicate that adenosine's effects on the human HPS are primarily antiadrenergic and are thus consistent with the concept of accentuated antagonism. These effects of adenosine may serve as a counterregulatory metabolic response that improves the O2 supply-demand ratio perturbed by enhanced sympathetic tone. Some catecholamine-mediated ventricular arrhythmias that occur during ischemia or enhanced adrenergic stress may be due to an imbalance in this negative feedback system. PMID:3198769

  13. Adenosine A2A receptor mediates microglial process retraction

    PubMed Central

    Orr, Anna G; Orr, Adam L; Li, Xiao-Jiang; Gross, Robert E; Traynelis, Stephen F

    2009-01-01

    Cell motility drives many biological processes, including immune responses and embryonic development. In the brain, microglia are immune cells that survey and scavenge brain tissue using elaborate motile processes. Motility of these processes is guided by local release of chemoattractants. However, most microglial processes retract during prolonged brain injury or disease. This hallmark of brain inflammation remains unexplained. Here we identified a molecular pathway in mouse and human microglia that converts ATP-driven process extension into process retraction during inflammation. This chemotactic reversal was driven by upregulation of the A2A adenosine receptor coincident with P2Y12 downregulation. Thus, A2A receptor stimulation by adenosine, a breakdown product of extracellular ATP, caused activated microglia to assume their characteristic amoeboid morphology during brain inflammation. Our results indicate that purine nucleotides provide an opportunity for context-dependent shifts in receptor signaling. Thus, we reveal an unexpected chemotactic switch that generates a hallmark feature of CNS inflammation. PMID:19525944

  14. Regulation of somatostatin gene transcription by cyclic adenosine monophosphate

    Microsoft Academic Search

    M. Montminy; P. Brindle; J. Arias; K. Ferreri; R. Armstrong

    1996-01-01

    Cyclic adenosine monophosphate (cAMP) stimulates transcription of somatostatin and other target genes with burstattenuation kinetics. The kinetics of protein kinase (PK-A)—dependent cAMP response element binding protein (CREB) phosphorylation closely parallel the changes in transcription of cAMP-responsive genes by run-on assay. Nuclear translocation of PK-A, visualized by microinjection of fluorescently labeled PK-A holoenzyme, appears to represent the rate-limiting step in CREB

  15. A1 Adenosine Receptor Activation Increases Adipocyte Leptin Secretion

    Microsoft Academic Search

    ALAN M. RICE; JOHN N. FAIN; SCOTT A. RIVKEES

    2000-01-01

    A1 adenosine receptors (A1ARs) are heavily expressed in adipo- cytes and influence fat cell metabolism. Because increasing evidence suggests a role for leptin in mediating appetite and fat cell metabo- lism, we tested whether A1ARs regulate leptin production. Rats were treated with the A1AR agonist N6-cyclopentyladenosine (CPA), and changes in circulating levels of leptin and leptin gene expression were examined.

  16. Adenosine Receptor Antagonists and Retinal Neovascularization in Vivo

    Microsoft Academic Search

    Robert P. Mino; Polyxenie E. Spoerri; Sergio Caballero; Luiz Belardinelli; Italo Biaggioni; Maria B. Grant

    2001-01-01

    PURPOSE. The role of adenosine receptor (AdoR) antagonists in human retinal endothelial cell function in vitro has previously been determined. In this study, efficacy of AdoR antagonist administration in reducing retinal neovascularization was ex- amined in a mouse pup model of oxygen-induced retinopathy. METHODS. A previously described model of oxygen-induced retinal neovascularization in newborn mouse pups was used to examine

  17. Pharmacophore modeling of human adenosine receptor A 2A antagonists

    Microsoft Academic Search

    Zhejun Xu; Feixiong Cheng; Chenxiao Da; Guixia Liu; Yun Tang

    2010-01-01

    Three-dimensional pharmacophore models of human adenosine receptor A2A antagonists were developed based on 23 diverse compounds selected from a large number of A2A antagonists. The best pharmacophore model, Hypo1, contained five features: one hydrogen bond donor , three hydrophobic points\\u000a and one ring aromatic. Its correlation coefficient, root mean square deviation, and cost difference values were 0.955, 0.921\\u000a and 84.4,

  18. Primary Adenosine Monophosphate (AMP) Deaminase Deficiency in a Hypotonic Infant

    Microsoft Academic Search

    Manuel Castro-Gago; Carmen Gómez-Lado; Laura Pérez-Gay; Jesús Eirís-Puñal; Elena Pintos Martínez; Inés García-Consuegra; Miguel Angel Martín

    2011-01-01

    The spectrum of the adenosine monophosphate (AMP) deaminase deficiency ranges from asymptomatic carriers to patients who manifest exercise-induced muscle pain, occasionally rhabdomyolysis, and idiopathic hyperCKemia. However, previous to the introduction of molecular techniques, rare cases with congenital weakness and hypotonia have also been reported. We report a 6-month-old girl with the association of congenital muscle weakness and hypotonia, muscle deficiency

  19. Pathophysiological roles for purines: adenosine, caffeine and urate

    PubMed Central

    Morelli, Micaela; Carta, Anna R; Kachroo, Anil; Schwarzschild, Michael A.

    2011-01-01

    The motor symptoms of Parkinson's disease (PD) are due primarily to the degeneration of the dopaminergic neurons in the nigrostriatal pathway. However, several other brain areas and neurotransmitters other than dopamine such as noradrenaline, 5-hydroxytryptamine and acetylcholine are affected in the disease. Moreover, adenosine because of the extensive interaction of its receptors with the dopaminergic system has been implicated in the in the pathophysiology of the disease. Based on the involvement of these nondopaminergic neurotransmitters in PD and the sometimes severe adverse effects that limit the mainstay use of dopamine-based antiparkinsonian treatments, recent assessments have called for a broadening of therapeutic options beyond the traditional dopaminergic drug arsenal. In this review we describe the interactions between dopamine and adenosine receptors that underpin the preclinical and clinical rationale for pursuing adenosine A2A receptor antagonists as symptomatic and potentially neuroprotective treatment of PD. The review will pay particular attention to recent results regarding specific A2A receptor-receptor interactions and recent findings identifying urate, the end product of purine metabolism, as a novel prognostic biomarker and candidate neuroprotectant in PD. PMID:20696321

  20. Phylogenetic Analysis Reveals a Novel Protein Family Closely Related to Adenosine Deaminase

    Microsoft Academic Search

    Stephanie A. Maier; Julia R. Galellis; Heather E. McDermid

    2005-01-01

    Adenosine deaminase (ADA) is a well-characterized enzyme involved in the depletion of adenosine levels. A group of proteins\\u000a with similarity to ADA, the adenosine deaminase-related growth factors (ADGF; known as CECR1 in vertebrates), has been described\\u000a recently in various organisms. We have determined the phylogenetic relationships of various gene products with significant\\u000a amino acid similarity to ADA using parsimony and

  1. Estimation of skeletal muscle interstitial adenosine during forearm dynamic exercise in humans

    NASA Technical Reports Server (NTRS)

    Costa, F.; Heusinkveld, J.; Ballog, R.; Davis, S.; Biaggioni, I.

    2000-01-01

    It has been proposed that adenosine is a metabolic signal that triggers activation of muscle afferents involved in the exercise pressor reflex. Furthermore, exogenous adenosine induces sympathetic activation that mimics the exercise pressor reflex, and blockade of adenosine receptors inhibits sympathetic activation induced by exercise. Thus, we hypothesize that adenosine is released locally by the muscle during exercise. We used microdialysis probes, placed in the flexor digitorium superficialis muscle, to estimate muscle interstitial adenosine levels in humans. We estimated resting in vivo muscle interstitial adenosine concentrations (0.292+/-0.058 micromol/L, n=4) by perfusing increasing concentrations of adenosine to determine the gradient produced in the dialysate. Muscle interstitial adenosine concentrations increased from 0.23+/-0.04 to 0.82+/-0.14 micromol/L (n=14, P<0.001) during intermittent dynamic exercise at 50% of maximal voluntary contraction. Lactate increased from 0.8+/-0.1 to 2.3+/-0.3 mmol/L (P<0.001). Lower intensity (15% maximal voluntary contraction) intermittent dynamic exercise increased adenosine concentrations from 0.104+/-0.02 to 0.42+/-0.16 micromol/L (n=7). The addition of ischemia to this low level of exercise produced a greater increase in adenosine (from 0.095+/-0.02 to 0.48+/-0.2 micromol/L) compared with nonischemic exercise (0. 095+/-0.02 to 0.25+/-0.12 micromol/L). These results indicate that microdialysis is useful in estimating adenosine concentrations and in reflecting changes in muscle interstitial adenosine during dynamic exercise in humans.

  2. Antagonism of the cytotoxic but not antiviral effects of ara-sangivamycin by adenosine.

    PubMed Central

    Birch, G M; Krawczyk, S H; Townsend, L B; Drach, J C

    1989-01-01

    Inhibition of DNA synthesis by ara-sangivamycin was antagonized by adenosine. The 50% inhibitory concentrations increased 1.6- to 32-fold in the presence of 1.0 to 50 microM adenosine, respectively. In contrast, the inhibition of human cytomegalovirus replication by ara-sangivamycin was not antagonized by as much as 50 microM adenosine. This suggests that different enzymes were responsible for the phosphorylation of ara-sangivamycin in uninfected and infected cells. PMID:2554803

  3. Contraction-induced secretion of VEGF from skeletal muscle cells is mediated by adenosine.

    PubMed

    Høier, Birgitte; Olsen, Karina; Nyberg, Michael; Bangsbo, Jens; Hellsten, Ylva

    2010-09-01

    The role of adenosine and contraction for secretion of vascular endothelial growth factor (VEGF) in skeletal muscle was investigated in human subjects and rat primary skeletal muscle cells. Microdialysis probes were inserted in the thigh muscle of seven male subjects, and dialysate was collected at rest, during infusion of adenosine, and during knee extensor exercise. The dialysate was analyzed for content of VEGF protein and adenosine. The mechanism of VEGF secretion from muscle cells in culture was examined in resting and electrostimulated cells and in response to the adenosine analog NECA and the adenosine A(2A) receptor specific analog CGS-21680. Adenosine receptors A(1), A(2A), and A(2B) were blocked with DPCPX, ZM-241385, and enprofylline, respectively. cAMP-dependent protein kinase A (PKA) and mitogen-activated protein kinase (MAPK) were inhibited by H-89 and PD-98509, respectively. The human experiment showed that adenosine infusion enhanced (P < 0.05) the interstitial concentration of VEGF protein approximately fourfold above baseline. Exercise increased (P < 0.05) the interstitial VEGF concentration approximately sixfold above rest in parallel with an approximately threefold increase in adenosine concentration. In accordance, in cultured muscle cells, NECA and contraction caused secretion of VEGF (P < 0.05). The contraction-induced secretion of VEGF was abolished by the A(2B) antagonist enprofylline and by inhibition of PKA or MAPK. The results demonstrate that adenosine causes secretion of VEGF from human skeletal muscle cells and that the contraction-induced secretion of VEGF protein is partially mediated via adenosine acting on A(2B) adenosine receptors. Moreover, the contraction-induced secretion of VEGF protein from muscle is dependent on both PKA and MAPK activation, but only the MAPK pathway appears to be adenosine dependent, revealing involvement of additional pathways in VEGF secretion. PMID:20543089

  4. Modulatory Effects of Endogenous Adenosine on Epinephrine Secretion From the Adrenal Medulla of the Rat

    Microsoft Academic Search

    Ching-jiunn Tseng; Wen-yu Ho; Hui-ching Lin; Che-se Tung; Chia-jen Kuan

    Abstract The purpose of this study was to examine (1) whether endogenous,adenosine receptors inhibit the release of epineph- rine and norepinephrine,from adrenal medulla in response to physiological and pharmacological,stimuli and (2) whether,the renin-angiotensin system modulates,this effect of endogenous adenosine. We used a conscious animal model,to approximate normal physiological conditions. Male Sprague-Dawley rats were treated with a surface adenosine receptor antagonist,

  5. Aggravated Brain Damage After Hypoxic Ischemia in Immature Adenosine A2A Knockout Mice

    Microsoft Academic Search

    Ulrika Ådén; Linda Halldner; Hugo Lagercrantz; Ishar Dalmau; Catherine Ledent; Bertil B. Fredholm

    2010-01-01

    Background and Purpose—Cerebral hypoxic ischemia (HI) is an important cause of brain injury in the newborn infant. Adenosine is believed to protect against HI brain damage. However, the roles of the different adenosine receptors are unclear, particularly in young animals. We examined the role of adenosine A2A receptors (A2AR) using 7-day-old A2A knockout (A2AR(\\/)) mice in a model of HI.

  6. Tolerance and diagnostic accuracy of an abbreviated adenosine infusion for myocardial scintigraphy: A randomized, prospective study

    Microsoft Academic Search

    Mark G. Treuth; Guillermo A. Reyes; Zuo-Xiang He; Eduardo Cwajg; John J. Mahmarian; Mario S. Verani

    2001-01-01

    Background  The objectives of this study were 2-fold: (1) to determine the tolerance of adenosine perfusion tomography with the use of\\u000a an abbreviated (3-minute) infusion in comparison to the standard (6-minute) infusion, and (2) to assess the relative diagnostic\\u000a accuracy of a 3-minute adenosine infusion in patients referred for arteriography. An abbreviated adenosine infusion may decrease\\u000a the frequency and duration of

  7. Specific binding of 3 H-adenosine to rat brain membranes

    Microsoft Academic Search

    U. Schwabe; H. Kiffe; C. Puchstein; T. Trost

    1979-01-01

    The binding of 3H-adenosine to rat brain membranes was studied by a microcentrifugation technique. Specific binding of 3H-adenosine was rapid, reversible, saturable and dependent on pH and temperature. Scatchard plots of equilibrium binding data were nonlinear suggesting the existence of two different binding sites for adenosine. The dissociation constants (Kd) were 1.7 µM and 13.6 µM and the maximal number

  8. Mechanical stimulation evokes rapid increases in extracellular adenosine concentration in the prefrontal cortex

    PubMed Central

    Ross, Ashley E.; Nguyen, Michael D.; Privman, Eve; Venton, B. Jill

    2014-01-01

    Mechanical perturbations can release ATP, which is broken down to adenosine. In this work, we used carbon-fiber microelectrodes and fast-scan cyclic voltammetry to measure mechanically-stimulated adenosine in the brain by lowering the electrode 50 ?m. Mechanical stimulation evoked adenosine in vivo (average: 3.3 ± 0.6 ?M) and in brain slices (average: 0.8 ± 0.1 ?M) in the prefrontal cortex. The release was transient, lasting 18 ± 2 s. Lowering a 15 ?m diameter glass pipette near the carbon-fiber microelectrode produced similar results as lowering the actual microelectrode. However, applying a small puff of artificial cerebral spinal fluid was not sufficient to evoke adenosine. Multiple stimulations within a 50 ?m region of a slice did not significantly change over time or damage cells. Chelating calcium with EDTA or blocking sodium channels with tetrodotoxin (TTX) significantly decreased mechanically evoked adenosine, signifying that the release is activity-dependent. An alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), did not affect mechanically-stimulated adenosine; however, the nucleoside triphosphate diphosphohydrolase 1,2 and 3 (NTDPase) inhibitor POM-1 significantly reduced adenosine so a portion of adenosine is dependent on extracellular ATP metabolism. Thus, mechanical perturbations from inserting a probe in the brain cause rapid, transient adenosine signaling which might be neuroprotective. PMID:24606335

  9. Adenosine and inosine release during hypoxia in the isolated spinal cord of neonatal rats

    PubMed Central

    Takahashi, T; Otsuguro, K; Ohta, T; Ito, S

    2010-01-01

    BACKGROUND AND PURPOSE Adenosine and inosine accumulate extracellularly during hypoxia/ischaemia in the brain and may act as neuroprotectants. In spinal cord, there is pharmacological evidence for increases in extracellular adenosine during hypoxia, but no direct measurements of purine release. Furthermore, the efflux pathways and origin of extracellular purines are not defined. To characterize hypoxia-evoked purine accumulation, we examined the effect of acute hypoxia on the extracellular levels of adenosine and inosine in isolated spinal cords from rats. EXPERIMENTAL APPROACH Extracellular adenosine and inosine concentrations were assayed in an in vitro preparation of the isolated spinal cord of the neonatal rat by HPLC. KEY RESULTS The extracellular level of inosine was about 10-fold higher than that of adenosine. Acute hypoxia (10 min) caused a temperature-dependent increase in these two purines, which were inhibited by an increase in external Ca2+, but not by several inhibitors of efflux pathways or metabolic enzymes of adenine nucleotides. Inhibitors of adenosine deaminase or the equilibrative nucleoside transporter (ENT) abolished the hypoxia-evoked increase in inosine but not adenosine. The inhibition of glial metabolism abolished the increase of both purines evoked by hypoxia but not by oxygen-glucose deprivation, hypercapnia or an adenosine kinase inhibitor. CONCLUSIONS AND IMPLICATIONS Our data suggest that hypoxia releases adenosine itself from intracellular sources. Inosine formed intracellularly may be released through ENTs. During hypoxia, astrocytes appear to play a key role in purine release from neonatal rat spinal cord. PMID:20735412

  10. Adenosine Receptor–Mediated Adhesion of Endothelial Progenitors to Cardiac Microvascular Endothelial Cells

    PubMed Central

    Ryzhov, Sergey; Solenkova, Nataliya V.; Goldstein, Anna E.; Lamparter, Mathias; Fleenor, Todd; Young, Pampee P.; Greelish, James P.; Byrne, John G.; Vaughan, Douglas E.; Biaggioni, Italo; Hatzopoulos, Antonis K.; Feoktistov, Igor

    2009-01-01

    Intracoronary delivery of endothelial progenitor cells (EPCs) is an emerging concept for the treatment of cardiovascular disease. Enhancement of EPC adhesion to vascular endothelium could improve cell retention within targeted organs. Because extracellular adenosine is elevated at sites of ischemia and stimulates neovascularization, we examined the potential role of adenosine in augmenting EPC retention to cardiac microvascular endothelium. Stimulation of adenosine receptors in murine embryonic EPCs (eEPCs) and cardiac endothelial cells (cECs) rapidly, within minutes, increased eEPC adhesion to cECs under static and flow conditions. Similarly, adhesion of human adult culture-expanded EPCs to human cECs was increased by stimulation of adenosine receptors. Furthermore, adenosine increased eEPC retention in isolated mouse hearts perfused with eEPCs. We determined that eEPCs and cECs preferentially express functional A1 and A2B adenosine receptor subtypes, respectively, and that both subtypes are involved in the regulation of eEPC adhesion to cECs. We documented that the interaction between P-selectin and its ligand (P-selectin glycoprotein ligand-1) plays a role in adenosine-dependent eEPC adhesion to cECs and that stimulation of adenosine receptors in cECs induces rapid cell surface expression of P-selectin. Our results suggest a role for adenosine in vasculogenesis and its potential use to stimulate engraftment in cell-based therapies. PMID:18032734

  11. Intracoronary Adenosine versus Intravenous Adenosine during Primary PCI for ST-Elevation Myocardial Infarction: Which One Offers Better Outcomes in terms of Microvascular Obstruction?

    PubMed Central

    Doolub, Gemina; Dall'Armellina, Erica

    2013-01-01

    Aims. Previous studies have suggested that intravenous administration of adenosine improves myocardial reperfusion and reduces infarct size in ST-elevation myocardial infarction (STEMI) patients. Intracoronary administration of adenosine has shown conflicting results. Methods. In this retrospective, single-centre, blinded clinical study, we assessed whether selective intracoronary administration of adenosine distal to the occlusion site immediately before initial balloon inflation reduces microvascular obstruction (MVO) as assessed with cardiac magnetic resonance imaging (MRI). Using contrast-enhanced sequences, microvascular obstruction (MVO) was calculated. We found 81 patients presenting with STEMI within 12?h from symptom onset who were eligible for the study. In 80/81 (100%) patients receiving the study drug, MRI was performed on Day 1 after primary angioplasty. Results. The prevalence of MVO was reduced in the patients treated with intracoronary adenosine, (45%) compared to 85% of patients who were administered intravenous adenosine (P = 0.0043). We found that the size of MVO in patients receiving intracoronary adenosine was significantly reduced compared to 0.91?g in the intravenous-treated group (P = 0.027). There was no statistically significant difference in TIMI flow and clinical outcomes after primary PCI. Conclusion. We found significant evidence that selective high-dose intracoronary administration of adenosine distal to the occlusion site of the culprit lesion in STEMI patients results in a decrease in microvascular obstruction. PMID:23606984

  12. Adenosine-5'-O-phosphorylated and adenosine-5'-O-phosphorothioylated polyols as strong inhibitors of (symmetrical) and (asymmetrical) dinucleoside tetraphosphatases.

    PubMed Central

    Guranowski, Andrzej; Starzy?ska, Elzbieta; McLennan, Alexander G; Baraniak, Janina; Stec, Wojciech J

    2003-01-01

    Dinucleoside 5',5"'- P (1), P ( n )-polyphosphates, and particularly the diadenosine compounds, have been implicated in extracellular purinergic signalling and in various intracellular processes, including DNA metabolism, tumour suppression and stress responses. If permitted to accumulate, they may also be toxic. One approach to understanding their function is through the various specific degradative enzymes that regulate their levels. Eight adenosine-5'- O -phosphorylated polyols (derivatives of glycerol, erythritol and pentaerythritol) and 11 adenosine-5'- O -phosphorothioylated polyols (derivatives of glycerol, erythritol, pentaerythritol, butanediol and pentanediol) have been tested as inhibitors of specific diadenosine tetraphosphate (Ap(4)A) hydrolases. Of these two groups of novel nucleotides, the adenosine-5'- O -phosphorothioylated polyols were generally stronger inhibitors than their adenosine-5'- O -phosphorylated counterparts. 1,4-Di(adenosine-5'- O -phosphorothio) erythritol appeared to be the strongest inhibitor of ( asymmetrical ) Ap(4)A hydrolases (EC 3.6.1.17) from both lupin and human, with K (i) values of 0.15 microM and 1.5 microM respectively. Of eight adenosine-5'- O -phosphorylated polyols, 1,4-di(adenosine-5'- O -phospho) erythritol was the only compound that inhibited the lupin enzyme. Two derivatives of pentaerythritol, di(adenosine-5'- O -phosphorothio)-di(phosphorothio) pentaerythritol and tri(adenosine-5'- O -phosphorothio)-phosphorothio-pentaerythritol, proved to be the strongest inhibitors of the prokaryotic ( symmetrical ) Ap(4)A hydrolase (EC 3.6.1.41) so far reported. The estimated K (i) values were 0.04 microM and 0.08 microM respectively. All of these inhibitors were competitive with respect to Ap(4)A. These new selectively acting Ap(4)A analogues should prove to be valuable tools for further studies of Ap(4)A function and of the enzymes involved in its metabolism. PMID:12697025

  13. Adenosine signaling contributes to ethanol-induced fatty liver in mice

    PubMed Central

    Peng, Zhongsheng; Borea, Pier Andrea; Wilder, Tuere; Yee, Herman; Chiriboga, Luis; Blackburn, Michael R.; Azzena, Gianfranco; Resta, Giuseppe; Cronstein, Bruce N.

    2009-01-01

    Fatty liver is commonly associated with alcohol ingestion and abuse. While the molecular pathogenesis of these fatty changes is well understood, the biochemical and pharmacological mechanisms by which ethanol stimulates these molecular changes remain unknown. During ethanol metabolism, adenosine is generated by the enzyme ecto-5?-nucleotidase, and adenosine production and adenosine receptor activation are known to play critical roles in the development of hepatic fibrosis. We therefore investigated whether adenosine and its receptors play a role in the development of alcohol-induced fatty liver. WT mice fed ethanol on the Lieber-DeCarli diet developed hepatic steatosis, including increased hepatic triglyceride content, while mice lacking ecto-5?-nucleotidase or adenosine A1 or A2B receptors were protected from developing fatty liver. Similar protection was also seen in WT mice treated with either an adenosine A1 or A2B receptor antagonist. Steatotic livers demonstrated increased expression of genes involved in fatty acid synthesis, which was prevented by blockade of adenosine A1 receptors, and decreased expression of genes involved in fatty acid metabolism, which was prevented by blockade of adenosine A2B receptors. In vitro studies supported roles for adenosine A1 receptors in promoting fatty acid synthesis and for A2B receptors in decreasing fatty acid metabolism. These results indicate that adenosine generated by ethanol metabolism plays an important role in ethanol-induced hepatic steatosis via both A1 and A2B receptors and suggest that targeting adenosine receptors may be effective in the prevention of alcohol-induced fatty liver. PMID:19221436

  14. Characterization of Spontaneous, Transient Adenosine Release in the Caudate-Putamen and Prefrontal Cortex

    PubMed Central

    Nguyen, Michael D.; Lee, Scott T.; Ross, Ashley E.; Ryals, Matthew; Choudhry, Vishesh I.; Venton, B. Jill

    2014-01-01

    Adenosine is a neuroprotective agent that inhibits neuronal activity and modulates neurotransmission. Previous research has shown adenosine gradually accumulates during pathologies such as stroke and regulates neurotransmission on the minute-to-hour time scale. Our lab developed a method using carbon-fiber microelectrodes to directly measure adenosine changes on a sub-second time scale with fast-scan cyclic voltammetry (FSCV). Recently, adenosine release lasting a couple of seconds has been found in murine spinal cord slices. In this study, we characterized spontaneous, transient adenosine release in vivo, in the caudate-putamen and prefrontal cortex of anesthetized rats. The average concentration of adenosine release was 0.17±0.01 µM in the caudate and 0.19±0.01 µM in the prefrontal cortex, although the range was large, from 0.04 to 3.2 µM. The average duration of spontaneous adenosine release was 2.9±0.1 seconds and 2.8±0.1 seconds in the caudate and prefrontal cortex, respectively. The concentration and number of transients detected do not change over a four hour period, suggesting spontaneous events are not caused by electrode implantation. The frequency of adenosine transients was higher in the prefrontal cortex than the caudate-putamen and was modulated by A1 receptors. The A1 antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine, 6 mg/kg i.p.) increased the frequency of spontaneous adenosine release, while the A1 agonist CPA (N6-cyclopentyladenosine, 1 mg/kg i.p.) decreased the frequency. These findings are a paradigm shift for understanding the time course of adenosine signaling, demonstrating that there is a rapid mode of adenosine signaling that could cause transient, local neuromodulation. PMID:24494035

  15. Recombinant ecto-5'-nucleotidase (CD73) has long lasting antinociceptive effects that are dependent on adenosine A1 receptor activation

    Microsoft Academic Search

    Nathaniel A Sowa; Meagen K Voss; Mark J Zylka

    2010-01-01

    BACKGROUND: Ecto-5'-nucleotidase (NT5E, also known as CD73) hydrolyzes extracellular adenosine 5'-monophosphate (AMP) to adenosine in nociceptive circuits. Since adenosine has antinociceptive effects in rodents and humans, we hypothesized that NT5E, an enzyme that generates adenosine, might also have antinociceptive effects in vivo. RESULTS: To test this hypothesis, we purified a soluble version of mouse NT5E (mNT5E) using the baculovirus expression

  16. Extracellular Adenosine Generation in the Regulation of Pro-Inflammatory Responses and Pathogen Colonization

    PubMed Central

    Alam, M. Samiul; Costales, Matthew G.; Cavanaugh, Christopher; Williams, Kristina

    2015-01-01

    Adenosine, an immunomodulatory biomolecule, is produced by the ecto-enzymes CD39 (nucleoside triphosphate dephosphorylase) and CD73 (ecto-5'-nucleotidase) by dephosphorylation of extracellular ATP. CD73 is expressed by many cell types during injury, infection and during steady-state conditions. Besides host cells, many bacteria also have CD39-CD73-like machinery, which helps the pathogen subvert the host inflammatory response. The major function for adenosine is anti-inflammatory, and most recent research has focused on adenosine’s control of inflammatory mechanisms underlying various autoimmune diseases (e.g., colitis, arthritis). Although adenosine generated through CD73 provides a feedback to control tissue damage mediated by a host immune response, it can also contribute to immunosuppression. Thus, inflammation can be a double-edged sword: it may harm the host but eventually helps by killing the invading pathogen. The role of adenosine in dampening inflammation has been an area of active research, but the relevance of the CD39/CD73-axis and adenosine receptor signaling in host defense against infection has received less attention. Here, we review our recent knowledge regarding CD73 expression during murine Salmonellosis and Helicobacter-induced gastric infection and its role in disease pathogenesis and bacterial persistence. We also explored a possible role for the CD73/adenosine pathway in regulating innate host defense function during infection. PMID:25950510

  17. Determination of ferulic acid and adenosine in Angelicae Radix by micellar electrokinetic chromatography

    Microsoft Academic Search

    Tao Guo; Yi Sun; Yin Sui; Famei Li

    2003-01-01

    A micellar electrokinetic chromatography for determining ferulic acid and adenosine in Angelicae Radix was developed. A buffer solution composed of 50 mmol Lу borax, 10 mmol Lу sodium deoxycholate, and 2% methanol was found to be the most suitable electrolyte for the separation. The contents of ferulic acid and adenosine in Angelicae Radix were determined within 20 min. Good linearity

  18. A 1 Adenosine Receptor Antagonists, Agonists, and Allosteric Enhancers

    Microsoft Academic Search

    William F. Kiesman; Elfatih Elzein; Jeff Zablocki

    \\u000a Intense efforts of many pharmaceutical companies and academicians in the A1 adenosine receptor (AR) field have led to the discovery of clinical candidates that are antagonists, agonists, and allosteric\\u000a enhancers. The A1AR antagonists currently in clinical development are KW3902, BG9928, and SLV320. All three have high affinity for the human\\u000a (h) A1AR subtype (hA1\\u000a K\\u000a i 200-fold selectivity over the

  19. Bone marrow transplantation and alternatives for adenosine deaminase deficiency.

    PubMed

    Gaspar, H Bobby

    2010-05-01

    Adenosine deaminase (ADA)-deficient severe combined immunodeficiency (SCID) comprises approximately 10% to 15% of all cases of SCID. The clinical effects of ADA deficiency are manifest most dramatically in the immune system, where it leads to severe lymphopenia. Although hematopoietic stem cell transplantation remains the mainstay of treatment for ADA-deficient SCID, 2 other treatment options are available, namely enzyme replacement therapy with PEG-ADA and autologous hematopoietic stem cell gene therapy. In this article the author reviews the available data on treatment by these different options, and offers an overview on when each of the different treatment options should be used. PMID:20493398

  20. Methotrexate and sulfasalazine promote adenosine release by a mechanism that requires ecto-5'-nucleotidase-mediated conversion of adenine nucleotides.

    PubMed Central

    Morabito, L; Montesinos, M C; Schreibman, D M; Balter, L; Thompson, L F; Resta, R; Carlin, G; Huie, M A; Cronstein, B N

    1998-01-01

    We and others have shown that an increased extracellular concentration of adenosine mediates the antiinflammatory effects of methotrexate and sulfasalazine both in vitro and in vivo, but the mechanism by which these drugs increase extracellular adenosine remains unclear. The results of the experiments reported here provide three distinct lines of evidence that adenosine results from the ecto-5'-nucleotidase- mediated conversion of adenine nucleotides to adenosine. First, pretreatment of a human microvascular endothelial cell line (HMEC-1) with methotrexate increases extracellular adenosine after exposure of the pretreated cells to activated neutrophils; the ecto-5'-nucleotidase inhibitor alpha, beta-methylene adenosine-5'-diphosphate (APCP) abrogates completely the increase in extracellular adenosine. Second, there is no methotrexate-mediated increase in extracellular adenosine concentration in the supernate of cells deficient in ecto-5'-nucleotidase, but there is a marked increase in extracellular adenosine concentration in the supernates of these cells after transfection and surface expression of the enzyme. Finally, as we have shown previously, adenosine mediates the antiinflammatory effects of methotrexate and sulfasalazine in the murine air pouch model of inflammation, and injection of APCP, the ecto-5'-nucleotidase inhibitor, abrogates completely the increase in adenosine and the decrement in inflammation in this in vivo model. These results not only show that ecto-5'-nucleotidase activity is a critical mediator of methotrexate- and sulfasalazine-induced antiinflammatory activity in vitro and in vivo but also indicate that adenine nucleotides, released from cells, are the source of extracellular adenosine. PMID:9435300

  1. Release of adenosine and ATP in the brain of the freshwater turtle ( Trachemys scripta) during long-term anoxia

    Microsoft Academic Search

    Peter L Lutz; Sandra Kabler

    1997-01-01

    Extracellular adenosine and ATP levels were monitored by microdialysis in the striatum of the freshwater turtle Trachemys scripta during long-term N2 respiration. After an initial rise in extracellular adenosine, a second peak of longer duration and higher in intensity, followed. The frequencies of these adenosine cycles varied considerably between individual turtles, such that the shortest time between the peaks was

  2. Distinct cardioprotective effects of adenosine mediated by differential coupling of receptor subtypes to phospholipases C and D

    Microsoft Academic Search

    MOLLIE PARSONS; LAURA YOUNG; JANG EUN LEE; KENNETH A. JACOBSON; BRUCE T. LIANG

    2000-01-01

    Adenosine released during cardiac ischemia exerts a marked protective effect in the heart that is mediated by the A1 and A3 subtypes of adenosine receptors. The signaling pathways acti- vated by these adenosine receptors have now been characterized in a chick embryo ventricular myocyte culture model of cardioprotection against ischemia. Selective A1 and A3 receptor agonists were shown to activate

  3. Drugs elevating extracellular adenosine enhance cell cycling of hematopoietic progenitor cells as inferred from the cytotoxic effects of 5-fluorouracil

    Microsoft Academic Search

    Milan Posp???il; Michal Hofer; Anton??n Vacek; Jarom??ra Net??ková; Ji?ina Holá; Vladim??r Znojil; Lenka Weiterová

    2001-01-01

    ObjectiveOur previous studies showed that the combined administration of drugs elevating extracellular adenosine, i.e., dipyridamole and adenosine monophosphate (AMP), enhanced hematopoiesis in normal mice and increased hematopoietic recovery in irradiated mice. In the present study, we have examined the possibility that these effects are due to the adenosine-induced cycling of the hematopoietic progenitor cells.

  4. Functional and molecular characterization of receptor subtypes mediating coronary microvascular dilation to adenosine.

    PubMed

    Hein, T W; Wang, W; Zoghi, B; Muthuchamy, M; Kuo, L

    2001-02-01

    Adenosine is a potent vasodilator of the coronary microvessels and is implicated in the regulation of coronary blood flow during metabolic stress. However, the receptor subtypes and the vasodilatory mechanism responsible for the dilation of coronary microvessels to adenosine remain unclear. In the present study, using an isolated-vessel preparation we demonstrated that porcine coronary arterioles (50-100 microm) dilated concentration-dependently to adenosine, CPA (adenosine A1 receptor agonist) and CGS21680 (adenosine A2A receptor agonist). These vasodilations were not altered by the A1 receptor antagonist CPX, but were abolished by the selective A2A receptor antagonist ZM241385, indicating that activation of A2A receptors mediates these vasodilatory responses. The protein kinase A inhibitor Rp-8-Br-cAMPS abolished coronary arteriolar dilations to adenylyl cyclase activator forskolin and cAMP analog 8-Br-cAMP, but failed to inhibit adenosine- and CGS21680-induced dilations. The calcium-activated potassium channel inhibitor iberiotoxin also did not affect vasodilations to adenosine and CGS21680. In contrast, the ATP-sensitive potassium (K(ATP)) channel inhibitor glibenclamide abolished vasodilations to adenosine and CGS21680 but did not affect vasodilations to forskolin and 8-Br-cAMP. In addition, the cAMP level in coronary microvessels was not increased by adenosine or CGS21680. The results from RT/PCR and in situ hybridization indicated that adenosine A2A receptor mRNA was encoded in coronary arterioles and the left anterior descending (LAD) artery but not in cardiomyocytes, whereas the A1 receptor transcript was detected in the LAD artery and cardiomyocytes but not in arterioles. Similarly, adenosine A1 and A2A proteins were expressed in the LAD artery, but only A2A receptors were expressed in coronary arterioles. Collectively, these functional data suggest that coronary arteriolar dilation to adenosine is primarily mediated by the opening of K(ATP) channels through activation of A2A receptors. This conclusion is corroborated by the molecular data showing that coronary arterioles only express adenosine A2A receptors. Furthermore, the dilation of coronary microvessels to adenosine A2A receptor activation appears to be independent of cAMP signaling. PMID:11162132

  5. Adenosine receptor expression in a rat model of experimental autoimmune myasthenia gravis.

    PubMed

    Li, Na; Wang, Geng; Yao, Xiuhua; Kong, Qingfei; Shang, Xiaoyu; Xie, Xiaoli; Wang, Jinghua; Kang, Xiaoying; Jin, Lianhong; Wang, Guangyou; Li, Hulun; Mu, Lili; Sun, Bo

    2014-08-01

    Extracellular adenosine is an essential negative regulator of immune reactions that acts by signaling via 4 distinct adenosine receptors. We evaluated adenosine receptor expression in Lewis rats presenting with experimental autoimmune myasthenia gravis (EAMG) to determine whether the expression of adenosine receptors are changed in the development and progression of EAMG. Lymphocyte A1AR and A2AAR mRNA and protein levels from lymphocytes harvested from the lymph nodes, spleen, and peripheral blood mononuclear cells (PBMCs) of EAMG rats were decreased. A modest but not significant increase in A2BAR levels was observed in EAMG lymphocytes harvested from lymph nodes and PBMCs. No changes in A3AR expression were observed in lymphocytes harvested from lymph nodes, spleen, or PBMCs following EAMG induction. Results presented in this report showed that the expression levels and the distribution pattern of adenosine receptors were altered in EAMG lymphocytes. PMID:25086239

  6. Intraosseous infusion is unreliable for adenosine delivery in the treatment of supraventricular tachycardia.

    PubMed

    Goodman, Ian Scott; Lu, Christina Jennifer

    2012-01-01

    Supraventricular tachycardia (SVT) is a common tachyarrhythmia in the pediatric population that can necessitate immediate treatment. Adenosine has been well studied as a mainstay treatment, but the methods of adenosine administration have not been very well delineated. The intraosseous technique has presented itself as a possible method of administration. We describe 2 cases in which adenosine was administered through bone marrow infusion to convert SVT without success. The cases we describe show that intraosseous is not a reliable method of administering adenosine to stop SVT. Both patients presented with SVT refractory to vagal maneuvers and difficult intravenous placement. Intraosseous access was achieved, but administration of adenosine at increasing doses was unable to successfully convert the arrhythmia. PMID:22217885

  7. Respiratory stimulant effects of adenosine in man after caffeine and enprofylline.

    PubMed Central

    Smits, P; Schouten, J; Thien, T

    1987-01-01

    In a double-blind and randomized study the respiratory stimulant effect of continuous intravenous adenosine infusion was studied after previous administration of caffeine, placebo and enprofylline in 10 healthy young volunteers. After placebo, adenosine induced an increase of minute ventilation (from 6.3 to 12.5 l min-1), tidal volume (from 0.60 to 0.96 l), and breathing rate (from 11.0 to 14.8 min-1). Venous pCO2 fell and pH rose after adenosine. Caffeine significantly reduced the adenosine-induced changes of minute ventilation, tidal volume, venous pCO2 and pH, whereas no changes occurred after enprofylline. Our results suggest that adenosine stimulates respiration in man by binding with specific P1-purinoceptors, which can be blocked by caffeine, but not by enprofylline. PMID:3440102

  8. The kinetic mechanism of S. pneumoniae DNA ligase and inhibition by adenosine-based antibacterial compounds.

    PubMed

    Jahi?, Haris; Liu, Ce Feng; Thresher, Jason; Livchak, Stephania; Wang, Hongming; Ehmann, David E

    2012-09-01

    The NAD-dependent DNA ligase is an excellent target for the discovery of antibacterial agents with a novel mode of action. In this work the DNA ligase from Streptococcus pneumoniae was investigated for its steady-state kinetic parameters and inhibition by compounds with an adenosine substructure. Inhibition by substrate DNA that was observed in the enzyme turnover experiments was verified by direct binding measurements using isothermal titration calorimetry (ITC). The substrate-inhibited enzyme form was identified as deadenylated DNA ligase. The binding potencies of 2-(butylsulfanyl) adenosine and 2-(cyclopentyloxy) adenosine were not significantly affected by the presence of the enzyme-bound DNA substrate. Finally, a mutant protein was prepared that was known to confer resistance to the adenosine compounds' antibacterial activity. The mutant protein was shown to have little catalytic impairment yet it was less susceptible to adenosine compound inhibition. PMID:22743594

  9. 2-(1-Hexyn-1-yl)adenosine-induced intraocular hypertension is mediated via K+ channel opening through adenosine A2A receptor in rabbits.

    PubMed

    Konno, Takashi; Uchibori, Takehiro; Nagai, Akihiko; Kogi, Kentaro; Nakahata, Norimichi

    2005-08-22

    The present study was performed to clarify the mechanism of change in intraocular pressure by 2-(1-hexyn-1-yl)adenosine (2-H-Ado), a selective adenosine A2 receptor agonist, in rabbits. 2-H-Ado (0.1%, 50 microl)-induced ocular hypertension (E(max): 7.7 mm Hg) was inhibited by an adenosine A2A receptor antagonist 1,3,7-trimethyl-8-(3-chlorostyryl)xanthine, ATP-sensitive K+ channel blocker glibenclamide or 5-hydroxydecanoic acid, but not by an adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine, an adenosine A2B receptor antagonist alloxazine or a cyclooxygenase inhibitor indomethacin. The outflow facility induced by 2-H-Ado seems to be independent of increase in intraocular pressure or ATP-sensitive K+ channel. In contrast, the recovery rate in intraocular pressure decreased by hypertonic saline was accelerated by 2-H-Ado, and this response was dependent on ATP-sensitive K+ channel. These results suggest that 2-H-Ado-induced ocular hypertension is mediated via K+ channel opening through adenosine A2A receptor, and this is probably due to aqueous formation, but independent of change in outflow facility or prostaglandin production. PMID:16023100

  10. Approximation of A1 adenosine receptor reserve appertaining to the direct negative inotropic effect of adenosine in hyperthyroid guinea pig left atria.

    PubMed

    Pak, Krisztian; Papp, Csaba; Galajda, Zoltan; Szerafin, Tamas; Varga, Balazs; Juhasz, Bela; Haines, David; Szentmiklosi, Andras J; Tosaki, Arpad; Gesztelyi, Rudolf

    2014-01-01

    Hyperthyroidism elevates cardiovascular mortality by several mechanisms, including increased risk of ischemic heart disease. Therefore, therapeutic strategies, which enhance tolerance of heart to ischemia-reperfusion injury, may be particularly useful for hyperthyroid patients. One promising cardioprotective approach is use of agents that cause (directly or indirectly) A1 adenosine receptor (A1 receptor) activation, since A1 adenosinergic pathways initiate protective mechanisms such as ischemic preconditioning. However, previously we found great A1 receptor reserve for the direct negative inotropic effect of adenosine in isolated guinea pig atria. This phenomenon suggests that weakening of atria is a possible side effect of A1 adenosinergic stimulant agents. Thus, the goal of the present investigation was to explore this receptor reserve in hyperthyroidism. Our recently developed method was used that prevents the rapid intracellular elimination of adenosine, allowing sufficient time for exogenous adenosine administered for the generation of concentration-response curves to exert its effect. Our method also allowed correction for the bias caused by the consequent endogenous adenosine accumulation. Our results demonstrate that thyroxine treatment does not substantially affect the A1 receptor reserve for the direct negative inotropic effect of adenosine. Consequently, if an agent causing A1 receptor activation is administered for any indication, the most probable adverse effect affecting the heart may be a decrease of atrial contractility in both eu- and hyperthyroid conditions. PMID:24177021

  11. Lifetime evidence for a weak lowest electronic transition in adenosine.

    PubMed

    Hart, L P; Daniels, M

    1989-07-31

    The fluorescence decay of adenosine in 1:1 glycol/water glass has been determined at 77K using narrow pulse (700 ps) laser excitation at 290 nm and fluorescence detection with a scanned narrow-gate (100 ps) fast sampler together with digital averaging. Data analysis by re-iterative non-linear least squares convolution shows the decay is best represented by the bi-exponential form I(t) = 0.59exp - t/1.2ns + 0.41 exp - t/7.0ns. This leads to intrinsic radiative lifetimes of 150 ns and 220 ns respectively and a combined oscillator strength of 1.5 x 10(-2). Compared with the overall oscillator strength of 0.29 for the entire first absorption band of adenosine this indicates that transitions to and from the lowest-lying state in this band are quite forbidden. This is not accounted for by current theoretical considerations. PMID:2757640

  12. Adenosine signaling and the energetic costs of induced immunity.

    PubMed

    Lazzaro, Brian P

    2015-04-01

    Life history theory predicts that trait evolution should be constrained by competing physiological demands on an organism. Immune defense provides a classic example in which immune responses are presumed to be costly and therefore come at the expense of other traits related to fitness. One strategy for mitigating the costs of expensive traits is to render them inducible, such that the cost is paid only when the trait is utilized. In the current issue of PLOS Biology, Bajgar and colleagues elegantly demonstrate the energetic and life history cost of the immune response that Drosophila melanogaster larvae induce after infection by the parasitoid wasp Leptopilina boulardi. These authors show that infection-induced proliferation of defensive blood cells commands a diversion of dietary carbon away from somatic growth and development, with simple sugars instead being shunted to the hematopoetic organ for rapid conversion into the raw energy required for cell proliferation. This metabolic shift results in a 15% delay in the development of the infected larva and is mediated by adenosine signaling between the hematopoietic organ and the central metabolic control organ of the host fly. The adenosine signal thus allows D. melanogaster to rapidly marshal the energy needed for effective defense and to pay the cost of immunity only when infected. PMID:25915419

  13. Methylthioadenosine Reprograms Macrophage Activation through Adenosine Receptor Stimulation

    PubMed Central

    Keyel, Peter A.; Romero, Matthew; Wu, Wenbo; Kwak, Daniel H.; Zhu, Qin; Liu, Xinyu; Salter, Russell D.

    2014-01-01

    Regulation of inflammation is necessary to balance sufficient pathogen clearance with excessive tissue damage. Central to regulating inflammation is the switch from a pro-inflammatory pathway to an anti-inflammatory pathway. Macrophages are well-positioned to initiate this switch, and as such are the target of multiple therapeutics. One such potential therapeutic is methylthioadenosine (MTA), which inhibits TNF? production following LPS stimulation. We found that MTA could block TNF? production by multiple TLR ligands. Further, it prevented surface expression of CD69 and CD86 and reduced NF-KB signaling. We then determined that the mechanism of this action by MTA is signaling through adenosine A2 receptors. A2 receptors and TLR receptors synergized to promote an anti-inflammatory phenotype, as MTA enhanced LPS tolerance. In contrast, IL-1? production and processing was not affected by MTA exposure. Taken together, these data demonstrate that MTA reprograms TLR activation pathways via adenosine receptors to promote resolution of inflammation. PMID:25117662

  14. A continuous spectrophotometric assay for monitoring adenosine 5'-monophosphate production.

    PubMed

    First, Eric A

    2015-08-15

    A number of biologically important enzymes release adenosine 5'-monophosphate (AMP) as a product, including aminoacyl-tRNA synthetases, cyclic AMP (cAMP) phosphodiesterases, ubiquitin and ubiquitin-like ligases, DNA ligases, coenzyme A (CoA) ligases, polyA deadenylases, and ribonucleases. In contrast to the abundance of assays available for monitoring the conversion of adenosine 5'-triphosphate (ATP) to ADP, there are relatively few assays for monitoring the conversion of ATP (or cAMP) to AMP. In this article, we describe a homogeneous assay that continuously monitors the production of AMP. Specifically, we have coupled the conversion of AMP to inosine 5'-monophosphate (IMP) (by AMP deaminase) to the oxidation of IMP (by IMP dehydrogenase). This results in the reduction of oxidized nicotine adenine dinucleotide (NAD(+)) to reduced nicotine adenine dinucleotide (NADH), allowing AMP formation to be monitored by the change in the absorbance at 340nm. Changes in AMP concentrations of 5?M or more can be reliably detected. The ease of use and relatively low expense make the AMP assay suitable for both high-throughput screening and kinetic analyses. PMID:25957126

  15. Adenosine Amine Congener as a Cochlear Rescue Agent

    PubMed Central

    Vlajkovic, Srdjan M.; Chang, Hao; Paek, Song Yee; Chi, Howard H.-T.; Sreebhavan, Sreevalsan; Telang, Ravindra S.; Tingle, Malcolm; Housley, Gary D.; Thorne, Peter R.

    2014-01-01

    We have previously shown that adenosine amine congener (ADAC), a selective A1 adenosine receptor agonist, can ameliorate noise- and cisplatin-induced cochlear injury. Here we demonstrate the dose-dependent rescue effects of ADAC on noise-induced cochlear injury in a rat model and establish the time window for treatment. Methods. ADAC (25–300??g/kg) was administered intraperitoneally to Wistar rats (8–10 weeks old) at intervals (6–72 hours) after exposure to traumatic noise (8–16?kHz, 110?dB sound pressure level, 2 hours). Hearing sensitivity was assessed using auditory brainstem responses (ABR) before and 12 days after noise exposure. Pharmacokinetic studies investigated ADAC concentrations in plasma after systemic (intravenous) administration. Results. ADAC was most effective in the first 24 hours after noise exposure at doses >50??g/kg, providing up to 21?dB protection (averaged across 8–28?kHz). Pharmacokinetic studies demonstrated a short (5?min) half-life of ADAC in plasma after intravenous administration without detection of degradation products. Conclusion. Our data show that ADAC mitigates noise-induced hearing loss in a dose- and time-dependent manner, but further studies are required to establish its translation as a clinical otological treatment. PMID:25243188

  16. Regulation of G Protein-Coupled Receptor-Adenylyl Cyclase Responsiveness in Human Airway Smooth Muscle by Exogenous and Autocrine Adenosine

    Microsoft Academic Search

    Stuart J. Mundell; Mark E. Olah; Reynold A. Panettieri; Jeffrey L. Benovic; Raymond B. Penn

    2001-01-01

    Adenosine is a mediator of bronchoconstriction in asthmatics and is believed to mediate its effects through adenosine re- ceptor activation in inflammatory cells. In this study, we iden- tify human airway smooth muscle (ASM) as a direct target of adenosine. Acute exposure of human ASM cultures to adeno- sine receptor (AR) agonists resulted in rapid accumulation of cyclic adenosine monophosphate

  17. Effect of adenosine and adenosine receptor antagonist on Müller cell potassium channel in Rat chronic ocular hypertension models.

    PubMed

    Yang, Zijian; Huang, Ping; Liu, Xiaohong; Huang, Shouyue; Deng, Lianfu; Jin, Zhe; Xu, Shuo; Shen, Xi; Luo, Xunda; Zhong, Yisheng

    2015-01-01

    Müller cells are principal glial cells in rat retina and have attracted much attention in glaucoma studies. However, it is not clear whether adenosine and adenosine receptor (AR) antagonists play any roles in the regulation of potassium channels in Müller cells and subsequently in the promotion of glutamine synthetase (GS) and L-Glutamate/L-Aspartate Transporter (GLAST) functions. We found that chronic ocular hypertension (COH) in rat down-regulated Müller cells Kir2.1, Kir4.1, TASK-1, GS and GLAST expressions and attenuated the peak of inward potassium current. Retinal ganglion cells (RGC) count was lower in the COH rats than that in the sham operation animals. Intravitreal injection of selective A2A AR antagonist SCH442416 up-regulated Müller cell Kir4.1, TASK-1, GS and GLAST expressions and enhanced inward potassium currents compared with those in the COH rats with vehicle control. Meanwhile, the RGC count was higher following intravitreal injection of SCH442416 in the COH rats than that after vehicle injection. The fact that PKA inhibitor H-89 blocked these SCH442416 effects suggested that the PKA signaling pathway was involved in the observed ocular responses following the intravitreal SCH442416 injection. PMID:26063641

  18. Effect of adenosine and adenosine receptor antagonist on Müller cell potassium channel in Rat chronic ocular hypertension models

    PubMed Central

    Yang, Zijian; Huang, Ping; Liu, Xiaohong; Huang, Shouyue; Deng, Lianfu; Jin, Zhe; Xu, Shuo; Shen, Xi; Luo, Xunda; Zhong, Yisheng

    2015-01-01

    Müller cells are principal glial cells in rat retina and have attracted much attention in glaucoma studies. However, it is not clear whether adenosine and adenosine receptor (AR) antagonists play any roles in the regulation of potassium channels in Müller cells and subsequently in the promotion of glutamine synthetase (GS) and L-Glutamate/L-Aspartate Transporter (GLAST) functions. We found that chronic ocular hypertension (COH) in rat down-regulated Müller cells Kir2.1, Kir4.1, TASK-1, GS and GLAST expressions and attenuated the peak of inward potassium current. Retinal ganglion cells (RGC) count was lower in the COH rats than that in the sham operation animals. Intravitreal injection of selective A2A AR antagonist SCH442416 up-regulated Müller cell Kir4.1, TASK-1, GS and GLAST expressions and enhanced inward potassium currents compared with those in the COH rats with vehicle control. Meanwhile, the RGC count was higher following intravitreal injection of SCH442416 in the COH rats than that after vehicle injection. The fact that PKA inhibitor H-89 blocked these SCH442416 effects suggested that the PKA signaling pathway was involved in the observed ocular responses following the intravitreal SCH442416 injection. PMID:26063641

  19. Effects of near-infra-red laser irradiation on adenosine triphosphate and adenosine diphosphate contents of rat brain tissue.

    PubMed

    Mochizuki-Oda, Noriko; Kataoka, Yosky; Cui, Yilong; Yamada, Hisao; Heya, Manabu; Awazu, Kunio

    2002-05-01

    Low-power, near-infra-red laser irradiation has been used to relieve patients from various kinds of pain, though the precise mechanisms of such biological actions of the laser have not yet been resolved. To investigate the cellular mechanisms by near-infra-red laser on the nervous system, we examined the effect of 830-nm laser irradiation on the energy metabolism of the rat brain. The diode laser was applied for 15 min with an irradiance of 4.8 W/cm(2). Tissue adenosine triphosphate (ATP) content of the irradiated area in the cerebral cortex was 19% higher than that of the non-treated area, whereas the adenosine diphosphate (ADP) content showed no significant difference. Laser irradiation at another wavelength (652 nm) had no effect on either ATP or ADP contents. The temperature of the tissue was increased by 4.4-4.7 degrees C during the irradiation of both wavelengths. These results suggest that the increase in tissue ATP content did not result from the thermal effect, but from a specific effect of the laser operated at the 830-nm wavelength. PMID:11959421

  20. Angiotensin AT1 receptor blockade abolishes the reflex sympatho-excitatory response to adenosine.

    PubMed Central

    Rongen, G A; Brooks, S C; Ando, S i; Abramson, B L; Floras, J S

    1998-01-01

    We tested the hypothesis that endogenous angiotensin II participates in the direct and reflex effects of adenosine on the sympathetic nervous system. Nine healthy men were studied after 1 wk of the angiotensin II type I receptor antagonist losartan (100 mg daily) or placebo, according to a double-blind randomized crossover design. Bilateral forearm blood flows, NE appearance rates, and total body NE spillover were determined before and during graded brachial arterial infusion of adenosine (0.5, 1.5, 5, and 15 microg/100 ml forearm tissue) and nitroprusside. Adenosine increased total body NE spillover (P < 0.05) whereas nitroprusside did not. Losartan lowered BP (P < 0.05), had no effect on total body NE spillover at rest, or forearm vasodilation during either infusion, but reduced the systemic noradrenergic response to adenosine from 1.0+/-0.4 nmol/min on the placebo day to 0.2+/-0.3 nmol/min (P < 0.01), and forearm NE appearance rate in response to adenosine was lower in the infused, as compared with the contralateral arm (P = 0.04). The sympatho-excitatory reflex elicited by adenosine is mediated through pathways involving the angiotensin II type I receptor. Interactions between adenosine and angiotensin II may assume importance during ischemia or congestive heart failure and could contribute to the benefit of converting enzyme inhibition in these conditions. PMID:9466971

  1. Evidence for constitutively-active adenosine receptors at mammalian motor nerve endings

    PubMed Central

    Searl, Timothy J.; Silinsky, Eugene M.

    2012-01-01

    A study was made to determine if constitutively active adenosine receptors are present at mouse motor nerve endings. In preparations blocked by low Ca2+ / high Mg2+ solution, 8-cyclopentyl-1,3,dipropylxanthine (CPX, 10–100 nM), which has been reported to be both an A1 adenosine receptor antagonist and inverse agonist, produced a dose-dependent increase in the number of acetylcholine quanta released by a nerve impulse. Adenosine deaminase, which degrades ambient adenosine into its inactive congener, inosine, failed to alter the response to 100 nM CPX. 8-cyclopentyltheophylline (CPT, 3 ?M), a competitive inhibitor at A1 adenosine receptors, prevented the increase in acetylcholine release produced by CPX. At normal levels of acetylcholine release, neither adenosine deaminase nor CPX affected acetylcholine release at low frequencies of nerve stimulation in (+)-tubocurarine blocked preparations. The results suggest that a proportion of the acetylcholine release process is controlled by constitutively active adenosine receptors at murine motor nerve endings, providing the first evidence for constitutive activity of G-protein-coupled receptors that modulate the function of mammalian nerve endings. PMID:22542659

  2. Physiological control of NKT cell-dependent hepatitis induction by extracellular adenosine

    PubMed Central

    Subramanian, Meenakshi; Kini, Radhika; Madasu, Manasa; Ohta, Akiko; Nowak, Michael; Exley, Mark; Sitkovsky, Michail; Ohta, Akio

    2015-01-01

    Summary Extracellular adenosine regulates inflammatory responses via A2A adenosine receptor (A2AR). A2AR-deficiency results in much exaggerated acute hepatitis, indicating non-redundancy of adenosine-A2AR pathway in inhibitory mechanisms of immune activation. To identify a critical target of immunoregulatory effect of extracellular adenosine, we focused on NKT cells, which play an indispensable role in hepatitis. A2AR agonist abolished NKT cell-dependent induction of acute hepatitis by Con A or ?-galactosylceramide (?-GalCer), corresponding to down-regulation of activation markers and cytokines in NKT cells and of NK cell co-activation. These results show that A2AR signaling can down-regulate NKT cell activation and suppress NKT cell-triggered inflammatory responses. Next, we hypothesized that NKT cells might be under physiological control of the adenosine-A2AR pathway. Indeed, both Con A and ?-GalCer induced more severe hepatitis in A2AR?/? mice than in wild-type controls. Transfer of A2AR?/? NKT cells into A2AR-expressing recipients resulted in exaggeration of Con A-induced liver damage, suggesting that NKT cell activation is controlled by endogenous adenosine via A2AR, and this physiological regulatory mechanism of NKT cells is critical in the control of tissue-damaging inflammation. The current study suggests the possibility to manipulate NKT cell activity in inflammatory disorders through intervention to the adenosine-A2AR pathway. PMID:24448964

  3. Adenosine kinase inhibition in the cochlea delays the onset of age-related hearing loss

    PubMed Central

    Vlajkovic, Srdjan M.; Guo, Cindy X.; Telang, Ravindra; Wong, Ann Chi Yan; Paramananthasivam, Vinthiya; Boison, Detlev; Housley, Gary D.; Thorne, Peter R.

    2011-01-01

    This study was undertaken to determine the role of adenosine signalling in the development of age-related hearing loss (ARHL). We and others have shown previously that adenosine signalling via A1 receptors is involved in cochlear protection from noise-induced cochlear injury. Here we demonstrate that enhanced adenosine signalling in the cochlea provides partial protection from ARHL in C57BL/6J mice. We targeted adenosine kinase (ADK), the key enzyme in adenosine metabolism, using a treatment regime with the selective ADK inhibitor ABT-702 (1.5 mg/kg intraperitoneally twice a week) commencing at the age of three months or six months. This treatment, intended to increase free adenosine levels in the cochlea, was maintained until the age of nine months and hearing thresholds were evaluated monthly using auditory brainstem responses (ABR). At nine months, when C57BL/6J mice normally exhibit significant ARHL, both groups treated with ABT-702 showed lower ABR threshold shifts at 10 and 16 kHz compared to control animals receiving the vehicle solution. The better thresholds of the ABT-702-treated mice at these frequencies were supported by increased survival of hair cells in the apical region of the cochlea. This study provides the first evidence that ARHL can be mitigated by enhancing adenosine signalling in the cochlea. PMID:21846498

  4. Evidence for evoked release of adenosine and glutamate from cultured cerebellar granule cells

    SciTech Connect

    Schousboe, A.; Frandsen, A.; Drejer, J. (Univ. of Copenhagen (Denmark))

    1989-09-01

    Evoked release of ({sup 3}H)-D-aspartate which labels the neurotransmitter glutamate pool in cultured cerebellar granule cells was compared with evoked release of adenosine from similar cultures. It was found that both adenosine and (3H)-D-aspartate could be released from the neurons in a calcium dependent manner after depolarization of the cells with either 10-100 microM glutamate or 50 mM KCl. Cultures of cerebellar granule cells treated with 50 microM kainate to eliminate GABAergic neurons behaved in the same way. This together with the observation that cultured astrocytes did not exhibit a calcium dependent, potassium stimulated adenosine release strongly suggest that cerebellar granule cells release adenosine in a neurotransmitter-like fashion together with glutamate which is the classical neurotransmitter of these neurons. Studies of the metabolism of adenosine showed that in the granule cells adenosine is rapidly metabolized to ATP, ADP, and AMP, but in spite of this, adenosine was found to be released preferential to ATP.

  5. Crystal structure of a model branchpoint-U2 snRNA duplex containing bulged adenosines.

    PubMed Central

    Berglund, J A; Rosbash, M; Schultz, S C

    2001-01-01

    Bulged nucleotides play a variety of important roles in RNA structure and function, frequently forming tertiary interactions and sometimes even participating in RNA catalysis. In pre-mRNA splicing, the U2 snRNA base pairs with the intron branchpoint sequence (BPS) to form a short RNA duplex that contains a bulged adenosine that ultimately serves as the nucleophile that attacks the 5' splice site. We have determined a 2.18-A resolution crystal structure of a self-complementary RNA designed to mimic the highly conserved yeast (Saccharomyces cerevisiae) branchpoint sequence (5'-UACUAACGUAGUA with the BPS italicized and the branchsite adenosine underlined) base paired with its complementary sequence from U2 snRNA. The structure shows a nearly ideal A-form helix from which two unpaired adenosines flip out. Although the adenosine adjacent to the branchsite adenosine is the one bulged out in the structure described here, either of these adenosines can serve as the nucleophile in mammalian but not in yeast pre-mRNA splicing. In addition, the packing of the bulged RNA helices within the crystal reveals a novel RNA tertiary interaction in which three RNA helices interact through bulged adenosines in the absence of any divalent metal ions. PMID:11350032

  6. Adenosine deaminase in rodent median eminence: detection by antibody to the mouse enzyme and co-localization with adenosine deaminase-complexing protein (CD26).

    PubMed

    Nagy, J I; Yamamoto, T; Uemura, H; Schrader, W P

    1996-07-01

    Adenosine deaminase in the hypothalamic tuberomammillary nucleus and median eminence of rat and mouse brains was investigated with two different antibodies generated against the enzyme derived from either calf or mouse. Both antibodies labelled neurons in the tuberomammillary nucleus and, as determined in rat, they immunolabelled the same neurons. In the median eminence, immunopositive fibres and terminals were detected with anti-mouse adenosine deaminase in both rat and mouse, while no such staining was seen in either species with antibody against the calf enzyme. These fibres were most concentrated in the external median eminence, had a more restricted distribution than those containing either galanin or tyrosine hydroxylase and only partially overlapped with oxytocin-positive fibres. By electron microscopy, adenosine deaminase was found in terminals containing both small, clear vesicles with diameters of 35 to 45 nm and large dense-core vesicles with diameters of 100 to 140 nm. Preadsorption of antibodies with purified enzyme derived from the species against which they were directed eliminated all staining in rat, while antibody adsorptions across species were less effective. Preadsorption of anti-mouse adenosine deaminase antibody with the mouse deaminase led to increased labelling in mouse median eminence, suggesting an interaction between tissue components and antibody-linked enzyme. Tests for the presence of adenosine deaminase-complexing protein (CD26) with an antibody against this protein gave positive labelling in the median eminence of both species and this labelling was co-distributed with that seen for adenosine deaminase. These results confirm the expression of adenosine deaminase in restricted populations of neurons in rodent brain as revealed with a novel antibody, suggest the presence of a distinct form or localization of the enzyme in the median eminence, and raise the possibility that it contributes, perhaps along with CD26, to purinergic regulation of hormone secretion in this structure. PMID:8783262

  7. Adenosine A?A and A? receptors are involved in the human endothelial progenitor cells migration.

    PubMed

    Fernandez, Paulina; Jara, Casandra; Aguilera, Valeria; Caviedes, Liska; Diaz, Francisca; Radojkovic, Claudia; Veas, Carlos; Lamperti, Liliana; Escudero, Carlos; Aguayo, Claudio

    2012-05-01

    Human endothelial progenitor cells (hEPC) are recruited to sites of neovascularization where they differentiate into endothelial cells. The signals/factors responsible for hEPC migration and adhesion to sites of injury are not well understood. Elevated levels of adenosine are known to increase mature endothelial cell migration in response to tissue injury. However, the understanding of the role of adenosine in the physiology of hEPC is very limited. Using quantitative polymerase chain reaction and western blot analyses, we detected the expression of the adenosine receptors A?A, A?B, and A? in hEPC. Stimulation of adenosine receptors using adenosine or the nonselective agonist adenosine-5'-N-ethylcarboxamide (NECA) increased hEPC migration in 1.4-fold and 2.1-fold (P < 0.01), respectively. Stimulation of hEPC using the A?A-specific agonist CGS-21680 resembled the effect observed in migration when using adenosine or NECA. Consequently, NECA and CGS-21680-stimulated migration of hEPC were reverted using the A?A receptor antagonist ZM-241385. NECA-stimulated migration was inhibited in dose-dependent manner using MRS-1523 (Ki of 147 ± 0.016 nM), MRS-1754 (Ki of 1900 ± 0.02 nM), or ZM-241385 (Ki of 0.2 ± 0.01 nM). In conclusion, adenosine stimulates hEPC migration by activating A?A and A? but not A?B receptors and provides evidence to support a role of adenosine in modulating angiogenic capacity of hEPC. PMID:22217884

  8. Smoke Extract Impairs Adenosine Wound Healing. Implications of Smoke-Generated Reactive Oxygen Species

    PubMed Central

    Zimmerman, Matthew C.; Zhang, Hui; Castellanos, Glenda; O’Malley, Jennifer K.; Alvarez-Ramirez, Horacio; Kharbanda, Kusum; Sisson, Joseph H.; Wyatt, Todd A.

    2013-01-01

    Adenosine concentrations are elevated in the lungs of patients with asthma and chronic obstructive pulmonary disease, where it balances between tissue repair and excessive airway remodeling. We previously demonstrated that the activation of the adenosine A2A receptor promotes epithelial wound closure. However, the mechanism by which adenosine-mediated wound healing occurs after cigarette smoke exposure has not been investigated. The present study investigates whether cigarette smoke exposure alters adenosine-mediated reparative properties via its ability to induce a shift in the oxidant/antioxidant balance. Using an in vitro wounding model, bronchial epithelial cells were exposed to 5% cigarette smoke extract, were wounded, and were then stimulated with either 10 ?M adenosine or the specific A2A receptor agonist, 5?-(N-cyclopropyl)–carboxamido–adenosine (CPCA; 10 ?M), and assessed for wound closure. In a subset of experiments, bronchial epithelial cells were infected with adenovirus vectors encoding human superoxide dismutase and/or catalase or control vector. In the presence of 5% smoke extract, significant delay was evident in both adenosine-mediated and CPCA-mediated wound closure. However, cells pretreated with N-acetylcysteine (NAC), a nonspecific antioxidant, reversed smoke extract–mediated inhibition. We found that cells overexpressing mitochondrial catalase repealed the smoke extract inhibition of CPCA-stimulated wound closure, whereas superoxide dismutase overexpression exerted no effect. Kinase experiments revealed that smoke extract significantly reduced the A2A-mediated activation of cyclic adenosine monophosphate–dependent protein kinase. However, pretreatment with NAC reversed this effect. In conclusion, our data suggest that cigarette smoke exposure impairs A2A-stimulated wound repair via a reactive oxygen species–dependent mechanism, thereby providing a better understanding of adenosine signaling that may direct the development of pharmacological tools for the treatment of chronic inflammatory lung disorders. PMID:23371060

  9. Differential attenuation of the responses to adenosine and methoxamine in isolated rabbit aorta.

    PubMed

    Wiener, H L; Thalody, G P

    1993-11-01

    This article describes the functional antagonism between the responses to adenosine (through adenosine A2 receptors) and methoxamine (through alpha-1 adrenoceptors) in the adventitia- and endothelium-denuded isolated rabbit thoracic aorta. Rings were contracted with different concentrations of methoxamine and cumulative relaxation concentration-response curves (CRC) to adenosine were constructed. This protocol allowed the authors to rearrange the same data, which yielded contractile CRCs to methoxamine in the presence of adenosine. A 32-fold increase in the [methoxamine] markedly attenuated the maximal response to adenosine (80% decrease) and shifted the CRC to adenosine 10-fold to the right. By contrast, a 3000-fold increase in the [adenosine] shifted the CRC to methoxamine 3.25-fold to the right and attenuated the maximal response by a modest 18%. Analysis of these data by the operational model of agonism indicated that the efficacy parameter, tau, for adenosine or methoxamine was reduced by 99% or 71%, respectively, under these conditions. The agonist dissociation constant, KA, for adenosine (80 microM) or methoxamine (33 microM) by functional antagonism was also estimated. Use of an irreversible alpha-1 adrenoceptor antagonist allowed for the estimation of the KA for methoxamine by the receptor inactivation method using the operational model (40 microM), the Furchgott equation (48 microM) and the nested equations (42 microM) described by James et al. These results suggest that this tissue preparation is a good model to study functional antagonism quantitatively and that the functional antagonism between the responses mediated by these two receptors allows for the reliable estimation of the agonist dissociation constant for alpha-1 adrenoceptor agonists. PMID:7902436

  10. Lack of Endogenous Adenosine Tonus on Sympathetic Neurotransmission in Spontaneously Hypertensive Rat Mesenteric Artery

    PubMed Central

    Sousa, Joana Beatriz; Vieira-Rocha, Maria Sofia; Sá, Carlos; Ferreirinha, Fátima; Correia-de-Sá, Paulo; Fresco, Paula; Diniz, Carmen

    2014-01-01

    Background Increased sympathetic activity has been implicated in hypertension. Adenosine has been shown to play a role in blood flow regulation. In the present study, the endogenous adenosine neuromodulatory role, in mesenteric arteries from normotensive and spontaneously hypertensive rats, was investigated. Methods and Results The role of endogenous adenosine in sympathetic neurotransmission was studied using electrically-evoked [3H]-noradrenaline release experiments. Purine content was determined by HPLC with fluorescence detection. Localization of adenosine A1 or A2A receptors in adventitia of mesenteric arteries was investigated by Laser Scanning Confocal Microscopy. Results indicate a higher electrically-evoked noradrenaline release from hypertensive mesenteric arteries. The tonic inhibitory modulation of noradrenaline release is mediated by adenosine A1 receptors and is lacking in arteries from hypertensive animals, despite their purine levels being higher comparatively to those determined in normotensive ones. Tonic facilitatory adenosine A2A receptor-mediated effects were absent in arteries from both strains. Immunohistochemistry revealed an adenosine A1 receptors redistribution from sympathetic fibers to Schwann cells, in adventitia of hypertensive mesenteric arteries which can explain, at least in part, the absence of effects observed for these receptors. Conclusion Data highlight the role of purines in hypertension revealing that an increase in sympathetic activity in hypertensive arteries is occurring due to a higher noradrenaline/ATP release from sympathetic nerves and the loss of endogenous adenosine inhibitory tonus. The observed nerve-to-glial redistribution of inhibitory adenosine A1 receptors in hypertensive arteries may explain the latter effect. PMID:25158061

  11. In vitro of adenosine on lymphocytes and erythrocytes from horses with combined immunodeficiency.

    PubMed Central

    Magnuson, N S; Perryman, L E

    1979-01-01

    The effect of adenosine on the mitogenic response of peripheral blood lymphocytes (PBL) and on the nucleotide pools of erythrocytes from normal horses, horses heterozygous for the combined immunodeficiency (CID) trait (carriers), and foals with CID was studied. When PBL from normal, carrier, and CID horses were stimulated by phytohemagglutinin (PHA), concanavalin A, or pokeweed mitogen, [3H]thymidine uptake was inhibited by adenosine (0.1 microM) to 1.0 mM) in a dose-dependent manner. Adenosine (100 microM) mediated inhibition of [3H]thymidine uptake was prevented in both normal and carrier horse PBL by incubation with uridine. Uridine had no sparing effect on PBL from horses with CID. Differences were detected between human and horse PBL in response to adenosine and erythro-9(2-hydroxy-3-nonyl) adenine (EHNA), a competitive inhibitor of adenosine deaminase. In the first assay, mitogen-stimulated PBL from horses were more sensitive to adenosine. In the second assay, adenosine was added to PBL cultures at various times after PHA addition. Adenosine inhibited mitogenesis in horse PBL if added within the first 24 h. In human PBL cultures, adenosine inhibited mitogenesis only if added within the first 4 h. The third assay measured capacity of PHA-stimulated human and horse lymphocytes to escape inhibition by adenosine or EHNA. At the end of a 72-h culture period, horse PBL were still inhibited of mitogenesis in both human and horse PBL. With prolonged incubation (72 h), synergistic inhibition was detected only in horse PB. With high-pressure liquid chromatography, nucleotide levels in erythrocytes of normal, carrier, and CID horses were found to be similar. Incubation with adenosine produced a 1.5- to 2-fold increase in total adenine nucleotide pools in erythrocytes from all horses. However, these increases were accompanied by alterations in the relative amounts of the nucleotide components. This was seen as a significant decrease in the ATP:(AMP plus ADP plus ATP) ratio and energy charge in erythrocytes from normal horses. In contrast, the ATP:(AMP plus ADP plus ATP) ratio decreased only slightly in erythrocytes from CID horses, whereas no change in the energy charge was detected. The data from these studies indicate a difference in adenosine metabolism exists between human and horse lymphoyctes, and an abnormality may exist in purine metabolism or in an interconnecting pathway in horses with CID. PMID:447864

  12. The 254 nm low intensity and 266 nm laser photochemistry of adenosine

    Microsoft Academic Search

    Carlos E. Crespo-Hernández; Lydia Mart??nez; Aurea E. González-Sierra; Lizbeth Robles-Irizarry; Arnaldo D??az-Vázquez; Rafael Arce

    2002-01-01

    The 254nm low intensity steady-state photolysis of adenosine in aqueous solutions at different pHs and concentrations was studied. The quantum yield of photodestruction of adenosine decreases as the pH is increased: (1.7±0.1)×10?2 (pH 2.6), (1.20±0.04)×10?2 (pH 6.5) and (0.29±0.01)×10?2 (pH 13.3). For the photodestruction of adenosine and the formation of adenine the quantum yield depends on the initial ground-state concentrations

  13. N6-Adenosine Methylation in MiRNAs

    PubMed Central

    Berulava, Tea; Rahmann, Sven; Rademacher, Katrin; Klein-Hitpass, Ludgar; Horsthemke, Bernhard

    2015-01-01

    Methylation of N6-adenosine (m6A) has been observed in many different classes of RNA, but its prevalence in microRNAs (miRNAs) has not yet been studied. Here we show that a knockdown of the m6A demethylase FTO affects the steady-state levels of several miRNAs. Moreover, RNA immunoprecipitation with an anti-m6A-antibody followed by RNA-seq revealed that a significant fraction of miRNAs contains m6A. By motif searches we have discovered consensus sequences discriminating between methylated and unmethylated miRNAs. The epigenetic modification of an epigenetic modifier as described here adds a new layer to the complexity of the posttranscriptional regulation of gene expression. PMID:25723394

  14. Serum adenosine deaminase activity in bovine liver diseases.

    PubMed

    Abd Ellah, Mahmoud Rushdi; Nishimori, Kazuhiro; Goryo, Masanobu; Okada, Keiji; Yasuda, Jun

    2004-11-01

    A total of 60 cattle were examined for the presence of pathological liver lesions. The liver lesions were classified as glycogen degeneration, liver abscess, sawdust liver and fatty degeneration. The value of serum adenosine deaminase (ADA) activity was investigated as a pilot study for diagnosing liver diseases in cattle. Serum ADA activity was significantly higher in cases with glycogen degeneration (9.8 +/- 3.8 U/l) , liver abscess (10.4 +/- 3.2 U/l), sawdust liver (11.5 +/- 7.3 U/l) and fatty degeneration (20.8 +/- 7.7 U/l) than in the controls. The results indicate that ADA activity increases with the degree of hepatocellular damage. We concluded that serum ADA activity may be of value in bovine liver disease diagnosis. PMID:15585959

  15. Increased Adenosine Triphosphatase in Leukocytes of Asthmatic Children

    PubMed Central

    Coffey, Ronald G.; Hadden, John W.; Middleton, Elliott

    1974-01-01

    Adenosine triphosphatase (ATPase) activities were compared in leukocytes of asthmatic and nonasthmatic children. Both Mg2+- and Ca2+-dependent ATPase activities were significantly elevated in two membrane fractions (59 to 66%) and in a superntant fraction (68 to 72%) prepared from sonicated leukocytes of asthmatic subjects. Intact cell surface or ecto ATPase was also elevated (67 to 76%) in asthmatic leukocytes. Alternate day glucocorticosteroid therapy was associated with leukocyte ATPase activities intermediate between those for asthmatics not receiving steroids and for nonasthmatic control subjects. Incubation of normal leukocytes with 10-8 M hydrocortisone or leukocyte membranes with 10-4-10-3 M hydrocortisone in vitro also resulted in decreased ATPase activities. The elevated leukocyte ATPase activities appear to relate to the adrenergic imbalance in asthma previously characterized by reduced beta adrenergic responsiveness of adenylate cyclase and suggest the possibility of more than one enzymatic abnormality intrinsic to the asthmatic condition. PMID:4276134

  16. [Adenosine triphosphate for supraventricular tachycardia in newborns and suckling infants].

    PubMed

    Haas, N A; Pufahl, C; König, S A; Gessler, P; Teufel, M

    1994-10-01

    A previously healthy and normally developing 12-day-old female suddenly became restless and developed cold sweats, tachypnoea and tachycardia (300 beats/min). Neither electrocardiogram nor echocardiogram showed evidence of any cardiac defect. Carotid sinus massage and other vagus-stimulating manoeuvres, undertaken because paroxysmal supraventricular tachycardia (PSVT) was suspected, were unsuccessful. Before rapid digitalization, adenosine triphosphate was administered (0.1 mg/kg intravenously). Sinus rhythm was restored within about 60 s. Despite further treatment with digoxin and verapamil (4 mg/kg.d), further episodes of PSVT occurred, each again responding to ATP (0.1 to 0.3 mg/kg). There were no side effects. After 24-hour Holter ECG monitoring had revealed Wolff-Parkinson-White syndrome as cause of the PSVT, propafenone was administered (15 mg/kg daily) and has prevented further recurrence of the tachycardia. PMID:7924940

  17. Adenosine–cannabinoid receptor interactions. Implications for striatal function

    PubMed Central

    Ferré, Sergi; Lluís, Carme; Justinova, Zuzana; Quiroz, César; Orru, Marco; Navarro, Gemma; Canela, Enric I; Franco, Rafael; Goldberg, Steven R

    2010-01-01

    Adenosine and endocannabinoids are very ubiquitous non-classical neurotransmitters that exert a modulatory role on the transmission of other more ‘classical’ neurotransmitters. In this review we will focus on their common role as modulators of dopamine and glutamate neurotransmission in the striatum, the main input structure of the basal ganglia. We will pay particular attention to the role of adenosine A2A receptors and cannabinoid CB1 receptors. Experimental results suggest that presynaptic CB1 receptors interacting with A2A receptors in cortico-striatal glutamatergic terminals that make synaptic contact with dynorphinergic medium-sized spiny neurons (MSNs) are involved in the motor-depressant and addictive effects of cannabinoids. On the other hand, postsynaptic CB1 receptors interacting with A2A and D2 receptors in the dendritic spines of enkephalinergic MSNs and postsynaptic CB1 receptors in the dendritic spines of dynorphinergic MSN are probably involved in the cataleptogenic effects of cannabinoids. These receptor interactions most probably depend on the existence of a variety of heteromers of A2A, CB1 and D2 receptors in different elements of striatal spine modules. Drugs selective for the different striatal A2A and CB1 receptor heteromers could be used for the treatment of neuropsychiatric disorders and drug addiction and they could provide effective drugs with fewer side effects than currently used drugs. This article is part of a themed issue on Cannabinoids. To view the editorial for this themed issue visit http://dx.doi.org/10.1111/j.1476-5381.2010.00831.x PMID:20590556

  18. Structural and Metabolic Specificity of Methylthiocoformycin for Malarial Adenosine Deaminases

    SciTech Connect

    Ho, M.; Cassera, M; Madrid, D; Ting, L; Tyler, P; Kim, K; Almo, S; Schramm, V

    2009-01-01

    Plasmodium falciparum is a purine auxotroph requiring hypoxanthine as a key metabolic precursor. Erythrocyte adenine nucleotides are the source of the purine precursors, making adenosine deaminase (ADA) a key enzyme in the pathway of hypoxanthine formation. Methylthioadenosine (MTA) is a substrate for most malarial ADAs, but not for human ADA. The catalytic site specificity of malarial ADAs permits methylthiocoformycin (MT-coformycin) to act as a Plasmodium-specific transition state analogue with low affinity for human ADA. The structural basis for MTA and MT-coformycin specificity in malarial ADAs is the subject of speculation. Here, the crystal structure of ADA from Plasmodium vivax (PvADA) in a complex with MT-coformycin reveals an unprecedented binding geometry for 5?-methylthioribosyl groups in the malarial ADAs. Compared to malarial ADA complexes with adenosine or deoxycoformycin, 5?-methylthioribosyl groups are rotated 130 degrees. A hydrogen bonding network between Asp172 and the 3?-hydroxyl of MT-coformycin is essential for recognition of the 5?-methylthioribosyl group. Water occupies the 5?-hydroxyl binding site when MT-coformycin is bound. Mutagenesis of Asp172 destroys the substrate specificity for MTA and MT-coformycin. Kinetic, mutagenic, and structural analyses of PvADA and kinetic analysis of five other Plasmodium ADAs establish the unique structural basis for its specificity for MTA and MT-coformycin. Plasmodium gallinaceum ADA does not use MTA as a substrate, is not inhibited by MT-coformycin, and is missing Asp172. Treatment of P. falciparum cultures with coformycin or MT-coformycin in the presence of MTA is effective in inhibiting parasite growth.

  19. Structural and metabolic specificity of methylthiocoformycin for malarial adenosine deaminases†

    PubMed Central

    Ho, Meng-Chiao; Cassera, María B.; Madrid, Dennis C.; Ting, Li-Min; Tyler, Peter C.; Kim, Kami; Almo, Steven C.; Schramm, Vern L.

    2009-01-01

    Plasmodium falciparum is a purine auxotroph requiring hypoxanthine as a key metabolic precursor. Erythrocyte adenine nucleotides are the source of the purine precursors, making adenosine deaminase (ADA) a key enzyme in the pathway of hypoxanthine formation. Methylthioadenosine (MTA) is a substrate for most malarial ADAs, but not for human ADA. The catalytic site specificity of malarial ADAs permits methylthiocoformycin (MT-coformycin) to act as a Plasmodium-specific transition state analogue with low affinity for human ADA (Tyler, P. C., Taylor, E. A., Fröhlich, R. G. G. and Schramm, V. L. (2007) J. Am. Chem. Soc. 129, 6872–6879). The structural basis for MTA and MT-coformycin specificity in malarial ADAs is the subject of speculation (Larson, E. T. et al. (2008) J. Mol. Biol. 381, 975–988). Here, the crystal structure of ADA from Plasmodium vivax in complex with MT-coformycin reveals an unprecedented binding geometry for 5’-methylthioribosyl groups in the malarial ADAs. Compared to malarial ADA complexes with adenosine or deoxycoformycin, 5’-methylthioribosyl groups are rotated 130°. A hydrogen bonding network between Asp172 and the 3'-hydroxyl of MT-coformycin is essential for recognition of the 5’-methylthioribosyl group. Water occupies the 5'-hydroxyl binding site when MT-coformycin is bound. Mutagenesis of Asp172 destroys the substrate specificity for MTA and MT-coformycin. Kinetic, mutagenic and structural analyses of PvADA and kinetic analysis of five other plasmodial ADAs establishes the unique structural basis for its specificity for MTA and MT-coformycin. Plasmodium gallinaceum ADA does not use MTA as a substrate, is not inhibited by MT-coformycin and is missing Asp172. Treatment of P. falciparum cultures with coformycin or MT-coformycin in the presence of MTA is effective in inhibiting parasite growth. PMID:19728741

  20. Microthalamotomy effect during deep brain stimulation: potential involvement of adenosine and glutamate efflux.

    PubMed

    Chang, Su-Youne; Shon, Young Min; Agnesi, Filippo; Lee, Kendall H

    2009-01-01

    Deep brain stimulation (DBS) of the thalamus is widely used in humans to treat essential tremor and tremor dominant Parkinson's disease. After DBS lead implantation, tremor is often reduced even without electrical stimulation. Often called "microthalamotomy" effect, the exact mechanism is unknown, although it is presumed to be due to micro lesioning. Here, we tested whether microthalamotomy effect may, in fact, be mediated via release of neurotransmitters adenosine and glutamate, using fast scan cyclic voltammetry (FSCV) and amperometry, respectively. Implantation of microelectrodes into the ventrolateral (VL) thalamus of the rat resulted in transient rise in adenosine and glutamate level from mechanical stimulation. Similarly, high frequency stimulation (100 - 130 Hz) of the VL thalamus also resulted in adenosine and glutamate release. These results suggest that glutamate and adenosine release may be an important and unappreciated mechanism whereby mechanical stimulation via electrode implantation procedure may achieve the microthalamotomy effect. PMID:19964296

  1. Microthalamotomy effect during Deep Brain Stimulation: Potential Involvement of Adenosine and Glutamate Efflux

    PubMed Central

    Chang, Su-Youne; Shon, Young Min; Agnesi, Filippo; Lee, Kendall H.

    2010-01-01

    Deep brain stimulation (DBS) of the thalamus is widely used in humans to treat essential tremor and tremor dominant Parkinson’s disease. After DBS lead implantation, tremor is often reduced even without electrical stimulation. Often called “microthalamotomy” effect, the exact mechanism is unknown, although it is presumed to be due to micro lesioning. Here, we tested whether microthalamotomy effect may, in fact, be mediated via release of neurotransmitters adenosine and glutamate, using fast scan cyclic voltammetry (FSCV) and amperometry, respectively. Implantation of microelectrodes into the ventrolateral (VL) thalamus of the rat resulted in transient rise in adenosine and glutamate level from mechanical stimulation. Similarly, high frequency stimulation (100 – 130 Hz) of the VL thalamus also resulted in adenosine and glutamate release. These results suggest that glutamate and adenosine release may be an important and unappreciated mechanism whereby mechanical stimulation via electrode implantation procedure may achieve the microthalamotomy effect. PMID:19964296

  2. Methotrexate inhibits neutrophil function by stimulating adenosine release from connective tissue cells.

    PubMed Central

    Cronstein, B N; Eberle, M A; Gruber, H E; Levin, R I

    1991-01-01

    Although commonly used to control a variety of inflammatory diseases, the mechanism of action of a low dose of methotrexate remains a mystery. Methotrexate accumulates intracellularly where it may interfere with purine metabolism. Therefore, we determined whether a 48-hr pretreatment with methotrexate affected adenosine release from [14C]adenine-labeled human fibroblasts and umbilical vein endothelial cells. Methotrexate significantly increased adenosine release by fibroblasts from 4 +/- 1% to 31 +/- 6% of total purine released (EC50, 1 nM) and by endothelial cells from 24 +/- 4% to 42 +/- 7%. Methotrexate-enhanced adenosine release from fibroblasts was further increased to 51 +/- 4% (EC50, 6 nM) and from endothelial cells was increased to 58 +/- 5% of total purine released by exposure to stimulated (fMet-Leu-Phe at 0.1 microM) neutrophils. The effect of methotrexate on adenosine release was not due to cytotoxicity since cells treated with maximal concentrations of methotrexate took up [14C]adenine and released 14C-labeled purine (a measure of cell injury) in a manner identical to control cells. Methotrexate treatment of fibroblasts dramatically inhibited adherence to fibroblasts by both unstimulated neutrophils (IC50, 9 nM) and stimulated neutrophils (IC50, 13 nM). Methotrexate treatment inhibited neutrophil adherence by enhancing adenosine release from fibroblasts since digestion of extracellular adenosine by added adenosine deaminase completely abrogated the effect of methotrexate on neutrophil adherence without, itself, affecting adherence. One hypothesis that explains the effect of methotrexate on adenosine release is that, by inhibition of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) transformylase, methotrexate induces the accumulation of AICAR, the nucleoside precursor of which (5-aminoimidazole-4-carboxamide ribonucleoside referred to hereafter as acadesine) has previously been shown to cause adenosine release from ischemic cardiac tissue. We found that acadesine also promotes adenosine release from and inhibits neutrophil adherence to connective tissue cells. The observation that the antiinflammatory actions of methotrexate are due to the capacity of methotrexate to induce adenosine release may form the basis for the development of an additional class of antiinflammatory drugs. PMID:2006182

  3. Adenosine-induced presynaptic inhibition of IPSCs and EPSCs in rat hypothalamic supraoptic nucleus neurones

    PubMed Central

    Oliet, Stéphane H R; Poulain, Dominique A

    1999-01-01

    The effects of adenosine on synaptic transmission in magnocellular neurosecretory cells were investigated using whole-cell patch-clamp recordings in acute rat hypothalamic slices that included the supraoptic nucleus. Adenosine reversibly reduced the amplitude of evoked inhibitory (IPSCs) and excitatory (EPSCs) postsynaptic currents in a dose-dependent manner (IC50? 10 ?m for both types of current). Depression of IPSCs and EPSCs by adenosine was reversed by the application of the A1 adenosine receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT; 10 ?m). When pairs of stimuli were given at short intervals, adenosine inhibitory action was always less effective on the second of the two responses than on the first, resulting in an increased paired-pulse facilitation and suggesting a presynaptic site of action. This observation was confirmed by analysis of spontaneous miniature synaptic currents whose frequency, but not amplitude or kinetics, was reversibly reduced by 100 ?M adenosine. CPT had no effect on synaptic responses evoked at a low frequency of stimulation (0.05–0.5 Hz), indicating the absence of tonic activation of A1 receptors under these recording conditions. However, CPT inhibited a time-dependent depression of both IPSCs and EPSCs induced during a 1 Hz train of stimuli. Taken together, these results suggest that adenosine can be released within the supraoptic nucleus at a concentration sufficient to inhibit the release of GABA and glutamate via the activation of presynaptic A1 receptors. By its inhibitory feedback action on the major afferent inputs to oxytocin and vasopressin neurones, adenosine could optimally adjust electrical and secretory activities of hypothalamic magnocellular neurones. PMID:10545146

  4. Xanthine derivatives as antagonists at A 1 and A 2 adenosine receptors

    Microsoft Academic Search

    U. Schwabe; D. Ukena; M. J. Lohse

    1985-01-01

    A variety of alkylxanthines has been comparatively examined as antagonists of A1 adenosine receptors in rat fat cells, rat and bovine cerebral cortex and of A2 adenosine receptors in human platelets. With few exceptions all xanthine derivatives with 7-position substituents such as diprophylline, proxyfylline, pentoxifylline and etofylline were less potent antagonists than xanthine itself which hadKi-values of 170 µmol\\/l (A1)

  5. Radial distribution function descriptors: an alternative for predicting A 2 A adenosine receptors agonists

    Microsoft Academic Search

    Maykel Pérez González; Carmen Terán; Marta Teijeira; Aliuska Morales Helguera

    2006-01-01

    The Radial Distribution Function approach has been applied to the study of the A2 A adenosine receptors agonist effect of 29 adenosine analogues: N6–arylcarbamoyl, 2-arylalkynyl-N6–arylcarbamoyl, and N6–carboxamido derivatives. A model able to describe around 85% of the variance in the experimental activity was developed with the use of the mentioned approach. In contrast, no one of nine different approaches, including the

  6. Regeneration of adenosine 5'-triphosphate using ATPase immobilized in an artificial membrane

    E-print Network

    VanDuker, Frank Cal

    1988-01-01

    REGENERATION OF ADENOSINE 5' ? TRIPHOSPHATE USING ATPASE IMMOBILIZED IN AN ARTIFICIAL MEMBRANE A Thesis by FRANK CAL VANDUKER, JR. Submitted to the Office of Graduate Studies of Texas ASM University in partial fu161lment of the requirement... for the degree of MASTER OF SCIENCE December 1988 Major Subject: Chemical Engineering REGENERATION OF ADENOSINE O' ? TRIPHOSPHATE USING ATPASE IMMOBILIZED IN AN ARTIFICIAL MEMBRANE A Thesis by FRANK CAL VANDUKER, JR. Approved as to style and content by...

  7. Adenosine treatment of supraventricular tachycardia following epidural test dose: a case study.

    PubMed

    Merson, N

    1993-10-01

    This is a case report of supraventricular tachycardia following initiation of epidural analgesia with use of an epinephrine test dose in a parturient during active labor. Vagal stimulatory efforts failed to interrupt the arrhythmia, but treatment with adenosine was successful. Fetal monitoring with a scalp electrode provided evidence of fetal well-being throughout the episode. Adenosine was chosen because of its safety for both the mother and the fetus and its lack of the hypotensive effect often seen with verapamil. PMID:8291402

  8. Radiation Damage of DNA Constituents: Esr Study of the ADENOSINE:5IODOURACIL Cocrystal

    Microsoft Academic Search

    Rafael Zamorano

    1986-01-01

    Single cocrystals of adenosine:5-iodouracil and partially deuterated adenosine:5-iodouracil were irradiated at 4.2K, 77K, and 300K with X-rays from a 3Mev Van de Graaff electron accelerator. Several types of free radicals were produced by the radiation and were studied by X-Band and Q-Band ESR from 77K to 300K. Six radicals were identified. Two electron addition products (radicals I1 and As1) and

  9. How Safe Is Adenosine When Used as a Pharmacologic Stressing Agent in Myocardial Perfusion Scintigraphy?

    Microsoft Academic Search

    Iman Al-Shammeri; Hani Salman; Ezzat Higazi; Raghu Halker; Mohammed Naeem; Azu Owunwanne

    1997-01-01

    Myocardial perfusion imaging is used in the assessment of coronary artery disease by stressing patients either physically or pharmacologically. Adenosine was used as a pharmacologic stressor when administered at a dose of 0.14 mg\\/kg\\/min for 6 min to determine its safety at this dose level. Twenty patients referred for myocardial perfusion imaging were stressed with adenosine. The protocol was completed

  10. Adenosine A 3 receptor agonist acts as a homeostatic regulator of bone marrow hematopoiesis

    Microsoft Academic Search

    Michal Hofer; Milan Pospíšil; Vladimír Znojil; Ji?ina Holá; Antonín Vacek; Denisa Štreitová

    2007-01-01

    The present study was performed to define the optimum conditions of the stimulatory action of the adenosine A3 receptor agonist, N6-(3-iodobenzyl)adenosine-5?-N-methyluronamide (IB-MECA), on bone marrow hematopoiesis in mice. Effects of 2-day treatment with IB-MECA given at single doses of 200nmol\\/kg twice daily were investigated in normal mice and in mice whose femoral bone marrow cells were either depleted or regenerating

  11. Intravenous adenosine (adenoscan) versus exercise in the noninvasive assessment of coronary artery disease by SPECT

    SciTech Connect

    LaManna, M.M.; Mohama, R.; Slavich, I.L. 3d.; Lumia, F.J.; Cha, S.D.; Rambaran, N.; Maranhao, V. (Deborah Heart and Lung Center, Browns Mills, NJ (USA))

    1990-11-01

    Fifteen patients at a mean age of 58 underwent adenosine and maximal exercise thallium SPECT imaging. All scans were performed 1 week apart and within 4 weeks of cardiac catheterization. SPECT imaging was performed after the infusion of 140 micrograms/kg/min of adenosine for 6 minutes. Mean heart rate increment during adenosine administration was 67 +/- 3.7 to 77 +/- 4.1. Mean blood pressure was 136 +/- 7.2 to 135 +/- 6.2 systolic and 78 +/- 1.8 to 68 +/- 2.6 diastolic. No adverse hemodynamic effects were observed. There were no changes in PR or QRS in intervals. Five stress ECGs were ischemic. No ST changes were observed with adenosine. Although 68% of the patients had symptoms of flushing, light-headedness, and dizziness during adenosine infusion, symptoms resolved within 1 minute of dosage adjustment or termination of the infusion in all but one patient, who required theophylline. Sensitivity for coronary artery detection was 77% and specificity 100%. Concordance between adenoscans and exercise thallium scintigraphy was high (13/15 = 87%). In two patients, there were minor scintigraphic differences. The authors conclude that adenosine is a sensitive, specific, and safe alternative to exercise testing in patients referred for thallium imaging and may be preferable to dipyridamole.

  12. Interaction of adenosine and naloxone on regional cerebral blood flow in morphine-dependent rats.

    PubMed

    Khorasani, Mahdi Zahedi; Hajizadeh, Sohrab; Fathollahi, Yaghoub; Semnanian, Saeed

    2006-04-21

    The present research aimed at investigating the opioid-adenosine interaction on regional cerebral blood flow (rCBF). Therefore rCBF in the sensory cortex of morphine-naive and -dependent rats was measured using the laser-Doppler flowmetry technique. The results showed that adenosine (10(-5), 10(-4), 10(-3) M) significantly increased rCBF in morphine-dependent rats (MDR) (P < 0.01). This effect was inhibited by theophylline (5 x 10(-5) M). Also systemic naloxone (0.5, 1.5 and 3 mg/kg, s.c.) significantly increased rCBF in MDR and it was accompanied by elevated blood pressure and heart rate. Local adenosine (10(-4) M) significantly augmented naloxone (0.5 mg/kg)-induced increase in rCBF of MDR but had no significant effect on naloxone's (1.5 and 3 mg/kg) increasing effect on rCBF. Theophylline also has no effect on naloxone increasing effect on rCBF. These data suggest that adenosine receptors responsiveness increase in sensory cortex of MDR. Naloxone also highly increased rCBF of MDR that probably not interfere with adenosine receptors. Also, it seems that adenosine acts as a modulator in rCBF regulation of morphine-dependent and morphine withdrawal rats. PMID:16626652

  13. Protection against methamphetamine-induced neurotoxicity to neostriatal dopaminergic neurons by adenosine receptor activation.

    PubMed

    Delle Donne, K T; Sonsalla, P K

    1994-12-01

    Methamphetamine (METH)-induced neurotoxicity to nigrostriatal dopaminergic neurons in experimental animals appears to have a glutamatergic component because blockade of N-methyl-D-aspartate receptors prevents the neuropathologic consequences. Because adenosine affords neuroprotection against various forms of glutamate-mediated neuronal damage, the present studies were performed to investigate whether adenosine plays a protective role in METH-induced toxicity. METH-induced decrements in neostriatal dopamine content and tyrosine hydroxylase activity in mice were potentiated by concurrent treatment with caffeine, a nonselective adenosine antagonist that blocks both A1 and A2 adenosine receptors. In contrast, chronic treatment of mice with caffeine through their drinking water for 4 weeks, which increased the number of adenosine A1 receptors in the neostriatum and frontal cortex, followed by drug washout, prevented the neurochemical changes produced by the treatment of mice with METH treatment. In contrast, this treatment did not prevent 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine-induced dopaminergic neurotoxicity. Furthermore, concurrent administration of cyclopentyladenosine, an adenosine A1 receptor agonist, attenuated the METH-induced neurochemical changes. This protection by cyclopentyladenosine was blocked by cyclopentyltheophylline, an A1 receptor antagonist. These results indicate that activation of A1 receptors can protect against METH-induced neurotoxicity in mice. PMID:7996441

  14. Adenosine mediated desensitization of cAMP signaling enhances T-cell responses

    PubMed Central

    Yang, Ailian; Mucsi, Ashley D.; Desrosiers, Melanie D.; Chen, Jiang-Fan; Schnermann, Jürgen B.; Blackburn, Michael R.; Shi, Yan

    2012-01-01

    Adenosine has long been regarded as a crucial anti-inflammatory agent that protects the host from excessive damage. It has been reported to play an important role in suppressing immune activation, particularly that of T cells. However, it is a general observation that induction of T-cell activation is an efficient event despite the high adenosine levels that are often present in the affected host due to injury or stress. We report here that prior to antigenic stimulation via TCR/CD3, exposure of T cells to adenosine desensitizes adeno-sine receptors, so as to create a window of time where the T cells are insensitive to this ubiquitous suppressor. T cells from mice that were pre-exposed to this manipulation showed stronger responses to antigenic stimulation; therefore, the P1 adenosine receptor desensitization demonstrated an adjuvant-like effect. Our results suggest that adenosine receptor desensitization may be a mechanism for T cells to escape the general suppression during early points of T-cell activation and may emerge as a potential alternative for vaccine adjuvants. PMID:19950175

  15. A ketogenic diet suppresses seizures in mice through adenosine A? receptors.

    PubMed

    Masino, Susan A; Li, Tianfu; Theofilas, Panos; Sandau, Ursula S; Ruskin, David N; Fredholm, Bertil B; Geiger, Jonathan D; Aronica, Eleonora; Boison, Detlev

    2011-07-01

    A ketogenic diet (KD) is a high-fat, low-carbohydrate metabolic regimen; its effectiveness in the treatment of refractory epilepsy suggests that the mechanisms underlying its anticonvulsive effects differ from those targeted by conventional antiepileptic drugs. Recently, KD and analogous metabolic strategies have shown therapeutic promise in other neurologic disorders, such as reducing brain injury, pain, and inflammation. Here, we have shown that KD can reduce seizures in mice by increasing activation of adenosine A1 receptors (A1Rs). When transgenic mice with spontaneous seizures caused by deficiency in adenosine metabolism or signaling were fed KD, seizures were nearly abolished if mice had intact A1Rs, were reduced if mice expressed reduced A1Rs, and were unaltered if mice lacked A1Rs. Seizures were restored by injecting either glucose (metabolic reversal) or an A1R antagonist (pharmacologic reversal). Western blot analysis demonstrated that the KD reduced adenosine kinase, the major adenosine-metabolizing enzyme. Importantly, hippocampal tissue resected from patients with medically intractable epilepsy demonstrated increased adenosine kinase. We therefore conclude that adenosine deficiency may be relevant to human epilepsy and that KD can reduce seizures by increasing A1R-mediated inhibition. PMID:21701065

  16. Determination of adenosine nucleotides in cultured cells by ion-pairing liquid chromatography–electrospray ionization mass spectrometry

    Microsoft Academic Search

    Tianxiu Qian; Zongwei Cai; M. S Yang

    2004-01-01

    A method using ion-pairing liquid chromatography–mass spectrometry (MS) was developed for analyzing adenosine 5?-monophosphate (AMP), adenosine 5?-diphosphate (ADP), and adenosine 5?-triphosphate (ATP) in cellular extracts. Dimethylhexylamine (DMHA) was used as ion-pairing agent to retain and separate the analytes on a reversed-phase microbore column with a gradient program. Positive-ion electrospray ionization–MS was applied for the detection because of the use of

  17. Comonitoring of adenosine and dopamine using the Wireless Instantaneous Neurotransmitter Concentration System: proof of principle

    PubMed Central

    Shon, Young-Min; Chang, Su-Youne; Tye, Susannah J.; Kimble, Christopher J.; Bennet, Kevin E.; Blaha, Charles D.; Lee, Kendall H.

    2010-01-01

    Object The authors of previous studies have demonstrated that local adenosine efflux may contribute to the therapeutic mechanism of action of thalamic deep brain stimulation (DBS) for essential tremor. Real-time monitoring of the neurochemical output of DBS-targeted regions may thus advance functional neurosurgical procedures by identifying candidate neurotransmitters and neuromodulators involved in the physiological effects of DBS. This would in turn permit the development of a method of chemically guided placement of DBS electrodes in vivo. Designed in compliance with FDA-recognized standards for medical electrical device safety, the authors report on the utility of the Wireless Instantaneous Neurotransmitter Concentration System (WINCS) for real-time comonitoring of electrical stimulation–evoked adenosine and dopamine efflux in vivo, utilizing fast-scan cyclic voltammetry (FSCV) at a polyacrylonitrile-based (T-650) carbon fiber microelectrode (CFM). Methods The WINCS was used for FSCV, which consisted of a triangle wave scanned between ?0.4 and +1.5 V at a rate of 400 V/second and applied at 10 Hz. All voltages applied to the CFM were with respect to an Ag/AgCl reference electrode. The CFM was constructed by aspirating a single T-650 carbon fiber (r = 2.5 ?m) into a glass capillary and pulling to a microscopic tip using a pipette puller. The exposed carbon fiber (the sensing region) extended beyond the glass insulation by ? 50 ?m. Proof of principle tests included in vitro measurements of adenosine and dopamine, as well as in vivo measurements in urethane-anesthetized rats by monitoring adenosine and dopamine efflux in the dorsomedial caudate putamen evoked by high-frequency electrical stimulation of the ventral tegmental area and substantia nigra. Results The WINCS provided reliable, high-fidelity measurements of adenosine efflux. Peak oxidative currents appeared at +1.5 V and at +1.0 V for adenosine, separate from the peak oxidative current at +0.6 V for dopamine. The WINCS detected subsecond adenosine and dopamine efflux in the caudate putamen at an implanted CFM during high-frequency stimulation of the ventral tegmental area and substantia nigra. Both in vitro and in vivo testing demonstrated that WINCS can detect adenosine in the presence of other easily oxidizable neurochemicals such as dopamine comparable to the detection abilities of a conventional hardwired electrochemical system for FSCV. Conclusions Altogether, these results demonstrate that WINCS is well suited for wireless monitoring of high-frequency stimulation-evoked changes in brain extracellular concentrations of adenosine. Clinical applications of selective adenosine measurements may prove important to the future development of DBS technology. PMID:19731995

  18. Inhibition of Platelet Activation and Thrombus Formation by Adenosine and Inosine: Studies on Their Relative Contribution and Molecular Modeling

    PubMed Central

    Fuentes, Eduardo; Pereira, Jaime; Mezzano, Diego; Alarcón, Marcelo; Caballero, Julio; Palomo, Iván

    2014-01-01

    Background The inhibitory effect of adenosine on platelet aggregation is abrogated after the addition of adenosine-deaminase. Inosine is a naturally occurring nucleoside degraded from adenosine. Objectives The mechanisms of antiplatelet action of adenosine and inosine in vitro and in vivo, and their differential biological effects by molecular modeling were investigated. Results Adenosine (0.5, 1 and 2 mmol/L) inhibited phosphatidylserine exposure from 52±4% in the control group to 44±4 (p<0.05), 29±2 (p<0.01) and 20±3% (p<0.001). P-selectin expression in the presence of adenosine 0.5, 1 and 2 mmol/L was inhibited from 32±4 to 27±2 (p<0.05), 14±3 (p<0.01) and 9±3% (p<0.001), respectively. At the concentrations tested, only inosine to 4 mmol/L had effect on platelet P-selectin expression (p<0.05). Adenosine and inosine inhibited platelet aggregation and ATP release stimulated by ADP and collagen. Adenosine and inosine reduced collagen-induced platelet adhesion and aggregate formation under flow. At the same concentrations adenosine inhibited platelet aggregation, decreased the levels of sCD40L and increased intraplatelet cAMP. In addition, SQ22536 (an adenylate cyclase inhibitor) and ZM241385 (a potent adenosine receptor A2A antagonist) attenuated the effect of adenosine on platelet aggregation induced by ADP and intraplatelet level of cAMP. Adenosine and inosine significantly inhibited thrombosis formation in vivo (62±2% occlusion at 60 min [n?=?6, p<0.01] and 72±1.9% occlusion at 60 min, [n?=?6, p<0.05], respectively) compared with the control (98±2% occlusion at 60 min, n?=?6). A2A is the adenosine receptor present in platelets; it is known that inosine is not an A2A ligand. Docking of adenosine and inosine inside A2A showed that the main difference is the formation by adenosine of an additional hydrogen bond between the NH2 of the adenine group and the residues Asn253 in H6 and Glu169 in EL2 of the A2A receptor. Conclusion Therefore, adenosine and inosine may represent novel agents lowering the risk of arterial thrombosis. PMID:25393959

  19. Differential Coronary Microvascular Exchange Responses to Adenosine: Roles of Receptor and Microvessel Subtypes

    PubMed Central

    WANG, JIANJIE; WHITT, STEVAN P.; RUBIN, LEONA J.; HUXLEY, VIRGINIA H.

    2012-01-01

    Objective To assess the role of adenosine receptors in the regulation of coronary microvascular permeability to porcine serum albumin (PsPSA). Methods Solute flux was measured in single perfused arterioles and venules isolated from pig hearts using fluorescent dye-labeled probes by microspectro-fluorometry. Messenger RNA, protein, and cellular distribution of adenosine receptors in arterioles and venules were analyzed by RT-PCR, immunoblot, and immunofluorescence. Results Control venule PsPSA (10.7 ± 4.8 × 10?7 cm s?1) was greater than that of arterioles (6.4 ± 2.8 × 10?7 cm · s?1; p <.05). Arteriolar PsPSA decreased ( p <.05) with adenosine suffusion over the range from 10?8 to 10?5 M, while venular PsPSA did not change. The nonselective A1 and A2 receptor antagonist, 8-(p-sulfophenyl) theophylline, blocked the adenosine-induced decrease in arteriolar PsPSA. Messenger RNA for adenosine A1,A2A,A2B, and A3 receptors was expressed in arterioles and venules. Protein for A1, A2A, and A2B, but not A3, was detected in both microvessel types and was further demonstrated on vascular endothelial cells. Conclusion Arteriolar PsPSA decreases with adenosine suffusion but not venular PsPSA. Adenosine A1, A2A, and A2B receptors are expressed in both arterioles and venules. Selective receptor-linked cellular signaling mechanisms underlying the regulation of permeability remain to be determined. PMID:16020078

  20. Adenosine, type 1 receptors: role in proximal tubule Na+ reabsorption

    PubMed Central

    Welch, William J

    2015-01-01

    Adenosine type 1 receptor (A1-AR) antagonists induce diuresis and natriuresis in experimental animals and humans. Much of this effect is due to inhibition of A1-ARs in the proximal tubule, which is responsible for 60–70% of the reabsorption of filtered Na+ and fluid. Intratubular application of receptor antagonists indicates that A1-AR mediates a portion of Na+ uptake in PT and PT cells, via multiple transport systems, including Na+/H+ exchanger-3 (NHE3), Na+/PO4? co-transporter and Na+-dependent glucose transporter, SGLT. Renal microperfusion and recollection studies have shown that fluid reabsorption is reduced by A1-AR antagonists and is lower in A1-AR KO mice., compared to WT mice. Absolute proximal reabsorption (APR) measured by free-flow micropuncture is equivocal, with studies that show either lower APR or similar APR in A1-AR KO mice, compared to WT mice. Inhibition of A1-ARs lowers elevated blood pressure in models of salt-sensitive hypertension, partially due to their effects in the proximal tubule. PMID:25345761

  1. Cyclic Adenosine 3?:5?-Monophosphate in Moss Protonema

    PubMed Central

    Handa, Avtar Krishan; Johri, Man Mohan

    1977-01-01

    From the protonema of the moss Funaria hygrometrica (L.) Sibth, a factor indistinguishable from cyclic adenosine 3?:5?-monophosphate (cAMP) has been isolated. The factor stimulated the activity of protein kinase from rabbit skeletal muscle and co-chromatographed with authentic cAMP in two solvent systems. Its ability to stimulate protein kinase activity was completely abolished by 3?:5?-cyclic nucleotide phosphodiesterase, the rate of inactivation being similar to that of authentic cAMP. Based on these properties, this factor is identified as 3?,5?-cAMP. Cyclic AMP could be readily removed from the cells and washing the cells with water reduced the endogenous level of cAMP by 2- to 3-fold. A comparison of cAMP levels by protein kinase and Gilman assays was made. The intracellular levels determined by protein kinase assay were about 7-fold lower than the values obtained by Gilman assay. This discrepancy was due to the presence of unidentified compounds which were completely degraded by 3?:5?-cyclic nucleotide phosphodiesterase. Although these displaced labeled cAMP in the Gilman assay, they did not stimulate the protein kinase activity. The protonema may contain cyclic nucleotides other than cAMP; these will not be detected in the protein kinase assay due to the specificity of this reaction. The crude extracts were found to be unsuitable for assaying cAMP by either method. PMID:16659878

  2. Intracellular Adenosine Triphosphate Deprivation through Lanthanide-Doped Nanoparticles.

    PubMed

    Tian, Jing; Zeng, Xiao; Xie, Xiaoji; Han, Sanyang; Liew, Oi-Wah; Chen, Yei-Tsung; Wang, Lianhui; Liu, Xiaogang

    2015-05-27

    Growing interest in lanthanide-doped nanoparticles for biological and medical uses has brought particular attention to their safety concerns. However, the intrinsic toxicity of this new class of optical nanomaterials in biological systems has not been fully evaluated. In this work, we systematically evaluate the long-term cytotoxicity of lanthanide-doped nanoparticles (NaGdF4 and NaYF4) to HeLa cells by monitoring cell viability (mitochondrial activity), adenosine triphosphate (ATP) level, and cell membrane integrity (lactate dehydrogenase release), respectively. Importantly, we find that ligand-free lanthanide-doped nanoparticles induce intracellular ATP deprivation of HeLa cells, resulting in a significant decrease in cell viability after exposure for 7 days. We attribute the particle-induced cell death to two distinct cell death pathways, autophagy and apoptosis, which are primarily mediated via the interaction between the nanoparticle and the phosphate group of cellular ATP. The understanding gained from the investigation of cytotoxicity associated with lanthanide-doped nanoparticles provides keen insights into the safe use of these nanoparticles in biological systems. PMID:25923914

  3. ADA (adenosine deaminase) gene therapy enters the competition

    SciTech Connect

    Culliton, B.J.

    1990-08-31

    Around the world, some 70 children are members of a select and deadly club. Born with an immune deficiency so severe that they will die of infection unless their immune systems can be repaired, they have captured the attention of would-be gene therapists who believe that a handful of these kids--the 15 or 20 who lack functioning levels of the enzyme adenosine deaminase (ADA)--could be saved by a healthy ADA gene. A team of gene therapists is ready to put the theory to the test. In April 1987, a team of NIH researchers headed by R. Michael Blaese and W. French Anderson came up with the first formal protocol to introduce a healthy ADA gene into an unhealthy human. After 3 years of line-by-line scrutiny by five review committees, they have permission to go ahead. Two or three children will be treated in the next year, and will be infused with T lymphocytes carrying the gene for ADA. If the experiment works, the ADA gene will begin producing normal amounts of ADA. An interesting feature of ADA deficiency, that makes it ideal for initial gene studies, is that the amount of ADA one needs for a healthy immune system is quite variable. Hence, once inside a patient's T cells, the new ADA gene needs only to express the enzyme in moderate amounts. No precise gene regulation is necessary.

  4. Brain to blood efflux transport of adenosine: blood-brain barrier studies in the rat.

    PubMed

    Isakovic, Aleksandra J; Abbott, N Joan; Redzic, Zoran B

    2004-07-01

    The blood-brain barrier (BBB) efflux transport of [(14)C] adenosine was studied using the brain efflux index (BEI) technique. BEI increased linearly over the first 2 min after injection, with deviation from linearity thereafter; 90.12 +/- 1.5% of the injected [(14)C] radioactivity remained within the brain after 20 min. The remaining tracer appears to be mainly intracellular, trapped by phosphorylation, as an almost linear increase of BEI over 20 min was observed after intracerebral injection of [(14)C] adenosine together with 5-iodo tubercidin. The BBB efflux clearance of [(14)C] radioactivity was estimated to be 27.62 +/- 5.2 micro L/min/g, almost threefold higher than the BBB influx clearance estimated by the brain uptake index technique. High-performance liquid chromatography (HPLC) analysis of blood plasma collected from the jugular vein after the intracerebral injection revealed metabolic breakdown of [(14)C] adenosine into nucleobases. The BBB efflux transport was saturable with apparent K(m) = 13.22 +/- 1.75 micro m and V(max) = 621.07 +/- 71.22 pmole/min/g, which indicated that BBB efflux in vivo is 6.2-12p mole/min/g, negligible when compared to the reported rate of adenosine uptake into neurones/glia. However, these kinetic parameters also suggest that under conditions of elevated ISF adenosine in hypoxia/ischaemia, BBB efflux transport could increase up to 25% of the uptake into neurones/glia and become an important mechanism to oppose the rise in ISF concentration. HPLC-fluorometry detected 93.6 +/- 5.25 nm of adenosine in rat plasma, which is 17- to 220-fold lower than the reported K(m) of adenosine BBB influx in rat. Together with the observed rapid degradation inside endothelial cells, this indicated negligible BBB influx of intact adenosine under resting conditions. Cross-inhibition studies showed that unlabelled inosine, adenine and hypoxanthine caused a decrease in BBB efflux of [(14)C] radioactivity in a concentration-dependent manner, with K(i) of 16.7 +/- 4.88, 65.1 +/- 14.1 and 71.1 +/- 16.9 micro m, respectively. This could be due to either competition of unlabelled molecules with [(14)C] adenosine or competition with its metabolites hypoxanthine and adenine for the same transport sites. PMID:15228584

  5. Interactions between responses mediated by activation of adenosine A2 receptors and alpha 1-adrenoceptors in the rabbit isolated aorta.

    PubMed Central

    Wiener, H. L.; Thalody, G. P.; Maayani, S.

    1993-01-01

    1. This paper describes aspects of the functional antagonism between the responses mediated by activated alpha 1-adrenoceptors and adenosine A2 receptors in the adventitia- and endothelium-denuded aorta of the rabbit. 2. Adenosine A2 receptor agonists relaxed aortic rings pre-contracted with phenylephrine. The relaxation response was agonist concentration-dependent and saturable. The respective contractile and relaxation responses were stable, reproducible, and reversible. 3. Increasing the phenylephrine concentration caused a progressive attenuation of the action of adenosine A2 receptor agonists, consisting of a decreased maximal response and a dextral shift of the adenosine agonist concentration-response curve. This functional antagonism could be completely reversed upon removal of adenosine by either the addition of adenosine deaminase or by wash-out of the adenosine agonist from the tissue. The relaxation response to the adenosine A2 receptor partial agonists, N6-cyclohexyladenosine and R-(-)-N6-(2-phenylisopropyl)adenosine, was abolished at higher phenylephrine concentrations (e.g. 30 EC50). 4. A 1000 fold increase in the adenosine concentration was required to shift the value of the EC50 of phenylephrine six fold, while a similar increase in the value of the EC50 of adenosine could be elicited by only a 32 fold increase in the phenylephrine concentration. A 30 fold increase in the phenylephrine concentration shifted the value of the EC50 of 5'-N-ethylcarboxamidoadenosine four fold. 5. Analysis of the functional antagonism between the responses mediated by these receptors using the Black & Leff (1983) operational model of agonism allowed for the estimation of the agonist dissociation constant, KA, and the apparent efficacy, tau, for both phenylephrine and adenosine A2 receptor agonists. Increasing the concentration of phenylephrine reduced the value of tau for adenosine agonists in a concentration-dependent and saturable manner. Similarly, increasing the concentration of adenosine reduced the value of tau for phenylephrine in a concentration-dependent and saturable manner. The phenylephrine KA value obtained by the method of functional antagonism (1.9 microM) was similar to that obtained by the receptor inactivation method (2.1 microM). 6. Partial occlusion of the alpha 1-adrenoceptor by the alkylating agent, dibenamine, demonstrated that the magnitude of the adenosine A2 receptor-mediated relaxation was inversely proportional to the number of functional alpha 1-adrenoceptors. 7. It is concluded that the magnitude of functional antagonism is proportional to the stimulus elicited through either receptor. We propose that this tissue preparation and pair of receptors is a good model to study quantitative aspects of functional antagonism between activated receptors. PMID:8395286

  6. Interactions between responses mediated by activation of adenosine A2 receptors and alpha 1-adrenoceptors in the rabbit isolated aorta.

    PubMed

    Wiener, H L; Thalody, G P; Maayani, S

    1993-06-01

    1. This paper describes aspects of the functional antagonism between the responses mediated by activated alpha 1-adrenoceptors and adenosine A2 receptors in the adventitia- and endothelium-denuded aorta of the rabbit. 2. Adenosine A2 receptor agonists relaxed aortic rings pre-contracted with phenylephrine. The relaxation response was agonist concentration-dependent and saturable. The respective contractile and relaxation responses were stable, reproducible, and reversible. 3. Increasing the phenylephrine concentration caused a progressive attenuation of the action of adenosine A2 receptor agonists, consisting of a decreased maximal response and a dextral shift of the adenosine agonist concentration-response curve. This functional antagonism could be completely reversed upon removal of adenosine by either the addition of adenosine deaminase or by wash-out of the adenosine agonist from the tissue. The relaxation response to the adenosine A2 receptor partial agonists, N6-cyclohexyladenosine and R-(-)-N6-(2-phenylisopropyl)adenosine, was abolished at higher phenylephrine concentrations (e.g. 30 EC50). 4. A 1000 fold increase in the adenosine concentration was required to shift the value of the EC50 of phenylephrine six fold, while a similar increase in the value of the EC50 of adenosine could be elicited by only a 32 fold increase in the phenylephrine concentration. A 30 fold increase in the phenylephrine concentration shifted the value of the EC50 of 5'-N-ethylcarboxamidoadenosine four fold. 5. Analysis of the functional antagonism between the responses mediated by these receptors using the Black & Leff (1983) operational model of agonism allowed for the estimation of the agonist dissociation constant, KA, and the apparent efficacy, tau, for both phenylephrine and adenosine A2 receptor agonists. Increasing the concentration of phenylephrine reduced the value of tau for adenosine agonists in a concentration-dependent and saturable manner. Similarly, increasing the concentration of adenosine reduced the value of tau for phenylephrine in a concentration-dependent and saturable manner. The phenylephrine KA value obtained by the method of functional antagonism (1.9 microM) was similar to that obtained by the receptor inactivation method (2.1 microM). 6. Partial occlusion of the alpha 1-adrenoceptor by the alkylating agent, dibenamine, demonstrated that the magnitude of the adenosine A2 receptor-mediated relaxation was inversely proportional to the number of functional alpha 1-adrenoceptors. 7. It is concluded that the magnitude of functional antagonism is proportional to the stimulus elicited through either receptor. We propose that this tissue preparation and pair of receptors is a good model to study quantitative aspects of functional antagonism between activated receptors. PMID:8395286

  7. Adenosine uptake is the major effector of extracellular ATP toxicity in human cervical cancer cells

    PubMed Central

    Mello, Paola de Andrade; Filippi-Chiela, Eduardo Cremonese; Nascimento, Jéssica; Beckenkamp, Aline; Santana, Danielle Bertodo; Kipper, Franciele; Casali, Emerson André; Nejar Bruno, Alessandra; Paccez, Juliano Domiraci; Zerbini, Luiz Fernando; Wink, Marcia Rosângela; Lenz, Guido; Buffon, Andréia

    2014-01-01

    In cervical cancer, HPV infection and disruption of mechanisms involving cell growth, differentiation, and apoptosis are strictly linked with tumor progression and invasion. Tumor microenvironment is ATP and adenosine rich, suggesting a role for purinergic signaling in cancer cell growth and death. Here we investigate the effect of extracellular ATP on human cervical cancer cells. We find that extracellular ATP itself has a small cytotoxic effect, whereas adenosine formed from ATP degradation by ectonucleotidases is the main factor responsible for apoptosis induction. The level of P2×7 receptor seemed to define the main cytotoxic mechanism triggered by ATP, since ATP itself eliminated a small subpopulation of cells that express high P2×7 levels, probably through its activation. Corroborating these data, blockage or knockdown of P2×7 only slightly reduced ATP cytotoxicity. On the other hand, cell viability was almost totally recovered with dipyridamole, an adenosine transporter inhibitor. Moreover, ATP-induced apoptosis and signaling—p53 increase, AMPK activation, and PARP cleavage—as well as autophagy induction were also inhibited by dipyridamole. In addition, inhibition of adenosine conversion into AMP also blocked cell death, indicating that metabolization of intracellular adenosine originating from extracellular ATP is responsible for the main effects of the latter in human cervical cancer cells. PMID:25103241

  8. The adenosine a2a receptor inhibits matrix-induced inflammation in a novel fashion.

    PubMed

    Scheibner, Kara A; Boodoo, Sada; Collins, Samuel; Black, Katharine E; Chan-Li, Yee; Zarek, Paul; Powell, Jonathan D; Horton, Maureen R

    2009-03-01

    Endogenous mediators within the inflammatory milieu play a critical role in directing the scope, duration, and resolution of inflammation. High-molecular-weight extracellular matrix hyaluronan (HA) helps to maintain homeostasis. During inflammation, hyaluronan is broken down into fragments that induce chemokines and cytokines, thereby augmenting the inflammatory response. Tissue-derived adenosine, released during inflammation, inhibits inflammation via the anti-inflammatory A2 adenosine receptor (A2aR). We demonstrate that adenosine modulates HA-induced gene expression via the A2aR. A2aR stimulation inhibits HA fragment-induced pro-fibrotic genes TNF-alpha, keratinocyte chemoattractant (KC), macrophage inflammatory protein (MIP)-2, and MIP-1alpha while simultaneously synergizing with hyaluronan fragments to up-regulate the TH1 cytokine IL-12. Interestingly, A2aR stimulation mediates these affects via the novel cAMP-activated guanine nucleotide exchange factor EPAC. In addition, A2aR-null mice are more susceptible to bleomycin-induced lung injury, consistent with a role for endogenous adenosine in inhibiting the inflammation that may lead to fibrosis. Indeed, the bleomycin treated A2aR-null mice demonstrate increased lung inflammation, HA accumulation, and histologic damage. Overall, our data elucidate the opposing roles of tissue-derived HA fragments and adenosine in regulating noninfectious lung inflammation and support the pursuit of A2aR agonists as a means of pharmacologically inhibiting inflammation that may lead to fibrosis. PMID:18703794

  9. Squalenoyl adenosine nanoparticles provide neuroprotection after stroke and spinal cord injury

    NASA Astrophysics Data System (ADS)

    Gaudin, Alice; Yemisci, Müge; Eroglu, Hakan; Lepetre-Mouelhi, Sinda; Turkoglu, Omer Faruk; Dönmez-Demir, Buket; Caban, Seçil; Sargon, Mustafa Fevzi; Garcia-Argote, Sébastien; Pieters, Grégory; Loreau, Olivier; Rousseau, Bernard; Tagit, Oya; Hildebrandt, Niko; Le Dantec, Yannick; Mougin, Julie; Valetti, Sabrina; Chacun, Hélène; Nicolas, Valérie; Desmaële, Didier; Andrieux, Karine; Capan, Yilmaz; Dalkara, Turgay; Couvreur, Patrick

    2014-12-01

    There is an urgent need to develop new therapeutic approaches for the treatment of severe neurological trauma, such as stroke and spinal cord injuries. However, many drugs with potential neuropharmacological activity, such as adenosine, are inefficient upon systemic administration because of their fast metabolization and rapid clearance from the bloodstream. Here, we show that conjugation of adenosine to the lipid squalene and the subsequent formation of nanoassemblies allows prolonged circulation of this nucleoside, providing neuroprotection in mouse stroke and rat spinal cord injury models. The animals receiving systemic administration of squalenoyl adenosine nanoassemblies showed a significant improvement of their neurologic deficit score in the case of cerebral ischaemia, and an early motor recovery of the hindlimbs in the case of spinal cord injury. Moreover, in vitro and in vivo studies demonstrated that the nanoassemblies were able to extend adenosine circulation and its interaction with the neurovascular unit. This Article shows, for the first time, that a hydrophilic and rapidly metabolized molecule such as adenosine may become pharmacologically efficient owing to a single conjugation with the lipid squalene.

  10. Squalenoyl adenosine nanoparticles provide neuroprotection after stroke and spinal cord injury.

    PubMed

    Gaudin, Alice; Yemisci, Müge; Eroglu, Hakan; Lepetre-Mouelhi, Sinda; Turkoglu, Omer Faruk; Dönmez-Demir, Buket; Caban, Seçil; Sargon, Mustafa Fevzi; Garcia-Argote, Sébastien; Pieters, Grégory; Loreau, Olivier; Rousseau, Bernard; Tagit, Oya; Hildebrandt, Niko; Le Dantec, Yannick; Mougin, Julie; Valetti, Sabrina; Chacun, Hélène; Nicolas, Valérie; Desmaële, Didier; Andrieux, Karine; Capan, Yilmaz; Dalkara, Turgay; Couvreur, Patrick

    2014-11-24

    There is an urgent need to develop new therapeutic approaches for the treatment of severe neurological trauma, such as stroke and spinal cord injuries. However, many drugs with potential neuropharmacological activity, such as adenosine, are inefficient upon systemic administration because of their fast metabolization and rapid clearance from the bloodstream. Here, we show that conjugation of adenosine to the lipid squalene and the subsequent formation of nanoassemblies allows prolonged circulation of this nucleoside, providing neuroprotection in mouse stroke and rat spinal cord injury models. The animals receiving systemic administration of squalenoyl adenosine nanoassemblies showed a significant improvement of their neurologic deficit score in the case of cerebral ischaemia, and an early motor recovery of the hindlimbs in the case of spinal cord injury. Moreover, in vitro and in vivo studies demonstrated that the nanoassemblies were able to extend adenosine circulation and its interaction with the neurovascular unit. This Article shows, for the first time, that a hydrophilic and rapidly metabolized molecule such as adenosine may become pharmacologically efficient owing to a single conjugation with the lipid squalene. PMID:25420034

  11. WS0701: a novel sedative-hypnotic agent acting on the adenosine system.

    PubMed

    Bai, Xiao-Yu; Zhang, Xue-Qiong; Zhang, Yong-He; Wu, Song; Hao, Ling-Hua; Liu, Rui; Huang, Zhong-Lin; Zhang, Wei-Ku; Sun, Zong-Miao; Du, Guan-Hua

    2014-10-01

    To characterize the sedative and hypnotic profile of the novel adenosine derivative ((3S,4R,5R)-3,4-dihydroxy-5-(6-((4-hydroxy-3-methoxybenzyl)amino)-9H-purin-9-yl)tetrahydrofuran-2-yl) methyl diaconate (WS0701), we performed a variety of behavioural tests and investigated the influence of WS0701 on various sleep stages. In mice, WS0701 significantly increased the number of entries and time spent in open arms in the elevated plus maze test, indicating an anxiolytic effect. WS0701 decreased locomotor activity counts and head dips in the hole-board test and enhanced sodium pentobarbital-induced hypnosis. However, WS0701 did not induce the loss of the righting reflex or amnesic effects in behavioural models. In rats, WS0701 exerted a sedative effect and markedly prolonged the time spent in non-rapid-eye-movement sleep, especially slow-wave sleep, but reduced the time spent in rapid-eye-movement sleep (REMS). Pretreatment with the selective adenosine A2a receptor antagonist SCH58261 attenuated the sedative and hypnotic effects of WS0701. WS0701 did not protect mice against picrotoxin-induced seizures, but inhibited adenosine deaminase activity and increased adenosine levels in the frontal cortex and hypothalamus of mice. In conclusion, WS0701 shows anxiolytic, sedative as well as sleep stage alterative effects, which may be related to the adenosine system. PMID:25171078

  12. Targeting Na(+) /K(+) -translocating adenosine triphosphatase in cancer treatment.

    PubMed

    Durlacher, Cameron T; Chow, Kevin; Chen, Xiao-Wu; He, Zhi-Xu; Zhang, Xueji; Yang, Tianxin; Zhou, Shu-Feng

    2015-05-01

    The Na(+) /K(+) -translocating adenosine triphosphatase (ATPase) transports sodium and potassium across the plasma membrane and represents a potential target in cancer chemotherapy. Na(+) /K(+) -ATPase belongs to the P-type ATPase family (also known as E1-E2 ATPase), which is involved in transporting certain ions, metals, and lipids across the plasma membrane of mammalian cells. In humans, the Na(+) /K(+) -ATPase is a binary complex of an ?-subunit that has four isoforms (?1 -?4 ) and a ?-subunit that has three isoforms (?1 -?3 ). This review aims to update our knowledge on the role of Na(+) /K(+) -ATPase in cancer development and metastasis, as well as on how Na(+) /K(+) -ATPase inhibitors kill tumour cells. The Na(+) /K(+) -ATPase has been found to be associated with cancer initiation, growth, development, and metastasis. Cardiac glycosides have exhibited anticancer effects in cell-based and mouse studies via inhibition of the Na(+) /K(+) -ATPase and other mechanisms. Na(+) /K(+) -ATPase inhibitors may kill cancer cells via induction of apoptosis and autophagy, radical oxygen species production, and cell cycle arrest. They also modulate multiple signalling pathways that regulate cancer cell survival and death, which contributes to their antiproliferative activities in cancer cells. The clinical evidence supporting the use of Na(+) /K(+) -ATPase inhibitors as anticancer drugs is weak. Several phase I and phase II clinical trials with digoxin, Anvirzel, and huachansu (an intravenous formulated extract of the venom of the wild toad), either alone or more often in combination with other anticancer agents, have shown acceptable safety profiles but limited efficacy in cancer patients. Well-designed randomized clinical trials with reasonable sample sizes are certainly warranted to confirm the efficacy and safety of cardiac glycosides for the treatment of cancer. PMID:25739707

  13. Crystal structure of adenosine 5'-phosphosulfate kinase from Penicillium chrysogenum.

    PubMed

    MacRae, I J; Segel, I H; Fisher, A J

    2000-02-22

    Adenosine 5'-phosphosulfate (APS) kinase catalyzes the second reaction in the two-step conversion of inorganic sulfate to 3'-phosphoadenosine 5'-phosphosulfate (PAPS). This report presents the 2.0 A resolution crystal structure of ligand-free APS kinase from the filamentous fungus, Penicillium chrysogenum. The enzyme crystallized as a homodimer with each subunit folded into a classic kinase motif consisting of a twisted, parallel beta-sheet sandwiched between two alpha-helical bundles. The Walker A motif, (32)GLSASGKS(39), formed the predicted P-loop structure. Superposition of the APS kinase active site region onto several other P-loop-containing proteins revealed that the conserved aspartate residue that usually interacts with the Mg(2+) coordination sphere of MgATP is absent in APS kinase. However, upon MgATP binding, a different aspartate, Asp 61, could shift and bind to the Mg(2+). The sequence (156)KAREGVIKEFT(166), which has been suggested to be a (P)APS motif, is located in a highly protease-susceptible loop that is disordered in both subunits of the free enzyme. MgATP or MgADP protects against proteolysis; APS alone has no effect but augments the protection provided by MgADP. The results suggest that the loop lacks a fixed structure until MgATP or MgADP is bound. The subsequent conformational change together with the potential change promoted by the interaction of MgATP with Asp 61 may define the APS binding site. This model is consistent with the obligatory ordered substrate binding sequence (MgATP or MgADP before APS) as established from steady state kinetics and equilibrium binding studies. PMID:10677210

  14. Quantitative analysis of adenosine using liquid chromatography\\/atmospheric pressure chemical ionization-tandem mass spectrometry (LC\\/APCI-MS\\/MS)

    Microsoft Academic Search

    Annelies Van Dycke; Alain Verstraete; Kristof Pil; Robrecht Raedt; Kristl Vonck; Detlev Boison; Paul Boon

    2010-01-01

    Adenosine-secreting cellular brain implants constitute a promising therapeutic approach for the treatment of epilepsy. To engineer neural stem cells for therapeutic adenosine delivery, a reliable and fast analytical method is necessary to quantify cell-based adenosine release. Here we describe the development, optimization and validation of adenosine measurement using liquid chromatography–atmospheric pressure chemical ionization-tandem mass spectrometry (LC–APCI-MS\\/MS). LC–MS\\/MS in positive ion

  15. Adenosine and purine nucleosides prevent the disruption of mitochondrial transmembrane potential by peroxynitrite in rat primary astrocytes.

    PubMed

    Choi, Ji Woong; Yoo, Byung-Kwon; Ryu, Mi Kyoung; Choi, Min Sik; Park, Gyu Hwan; Ko, Kwang Ho

    2005-07-01

    Previously, we have shown that astrocytes deprived of glucose became highly vulnerable to peroxynitrite, and adenosine and its metabolites attenuated the gliotoxicity via the preservation of cellular ATP level. Here, we found that adenosine and related metabolites prevented the disruption of mitochondrial transmembrane potential (MTP) in glucose-deprived rat primary astrocytes exposed to 3-morpholinosydnonimine (SIN-1), a peroxynitrite releasing agent. Exposure to glucose deprivation and SIN-1 (2 h) significantly disrupted MTP in astrocytes, and adenosine prevented it in dose-dependent manner with an EC50 of 5.08 microM. Adenosine also partially prevented the cell death by myxothiazol, a well-known inhibitor of mitochondrial respiration. Blockade of adenosine deamination or intracellular transport with erythro-9-(-hydroxy-3-nonyl)adenosine (EHNA) or S-(4-nitrobenzyl)-6-thioinosine (NBTI), respectively, completely reversed the protective effect of adenosine. Other purine nucleos(t)ides including inosine, guanosine, ATP, ADP, AMP, ITP, and GTP also showed similar protective effects. This study indicates that adenosine and related purine nucleos(t)ides may protect astrocytes from peroxynitrite-induced mitochondrial dysfunction. PMID:16114496

  16. Interactions between adenosine, angiotensin II and nitric oxide on the afferent arteriole influence sensitivity of the tubuloglomerular feedback

    PubMed Central

    Persson, A. E. G.; Lai, En Yin; Gao, Xiang; Carlström, Mattias; Patzak, Andreas

    2013-01-01

    Adenosine, via activation of A1 receptors on the afferent arteriole (AA), mediates the tubuloglomerular feedback (TGF) mechanism. Angiotensin II and nitric oxide (NO) can modulate the sensitivity of the TGF mechanism. However, the interaction among these substances in regulating the TGF resetting phenomenon has been debated. Studies in isolated perfused AA have shown a biphasic response to accumulating doses of adenosine alone. In the nanomolar range adenosine has a weak contractile effect (7%), whereas vasodilatation is observed at high concentrations. However, a synergistic interaction between the contractile response by adenosine and that of angiotensin II has been demonstrated. Adenosine in low concentrations strongly enhances the response to angiotensin II. At the same time, angiotensin II in physiological concentrations increases significantly the contractile response to adenosine. Moreover, addition of a NO donor (spermine NONOate) to increase NO bioavailability abolished the contractile response from combined application of angiotensin II and adenosine. These mutual modulating effects of adenosine and angiotensin II, and the effect of NO on the response of AA can contribute to the resetting of the TGF sensitivity. PMID:23882224

  17. The Metal Ion-Dependent Adhesion Site Motif of the Enterococcus faecalis EbpA Pilin Mediates Pilus Function in Catheter-Associated Urinary Tract Infection

    PubMed Central

    Nielsen, Hailyn V.; Guiton, Pascale S.; Kline, Kimberly A.; Port, Gary C.; Pinkner, Jerome S.; Neiers, Fabrice; Normark, Staffan; Henriques-Normark, Birgitta; Caparon, Michael G.; Hultgren, Scott J.

    2012-01-01

    ABSTRACT Though the bacterial opportunist Enterococcus faecalis causes a myriad of hospital-acquired infections (HAIs), including catheter-associated urinary tract infections (CAUTIs), little is known about the virulence mechanisms that it employs. However, the endocarditis- and biofilm-associated pilus (Ebp), a member of the sortase-assembled pilus family, was shown to play a role in a mouse model of E. faecalis ascending UTI. The Ebp pilus comprises the major EbpC shaft subunit and the EbpA and EbpB minor subunits. We investigated the biogenesis and function of Ebp pili in an experimental model of CAUTI using a panel of chromosomal pilin deletion mutants. A nonpiliated pilus knockout mutant (EbpABC? strain) was severely attenuated compared to its isogenic parent OG1RF in experimental CAUTI. In contrast, a nonpiliated ebpC deletion mutant (EbpC? strain) behaved similarly to OG1RF in vivo because it expressed EbpA and EbpB. Deletion of the minor pilin gene ebpA or ebpB perturbed pilus biogenesis and led to defects in experimental CAUTI. We discovered that the function of Ebp pili in vivo depended on a predicted metal ion-dependent adhesion site (MIDAS) motif in EbpA’s von Willebrand factor A domain, a common protein domain among the tip subunits of sortase-assembled pili. Thus, this study identified the Ebp pilus as a virulence factor in E. faecalis CAUTI and also defined the molecular basis of this function, critical knowledge for the rational development of targeted therapeutics. PMID:22829678

  18. Autoradiographic localization of adenosine uptake sites in rat brain using (/sup 3/H)nitrobenzylthioinosine

    SciTech Connect

    Bisserbe, J.C.; Patel, J.; Marangos, P.J.

    1985-02-01

    The adenosine uptake site has been localized in rat brain by an in vitro light microscopic autoradiographic method, using (/sup 3/H)nitrobenzylthioinosine ((/sup 3/H)NBI) as the probe. The binding characteristics of (/sup 3/H)NBI on slide-mounted sections are comparable to those seen in studies performed on brain homogenates. A very high density of uptake sites occurs in the nucleus tractus solitarius, in the superficial layer of the superior colliculus, in several thalamic nuclei, and also in geniculate body nuclei. A high density of sites are also observed in the nucleus accumbens, the caudate putamen, the dorsal tegmentum area, the substantia nigra, and the central gray. The localization of the adenosine uptake site in brain may provide information on the functional activity of the site and suggests the involvement of the adenosine system in the central regulation of cardiovascular function.

  19. Adenosine-containing molecules amplify glucose signaling and enhance txnip expression.

    PubMed

    Yu, Fa-Xing; Goh, Shuang-Ru; Dai, Ru-Ping; Luo, Yan

    2009-06-01

    Eukaryotic cells sense extracellular glucose concentrations via diverse mechanisms to regulate the expression of genes involved in metabolic control. One such example is the tight correlation between the expression of thioredoxin-interacting protein (Txnip) and extracellular glucose levels. In this report, we show that the transcription of the Txnip gene is induced by adenosine-containing molecules, of which an intact adenosine moiety is necessary and sufficient. Txnip promoter contains a carbohydrate response element, which mediates the induction of Txnip expression by these molecules in a glucose-dependent manner. Max-like protein X and MondoA are transcription factors previously shown to stimulate glucose-dependent Txnip expression and are shown here to convey stimulatory signals from extracellular adenosine-containing molecules to the Txnip promoter. The regulatory role of these molecules may be exerted via amplifying glucose signaling. Hence, this revelation may pave the way for interventions aimed toward metabolic disorders resulting from abnormal glucose homeostasis. PMID:19246513

  20. Astrocytes Control Food Intake by Inhibiting AGRP Neuron Activity via Adenosine A1 Receptors.

    PubMed

    Yang, Liang; Qi, Yong; Yang, Yunlei

    2015-05-01

    It is well recognized that feeding behavior in mammals is orchestrated by neurons within the medial basal hypothalamus. However, it remains unclear whether food intake is also under the control of glial cells. Here, we combine chemical genetics, cell-type-specific electrophysiology, pharmacology, and feeding assays to show that stimulation of astrocytes within the medial basal hypothalamus reduces both basal- and ghrelin-evoked food intake. This occurs by a mechanism of adenosine-mediated inactivation of the orexigenic agouti-related peptide (AGRP) neurons in the hypothalamic arcuate nucleus (ARC) via adenosine A1 receptors. Our data suggest that glial cells participate in regulating food intake by modulating extracellular levels of adenosine. These findings reveal the existence of a glial relay circuit that controls feeding behavior, one that might serve as a target for therapeutic intervention in the treatment of appetite disorders. PMID:25921535

  1. Computational Elucidation of Structural Basis for Ligand Binding with Leishmania donovani Adenosine Kinase

    PubMed Central

    Kar, Rajiv K.; Ansari, Md. Yousuf; Suryadevara, Priyanka; Sahoo, Bikash R.; Sahoo, Ganesh C.; Dikhit, Manas R.; Das, Pradeep

    2013-01-01

    Enzyme adenosine kinase is responsible for phosphorylation of adenosine to AMP and is crucial for parasites which are purine auxotrophs. The present study describes development of robust homology model of Leishmania donovani adenosine kinase to forecast interaction phenomenon with inhibitory molecules using structure-based drug designing strategy. Docking calculation using reported organic small molecules and natural products revealed key active site residues such as Arg131 and Asp16 for ligand binding, which is consistent with previous studies. Molecular dynamics simulation of ligand protein complex revealed the importance of hydrogen bonding with active site residues and solvent molecules, which may be crucial for successful development of drug candidates. Precise role of Phe168 residue in the active site was elucidated in this report that provided stability to ligand-protein complex via aromatic-? contacts. Overall, the present study is believed to provide valuable information to design a new compound with improved activity for antileishmanial therapeutics development. PMID:23984386

  2. Computational study of the molecular mechanisms of caffeine action: Caffeine complexes with adenosine receptors

    NASA Astrophysics Data System (ADS)

    Poltev, V. I.; Rodríguez, E.; Grokhlina, T. I.; Deriabina, A.; Gonzalez, E.

    To understand the molecular basis of the principal biological action of the caffeine (CAF), the molecular mechanics calculations of possible complexes between CAF and the fragments of human A1 adenosine receptor were performed. The fragments were selected after considerations of the CAF molecular structure and its possible interactions, as well as after an analysis of the extensive bibliography on the structure, biological role, site-directed mutagenesis, and the modeling of the adenosine receptors. The minimum energy configurations of these complexes were obtained using two different computer programs with different force fields. The most favorable configurations correspond to the formation of two hydrogen bonds between the CAF molecule and hydrophilic amino acid residues of the fragments of transmembrane domains of the receptor. These configurations are supposed to contribute to CAF blocking of the adenosine receptors. They will be used later for the construction of model CAF complexes with two transmembrane domains simultaneously.

  3. The critical role of adenosine A 2A receptors in downregulation of inflammation and immunity in the pathogenesis of infectious diseases

    Microsoft Academic Search

    Manfred Thiel; Charles C Caldwell; Michail V Sitkovsky

    2003-01-01

    Adenosine can be described as a retaliatory metabolite, the production and release of which is usually enhanced under adverse environmental conditions. Binding via specific receptors, adenosine activates endogenous protective mechanisms aiming at the restoration of tissue homeostasis. While adenosinergic downregulation of tissue damage is beneficial in acute inflammation, chronic suppression of the immune system by adenosine may account for immunoparalysis

  4. Uneven distribution of nucleoside transporters and intracellular enzymatic degradation prevent transport of intact [14C] adenosine across the sheep choroid plexus epithelium as a monolayer in primary culture

    Microsoft Academic Search

    Zoran B Redzic; Aleksandra J Isakovic; Sonja T Misirlic Dencic; Dusan Popadic; Malcolm B Segal

    2006-01-01

    BACKGROUND: Efflux transport of adenosine across the choroid plexus (CP) epithelium might contribute to the homeostasis of this neuromodulator in the extracellular fluids of the brain. The aim of this study was to explore adenosine transport across sheep CP epithelial cell monolayers in primary culture. METHODS: To explore transport of adenosine across the CP epithelium, we have developed a method

  5. Interleukin6 Enhances Expression of Adenosine A1 Receptor mRNA and Signaling in Cultured Rat Cortical Astrocytes and Brain Slices

    Microsoft Academic Search

    Knut Biber; Beate Lubrich; Bernd L Fiebich; Hendrikus WGM Boddeke; Dietrich van Calker

    2001-01-01

    The inhibitory neuromodulator adenosine is released in the brain in high concentrations under conditions of exaggerated neuronal activity such as ischemia and seizures, or electroconvulsive treatment. By inhibiting neural overactivity, adenosine counteracts seizure activity and promotes neuronal survival. Since stimulation of adenosine A2b receptors on astrocytes induces increased synthesis and release of interleukin-6, which also exerts neuroprotective effects, we hypothesized

  6. Alcohol Worsens Acute Lung Injury by Inhibiting Alveolar Sodium Transport through the Adenosine A1 Receptor

    PubMed Central

    Urich, Daniela; Soberanes, Saul; Manghi, Tomas S.; Chiarella, Sergio E.; Chandel, Navdeep S.; Budinger, G. R. Scott; Mutlu, Gökhan M.

    2012-01-01

    Objective Alcohol intake increases the risk of acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) and is associated with poor outcomes in patients who develop these syndromes. No specific therapies are currently available to treat or decrease the risk of ARDS in patients with alcoholism. We have recently shown increased levels of lung adenosine inhibit alveolar fluid clearance, an important predictor of outcome in patients with ARDS. We hypothesized that alcohol might worsen lung injury by increasing lung adenosine levels, resulting in impaired active Na+ transport in the lung. Methods We treated wild-type mice with alcohol administered i.p. to achieve blood alcohol levels associated with moderate to severe intoxication and measured the rate of alveolar fluid clearance and Na,K-ATPase expression in peripheral lung tissue and assessed the effect of alcohol on survival during exposure to hyperoxia. We used primary rat alveolar type II cells to investigate the mechanisms by which alcohol regulates alveolar Na+ transport. Results Exposure to alcohol reduced alveolar fluid clearance, downregulated Na,K-ATPase in the lung tissue and worsened hyperoxia-induced lung injury. Alcohol caused an increase in BAL fluid adenosine levels. A similar increase in lung adenosine levels was observed after exposure to hyperoxia. In primary rat alveolar type II cells alcohol and adenosine decreased the abundance of the Na,K-ATPase at the basolateral membrane via a mechanism that required activation of the AMPK. Conclusions Alcohol decreases alveolar fluid clearance and impairs survival from acute lung injury. Alcohol induced increases in lung adenosine levels may be responsible for reduction in alveolar fluid clearance and associated worsening of lung injury. PMID:22272351

  7. Effect of adenosine system in the action of oseltamivir on behavior in mice.

    PubMed

    Uchiyama, Hidemori; Hiromura, Makoto; Shiratani, Tomonori; Kuroki, Hiroaki; Honda, Sinichiro; Kosako, Kazuhiro; Soeda, Shinji; Inoue, Kazuhide; Toda, Akihisa

    2015-07-10

    Abnormal behaviors and death associated with the use of oseltamivir (Tamiflu(®)) have emerged as a major issue in influenza patients. We have previously reported that the mechanisms underlying the effects of caffeine, a non-selective adenosine A1/A2 receptor antagonist, combined with oseltamivir. Oseltamivir is rapidly hydrolyzed to its active form (oseltamivir carboxylate, OCB). In this study, we investigated the effects of an adenosine system and OCB on the action of oseltamivir on mice behavior. Oseltamivir for 1 day (150mg/kg, intraperitoneally (i.p.)) alone did not affect ambulation at 2h post-injection. However, caffeine (10mg/kg, i.p.) in combination with oseltamivir for 1 day increased ambulation. Moreover, caffeine (30mg/kg, i.p.) in combination with oseltamivir for 3 days increased ambulation, but caffeine (10mg/kg, i.p.) in combination with oseltamivir for 3 days did not increase. These enhancements were inhibited by an adenosine A2 receptor agonist, CGS21680 (0.2mg/kg, subcutaneously (s.c.)). Furthermore, an adenosine A2 receptor antagonist, SCH58261 (1 and 3mg/kg, i.p.) in combination with oseltamivir for 1 day increased ambulation. Moreover, SCH58261 (3mg/kg, i.p.) in combination with oseltamivir for 3 days increased ambulation, but SCH58261 (1 mg/kg, i.p.) in combination with oseltamivir for 3 days did not. Conversely, in phenobarbital (PB)-treated mice, caffeine (3mg/kg, i.p.) in combination with oseltamivir for 1 day increased ambulation. Moreover, OCB for 1 day (0.3 ?g/mouse intracerebroventricular (i.c.v.)) alone increased ambulation. These findings suggest that the actions of oseltamivir may involve the adenosine systems and its metabolism. Our findings suggest an interaction between the central blockade of adenosine A2 receptors by caffeine and OCB-induced behavioral changes. PMID:25980995

  8. Structure-activity relationship for the binding of nucleoside ligands to adenosine kinase from Toxoplasma gondii.

    PubMed

    Iltzsch, M H; Uber, S S; Tankersley, K O; el Kouni, M H

    1995-05-17

    One hundred and twenty-eight purine nucleoside analogs were evaluated as ligands of Toxoplasma gondii adenosine kinase (EC 2.7.1.20) by examining their ability to inhibit this enzyme in vitro. Inhibition was quantified by determining apparent Ki (appKi) values for those compounds that inhibited this enzyme by greater than 10% at a concentration of 1 mM. Two compounds, N6-(p-methoxybenzoyl)adenosine and 7-iodo-7-deazaadenosine (iodotubercidin), were found to bind to the enzyme (appKi = 3.9 and 1.6 microM, respectively) better than adenosine. On the basis of these data, a structure-activity relationship for the binding of ligands to T. gondii adenosine kinase was formulated using adenosine as a reference compound. It was concluded that the following structural features of purine nucleoside analogs are required or strongly preferred for binding: (1) "pyridine-type" endocyclic nitrogens at the 1- and 3-positions; (2) an exocyclic hydrogen at the 2-position; (3) 6-position exocyclic substituents in the lactim tautomeric form; (4) a "pyridine-type" endocyclic nitrogen at the 7-position or hydrophobic exocyclic substituents attached to an endocyclic carbon at the 7-position; (5) an endocyclic methine or "pyridine-type" nitrogen at the 8-position; (6) an endocyclic nitrogen at the 9-position; (7) a pentose or "pentose-like" (e.g. hydroxylated cyclopentene) moiety attached to the 9-position nitrogen; (8) hydroxyl groups at the 2'- and 3'-positions in a ribose configuration; (9) a hydroxymethyl or methyl (i.e. 5'-deoxy) group at the 5'-position; (10) a beta-D-nucleoside configuration; and (11) an anti conformation around the N-glycosidic bond. In addition, there appears to be a "pocket" in the catalytic site of T. gondii adenosine kinase, adjacent to the 6-position of adenosine, that can accommodate large (preferably unsaturated or aromatic) substituents (e.g. phenyl). These findings provide the basis for the rational design of additional ligands of T. gondii adenosine kinase. PMID:7763293

  9. Mechanism of adenosine-induced airways obstruction in allergic guinea pigs.

    PubMed

    Keir, Sandra; Boswell-Smith, Victoria; Spina, Domenico; Page, Clive

    2006-04-01

    Inhaled adenosine induces airway obstruction in asthmatic but not healthy subjects, a phenomenon that is also observed in various animal species when they are immunised to a relevant antigen, but which does not occur in naïve animals. The purpose of this study was to investigate the mechanisms of airway responsiveness to adenosine receptor agonists in anaesthetised allergic guinea pigs. Inhaled adenosine 5'-monophosphate (AMP), the A1-selective adenosine receptor agonist N6-cyclopentyladenosine (CPA) and ovalbumin all caused airway obstruction in allergic guinea pigs, but not naïve animals, as assessed by changes in total lung resistance. In contrast, the A(2a)-selective (CGS 21680; 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxoamido adenosine) and A3-selective (IB-MECA; 1-deoxy-1-[6-[[3-iodophenyl)-methyl]amino]-9H-purin-9-yl]-N-methyl-beta-D-ribofuranuronamide) adenosine receptor agonists failed to elicit airway obstruction in passively sensitised guinea pigs. Airway obstruction induced by AMP or CPA was not inhibited by the H1 receptor antagonist, mepyramine (1 mg kg(-1)) in passively sensitised guinea-pigs. In contrast, airway obstruction to ovalbumin was significantly inhibited by this antagonist. Airway obstruction induced by AMP and CPA was significantly inhibited in sensitised animals chronically treated with capsaicin. In contrast, airway obstruction to ovalbumin was not inhibited by this treatment. Airway obstruction induced by AMP, CPA and ovalbumin was significantly inhibited following bilateral vagotomy or pharmacological treatment with atropine (2 mg kg(-1)). Airway obstruction to CPA was inhibited by the adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX: 0.1-1 mg kg(-1)). In contrast, airway obstruction to ovalbumin was not inhibited by this treatment. These observations provide evidence indicating that AMP and CPA may induce airway obstruction in sensitised guinea pigs by a mechanism unrelated to histamine release from mast cells, but is mediated via an adenosine A1-receptor-dependent mechanism. The inhibition of AMP- and CPA-induced airway obstruction by atropine, capsaicin and bilateral vagotomy suggests a neuronal-dependent mechanism with the particular involvement of capsaicin-sensitive nerves. PMID:16432507

  10. Interaction of adenosine and naloxone on regional cerebral blood flow in morphine-dependent rats

    Microsoft Academic Search

    Mahdi Zahedi Khorasani; Sohrab Hajizadeh; Yaghoub Fathollahi; Saeed Semnanian

    2006-01-01

    The present research aimed at investigating the opioid–adenosine interaction on regional cerebral blood flow (rCBF). Therefore rCBF in the sensory cortex of morphine-naive and -dependent rats was measured using the laser-Doppler flowmetry technique. The results showed that adenosine (10?5, 10?4, 10?3 M) significantly increased rCBF in morphine-dependent rats (MDR) (P < 0.01). This effect was inhibited by theophylline (5 × 10?5 M). Also systemic naloxone (0.5,

  11. Adenosine(5') oligophospho-(5') guanosines and guanosine(5') oligophospho-(5') guanosines in human platelets.

    PubMed Central

    Schlüter, H; Grobeta, I; Bachmann, J; Kaufmann, R; van der Giet, M; Tepel, M; Nofer, J R; Assmann, G; Karas, M; Jankowski, J; Zidek, W

    1998-01-01

    We isolated and identified nucleoside(5') oligophospho-(5') nucleosides containing adenosine and guanosine (ApnG; n = 3-6) as well as diguanosine polyphosphates (GpnG; n = 3-6) in human platelets. For identification, UV spectrometry, matrix-assisted laser desorption/ionization, postsource decay matrix-assisted laser desorption/ionization mass spectrometry, and enzymatic cleavage experiments were used. The adenosine(5') oligophospho-(5') guanosines act as vasoconstrictors and growth factors. The diguanosine polyphosphates are potent modulators of growth in vascular smooth muscle cells, but do not affect vascular tone. PMID:9449703

  12. Analgesic and anti-inflammatory effects of A-286501, a novel orally active adenosine kinase inhibitor

    Microsoft Academic Search

    Michael F. Jarvis; Haixia Yu; Steve McGaraughty; Carol T. Wismer; Joe Mikusa; Chang Zhu; Katharine Chu; Kathy Kohlhaas; Marlon Cowart; Chih-Hung Lee; Andrew O. Stewart; Bryan F. Cox; James Polakowski; Elizabeth A. Kowaluk

    2002-01-01

    Adenosine (ADO) is an inhibitory neuromodulator that can increase nociceptive thresholds in response to noxious stimulation. Inhibition of the ADO-metabolizing enzyme, adenosine kinase (AK) increases extracellular ADO concentrations at sites of tissue trauma and AK inhibitors may have therapeutic potential as analgesic and anti-inflammatory agents. N7-((1?R,2?S,3?R,4?S)-2?,3?-dihydroxy-4?-amino-cyclopentyl)-4-amino-5-bromo-pyrrolo[2,3-a]pyrimidine (A-286501) is a novel and potent (IC50=0.47nM) carbocyclic nucleoside AK inhibitor that has no

  13. Adenosine Augments IL-10 Production by Macrophages through an A2B Receptor-Mediated Posttranscriptional Mechanism1

    PubMed Central

    Németh, Zoltán H.; Lutz, Carol S.; Csóka, Balázs; Deitch, Edwin A.; Leibovich, S. Joseph; Gause, William C.; Tone, Masahide; Pacher, Pál; Vizi, E. Sylvester; Haskó, György

    2007-01-01

    Adenosine receptor ligands have anti-inflammatory effects and modulate immune responses by up-regulating IL-10 production by immunostimulated macrophages. The adenosine receptor family comprises G protein-coupled heptahelical transmembrane receptors classified into four types: A1, A2A, A2B, and A3. Our understanding of the signaling mechanisms leading to enhanced IL-10 production following adenosine receptor occupancy on macrophages is limited. In this study, we demonstrate that adenosine receptor occupancy increases IL-10 production by LPS-stimulated macrophages without affecting IL-10 promoter activity and IL-10 mRNA levels, indicating a posttranscriptional mechanism. Transfection experiments with reporter constructs containing sequences corresponding to the AU-rich 3?-untranslated region (UTR) of IL-10 mRNA confirmed that adenosine receptor activation acts by relieving the translational repressive effect of the IL-10 3?-UTR. By contrast, adenosine receptor activation failed to liberate the translational arrest conferred by the 3?-UTR of TNF-? mRNA. The IL-10 3?-UTR formed specific complexes with proteins present in cytoplasmic extracts of RAW 264.7 cells. Adenosine enhanced binding of proteins to a region of the IL-10 3?-UTR containing the GUAUUUAUU nonamer. The stimulatory effect of adenosine on IL-10 production was mediated through the A2B receptor, because the order of potency of selective agonists was 5?-N-ethylcarboxamidoadenosine (NECA) > N6-(3-iodobenzyl)-adenosine-5?-N-methyluronamide (IB-MECA) > 2-chloro-N6-cyclopentyladenosine (CCPA) = 2-p-(2-carboxyethyl)-phenethylamino-5?-N-ethyl-carboxamidoadenosine (CGS-21680). Also, the selective A2B antagonist, alloxazine, prevented the effect of adenosine. Collectively, these studies identify a novel pathway in which activation of a G protein-coupled receptor augments translation of an anti-inflammatory gene. PMID:16339566

  14. Low energy electron attachment to the adenosine site of DNA.

    PubMed

    Gu, Jiande; Wang, Jing; Leszczynski, Jerzy

    2011-12-15

    To evaluate the role of adenosine in low energy electron (LEE) induced DNA strand breaks, theoretical investigations of the LEE attachment induced C-O ? bonds and N-glycosidic bond breaking of 2'-deoxyadenosine-3',5'-diphosphate (3',5'-dAMP) were performed at the B3LYP/DZP++ level of theory. The results indicate that, although adenine-rich oligonucleotides are capable of capturing the near 0 eV electron to form the electronically stable radical anions in the gas phase, it is unlikely to undergo either C-O ? bond cleavage or the glycosidic processes due to the low electron detachment energy (VDE) of 3',5'-dADP(-) unit (0.26 eV). Instead, these radical anions should directly yield an electron detachment product in the gas phase. In the presence of polarizable surroundings, due to the large increase of the electron detachment energy (VDE increases to 1.59 eV), the adenine-centered radical anions could directly lead to strand breaks in the adenine-rich DNA single strands through either ? bond or N-glycosidic bond breaking. The values of activation energy for rupture of the C(5')-O(5') ? bond (22.5 kcal/mol), the N-glycosidic bond (20.2 kcal/mol), and the C(3')-O(3') ? bond (13.2 kcal/mol) indicate that C(3')-O(3') ? bond breaking should dominate. Moreover, along with the previous research, the predicted ratio of the activation energy barrier of the C(5')-O(5') ? bond breakage in 3',5'-dXDP(-) (X = G, A, T) partly explains the observation in the femtosecond time-resolved laser spectroscopic experiment that the C(5')-O(5') ? bond breaking only occurs in dGMP(-) and dTMP(-) not in dAMP(-). This study completes the series of LEE-induced DNA single strand breaking investigations for the four basic DNA units 3',5'-dXDP (X = G, A, T, C). The obtained results are vital for elucidating the experimental observations. Combined with the previous studies, the information revealed in this study is crucial for understanding the mechanisms of the interactions between the LEE and the DNA stands. PMID:22034990

  15. Adenosine Analogues as Selective Inhibitors of Glyceraldehyde-3-phosphate Dehydrogenase of Trypanosomatidae via Structure-Based Drug Design

    PubMed Central

    Bressi, Jerome C.; Verlinde, Christophe L. M. J.; Aronov, Alex M.; Shaw, My Le; Shin, Sam S.; Nguyen, Lisa N.; Suresh, Stephen; Buckner, Frederick S.; Van Voorhis, Wesley C.; Kuntz, Irwin D.; Hol, Wim G. J.; Gelb, Michael H.

    2010-01-01

    In our continuation of the structure-based design of anti-trypanosomatid drugs, parasite-selective adenosine analogues were identified as low micromolar inhibitors of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Crystal structures of Trypanosoma brucei, Trypanosoma cruzi, Leishmania mexicana, and human GAPDH’s provided details of how the adenosyl moiety of NAD+ interacts with the proteins, and this facilitated the understanding of the relative affinities of a series of adenosine analogues for the various GAPDH’s. From exploration of modifications of the naphthalenemethyl and benzamide substituents of a lead compound, N6-(1-naphthalenemethyl)-2?-deoxy-2?-(3-methoxybenzamido)adenosine (6e), N6-(substituted-naphthalenemethyl)-2?-deoxy-2?-(substituted-benzamido)adenosine analogues were investigated. N6-(1-Naphthalenemethyl)-2?-deoxy-2?-(3,5-dimethoxybenzamido)adenosine (6m), N6-[1-(3-hydroxy-naphthalene)methyl]-2?-deoxy-2?-(3,5-dimethoxybenzamido)adenosine (7m), N6-[1-(3-methoxy-naphthalene)methyl]-2?-deoxy-2?-(3,5-dimethoxybenzamido)adenosine (9m), N6-(2-naphthalene-methyl)-2?-deoxy-2?-(3-methoxybenzamido)adenosine (11e), and N6-(2-naphthalenemethyl)-2?-deoxy-2?-(3,5-dimethoxybenzamido)adenosine (11m) demonstrated a 2- to 3-fold improvement over 6e and a 7100- to 25000-fold improvement over the adenosine template. IC50’s of these compounds were in the range 2–12 ?M for T. brucei, T. cruzi, and L. mexicana GAPDH’s, and these compounds did not inhibit mammalian GAPDH when tested at their solubility limit. To explore more thoroughly the structure–activity relationships of this class of compounds, a library of 240 N6-(substituted)-2?-deoxy-2?-(amido)adenosine analogues was generated using parallel solution-phase synthesis with N6 and C2? substituents chosen on the basis of computational docking scores. This resulted in the identification of 40 additional compounds that inhibit parasite GAPDH’s in the low micromolar range. We also explored adenosine analogues containing 5?-amido substituents and found that 2?,5?-dideoxy-2?-(3,5-dimethoxy-benzamido)-5?-(diphenylacetamido)adenosine (49) displays an IC50 of 60–100 ?M against the three parasite GAPDH’s. PMID:11405646

  16. Determination of Aluminum, Calcium, and Magnesium in Fraser Fir ( Abies fraseri) Foliage from Five Native Sites by Atomic Absorption Spectrometry: The Effect of Elevation upon Nutritional Status

    Microsoft Academic Search

    Chad E. Lee; Jeremy M. Cox; Derek M. Foster; Holly L. Humphrey; Royce S. Woosley; David J. Butcher

    1997-01-01

    The Fraser fir (Abies fraseri) is a conifer native to high elevation sites in the southern Appalachians that has recently suffered severe mortality because of an exotic insect, the balsam woolly adelgid (BWA). The companion tree of the Fraser fir, the red spruce (Piceae rubens) has suffered relatively mild decline induced by acidic deposition, due to reduction of extractable calcium

  17. The mitochondrial transporter of ascorbic acid functions with high affinity in the presence of low millimolar concentrations of sodium and in the absence of calcium and magnesium.

    PubMed

    Fiorani, Mara; Azzolini, Catia; Cerioni, Liana; Scotti, Maddalena; Guidarelli, Andrea; Ciacci, Caterina; Cantoni, Orazio

    2015-06-01

    We recently reported that U937 cell mitochondria express a functional Na(+)-dependent ascorbic acid (AA) transporter recognised by anti-SVCT2 antibodies. The present study confirms and extends these observations by showing that this transporter is characterised by a Km and a pH-dependence comparable with that reported for the plasma membrane SVCT2. In isolated mitochondria, Na(+) increased AA transport rate in a cooperative manner, revealed by a sigmoid curve and a Hill coefficient of 2, as also observed in intact Raw 264.7 cells (uniquely expressing SVCT2). There was however a striking difference on the Na(+) concentrations necessary to reach saturation, i.e., 1 or 100mM for the mitochondrial and plasma membrane transporters, respectively. Furthermore the mitochondrial, unlike the plasma membrane, transporter was fully active also in the absence of added Ca(++) and/or Mg(++). Taken together, the results presented in this study indicate that the U937 cell mitochondrial transporter of AA, because of its very low requirement for Na(+) and independence for Ca(++) and Mg(++), displays kinetic characteristics surprisingly similar with those of the plasma membrane SVCT2. PMID:25786874

  18. Effect of calcium and magnesium on neurotoxicity and blood platinum concentrations in patients receiving mFOLFOX6 therapy: a prospective randomized study

    Microsoft Academic Search

    Keiichiro Ishibashi; Norimichi Okada; Tatsuya Miyazaki; Motohiko Sano; Hideyuki Ishida

    2010-01-01

    Background  Whether the administration of calcium (Ca) and magnesium (Mg) can reduce oxaliplatin-related neurotoxicity remains controversial.\\u000a In addition, little is known about the effects of Ca\\/Mg on the blood level of platinum or objective tumor progression.\\u000a \\u000a \\u000a \\u000a Patients and methods  Patients receiving modified FOLFOX6 for metastatic colorectal cancer were double-blinded and randomized to receive additional\\u000a treatment with Ca\\/Mg or placebo before and after

  19. Stimulation of rat liver glycogen synthesis by the adenosine kinase inhibitor 5-iodotubercidin.

    PubMed Central

    Flückiger-Isler, R E; Walter, P

    1993-01-01

    The adenosine kinase inhibitor 5-iodotubercidin (Itu) was found to have the following effects on glycogen metabolism in hepatocytes of fasted rats. (1) Itu strongly stimulated glycogen synthesis from different substrates (glucose, lactate plus pyruvate, dihydroxyacetone, glycerol and fructose). In cells incubated with these substrates, the well-known stimulating effect of amino acids and that of Itu was more than additive. (2) In parallel with the increase in glycogen deposition, there was an increase in synthase a and a decrease in phosphorylase a concentrations after administration of Itu. Synthase a was increased by Itu and amino acids in an additive manner, whereas the observed activation of phosphorylase after addition of amino acids was antagonized by Itu. (3) In contrast with amino acids, Itu increased neither the cell volume nor the aspartate and glutamate concentrations. (4) Itu enhanced the levels of cyclic AMP. The stimulation of glycogen deposition in the presence of Itu persisted when the cyclic AMP concentration was further increased by adenosine or 2-chloroadenosine. (5) Itu decreased the concentration of ATP, but its effects on glycogen synthesis, synthase a and phosphorylase a concentrations persisted when the ATP catabolism was prevented by adenosine. (6) The effect of Itu on glycogen synthesis was not the result of inhibition of adenosine kinase, since 5'-amino-5'-deoxyadenosine, another inhibitor of this enzyme, had no effect on glycogen deposition. PMID:8503865

  20. An RNA Editor, Adenosine Deaminase Acting on Double-Stranded RNA (ADAR1)

    PubMed Central

    George, Cyril X.; John, Lijo

    2014-01-01

    Adenosine deaminase acting on RNA1 (ADAR1) catalyzes the C6 deamination of adenosine (A) to produce inosine (I) in regions of RNA with double-stranded (ds) character. This process is known as A-to-I RNA editing. Alternative promoters drive the expression of the Adar1 gene and alternative splicing gives rise to transcripts that encode 2 ADAR1 protein size isoforms. ADAR1 p150 is an interferon (IFN)-inducible dsRNA adenosine deaminase found in the cytoplasm and nucleus, whereas ADAR1 p110 is constitutively expressed and nuclear in localization. Dependent on the duplex structure of the dsRNA substrate, deamination of adenosine by ADAR can be either highly site-selective or nonspecific. A-to-I editing can alter the stability of RNA structures and the coding of RNA as I is read as G instead of A by ribosomes during mRNA translation and by polymerases during RNA replication. A-to-I editing is of broad physiologic significance. Both the production and the action of IFNs, and hence the subsequent interaction of viruses with their hosts, are among the processes affected by A-to-I editing. PMID:24905200

  1. Adenosine and Pediatric Supraventricular Tachycardia in the Emergency Department: Multicenter Study and Review

    Microsoft Academic Search

    Joseph D Losek; Erin Endom; Ann Dietrich; Gail Stewart; William Zempsky; Kathy Smith

    1999-01-01

    Study objective: To determine the frequency of successful cardioversion and the adverse effects of adenosine treatment in pediatric emergency department patients with supraventricular tachycardia (SVT). Methods: This was a multicenter descriptive study with both prospective (convenience sample) and retrospective (chart review) patient entry. The setting was 7 urban pediatric EDs with a yearly census range of 22,000 to 70,000 visits.

  2. Alteration of A 3 adenosine receptors in human neutrophils and low frequency electromagnetic fields

    Microsoft Academic Search

    Katia Varani; Stefania Gessi; Stefania Merighi; Valeria Iannotta; Elena Cattabriga; Cecilia Pancaldi; Ruggero Cadossi; Pier Andrea Borea

    2003-01-01

    The present study was designed to evaluate the binding and functional characterization of A3 adenosine receptors in human neutrophils exposed to low frequency, low energy, pulsing electromagnetic fields (PEMFs). Great interest has grown concerning the use of PEMF in the clinical practice for therapeutic purposes strictly correlated with inflammatory conditions. Saturation experiments performed using the high affinity and selective A3

  3. A radial distribution function approach to predict A 2B agonist effect of adenosine analogues

    Microsoft Academic Search

    Maykel Pérez González; Carmen Terán; Yagamare Fall; Marta Teijeira; Pedro Besada

    2005-01-01

    The radial distribution function (RDF) approach has been applied to the study of the A2B agonist effect of a set of 89 adenosine analogues reported with this activity. A model able to describe more than 70% of the variance in the experimental activity was developed with the use of the mentioned approach. In contrast, none of the eleven different approaches

  4. ADENOSINE TRIPHOSPHATE-INDUCED MOTILITY AND SLIDING OF FILAMENTS IN MAMMALIAN SPERM

    E-print Network

    Lindemann, Charles

    spermatozoa. Human sperm subjected to the same procedures showed similar patterns of reactivationADENOSINE TRIPHOSPHATE-INDUCED MOTILITY AND SLIDING OF FILAMENTS IN MAMMALIAN SPERM EXTRACTED, Oakland University, Rochester, Michigan 48063. ABSTRACT Bull sperm that had been extracted with 0

  5. NK cell-mediated cytotoxicity modulation by A(2) adenosine receptor agonist in different mammalian species.

    PubMed

    Kuldová, M; Svoboda, J; Kovár?, F; Vannucci, L; Kovár?, H; Fiserová, A

    2009-01-01

    Adenosines, endogenous purine nucleosides, appear in the extracellular space under metabolically stressful conditions associated with ischemia, inflammation, and cell damage. Their activity on innate immunity is prevalently inhibitory and can develop both in infectious and neoplastic diseases. During cancer development, tumor cells that release high concentrations of adenosines can impair the function of tumor-infiltrating lymphocytes and assist tumor growth by neo-angiogenesis. We evaluated the influence of A(2) adenosine receptor (A(2)AR) agonist on cytotoxic-cell response comparing human with other mammalian species (rodents, pigs, goats), both in healthy and in cancer conditions. The A(2)AR agonist developed dose-dependent inhibition of the cytotoxic activity of immune effector cells in all studied species. However, variability of the response was observed in relation to the species and the target cells that were used. Altogether, our data indicate that the A(2)AR plays a central role in adenosine-mediated inhibition of immune response to tumors. PMID:19826926

  6. Effect of Adenosine on the Management of Supraventricular Tachycardia by Urban Paramedics

    Microsoft Academic Search

    Michael Lozano; Barbara A McIntosh; Lorraine M. Giordano

    1995-01-01

    Study objective: To determine the effect of the addition of adenosine, as a standing-order medication, on the prehospital management of supraventricular tachycardia (SVT) in a large urban emergency medical services (EMS) system. Design: Prospective observational case series with historical controls. Setting: Large urban municipal EMS system staffed by paramedics and emergency medical technicians trained to operate automatic or semiautomatic defibrillators

  7. Coronary flow reserve improves after aortic valve replacement for aortic stenosis: an adenosine transthoracic echocardiography study

    Microsoft Academic Search

    David J. R Hildick-Smith; Leonard M Shapiro

    2000-01-01

    OBJECTIVESThe goal of this study was to assess coronary flow reserve (CFR) before and after aortic valve replacement (AVR).BACKGROUNDCoronary flow reserve is impaired under conditions of left ventricular (LV) hypertrophy. It is not known whether CFR improves with regression of LV hypertrophy in humans.METHODSWe investigated 35 patients with pure aortic stenosis, LV hypertrophy and normal coronary arteriograms. Patients underwent adenosine

  8. Structural basis of the substrate specificity of Bacillus cereus adenosine phosphorylase

    PubMed Central

    Dessanti, Paola; Zhang, Yang; Allegrini, Simone; Tozzi, Maria Grazia; Sgarrella, Francesco; Ealick, Steven E.

    2012-01-01

    Purine nucleoside phosphorylases catalyze the phosphorolytic cleavage of the glycosidic bond of purine (2?-deoxy)nucleosides, generating the corresponding free base and (2?-deoxy)­ribose 1-phosphate. Two classes of PNPs have been identified: homotrimers specific for 6-oxopurines and homohexamers that accept both 6-oxopurines and 6-aminopurines. Bacillus cereus adenosine phosphorylase (AdoP) is a hexameric PNP; however, it is highly specific for 6-aminopurines. To investigate the structural basis for the unique substrate specificity of AdoP, the active-site mutant D204N was prepared and kinetically characterized and the structures of the wild-type protein and the D204N mutant complexed with adenosine and sulfate or with inosine and sulfate were determined at high resolution (1.2–1.4?Å). AdoP interacts directly with the preferred substrate through a hydrogen-bond donation from the catalytically important residue Asp204 to N7 of the purine base. Comparison with Escherichia coli PNP revealed a more optimal orientation of Asp204 towards N7 of adenosine and a more closed active site. When inosine is bound, two water molecules are interposed between Asp204 and the N7 and O6 atoms of the nucleoside, thus allowing the enzyme to find alternative but less efficient ways to stabilize the transition state. The mutation of Asp204 to asparagine led to a significant decrease in catalytic efficiency for adenosine without affecting the efficiency of inosine cleavage. PMID:22349225

  9. Increased Adenosine Monophosphate-Activated Protein Kinase Activity in Rat Hearts With Pressure-Overload Hypertrophy

    Microsoft Academic Search

    Rong Tian; Nicolas Musi; Jessica D'Agostino; Michael F. Hirshman; Laurie J. Goodyear

    Background—Recent reports suggest that activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), in response to acute changes in cellular energy status in cardiac and skeletal muscles, results in altered substrate utilization. We hypothesized that chronic alterations in myocardial energetics in hypertrophied hearts (left ventricular hypertrophy, LVH) will lead to elevated AMPK activity, which in turn regulates substrate utilization. Methods and

  10. [Sedative, hypnotic and anticonvulsive effects of an adenosine analogue WS090501].

    PubMed

    Li, Wei; Zhang, Jian-Jun

    2011-06-01

    This study is to examine the sedative, hypnotic and anticonvulsive effects of an adenosine analogue, WS090501. The spontaneous locomotor activity was recorded by open field equipment, and the EEG of rats was recorded by polyphysiograph. Pentylenetetrazol (PTZ)-induced seizure model was used. The spontaneous locomotor activity was decreased by WS090501 at various doses (0.06, 0.13, and 0.25 mg x kg(-1)), and the decreasing rate was 28.4%, 47.1% and 61.2% respectively. Furthermore, the effect of WS090501 on spontaneous locomotor activity of mice can be antagonized by DPCPX, a selective adenosine A1R antagonist, but cannot be antagonized by SCH58261, a selective adenosine A2AR antagonist. The NREM sleep was significantly increased by WS090501 (0.05 and 0.2 mg x kg(-1)), and the increasing rate was 27.6% and 102.8%, respectively, at 6th hour after administration. The REM sleep decreased significantly at the higher dose. PTZ induced serious convulsion in mice. The latency of convulsion was prolonged, and the number of seizure and mortality decreased after administration of WS090501. These results show that WS090501 has potent sedative, hypnotic and anticonvulsive effects, which may be mediated through adenosine A1R. PMID:21882539

  11. Adenosine, methacholine, and exercise challenges in children with asthma or paediatric chronic obstructive pulmonary disease

    Microsoft Academic Search

    A Avital; C Springer; E Bar-Yishay; S Godfrey

    1995-01-01

    BACKGROUND--Bronchial hyperreactivity to methacholine is present in children with asthma and other types of paediatric chronic obstructive pulmonary disease (COPD), while hyperreactivity to exercise is more specific for asthma. Adenosine 5'-monophosphate (AMP) is a potent bronchoconstrictor and, like exercise, may provoke asthma by activating mast cells. This study investigated the suitability of AMP as a specific challenge for asthma in

  12. Cardiac myocyte–secreted cAMP exerts paracrine action via adenosine receptor activation

    PubMed Central

    Sassi, Yassine; Ahles, Andrea; Truong, Dong-Jiunn Jeffery; Baqi, Younis; Lee, Sang-Yong; Husse, Britta; Hulot, Jean-Sébastien; Foinquinos, Ariana; Thum, Thomas; Müller, Christa E.; Dendorfer, Andreas; Laggerbauer, Bernhard; Engelhardt, Stefan

    2014-01-01

    Acute stimulation of cardiac ?-adrenoceptors is crucial to increasing cardiac function under stress; however, sustained ?-adrenergic stimulation has been implicated in pathological myocardial remodeling and heart failure. Here, we have demonstrated that export of cAMP from cardiac myocytes is an intrinsic cardioprotective mechanism in response to cardiac stress. We report that infusion of cAMP into mice averted myocardial hypertrophy and fibrosis in a disease model of cardiac pressure overload. The protective effect of exogenous cAMP required adenosine receptor signaling. This observation led to the identification of a potent paracrine mechanism that is dependent on secreted cAMP. Specifically, FRET-based imaging of cAMP formation in primary cells and in myocardial tissue from murine hearts revealed that cardiomyocytes depend on the transporter ABCC4 to export cAMP as an extracellular signal. Extracellular cAMP, through its metabolite adenosine, reduced cardiomyocyte cAMP formation and hypertrophy by activating A1 adenosine receptors while delivering an antifibrotic signal to cardiac fibroblasts by A2 adenosine receptor activation. Together, our data reveal a paracrine role for secreted cAMP in intercellular signaling in the myocardium, and we postulate that secreted cAMP may also constitute an important signal in other tissues. PMID:25401477

  13. Adenosine A2A Receptors Modulate Acute Injury and Neuroinflammation in Brain Ischemia

    PubMed Central

    Pedata, Felicita; Pugliese, Anna Maria; Coppi, Elisabetta; Dettori, Ilaria; Maraula, Giovanna; Cellai, Lucrezia; Melani, Alessia

    2014-01-01

    The extracellular concentration of adenosine in the brain increases dramatically during ischemia. Adenosine A2A receptor is expressed in neurons and glial cells and in inflammatory cells (lymphocytes and granulocytes). Recently, adenosine A2A receptor emerged as a potential therapeutic attractive target in ischemia. Ischemia is a multifactorial pathology characterized by different events evolving in the time. After ischemia the early massive increase of extracellular glutamate is followed by activation of resident immune cells, that is, microglia, and production or activation of inflammation mediators. Proinflammatory cytokines, which upregulate cell adhesion molecules, exert an important role in promoting recruitment of leukocytes that in turn promote expansion of the inflammatory response in ischemic tissue. Protracted neuroinflammation is now recognized as the predominant mechanism of secondary brain injury progression. A2A receptors present on central cells and on blood cells account for important effects depending on the time-related evolution of the pathological condition. Evidence suggests that A2A receptor antagonists provide early protection via centrally mediated control of excessive excitotoxicity, while A2A receptor agonists provide protracted protection by controlling massive blood cell infiltration in the hours and days after ischemia. Focus on inflammatory responses provides for adenosine A2A receptor agonists a wide therapeutic time-window of hours and even days after stroke. PMID:25165414

  14. Neuroprotection by Caffeine and A 2A Adenosine Receptor Inactivation in a Model of Parkinson's Disease

    Microsoft Academic Search

    Jiang-Fan Chen; Kui Xu; Jacobus P. Petzer; Roland Staal; Yue-Hang Xu; Mark Beilstein; Patricia K. Sonsalla; Kay Castagnoli; Neal Castagnoli Jr; Michael A. Schwarzschild

    Recent epidemiological studies have established an associa- tion between the common consumption of coffee or other caffeinated beverages and a reduced risk of developing Parkin- son's disease (PD). To explore the possibility that caffeine helps prevent the dopaminergic deficits characteristic of PD, we in- vestigated the effects of caffeine and the adenosine receptor subtypes through which it may act in

  15. Adenosine accelerates the healing of diabetic ischemic ulcers by improving autophagy of endothelial progenitor cells grown on a biomaterial

    PubMed Central

    Chen, Wen; Wu, Yangxiao; Li, Li; Yang, Mingcan; Shen, Lei; Liu, Ge; Tan, Ju; Zeng, Wen; Zhu, Chuhong

    2015-01-01

    Endothelial progenitor cells (EPCs) seeded on biomaterials can effectively promote diabetic ischemic wound healing. However, the function of transplanted EPCs is negatively affected by a high-glucose and ischemic microenvironment. Our experiments showed that EPC autophagy was inhibited and mitochondrial membrane potential (MMP) was increased in diabetic patients, while adenosine treatment decreased the energy requirements and increased the autophagy levels of EPCs. In animal experiments, we transplanted a biomaterial seeded with EPCs onto the surface of diabetic wounds and found that adenosine-stimulated EPCs effectively promoted wound healing. Increased microvascular genesis and survival of the transplanted cells were also observed in the adenosine-stimulated groups. Interestingly, our study showed that adenosine increased the autophagy of the transplanted EPCs seeded onto the biomaterial and maintained EPC survival at 48 and 96?hours. Moreover, we observed that adenosine induced EPC differentiation through increasing the level of autophagy. In conclusion, our study indicated that adenosine-stimulated EPCs seeded onto a biomaterial significantly improved wound healing in diabetic mice; mechanistically, adenosine might maintain EPC survival and differentiation by increasing high glucose-inhibited EPC autophagy and maintaining cellular energy metabolism. PMID:26108983

  16. Aptamer-conjugated magnetic nanoparticles for extraction of adenosine from urine followed by electrospray ion mobility spectrometry.

    PubMed

    Najafabadi, Marzieh Enteshari; Khayamian, Taghi; Hashemian, Zahra

    2015-03-25

    Magnetic nanoparticles (MNPs) conjugated with aptamer was developed for the selective extraction of adenosine in urine samples followed by electrospray ionization-ion mobility spectrometry (ESI-IMS). The ion mobility spectrum of adenosine showed two peaks at low concentrations and two more peaks related to dimer of adenosine at high concentrations. However, the ion mobility spectrum of eluent at low concentration showed only the peaks related to dimer of adenosine. In other words, aptamer captured two adenosine molecules between the top G-quartet and the two short stems, where they bonded to each other. The mass spectrum of the eluent also validated the presence of dimer (m/z 535.95). The effect of extraction parameters on extraction efficiency including sorbent amount, elution conditions (solvent type and volume) and adsorption conditions were investigated. Under the optimized conditions, the linear dynamic range was found to be 0.05-5.00 ?g mL(-1) with detection limit of 0.02 ?g mL(-1). The extraction efficiency was 94% and the relative standard deviation was 4% for three replicate measurements of adenosine at 0.25 ?g mL(-1) in urine samples. As a practical application, the method was applied for the determination of adenosine in urine samples of patients with lung cancer, and the obtained results were in good agreement with those obtained by HPLC-UV method. Therefore, the proposed method is an alternative clinical analysis. PMID:25625475

  17. Adenosine decreases post-ischaemic cardiac TNF-alpha production: anti-inflammatory implications for preconditioning and transplantation.

    PubMed Central

    Meldrum, D R; Cain, B S; Cleveland, J C; Meng, X; Ayala, A; Banerjee, A; Harken, A H

    1997-01-01

    Tumour necrosis factor-alpha (TNF-alpha) is an autocrine contributor to myocardial dysfunction and cardiomyocyte death in ischaemia-reperfusion injury (I/R), sepsis, chronic heart failure and cardiac allograft rejection. Cardiac resident macrophages, infiltrating leucocytes, and cardiomyocytes themselves produce TNF-alpha. Although adenosine reduces macrophage TNF-alpha production and protects myocardium against I/R, it remains unknown whether I/R induces an increase in cardiac TNF-alpha in a crystalloid-perfused model (in the absence of blood), and, whether adenosine decreases cardiac TNF-alpha and protects function after I/R. To study this, isolated rat hearts were crystalloid-perfused using the Langendorff method and subjected to I/R, with or without adenosine pretreatment. Post-ischaemic cardiac TNF-alpha (enzyme-linked immunosorbent assay and bioassay) and function were determined (Langendorff). I/R increased cardiac TNF-alpha and impaired myocardial function. Adenosine decreased cardiac TNF-alpha and improved post-ischaemic functional recovery. This study demonstrates that: first, I/R induces an increase in cardiac tissue TNF-alpha in a crystalloid-perfused model: second, adenosine decreases cardiac TNF-alpha and improves post-ischaemic myocardial function; third, decreased cardiac TNF-alpha may represent a mechanism by which adenosine protects myocardium; and fourth, adenosine-induced suppression of cardiac TNF-alpha may provide an anti-inflammatory link to preconditioning and have implications for cardiac allograft preservation. PMID:9497488

  18. Adenosine accelerates the healing of diabetic ischemic ulcers by improving autophagy of endothelial progenitor cells grown on a biomaterial.

    PubMed

    Chen, Wen; Wu, Yangxiao; Li, Li; Yang, Mingcan; Shen, Lei; Liu, Ge; Tan, Ju; Zeng, Wen; Zhu, Chuhong

    2015-01-01

    Endothelial progenitor cells (EPCs) seeded on biomaterials can effectively promote diabetic ischemic wound healing. However, the function of transplanted EPCs is negatively affected by a high-glucose and ischemic microenvironment. Our experiments showed that EPC autophagy was inhibited and mitochondrial membrane potential (MMP) was increased in diabetic patients, while adenosine treatment decreased the energy requirements and increased the autophagy levels of EPCs. In animal experiments, we transplanted a biomaterial seeded with EPCs onto the surface of diabetic wounds and found that adenosine-stimulated EPCs effectively promoted wound healing. Increased microvascular genesis and survival of the transplanted cells were also observed in the adenosine-stimulated groups. Interestingly, our study showed that adenosine increased the autophagy of the transplanted EPCs seeded onto the biomaterial and maintained EPC survival at 48 and 96?hours. Moreover, we observed that adenosine induced EPC differentiation through increasing the level of autophagy. In conclusion, our study indicated that adenosine-stimulated EPCs seeded onto a biomaterial significantly improved wound healing in diabetic mice; mechanistically, adenosine might maintain EPC survival and differentiation by increasing high glucose-inhibited EPC autophagy and maintaining cellular energy metabolism. PMID:26108983

  19. International Union of Basic and Clinical Pharmacology. LXXXI. Nomenclature and Classification of Adenosine Receptors—An Update

    PubMed Central

    IJzerman, Adriaan P.; Jacobson, Kenneth A.; Linden, Joel; Müller, Christa E.

    2011-01-01

    In the 10 years since our previous International Union of Basic and Clinical Pharmacology report on the nomenclature and classification of adenosine receptors, no developments have led to major changes in the recommendations. However, there have been so many other developments that an update is needed. The fact that the structure of one of the adenosine receptors has recently been solved has already led to new ways of in silico screening of ligands. The evidence that adenosine receptors can form homo- and heteromultimers has accumulated, but the functional significance of such complexes remains unclear. The availability of mice with genetic modification of all the adenosine receptors has led to a clarification of the functional roles of adenosine, and to excellent means to study the specificity of drugs. There are also interesting associations between disease and structural variants in one or more of the adenosine receptors. Several new selective agonists and antagonists have become available. They provide improved possibilities for receptor classification. There are also developments hinting at the usefulness of allosteric modulators. Many drugs targeting adenosine receptors are in clinical trials, but the established therapeutic use is still very limited. PMID:21303899

  20. Differences in adenosine A-1 and A-2 receptor density revealed by autoradiography in methylxanthine-sensitive and insensitive mice

    SciTech Connect

    Jarvis, M.F.; Williams, M.

    1988-07-01

    Two strains of inbred mice, CBA/J and SWR/J, have been identified which are, respectively, sensitive and insensitive to the behavioral and toxic effects of methylxanthines. Autoradiographic analyses of brain adenosine receptors were conducted with (/sup 3/H)CHA to label adenosine A-1 receptors and (/sup 3/H)NECA, in the presence of 50 nM CPA, to label adenosine A-2 receptors. For both mouse strains, adenosine A-1 receptors were most highly concentrated in the hippocampus and cerebellum whereas adenosine A-2 receptors were selectively localized in the striatum. CBA/J mice displayed a 30% greater density of adenosine A-1 receptors in the hippocampal CA-1 and CA-3 regions and in the cerebellum as compared to the SWR/J mice. The number of A-2 receptors (Bmax) was 40% greater in the striatum and olfactory tubercle of CBA/J as compared to SWR/J mice. No significant regional differences in A-1 or A-2 receptor affinities were observed between these inbred strains of mice. These results indicate that the differential sensitivity to methylxanthines between these mouse strains may reflect a genetically mediated difference in regional adenosine receptor densities.

  1. Functionalized Congeners of 1,4-Dihydropyridines as Antagonist Molecular Probes for A3 Adenosine Receptors

    PubMed Central

    Li, An-Hu; Chang, Louis; Ji, Xiao-duo; Melman, Neli; Jacobson, Kenneth A.

    2012-01-01

    4-Phenylethynyl-6-phenyl-1,4-dihydropyridine derivatives are selective antagonists at human A3 adenosine receptors, with Ki values in a radioligand binding assay vs [125I]AB-MECA [N6-(4-amino-3-iodobenzyl)-5?-N-methylcarbamoyl-adenosine] in the submicromolar range. In this study, functionalized congeners of 1,4-dihydropyridines were designed as chemically reactive adenosine A3 antagonists, for the purpose of synthesizing molecular probes for this receptor subtype. Selectivity of the new analogues for cloned human A3 adenosine receptors was determined in radioligand binding in comparison to binding at rat brain A1 and A2A receptors. Benzyl ester groups at the 3- and/or 5-positions and phenyl groups at the 2- and/or 6-positions were introduced as potential sites for chain attachment. Structure–activity analysis at A3 adenosine receptors indicated that 3,5-dibenzyl esters, but not 2,6-diphenyl groups, are tolerated in binding. Ring substitution of the 5-benzyl ester with a 4-fluorosulfonyl group provided enhanced A3 receptor affinity resulting in a Ki value of 2.42 nM; however, a long-chain derivative containing terminal amine functionalization at the 4-position of the 5-benzyl ester showed only moderate affinity. This sulfonyl fluoride derivative appeared to bind irreversibly to the human A3 receptor (1 h incubation at 100 nM resulting in the loss of 56% of the specific radioligand binding sites), while the binding of other potent dihydropyridines and other antagonists was generally reversible. At the 3-position of the dihydropyridine ring, an amine-functionalized chain attached at the 4-position of a benzyl ester provided higher A3 receptor affinity than the corresponding 5-position isomer. This amine congener was also used as an intermediate in the synthesis of a biotin conjugate, which bound to A3 receptors with a Ki value of 0.60 ?M. PMID:10411465

  2. Enhancement of tumor immunotherapy by deletion of the A2A adenosine receptor

    PubMed Central

    Alme, Angela; Senaldi, Liana; Zarek, Paul E.; Horton, Maureen; Powell, Jonathan D.

    2013-01-01

    The A2A adenosine receptor plays a critical and non-redundant role in suppressing inflammation at sites of hypoxia and tissue damage. The tumor microenvironment has high levels of adenosine as a result of hypoxia and ectopic expression of enzymes responsible for the generation of extracellular adenosine. Thus, we sought to determine the ability of A2A receptor null mice to immunologically reject tumors. We observed that mice lacking the A2A adenosine receptor showed significantly delayed growth of lymphoma cells when compared to WT mice. Furthermore, when immunized with a low dose of tumor or with an irradiated GM-CSF–secreting tumor vaccine, A2A receptor null mice showed significantly enhanced protection from a subsequent high-dose challenge from both immunogenic and poorly immunogenic tumor lines. This increase in protection was accompanied by an increase in the number of tumor-antigen-specific CD8 T cells at the vaccine-site draining lymph node. Finally, we found that A2A receptor null mice displayed more robust anti-tumor responses than WT mice when they were treated with a soluble B7-DC/Fc fusion protein designed to antagonize B7-H1-mediated co-inhibition. This combinatorial immunotherapy strategy could also be recapitulated with pharmacological A2A receptor blockade paired with B7-DC/Fc administration. In light of these data, we believe that blockade of the A2A adenosine receptor is an attractive target for tumor immunotherapy that synergizes with other immunomodulatory approaches currently in clinical trials. PMID:22116345

  3. ATP and adenosine in the local regulation of water transport and homeostasis by the kidney

    PubMed Central

    Rieg, Timo; Vallon, Volker

    2009-01-01

    Regulation of body water homeostasis is critically dependent on the kidney and under the control of AVP, which is released from the neurohypophysis. In the collecting duct (CD) of the kidney, AVP activates adenylyl cyclase via vasopressin V2 receptors. cAMP-dependent activation of protein kinase A phosphorylates the water channel aquaporin-2 and increases water permeability by insertion of aquaporin-2 into the apical cell membrane. However, local factors modulate the effects of AVP to fine tune its effects, accelerate responses, and potentially protect the integrity of CD cells. Nucleotides like ATP belong to these local factors and act in an autocrine and paracrine way to activate P2Y2 receptors on CD cells. Extracellular breakdown of ATP and cAMP forms adenosine, the latter also induces specific effects on the CD by activation of adenosine A1 receptors. Activation of both receptor types can inhibit the cAMP-triggered activation of protein kinase A and reduce water permeability and transport. This review focuses on the role and potential interactions of the ATP and adenosine system with regard to the regulation of water transport in the CD. We address the potential stimuli and mechanisms involved in nucleotide release and adenosine formation, and discuss the corresponding signaling cascades that are activated. Potential interactions between the ATP and adenosine system, as well as other factors involved in the regulation of CD function, are outlined. Data from pharmacological studies and gene-targeted mouse models are presented to demonstrate the in vivo relevance to water transport and homeostasis. PMID:19020292

  4. Role of nitric oxide in adenosine-induced vasodilation in humans

    NASA Technical Reports Server (NTRS)

    Costa, F.; Biaggioni, I.; Robertson, D. (Principal Investigator)

    1998-01-01

    Vasodilation is one of the most prominent effects of adenosine and one of the first to be recognized, but its mechanism of action is not completely understood. In particular, there is conflicting information about the potential contribution of endothelial factors. The purpose of this study was to explore the role of nitric oxide in the vasodilatory effect of adenosine. Forearm blood flow responses to intrabrachial adenosine infusion (125 microg/min) were assessed with venous occlusion plethysmography during intrabrachial infusion of saline or the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) (12.5 mg/min). Intrabrachial infusions of acetylcholine (50 microg/min) and nitroprusside (3 microg/min) were used as a positive and negative control, respectively. These doses were chosen to produce comparable levels of vasodilation. In a separate study, a second saline infusion was administered instead of L-NMMA to rule out time-related effects. As expected, pretreatment with L-NMMA reduced acetylcholine-induced vasodilation; 50 microg/min acetylcholine increased forearm blood flow by 150+/-43% and 51+/-12% during saline and L-NMMA infusion, respectively (P<.01, n=6). In contrast, L-NMMA did not affect the increase in forearm blood flow produced by 3 microg/min nitroprusside (165+/-30% and 248+/-41% during saline and L-NMMA, respectively) or adenosine (173+/-48% and 270+/-75% during saline and L-NMMA, respectively). On the basis of our observations, we conclude that adenosine-induced vasodilation is not mediated by nitric oxide in the human forearm.

  5. The adenosine receptor affinities and monoamine oxidase B inhibitory properties of sulfanylphthalimide analogues.

    PubMed

    Van der Walt, Mietha M; Terre'Blanche, Gisella; Petzer, Anél; Petzer, Jacobus P

    2015-04-01

    Based on a report that sulfanylphthalimides are highly potent monoamine oxidase (MAO) B selective inhibitors, the present study examines the adenosine receptor affinities and MAO-B inhibitory properties of a series of 4- and 5-sulfanylphthalimide analogues. Since adenosine antagonists (A1 and A2A subtypes) and MAO-B inhibitors are considered agents for the therapy of neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease, dual-target-directed drugs that antagonize adenosine receptors and inhibit MAO-B may have enhanced therapeutic value. The results document that the sulfanylphthalimide analogues are selective for the adenosine A1 receptor over the A2A receptor subtype, with a number of compounds also possessing MAO-B inhibitory properties. Among the compounds evaluated, 5-[(4-methoxybenzyl)sulfanyl]phthalimide was found to possess the highest binding affinity to adenosine A1 receptors with a Ki value of 0.369 ?M. This compound is reported to also inhibit MAO-B with an IC50 value of 0.020 ?M. Such dual-target-directed compounds may act synergistic in the treatment of Parkinson's disease: antagonism of the A1 receptor may facilitate dopamine release, while MAO-B inhibition may reduce dopamine metabolism. Additionally, dual-target-directed compounds may find therapeutic value in Alzheimer's disease: antagonism of the A1 receptor may be beneficial in the treatment of cognitive dysfunction, while MAO-B inhibition may exhibit neuroprotective properties. In neurological diseases, such as Parkinson's disease and Alzheimer's disease, dual-target-directed drugs are expected to be advantageous over single-target treatments. PMID:25746740

  6. Kinetic characterization of adenosine A2 receptor-mediated relaxation in isolated rabbit aorta.

    PubMed

    Wiener, H L; Thalody, G P

    1993-07-01

    Previous studies in our laboratory (Wiener et al., 1991, Soc. Neurosci. Abstr. 17, 989) have addressed aspects of the functional antagonism between the responses mediated by activated adenosine A2 receptors and alpha 1-adrenoceptors in adventitia- and endothelium-denuded rabbit thoracic aortic rings by steady-state protocols which ignore the time course of response generation. In the present communication we describe aspects of the time-dependent kinetics of relaxation responses to adenosine A2 receptor agonists in tissues pre-contracted with the alpha 1-adrenoceptor agonist phenylephrine. The results were analyzed by application of the model originally developed by Keitz et al. (1990, J. Pharmacol. Exp. Ther. 255, 650) to describe the relaxation response, to a beta-adrenoceptor agonist, as a first-order exponential decrease in tissue tension over time to estimate the apparent rate constant for relaxation (krel) and the magnitude of relaxation at equilibrium. The magnitude of the relaxation responses to adenosine, N6-cyclohexyladenosine, N6-methyladenosine, 5'-N-ethylcarboxamidoadenosine, and R(-)-N6-(2-phenylisopropyl)adenosine were agonist concentration-dependent and saturable, as were the apparent rate constants for relaxation. In addition, the magnitude of the apparent rate constants for relaxation and the relaxation responses were inversely proportional to the fractional occupancy of the alpha 1-adrenoceptor. The hypothesis put forth by Keitz et al. that the maximal value of the apparent rate constant for relaxation may serve as the kinetic definition of agonist efficacy was also tested and found to be invalid for the adenosine A2 receptor. We propose that this pair of activated receptors and tissue preparation is a good model to study quantitative aspects of functional antagonism by kinetic paradigms. PMID:8405084

  7. Pre-excited atrial fibrillation triggered by intravenous adenosine: a commonly used drug with potentially life-threatening adverse effects.

    PubMed

    Turley, A J; Murray, S; Thambyrajah, J

    2008-01-01

    Although serious adverse events following adenosine administration are rare, it should only be administered in an environment where continuous ECG monitoring and emergency resuscitation equipment are available. The case report describes the development of pre-excited atrial fibrillation in a 31-year-old woman with Wolff-Parkinson-White syndrome following the administration of adenosine. She had previously been fit and well and was admitted to the coronary care unit with a 2 h history of regular palpitations. A 12-lead ECG showed a narrow QRS complex tachycardia. Carotid sinus massage was unsuccessful in terminating the tachycardia and the patient subsequently received rapid boluses of intravenous adenosine. The cardiac rhythm degenerated into atrial fibrillation with ventricular pre-excitation following 12 mg adenosine. PMID:18156545

  8. Effects of omeprazole treatment on nucleoside transporter expression and adenosine uptake in rat gastric mucosa.

    PubMed

    Redzic, Zoran B; Hasan, Fuad A; Al-Sarraf, Hameed

    2009-05-01

    Increased adenosine concentration inhibits gastric acid secretion in rat via adenosine A1 and A2A receptors, whereas achlorhydria suppresses A1 and A2A receptor gene expression. This study aimed to examine the effects of omeprazole-induced achlorhydria on the expression and functional activity of nucleoside transporters in rat gastric mucosa. Wistar rats were treated for either 1 or 3 days with 0.4 mmol/kg omeprazole via gavage; controls were treated with vehicle. The expression of nucleoside transporters at the transcript level was explored by quantitative real-time polymerase chain reaction assays; the functional activity of nucleoside transporters in gastric mucosa was explored by observing [3H]adenosine uptake in vitro. Gastric mucosa expressed rat equilibrative nucleoside transporter (rENT) 1 and 2, and rat concentrative nucleoside transporter (rCNT) 1, 2, and 3 at the transcript level, and the estimated values for the threshold cycles for target amplification (Ct) were 31.5 +/- 2, 28.5 +/- 2.1, 32.9 +/- 2.2, 29.1 +/- 2, and 28.9 +/- 2.5, respectively (n = 3 or 4). The Ct value for rat beta-actin was 21.9 +/- 1.8 (n = 4). In vitro uptake of [3H]adenosine by gastric mucosa samples consisted of Na+-dependent and Na+-independent components. One-day omeprazole treatment caused no change in nucleoside transporter mRNA levels or in [3H]adenosine uptake. Three-day omeprazole treatments, however, led to a 12-fold and 17-fold increase in rENT2 and rCNT1 mRNA levels, respectively. Samples taken after 3 days of treatment also took up significantly more [3H]adenosine than did samples from the corresponding control. In conclusion, the possible modification of nucleoside transport activities by changes in intraluminal acidity may have significance as part of a purinergic regulatory feedback mechanism in the control of gastric acid secretion. PMID:19448739

  9. Regulation of aggregate size and pattern by adenosine and caffeine in cellular slime molds

    PubMed Central

    2012-01-01

    Background Multicellularity in cellular slime molds is achieved by aggregation of several hundreds to thousands of cells. In the model slime mold Dictyostelium discoideum, adenosine is known to increase the aggregate size and its antagonist caffeine reduces the aggregate size. However, it is not clear if the actions of adenosine and caffeine are evolutionarily conserved among other slime molds known to use structurally unrelated chemoattractants. We have examined how the known factors affecting aggregate size are modulated by adenosine and caffeine. Result Adenosine and caffeine induced the formation of large and small aggregates respectively, in evolutionarily distinct slime molds known to use diverse chemoattractants for their aggregation. Due to its genetic tractability, we chose D. discoideum to further investigate the factors affecting aggregate size. The changes in aggregate size are caused by the effect of the compounds on several parameters such as cell number and size, cell-cell adhesion, cAMP signal relay and cell counting mechanisms. While some of the effects of these two compounds are opposite to each other, interestingly, both compounds increase the intracellular glucose level and strengthen cell-cell adhesion. These compounds also inhibit the synthesis of cAMP phosphodiesterase (PdsA), weakening the relay of extracellular cAMP signal. Adenosine as well as caffeine rescue mutants impaired in stream formation (pde4- and pdiA-) and colony size (smlA- and ctnA-) and restore their parental aggregate size. Conclusion Adenosine increased the cell division timings thereby making large number of cells available for aggregation and also it marginally increased the cell size contributing to large aggregate size. Reduced cell division rates and decreased cell size in the presence of caffeine makes the aggregates smaller than controls. Both the compounds altered the speed of the chemotactic amoebae causing a variation in aggregate size. Our data strongly suggests that cytosolic glucose and extracellular cAMP levels are the other major determinants regulating aggregate size and pattern. Importantly, the aggregation process is conserved among different lineages of cellular slime molds despite using unrelated signalling molecules for aggregation. PMID:22269093

  10. Differential impact of adenosine nucleotides released by osteocytes on breast cancer growth and bone metastasis.

    PubMed

    Zhou, J Z; Riquelme, M A; Gao, X; Ellies, L G; Sun, L Z; Jiang, J X

    2015-04-01

    Extracellular ATP has been shown to either inhibit or promote cancer growth and migration; however, the mechanism underlying this discrepancy remained elusive. Here we demonstrate the divergent roles of ATP and adenosine released by bone osteocytes on breast cancers. We showed that conditioned media (CM) collected from osteocytes treated with alendronate (AD), a bisphosphonate drug, inhibited the migration of human breast cancer MDA-MB-231 cells. Removal of the extracellular ATP by apyrase in CM abolished this effect, suggesting the involvement of ATP. ATP exerted its inhibitory effect through the activation of purinergic P2X receptor signaling in breast cancer cells evidenced by the attenuation of the inhibition by an antagonist, oxidized ATP, as well as knocking down P2X7 with small interfering RNA (siRNA), and the inhibition of migration by an agonist, BzATP. Intriguingly, ATP had a biphasic effect on breast cancer cells-lower dosage inhibited but higher dosage promoted its migration. The stimulatory effect on migration was blocked by an adenosine receptor antagonist, MRS1754, ARL67156, an ecto-ATPase inhibitor, and A2A receptor siRNA, suggesting that in contrast to ATP, adenosine, a metabolic product of ATP, promoted migration of breast cancer cells. Consistently, non-hydrolyzable ATP, ATP?S, only inhibited but did not promote cancer cell migration. ATP also had a similar inhibitory effect on the Py8119 mouse mammary carcinoma cells; however, adenosine had no effect owing to the absence of the A2A receptor. Consistently, ATP?S inhibited, whereas adenosine promoted anchorage-independent growth of MDA-MB-231 cells. Our in vivo xenograft study showed a significant delay of tumor growth with the treatment of ATP?S. Moreover, the extent of bone metastasis in a mouse intratibial model was significantly reduced with the treatment of ATP?S. Together, our results suggest the distinct roles of ATP and adenosine released by osteocytes and the activation of corresponding receptors P2X7 and A2A signaling on breast cancer cell growth, migration and bone metastasis. PMID:24837364

  11. LY 294002 inhibits adenosine receptor activation by a mechanism independent of effects on PI-3 kinase or casein kinase II.

    PubMed

    Searl, T J; Silinsky, E M

    2005-12-01

    Adenosine reduces both evoked and spontaneous calcium-dependent acetylcholine (ACh) release through a mechanism downstream of calcium entry at amphibian motor nerve endings (Silinsky EM. J Physiol 1984; 346: 243-56). LY 294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one), an inhibitor of both phosphoinositide-3 kinase (PI-3 kinase) and casein kinase II, has been reported to increase spontaneous ACh release reflected in miniature endplate potential (MEPP) frequencies independently of intraterminal calcium at the frog neuromuscular junction (Rizzoli SO, Betz WJ. J Neurosci 2002; 22: 10680-9). It has been suggested that the increase in MEPP frequency caused by LY 294002, is mediated through an action on synaptotagmins, vesicle associated calcium sensors believed to trigger synaptic vesicle exocytosis. We thus examined the effects of adenosine on MEPP frequencies and evoked ACh release reflected as endplate potentials (EPPs) in order to determine if the presumed calcium-independent ACh release is affected by adenosine. We also wanted to determine if PI-3 kinase or casein kinase II is involved in mediating or modulating the inhibitory effects of adenosine. To these ends, we examined the effects of adenosine in the presence of LY 294002, wortmannin (a highly selective the PI-3 kinase inhibitor), or DRB (5,6-dichlorobenzimidazole riboside, an inhibitor of casein kinase II). LY 294002 reduced the sensitivity of both MEPP frequencies and the nerve-evoked calcium dependent EPPs to adenosine. The occlusive effects of LY 294002 on the actions of adenosine on MEPPs and EPPs were overcome by increasing adenosine concentration. Neither wortmannin nor DRB had any effect on the sensitivity of the EPPs to adenosine indicating that neither PI-3 kinase nor casein kinase II inhibition mediates the reduction in motor-nerve terminal sensitivity to adenosine produced by LY 294002. The results indicate a competitive relationship between LY 294002 and adenosine at A(1) receptors at the frog neuromuscular junction. This effect is independent of the previously described effects of LY 294002 on the exocytotic process, and is also independent of PI-3 kinase or casein kinase II. PMID:18404524

  12. Interactions between caffeine and cocaine in tests of motor activity: role of the adenosine A2 receptor

    E-print Network

    Snow, Steven Wayne

    1993-01-01

    as decreases in schedule-controlled operant responding (Coffin and Carney, 1983). These effects were selectively blocked by 13 caffeine and other methylxanthines (Yarbrough and McGuffin-Clineschmidt, 1981). Thus, the interaction between caffeine.... L. and Carney, J. M. (1983) Behavioral pharmacology of adenosine analogs. In: Physiology and Pharmacologyof Adenosine Derivative (Daly, J. W. , Ed. ), pp. 267-274. Raven Press, New York. Colpaert, F. C. , Desmedt, L. K. , and Janssen, P. J. (1976...

  13. Chronic intrathecal morphine treatment does not cause down-regulation of spinal adenosine A 1 receptors in rats

    Microsoft Academic Search

    Pao-Luh Tao; Chih-Shung Wong; Mei-Chuan Lin

    1996-01-01

    We have shown previously that systemic chronic morphine treatment causes down-regulation of spinal adenosine A1 receptors in rats. Recently, we have found that chronic supraspinal morphine treatment also causes this effect. In the present study, we investigated whether chronic spinal morphine treatment has the same effect of down-regulation of spinal adenosine A1 receptors. Adult male Sprague-Dawley rats were rendered tolerant

  14. Acyl Coenzyme A Synthetase from Pseudomonas fragi Catalyzes the Synthesis of Adenosine 5?-Polyphosphates and Dinucleoside Polyphosphates†

    PubMed Central

    Fontes, Rui; Günther Sillero, Maria A.; Sillero, Antonio

    1998-01-01

    Acyl coenzyme A (CoA) synthetase (EC 6.2.1.8) from Pseudomonas fragi catalyzes the synthesis of adenosine 5?-tetraphosphate (p4A) and adenosine 5?-pentaphosphate (p5A) from ATP and tri- or tetrapolyphosphate, respectively. dATP, adenosine-5?-O-[?-thiotriphosphate] (ATP?S), adenosine(5?)tetraphospho(5?)adenosine (Ap4A), and adenosine(5?)pentaphospho(5?)adenosine (Ap5A) are also substrates of the reaction yielding p4(d)A in the presence of tripolyphosphate (P3). UTP, CTP, and AMP are not substrates of the reaction. The Km values for ATP and P3 are 0.015 and 1.3 mM, respectively. Maximum velocity was obtained in the presence of MgCl2 or CoCl2 equimolecular with the sum of ATP and P3. The relative rates of synthesis of p4A with divalent cations were Mg = Co > Mn = Zn >> Ca. In the pH range used, maximum and minimum activities were measured at pH values of 5.5 and 8.2, respectively; the opposite was observed for the synthesis of palmitoyl-CoA, with maximum activity in the alkaline range. The relative rates of synthesis of palmitoyl-CoA and p4A are around 10 (at pH 5.5) and around 200 (at pH 8.2). The synthesis of p4A is inhibited by CoA, and the inhibitory effect of CoA can be counteracted by fatty acids. To a lesser extent, the enzyme catalyzes the synthesis also of Ap4A (from ATP), Ap5A (from p4A), and adenosine(5?)tetraphospho(5?)nucleoside (Ap4N) from adequate adenylyl donors (ATP, ATP?S, or octanoyl-AMP) and adequate adenylyl acceptors (nucleoside triphosphates). PMID:9620965

  15. Adenosine triphosphatase in nerves and ganglia of rats with streptozotocin-induced diabetes or galactosaemia; effects of aldose reductase inhibition

    Microsoft Academic Search

    J. E. Lambourne; A. M. Brown; N. Calcutt; D. R. Tomlinson; G. B. Willars

    1988-01-01

    Summary  This study measured the ouabain-sensitive and ouabain-resistant adenosine triphosphatase activity in homogenates of the sciatic\\u000a nerves and of pooled fourth and fifth lumbar dorsal root ganglia from rats fed 20% galactose or made diabetic with streptozotocin\\u000a for either 4 or 8 weeks. Diabetes caused reductions in both fractions of sciatic nerve adenosine triphosphatase activity.\\u000a After 8 weeks the ouabainsensitive fraction

  16. A1 Adenosine Receptor Upregulation and Activation Attenuates Neuroinflammation and Demyelination in a Model of Multiple Sclerosis

    Microsoft Academic Search

    Shigeki Tsutsui; Jurgen Schnermann; Farshid Noorbakhsh; Scot Henry; V. Wee Yong; Brent W. Winston; Kenneth Warren; Christopher Power

    2004-01-01

    The neuromodulator adenosine regulates immune activation and neuronal survival through specific G-protein-coupled receptors ex- pressed on macrophages and neurons, including the A1 adenosine receptor (A1AR). Here we show that A1AR null (A1AR\\/) mice developed a severe progressive-relapsing form of experimental allergic encephalomyelitis (EAE) compared with their wild-type (A1AR\\/) littermates. Worsened demyelination, axonal injury, and enhanced activation of microglia\\/macrophages were observed

  17. A Highly Decreased Binding of Cyclic Adenosine Monophosphate to Protein Kinase A in Erythrocyte Membranes is Specific for Active Psoriasis

    Microsoft Academic Search

    Rudolf E. Schopf; Yvonne Langendorf; Roman E. Benz; Lothar Färber; Peter Benes

    2002-01-01

    A cyclic adenosine monophosphate binding abnormality in psoriatic erythrocytes that could be corrected by retinoid treatment has been reported. It was tested whether this binding abnormality is specific for psoriasis and the effects of treatment were compared with etretinate, cyclosporine A, or anthralin on 2-3H-8-N3-cyclic adenosine monophosphate binding to the regulatory subunit of protein kinase A in erythrocyte membranes. One

  18. Adenosine acts by A1 receptors to stimulate release of prolactin from anterior-pituitaries in vitro.

    PubMed

    Yu, W H; Kimura, M; Walczewska, A; Porter, J C; McCann, S M

    1998-06-23

    Adenosine has been identified in the anterior pituitary gland and is secreted from cultured folliculostellate (FS) cells. To determine whether adenosine controls the secretion of anterior pituitary hormones in vitro, adenosine was incubated with anterior pituitaries. It stimulated prolactin (PRL) release at the lowest concentration used (10(-10) M); the stimulation peaked at 10(-8) M with a threefold increase in release and declined to minimal stimulation at 10(-4) and 10(-3) M. Follicle-stimulating hormone release was maximally inhibited at 10(-8) M, whereas luteinizing hormone release was not significantly inhibited. Two selective A1 adenosine receptor antagonists (10(-7) or 10(-5) M) had no effect on basal PRL release, but either antagonist completely blocked the response to the most effective concentration of adenosine (10(-8) M). In contrast, a highly specific A2 receptor antagonist (10(-7) or 10(-5) M) had no effect on basal PRL release or the stimulation of PRL release induced by adenosine (10(-8) M). We conclude that adenosine acts to stimulate PRL release in vitro by activating A1 receptors. Since the A1 receptors decrease intracellular-free calcium, this would decrease the activation of nitric oxide synthase in the FS cells, resulting in decreased release of nitric oxide (NO). NO inhibits PRL release by activating guanylate cyclase that synthesizes cGMP from GTP; cGMP concentrations increase in the lactotrophs leading to inhibition of PRL release. In the case of adenosine, NO release from the FS cells decreases, resulting in decreased concentrations of NO in the lactotrophs, consequent decreased cGMP formation, and resultant increased PRL release. PMID:9636230

  19. Adenosine acts by A1 receptors to stimulate release of prolactin from anterior-pituitaries in vitro

    PubMed Central

    Yu, Wen H.; Kimura, Mayumi; Walczewska, Anna; Porter, John C.; McCann, Samuel M.

    1998-01-01

    Adenosine has been identified in the anterior pituitary gland and is secreted from cultured folliculostellate (FS) cells. To determine whether adenosine controls the secretion of anterior pituitary hormones in vitro, adenosine was incubated with anterior pituitaries. It stimulated prolactin (PRL) release at the lowest concentration used (10?10 M); the stimulation peaked at 10?8 M with a threefold increase in release and declined to minimal stimulation at 10?4 and 10?3 M. Follicle-stimulating hormone release was maximally inhibited at 10?8 M, whereas luteinizing hormone release was not significantly inhibited. Two selective A1 adenosine receptor antagonists (10?7 or 10?5 M) had no effect on basal PRL release, but either antagonist completely blocked the response to the most effective concentration of adenosine (10?8 M). In contrast, a highly specific A2 receptor antagonist (10?7 or 10?5 M) had no effect on basal PRL release or the stimulation of PRL release induced by adenosine (10?8 M). We conclude that adenosine acts to stimulate PRL release in vitro by activating A1 receptors. Since the A1 receptors decrease intracellular-free calcium, this would decrease the activation of nitric oxide synthase in the FS cells, resulting in decreased release of nitric oxide (NO). NO inhibits PRL release by activating guanylate cyclase that synthesizes cGMP from GTP; cGMP concentrations increase in the lactotrophs leading to inhibition of PRL release. In the case of adenosine, NO release from the FS cells decreases, resulting in decreased concentrations of NO in the lactotrophs, consequent decreased cGMP formation, and resultant increased PRL release. PMID:9636230

  20. Effects of adenosine A 3 receptor agonist on bone marrow granulocytic system in 5-fluorouracil-treated mice

    Microsoft Academic Search

    Michal Hofer; Milan Pospíšil; Antonín Vacek; Ji?ina Holá; Vladimír Znojil; Lenka Weiterová; Denisa Štreitová

    2006-01-01

    The purpose of the experiments reported was to investigate effects of N6-(3-iodobenzyl)adenosine-5’-N-methyluronamide (IB-MECA), a selective adenosine A3 receptor agonist, on the granulocytic system in femoral marrow of mice depleted by the cytotoxic drug 5-fluorouracil. In the phase of the highest cell depletion IB-MECA was injected i.p. at single doses of 200 nmol\\/kg given either once or twice daily in 2-

  1. Efficiency of purine utilization by Helicobacter pylori: roles for adenosine deaminase and a NupC homolog.

    PubMed

    Miller, Erica F; Vaish, Soumya; Maier, Robert J

    2012-01-01

    The ability to synthesize and salvage purines is crucial for colonization by a variety of human bacterial pathogens. Helicobacter pylori colonizes the gastric epithelium of humans, yet its specific purine requirements are poorly understood, and the transport mechanisms underlying purine uptake remain unknown. Using a fully defined synthetic growth medium, we determined that H. pylori 26695 possesses a complete salvage pathway that allows for growth on any biological purine nucleobase or nucleoside with the exception of xanthosine. Doubling times in this medium varied between 7 and 14 hours depending on the purine source, with hypoxanthine, inosine and adenosine representing the purines utilized most efficiently for growth. The ability to grow on adenine or adenosine was studied using enzyme assays, revealing deamination of adenosine but not adenine by H. pylori 26695 cell lysates. Using mutant analysis we show that a strain lacking the gene encoding a NupC homolog (HP1180) was growth-retarded in a defined medium supplemented with certain purines. This strain was attenuated for uptake of radiolabeled adenosine, guanosine, and inosine, showing a role for this transporter in uptake of purine nucleosides. Deletion of the GMP biosynthesis gene guaA had no discernible effect on mouse stomach colonization, in contrast to findings in numerous bacterial pathogens. In this study we define a more comprehensive model for purine acquisition and salvage in H. pylori that includes purine uptake by a NupC homolog and catabolism of adenosine via adenosine deaminase. PMID:22701700

  2. Changes in neuromodulatory effect of adenosine A1 receptors on piriform cortex field potentials in amygdala kindled rats.

    PubMed

    Rezvani, Mohammad Ebrahim; Mirnajafi-Zadeh, Javad; Fathollahi, Yaghoub; Palizvan, Mohammad Reza

    2007-06-22

    Adenosine exerts its anticonvulsants effect through different brain regions including piriform cortex. In this study, the effect of amygdala kindled seizures on adenosine A1 receptor-mediated neuromodulation in piriform cortex pyramidal neurons was tested at 24 h and 1 month after kindling. Animals were kindled by daily electrical stimulation of amygdala. Field potentials were recorded from layer II of piriform cortex pyramidal cells following stimulation of the lateral olfactory tract. Obtained results showed that N6-cyclohexyladenosine (CHA), a selective adenosine A1 receptor agonist (1, 10 and 100 microM; i.c.v.), reduced A1 slope and B1 amplitude of field potentials in both kindled and non-kindled (control) rats. However, its effects on kindled animals were more potent at 24 h, but not 1 month post-kindling. 8 cyclopenthyl-1,3-dimethylxanthine (CPT), a selective adenosine A1 receptor antagonist (50 microM, i.c.v.), had no significant effect on the field potential parameters. However, CPT (50 microM, i.c.v.) pretreatment eliminated effects of CHA (10 microM; i.c.v.) on the field potentials. These results indicate that activation of adenosine A1 receptors has an inhibitory effect on the field potentials of piriform cortex pyramidal neurons and the efficiency of adenosine A1 receptor neuromodulation in piriform cortex is increased at short-term (24 h) but return to normal at long-term (1 month) after kindling implementation. PMID:17359967

  3. Excess adenosine A2B receptor signaling contributes to priapism through HIF-1? mediated reduction of PDE5 gene expression

    PubMed Central

    Ning, Chen; Wen, Jiaming; Zhang, Yujin; Dai, Yingbo; Wang, Wei; Zhang, Weiru; Qi, Lin; Grenz, Almut; Eltzschig, Holger K.; Blackburn, Michael R.; Kellems, Rodney E.; Xia, Yang

    2014-01-01

    Priapism is featured with prolonged and painful penile erection and is prevalent among males with sickle cell disease (SCD). The disorder is a dangerous urological and hematological emergency since it is associated with ischemic tissue damage and erectile disability. Here we report that phosphodiesterase-5 (PDE5) gene expression and PDE activity is significantly reduced in penile tissues of two independent priapic models: SCD mice and adenosine deaminase (ADA)-deficient mice. Moreover, using ADA enzyme therapy to reduce adenosine or a specific antagonist to block A2B adenosine receptor (ADORA2B) signaling, we successfully attenuated priapism in both ADA?/? and SCD mice by restoring penile PDE5 gene expression to normal levels. This finding led us to further discover that excess adenosine signaling via ADORA2B activation directly reduces PDE5 gene expression in a hypoxia-inducible factor-1? (HIF-1?)-dependent manner. Overall, we reveal that excess adenosine-mediated ADORA2B signaling underlies reduced penile PDE activity by decreasing PDE5 gene expression in a HIF-1?-dependent manner and provide new insight for the pathogenesis of priapism and novel therapies for the disease.—Ning, C., Wen, J., Zhang, Y., Dai, Y., Wang, W., Zhang, W., Qi, L., Grenz, A., Eltzschig, H. K., Blackburn, M. R., Kellems, R. E., Xia, Y. Excess adenosine A2B receptor signaling contributes to priapism through HIF-1? mediated reduction of PDE5 gene expression. PMID:24614760

  4. Adenosine Diphosphoglucose-Starch Glucosyltransferases from Developing Kernels of Waxy Maize

    PubMed Central

    Ozbun, J. L.; Hawker, J. S.; Preiss, Jack

    1971-01-01

    Two adenosine diphosphoglucose: ?-1,4-glucan ?-4-glucosyl-transferases were extracted from kernels of waxy maize harvested 22 days after pollination and separated by gradient elution from a diethylaminoethyl-cellulose column. Both fractions could utilize amylopectin, amylose, glycogen, maltotriose and maltose as primers. The rate of glucose transfer from adenosine diphosphoglucose to rabbit liver glycogen of fraction II was 78% of the rate of glucose transfer to amylopectin, but with fraction I the rate of transfer of glucose to rabbit liver glycogen was 380% of that observed to amylopectin. Glucan synthesis in the absence of added primer was found in fraction I in the presence of 0.5 m sodium citrate and bovine serum albumin. The unprimed product was a methanol-precipitable glucan with principally ?-1,4 linkages and some ?-1,6 linkages, and its iodine spectrum was similar to that of amylopectin. PMID:16657876

  5. Quinazolines as Adenosine Receptor Antagonists: SAR and Selectivity for A2B Receptors

    PubMed Central

    Webb, Thomas R.; Lvovskiy, Dmitriy; Kim, Soon-Ai; Ji, Xiao-duo; Melman, Neli; Linden, Joel; Jacobson, Kenneth A.

    2012-01-01

    We have recently reported the discovery of numerous new compounds that are selective inhibitors of all of the subtypes of the adenosine receptor family via a pharmacophore database searching and screening strategy. During the course of this work we made the unexpected discovery of a potent A2B receptor antagonist, 4-methyl-7-methoxyquinazolyl-2-(2?-amino-4?-imidazolinone) (38, CMB 6446), which showed selectivity for this receptor and functioned as an antagonist, with a binding Ki value of 112 nM. We explored the effects of both substituent- and ring-structural variations on the receptor affinity in this series of derivatives, which were found to be mostly non-selective adenosine receptor ligands with Ki values in the micromolar range. Since no enhancement of A2B receptor affinity of 38 was achieved, the previously reported pharmacophore-based searching strategy yielded the most potent and selective structurally-related hit in the database originally searched. PMID:12467710

  6. The role of adenosine in hypoxic pulmonary vasoconstriction in the anaesthetized rat.

    PubMed

    Thomas, T; Marshall, J M

    1993-07-01

    In nine artificially ventilated rats anaesthetized with Saffan, systemic hypoxia induced a tachycardia followed by a bradycardia, a fall in systemic arterial pressure and an increase in pulmonary artery pressure (PPA) indicating pulmonary vasoconstriction. This increase in PPA was abolished by the adenosine receptor antagonist 8-phenyltheophylline (8-PT, 10 mg kg-1 I.V.). Further, in seven rats the Pa,O2 achieved during hypoxia was greater after 8-PT than before (38 vs. 40 mmHg). We suggest that adenosine makes a major contribution to hypoxia-induced pulmonary vasoconstriction in the rat. The better maintenance of Pa,O2 during hypoxia may reflect improved perfusion of well-ventilated alveoli. PMID:8398107

  7. Discovery of S-adenosyl-L-homocysteine hydrolase inhibitors based on non-adenosine analogs.

    PubMed

    Nakao, Akira; Suzuki, Hiroko; Ueno, Hiroaki; Iwasaki, Hiroshi; Setsuta, Tomofumi

    2014-09-01

    High throughput screening using Automated Ligand Identification System (ALIS) resulted in the discovery of a new series of S-adenosyl-L-homocysteine hydrolase inhibitors based on non-adenosine analogs. The optimization campaign led to very potent and competitive compound 39 with a Ki value of 1.5 nM. Compound 39 could be a promising lead compound for research to reduce elevated homocysteine levels. PMID:25022879

  8. Inhibition of Adenosine Triphosphatases in Vitro by Silver Nitrate and Silver Sulfadiazine

    Microsoft Academic Search

    B. R. Nechay; J. P. Saunders

    1984-01-01

    Inhibition of adenosine triphosphatase (ATPase) by silver nitrate (AgNO3) in vitro was studied in microsomal fractions or tissue homogenates of canine brain and kidney and human kidney. In microsomal fractions, AgNO3 was an indiscriminate inhibitor of ouabain-sensitive (Na+ + K+ ATPase) and ouabain-insensitive (Mg2+ ATPase) activities, with 50% inhibition obtaining at concentrations on the order of 10–7 to 10–6 M.

  9. Protective mechanisms of adenosine 5'-monophosphate in platelet activation and thrombus formation.

    PubMed

    Fuentes, E; Badimon, L; Caballero, J; Padró, T; Vilahur, G; Alarcón, M; Pérez, P; Palomo, I

    2014-03-01

    Platelet activation is relevant to a variety of acute thrombotic events. We sought to examine adenosine 5'-monophosphate (AMP) mechanisms of action in preventing platelet activation, thrombus formation and platelet-related inflammatory response. We assessed the effect of AMP on 1) P-selectin expression and GPIIb/IIIa activation by flow cytometry; 2) Platelet aggregation and ATP secretion induced by ADP, collagen, TRAP-6, convulxin and thrombin; 3) Platelet rolling and firm adhesion, and platelet-leukocyte interactions under flow-controlled conditions; and, 4) Platelet cAMP levels, sP-selectin, sCD40L, IL-1?, TGF-?1 and CCL5 release, PDE3A activity and PKA phosphorylation. The effect of AMP on in vivo thrombus formation was also evaluated in a murine model. The AMP docking with respect to A2 adenosine receptor was determined by homology. AMP concentration-dependently (0.1 to 3 mmol/l) inhibited P-selectin expression and GPIIb/IIIa activation, platelet secretion and aggregation induced by ADP, collagen, TRAP-6 and convulxin, and diminished platelet rolling and firm adhesion. Furthermore, AMP induced a marked increase in the rolling speed of leukocytes retained on the platelet surface. At these concentrations AMP significantly decreased inflammatory mediator from platelet, increased intraplatelet cAMP levels and inhibited PDE3A activity. Interestingly, SQ22536, ZM241385 and SCH58261 attenuated the antiplatelet effect of AMP. Docking experiments revealed that AMP had the same orientation that adenosine inside the A2 adenosine receptor binding pocket. These in vitro antithrombotic properties were further supported in an in vivo model of thrombosis. Considering the successful use of combined antiplatelet therapy, AMP may be further developed as a novel antiplatelet agent. PMID:24306059

  10. Purification and characterization of the adenosine A2-like binding site from human placental membrane.

    PubMed

    Hutchison, K A; Fox, I H

    1989-11-25

    We have purified and characterized the adenosine A2-like binding site from human placental membranes. 5'-N-Ethylcarboxamido[2,8-3H]adenosine ([3H]NECA) binds to this site, with a Kd of 240 nM and a Bmax of 13.0 pmol/mg in human placental membranes. The adenosine A2-like binding site was purified after extraction from placental membranes with 0.1% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid. The purification included ammonium sulfate precipitation and concanavalin A, DEAE-Sephadex, and Sepharose 6B gel filtration chromatographies. The protein was purified 127-fold to homogeneity, with a final specific activity of 1.5-1.9 nmol/mg of protein and a 5.5-8.1% yield of binding activity from the membranes. The purified protein had similar binding properties and an identical potency order for displacement of [3H] NECA by adenosine analogs as the initial membranes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified protein revealed a single band at 98 kDa which coeluted with [3H]NECA binding activity during Sepharose 6B gel filtration chromatography. In 0.1% Triton X-100, the binding complex has a Stokes radius of 70 A, a sedimentation coefficient of 6.9 S, and a partial specific volume of 0.698 ml/g. The detergent-protein complex has a calculated molecular mass of 230 kDa. The estimated frictional ratio is 1.5. The native binding complex appears to consist of a dimer of identical subunits. The function of this ubiquitous protein remains unclear. PMID:2584200

  11. Adenosine receptor-induced cyclic AMP generation and inhibition of 5-hydroxytryptamine release in human platelets.

    PubMed Central

    Cooper, J A; Hill, S J; Alexander, S P; Rubin, P C; Horn, E H

    1995-01-01

    1. We have assessed the effects of adenosine receptor agonists and antagonists on collagen-induced 5-hydroxytryptamine (5-HT) release and cyclic AMP generation in human platelets. 2. 5'-N-ethylcarboxamidoadenosine (NECA) and CGS 21680 elicited accumulations of cyclic AMP with mean EC50 values of 2678 and 980 nM, respectively. The maximal response to CGS 21680 was approximately half that of the response to 10 microM NECA. 3. NECA and CGS 21680 inhibited collagen-induced 5-hydroxytryptamine release with mean EC50 values of 960 and 210 nM, respectively. The maximal response to CGS 21680 was approximately 25% of the response to 10 microM NECA. 4. The A1/A2a-selective adenosine receptor antagonist PD 115,199 was more potent as an inhibitor of NECA-elicited responses than the A1-selective antagonist DPCPX with calculated Ki values of 22-32 nM and > 10 microM, respectively. 5. In the presence of a cyclic AMP phosphodiesterase inhibitor, the effects of CGS 21680 on cyclic AMP accumulation and 5-HT release were enhanced to levels similar to those elicited by 10 microM NECA. In the absence of phosphodiesterase inhibition, CGS 21680 did not antagonise the effects of NECA. Furthermore, endogenous adenosine did not contribute to the effects of CGS 21680 when phosphodiesterase was inhibited. 6. We conclude that an A2a adenosine receptor appears to be involved in the NECA-elicited increases in cyclic AMP levels and inhibition of 5-HT release in human platelets.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8527267

  12. Negative regulation of diacylglycerol kinase ? mediates adenosine-dependent hepatocyte preconditioning

    Microsoft Academic Search

    G Baldanzi; E Alchera; C Imarisio; M Gaggianesi; C Dal Ponte; M Nitti; C Domenicotti; W J van Blitterswijk; E Albano; A Graziani; R Carini

    2010-01-01

    In liver ischemic preconditioning (IP), stimulation of adenosine A2a receptors (A2aR) prevents ischemia\\/reperfusion injury by promoting diacylglycerol-mediated activation of protein kinase C (PKC). By concerting diacylglycerol to phosphatidic acid, diacylglycerol kinases (DGKs) act as terminator of diacylglycerol signalling. This study investigates the role of DGK in the development of hepatocyte IP. DGK activity and cell viability were evaluated in isolated

  13. Transesophageal electrocardiography and adenosine in the diagnosis of wide complex tachycardia.

    PubMed Central

    Lopez, J A; Lufschanowski, R; Massumi, A

    1994-01-01

    The diagnosis of wide complex tachycardia based on surface electrocardiography can be difficult. Misdiagnosis occurs frequently and is commonly associated with increased morbidity and mortality. We describe a case of wide QRS complex tachycardia in which transesophageal electrocardiography and intravenous adenosine were used to obtain a reliable diagnosis. These are safe and readily available tools for elucidating the mechanism of wide complex tachyarrhythmias in hemodynamically stable patients. PMID:8061537

  14. Deamination of adenosines in extracellular RNA spontaneously internalized by human cells.

    PubMed

    Kuligina, Elena V; Vratskih, Oksana V; Semenov, Dmitry V; Matveeva, Vera A; Richter, Vladimir A

    2008-08-01

    Ribonucleic acids circulating in mammalian extracellular fluids as well as RNAs accumulating in culture medium condensed by mammalian cells are internalized by acceptor cells and distributed among cellular compartments. The internalized RNA can be involved in the induction and regulation of cellular processes as guide or signaling molecules. The internalization of RNA may be accompanied by covalent modifications influencing the stability and functionality of this RNA. To analyze nucleotide modifications introduced by human cells in internalized extracellular RNA, 5.8S rRNA of S. cerevisiae was used. It was shown that 5.8S rRNA of S. cerevisiae is captured by human adenocarcinoma MCF-7 cells from culture medium and delivered to cytoplasm and nuclei. Most of the internalized RNA was hydrolyzed to mono- and oligonucleotides. Full-length RNA uptake was detected by RT-PCR in the cytoplasm and in nuclei after the pulse addition of RNA to the culture medium. 5'-Inosine was the only detectable modified nucleotide in the hydrolysate of cell-internalized RNAs. Consequently, extracellular RNAs entering human cells were subjected to partial adenosine deamination. Sequencing of cDNA confirmed that full-length extracellular RNA that accumulated in the nucleus, but not in the cytoplasm, was partially edited by adenosine deaminases. The deamination revealed in nuclear-stored, full-length RNA was site-specific. Adenosines edited in S. cerevisiae 5.8S rRNA are stack-closing A-U pairs A53 and A96, as well as unpaired A44 and A65. Our data emphasize the participation of adenosine deaminases in capturing and intracellular trafficking of internalized RNAs. PMID:18837925

  15. Adenosine induces dephosphorylation of myosin II regulatory light chain in cultured bovine corneal endothelial cells

    Microsoft Academic Search

    S. P. Srinivas; M. Satpathy; P. Gallagher; E. Larivière; W. Van Driessche

    2004-01-01

    Purpose: Dephosphorylation of the myosin II regulatory light chain (MLC) promotes barrier integrity of cellular monolayers through relaxation of the actin cytoskeleton. This study has investigated the influence of adenosine (ADO) on MLC phosphorylation in cultured bovine corneal endothelial cells (BCEC).Methods: MLC phosphorylation was assessed by urea-glycerol gel electrophoresis and immunoblotting. Elevation of cAMP in response to agonists of A2b

  16. The adenosine-triphosphate–sensitive potassium-channel opener pinacidil is effective in blood cardioplegia

    Microsoft Academic Search

    Jennifer S Lawton; Peng-Wie Hsia; Ralph J Damiano

    1998-01-01

    Background. This study was designed to evaluate the adenosine-triphosphate–sensitive potassium channel opener pinacidil as a blood cardioplegic agent.Methods. Using a blood-perfused, parabiotic, Langendorff rabbit model, hearts underwent 30 minutes of normothermic ischemia protected with blood cardioplegia (St. Thomas’ solution [n = 8] or Krebs-Henseleit solution with pinacidil [50 ?mol\\/L, n = 8]) and 30 minutes of reperfusion. Percent recovery of

  17. Ca 2+ -activated K + channels in airway smooth muscle are inhibited by cytoplasmic adenosine triphosphate

    Microsoft Academic Search

    Klaus Groschner; Shai D. Silberberg; Craig H. Gelband; Cornelis van Breemen

    1991-01-01

    Large-conductance Ca2+-activated K+ channels were studied in membranes of cultured rabbit airway smooth muscle cells, using the patch-clamp technique. In cell-attached recordings, channel openings were rare and occurred only at very positive potentials. Bradykinin (10 µM), an agonist which releases Ca2+ from the sarcoplasmic reticulum, transiently increased channel activity. The metabolic blocker 2,4-dinitrophenol (20 µM), which lowers cellular adenosine triphosphate

  18. Glucose Transfer from Adenosine Diphosphate-Glucose to Starch in Preparations of Waxy Seeds

    Microsoft Academic Search

    Oliver E. Nelson; Chia Yin Tsai

    1964-01-01

    Preparation of starch granules from the developing seeds of 17 different waxy mutants of maize all transfer glucose from adenosine diphosphate-glucose to starch at about one-tenth of the rate of similar preparations from seeds of non-waxy maize. The source of most, if not all, of the activity in preparations from waxy mutants is a limited number of enzymatically active starch

  19. Adenosine A 3 receptors promote degranulation of rat mast cells both in vitro and in vivo

    Microsoft Academic Search

    J. J. Reeves; C. A. Jones; M. J. Sheehan; C. J. Vardey; C. J. Whelan

    1997-01-01

    Objective: To investigate the effects of adenosine receptor agonists and antagonists on 5-HT release from rat isolated pleural mast cells and on plasma protein extravasation in the skin of conscious rats.¶In vitro Methods: Rat isolated pleural mast cells were loaded with [14C] 5-HT, sensitised with mouse monoclonal anti-DNP and then challenged with human serum albumin-DNP. DNP-stimulated 5-HT release from mast

  20. Nonenzymatic template-directed synthesis on hairpin oligonucleotides. III - Incorporation of adenosine and uridine residues

    NASA Technical Reports Server (NTRS)

    Wu, Taifeng; Orgel, Leslie E.

    1992-01-01

    Nonenzymatic template-directed incorporation of adenosine and uridine residues into template sequences was obtained using nucleoside-5-prime phosphoro (2-methyl)imidazolides as substrates and hairpin oligonucleotides as templates. The reactions are regiospecific, producing mainly 3-prime-5-prime phosphodiester bonds. Limited synthesis of CA and AC sequences was observed along with some synthesis of the AA sequences on templates containing TG and GT sequences, along wilth some synthesis of the AA sequences on templates containing TT sequences.

  1. Design and evaluation of xanthine based adenosine receptor antagonists: Potential hypoxia targeted immunotherapies

    PubMed Central

    Thomas, Rhiannon; Lee, Joslynn; Chevalier, Vincent; Sadler, Sara; Selesniemi, Kaisa; Hatfield, Stephen; Sitkovsky, Michail; Ondrechen, Mary Jo; Jones, Graham B.

    2015-01-01

    Molecular modeling techniques were applied to the design, synthesis and optimization of a new series of xanthine based adenosine A2A receptor antagonists. The optimized lead compound was converted to a PEG derivative and a functional in vitro bioassay used to confirm efficacy. Additionally, the PEGylated version showed enhanced aqueous solubility and was inert to photoisomerization, a known limitation of existing antagonists of this class. PMID:24126093

  2. Caffeine reduces hypnotic effects of alcohol through adenosine A 2A receptor blockade

    Microsoft Academic Search

    M El Yacoubi; C Ledent; M Parmentier; J Costentin; J.-M Vaugeois

    2003-01-01

    The role of the adenosine A2A receptor in the hypnotic effects of ethanol was assessed in mice. The duration of the loss of righting reflex following acute ethanol administration was shorter for A2A receptor-deficient mice (A2AR KO) than for wild-type mice (A2AR WT), whereas the fall in body temperature was not different between the two phenotypes. In contrast, the duration

  3. Adenosine analogue reduces spinal cord reperfusion injury in a time-dependent fashion

    Microsoft Academic Search

    David C. Cassada; Curtis G. Tribble; Aditya K. Kaza; Steven M. Fiser; Stewart M. Long; Joel Linden; Jayson M. Rieger; Irving L. Kron; John A. Kern

    2001-01-01

    Background. We hypothesized that inflammation during spinal cord reperfusion worsens ischemic injury. ATL-146e, an adenosine A2A agonist with known anti-inflammatory properties, was used to test this hypothesis at varied intervals to determine the time course of reperfusion injury. Methods. Forty rabbits underwent cross-clamping of the infrarenal aorta for 45 minutes. One group (n = 14 animals) received 0.06 ?g\\/kg\\/min systemic

  4. The use of adenosine and adenosine triphosphate testing in the diagnosis, risk stratification and management of patients with syncope: current evidence and future perspectives.

    PubMed

    Fragakis, Nikolaos; Antoniadis, Antonios P; Saviano, Massimo; Vassilikos, Vassilios; Pappone, Carlo

    2015-03-15

    Syncope is a significant source of cardiovascular-related morbidity yet the etiology is frequently obscure and the identification of patients at highest risk is challenging. Adenosine (AD) and adenosine triphosphate (ATP) administrations have been suggested as potentially useful non-invasive tools in the diagnostic workup of patients with neurally-mediated or bradycardia-related syncope. It has been postulated that both compounds by modulating the autonomic innervation in the heart and exerting negative chronotropic and dromotropic effects in the conduction system, may unmask the mechanism of syncope. However, the clinical implications derived from the efficacy of both tests in the investigation of syncope remain unclear mainly due to inconclusive and occasionally contradictory results of published studies. This review article summarizes recent and past information in the use of ATP and AD in the investigation of syncope with emphasis on clinical trials. We present the current level of evidence for the use of these agents in clinical practice, identify areas where further research is warranted and highlight the future perspectives of these agents as complements to an accurate risk-stratification of patients with syncope. PMID:25725201

  5. G Protein-Coupled Receptors and Adipogenesis: A Focus on Adenosine Receptors

    PubMed Central

    EISENSTEIN, ANNA; RAVID, KATYA

    2014-01-01

    G-protein coupled receptors (GPCRs) are a large family of proteins that coordinate extracellular signals to produce physiologic outcomes. Adenosine receptors (AR) are one class of GPCRs that have been shown to regulate functions as diverse as inflammation, blood flow, and cellular differentiation. Adenosine signals through four GPCRs that either inhibit (A1AR and A3AR) or activate (A2aAR and A2bAR) adenylyl cyclase. This review will focus on the role of GPCRs, and in particular, adenosine receptors, in adipogenesis. Preadipocytes differentiate to mature adipocytes as the adipose tissue expands to compensate for the consumption of excess nutrients. These newly generated adipocytes contribute to maintaining metabolic homeostasis. Understanding the key drivers of this differentiation process can aid the development of therapeutics to combat the growing obesity epidemic and associated metabolic consequences. Although much literature has covered the transcriptional events that culminate in the formation of an adipocyte, less focus has been on receptor-mediated extracellular signals that direct this process. This review will highlight GPCRs and their downstream messengers as significant players controlling adipocyte differentiation. PMID:24114647

  6. Impaired adenosine-mediated angiogenesis in preeclampsia: potential implications for fetal programming

    PubMed Central

    Escudero, Carlos; Roberts, James M.; Myatt, Leslie; Feoktistov, Igor

    2014-01-01

    Preeclampsia is a pregnancy-specific syndrome, defined by such clinical hallmarks as the onset of maternal hypertension and proteinuria after 20 weeks of gestation. The syndrome is also characterized by impaired blood flow through the utero-placental circulation and relative placental ischemia, which in turn, may generate feto-placental endothelial dysfunction. Endothelial dysfunction in offspring born from preeclamptic pregnancies has been associated with an increased risk of cardiovascular disease, including hypertension, later in life. Interestingly, diminished endothelial function, manifested by low angiogenic capacity, leads to hypertension in animal studies. Recently, we have shown that the adenosine receptor A2A/nitric oxide/vascular endothelial growth factor axis is reduced in human umbilical vein endothelial cells derived from preeclamptic pregnancies, an effect correlated with gestational age at onset of preeclampsia. We and others suggested that impaired vascular function might be associated with high cardiovascular risk in offspring exposed to pregnancy diseases. However, we are not aware of any studies that examine impaired adenosine-mediated angiogenesis as a possible link to hypertension in offspring born from preeclamptic pregnancies. In this review, we present evidence supporting the hypothesis that reduced adenosine-mediated angiogenesis during preeclamptic pregnancies might be associated with development of hypertension in the offspring. PMID:24926270

  7. A Fragment-Based Approach to Probing Adenosine Recognition Sites by Using Dynamic Combinatorial Chemistry

    PubMed Central

    Scott, Duncan E.; Dawes, Gwen J.; Ando, Michiyo; Abell, Chris; Ciulli, Alessio

    2015-01-01

    A new strategy that combines the concepts of fragment-based drug design and dynamic combinatorial chemistry (DCC) for targeting adenosine recognition sites on enzymes is reported. We demonstrate the use of 5?-deoxy-5?-thioadenosine as a noncovalent anchor fragment in dynamic combinatorial libraries templated by Mycobacterium tuberculosis pantothenate synthetase. A benzyl disulfide derivative was identified upon library analysis by HPLC. Structural and binding studies of protein–ligand complexes by X-ray crystallography and isothermal titration calorimetry informed the subsequent optimisation of the DCC hit into a disulfide containing the novel meta-nitrobenzyl fragment that targets the pantoate binding site of pantothenate synthetase. Given the prevalence of adenosine-recognition motifs in enzymes, our results provide a proof-of-concept for using this strategy to probe adjacent pockets for a range of adenosine binding enzymes, including other related adenylate-forming ligases, kinases, and ATPases, as well as NAD(P)(H), CoA and FAD(H2) binding proteins. PMID:19827080

  8. History and Perspectives of A2A Adenosine Receptor Antagonists as Potential Therapeutic Agents.

    PubMed

    Preti, Delia; Baraldi, Pier Giovanni; Moorman, Allan R; Borea, Pier Andrea; Varani, Katia

    2015-07-01

    Growing evidence emphasizes that the purine nucleoside adenosine plays an active role as a local regulator in different pathologies. Adenosine is a ubiquitous nucleoside involved in various physiological and pathological functions by stimulating A1 , A2A , A2B , and A3 adenosine receptors (ARs). At the present time, the role of A2A ARs is well known in physiological conditions and in a variety of pathologies, including inflammatory tissue damage and neurodegenerative disorders. In particular, the use of selective A2A antagonists has been reported to be potentially useful in the treatment of Parkinson's disease (PD). In this review, A2A AR signal transduction pathways, together with an analysis of the structure-activity relationships of A2A antagonists, and their corresponding pharmacological roles and therapeutic potential have been presented. The initial results from an emerging polypharmacological approach are also analyzed. This approach is based on the optimization of the affinity and/or functional activity of the examined compounds toward multiple targets, such as A1 /A2A ARs and monoamine oxidase-B (MAO-B), both closely implicated in the pathogenesis of PD. PMID:25821194

  9. A Fluorescent Adenosine Analogue as a Substrate for an A-to-I RNA Editing Enzyme.

    PubMed

    Mizrahi, Rena A; Shin, Dongwon; Sinkeldam, Renatus W; Phelps, Kelly J; Fin, Andrea; Tantillo, Dean J; Tor, Yitzhak; Beal, Peter A

    2015-07-20

    Adenosine to inosine RNA editing catalyzed by ADAR enzymes is common in humans, and altered editing is associated with disease. Experiments using substrate RNAs with adenosine analogues at editing sites are useful for defining features of the ADAR reaction mechanism. The reactivity of ADAR2 was evaluated with RNA containing the emissive adenosine analogue thieno[3,4-d]-6-aminopyrimidine ((th) A). This nucleoside was incorporated into a mimic of the glutamate receptor B (GluR B) mRNA R/G editing site. We found that (th) A is recognized by AMV reverse transcriptase as A, and is deaminated rapidly by human ADAR2 to give (th) I. Importantly, ADAR reaction progress can be monitored by following the deamination-induced change in fluorescence of the (th) A-modified RNA. The observed high (th) A reactivity adds to our understanding of the structural features that are necessary for an efficient hADAR2 reaction. Furthermore, the new fluorescent assay is expected to accelerate mechanistic studies of ADARs. PMID:26095193

  10. Adenosine A1 receptor binding activity of methoxy flavonoids from Orthosiphon stamineus.

    PubMed

    Yuliana, Nancy Dewi; Khatib, Alfi; Link-Struensee, Anne Maria; Ijzerman, Adriaan P; Rungkat-Zakaria, Fransiska; Choi, Young Hae; Verpoorte, Robert

    2009-02-01

    Orthosiphon stamineus Benth. ( Orthosiphon Grandiflorus Bold. or Clerodendranthus spicatus Thunb.) is an Indonesian medicinal herb traditionally used for diseases such as hypertension, diabetes, and kidney stones. Despite the importance of this last application, there are very few reports on it. Diuretic action is an important factor in kidney stone treatment, as an increase in the volume of fluid flowing through the kidney will help to dissolve the stones, assist their passing to avoid further retention, and flush out the deposits. Among the diverse roles of adenosine A (1) receptor antagonists in renal protection, many studies have shown that they can induce diuresis and sodium excretion. A bioassay-guided fractionation of a methanol-water extract of Orthosiphon stamineus leaves using the adenosine A (1) receptor binding assay resulted in the isolation of seven methoxy flavonoids as active ligands with K(i) values in the micromolar range. The Hill slope values are not significantly different from unity (within 0.9 - 1.4), which indicates the antagonist effect to A (1)-R. The results of this study thus provide a scientific foundation for the traditional use ofOrthosiphon stamineus in kidney stone treatment, as the affinity of the active compounds isolated from it as adenosine A (1) receptor ligands allows them to be associated with diuretic activity, which is one possible treatment for renal lithiasis. PMID:19137497

  11. Cordycepin Increases Nonrapid Eye Movement Sleep via Adenosine Receptors in Rats.

    PubMed

    Hu, Zhenzhen; Lee, Chung-Il; Shah, Vikash Kumar; Oh, Eun-Hye; Han, Jin-Yi; Bae, Jae-Ryong; Lee, Kinam; Chong, Myong-Soo; Hong, Jin Tae; Oh, Ki-Wan

    2013-01-01

    Cordycepin (3'-deoxyadenosine) is a naturally occurring adenosine analogue and one of the bioactive constituents isolated from Cordyceps militaris/Cordyceps sinensis, species of the fungal genus Cordyceps. It has traditionally been a prized Chinese folk medicine for the human well-being. Because of similarity of chemical structure of adenosine, cordycepin has been focused on the diverse effects of the central nervous systems (CNSs), like sleep regulation. Therefore, this study was undertaken to know whether cordycepin increases the natural sleep in rats, and its effect is mediated by adenosine receptors (ARs). Sleep was recorded using electroencephalogram (EEG) for 4 hours after oral administration of cordycepin in rats. Sleep architecture and EEG power spectra were analyzed. Cordycepin reduced sleep-wake cycles and increased nonrapid eye movement (NREM) sleep. Interestingly, cordycepin increased ? (theta) waves power density during NREM sleep. In addition, the protein levels of AR subtypes (A1, A2A, and A2B) were increased after the administration of cordycepin, especially in the rat hypothalamus which plays an important role in sleep regulation. Therefore, we suggest that cordycepin increases theta waves power density during NREM sleep via nonspecific AR in rats. In addition, this experiment can provide basic evidence that cordycepin may be helpful for sleep-disturbed subjects. PMID:23710239

  12. A continuous spectrophotometric assay for adenosine 5'-phosphosulfate reductase activity with sulfite-selective probes.

    PubMed

    Paritala, Hanumantharao; Carroll, Kate S

    2013-09-01

    Mycobacterium tuberculosis (Mtb) adenosine 5'-phosphosulfate (APS) reductase (APR) catalyzes the first committed step in sulfate reduction for the biosynthesis of essential reduced sulfur-containing biomolecules, such as cysteine, and is essential for survival in the latent phase of tuberculosis (TB) infection. Despite the importance of APR to Mtb and other bacterial pathogens, current assay methods depend on the use of (35)S-labeled APS or shunt adenosine 5'-monophosphate (AMP) to a coupled-enzyme system. Both methods are cumbersome and require the use of expensive reagents. Here, we report the development of a continuous spectrophotometric method for measuring APR activity by using novel sulfite-selective colorimetric or "off-on" fluorescent levulinate-based probes. Thus, the APR activity can be followed by monitoring the increase in absorbance or fluorescence of the resulting phenolate product. Using this assay, we determined Michaelis-Menten kinetic constants (K(m), k(cat), and k(cat)/K(m)) and the apparent inhibition constant (Ki) for adenosine 5'-diphosphate (ADP), which compared favorably with values obtained in the "gold standard" radioactive assay. The newly developed assay is robust and easy to perform with a simple spectrophotometer. PMID:23711725

  13. [Extraction and ultra-performance liquid chromatographic analysis of adenosine phosphates in royal jelly].

    PubMed

    Chen, Lanzhen; Li, Guifen; Xue, Xiaofeng; Wu, Liming; Zhao, Jing; Huang, Jingping; Yuan, Hancheng

    2008-11-01

    Several different extraction procedures including perchloric acid extraction, boiling water extraction and boiling magnesium sulfate solution extraction were studied for the extraction of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) from the royal jelly. Among these methods, the extraction with 5% perchloric acid at below 4 degrees C was the optimum extraction method. A simple, fast and sensitive ultra-performance liquid chromatographic (UPLC) method was developed for the determination of ATP, ADP and AMP in royal jelly. The separation was achieved within 4 min using a BEH Shield RP18 column (100 mm x 2.1 mm, 1.7 microm) with 50 mmol/L monoammonium phosphate solution (pH 6.5) and acetonitrile as the mobile phase. The spiked recoveries of ATP, ADP and AMP were 84.1% -94.3%, 86.2% -93.7% and 91.0% -104.3%, respectively. The relative standard deviations were less than 10%. This method was successfully applied to the analysis of some royal jelly samples from beekeepers and markets for the investigation of distribution of ATP, ADP and AMP in royal jelly samples. PMID:19253554

  14. Adenosine A(3) receptor agonist acts as a homeostatic regulator of bone marrow hematopoiesis.

    PubMed

    Hofer, Michal; Pospísil, Milan; Znojil, Vladimír; Holá, Jirina; Vacek, Antonín; Streitová, Denisa

    2007-07-01

    The present study was performed to define the optimum conditions of the stimulatory action of the adenosine A(3) receptor agonist, N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA), on bone marrow hematopoiesis in mice. Effects of 2-day treatment with IB-MECA given at single doses of 200nmol/kg twice daily were investigated in normal mice and in mice whose femoral bone marrow cells were either depleted or regenerating after pretreatment with the cytotoxic drug 5-fluorouracil. Morphological criteria were used to determine the proliferation state of the granulocytic and erythroid cell systems. Significant negative correlation between the control proliferation state and the increase of cell proliferation after IB-MECA treatment irrespective of the cell lineage investigated was found. The results suggest the homeostatic character of the induced stimulatory effects and the need to respect the functional state of the target tissue when investigating effects of adenosine receptor agonists under in vivo conditions. PMID:17383145

  15. Methotrexate enhances the anti-inflammatory effect of CF101 via up-regulation of the A3 adenosine receptor expression

    Microsoft Academic Search

    Avivit Ochaion; Sara Bar-Yehuda; Shira Cohn; Luis Del Valle; Georginia Perez-Liz; Lea Madi; Faina Barer; Motti Farbstein; Sari Fishman-Furman; Tatiana Reitblat; Alexander Reitblat; Howard Amital; Yair Levi; Yair Molad; Reuven Mader; Moshe Tishler; Pnina Langevitz; Alexander Zabutti; Pnina Fishman

    2006-01-01

    Methotrexate (MTX) exerts an anti-inflammatory effect via its metabolite adenosine, which activates adenosine receptors. The A3 adenosine receptor (A3AR) was found to be highly expressed in inflammatory tissues and peripheral blood mononuclear cells (PBMCs) of rats with adjuvant-induced arthritis (AIA). CF101 (IB-MECA), an A3AR agonist, was previously found to inhibit the clinical and pathological manifestations of AIA. The aim of

  16. Involvement of K+ Channels in the Inhibitory Effects of Adenosine on Anoxia-Induced [Ca2+ ]i Increase in Cultured Rat Hippocampal CA1 Neurons

    Microsoft Academic Search

    Qin Wan; Hang Yao; Fu-Zhuang Wang

    1999-01-01

    Changes in intracellular free Ca2+ concentration ([Ca2+]i) in cultured hippocampal CA1 neurons isolated from newborn rats were measured by a confocal laser scanning microscope, using the Ca2+ indicator Fluo-3. The results showed that exogenous adenosine (100 ?M) significantly attenuated the increase of neuronal [Ca2+]i induced by acute anoxia. This effect of adenosine could be suppressed by the adenosine A1 receptor

  17. Modulation of adenosine transport by insulin in human umbilical artery smooth muscle cells from normal or gestational diabetic pregnancies

    PubMed Central

    Aguayo, Claudio; Flores, Carlos; Parodi, Jorge; Rojas, Romina; Mann, Giovanni E; Pearson, Jeremy D; Sobrevia, Luis

    2001-01-01

    Adenosine transport was measured in human cultured umbilical artery smooth muscle cells, isolated from non-diabetic or gestational diabetic pregnancies, under basal conditions and after pretreatment in vitro with insulin. Adenosine transport in non-diabetic smooth muscle cells was significantly increased by insulin (half-maximal stimulation at 0.33 ± 0.02 nm, 8 h) and characterized by a higher maximal rate (Vmax) for nitrobenzylthioinosine (NBMPR)-sensitive (es) saturable nucleoside transport (17 ± 5 vs. 52 ± 12 pmol (?g protein)?1 min?1, control vs. insulin, respectively) and maximal binding sites (Bmax) for [3H]NBMPR (0.66 ± 0.07 vs. 1.1 ± 0.1 fmol (?g protein)?1, control vs. insulin, respectively), with no significant changes in Michaelis-Menten (Km) and dissociation (Kd) constants. In contrast, in smooth muscle cells from diabetic pregnancies, where the values of Vmax for adenosine transport (59 ± 4 pmol (?g protein)?1 min?1) and Bmax for [3H]NBMPR binding (1.62 ± 0.16 fmol (?g protein)?1) were significantly elevated by comparison with non-diabetic cells, insulin treatment (1 nm, 8 h) reduced the Vmax for adenosine transport and Bmax for [3H]NBMPR binding to levels detected in non-diabetic cells. In non-diabetic cells, the stimulatory effect of insulin on adenosine transport was mimicked by dibutyryl cGMP (100 nm) and reduced by inhibitors of phosphatidylinositol 3-kinase (10 nm wortmannin), nitric oxide synthase (100 ?mNG-nitro-l-arginine methyl ester, l-NAME) or protein synthesis (1 ?m cycloheximide), whereas inhibition of adenylyl cyclase (100 ?m SQ-22536) had no effect. Wortmannin or SQ-22536, but not l-NAME or cycloheximide, attenuated the inhibitory action of insulin on the diabetes-induced stimulation of adenosine transport. Protein levels of inducible NO synthase (iNOS) were similar in non-diabetic and diabetic cells, but were increased by insulin (1 nm, 8 h) only in non-diabetic smooth muscle cells. Our results suggest that adenosine transport via the es nucleoside transporter is modulated differentially by insulin in either cell type. Insulin increased adenosine transport in non-diabetic cells via NO and cGMP, but inhibited the diabetes-elevated adenosine transport via activation of adenylyl cyclase, suggesting that the biological actions of adenosine may be altered under conditions of sustained hyperglycaemia in uncontrolled diabetes. PMID:11433005

  18. Ethanol-induced increase in portal blood flow: Role of acetate and A sub 1 - and A sub 2 -adenosine receptors

    SciTech Connect

    Carmichael, F.J.; Saldivia, V.; Varghese, G.A.; Israel, Y.; Orrego, H. (Addiction Research Foundation Clinical Institute, Toronto, Ontario (Canada) Univ. of Toronto, Ontario (Canada))

    1988-10-01

    The increase in portal blood flow induced by ethanol appears to be adenosine mediated. Acetate, which is released by the liver during ethanol metabolism, is known to increase adenosine levels in tissues and in blood. The effects of acetate on portal blood flow were investigated in rats using the microsphere technique. The intravenous infusion of acetate resulted in vasodilation of the preportal vasculature and in a dose-dependent increase in portal blood flow. This acetate-induced increase in portal blood flow was suppressed by the adenosine receptor blocker, 8-phenyltheophylline. Using the A{sub 1}-adenosine receptor agonist N-6-cyclohexyl adenosine and the A{sub 2}-agonist 5{prime}-N-ethylcarboxamido adenosine, we demonstrate that the effect of adenosine on the preportal vasculature is mediated by the A{sub 2}-subtype of adenosine receptors. In conclusion, these data support the hypothesis that the increase in portal blood flow after ethanol administration results from a preportal vasodilatory effect of adenosine formed from acetate metabolism in extrahepatic tissues.

  19. Adenosine A2 receptors are involved in the activation of ATP-sensitive K+ currents during metabolic inhibition in guinea pig ventricular myocytes.

    PubMed

    Pan, Sheng-Jun; Li, Li-Rong

    2011-03-01

    It has been hypothesized that an interaction among adenosine A(1) receptors, protein kinase C (PKC) activation, and ATP-sensitive potassium channels (K(ATP)) mediates ischemic preconditioning in experiments on different animal species. The purpose of this study was to determine if activation of K(ATP) is functionally coupled to A(1) receptors and (or) PKC activation during metabolic inhibition (MI) in guinea pig ventricular myocytes. Perforated-patch using nystatin and conventional whole-cell recording methods were used to observe the effects of adenosine and adenosine-receptor antagonists on the activation of K(ATP) currents during MI induced by application of 2,4-dinitrophenol (DNP) and 2-deoxyglucose (2DG) without glucose, in the presence or absence of a PKC activator, phorbol 12-myristate 13-acetate (PMA). Adenosine accelerated the time course activation of K(ATP) currents during MI under the intact intracellular condition or dialyzed condition with l mmol/L ATP in the pipette solution. The accelerated effect of adenosine activation of K(ATP) under MI was not reversed by a nonselective Al adenosine receptor antagonist, 8-(p-sulfophenyl)theophylline (SPT), or a specific Al adenosine receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). However, the adenosine A(2) receptor antagonist alloxazine reversed the time course activation of the K(ATP) current under MI. An adenylate cyclase activator, forskolin, did not further abbreviate the time course activation of K(ATP) with or without adenosine. Application of a PKC blocker, chelerythrine, reversed the time course activation of K(ATP) by adenosine under MI. In addition, pretreatment with a PKC activator, PMA, had similar effects to adenosine, while adenosine did not further shorten the time required for activation of K(ATP) currents during MI with PMA pretreatment. There is no direct evidence of activation of K(ATP) currents by adenosine A(1) receptor during metabolic inhibition under our experimental condition. However, adenosine A(2) receptor activation is involved in the K(ATP) channel activation in the guinea pig ventricular myocytes, of which effect is not mediated through the increase in intracellular cAMP. Adenosine seems to interact with PKC activation to open K(ATP) during MI, but a possible link between the adenosine A(2) receptor and PKC activation in this process needs further elucidation. PMID:21423292

  20. The effect of cannabidiol on ischemia/reperfusion-induced ventricular arrhythmias: the role of adenosine A1 receptors.

    PubMed

    Gonca, Ersöz; Dar?c?, Faruk

    2015-01-01

    Cannabidiol (CBD) is a nonpsychoactive phytocannabinoid with anti-inflammatory activity mediated by enhancing adenosine signaling. As the adenosine A1 receptor activation confers protection against ischemia/reperfusion (I/R)-induced ventricular arrhythmias, we hypothesized that CBD may have antiarrhythmic effect through the activation of adenosine A1 receptor. Cannabidiol has recently been shown to suppress ischemia-induced ventricular arrhythmias. We aimed to research the effect of CBD on the incidence and the duration of I/R-induced ventricular arrhythmias and to investigate the role of adenosine A1 receptor activation in the possible antiarrhythmic effect of CBD. Myocardial ischemia and reperfusion was induced in anesthetized male rats by ligating the left anterior descending coronary artery for 6 minutes and by loosening the bond at the coronary artery, respectively. Cannabidiol alone was given in a dose of 50 µg/kg, 10 minutes prior to coronary artery occlusion and coadministrated with adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) in a dose of 100 µg/kg, 15 minutes prior to coronary artery occlusion to investigate whether the antiarrhythmic effect of CBD is modified by the activation of adenosine A1 receptors. The experimental groups were as follows: (1) vehicle control (n = 10), (2) CBD (n = 9), (3) DPCPX (n = 7), and (4) CBD + DPCPX group (n = 7). Cannabidiol treatment significantly decreased the incidence and the duration of ventricular tachycardia, total length of arrhythmias, and the arrhythmia scores compared to control during the reperfusion period. The DPCPX treatment alone did not affect the incidence and the duration of any type of arrhythmias. However, DPCPX aborted the antiarrhythmic effect of CBD when it was combined with it. The present results demonstrated that CBD has an antiarrhythmic effect against I/R-induced arrhythmias, and the antiarrhythmic effect of CBD may be mediated through the activation of adenosine A1 receptor. PMID:24853683

  1. Phorbol esters and adenosine affect the readily releasable neurotransmitter pool by different mechanisms at amphibian motor nerve endings

    PubMed Central

    Searl, T J; Silinsky, E M

    2003-01-01

    Phorbol esters and adenosine have been proposed to interact at common sites downstream of calcium entry at amphibian motor nerve endings. We thus studied the actions and interactions of phorbol esters and adenosine using electrophysiological recording techniques in conjunction with both binomial statistical analysis and high-frequency stimulation at the amphibian neuromuscular junction. To begin this study, we confirmed previous observations that synchronous evoked acetylcholine (ACh) release (reflected as endplate potentials, EPPs) is well described by a simple binomial distribution. We then used binomial analysis to study the effects of the phorbol ester phorbol dibutyrate (PDBu, 100 nm) and adenosine (50 µm) on the binomial parameters n (the number of calcium charged ACh quanta available for release) and p (the average probability of release), where the mean level of evoked ACh release (m) = np. We found that PDBu increased m by increasing the parameter n whilst adenosine reduced m by reducing n; neither agent affected the parameter p. PDBu had no effect on either the potency or efficacy of the inhibition produced by adenosine. Subtle differences between these two agents were revealed by the patterns of EPPs evoked by high-frequency trains of stimuli. Phorbol esters increased ACh release during the early phase of stimulation but not during the subsequent plateau phase. The inhibitory effect of adenosine was maximal at the beginning of the train and was still present with reduced efficacy during the plateau phase. When taken together with previous findings, these present results suggest that phorbol esters increase the immediately available store of synaptic vesicles by increasing the number of primed vesicles whilst adenosine acts at a later stage of the secretory process to decrease the number of calcium-charged primed vesicles. PMID:12972626

  2. Adenosine kinase inhibition protects the kidney against streptozotocin-induced diabetes through anti-inflammatory and anti-oxidant mechanisms.

    PubMed

    Pye, Chelsey; Elsherbiny, Nehal M; Ibrahim, Ahmed S; Liou, Gregory I; Chadli, Ahmed; Al-Shabrawey, Mohamed; Elmarakby, Ahmed A

    2014-07-01

    Adenosine provides anti-inflammatory effects in cardiovascular disease via the activation of adenosine A2A receptors; however, the physiological effect of adenosine could be limited due to its phosphorylation by adenosine kinase. We hypothesized that inhibition of adenosine kinase exacerbates extracellular adenosine levels to reduce renal inflammation and injury in streptozotocin-induced diabetes. Diabetes was induced in male C57BL/6 mice by daily injection of streptozotocin (50mg/kg/day, i.p. for 5 days). Control and diabetic mice were then treated with the adenosine kinase inhibitor ABT702 (1.5mg/kg, i.p. two times a week for 8 weeks, n=7-8/group) or the vehicle (5% DMSO). ABT702 treatment reduced blood glucose level in diabetic mice (?20%; P<0.05). ABT702 also reduced albuminuria and markers of glomerular injury, nephrinuria and podocalyxin excretion levels, in diabetic mice. Renal NADPH oxidase activity and urinary thiobarbituric acid reactive substances (TBARS) excretion, indices of oxidative stress, were also elevated in diabetic mice and ABT702 significantly reduced these changes. ABT702 increased renal endothelial nitric oxide synthase expression (eNOS) and nitrate/nitrite excretion levels in diabetic mice. In addition, the diabetic mice displayed an increase in renal macrophage infiltration, in association with increased renal NF?B activation. Importantly, treatment with ABT702 significantly reduced all these inflammatory parameters (P<0.05). Furthermore, ABT702 decreased glomerular permeability and inflammation and restored the decrease in glomerular occludin expression in vitro in high glucose treated human glomerular endothelial cells. Collectively, the results suggest that the reno-protective effects of ABT702 could be attributed to the reduction in renal inflammation and oxidative stress in diabetic mice. PMID:24841126

  3. Effect of adenosine and its stabile analogue 2-chloroadenosine on cerebrocortical microcirculation and NAD/NADH redox state.

    PubMed

    Dóra, E

    1985-07-01

    In the present study, the effects of topically applied adenosine (ADO) and its stabile analogue 2-chloroadenosine (CADO) on cerebrocortical microcirculation and NAD/NADH redox state (oxidized/reduced nicotinamide adenine dinucleotide) were investigated. Vascular volume (CVV), mean transit time of blood flow (tm), blood flow (CBF), and NADH fluorescence of the cat brain cortex were measured through a cranial window with a microscope fluororeflectometer. The reference values of CVV, tm, and CBF, measured in the artificial cerebrospinal fluid (mock CSF) which superfused brain cortex, were regarded as 100%. Adenosine and 2-chloroadenosine, in the concentration range of 10(-6) - 10(-3) M, resulted in concentration-dependent increases in CBF and NAD reduction. 10(-5) M adenosine and 2-chloroadenosine increased CBF by 49.6 +/- 5.6% and 80.4 +/- 10.3%, respectively. At a pharmacologically high concentration (10(-3) M), ADO increased CBF by 164.6 +/- 13.5%, CADO by 333 +/- 44%. At the same time, 10(-3) M ADO and CADO shifted the cortical NAD/NADH redox state by 7.9 +/- 0.4% and 12.4 +/- 0.7%, respectively toward a more reduced state. Our results, concerning the vasodilator potency of adenosine and 2-chloroadenosine, accord with available data in the literature. However, the pronounced NAD reduction obtained with these adenosine nucleosides suggests that, besides an action on vascular adenosine receptors, some other changes, such as increased substrate mobilization and possibly cAMP production, may contribute to the vasodilator effect of adenosine and 2-chloroadenosine. PMID:4034367

  4. Effects of 2-ethylamino-1,3,4-thiadiazole on hepatic adenosine nucleotides in experimental hemorrhagic shock.

    PubMed

    Abraham, J; Hopkins, R W; Damewood, C A; Simeone, F A

    1980-01-01

    2-Ethylamino-1,3,4-thiadiazole (EAT), originally tested as a cancer chemotherapeutic agent, has been shown to increase the de novo synthesis of purines. To evaluate its effects on hepatic adenosine nucleotides in hemorrhagic shock, EAT was administered to dogs prior to bleeding. Concentrations of uric acid and allantoin in serum and lymph were also measured as additional indices of purine metabolism in the dog. During oligemia, the adenosine triphosphate (ATP) in serial liver biopsies fell to half of the control values in treated and untreated groups. After reinfusion, the APT and total adenosine nucleotides increased in both groups but were significantly higher in treated than in untreated control animals (P less than 0.05). In treated animals the hepatic ATP reached 93% and 109% of initial values at one and three hours after reinfusion, respectively. Corresponding values were 63% and 80% in surviving untreated control animals. During oligemia and after reinfusion, the uric acid was increased in both groups but remained significantly lower in treated than in untreated animals. The arterial pressure of treated animals remained higher after reinfusion than in untreated animals. Studies in oligemic rats demonstrated significantly greater survival in EAT-treated animals than in untreated controls. The data suggest that pretreatment with EAT results in improved recovery of the hepatic adenosine nucleotide pool and increased survival of oligemic animals, which may be related to the greater availability of substrates for synthesis of the adenosine nucleotides. PMID:7226432

  5. Effects of cystamine and cysteamine on the adenosine-triphosphate activity and oxidative phosphorylation of rat-liver mitochondria

    PubMed Central

    Skrede, S.

    1966-01-01

    1. Cystamine (2,2?-diaminodiethyl disulphide) caused an unmasking of mitochondrial adenosine triphosphatase and a leakage of Mg2+ from the mitochondria, and decreased the stimulation of adenosine triphosphatase by 2,4-dinitrophenol. When Mg2+ was added, cystamine potentiated the activation of adenosine triphosphatase by 2,4-dinitrophenol. 2. Cystamine was without effect on the adenosine triphosphatase of disrupted mitochondria. 3. Cystamine was moderately potent as an uncoupling agent and as an inhibitor of the [32P]Pi–ATP exchange reaction. 4. Cysteamine (2-aminoethanethiol) was without the above effects, when special precautions were taken to counteract its autoxidation. 5. The effects of cystamine should probably be ascribed to its disulphide group, since the diamine cadaverine protected slightly against the loss of Mg2+ and the decrease of 2,4-dinitrophenol-stimulated adenosine-triphosphatase activity caused by aging of the mitochondria. It is suggested that cystamine acts by a breakdown of mitochondrial permeability barriers. PMID:4223634

  6. Determination of Serum Adenosine Deaminase and Xanthine Oxidase Levels in Patients with Crimean–Congo Hemorrhagic Fever

    PubMed Central

    Celik, V. Kenan; Sari, Ismail; Engin, Aynur; Yildiz, Gürsel; Aydin, Hüseyin; Bakir, Sevtap

    2010-01-01

    OBJECTIVE: Crimean–Congo hemorrhagic fever is an acute viral hemorrhagic fever with a high mortality rate. Despite increasing knowledge about hemorrhagic fever viruses, little is known about the pathogenesis of Crimean–Congo hemorrhagic fever. In this study, we measured serum adenosine deaminase and xanthine oxidase levels in Crimean–Congo hemorrhagic fever patients. METHODS: Serum adenosine deaminase levels were measured with a sensitive colorimetric method described by Giusti and xanthine oxidase levels by the method of Worthington in 30 consecutive hospitalized patients (mean age 42.6 ± 21.0). Laboratory tests confirmed their diagnoses of Crimean–Congo hemorrhagic fever. Thirty-five subjects (mean age 42.9 ± 19.1) served as the control group. RESULTS: There was a significant difference in adenosine deaminase and xanthine oxidase levels between cases and controls (p<0.05). However, neither adenosine deaminase nor xanthine oxidase levels varied with the severity of disease in the cases assessed (p>0.05). CONCLUSION: Adenosine deaminase and xanthine oxidase levels were increased in patients with Crimean–Congo hemorrhagic fever. Elevated serum xanthine oxidase activity in patients with Crimean–Congo hemorrhagic fever may be associated with reactive oxygen species generated by the xanthine/xanthine oxidase system during inflammatory responses. In addition, elevated lipid peroxidation may contribute to cell damage and hemorrhage. The association of cell damage and hemorrhage with xanthine oxidase activity should be further investigated in large-scale studies. PMID:20668627

  7. Adenylate cyclase from synchronized neuroblastoma cells: responsiveness to prostaglandin E1, adenosine, and dopamine during the cell cycle.

    PubMed

    Pénit, J; Cantau, B; Huot, J; Jard, S

    1977-04-01

    Neuroblastoma cells were synchronized by a combined isoleucine plus glutamine starvation. Adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] was measured under basal conditions and in the presence of dopamine, adenosine and prostaglandin (PG) E1. A clear dissociation occurred between the respective evolution patterns of basal and agonist-stimulated adenylate cyclase activities. The magnitudes of the enzyme response to PGE1, adenosine, and dopamine also exhibited different evolution patterns during the cell cycle. Evolution of adenylate cyclase responsiveness to PGE1 during the cell cycle exhibited striking similarities with the intracellular 3':5'-cyclic AMP changes observed elsewhere. Use of theophylline and fluphenazine as specific inhibitors of adenosine and dopamine, respectively, made it possible to demonstrate that adenosine, dopamine, and PGE1 stimulated adenylate cyclase through independent receptor sites. Furthermore, whatever the stage of the cell cycle, responses to these three agonists were not additive, indicating that the receptors of adenosine, dopamine, and PGE1 control the same adenylate cyclase moieties. The data suggest that adenylate cyclase cell content and enzyme responsiveness to specific agonists can be independently controlled. PMID:266197

  8. Stimulation of central A1 adenosine receptors suppresses seizure and neuropathology in a soman nerve agent seizure rat model.

    PubMed

    Thomas, Thaddeus P; Shih, Tsung-Ming

    2014-09-01

    The current regimen for treating nerve agent poisoning does not sufficiently suppress the excitotoxic activity that causes severe brain damage, especially in cases where treatment is delayed and nerve agent-induced status epilepticus develops. New therapeutic targets are required to improve survivability and minimize neuropathology after irreversible acetylcholinesterase inactivation. Earlier studies have shown that systemic delivery of adenosine agonists decreases nerve agent lethality; however, the mechanism of protection remains to be understood. The primary aim of this study was to investigate the role of central adenosine receptor (AR) stimulation in neuroprotection by directly injecting (6)-cyclopentyladenosine (CPA), an adenosine agonist specific to the A1 receptor subtype (A1R), into the brain intracerebroventricularly (ICV) in a soman seizure rat model. In addition to general A1R stimulation, we hypothesized that bilateral micro-injection of CPA into the cholinergic basal forebrain (BF) could also suppress excitotoxic activity. The results from these studies demonstrated that centrally administered adenosine agonists are anti-seizure and neuroprotective. CPA-delivered ICV prevented seizure and convulsion in 100% of the animals. Moreover, neuropathological evaluation indicated that adenosine treatments reduced brain damage from severe to minimal. Inhibition of the BF via CPA had varied results. Some animals were protected by treatment; however, others displayed similar pathology to the control. Overall, these data suggest that stimulating central ARs could be an effective target for the next generation countermeasures for nerve agent intoxication. PMID:24785252

  9. Effects of propentofylline on adenosine A1 and A2 receptors and nitrobenzylthioinosine-sensitive nucleoside transporters: quantitative autoradiographic analysis.

    PubMed

    Parkinson, F E; Fredholm, B B

    1991-09-24

    Previous studies have demonstrated that the xanthine compound, propentofylline, has beneficial effects in models of cerebral ischemia and can enhance some and exhibit other effects of adenosine. We investigated the in vitro effects of propentofylline and its hydroxy metabolite, A72,0287, on the binding of [3H]cyclohexyladenosine ([3H]CHA), [3H]2-[p-(2-carbonyl-ethyl)-phenylethyl-amino]-5'-N- ethylcarboxamido adenosine ([3H]CGS 21680) and [3H]nitrobenzylthioinosine ([3H]NBMPR) to adenosine A1 and A2 receptors and NBMPR-sensitive nucleoside transporters, respectively, in 10-microns coronal rat brain sections. Both xanthines had micromolar affinity for each of these sites with approximately 10-fold lower affinity for A2 receptors than for A1 receptors and [3H]NBMPR binding sites. Saturation analysis of [3H]CHA or [3H]CGS 21680 binding in the presence of increasing concentrations of propentofylline produced significant increases in KD values without affecting Bmax values; thus propentofylline is a competitive inhibitor at A1 and A2 receptors. The effects on A2 receptors apparently require higher concentrations (Ki approximately 200 microM) than the effects on A1 receptors (Ki approximately 20 microM). Propentofylline was also found to be a competitive inhibitor of [3H]NBMPR binding. Therefore we conclude that propentofylline interacts with adenosine-responsive systems to increase interstitial adenosine concentrations and to selectively inhibit A1 receptors. PMID:1748157

  10. Basal and adenosine receptor-stimulated levels of cAMP are reduced in lymphocytes from alcoholic patients

    SciTech Connect

    Diamond, I.; Wrubel, B.; Estrin, W.; Gordon, A.

    1987-03-01

    Alcoholism causes serious neurologic disease that may be due, in part, to the ability of ethanol to interact with neural cell membranes and change neuronal function. Adenosine receptors are membrane-bound proteins that appear to mediate some of the effects of ethanol in the brain. Human lymphocytes also have adenosine receptors, and their activation causes increases in cAMP levels. To test the hypothesis that basal and adenosine receptor-stimulated cAMP levels in lymphocytes might be abnormal in alcoholism, the authors studied lymphocytes from 10 alcoholic subjects, 10 age- and sex-matched normal individuals, and 10 patients with nonalcoholic liver disease. Basal and adenosine receptor-stimulated cAMP levels were reduced 75% in lymphocytes from alcoholic subjects. Also, there was a 76% reduction in ethanol stimulation of cAMP accumulation in lymphocytes from alcoholics. Similar results were demonstrable in isolated T cells. Unlike other laboratory tests examined, these measurements appeared to distinguish alcoholics from normal subjects and from patients with nonalcoholic liver disease. Reduced basal and adenosine receptor-stimulated levels of cAMP in lymphocytes from alcoholics may reflect a change in cell membranes due either to chronic alcohol abuse or to a genetic predisposition unique to alcoholic subjects.

  11. Renal afferent arteriolar and tubuloglomerular feedback reactivity in mice with conditional deletions of adenosine 1 receptors

    PubMed Central

    Li, Lingli; Lai, En Yin; Huang, Yuning; Eisner, Christoph; Mizel, Diane; Wilcox, Christopher S.

    2012-01-01

    Adenosine 1 receptors (A1AR) have been shown in previous experiments to play a major role in the tubuloglomerular feedback (TGF) constrictor response of afferent arterioles (AA) to increased loop of Henle flow. Overexpression studies have pointed to a critical role of vascular A1AR, but it has remained unclear whether selective deletion of A1AR from smooth muscle cells is sufficient to abolish TGF responsiveness. To address this question, we have determined TGF response magnitude in mice in which vascular A1AR deletion was achieved using the loxP recombination approach with cre recombinase being controlled by a smooth muscle actin promoter (SmCre/A1ARff). Effective vascular deletion of A1AR was affirmed by absence of vasoconstrictor responses to adenosine or cyclohexyl adenosine (CHA) in microperfused AA. Elevation of loop of Henle flow from 0 to 30 nl/min caused a 22.1 ± 3.1% reduction of stop flow pressure in control mice and of 7.2 ± 1.5% in SmCre/A1ARff mice (P < 0.001). Maintenance of residual TGF activity despite absence of A1AR-mediated responses in AA suggests participation of extravascular A1AR in TGF. Support for this notion comes from the observation that deletion of A1ARff by nestin-driven cre causes an identical TGF response reduction (7.3 ± 2.4% in NestinCre/A1ARff vs. 20.3 ± 2.7% in controls), whereas AA responsiveness was reduced but not abolished. A1AR on AA smooth muscle cells are primarily responsible for TGF activation, but A1AR on extravascular cells, perhaps mesangial cells, appear to contribute to the TGF response. PMID:22896040

  12. The Quintiles Prize Lecture 2004: The identification of the adenosine A2B receptor as a novel therapeutic target in asthma

    PubMed Central

    Holgate, Stephen T

    2005-01-01

    Adenosine is a powerful bronchoconstrictor of asthmatic, but not normal, airways. In vitro studies on isolated human mast cells and basophils revealed that adenosine and selective analogues augmented inflammatory mediator release from mast cells by stimulating A2 receptors. Pharmacological blockade of mast cell mediator release in vivo also attenuated adenosine-induced bronchoconstriction, as did theophylline, by adenosine A2 receptor antagonism. Further in vitro studies revealed that the asthmatic response to adenosine is likely to be mediated via the A2B subtype which is selectively antagonised by enprofylline. Studies in animal models, especially mice, have shown a close synergistic interaction between adenosine, Th2 and airway remodelling responses. The recent description of A2B receptors on human airway smooth muscle cells that mediate cytokine and chemokine release and induce differentiation of fibroblasts into myofibroblasts strengthens the view that adenosine maybe more than an inflammatory mediator in asthma but also participates in airway wall remodelling in this disease. These data have provided a firm basis for developing adenosine A2B receptor antagonists as a new therapeutic approach to this disease. PMID:15980878

  13. Minoxidil-Induced Hair Growth is Mediated by Adenosine in Cultured Dermal Papilla Cells: Possible Involvement of Sulfonylurea Receptor 2B as a Target of Minoxidil

    Microsoft Academic Search

    Ming Li; Azusa Marubayashi; Yutaka Nakaya; Kiyoshi Fukui; Seiji Arase

    2001-01-01

    The mechanism by which minoxidil, an adenosine-triphosphate-sensitive potassium channel opener, induces hypertrichosis remains to be elucidated. Minoxidil has been reported to stimulate the production of vascular endothelial growth factor, a possible promoter of hair growth, in cultured dermal papilla cells. The mechanism of production of vascular endothelial growth factor remains unclear, however. We hypothesize that adenosine serves as a mediator

  14. The Quintiles Prize Lecture 2004. The identification of the adenosine A2B receptor as a novel therapeutic target in asthma.

    PubMed

    Holgate, Stephen T

    2005-08-01

    Adenosine is a powerful bronchoconstrictor of asthmatic, but not normal, airways. In vitro studies on isolated human mast cells and basophils revealed that adenosine and selective analogues augmented inflammatory mediator release from mast cells by stimulating A(2) receptors. Pharmacological blockade of mast cell mediator release in vivo also attenuated adenosine-induced bronchoconstriction, as did theophylline, by adenosine A(2) receptor antagonism. Further in vitro studies revealed that the asthmatic response to adenosine is likely to be mediated via the A(2B) subtype which is selectively antagonised by enprofylline. Studies in animal models, especially mice, have shown a close synergistic interaction between adenosine, Th2 and airway remodelling responses. The recent description of A(2B) receptors on human airway smooth muscle cells that mediate cytokine and chemokine release and induce differentiation of fibroblasts into myofibroblasts strengthens the view that adenosine maybe more than an inflammatory mediator in asthma but also participates in airway wall remodelling in this disease. These data have provided a firm basis for developing adenosine A(2B) receptor antagonists as a new therapeutic approach to this disease. PMID:15980878

  15. Measuring the dynamics of cyclic adenosine monophosphate level in living cells induced by low-level laser irradiation using bioluminescence resonance energy transfer.

    PubMed

    Huang, Yimei; Zheng, Liqin; Yang, Hongqin; Chen, Jiangxu; Wang, Yuhua; Li, Hui; Xie, Shusen; Zeng, Haishan

    2015-05-01

    Several studies demonstrated that the cyclic adenosine monophosphate (cAMP), an important second messenger, is involved in the mechanism of low-level laser irradiation (LLLI) treatment. However, most of these studies obtained the cAMP level in cell culture extracts or supernatant. In this study, the cAMP level in living cells was measured with bioluminescence resonance energy transfer (BRET). The effect of LLLI on cAMP level in living cells with adenosine receptors blocked was explored to identify the role of adenosine receptors in LLLI. The results showed that LLLI increased the cAMP level. Moreover, the rise of cAMP level was light dose dependent but wavelength independent for 658-, 785-, and 830-nm laser light. The results also exhibited that the adenosine receptors, a class of G protein-coupled receptor (GPCR), modulated the increase of cAMP level induced by LLLI. The cAMP level increased more significantly when the A3 adenosine receptors (A3R) were blocked by A3R antagonist compared with A1 adenosine receptor or A2a adenosine receptor blocked in HEK293T cells after LLLI, which was in good agreement with the adenosine receptors’ expressions. All these results suggested that measuring the cAMP level with BRET could be a useful technique to study the role of GPCRs in living cells under LLLI. PMID:25611980

  16. A new chemical tool (C0036E08) supports the role of adenosine A 2B receptors in mediating human mast cell activation

    Microsoft Academic Search

    Montserrat Buceta; Eduardo Domínguez; Marián Castro; José Brea; David Álvarez; Javier Barcala; Luis Valdés; Pedro Álvarez-Calderón; Fernando Domínguez; Bernat Vidal; Jose Luis Díaz; Montse Miralpeix; Jorge Beleta; María Isabel Cadavid; María Isabel Loza

    2008-01-01

    Asthma is a chronic inflammatory disease of the airways that involves many cell types, amongst which mast cells are known to be important. Adenosine, a potent bronchoconstricting agent, exerts its ability to modulate adenosine receptors of mast cells thereby potentiating derived mediator release, histamine being one of the first mediators to be released. The heterogeneity of sources of mast cells

  17. Crystal Structure of Staphylococcus aureus tRNA Adenosine Deaminase TadA in Complex with RNA

    SciTech Connect

    Losey,H.; Ruthenburg, A.; Verdine, G.

    2006-01-01

    Bacterial tRNA adenosine deaminases (TadAs) catalyze the hydrolytic deamination of adenosine to inosine at the wobble position of tRNA(Arg2), a process that enables this single tRNA to recognize three different arginine codons in mRNA. In addition, inosine is also introduced at the wobble position of multiple eukaryotic tRNAs. The genes encoding these deaminases are essential in bacteria and yeast, demonstrating the importance of their biological activity. Here we report the crystallization and structure determination to 2.0 A of Staphylococcus aureus TadA bound to the anticodon stem-loop of tRNA(Arg2) bearing nebularine, a non-hydrolyzable adenosine analog, at the wobble position. The cocrystal structure reveals the basis for both sequence and structure specificity in the interactions of TadA with RNA, and it additionally provides insight into the active site architecture that promotes efficient hydrolytic deamination.

  18. Non-linear quantitative structure-activity relationship for adenine derivatives as competitive inhibitors of adenosine deaminase

    SciTech Connect

    Sadat Hayatshahi, Sayyed Hamed [Department of Biophysics, Faculty of Science, Tarbiat Modares University, P.O. Box: 14115/175, Tehran (Iran, Islamic Republic of) ; Abdolmaleki, Parviz [Department of Biophysics, Faculty of Science, Tarbiat Modares University, P.O. Box: 14115/175, Tehran (Iran, Islamic Republic of) ]. E-mail: parviz@modares.ac.ir; Safarian, Shahrokh [Department of Biology, Faculty of Science, Tehran University, P.O. Box: 13155-6455, Tehran (Iran, Islamic Republic of) ; Khajeh, Khosro [Department of Biochemistry, Faculty of Science, Tarbiat Modares University, P.O. Box: 14115/175, Tehran (Iran, Islamic Republic of)

    2005-12-16

    Logistic regression and artificial neural networks have been developed as two non-linear models to establish quantitative structure-activity relationships between structural descriptors and biochemical activity of adenosine based competitive inhibitors, toward adenosine deaminase. The training set included 24 compounds with known k {sub i} values. The models were trained to solve two-class problems. Unlike the previous work in which multiple linear regression was used, the highest of positive charge on the molecules was recognized to be in close relation with their inhibition activity, while the electric charge on atom N1 of adenosine was found to be a poor descriptor. Consequently, the previously developed equation was improved and the newly formed one could predict the class of 91.66% of compounds correctly. Also optimized 2-3-1 and 3-4-1 neural networks could increase this rate to 95.83%.

  19. Adenosine 3', 5'-cyclic monophosphate levels in Thermomonospora curvata during cellulase biosynthesis

    Microsoft Academic Search

    George Fennington; Debbie Neubauer; Fred Stutzenberger

    1983-01-01

    The enzymatic degradation of cellulose requires the synergistic activity of at least three enzymes: exo-beta-1,4-glucanase (EC3.2.1.91), endo-beta-1,4-glucanase (EC3.2.1.4), and beta-glucosidase (EC3.2.1.21). Despite extensive studies on a variety of cellulolytic bacteria and fungi, the mechanism(s) regulating the biosynthesis of this inducible catabolic enzyme complex remains unknown. The intracellular concentrations of cyclic nucleotides such as adenosine 3',5'-cyclic monophosphate (cAMP) have been shown

  20. Identification of adenosine functional groups involved in substrate binding by the ribonuclease P ribozyme.

    PubMed

    Siew, D; Zahler, N H; Cassano, A G; Strobel, S A; Harris, M E

    1999-02-01

    The RNA component of bacterial ribonuclease P (RNase P) binds to substrate pre-tRNAs with high affinity and catalyzes site-specific phosphodiester bond hydrolysis to generate the mature tRNA 5' end. Herein we describe the use of biotinylated pre-tRNA substrates to isolate RNase P ribozyme-substrate complexes for nucleotide analogue interference mapping of ribozyme base functional groups involved in substrate recognition. By using a series of adenosine base analogues tagged with phosphorothioate substitutions, we identify specific chemical groups involved in substrate binding. Only 10 adenosines in the Escherichia coli ribozyme show significant sensitivity to interference: A65, A66, A136, A232-234, A248, A249, A334, and A347. Most of these adenosine positions are universally conserved among all bacterial RNase P RNAs; however, not all conserved adenosines are sensitive to analogue substitution. Importantly, all but one of the sensitive nucleotides are located at positions of intermolecular cross-linking between the ribozyme and the substrate. One site of interference that did not correlate with available structural data involved A136 in J11/12. To confirm the generality of the results, we repeated the interference analysis of J11/12 in the Bacillus subtilis RNase P ribozyme, which differs significantly in overall secondary structure. Notably, the B. subtilis ribozyme shows an identical interference pattern at the position (A191) that is homologous to A136. Furthermore, mutation of A136 in the E. coli ribozyme gives rise to a measurable increase in the equilibrium binding constant for the ribozyme-substrate interaction, while mutation of a nearby conserved nucleotide (A132) that is not sensitive to analogue incorporation does not. These results strongly support direct participation of nucleotides in the P4, P11, J5/15, and J18/2 regions of ribozyme structure in pre-tRNA binding and implicate an additional region, J11/12, as involved in substrate recognition. In aggregate, the interference results provide a detailed chemical picture of how the conserved nucleotides adjacent to the pre-tRNA substrate contribute to substrate binding and provide a framework for subsequent identification of the specific roles of these chemical groups in substrate recognition. PMID:10026268

  1. Total Synthesis of a Cyclic Adenosine 5?-Diphosphate Ribose Receptor Agonist

    PubMed Central

    2012-01-01

    Stable cyclic adenosine 5?-diphosphate ribose (cADPR) analogues are chemical biology tools that can probe the Ca2+ release mechanism and structure–activity relationships of this emerging potent second messenger. However, analogues with an intact “northern” ribose have been inaccessible due to the difficulty of generating the sensitive N1-ribosyl link. We report the first total synthesis of the membrane permeant, hydrolytically stable, cADPR receptor agonist 8-Br-N1-cIDPR via regio- and stereoselective N1-ribosylation of protected 8-bromoinosine. PMID:22283398

  2. Strategies for the Use of Poly(adenosine diphosphate ribose) Polymerase (PARP) Inhibitors in Cancer Therapy

    PubMed Central

    Ström, Cecilia E.; Helleday, Thomas

    2012-01-01

    Treatments with Poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors have offered patients carrying cancers with mutated BRCA1 or BRCA2 genes a new and in many cases effective option for disease control. There is potentially a large patient population that may also benefit from PARP inhibitor treatment, either in monotherapy or in combination with chemotherapy. Here, we describe the multifaceted role of PARP inhibitors and discuss which treatment options could potentially be useful to gain disease control without potentiating side effects. PMID:24970153

  3. Strategies for the Use of Poly(adenosine diphosphate ribose) Polymerase (PARP) Inhibitors in Cancer Therapy.

    PubMed

    Ström, Cecilia E; Helleday, Thomas

    2012-01-01

    Treatments with Poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors have offered patients carrying cancers with mutated BRCA1 or BRCA2 genes a new and in many cases effective option for disease control. There is potentially a large patient population that may also benefit from PARP inhibitor treatment, either in monotherapy or in combination with chemotherapy. Here, we describe the multifaceted role of PARP inhibitors and discuss which treatment options could potentially be useful to gain disease control without potentiating side effects. PMID:24970153

  4. Photo protection of RNA building blocks: Adenosine 5?-monophosphate, cytidine 5?-monophosphate and cytosine

    NASA Astrophysics Data System (ADS)

    Nielsen, Jakob Brun; Thøgersen, Jan; Jensen, Svend Knak; Keiding, Søren Rud

    2013-04-01

    Photoprotection of the RNA nucleotides adenosine 5'-monophosphate and cytidine 5'-monophosphate, and the nucleobase cytosine was studied using UV pump, IR probe femtosecond transient absorption spectroscopy. The excitation energy is contained in the aromatic ring system, protecting the RNA backbone. All three molecules dissipate the excitation energy by internal conversion and subsequent vibrational relaxation to the electronic ground state in less than 10 ps. In addition, a second deactivation channel is found in cytidine 5'-monophosphate, illustrated by a signal at 1563 cm-1 with a lifetime of 33 ps assigned to an n?? state in agreement with observations in the UV region.

  5. Selective regulation of nuclear orphan receptors 4A by adenosine receptor subtypes in human mast cells

    PubMed Central

    Zhang, Li; Paine, Catherine

    2010-01-01

    Nuclear orphan receptors 4A (NR4A) are early responsive genes that belong to the superfamily of hormone receptors and comprise NR4A1, NR4A2 and NR4A3. They have been associated to transcriptional activation of multiple genes involved in inflammation, apoptosis and cell cycle control. Here, we establish a link between NR4As and adenosine, a paradoxical inflammatory molecule that can contribute to persistence of inflammation or mediate inflammatory shutdown. Transcriptomics screening of the human mast cell-line HMC-1 revealed a sharp induction of transcriptionally active NR4A2 and NR4A3 by the adenosine analogue NECA. The concomitant treatment of NECA and the adenosine receptor A2A (A2AAR) selective antagonist SCH-58261 exaggerated this effect, suggesting that upregulation of these factors in mast cells is mediated by other AR subtypes (A2B and A3) and that A2AAR activation counteracts NR4A2 and NR4A3 induction. In agreement with this, A2AAR-silencing amplified NR4A induction by NECA. Interestingly, a similar A2AAR modulatory effect was observed on ERK1/2 phosphorylation because A2AAR blockage exacerbated NECA-mediated phosphorylation of ERK1/2. In addition, PKC or MEK1/2 inhibition prevented ERK1/2 phosphorylation and antagonized AR-mediated induction of NR4A2 and NR4A3, suggesting the involvement of these kinases in AR to NR4A signaling. Finally, we observed that selective A2AAR activation with CGS-21680 blocked PMA-induced ERK1/2 phosphorylation and modulated the overexpression of functional nuclear orphan receptors 4A. Taken together, these results establish a novel PKC/ERK/nuclear orphan receptors 4A axis for adenosinergic signaling in mast cells, which can be modulated by A2AAR activation, not only in the context of adenosine but of other mast cell activating stimuli as well. PMID:21234122

  6. Stimulation of the adenosine A3 receptor reverses vascular hyporeactivity after hemorrhagic shock in rats

    Microsoft Academic Search

    Rong Zhou; Feng Chen; Qiang Li; De-yao Hu; Liang-ming Liu

    2010-01-01

    Aim:To investigate whether adenosine A3 receptors (A3AR) stimulation restore vascular reactivity after hemorrhagic shock through a ryanodine receptor (RyR)-mediated and large conductance calcium-activated potassium (BKCa) channel-dependent pathway.Methods:Rat hemorrhagic shock model (40 mmHg) and vascular smooth muscle cell (VSMC) hypoxic model were used. The expression of A3AR was determined by Western blot and RT-PCR. The effect of A3AR stimulation on RyR-mediated

  7. Discovery of LAS101057: A Potent, Selective, and Orally Efficacious A2B Adenosine Receptor Antagonist

    PubMed Central

    2010-01-01

    The structure?activity relationships for a series of pyrazine-based A2B adenosine receptor antagonists are described. From this work, LAS101057 (17), a potent, selective, and orally efficacious A2B receptor antagonist, was identified as a clinical development candidate. LAS101057 inhibits agonist-induced IL-6 production in human fibroblasts and is active in an ovalbumin (OVA)-sensitized mouse model after oral administration, reducing airway hyperresponsiveness to methacholine, Th2 cytokine production, and OVA-specific IgE levels. PMID:24900298

  8. Extraction and quantification of adenosine triphosphate in mammalian tissues and cells.

    PubMed

    Chida, Junji; Kido, Hiroshi

    2014-01-01

    Adenosine 5'-triphosphate (ATP) is the "energy currency" of organisms and plays central roles in bioenergetics, whereby its level is used to evaluate cell viability, proliferation, death, and energy transmission. In this chapter, we describe an improved and efficient method for extraction of ATP from tissues and cells using phenol-based reagents. The chaotropic extraction reagents reported so far co-precipitate ATP with insoluble proteins during extraction and with salts during neutralization. In comparison, the phenol-based reagents extract ATP well without the risks of co-precipitation. The extracted ATP can be quantified by the luciferase assay or high-performance liquid chromatography. PMID:24166365

  9. Overcoming matrix effects in the chemiluminescence determination of extracellular adenosine triphosphate in erythrocyte suspensions.

    PubMed

    Clarke, Andrea; Ouellet, Marc; English, Ann M

    2013-05-15

    As erythrocyte-derived extracellular adenosine triphosphate (ATP) gains recognition as a key vasodilator, its accurate determination is critical. Erythrocytes' high hemoglobin content can act as an inner filter when measuring ATP concentrations by chemiluminescence. We evaluated two approaches to correct for this matrix effect: addition of cell-free hemoglobin to the ATP standards and standard addition of ATP to erythrocyte suspensions. In addition, we reduced sample hematocrit to minimize the absorbance. We conclude that extracellular ATP should be determined in erythrocyte suspensions at 0.06 to 0.004% hematocrit. This gives robust signals without matrix effects and requires only microliters of blood. PMID:23376575

  10. Coronary flow reserve is supranormal in endurance athletes: an adenosine transthoracic echocardiographic study

    PubMed Central

    Hildick-Smith, D; Johnson, P; Wisbey, C; Winter, E; Shapiro, L

    2000-01-01

    OBJECTIVE—To compare coronary flow reserve in endurance athletes and healthy sedentary controls, using adenosine transthoracic echocardiography.?METHODS—29 male endurance athletes (mean (SD) age 27.3 (6.6) years, body mass index (BMI) 22.1 (1.9) kg/m2) and 23 male controls (age 27.2 (6.1) years, BMI 23.9 (2.6) kg/m2) with no coronary risk factors underwent transthoracic echocardiographic assessment of distal left anterior descending coronary artery (LAD) diameter and flow, both at rest and during intravenous adenosine infusion (140 µg/kg/min).?RESULTS—Distal LAD diameter and flow were adequately assessed in 19 controls (83%) and 26 athletes (90%). Distal LAD diameter in athletes (2.04 (0.25) mm) was not significantly greater than in sedentary controls (1.97 (0.27) mm). Per cent increase in LAD diameter following 400 µg sublingual nitrate was greater in the athletes than in the controls, at 14.1 (7.2)% v 8.8 (5.7)% (p < 0.01). Left ventricular mass index in athletes exceeded that of controls, at 130 (19) v 98 (14) g/m2 (p < 0.01). Resting flow among the athletes (10.6 (3.1) ml/min; 4.4 (1.2) ml/min/100 g left ventricular mass) was less than in the controls (14.3 (3.6) ml/min; 8.2 (2.2) ml/min/100 g left ventricular mass) (both p < 0.01). Hyperaemic flow among the athletes (61.9 (17.8) ml/min) exceeded that of the controls (51.1 (14.6) ml/min; p = 0.02), but not when corrected for left ventricular mass (25.9 (5.6) v 28.5 (7.4) ml/min/100 g left ventricular mass; NS). Coronary flow reserve was therefore substantially greater in the athletes than in the controls, at 5.9 (1.0) v 3.7 (0.7) (p < 0.01).?CONCLUSIONS—Coronary flow reserve in endurance athletes is supranormal and endothelium independent vasodilatation is enhanced. Myocardial hypertrophy per se does not necessarily impair coronary flow reserve. Adenosine transthoracic echocardiography is a promising technique for the investigation of coronary flow reserve.???Keywords: coronary flow reserve; athlete; adenosine transthoracic echocardiography PMID:10995406

  11. Uneven distribution of nucleoside transporters and intracellular enzymatic degradation prevent transport of intact [14C] adenosine across the sheep choroid plexus epithelium as a monolayer in primary culture

    PubMed Central

    Redzic, Zoran B; Isakovic, Aleksandra J; Misirlic Dencic, Sonja T; Popadic, Dusan; Segal, Malcolm B

    2006-01-01

    Background Efflux transport of adenosine across the choroid plexus (CP) epithelium might contribute to the homeostasis of this neuromodulator in the extracellular fluids of the brain. The aim of this study was to explore adenosine transport across sheep CP epithelial cell monolayers in primary culture. Methods To explore transport of adenosine across the CP epithelium, we have developed a method for primary culture of the sheep choroid plexus epithelial cells (CPEC) on plastic permeable supports and analysed [14C] adenosine transport across this cellular layer, [14C] adenosine metabolism inside the cells, and cellular uptake of [14C] adenosine from either of the chambers. The primary cell culture consisted of an enriched epithelial cell fraction from the sheep fourth ventricle CP and was grown on laminin-precoated filter inserts. Results and conclusion CPEC grew as monolayers forming typical polygonal islands, reaching optical confluence on the third day after the seeding. Transepithelial electrical resistance increased over the time after seeding up to 85 ± 9 ? cm2 at day 8, while permeability towards [14C] sucrose, a marker of paracellular diffusion, simultaneously decreased. These cells expressed some features typical of the CPEC in situ, including three nucleoside transporters at the transcript level that normally mediate adenosine transport across cellular membranes. The estimated permeability of these monolayers towards [14C] adenosine was low and the same order of magnitude as for the markers of paracellular diffusion. However, inhibition of the intracellular enzymes, adenosine kinase and adenosine deaminase, led to a significant increase in transcellular permeability, indicating that intracellular phosphorylation into nucleotides might be a reason for the low transcellular permeability. HPLC analysis with simultaneous detection of radioactivity revealed that [14C] radioactivity which appeared in the acceptor chamber after the incubation of CPEC monolayers with [14C] adenosine in the donor chamber was mostly present as [14C] hypoxanthine, a product of adenosine metabolic degradation. Therefore, it appears that CPEC in primary cultures act as an enzymatic barrier towards adenosine. Cellular uptake studies revealed that concentrative uptake of [14C] adenosine was confined only to the side of these cells facing the upper or apical chamber, indicating uneven distribution of nucleoside transporters. PMID:16571111

  12. Adenosine, a hepato-protective component in active hexose correlated compound: its identification and iNOS suppression mechanism.

    PubMed

    Tanaka, Yoshito; Ohashi, Satomi; Ohtsuki, Aya; Kiyono, Tamami; Park, Eun Young; Nakamura, Yasushi; Sato, Kenji; Oishi, Masaharu; Miki, Hirokazu; Tokuhara, Katsuji; Matsui, Kosuke; Kaibori, Masaki; Nishizawa, Mikio; Okumura, Tadayoshi; Kwon, A-Hon

    2014-08-31

    Supplementation of active hexose correlated compound (AHCC) improved the prognosis of postoperative hepatocellular carcinoma patients. Excess production of nitric oxide (NO) by inducible NO synthase (iNOS) is an inflammatory biomarker in liver injury. AHCC suppressed iNOS induction in hepatocytes, suggesting that AHCC has a potential liver-protective effect. However, the active component in AHCC responsible for NO suppressive activities has not been identified. The objective of this study was to identify this NO suppressive component and to investigate its mechanisms of action. AHCC was subjected to fractionation by cation exchanger, size exclusion chromatography, and normal- and reversed-phase HPLC. Aliquots of the fractions were added to primary cultured rat hepatocytes stimulated with interleukin (IL)-1?, and NO production was assayed. By activity-guided fractionation and electron spray ionization mass spectrometry analysis, adenosine was identified as one of the NO suppressive components in AHCC. Adenosine inhibited NO production, and reduced the expression of iNOS protein and mRNA. It had no effects on I?B degradation, but it inhibited NF-?B activation. Adenosine also inhibited the upregulation of type I IL-1 receptor (IL-1RI). Experiments with iNOS promoter-luciferase constructs revealed that adenosine decreased the levels of iNOS mRNA at the promoter transactivation and mRNA stabilization steps. Adenosine decreased the expression of the iNOS gene antisense transcript, which is involved in iNOS mRNA stability. Adenosine in AHCC suppressed iNOS induction by blocking NF-?B activation and the upregulation of the IL-1RI pathways, resulting in the inhibition of NO production. PMID:24878381

  13. Spinal noradrenergic activation mediates allodynia reduction from an allosteric adenosine modulator in a rat model of neuropathic pain.

    PubMed

    Li, Xinhui; Conklin, Dawn; Ma, Weiya; Zhu, Xiaoying; Eisenach, James C

    2002-05-01

    Activation of adenosine A1 receptors by endogenous adenosine or synthetic agonists produces anti-nociception in animal models of acute pain and also reduces hypersensitivity in models of inflammatory and nerve-injury pain. Allosteric adenosine modulators facilitate adenosine agonist binding to the A1 receptor. The purpose of the current study was to examine the effect, mechanisms of action, and interaction with noradrenergic systems of intrathecal (i.t.) or oral administration of the allosteric adenosine modulator T62 in a rat model of neuropathic pain. A spinal nerve ligation rat model (SNL; ligation of left L5 and L6 spinal nerve roots) was used. One week after SNL surgery, an i.t. catheter was inserted. Withdrawal threshold to mechanical stimulation of the left hind paw was determined before and after surgery, confirming mechanical hypersensitivity. Oral or i.t. T62 reduced hypersensitivity induced by SNL. The effects of i.t. T62 were inhibited by i.t. injection of an A1 receptor antagonist and by an 2-adrenergic antagonist but not by an A2 adenosine receptor antagonist. Anti-dopamine hydroxylase (DH)-saporin treatment reduce spinal norepinephrine content by 97%, accompanied by an almost complete loss of DH immunoreactive axons in the spinal dorsal horn and neurons in the locus coeruleus. The effect of T62 was completely lost in animals treated with anti-DH-saporin. These data support the hypothesis that activation of the A1 receptor by the allosteric modulator, T62, produces anti-nociception via spinal noradrenergic activation. PMID:12031785

  14. Decreased extracellular adenosine levels lead to loss of hypoxia-induced neuroprotection after repeated episodes of exposure to hypoxia.

    PubMed

    Cui, Mei; Bai, Xue; Li, Tianfu; Chen, Fangzhe; Dong, Qiang; Zhao, Yanxin; Liu, Xueyuan

    2013-01-01

    Achieving a prolonged neuroprotective state following transient ischemic attacks (TIAs) is likely to effectively reduce the brain damage and neurological dysfunction associated with recurrent stroke. HPC is a phenomenon in which advanced exposure to mild hypoxia reduces the stroke volume produced by a subsequent TIA. However, this neuroprotection is not long-lasting, with the effects reaching a peak after 3 days. Therefore, in this study, we investigated the use of multiple episodes of hypoxic exposure at different time intervals to induce longer-term protection in a mouse stroke model. C57BL/6 mice were subjected to different hypoxic preconditioning protocols: a single episode of HPC or five identical episodes at intervals of 3 days (E3d HPC) or 6 days (E6d HPC). Three days after the last hypoxic exposure, temporary middle cerebral artery occlusion (MCAO) was induced. The effects of these HPC protocols on hypoxia-inducible factor (HIF) regulated gene mRNA expression were measured by quantitative PCR. Changes in extracellular adenosine concentrations, known to exert neuroprotective effects, were also measured using in vivo microdialysis and high pressure liquid chromatography (HPLC). Neuroprotection was provided by E6d HPC but not E3d HPC. HIF-regulated target gene expression increased significantly following all HPC protocols. However, E3d HPC significantly decreased extracellular adenosine and reduced cerebral blood flow in the ischemic region with upregulated expression of the adenosine transporter, equilibrative nucleoside transporter 1 (ENT1). An ENT1 inhibitor, propentofylline increased the cerebral blood flow and re-established neuroprotection in E3d HPC. Adenosine receptor specific antagonists showed that adenosine mainly through A1 receptor mediates HPC induced neuroprotection. Our data indicate that cooperation of HIF-regulated genes and extracellular adenosine is necessary for HPC-induced neuroprotection. PMID:23437309

  15. Decreased Extracellular Adenosine Levels Lead to Loss of Hypoxia-Induced Neuroprotection after Repeated Episodes of Exposure to Hypoxia

    PubMed Central

    Li, Tianfu; Chen, Fangzhe; Dong, Qiang; Zhao, Yanxin; Liu, Xueyuan

    2013-01-01

    Achieving a prolonged neuroprotective state following transient ischemic attacks (TIAs) is likely to effectively reduce the brain damage and neurological dysfunction associated with recurrent stroke. HPC is a phenomenon in which advanced exposure to mild hypoxia reduces the stroke volume produced by a subsequent TIA. However, this neuroprotection is not long-lasting, with the effects reaching a peak after 3 days. Therefore, in this study, we investigated the use of multiple episodes of hypoxic exposure at different time intervals to induce longer-term protection in a mouse stroke model. C57BL/6 mice were subjected to different hypoxic preconditioning protocols: a single episode of HPC or five identical episodes at intervals of 3 days (E3d HPC) or 6 days (E6d HPC). Three days after the last hypoxic exposure, temporary middle cerebral artery occlusion (MCAO) was induced. The effects of these HPC protocols on hypoxia-inducible factor (HIF) regulated gene mRNA expression were measured by quantitative PCR. Changes in extracellular adenosine concentrations, known to exert neuroprotective effects, were also measured using in vivo microdialysis and high pressure liquid chromatography (HPLC). Neuroprotection was provided by E6d HPC but not E3d HPC. HIF-regulated target gene expression increased significantly following all HPC protocols. However, E3d HPC significantly decreased extracellular adenosine and reduced cerebral blood flow in the ischemic region with upregulated expression of the adenosine transporter, equilibrative nucleoside transporter 1 (ENT1). An ENT1 inhibitor, propentofylline increased the cerebral blood flow and re-established neuroprotection in E3d HPC. Adenosine receptor specific antagonists showed that adenosine mainly through A1 receptor mediates HPC induced neuroprotection. Our data indicate that cooperation of HIF-regulated genes and extracellular adenosine is necessary for HPC-induced neuroprotection. PMID:23437309

  16. Interaction of mechanisms involving epoxyeicosatrienoic acids, adenosine receptors, and metabotropic glutamate receptors in neurovascular coupling in rat whisker barrel cortex

    PubMed Central

    Shi, Yanrong; Liu, Xiaoguang; Gebremedhin, Debebe; Falck, John R; Harder, David R; Koehler, Raymond C

    2008-01-01

    Adenosine, astrocyte metabotropic glutamate receptors (mGluRs), and epoxyeicosatrienoic acids (EETs) have been implicated in neurovascular coupling. Although A2A and A2B receptors mediate cerebral vasodilation to adenosine, the role of each receptor in the cerebral blood flow (CBF) response to neural activation remains to be fully elucidated. In addition, adenosine can amplify astrocyte calcium, which may increase arachidonic acid metabolites such as EETs. The interaction of these pathways was investigated by determining if combined treatment with antagonists exerted an additive inhibitory effect on the CBF response. During whisker stimulation of anesthetized rats, the increase in cortical CBF was reduced by approximately half after individual administration of A2B, mGluR and EET antagonists and EET synthesis inhibitors. Combining treatment of either a mGluR antagonist, an EET antagonist, or an EET synthesis inhibitor with an A2B receptor antagonist did not produce an additional decrement in the CBF response. Likewise, the CBF response also remained reduced by ~50% when an EET antagonist was combined with an mGluR antagonist or an mGluR antagonist plus an A2B receptor antagonist. In contrast, A2A and A3 receptor antagonists had no effect on the CBF response to whisker stimulation. We conclude that (1) adenosine A2B receptors, rather than A2A or A3 receptors, play a significant role in coupling cortical CBF to neuronal activity, and (2) the adenosine A2B receptor, mGluR, and EETs signaling pathways are not functionally additive, consistent with the possibility of astrocytic mGluR and adenosine A2B receptor linkage to the synthesis and release of vasodilatory EETs. PMID:17519974

  17. The enzymology of adenosine triphosphate sulphurylase from spinach leaf tissue. Kinetic studies and a proposed reaction mechanism

    PubMed Central

    Shaw, W. H.; Anderson, J. W.

    1974-01-01

    1. Sulphate-dependent PPi–ATP exchange, catalysed by purified spinach leaf ATP sulphurylase, was correlated with the concentration of MgATP2? and MgP2O72?; ATP sulphurylase activity was not correlated with the concentration of free Mg2+. 2. Sulphate-dependent PPi–ATP exchange was independent of PPi concentration, but dependent on the concentration of ATP and sulphate. The rate of sulphate-dependent PPi–ATP exchange was quantitatively defined by the rate equation applicable to the initial rate of a bireactant sequential mechanism under steady-state conditions. 3. Chlorate, nitrate and ADP inhibited the exchange reaction. The inhibition by chlorate and nitrate was uncompetitive with respect to ATP and competitive with respect to sulphate. The inhibition by ADP was competitive with respect to ATP and non-competitive with respect to sulphate. 4. ATP sulphurylase catalysed the synthesis of [32P]ATP from [32P]PPi and adenosine 5?-sulphatophosphate in the absence of sulphate; some properties of the reaction are described. Enzyme activity was dependent on the concentration of PPi and adenosine 5?-sulphatophosphate. 5. The synthesis of ATP from PPi and adenosine 5?-sulphatophosphate was inhibited by sulphate and ATP. The inhibition by sulphate was non-competitive with respect to PPi and adenosine 5?-sulphatophosphate; the inhibition by ATP was competitive with respect to adenosine 5?-sulphatophosphate and non-competitive with respect to PPi. It was concluded that the reaction catalysed by spinach leaf ATP sulphurylase was ordered; expressing the order in the forward direction, MgATP2? was the first product to react with the enzyme and MgP2O72? was the first product released. 6. The expected exchange reaction between sulphate and adenosine 5?-sulphatophosphate could not be demonstrated. PMID:4463947

  18. Effect of 2-(6-cyano-1-hexyn-1-yl)adenosine on ocular blood flow in rabbits

    Microsoft Academic Search

    Takashi Konno; Takehiro Uchibori; Akihiko Nagai; Kentaro Kogi; Norimichi Nakahata

    2007-01-01

    Previously, we reported that a relatively selective adenosine A2A receptor agonist 2-(6-cyano-1-hexyn-1-yl)adenosine (2-CN-Ado) elicited ocular hypotension in rabbits (Journal of Pharmacological Sciences 2005;97:501–509). In the present study, we investigated the effect of 2-CN-Ado on ocular blood flow in rabbit eyes. An intravitreal injection of 2-CN-Ado increased ocular blood flow, measured by a non-contact laser flowmeter. 2-CN-Ado-induced increase in ocular blood

  19. Imaging of adenosine A 1 receptors in the human brain by positron emission tomography with [ 11 C]MPDX

    Microsoft Academic Search

    Nobuyoshi Fukumitsu; Kenji Ishii; Yuichi Kimura; Keiichi Oda; Toru Sasaki; Yutaka Mori; Kiichi Ishiwata

    2003-01-01

    We report the first clinical PET study using [1-methyl-11C]8-dicyclopropylmethyl-1-methyl-3-propylxanthine ([11C]MPDX) for imaging adenosine A1 receptors in the human brain. The binding of [11C]MPDX evaluated quantitatively as the distribution volume by a graphical analysis was high in the striatum and thalamus,\\u000a and low in the cerebellum. The distribution pattern of [11C]MPDX was coincident with that of adenosine A1 receptorsin vitro reported

  20. Adenosine can improve the intra-atrial conduction block along the mitral annulus during accessory pathway ablation.

    PubMed

    Yamada, Takumi; Lau, Yung R; McElderry, H Thomas; Doppalapudi, Harish; Kay, G Neal

    2008-03-01

    A 10-year-old boy with a supraventricular tachycardia was referred for catheter ablation. An electrophysiologic study revealed a left lateral concealed accessory pathway (AP). A few radiofrequency (RF) applications targeting the AP resulted in an inadvertent intra-atrial conduction block at the mitral isthmus without any damage to the AP. Adenosine was then administered during left ventricular pacing. Soon after that, the conduction at the mitral isthmus recovered partially, and that change disappeared soon. Those findings suggested that the administration of adenosine may transiently recover the conduction at the mitral isthmus damaged by RF ablation. PMID:18308752

  1. Potentiation by levamisole, methisoprinol, and adenine or adenosine of the inhibitory activity of human interferon against encephalomyocarditis virus.

    PubMed Central

    Muñoz, A; García, R A; Pérez-Aranda, A

    1986-01-01

    The antiviral action of different human interferons against encephalomyocarditis virus in HeLa cell cultures was analyzed. Cell treatment with levamisole (200 micrograms/ml), methisoprinol (1 mg/ml), or adenine or adenosine (33 or 100 micrograms/ml, respectively) potentiated the anti-encephalomyocarditis virus activity of human interferon by 8- to 32-fold. A higher level of potentiation (256-fold) was achieved either by combined treatments with levamisole plus methisoprinol or by treatment with one of these compounds plus adenine or adenosine. Images PMID:2428301

  2. Insulin Restores Gestational Diabetes Mellitus–Reduced Adenosine Transport Involving Differential Expression of Insulin Receptor Isoforms in Human Umbilical Vein Endothelium

    PubMed Central

    Westermeier, Francisco; Salomón, Carlos; González, Marcelo; Puebla, Carlos; Guzmán-Gutiérrez, Enrique; Cifuentes, Fredi; Leiva, Andrea; Casanello, Paola; Sobrevia, Luis

    2011-01-01

    OBJECTIVE To determine whether insulin reverses gestational diabetes mellitus (GDM)–reduced expression and activity of human equilibrative nucleoside transporters 1 (hENT1) in human umbilical vein endothelium cells (HUVECs). RESEARCH DESIGN AND METHODS Primary cultured HUVECs from full-term normal (n = 44) and diet-treated GDM (n = 44) pregnancies were used. Insulin effect was assayed on hENT1 expression (protein, mRNA, SLC29A1 promoter activity) and activity (initial rates of adenosine transport) as well as endothelial nitric oxide (NO) synthase activity (serine1177 phosphorylation, l-citrulline formation). Adenosine concentration in culture medium and umbilical vein blood (high-performance liquid chromatography) as well as insulin receptor A and B expression (quantitative PCR) were determined. Reactivity of umbilical vein rings to adenosine and insulin was assayed by wire myography. Experiments were in the absence or presence of l-NG-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) or ZM-241385 (an A2A-adenosine receptor antagonist). RESULTS Umbilical vein blood adenosine concentration was higher, and the adenosine- and insulin-induced NO/endothelium-dependent umbilical vein relaxation was lower in GDM. Cells from GDM exhibited increased insulin receptor A isoform expression in addition to the reported NO–dependent inhibition of hENT1-adenosine transport and SLC29A1 reporter repression, and increased extracellular concentration of adenosine and NO synthase activity. Insulin reversed all these parameters to values in normal pregnancies, an effect blocked by ZM-241385 and l-NAME. CONCLUSIONS GDM and normal pregnancy HUVEC phenotypes are differentially responsive to insulin, a phenomenon where insulin acts as protecting factor for endothelial dysfunction characteristic of this syndrome. Abnormal adenosine plasma levels, and potentially A2A-adenosine receptors and insulin receptor A, will play crucial roles in this phenomenon in GDM. PMID:21515851

  3. An adenosine kinase in apoplastic location is involved in Magnaporthe oryzae cold acclimation.

    PubMed

    Li, Jian; Jia, Baolei; Liang, Xilong; Liu, Jinliang; Wang, Yanli; Liang, Xunna; Yan, Hai; Wang, Yuhan; Zhang, Shihong

    2014-04-01

    Cold acclimation is an important process to increase freezing tolerance for over-winter survival in many organisms. The apoplastic area is very important in cold acclimation. Two-dimensional electrophoresis was used to identify apoplastic proteins involved in the cold acclimation process of the filamentous fungus Magnaporthe oryzae, and nine protein spots showed at least 1.5-fold increase during cold treatment. These proteins were further analyzed by matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry. One of these proteins was identified to be an adenosine kinase (MoAK), an ortholog of the adenosine kinase from Saccharomyces cerevisiae. The MoAK gene showed significantly increased in transcription level. Microscopic analyses showed that an MoAK::GFP fusion protein was localized in the apoplastic region. The MoAk protein showed anti-freezing activity when expressed in yeast. These results indicated that cold acclimation is crucial for fungal freezing tolerance and MoAK played an important role in this process in M. oryzae. PMID:23681700

  4. Nucleotide Binding Site Communication in Arabidopsis thaliana Adenosine 5;-Phosphosulfate Kinase

    SciTech Connect

    Ravilious, Geoffrey E.; Jez, Joseph M. (WU)

    2012-08-31

    Adenosine 5{prime}-phosphosulfate kinase (APSK) catalyzes the ATP-dependent synthesis of adenosine 3{prime}-phosphate 5{prime}-phosphosulfate (PAPS), which is an essential metabolite for sulfur assimilation in prokaryotes and eukaryotes. Using APSK from Arabidopsis thaliana, we examine the energetics of nucleotide binary and ternary complex formation and probe active site features that coordinate the order of ligand addition. Calorimetric analysis shows that binding can occur first at either nucleotide site, but that initial interaction at the ATP/ADP site was favored and enhanced affinity for APS in the second site by 50-fold. The thermodynamics of the two possible binding models (i.e. ATP first versus APS first) differs and implies that active site structural changes guide the order of nucleotide addition. The ligand binding analysis also supports an earlier suggestion of intermolecular interactions in the dimeric APSK structure. Crystallographic, site-directed mutagenesis, and energetic analyses of oxyanion recognition by the P-loop in the ATP/ADP binding site and the role of Asp136, which bridges the ATP/ADP and APS/PAPS binding sites, suggest how the ordered nucleotide binding sequence and structural changes are dynamically coordinated for catalysis.

  5. Syzygium cumini inhibits adenosine deaminase activity and reduces glucose levels in hyperglycemic patients.

    PubMed

    Bopp, A; De Bona, K S; Bellé, L P; Moresco, R N; Moretto, M B

    2009-08-01

    Syzigium cumini (L.) Skeels from the Myrtaceae family is among the most common medicinal plants used to treat diabetes in Brazil. Leaves, fruits, and barks of S. cumini have been used for their hypoglycemic activity. Adenosine deaminase (ADA) is an important enzyme that plays a relevant role in purine and DNA metabolism, immune responses, and peptidase activity. ADA is suggested to be an important enzyme for modulating the bioactivity of insulin, but its clinical significance in diabetes mellitus (DM) has not yet been proven. In this study, we examined the effect of aqueous leaf extracts of S. cumini (L.) (ASC) on ADA activity of hyperglycemic subjects and the activity of total ADA, and its isoenzymes in serum and erythrocytes. The present study indicates that: (i) the ADA activity in hyperglycemic serum was higher than normoglycemic serum and ADA activity was higher when the blood glucose level was more elevated; (ii) ASC (60-1000 microg/mL) in vitro caused a concentration-dependent inhibition of total ADA activity and a decrease in the blood glucose level in serum; (iii) ADA1 and 2 were reduced both in erythrocytes and in hyperglycemic serum. These results suggest that the decrease of ADA activity provoked by ASC may contribute to control adenosine levels and the antioxidant defense system of red cells and could be related to the complex ADA/DPP-IV-CD26 and the properties of dipeptidyl peptidase IV (DPP-IV) inhibitors which serve as important regulators of blood glucose. PMID:19709327

  6. Hydrogen peroxide induced adenosine diphosphate ribosyl transferase (ADPRT) response in patients with inflammatory bowel disease.

    PubMed Central

    Markowitz, M M; Rozen, P; Pero, R W; Tobi, M; Miller, D G

    1988-01-01

    The sample population in this initial case control study of the adenosine diphosphate ribosyl transferase (ADPRT) response of inflammatory bowel disease patients included: 23 patients with ulcerative colitis (UC)-active and inactive, 13 patients with Crohn's disease (CD)-active and inactive, 14 first degree relatives of UC and CD patients, and 19 age-matched controls. Adenosine diphosphate ribosyl transferase activity was determined after one hour incubation with 1% plasma (the constitutive value) or with 1% plasma and 100 microM H2O2 (the activated value) with the resulting difference designated as the induced value. Statistically significant decrease in ADPRT activity was found for the constitutive, activated and induced values in human mononuclear leucocytes of UC and CD patients, compared with controls. The values in the first degree relatives of UC and CD patients were not significantly different from either the control or disease populations, indicating an intermediate ADPRT response. These results may be related to the nature of the immunological response of IBD patients and comparable with similar findings in other diseases with known DNA repair deficiencies--for example, colon cancer. PMID:3146530

  7. Context effects on N6-adenosine methylation sites in prolactin mRNA.

    PubMed Central

    Narayan, P; Ludwiczak, R L; Goodwin, E C; Rottman, F M

    1994-01-01

    The methylation of internal adenosine residues in mRNA only occurs within GAC or AAC sequences. Although both of these sequence motifs are utilized, a general preference has been noted for the extended sequence RGACU. Not all RGACU sequences in an mRNA are methylated and the mechanisms that govern the selection of methylation sites in mRNA remain unclear. To address this problem we have examined the methylation of transcripts containing sequences of a natural mRNA, namely, bovine prolactin mRNA. In this mRNA, a specific AGACU sequence in the 3' untranslated region is the predominant site of methylation both in vivo and in vitro. The degree to which N6-adenosine methyltransferase recognizes the sequence context of the consensus methylation site was explored by mutational analysis of the nucleotides adjacent to the core sequence as well as the extended regions in which the core element was found. Our results indicate that efficient methylation depends on the extended five nucleotide consensus sequence but is strongly influenced by the context in which the consensus sequence occurs within the overall mRNA molecule. Furthermore, consensus methylation sites present in an RNA duplex are not recognized by the methyltransferase. Images PMID:8127679

  8. Calculations of the circular dichroism of adenosine derivatives constrained in the syn form

    PubMed Central

    Miles, Daniel W.; Farmer, Morris; Eyring, Henry

    1980-01-01

    The rotational strengths of the four longer wavelength transitions, B2u, B1u, and the two E1u, of adenosine derivatives constrained in the syn form have been investigated theoretically and experimentally. The theory combines a complete neglect of differential overlap version S (CNDO/S) description of the base with a generalized bond exciton method by means of a matrix method. Rotational strength wheels for these transitions showing the rotational strength as a function of the glycosidic rotational angles are presented and sector rules discussed. Similar sector rules are predicted for purine nucleoside derivatives containing the 6-amino substituent, regardless of heteroatom content at positions 1 or 3 of the base. The sector rules for the B2u rotational strength of purine nucleosides lacking the 6-amino substituent are strongly influenced by aza substitution. The circular dichroism spectra of 3-deazaadenosine, 8-(?-hydroxyisopropyl)-adenosine, and other purine nucleosides having a strong preference for the syn conformation are presented and compared with the theoretical results. PMID:16592840

  9. Inhibition of adenosine deaminase (ADA)-mediated metabolism of cordycepin by natural substances

    PubMed Central

    Li, Gen; Nakagome, Izumi; Hirono, Shuichi; Itoh, Tomoo; Fujiwara, Ryoichi

    2015-01-01

    Cordycepin, which is an analogue of a nucleoside adenosine, exhibits a wide variety of pharmacological activities including anticancer effects. In this study, ADA1- and ADA2-expressing HEK293 cells were established to determine the major ADA isoform responsible for the deamination of cordycepin. While the metabolic rate of cordycepin deamination was similar between ADA2-expressing and Mock cells, extensive metabolism of cordycepin was observed in the ADA1-expressing cells with Km and Vmax values of 54.9 ?mol/L and 45.8 nmole/min/mg protein. Among five natural substances tested in this study (kaempferol, quercetin, myricetin, naringenin, and naringin), naringin strongly inhibited the deamination of cordycepin with Ki values of 58.8 ?mol/L in mouse erythrocytes and 168.3 ?mol/L in human erythrocytes. A treatment of Jurkat cells with a combination of cordycepin and naringin showed significant cytotoxicity. Our in silico study suggests that not only small molecules such as adenosine derivatives but also bulky molecules like naringin can be a potent ADA1 inhibitor for the clinical usage.

  10. Sonogashira alkynylation of unprotected 8-brominated adenosines and guanosines: fluorescence properties of compact conjugated acetylenes containing a purine ring

    Microsoft Academic Search

    Andrew G. Firth; Ian J. S. Fairlamb; Kate Darley; Christoph G. Baumann

    2006-01-01

    A practical Sonogashira alkynylation protocol for the preparation of 8-alkynylated adenosines and guanosines has been developed. Protection of the sugar hydroxyl substituents is not required; protection hinders the purification of these products. A preliminary fluorescent study is reported, which shows that the presence of a substituent on the phenylene ring influences the fluorescent properties considerably, an outcome that could be

  11. Effect of doxazosin on stretch-activated adenosine triphosphate release in bladder urothelial cells from patients with benign prostatic hyperplasia

    Microsoft Academic Search

    Yan Sun; Jennifer MaLossi; Stephen C Jacobs; Toby C Chai

    2002-01-01

    Objectives. Recent data suggest that the bladder urothelium may have a sensory function by way of release of adenosine triphosphate (ATP) during stretch, which then acts as a sensory neurotransmitter. Because benign prostatic hyperplasia (BPH) can give rise to irritative (hypersensory) voiding patterns, we questioned whether the bladder urothelium from patients with BPH released more ATP during in vitro stretch

  12. Application of cationic liposomes containing surfactants to an enhancer in firefly bioluminescent assay of adenosine 5?-triphosphate

    Microsoft Academic Search

    Tamio Kamidate; Satoko Niwa; Naohiro Nakata

    2000-01-01

    The effects of surfactant having single and two alkyl chains as a component of liposomes on the intensity of bioluminescence (BL) from firefly luciferin–luciferase reaction with adenosine 5?-triphosphate (ATP) and on the stability of liposomes were investigated by use of vesicles formed by extrusion technique. Stearyltrimethylammonium chloride (STAC) and distearyldimethylammonium chloride (DSDAC) were used as a surfactant having single and

  13. Regulatory T cell-derived adenosine induces dendritic cell migration through the Epac-Rap1 pathway.

    PubMed

    Ring, Sabine; Pushkarevskaya, Anna; Schild, Hansjörg; Probst, Hans Christian; Jendrossek, Verena; Wirsdörfer, Florian; Ledent, Catherine; Robson, Simon Christopher; Enk, Alexander H; Mahnke, Karsten

    2015-04-15

    Dendritic cells (DC) are one target for immune suppression by regulatory T cells (Treg), because their interaction results in reduced T cell stimulatory capacity and secretion of inhibitory cytokines in DC. We show that DC in the presence of Treg are more mobile as compared with cocultures with conventional CD4(+) T cells and form DC-Treg aggregates within 2 h of culture. The migration of DC was specifically directed toward Treg, as Treg, but not CD4(+) T cells, attracted DC in Boyden chambers. Treg deficient for the ectonucleotidase CD39 were unable to attract DC. Likewise, addition of antagonists for A2A adenosine receptors abolished the formation of DC-Treg clusters, indicating a role for adenosine in guiding DC-Treg interactions. Analysis of the signal transduction events in DC after contact to Treg revealed increased levels of cAMP, followed by activation of Epac1 and the GTPase Rap1. Subsequently activated Rap1 localized to the subcortical actin cytoskeleton in DC, providing a means by which directed locomotion of DC toward Treg is facilitated. In aggregate, these data show that Treg degrade ATP to adenosine via CD39, attracting DC by activating Epac1-Rap1-dependent pathways. As a consequence, DC-Treg clusters are formed and DC are rendered less stimulatory. This adenosine-mediated attraction of DC may therefore act as one mechanism by which Treg regulate the induction of immune responses by DC. PMID:25780038

  14. Generation and accumulation of immunosuppressive adenosine by human CD4+CD25highFOXP3+ regulatory T cells.

    PubMed

    Mandapathil, Magis; Hilldorfer, Benedict; Szczepanski, Miroslaw J; Czystowska, Malgorzata; Szajnik, Marta; Ren, Jin; Lang, Stephan; Jackson, Edwin K; Gorelik, Elieser; Whiteside, Theresa L

    2010-03-01

    Naturally occurring regulatory T cells (nTreg) are crucial for maintaining tolerance to self and thus preventing autoimmune diseases and allograft rejections. In cancer, Treg down-regulate antitumor responses by several distinct mechanisms. This study analyzes the role the adenosinergic pathway plays in suppressive activities of human nTreg. Human CD4(+)CD25(high)FOXP3(+) Treg overexpress CD39 and CD73, ectonucleotidases sequentially converting ATP into AMP and adenosine, which then binds to A(2a) receptors on effector T cells, suppressing their functions. CD4(+)CD39(+) and CD4(+)CD25(high) T cells express low levels of adenosine deaminase (ADA), the enzyme responsible for adenosine breakdown, and of CD26, a surface-bound glycoprotein associated with ADA. In contrast, T effector cells are enriched in CD26/ADA but express low levels of CD39 and CD73. Inhibitors of ectonucleotidase activity (e.g. ARL67156) and antagonists of the A(2a) receptor (e.g. ZM241385) blocked Treg-mediated immunosuppression. The inhibition of ADA activity on effector T cells enhanced Treg-mediated immunosuppression. Thus, human nTreg characterized by the presence of CD39 and the low expression of CD26/ADA are responsible for the generation of adenosine, which plays a major role in Treg-mediated immunosuppression. The data suggest that the adenosinergic pathway represents a potential therapeutic target for regulation of immunosuppression in a broad variety of human diseases. PMID:19858205

  15. Rational Design of Sulfonated A3 Adenosine Receptor-Selective Nucleosides as Pharmacological Tools to Study Chronic Neuropathic Pain

    PubMed Central

    Paoletta, Silvia; Tosh, Dilip K.; Finley, Amanda; Gizewski, Elizabeth T.; Moss, Steven M.; Gao, Zhan-Guo; Auchampach, John A.; Salvemini, Daniela; Jacobson, Kenneth A.

    2013-01-01

    (N)-Methanocarba (bicyclo[3.1.0]hexane)-adenosine derivatives were probed for sites of charged sulfonate substitution, which precludes diffusion across biological membranes, e.g. blood brain barrier. Molecular modeling predicted that sulfonate groups on C2-phenylethynyl substituents would provide high affinity at both mouse (m) and human (h) A3 adenosine receptors (ARs), while a N6-p-sulfo-phenylethyl substituent would determine higher hA3AR vs. mA3AR affinity. These modeling predictions, based on steric fitting of the binding cavity and crucial interactions with key residues, were confirmed by binding/efficacy studies of synthesized sulfonates. N6-3-Chlorobenzyl-2-(3-sulfophenylethynyl) derivative 7 (MRS5841) bound selectively to h/m A3ARs (Ki hA3AR 1.9 nM) as agonist, while corresponding p-sulfo isomer 6 (MRS5701) displayed mixed A1/A3AR agonism. Both nucleosides administered i.p. reduced mouse chronic neuropathic pain that was ascribed to either A3 or A1/A3ARs using A3AR genetic deletion. Thus, rational design methods based on A3AR homology models successfully predicted sites for sulfonate incorporation, for delineating adenosine’s CNS vs. peripheral actions. PMID:23789857

  16. Role of JunB in Adenosine A2B Receptor–Mediated Vascular Endothelial Growth Factor Production

    PubMed Central

    Biktasova, Asel; Goldstein, Anna E.; Zhang, Qinkun; Biaggioni, Italo; Dikov, Mikhail M.

    2014-01-01

    Interstitial adenosine stimulates neovascularization in part through A2B adenosine receptor-dependent upregulation of vascular endothelial growth factor (VEGF). In the current study, we tested the hypothesis that A2B receptors upregulate JunB, which can contribute to stimulation of VEGF production. Using the human microvascular endothelial cell line, human mast cell line, mouse cardiac Sca1-positive stromal cells, and mouse Lewis lung carcinoma (LLC) cells, we found that adenosine receptor-dependent upregulation of VEGF production was associated with an increase in VEGF transcription, activator protein-1 (AP-1) activity, and JunB accumulation in all cells investigated. Furthermore, the expression of JunB, but not the expression of other genes encoding transcription factors from the Jun family, was specifically upregulated. In LLC cells expressing A2A and A2B receptor transcripts, only the nonselective adenosine agonist NECA (5?-N-ethylcarboxamidoadenosine), but not the selective A2A receptor agonist CGS21680 [2-p-(2-carboxyethyl) phenylethylamino-5?-N-ethylcarboxamidoadenosine], significantly increased JunB reporter activity and JunB nuclear accumulation, which were inhibited by the A2B receptor antagonist PSB603 [(8-[4-[4-((4-chlorophenzyl)piperazide-1-sulfonyl)phenyl

  17. Reduction of postischemic brain damage and memory deficits following treatment with the selective adenosine A 1 receptor agonist

    Microsoft Academic Search

    Mark Beenhakker; Rick C.-S. Lin; Margaret F. Carter; Ian A. Paul; Norbert Bischofberger; Kenneth A. Jacobson

    1996-01-01

    Agonists of adenosine A1 receptors have been frequently proposed as candidates for clinical development in treatment of cerebral ischemia and stroke. Numerous experimental studies have shown that pre- and postischemic administration of these drugs results in a very significant reduction of postischemic brain damage. However, only a few studies determined the impact of cerebral ischemia and drug treatment on postischemic

  18. SLEEP, Vol. 35, No. 7, 2012 967 Caffeine-Related Sleep Disturbance and Adenosine Receptor--Byrne et al INTRODUCTION

    E-print Network

    Nyholt, Dale R.

    SLEEP, Vol. 35, No. 7, 2012 967 Caffeine-Related Sleep Disturbance and Adenosine Receptor--Byrne et al INTRODUCTION Caffeine is the most widely used psychoactive drug in the world, being used- feine, and caffeine consumption and withdrawal is known to cause many side effects. One of the most

  19. Adenosine A1 receptors and the anticonvulsant potential of drugs effective in the model of 3-nitropropionic acid-induced seizures in mice.

    PubMed

    Zuchora, Beata; Wielosz, Marian; Urba?ska, Ewa M

    2005-01-01

    The role of adenosine A1 receptors in the activity of drugs and substances protecting against seizures evoked by mitochondrial toxin, 3-nitropropionic acid (3-NPA) was studied in mice. Non-selective A1/A2 adenosine receptor antagonist, aminophylline and selective A1 adenosine receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) diminished the anticonvulsive effects of diazepam, phenobarbital, valproate and gabapentin. In contrast, A1/A2 adenosine receptor antagonist, 8-(p-sulfophenyl)theophylline (8pSPT) not penetrating via blood-brain barrier was ineffective. Aminophylline and DPCPX but not 8pSPT also reversed the protective action of A1/A2 adenosine receptor agonist, 2-chloroadenosine (2-CADO) and selective A1 adenosine receptor agonist, R-N6-phenylisopropyloadenosine (R-PIA), against 3-NPA-evoked convulsions. Obtained results suggest that the central adenosine A1 receptor stimulation may play a role in the anticonvulsive potential of diazepam, phenobarbital, valproate and gabapentin in a novel model of 3-NPA-evoked seizures. Moreover, concomitant application of aminophylline with these drugs may reduce their clinical antiepileptic efficacy, especially among patients suffering from seizures related to the disturbances of mitochondrial respiratory chain. PMID:15572277

  20. Laboratory and field comparisons of adenosine influx in Plasmodium falciparum and Plasmodium vivax infected erythrocytes with genetic abnormalities from patients in Myanmar.

    PubMed

    Myint-Oo; O'Sullivan, W J; Gero, A M

    1997-03-01

    Influx of the purine nucleoside, adenosine, was assessed in erythrocytes from both normal subjects and from subjects with a range of genetically determined erythrocyte disorders from Myanmar. The latter included alpha-thalassemia major (Myanmar variant), beta-thalassemia major (Myanmar variant), beta-thalassemia trait, HbEE and HbAE erythrocytes and two variants of glucose-6-phosphate dehydrogenase (G6PDH) deficiency. Significant reductions (p < 0.01) of adenosine influx were observed in erythrocytes from individuals with alpha- and beta-thalassemia major and severe G6PDH deficiency. Abnormal erythrocytes infected with the malarial parasites, Plasmodium falciparum or Plasmodium vivax, demonstrated a reduction in adenosine transport which correlated with the proportion of abnormal erythrocytes present in the samples obtained. The effect of nitrobenzylthioinosine (NBMPR) on adenosine influx was explored in normal and abnormal erythrocytes. In all these cases, NBMPR completely inhibited the transport of adenosine. However, transport of adenosine into P. falciparum and P. vivax-infected normal erythrocytes and abnormal cells was only inhibited 50-60% by NBMPR. The combination of tubercidin and NBMPR completely blocked adenosine transport into both normal and abnormal erythrocytes infected with either P. falciparum or P. vivax. PMID:9322280

  1. A new chemical tool (C0036E08) supports the role of adenosine A(2B) receptors in mediating human mast cell activation.

    PubMed

    Buceta, Montserrat; Domínguez, Eduardo; Castro, Marián; Brea, José; Alvarez, David; Barcala, Javier; Valdés, Luis; Alvarez-Calderón, Pedro; Domínguez, Fernando; Vidal, Bernat; Díaz, Jose Luis; Miralpeix, Montse; Beleta, Jorge; Cadavid, María Isabel; Loza, María Isabel

    2008-10-01

    Asthma is a chronic inflammatory disease of the airways that involves many cell types, amongst which mast cells are known to be important. Adenosine, a potent bronchoconstricting agent, exerts its ability to modulate adenosine receptors of mast cells thereby potentiating derived mediator release, histamine being one of the first mediators to be released. The heterogeneity of sources of mast cells and the lack of highly potent ligands selective for the different adenosine receptor subtypes have been important hurdles in this area of research. In the present study we describe compound C0036E08, a novel ligand that has high affinity (pK(i) 8.46) for adenosine A(2B) receptors, being 9 times, 1412 times and 3090 times more selective for A(2B) receptors than for A(1), A(2A) and A(3) receptors, respectively. Compound C0036E08 showed antagonist activity at recombinant and native adenosine receptors, and it was able to fully block NECA-induced histamine release in freshly isolated mast cells from human bronchoalveolar fluid. C0036E08 has been shown to be a valuable tool for the identification of adenosine A(2B) receptors as the adenosine receptors responsible for the NECA-induced response in human mast cells. Considering the increasing interest of A(2B) receptors as a therapeutic target in asthma, this chemical tool might provide a base for the development of new anti-asthmatic drugs. PMID:18687311

  2. Structure-Activity Relationships of Truncated C2- or C8-Substituted Adenosine Derivatives as Dual Acting A2A and A3 Adenosine Receptor Ligands

    PubMed Central

    Hou, Xiyan; Majik, Mahesh S.; Kim, Kyunglim; Pyee, Yuna; Lee, Yoonji; Alexander, Varughese; Chung, Hwa-Jin; Lee, Hyuk Woo; Chandra, Girish; Lee, Jin Hee; Park, Seul-gi; Choi, Won Jun; Kim, Hea Ok; Phan, Khai; Gao, Zhan-Guo; Jacobson, Kenneth A.; Choi, Sun; Lee, Sang Kook; Jeong, Lak Shin

    2011-01-01

    Truncated N6-substituted-4?-oxo- and 4?-thioadenosine derivatives with C2 or C8 substitution were studied as dual acting A2A and A3 adenosine receptor (AR) ligands. The lithiation-mediated stannyl transfer and palladium-catalyzed cross coupling reactions were utilized for functionalization of the C2 position of 6-chloropurine nucleosides. An unsubstituted 6-amino group and a hydrophobic C2 substituent were required for high affinity at the hA2AAR, but hydrophobic C8 substitution abolished binding at the hA2AAR. However, most of synthesized compounds displayed medium to high binding affinity at the hA3AR, regardless of C2 or C8 substitution, and low efficacy in a functional cAMP assay. Several compounds tended to be full hA2AAR agonists. C2 substitution probed geometrically through hA2AAR-docking, was important for binding in order of hexynyl > hexenyl > hexanyl. Compound 4g was the most potent ligand acting dually as hA2AAR agonist and hA3AR antagonist, which might be useful for treatment of asthma or other inflammatory diseases. PMID:22142423

  3. Soluble and membrane-associated human low-affinity adenosine binding protein (adenotin): properties and homology with mammalian and avian stress proteins.

    PubMed

    Hutchison, K A; Nevins, B; Perini, F; Fox, I H

    1990-05-29

    A low-affinity adenosine binding protein has recently been distinguished from the adenosine A2 receptor and purified from human placental membranes. Soluble human placental extracts contain an adenosine binding activity that has properties similar to those of the membrane low-affinity adenosine binding protein. The binding protein was purified from soluble human placental extracts 134-fold to 89% purity with a Bmax of 2.5 nmol/mg. It comprises 0.7-0.9% of the soluble protein. The major purified soluble protein has a subunit molecular mass of 98 kDa and a Stokes radius identical with that of the membrane-bound adenosine binding protein. Competition analysis of the soluble protein revealed similar affinities and an identical potency order for displacement of 5'-(N-ethylcarbamoyl)[2,8-3H]adenosine ([3H]NECA) as follows: NECA greater than 2-chloroadenosine greater than adenosine greater than (R)-N6-(2-phenylisopropyl)adenosine. The soluble binding protein was more acidic than the membrane binding protein as revealed by a comparison of the elution properties during ion exchange chromatography. A second form of soluble adenosine binding activity comprised 17% of the major form and had a charge similar to that of the membrane binding protein, a smaller Stokes radius, and a subunit molecular mass of 74 kDa. Carbohydrate composition analysis revealed that the major soluble form has 4.3% carbohydrate by weight as compared to the membrane-associated form, which has 5.5% carbohydrate by weight.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2378869

  4. Increased adenosine levels in mice expressing mutant glial fibrillary acidic protein in astrocytes result in failure of induction of LTP reversal (depotentiation) in hippocampal CA1 neurons.

    PubMed

    Fujii, Satoshi; Tanaka, Kenji F; Ikenaka, Kazuhiro; Yamazaki, Yoshihiko

    2014-08-26

    Astrocytes regulate the activity of neighboring neurons by releasing chemical transmitters, including ATP. Adenosine levels in the cerebrospinal fluid of mice that express a mutant human glial fibrillary acidic protein in astrocytes are slightly elevated compared to those in wild type mice and this might result from the observed increased release by mutant astrocytes of ATP, which can be used to produce adenosine. Using hippocampal slices from these mutant mice, we examined whether the increased endogenous adenosine levels in the hippocampus modulate the reversal of long-term potentiation (LTP), i.e. depotentiation (DP), in CA1 neurons. In hippocampal slices from wild type mice, a stable LTP was induced by tetanic stimulation consisting of 100 pulses at 100 Hz, and this was reversed by a train of low frequency stimulation (LFS) of 500 pulses at 1 Hz applied 30 min later. This induction of DP was inhibited by application of either 100 nM adenosine or 0.5 nM N(6)-cyclopentyladenosine, an adenosine A1 receptor agonist, during LFS, indicating that the increase in extracellular adenosine levels attenuated DP induction by acting on adenosine A1 receptors. In contrast, although a stable LTP was also induced in hippocampal slices from mutant mice, induction of DP was inhibited, but DP could be induced by application, during LFS, of 50 nM 8-cyclopentyltheophylline, an adenosine A1 receptor antagonist. These results suggest that a small increase in extracellular adenosine levels resulting from increased ATP release by astrocytes results in attenuation of DP in hippocampal CA1 neurons in the mutant mice. PMID:25017946

  5. The ADA*2 allele of the adenosine deaminase gene (20q13.11) and recurrent spontaneous abortions: an age-dependent association

    PubMed Central

    Nunes, Daniela Prudente Teixeira; Spegiorin, Lígia Cosentino Junqueira Franco; de Mattos, Cinara Cássia Brandão; Oliani, Antonio Helio; Vaz-Oliani, Denise Cristina Mós; de Mattos, Luiz Carlos

    2011-01-01

    OBJECTIVE: Adenosine deaminase acts on adenosine and deoxyadenosine metabolism and modulates the immune response. The adenosine deaminase G22A polymorphism (20q.11.33) influences the level of adenosine deaminase enzyme expression, which seems to play a key role in maintaining pregnancy. The adenosine deaminase 2 phenotype has been associated with a protective effect against recurrent spontaneous abortions in European Caucasian women. The aim of this study was to investigate whether the G22A polymorphism of the adenosine deaminase gene is associated with recurrent spontaneous abortions in Brazilian women. METHODS: A total of 311 women were recruited to form two groups: G1, with a history of recurrent spontaneous abortions (N?=?129), and G2, without a history of abortions (N?=?182). Genomic DNA was extracted from peripheral blood with a commercial kit and PCR-RFLP analysis was used to identify the G22A genetic polymorphism. Fisher's exact test and odds ratio values were used to compare the proportions of adenosine deaminase genotypes and alleles between women with and without a history of recurrent spontaneous abortion (p<0.05). The differences between mean values for categorical data were calculated using unpaired t tests. The Hardy-Weinberg equilibrium was assessed with a chi-square test. RESULTS: Statistically significant differences were identified for the frequencies of adenosine deaminase genotypes and alleles between the G1 and G2 groups when adjusted for maternal age. CONCLUSIONS: The results suggest that the adenosine deaminase *2 allele is associated with a low risk for recurrent spontaneous abortions, but this association is dependent on older age. PMID:22086524

  6. Role of 2',3'-cyclic nucleotide 3'-phosphodiesterase in the renal 2',3'-cAMP-adenosine pathway.

    PubMed

    Jackson, Edwin K; Gillespie, Delbert G; Mi, Zaichuan; Cheng, Dongmei; Bansal, Rashmi; Janesko-Feldman, Keri; Kochanek, Patrick M

    2014-07-01

    Energy depletion increases the renal production of 2',3'-cAMP (a positional isomer of 3',5'-cAMP that opens mitochondrial permeability transition pores) and 2',3'-cAMP is converted to 2'-AMP and 3'-AMP, which in turn are metabolized to adenosine. Because the enzymes involved in this "2',3'-cAMP-adenosine pathway" are unknown, we examined whether 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) participates in the renal metabolism of 2',3'-cAMP. Western blotting and real-time PCR demonstrated expression of CNPase in rat glomerular mesangial, preglomerular vascular smooth muscle and endothelial, proximal tubular, thick ascending limb and collecting duct cells. Real-time PCR established the expression of CNPase in human glomerular mesangial, proximal tubular and vascular smooth muscle cells; and the level of expression of CNPase was greater than that for phosphodiesterase 4 (major enzyme for the metabolism of 3',5'-cAMP). Overexpression of CNPase in rat preglomerular vascular smooth muscle cells increased the metabolism of exogenous 2',3'-cAMP to 2'-AMP. Infusions of 2',3'-cAMP into isolated CNPase wild-type (+/+) kidneys increased renal venous 2'-AMP, and this response was diminished by 63% in CNPase knockout (-/-) kidneys, whereas the conversion of 3',5'-cAMP to 5'-AMP was similar in CNPase +/+ vs. -/- kidneys. In CNPase +/+ kidneys, energy depletion (metabolic poisons) increased kidney tissue levels of adenosine and its metabolites (inosine, hypoxanthine, xanthine, and uric acid) without accumulation of 2',3'-cAMP. In contrast, in CNPase -/- kidneys, energy depletion increased kidney tissue levels of 2',3'-cAMP and abolished the increase in adenosine and its metabolites. In conclusion, kidneys express CNPase, and renal CNPase mediates in part the renal 2',3'-cAMP-adenosine pathway. PMID:24808540

  7. CHOLESTEROL 27-HYDROXYLASE BUT NOT APOLIPOPROTEIN apoE CONTRIBUTES TO A2A ADENOSINE RECEPTOR STIMULATED REVERSE CHOLESTEROL TRANSPORT

    PubMed Central

    Bingham, Taiese Crystal; Parathath, Saj; Tian, Heather; Reiss, Allison; Chan, Edwin; Fisher, Edward A.; Cronstein, Bruce N.

    2011-01-01

    Movement of free cholesterol between the cellular compartment and acceptor is governed by cholesterol gradients that are determined by several enzymes and reverse cholesterol transport proteins. We have previously demonstrated that adenosine A2A receptors inhibit foam cell formation and stimulate production of cholesterol 27-hydroxylase (CYP27A1), an enzyme involved in the conversion of cholesterol to oxysterols. We therefore asked whether the effect of adenosine A2A receptors on foam cell formation in vitro are mediated by CYP27A1 or apoE, a carrier for cholesterol in the serum. We found that specific lentiviral siRNA infection markedly reduced apoE or 27-hydroxylase mRNA in THP-1 cells. Despite diminished apoE expression (p< 0.0002, IFN? CGS vs. IFN? alone, n= 4) CGS-21680, an adenosine A2A receptor agonist, inhibits foam cell formation. In contrast, CGS-21680 had no effect on reducing foam cell formation in CYP27A1 KD cells (4±2% p<0.5113 inhibition vs. IFN? alone n= 4). Previously we reported the A2A agonist CGS-21680 increases apoAI-mediated cholesterol efflux nearly 2-fold in wildtype macrophages. Adenosine receptor activation had no effect on cholesterol efflux in CYP27A1 KD cells but reduced efflux in apoE KD cells. These results demonstrate that adenosine A2A receptor occupancy diminishes foam cell formation by increasing expression and function of CYP27A1. PMID:21258856

  8. Experimental hypothyroidism modifies specific binding of A1 and A2A analogues to adenosine receptors in the rat kidney

    PubMed Central

    Franco, Martha; Galicia, Othir; Quintana, Alicia; Martínez, Flavio

    2004-01-01

    Binding kinetic studies with the adenosine analogues [3H]CPA (0.250–50 nM) and [3H]CGS21680 (0.1–100 nM) were performed in renal tissue from control (NL) and thyroidectomised (HTX) rats. We propose that the low renal adenosine content reported in hypothyroid rats may induce changes in the density and/or affinity of adenosine receptor, distributed in the cortex (C), outer medulla (OM), and inner medulla (IM) of the kidney. [3H]CPA and [3H]CGS21680 binding saturation isotherms were fitted by nonlinear regression analysis and evaluated by Furchgott's method. These results revealed high (KH) and low (KL) affinity (KD) sites for both compounds. As expected, a heterogeneous pattern was observed for Bmax and KD values. Bound [3H]CPA and [3H]CGS21680 were displaced by increasing concentrations of nonlabelled DPCPX and NECA, respectively, indicating the presence of A1 and A2A adenosine receptors distributed in the renal segments studied. The relative intrinsic efficacy (?) for [3H]CPA and [3H]CGS21680 showed extreme values (far from 1.0), 0.5 in IM NL and 2.70 in IM HTX for [3H]CGS21680. Our results indicate that A2A adenosine receptor is predominant in IM from HTX, but A1 receptors are expressed preferentially in C in NL. We conclude that the changes observed in number, affinity, and ? for the A2A receptor in IM from HTX might be responsible from alterations in medullary function, that is, incapacity for urine concentration as observed in the hypothyroid kidney. PMID:15148254

  9. Modulation of Ca2+-dependent and Ca2+-independent miniature endplate potentials by phorbol ester and adenosine in frog

    PubMed Central

    Searl, Timothy J; Silinsky, Eugene M

    2005-01-01

    Phorbol esters and adenosine modulate transmitter release from frog motor nerves through actions at separate sites downstream of calcium entry. However, it is not known whether these agents have calcium-independent sites of action. We therefore characterised calcium independent miniature endplate potentials (mepps) generated in response to 4-aminoquinaldine (4-AQA) and then compared the modulation of these mepps by phorbol esters and adenosine with that of normal calcium dependent mepps. Application of 30??M 4-AQA resulted in the appearance of a population of mepps with amplitudes greater than twice the total population mode (mepp>2M). In the presence of 4-AQA, K+ depolarisation or hypertonicity increased the numbers of normal amplitude mepps (meppN) but had no effect on the frequency of mepp>2M events, suggesting that mepp>2M are not dependent on calcium. Treatment with the botulinum toxin (Botx) fractions C, D, or E (which selectively cleave syntaxin, synaptobrevin and SNAP-25, respectively) produced equivalent reductions in both normal and 4-AQA induced mepps, suggesting that both mepp populations have equal dependence on the intact SNARE proteins. Phorbol dibutyrate (PDBu, 100?nM) increased the frequencies of both populations of mepps recorded in the presence of 4-AQA. Adenosine (25??M) selectively reduced the numbers of meppN with no effect on the frequency of mepp>2M events. These results suggest that mepp>2M events released in response to 4-AQA are dependent on intact forms of syntaxin, synaptobrevin and SNAP-25, but unlike meppN are independent of a functional calcium sensor. The selective action of adenosine, to reduce the numbers of normal amplitude mepps without effecting the frequency of mepp>2M events, suggests that adenosine normally inhibits transmitter release through a mechanism that is dependent on the presence of a functional calcium sensor. PMID:15880138

  10. Role of 2?,3?-cyclic nucleotide 3?-phosphodiesterase in the renal 2?,3?-cAMP-adenosine pathway

    PubMed Central

    Gillespie, Delbert G.; Mi, Zaichuan; Cheng, Dongmei; Bansal, Rashmi; Janesko-Feldman, Keri; Kochanek, Patrick M.

    2014-01-01

    Energy depletion increases the renal production of 2?,3?-cAMP (a positional isomer of 3?,5?-cAMP that opens mitochondrial permeability transition pores) and 2?,3?-cAMP is converted to 2?-AMP and 3?-AMP, which in turn are metabolized to adenosine. Because the enzymes involved in this “2?,3?-cAMP-adenosine pathway” are unknown, we examined whether 2?,3?-cyclic nucleotide 3?-phosphodiesterase (CNPase) participates in the renal metabolism of 2?,3?-cAMP. Western blotting and real-time PCR demonstrated expression of CNPase in rat glomerular mesangial, preglomerular vascular smooth muscle and endothelial, proximal tubular, thick ascending limb and collecting duct cells. Real-time PCR established the expression of CNPase in human glomerular mesangial, proximal tubular and vascular smooth muscle cells; and the level of expression of CNPase was greater than that for phosphodiesterase 4 (major enzyme for the metabolism of 3?,5?-cAMP). Overexpression of CNPase in rat preglomerular vascular smooth muscle cells increased the metabolism of exogenous 2?,3?-cAMP to 2?-AMP. Infusions of 2?,3?-cAMP into isolated CNPase wild-type (+/+) kidneys increased renal venous 2?-AMP, and this response was diminished by 63% in CNPase knockout (?/?) kidneys, whereas the conversion of 3?,5?-cAMP to 5?-AMP was similar in CNPase +/+ vs. ?/? kidneys. In CNPase +/+ kidneys, energy depletion (metabolic poisons) increased kidney tissue levels of adenosine and its metabolites (inosine, hypoxanthine, xanthine, and uric acid) without accumulation of 2?,3?-cAMP. In contrast, in CNPase ?/? kidneys, energy depletion increased kidney tissue levels of 2?,3?-cAMP and abolished the increase in adenosine and its metabolites. In conclusion, kidneys express CNPase, and renal CNPase mediates in part the renal 2?,3?-cAMP-adenosine pathway. PMID:24808540

  11. Adenosine receptor activation is responsible for prolonged depression of synaptic transmission after spreading depolarization in brain slices.

    PubMed

    Lindquist, B E; Shuttleworth, C W

    2012-10-25

    Spreading depolarization (SD) is a slowly propagating, coordinated depolarization of brain tissue, which is followed by a transient (5-10min) depression of synaptic activity. The mechanisms for synaptic depression after SD are incompletely understood. We examined the relative contributions of action potential failure and adenosine receptor activation to the suppression of evoked synaptic activity in murine brain slices. Focal micro-injection of potassium chloride (KCl) was used to induce SD and synaptic potentials were evoked by electrical stimulation of Schaffer collateral inputs to hippocampal area Cornu Ammonis area 1 (CA1). SD was accompanied by loss of both presynaptic action potentials (as assessed from fiber volleys) and field excitatory postsynaptic potentials (fEPSPs). Fiber volleys recovered rapidly upon neutralization of the extracellular direct current (DC) potential, whereas fEPSPs underwent a secondary suppression phase lasting several minutes. Paired-pulse ratio was elevated during the secondary suppression period, consistent with a presynaptic mechanism of synaptic depression. A transient increase in extracellular adenosine concentration was detected during the period of secondary suppression. Antagonists of adenosine A1 receptors (8-cyclopentyl-1,3-dipropylxanthine [DPCPX] or 8-cyclopentyl-1,3-dimethylxanthine [8-CPT]) greatly accelerated fEPSP recovery and abolished increases in paired-pulse ratio normally observed after SD. The duration of fEPSP suppression was correlated with both the duration of the DC shift and the area of tissue depolarized, consistent with the model that adenosine accumulates in proportion to the metabolic burden of SD. These results suggest that in brain slices, the duration of the DC shift approximately defined the period of action potential failure, but the secondary depression of evoked responses was in large part due to endogenous adenosine accumulation after SD. PMID:22864185

  12. Neural and humoral control of regional vascular beds via A1 adenosine receptors located in the nucleus tractus solitarii.

    PubMed

    McClure, Joseph M; O'Leary, Donal S; Scislo, Tadeusz J

    2011-03-01

    Our previous studies showed that stimulation of adenosine A(1) receptors located in the nucleus of the solitary tract (NTS) exerts counteracting effects on the iliac vascular bed: activation of the adrenal medulla and ?-adrenergic vasodilation vs. sympathetic and vasopressinergic vasoconstriction. Because NTS A(1) adenosine receptors inhibit baroreflex transmission in the NTS and contribute to the pressor component of the HDR, we hypothesized that these receptors also contribute to the redistribution of blood from the visceral to the muscle vasculature via prevailing sympathetic and vasopressinergic vasoconstriction in the visceral (renal and mesenteric) vascular beds and prevailing ?-adrenergic vasodilation in the somatic (iliac) vasculature. To test this hypothesis, we compared the A(1) adenosine-receptor-mediated effects of each vasoactive factor triggered by NTS A(1) adenosine receptor stimulation [N(6)-cyclopentyladenosine (CPA), 330 pmol in 50 nl] on the regional vascular responses in urethane/chloralose-anesthetized rats. The single-factor effects were separated using adrenalectomy, ?-adrenergic blockade, V(1) vasopressin receptor blockade, and sinoaortic denervation. In intact animals, initial vasodilation was followed by large, sustained vasoconstriction with smaller responses observed in renal vs. mesenteric and iliac vascular beds. The initial ?-adrenergic vasodilation prevailed in the iliac vs. mesenteric and renal vasculature. The large and sustained vasopressinergic vasoconstriction was similar in all vascular beds. Small sympathetic vasoconstriction was observed only in the iliac vasculature in this setting. We conclude that, although A(1) adenosine-receptor-mediated ?-adrenergic vasodilation may contribute to the redistribution of blood from the visceral to the muscle vasculature, this effect is overridden by sympathetic and vasopressinergic vasoconstriction. PMID:21148476

  13. Neural and humoral control of regional vascular beds via A1 adenosine receptors located in the nucleus tractus solitarii

    PubMed Central

    McClure, Joseph M.; O'Leary, Donal S.

    2011-01-01

    Our previous studies showed that stimulation of adenosine A1 receptors located in the nucleus of the solitary tract (NTS) exerts counteracting effects on the iliac vascular bed: activation of the adrenal medulla and ?-adrenergic vasodilation vs. sympathetic and vasopressinergic vasoconstriction. Because NTS A1 adenosine receptors inhibit baroreflex transmission in the NTS and contribute to the pressor component of the HDR, we hypothesized that these receptors also contribute to the redistribution of blood from the visceral to the muscle vasculature via prevailing sympathetic and vasopressinergic vasoconstriction in the visceral (renal and mesenteric) vascular beds and prevailing ?-adrenergic vasodilation in the somatic (iliac) vasculature. To test this hypothesis, we compared the A1 adenosine-receptor-mediated effects of each vasoactive factor triggered by NTS A1 adenosine receptor stimulation [N6-cyclopentyladenosine (CPA), 330 pmol in 50 nl] on the regional vascular responses in urethane/chloralose-anesthetized rats. The single-factor effects were separated using adrenalectomy, ?-adrenergic blockade, V1 vasopressin receptor blockade, and sinoaortic denervation. In intact animals, initial vasodilation was followed by large, sustained vasoconstriction with smaller responses observed in renal vs. mesenteric and iliac vascular beds. The initial ?-adrenergic vasodilation prevailed in the iliac vs. mesenteric and renal vasculature. The large and sustained vasopressinergic vasoconstriction was similar in all vascular beds. Small sympathetic vasoconstriction was observed only in the iliac vasculature in this setting. We conclude that, although A1 adenosine-receptor-mediated ?-adrenergic vasodilation may contribute to the redistribution of blood from the visceral to the muscle vasculature, this effect is overridden by sympathetic and vasopressinergic vasoconstriction. PMID:21148476

  14. Homeostatic action of adenosine A3 and A1 receptor agonists on proliferation of hematopoietic precursor cells.

    PubMed

    Hofer, Michal; Pospísil, Milan; Znojil, Vladimír; Holá, Jirina; Streitová, Denisa; Vacek, Antonín

    2008-07-01

    Two adenosine receptor agonists, N6-(3-iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA) and N6-cyclopentyladenosine (CPA), which selectively activate adenosine A3 and A1 receptors, respectively, were tested for their ability to influence proliferation of granulocytic and erythroid cells in femoral bone marrow of mice using morphological criteria. Agonists were given intraperitoneally to mice in repeated isomolar doses of 200 nmol/kg. Three variants of experiments were performed to investigate the action of the agonists under normal resting state of mice and in phases of cell depletion and subsequent regeneration after treatment with the cytotoxic drug 5-fluorouracil. In the case of granulopoiesis, IB-MECA 1) increased by a moderate but significant level proliferation of cells under normal resting state; 2) strongly increased proliferation of cells in the cell depletion phase; but 3) did not influence cell proliferation in the regeneration phase. CPA did not influence cell proliferation under normal resting state and in the cell depletion phase, but strongly suppressed the overshooting cell proliferation in the regeneration phase. The stimulatory effect of IB-MECA on cell proliferation of erythroid cells was observed only when this agonist was administered during the cell depletion phase. CPA did not modulate erythroid proliferation in any of the functional states investigated, probably due to the lower demand for cell production as compared with granulopoiesis. The results indicate opposite effects of the two adenosine receptor agonists on proliferation of hematopoietic cells and suggest the plasticity and homeostatic role of the adenosine receptor expression. PMID:18445770

  15. Direct visualization by electron microscopy of the weakly bound intermediates in the actomyosin adenosine triphosphatase cycle.

    PubMed Central

    Pollard, T D; Bhandari, D; Maupin, P; Wachsstock, D; Weeds, A G; Zot, H G

    1993-01-01

    We used a novel stopped-flow/rapid-freezing machine to prepare the transient intermediates in the actin-myosin adenosine triphosphatase (ATPase) cycle for direct observation by electron microscopy. We focused on the low affinity complexes of myosin-adenosine triphosphate (ATP) and myosin-adenosine diphosphate (ADP)-Pi with actin filaments since the transition from these states to the high affinity actin-myosin-ADP and actin-myosin states is postulated to generate the molecular motion that drives muscle contraction and other types of cellular movements. After rapid freezing and metal replication of mixtures of myosin subfragment-1, actin filaments, and ATP, the structure of the weakly bound intermediates is indistinguishable from nucleotide-free rigor complexes. In particular, the average angle of attachment of the myosin head to the actin filament is approximately 40 degrees in both cases. At all stages in the ATPase cycle, the configuration of most of the myosin heads bound to actin filaments is similar, and the part of the myosin head preserved in freeze-fracture replicas does not tilt by more than a few degrees during the transition from the low affinity to high affinity states. In contrast, myosin heads chemically cross-linked to actin filaments differ in their attachment angles from ordered at 40 degrees without ATP to nearly random in the presence of ATP when viewed by negative staining (Craig, R., L.E. Greene, and E. Eisenberg. 1985. Proc. Natl. Acad. Sci. USA. 82:3247-3251, and confirmed here), freezing in vitreous ice (Applegate, D., and P. Flicker. 1987. J. Biol. Chem. 262:6856-6863), and in replicas of rapidly frozen samples. This suggests that many of the cross-linked heads in these preparations are dissociated from but tethered to the actin filaments in the presence of ATP. These observations suggest that the molecular motion produced by myosin and actin takes place with the myosin head at a point some distance from the actin binding site or does not involve a large change in the shape of the myosin head. Images FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 10 PMID:8457671

  16. Role of ascites adenosine deaminase in differentiating between tuberculous peritonitis and peritoneal carcinomatosis

    PubMed Central

    Kang, Seung Joo; Kim, Ji Won; Baek, Jee Hyun; Kim, Se Hyung; Kim, Byeong Gwan; Lee, Kook Lae; Jeong, Ji Bong; Jung, Yong Jin; Kim, Joo Sung; Jung, Hyun Chae; Song, In Sung

    2012-01-01

    AIM: To investigate the usefulness of tumor markers and adenosine deaminase in differentiating between tuberculous peritonitis (TBP) and peritoneal carcinomatosis (PC). METHODS: A retrospective analysis of data was performed on consecutive patients who underwent peritoneoscopic and abdominal computed tomography (CT) evaluations. Among 75 patients at the Seoul National University Hospital from January 2000 to June 2010 who underwent both tests, 27 patients (36.0%) and 25 patients (33.3%) were diagnosed with TBP and PC, respectively. Diagnosis was confirmed by peritoneoscopic biopsy. RESULTS: Serum c-reactive protein (7.88 ± 6.62 mg/dL vs 3.12 ± 2.69 mg/dL, P = 0.01), ascites adenosine deaminase (66.76 ± 32.09 IU/L vs 13.89 ± 8.95 IU/L, P < 0.01), ascites lymphocyte proportion (67.77 ± 23.41% vs 48.36 ± 18.78%, P < 0.01), and serum-ascites albumin gradient (0.72 ± 0.49 g/dL vs 1.05 ± 0.50 g/dL, P = 0.03) were significantly different between the two groups. Among tumor markers, serum and ascites carcinoembryonic antigen, serum carbohydrate antigen 19-9 showed significant difference between two groups. Abdominal CT examinations showed that smooth involvement of the parietal peritoneum was more common in the TBP group (77.8% vs 40.7%) whereas nodular involvement was more common in the PC group (14.8% vs 40.7%, P = 0.04). From receiver operating characteristic (ROC) curves ascites adenosines deaminase (ADA) showed better discriminative capability than tumor markers. An ADA cut-off level of 21 IU/L was found to yield the best results of differential diagnosis; sensitivity, specificity, positive predictive value, and negative predictive value were 92.0%, 85.0%, 88.5% and 89.5%, respectively. CONCLUSION: Besides clinical and radiologic findings, ascitic fluid ADA measurement is helpful in the differential diagnosis of TBP and PC. PMID:22719194

  17. Inhibitors of blood platelet aggregation. Effects of some 1,2-benzisothiazol-3-ones on platelet responsiveness to adenosine diphosphate and collagen.

    PubMed

    Baggaley, K H; English, P D; Jennings, L J; Morgan, B; Nunn, B; Tyrrell, A W

    1985-11-01

    A series of substituted 1,2-benzisothiazol-3-ones was synthesized, and the compounds were tested for ability to inhibit platelet aggregation induced by adenosine diphosphate and collagen in rats and guinea pigs ex vivo. Alkyl substituents at the 2-position bearing a basic group were necessary for ex vivo activity. Several of the compounds were potent inhibitors of adenosine diphosphate induced first-phase aggregation, but adverse toxicological findings terminated their further development. Preliminary studies suggested that inhibition of aggregation was not attributable to inhibition of prostanoid synthesis or to raised levels of cyclic 3',5'-adenosine monophosphate. PMID:4067991

  18. Synthesis of ?-Phosphate-Labeled and Doubly Labeled Adenosine Triphosphate Analogs.

    PubMed

    Hacker, Stephan M; Welter, Moritz; Marx, Andreas

    2015-01-01

    This unit describes the synthesis of ?-phosphate-labeled and doubly labeled adenosine triphosphate (ATP) analogs and their characterization using the phosphodiesterase I from Crotalus adamanteus (snake venom phosphodiesterase; SVPD). In the key step of the synthesis, ATP or an ATP analog, bearing a linker containing a trifluoroacetamide group attached to the nucleoside, are modified with an azide-containing linker at the terminal phosphate using an alkylation reaction. Subsequently, different labels are introduced to the linkers by transformation of one functional group to an amine and coupling to an N-hydroxysuccinimide ester. Specifically, the Staudinger reaction of the azide is employed as a straightforward means to obtain an amine in the presence of various labels. Furthermore, the fluorescence characteristics of a fluorogenic, doubly labeled ATP analog are investigated following enzymatic cleavage by SVPD. © 2015 by John Wiley & Sons, Inc. PMID:25754889

  19. [Adenosine deaminase 1 deficiency, an inborn error of metabolism underlying a severe form of combined immunodeficiency].

    PubMed

    Giraud, A; Lavocat, M-P; Cremillieux, C; Patural, H; Thouvenin, S; David, A; Perignon, J-L; Stephan, J-L

    2015-06-01

    Severe combined immune deficiencies (SCIDs) are a heterogeneous group of severe cellular immunodeficiencies. Early diagnosis is essential to allow adapted care before life-threatening systemic infections or complications associated with live vaccines. Adenosine deaminase 1 deficiency (ADA1) is an inborn error of metabolism leading to severe lymphopenia and characteristic bone lesions. Herein, we present the typical case of a child in whom ADA SCID was diagnosed at 2months of life, revealed by lung involvement and extreme lymphopenia. Immune restoration in terms of peripheral lymphocyte count with enzyme replacement therapy, namely pegylated bovine ADA, is satisfactory so far. The search for a compatible donor is underway. Correcting the genetic defect by gene transfer is also being considered. The phenotype of this very rare condition is described. A severe peripheral lymphopenia in a young child is a finding of utmost importance for the diagnosis of a primary cellular immunodeficiency. PMID:25842197

  20. Characterizations of a new Cordyceps cicadae isolate and production of adenosine and cordycepin

    PubMed Central

    Wang, Yongjun; Guo, Yanbin; Zhang, Liqin; Wu, Jia

    2012-01-01

    Cordyceps is a fastidious pathogenic fungus infecting insects, and recent years have witnessed rapid progress in its medical properties. In this study, a wild isolate, C. cicadae MP12, was characterized through in vitro cultivation and its nuclear small-subunit (SSU) ribosomal DNA (rDNA) data. In vitro culture of C. cicadae MP12 was established by growing its fruiting bodies in a solid matrix. C. cicadae MP12 was inoculated into Cryptotympana atrata cicada pupae for in vivo culture, where the fungi developed its fruiting body as well. The contents of adenosine and cordycepin in dried fruiting bodies after culture were 1421.45?g/g and 1398.12 ?g/g, respectively. Therefore, the established cultures from this study could be used for the production of various medically important metabolic substances. PMID:24031851

  1. Fluorescence aptameric sensor for isothermal circular strand-displacement polymerization amplification detection of adenosine triphosphate.

    PubMed

    Song, Weiling; Zhang, Qiao; Xie, Xuxu; Zhang, Shusheng

    2014-11-15

    In this work, isothermal circular strand-displacement polymerization amplification assay is developed for highly specific and sensitive detection of adenosine triphosphate (ATP). The amplification process consists of circular common target molecule-displacement polymerization (CCDP) and circular nucleic acid strand-displacement polymerization (CNDP). In the presence of ATP, the complementary strand was released from the aptamer by the target recognition of ATP, and catalyzed the subsequent cycle reaction. With the polymerase and primer, the displaced target triggers the process of CCDP. With the involvement of nicking endonuclease, the released complementary strand triggers the CNDP. Combined CCDP with CNDP, the exponentially produced fluorescence probes are obtained, achieving a detection limit of ATP as low as 2.6 × 10(-10)M. Moreover, the proposed strategy exhibits an excellent specificity and is successfully applied in real sample assay which demonstrates potential application in practical samples. PMID:24851721

  2. Adenosine A2A Receptor Antagonists and Parkinson’s Disease

    PubMed Central

    2011-01-01

    This Review summarizes and updates the work on adenosine A2A receptor antagonists for Parkinson’s disease from 2006 to the present. There have been numerous publications, patent applications, and press releases within this time frame that highlight new medicinal chemistry approaches to this attractive and promising target to treat Parkinson’s disease. The Review is broken down by scaffold type and will discuss the efforts to optimize particular scaffolds for activity, pharmacokinetics, and other drug discovery parameters. The majority of approaches focus on preparing selective A2A antagonists, but a few approaches to dual A2A/A1 antagonists will also be highlighted. The in vivo profiles of compounds will be highlighted and discussed to compare activities across different chemical series. A clinical report and update will be given on compounds that have entered clinical trials. PMID:22860156

  3. A conformational study of some adenosines by use of nuclear Overhauser effect

    PubMed Central

    Ueyama, M.; Tori, K.; Ikehara, M.; Kaneko, M.

    1974-01-01

    Conformations of 8-bromo-2?-[unk]-triisopropylbenzenesulfonyladenosine ([unk]) and its 3?-[unk]-isomer ([unk]) in solution have been determined by the use of intramolecular nuclear Overhauser effects in 1H NMR spectroscopy. Compound [unk] has been proved to have a conformation in which the adenosine and benzene rings are intramolecularly stacked and compound [unk] an elongated non-stacked conformation in dimethylsulphoxide. The 5?-[unk]-acetyl derivative of [unk] has also been found to adopt the intramolecularly stacked conformation in dimethylsulphoxide, but a non-stacked one in chloroform. Coupling constants observed are discussed in connection with the conformation of the ribose moiety. The 13C NMR spectra have also been examined, but no effect which could be ascribed to the stacking phenomena was observed in the carbon chemical shifts. PMID:10793760

  4. Effect of adenosine 5'-[beta,gamma-imido]triphosphate on myosin head domain movements.

    PubMed

    Hartvig, Nóra; Lõrinczy, Dénes; Farkas, Nelli; Belagyi, Joseph

    2002-04-01

    Conventional and saturation transfer electron paramagnetic resonance spectroscopy (EPR and ST EPR) was used to study the orientation of probe molecules in muscle fibers in different intermediate states of the ATP hydrolysis cycle. A separate procedure was used to obtain ST EPR spectra with precise phase settings even in the case of samples with low spectral intensity. Fibers prepared from rabbit psoas muscle were labeled with isothiocyanate spin labels at the reactive thiol sites of the catalytic domain of myosin. In comparison with rigor, a significant difference was detected in the orientation-dependence of spin labels in the ADP and adenosine 5'-[beta,gamma-imido]triphosphate (AdoPP[CH2]P) states, indicating changes in the internal dynamics and domain orientation of myosin. In the AdoPP[CH2]P state, approximately half of the myosin heads reflected the motional state of ADP-myosin, and the other half showed a different dynamic state with greater mobility. PMID:11985595

  5. Antidepressant effects of sleep deprivation require astrocyte-dependent adenosine mediated signaling.

    PubMed

    Hines, D J; Schmitt, L I; Hines, R M; Moss, S J; Haydon, P G

    2013-01-01

    Major depressive disorder is a debilitating condition with a lifetime risk of ten percent. Most treatments take several weeks to achieve clinical efficacy, limiting the ability to bring instant relief needed in psychiatric emergencies. One intervention that rapidly alleviates depressive symptoms is sleep deprivation; however, its mechanism of action is unknown. Astrocytes regulate responses to sleep deprivation, raising the possibility that glial signaling mediates antidepressive-like actions of sleep deprivation. Here, we found that astrocytic signaling to adenosine (A1) receptors was required for the robust reduction of depressive-like behaviors following 12 hours of sleep deprivation. As sleep deprivation activates synaptic A1 receptors, we mimicked the effect of sleep deprivation on depression phenotypes by administration of the A1 agonist CCPA. These results provide the first mechanistic insight into how sleep deprivation impacts mood, and provide a novel pathway for rapid antidepressant development by modulation of glial signaling in the brain. PMID:23321809

  6. Neurotransmitters adenosine triphosphate and noradrenaline induce nitric oxide release in rat vas deferens.

    PubMed

    Vetri, T; Di Maio, R; Bonafede, G; Passafiume, L; Postorino, A

    2000-06-01

    1. In rat vas deferens, electrical field stimulation (EFS) evoked a muscular biphasic tetrodotoxin (TTX)-sensitive contractile response. 2. The amplitude of this response increased with the frequency of stimulation. 3. After each stimulation, nitric oxide (NO) release was assayed and found to be released in a frequency-dependent manner. 4. NO release also occurred after treatment with exogenous neurotransmitters, adenosine 5'-triphosphate (ATP) and noradrenaline (NA). 5. Prazosin and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), respective antagonists of alpha1-adrenoceptors and P2x purinoceptors, inhibited NO release induced by NA and ATP. Both prazosin and PPADS inhibited NO release by EFS. 6. TTX failed to modify the NO release induced by exogenous neurotransmitters but abolished the release of NO and contractile response by EFS. 7. EFS and released noradrenaline and ATP induce the release of NO through postjunctional alpha1 -adrenoceptors and P2x-purinoceptors, respectively. PMID:11193001

  7. Adenosine Triphosphatase Activities in Leaves of the Mangrove Avicennia nitida Jacq

    PubMed Central

    Kylin, A.; Gee, R.

    1970-01-01

    Homogenates from the salt-excreting leaves of the mangrove Avicennia nitida were subjected to differential centrifugation and investigated for adenosine triphosphatase activities. At pH 6.75 a salt stimulation with peaks at three different sodium to potassium ratios could be demonstrated above the activity due to Mg2+ ions. The stimulation by sodium and potassium depends on the ionic strength of the test medium, higher salt concentrations being inhibitory. The plant system seems thus more complicated than the animal activities. Technically, this means that a search for (Na+ + K+)-activated ATPases in plants should be performed with a close spacing of Na:K ratios at several constant levels of salt. Literature data on the transport of Na+ and K+ indicate that the physiological situation is rather complex in plants. PMID:16657297

  8. Small molecule adenosine 5'-monophosphate activated protein kinase (AMPK) modulators and human diseases.

    PubMed

    Rana, Sandeep; Blowers, Elizabeth C; Natarajan, Amarnath

    2015-01-01

    Adenosine 5'-monophosphate activated protein kinase (AMPK) is a master sensor of cellular energy status that plays a key role in the regulation of whole-body energy homeostasis. AMPK is a serine/threonine kinase that is activated by upstream kinases LKB1, CaMKK?, and Tak1, among others. AMPK exists as ??? trimeric complexes that are allosterically regulated by AMP, ADP, and ATP. Dysregulation of AMPK has been implicated in a number of metabolic diseases including type 2 diabetes mellitus and obesity. Recent studies have associated roles of AMPK with the development of cancer and neurological disorders, making it a potential therapeutic target to treat human diseases. This review focuses on the structure and function of AMPK, its role in human diseases, and its direct substrates and provides a brief synopsis of key AMPK modulators and their relevance in human diseases. PMID:25122135

  9. Diagnostic Value of Serum Adenosine Deaminase (ADA) Level for Pulmonary Tuberculosis

    PubMed Central

    Salmanzadeh, Shokrollah; Tavakkol, Heshmatollah; Bavieh, Khalid; Alavi, Seyed Mohammad

    2015-01-01

    Background: Diagnosis of tuberculosis (TB) is not always easy, thus employing methods with a short duration and acceptable sensitivity and specificity is necessary to diagnose TB. Objectives: The aim of this study was to investigate the diagnostic value of serum adenosine deaminase (ADA) level for diagnosis of pulmonary tuberculosis. Patients and Methods: A total of 160 sex and age-matched subjects were included in this study, and were divided to four groups; forty patients with pulmonary tuberculosis (PTB) diagnosed based on the national TB program (NTP), forty patients with non-tuberculosis bacterial pneumonia, forty patients with lung cancer and forty people who were healthy in every respect. Serum adenosine deaminase activity in patients of each group was measured by the Giusti and Galanti calorimetry method using a commercial kit (Diazyme, USA). The ANOVA analysis was used to compare groups for quantitative variables. Results: Mean serum ADA level in the PTB group was clearly higher than the mean serum ADA in the other three groups. Mean serum ADA was 26 IU/L in PTB patients, 19.48 IU/L in patients with pneumonia, 15.8 IU/L in patients with lung cancer, and 10.7 IU/L in the control group (P < 0.05). In regard to the cut off value of 26 IU/L for ADA in patients with PTB sensitivity and specificity was defined as 35% and 91%, respectively. Conclusions: Serum ADA activity with high specificity percentage may be a useful alternative test in restricted resource areas to rule out diagnosis of PTB. However, serum ADA activity is not a useful tool for TB diagnosis. PMID:25861440

  10. Identification and Characterization of Two Adenosine Phosphorylase Activities in Mycobacterium smegmatis?

    PubMed Central

    Buckoreelall, Kajal; Wilson, Landon; Parker, William B.

    2011-01-01

    Purine nucleoside phosphorylase (PNP) is an important enzyme in purine metabolism and cleaves purine nucleosides to their respective bases. Mycobacterial PNP is specific for 6-oxopurines and cannot account for the adenosine (Ado) cleavage activity that has been detected in M. tuberculosis and M. smegmatis cultures. In the current work, two Ado cleavage activities were identified from M. smegmatis cell extracts. The first activity was biochemically determined to be a phosphorylase that could reversibly catalyze adenosine + phosphate ? adenine + alpha-d-ribose-1-phosphate. Our purification scheme led to a 30-fold purification of this activity, with the removal of more than 99.9% of total protein. While Ado was the preferred substrate, inosine and guanosine were also cleaved, with 43% and 32% of the Ado activity, respectively. Our data suggest that M. smegmatis expresses two PNPs: a previously described trimeric PNP that can cleave inosine and guanosine only and a second, novel PNP (Ado-PNP) that can cleave Ado, inosine, and guanosine. Ado-PNP had an apparent Km (Km app) of 98 ± 6 ?M (with Ado) and a native molecular mass of 125 ± 7 kDa. The second Ado cleavage activity was identified as 5?-methylthioadenosine phosphorylase (MTAP) based on its biochemical properties and mass spectrometry analysis. Our study marks the first report of the existence of MTAP in any bacterium. Since human cells do not readily convert Ado to Ade, an understanding of the substrate preferences of these enzymes could lead to the identification of Ado analogs that could be selectively activated to toxic products in mycobacteria. PMID:21821769

  11. Role of cyclic nucleotides in vasodilations of the rat thoracic aorta induced by adenosine analogues

    PubMed Central

    Hourani, Susanna M O; Boon, Katherine; Fooks, Helen M; Prentice, Deborah J

    2001-01-01

    Although adenosine analogues such as 5?-N-ethylcarboxamidoadenosine (NECA) relax the rat thoracic aorta in a partially endothelium-dependent manner via adenosine A2A receptors, others such as N6-R-phenylisopropyladenosine (R-PIA) act via an endothelium-independent, antagonist-insensitive mechanism. The role of cyclic nucleotides in these relaxations was investigated in isolated aortic rings using inhibitors of adenylate and guanylate cyclases as well as subtype-selective phosphodiesterase inhibitors. The adenylate cyclase inhibitor 9-(tetrahydro-2-furanyl)-9H-purin-6-amine (SQ?22536; 100??M) significantly inhibited responses to NECA, but not responses to R-PIA. The type IV (cyclic AMP-selective) phosphodiesterase inhibitor 4-[(3-butoxy-4-methoxyphenyl)methyl]-2-imidazolidinone (RO?20-1724; 30??M) significantly enhanced responses to NECA and to a lesser extent those to R-PIA. The guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3a]quinoxalin-1-one (ODQ; 100??M) significantly inhibited responses to NECA and acetylcholine but not responses to R-PIA. The selective phosphodiesterase V (cyclic GMP-selective) inhibitors, zaprinast (10??M) and 4-{[3?,4?-(methylenedioxy)benzyl]amino}-6-methoxyquinazoline (MMQ; 1??M), had no significant effect on responses to either NECA or R-PIA, but enhanced responses to acetylcholine. These results are consistent with the effects of NECA being via activation of endothelial receptors to release NO which stimulates guanylate cyclase, as well as smooth muscle receptors coupled to stimulation of adenylate cyclase. The lack of effect of zaprinast and MMQ on responses to NECA are likely to be due to simultaneous activation of both adenylate and guanylate cyclases in the smooth muscle, as cyclic AMP reduces the sensitivity of phosphodiesterase V to inhibitors. These results also suggest that the effects of R-PIA are via neither of these mechanisms. PMID:11454656

  12. Overexpression of Adenosine A2A Receptors in Rats: Effects on Depression, Locomotion, and Anxiety

    PubMed Central

    Coelho, Joana E.; Alves, Pedro; Canas, Paula M.; Valadas, Jorge S.; Shmidt, Tatiana; Batalha, Vânia L.; Ferreira, Diana G.; Ribeiro, Joaquim A.; Bader, Michael; Cunha, Rodrigo A.; do Couto, Frederico Simões; Lopes, Luísa V.

    2014-01-01

    Adenosine A2A receptors (A2AR) are a sub-type of receptors enriched in basal ganglia, activated by the neuromodulator adenosine, which interact with dopamine D2 receptors. Although this reciprocal antagonistic interaction is well-established in motor function, the outcome in dopamine-related behaviors remains uncertain, in particular in depression and anxiety. We have demonstrated an upsurge of A2AR associated to aging and chronic stress. Furthermore, Alzheimer’s disease patients present A2AR accumulation in cortical areas together with depressive signs. We now tested the impact of overexpressing A2AR in forebrain neurons on dopamine-related behavior, namely depression. Adult male rats overexpressing human A2AR under the control of CaMKII promoter [Tg(CaMKII-hA2AR)] and aged-matched wild-types (WT) of the same strain (Sprague-Dawley) were studied. The forced swimming test (FST), sucrose preference test (SPT), and the open-field test (OFT) were performed to evaluate behavioral despair, anhedonia, locomotion, and anxiety. Tg(CaMKII-hA2AR) animals spent more time floating and less time swimming in the FST and presented a decreased sucrose preference at 48?h in the SPT. They also covered higher distances in the OFT and spent more time in the central zone than the WT. The results indicate that Tg(CaMKII-hA2AR) rats exhibit depressive-like behavior, hyperlocomotion, and altered exploratory behavior. This A2AR overexpression may explain the depressive signs found in aging, chronic stress, and Alzheimer’s disease. PMID:24982640

  13. Adenosine A2A receptor modulation of juvenile female rat skeletal muscle microvessel permeability

    PubMed Central

    Wang, Jianjie; Huxley, Virginia H.

    2015-01-01

    Little is known of the regulation of skeletal muscle microvascular exchange under resting or stimulating conditions. Adenosine (ADO) levels in skeletal muscle increase during physiological (exercise) and pathological (hypoxia, inflammation, and ischemia) conditions. Later stages of these pathologies are characterized by the loss of vascular barrier integrity. This study focused on determining which ADO receptor mediates the robust reduction in microvessel permeability to rat serum albumin (PsRSA) observed in juvenile female rats. In microvessels isolated from abdominal skeletal muscle, ADO suffusion induced a concentration-dependent reduction in arteriolar [log(IC50) = ?9.8 ± 0.2 M] and venular [log(IC50) = ?8.4 ± 0.2 M] PsRSA. RT-PCR and immunoblot analysis demonstrated mRNA and protein expression of ADO A1, A2A, A2B, and A3 receptors in both vessel types, and immunofluorescence assay revealed expression of the four subtype receptors in the microvascular walls (endothelium and smooth muscle). PsRSA responses of arterioles and venules to ADO were blocked by 8-(p-sulphophenyl)theophylline, a nonselective A1 and A2 antagonist. An A2A agonist, CGS21680, was more potent than the A1 agonist, cyclopentyladenosine, or the most-selective A2B agonist, 5?-(N-ethylcarboxamido)adenosine. The ability of CGS21680 or ADO to reduce PsRSA was abolished by the A2A antagonist, ZM241385. An adenylyl cyclase inhibitor, SQ22536, blocked the permeability response to ADO. In aggregate, these results demonstrate that, in juvenile females (before the production of the reproductive hormones), ADO enhances skeletal muscle arteriole and venule barrier function predominantly via A2A receptors using activation of adenylyl cyclase-signaling mechanisms. PMID:16815983

  14. Adenosine Kinase Modulates Root Gravitropism and Cap Morphogenesis in Arabidopsis1[W][OA

    PubMed Central

    Young, Li-Sen; Harrison, Benjamin R.; U.M., Narayana Murthy; Moffatt, Barbara A.; Gilroy, Simon; Masson, Patrick H.

    2006-01-01

    Adenosine kinase (ADK) is a key enzyme that regulates intra- and extracellular levels of adenosine, thereby modulating methyltransferase reactions, production of polyamines and secondary compounds, and cell signaling in animals. Unfortunately, little is known about ADK's contribution to the regulation of plant growth and development. Here, we show that ADK is a modulator of root cap morphogenesis and gravitropism. Upon gravistimulation, soluble ADK levels and activity increase in the root tip. Mutation in one of two Arabidopsis (Arabidopsis thaliana) ADK genes, ADK1, results in cap morphogenesis defects, along with alterations in root sensitivity to gravistimulation and slower kinetics of root gravitropic curvature. The kinetics defect can be partially rescued by adding spermine to the growth medium, whereas the defects in cap morphogenesis and gravitropic sensitivity cannot. The root morphogenesis and gravitropism defects of adk1-1 are accompanied by altered expression of the PIN3 auxin efflux facilitator in the cap and decreased expression of the auxin-responsive DR5-GUS reporter. Furthermore, PIN3 fails to relocalize to the bottom membrane of statocytes upon gravistimulation. Consequently, adk1-1 roots cannot develop a lateral auxin gradient across the cap, necessary for the curvature response. Interestingly, adk1-1 does not affect gravity-induced cytoplasmic alkalinization of the root statocytes, suggesting either that ADK1 functions between cytoplasmic alkalinization and PIN3 relocalization in a linear pathway or that the pH and PIN3-relocalization responses to gravistimulation belong to distinct branches of the pathway. Our data are consistent with a role for ADK and the S-adenosyl-l-methionine pathway in the control of root gravitropism and cap morphogenesis. PMID:16891550

  15. Purification, properties and substrate specificity of adenosine triphosphate sulphurylase from spinach leaf tissue

    PubMed Central

    Shaw, W. H.; Anderson, J. W.

    1972-01-01

    1. ATP sulphurylase was purified up to 1000-fold from spinach leaf tissue. Activity was measured by sulphate-dependent [32P]PPi–ATP exchange. The enzyme was separated from Mg2+-requiring alkaline pyrophosphatase (which interferes with the PPi–ATP-exchange assay) and from other PPi–ATP-exchange activities. No ADP sulphurylase activity was detected. 2. Sulphate was the only form of inorganic sulphur that catalysed PPi–ATP exchange; Km (sulphate) was 3.1mm, Km (ATP) was 0.35mm and the pH optimum was 7.5–9.0. The enzyme was insensitive to thiol-group reagents and required either Mg2+ or Co2+ for activity. 3. The enzyme catalysed [32P]PPi–dATP exchange; Km (dATP) was 0.84mm and V (dATP) was 30% of V (ATP). Competition between ATP and dATP was demonstrated. 4. Selenate catalysed [32P]PPi–ATP exchange and competed with sulphate; Km (selenate) was 1.0mm and V (selenate) was 30% of V (sulphate). No AMP was formed with selenate as substrate. Molybdate did not catalyse PPi–ATP exchange, but AMP was formed. 5. Synthesis of adenosine 5?-[35S]sulphatophosphate was demonstrated by coupling purified ATP sulphurylase and Mg2+-dependent alkaline pyrophosphatase (also prepared from spinach) with [35S]sulphate and ATP as substrates; adenosine 5?-sulphatophosphate was not synthesized in the absence of pyrophosphatase. Some parameters of the coupled system are reported. PMID:5073745

  16. Subcellular localization of adenosine A(1) receptors in nerve terminals and synapses of the rat hippocampus.

    PubMed

    Rebola, Nelson; Pinheiro, Paulo C; Oliveira, Catarina R; Malva, João O; Cunha, Rodrigo A

    2003-10-10

    Adenosine is a neuromodulator in the CNS that mainly acts through pre- and postsynaptic A(1) receptors to inhibit the release of excitatory neurotransmitters and NMDA receptor function. This might result from a highly localized distribution of A(1) receptors in the active zone and postsynaptic density of CNS synapses that we now investigated in the rat hippocampus. The binding density of the selective A(1) receptor antagonist, [3H]1,3-dipropyl-8-cyclopentylxanthine ([3H]DPCPX), was enriched in membranes from Percoll-purified nerve terminals (B(max)=1839+/-52 fM/mg protein) compared to total membranes from the hippocampus (B(max)=984+/-31 fM/mg protein), the same occurring with A(1) receptor immunoreactivity. [3H]DPCPX binding occurred mainly to the plasma membrane rather than to intracellular sites, since the binding of the membrane permeable A(1) receptor ligand [3H]DPCPX to intact hippocampal nerve terminals (B(max)=1901+/-192 fM/mg protein) was markedly reduced (B(max)=321+/-30 fM/mg protein) by the membrane impermeable adenosine receptor antagonist, 8-sulfophenyltheophilline (25 microM). Further subcellular fractionation of hippocampal nerve terminals revealed that A(1) receptor immunoreactivity was strategically located in the active zone of presynaptic nerve terminals, as expected to understand the efficiency of A(1) receptors to depress neurotransmitter release. A(1) Receptors were also present in nerve terminals outside the active zone in accordance with the existence of a presynaptic A(1) receptor reserve. Finally, A(1) receptor immunoreactivity was evident in the postsynaptic density together with NMDA receptor subunits 1, 2A and 2B and with N-and P/Q-type calcium channel immunoreactivity, emphasizing the importance of A(1) receptors in the control of dendritic integration. PMID:14499945

  17. Radiation damage of DNA constituents: ESR study of the adenosine:5-iodouracil cocrystal

    SciTech Connect

    Zamorano, R.

    1986-01-01

    Single cocrystals of adenosine:5-iodouracil and partially deuterated adenosine:5-iodouracil were irradiated at 4.2K, 77K, and 300K with x-rays from a 3Mev Van de Graaff electron accelerator. Several types of free radicals were produced by the radiation and were studied by X-Band and Q-Band ESR from 77K to 300K. Six radicals were identified. Two electron addition products (radicals I1 and As1) and one electron abstraction product (radical 12) are stabilized at 77K. At room temperature two hydrogen addition radicals (I3 and As2) and a singlet radical (As3) are stabilized. Upon annealing to 165K after low temperature irradiation, radicals I1 and I2 decay to nonparamagnetic species. Radical As1 remains stable from 77K to 240K. From 240K to 300K the As1 radical decays and radicals As2 and I3 gradually grow in. Irradiation and observation at room temperature produces predominantly a singlet radical (As3). The electron addition radical, I1, is a sigma*-type radical that presents the unpaired electron spin density localized mainly on the iodine atom. This radical does not de-halogenate, to produce the reactive uracilyl radical, but instead it decays into a non paramagnetic species when annealed from 77K to 300K. The low temperature radical population obtained in this cocrystal and the subsequent radical reactions upon annealing, contradict the hypothesis that, in the presence of purine:pyrimidine stacking interactions, electrons are transferred to the pyrimidines while holes are transferred to the purines.

  18. Aptamer fluorescence anisotropy sensors for adenosine triphosphate by comprehensive screening tetramethylrhodamine labeled nucleotides.

    PubMed

    Zhao, Qiang; Lv, Qin; Wang, Hailin

    2015-08-15

    We previously reported a fluorescence anisotropy (FA) approach for small molecules using tetramethylrhodamine (TMR) labeled aptamer. It relies on target-binding induced change of intramolecular interaction between TMR and guanine (G) base. TMR-labeling sites are crucial for this approach. Only terminal ends and thymine (T) bases could be tested for TMR labeling in our previous work, possibly causing limitation in analysis of different targets with this FA strategy. Here, taking the analysis of adenosine triphosphate (ATP) as an example, we demonstrated a success of conjugating TMR on other bases of aptamer adenine (A) or cytosine (C) bases and an achievement of full mapping various labeling sites of aptamers. We successfully constructed aptamer fluorescence anisotropy (FA) sensors for adenosine triphosphate (ATP). We conjugated single TMR on adenine (A), cytosine (C), or thymine (T) bases or terminals of a 25-mer aptamer against ATP and tested FA responses of 14 TMR-labeled aptamer to ATP. The aptamers having TMR labeled on the 16th base C or 23rd base A were screened out and exhibited significant FA-decreasing or FA-increasing responses upon ATP, respectively. These two favorable TMR-labeled aptamers enabled direct FA sensing ATP with a detection limit of 1µM and the analysis of ATP in diluted serum. The comprehensive screening various TMR labeling sites of aptamers facilitates the successful construction of FA sensors using TMR-labeled aptamers. It will expand application of TMR-G interaction based aptamer FA strategy to a variety of targets. PMID:25814408

  19. Adenosine Analogues as Inhibitors of Trypanosoma brucei Phosphoglycerate Kinase: Elucidation of a Novel Binding Mode for a 2-Amino-N6-Substituted

    E-print Network

    Gelb, Michael

    of adenosine analogues as drugs against African trypanosomiasis, N6 -, 2-amino-N6 -, and N2 -substituted mode. Introduction African trypanosomiasis is a devastating parasitic disease that affects more than

  20. N6-(?2-Isopentenyl)adenosine: Its Occurrence as a Free Nucleoside in an Autonomous Strain of Tobacco Tissue 12

    PubMed Central

    Dyson, W. H.; Hall, R. H.

    1972-01-01

    Cytokinins from both the free nucleoside pool and the transfer RNA have been isolated and identified in a habituated strain of tobacco pith callus (Nicotiana tabacum [L] var. Wisconsin 38). The transfer RNA of this strain contains both N6-(?2-isopentenyl) adenosine and N6-(4-hydroxy-3-methylbut-2-cis-enyl) adenosine. The trans-hydroxylated derivative is absent from the transfer RNA of this dark-grown tissue. N6-(?2-Isopentenyl)-adenosine was identified as a component of the free nucleoside pool in concentrations of about 10 micrograms per kilogram of tissue. The cytokinin-requiring tissue grown in the presence of N6-furfurylaminopurine contains less than 85 nanograms per kilogram of N6-(?2-isopentenyl) adenosine. This is the detectable limit under the conditions of the experiment. PMID:16658228

  1. Astrocyte-Derived Adenosine and A1 Receptor Activity Contribute to Sleep Loss-Induced Deficits in Hippocampal Synaptic Plasticity and Memory in Mice

    E-print Network

    Florian, Cédrick

    Sleep deprivation (SD) can have a negative impact on cognitive function, but the mechanism(s) by which SD modulates memory remains unclear. We have previously shown that astrocyte-derived adenosine is a candidate molecule ...

  2. Coronary vasodilator reserve. Comparison of the effects of papaverine and adenosine on coronary flow, ventricular function, and myocardial metabolism.

    PubMed

    Christensen, C W; Rosen, L B; Gal, R A; Haseeb, M; Lassar, T A; Port, S C

    1991-01-01

    To evaluate coronary flow reserve during cardiac catheterization, intracoronary adenosine and papaverine have been used in the clinical setting. Although papaverine maximizes coronary blood flow, it induces several toxic side effects that reduce its desirability as a coronary dilator. This investigation was designed to compare the subselective intracoronary administration of papaverine with that of adenosine in an animal model. In dogs (n = 34), we studied the effects of each agent on hemodynamics, regional myocardial blood flow, contractility (sonomicrometric and echocardiographic), metabolism (coronary arterial and venous lactate and tissue high-energy phosphates), and electrocardiographic (ST and QT intervals) parameters. Barbiturate and morphine anesthesia/analgesia was induced, and a left thoracotomy was performed. An arterial shunt was created from the left carotid artery to the left anterior descending coronary artery. Two separate groups were studied: group 1 (n = 16) for regional myocardial blood flow and mechanical function and group 2 (n = 18) for biochemical measurements. Adenosine (67 +/- 2 micrograms/min) or papaverine (6 +/- 1 mg/min) was infused into the coronary shunt at a rate of 0.5 + 0.1 ml/min for a maximum duration of 3.5 minutes. Regional myocardial blood flows were determined at control (predrug) and maximal coronary flow using radiolabeled microspheres. All hemodynamic, wall motion, biochemical, and electrocardiographic parameters were also measured at these times. Both drugs produced comparable increases in total and regional coronary blood flows (adenosine, 1.21 +/- 0.15 to 4.83 +/- 0.36 ml/min/g; papaverine, 1.21 +/- 0.05 to 4.89 +/- 0.28 ml/min/g) upon infusion into the left anterior descending coronary artery. Papaverine produced significant (p less than 0.05) changes in subendocardial ST segment electrocardiogram (-2.5 mm), QT prolongation (8 +/- 2%), myocardial creatine phosphate (47% decrease), and coronary sinus serum lactate (277% increase) compared with control. In addition, intracoronary papaverine induced an abnormal contractile pattern. No significant changes in any of these parameters (i.e., ST segment, QT prolongation, myocardial creatine phosphate level, or lactate level) were observed with intracoronary adenosine infusions. We conclude that intracoronary adenosine is comparable to papaverine for maximizing coronary blood flow without the deleterious properties observed with intracoronary papaverine. PMID:1984887

  3. Activation of adenosine low-affinity A3 receptors inhibits the enteric short interplexus neural circuit triggered by histamine.

    PubMed

    Bozarov, Andrey; Wang, Yu-Zhong; Yu, Jun Ge; Wunderlich, Jacqueline; Hassanain, Hamdy H; Alhaj, Mazin; Cooke, Helen J; Grants, Iveta; Ren, Tianhua; Christofi, Fievos L

    2009-12-01

    We tested the novel hypothesis that endogenous adenosine (eADO) activates low-affinity A3 receptors in a model of neurogenic diarrhea in the guinea pig colon. Dimaprit activation of H2 receptors was used to trigger a cyclic coordinated response of contraction and Cl(-) secretion. Contraction-relaxation was monitored by sonomicrometry (via intracrystal distance) simultaneously with short-circuit current (I(sc), Cl(-) secretion). The short interplexus reflex coordinated response was attenuated or abolished by antagonists at H2 (cimetidine), 5-hydroxytryptamine 4 receptor (RS39604), neurokinin-1 receptor (GR82334), or nicotinic (mecamylamine) receptors. The A1 agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA) abolished coordinated responses, and A1 antagonists could restore normal responses. A1-selective antagonists alone [8-cyclopentyltheophylline (CPT), 1,3-dipropyl-8-(2-amino-4-chlorophenyl)xanthine (PACPX), or 8-cyclopentyl-N(3)-[3-(4-(fluorosulfonyl)benzoyloxy)propyl]-xanthine (FSCPX)] caused a concentration-dependent augmentation of crypt cell secretion or contraction and acted at nanomolar concentrations. The A3 agonist N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) abolished coordinated responses and the A3 antagonist 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS1191) could restore and further augment responses. The IB-MECA effect was resistant to knockdown of adenosine A1 receptor with the irreversible antagonist FSCPX; the IC(50) for IB-MECA was 0.8 microM. MRS1191 alone could augment or unmask coordinated responses to dimaprit, and IB-MECA suppressed them. MRS1191 augmented distension-evoked reflex I(sc) responses. Adenosine deaminase mimicked actions of adenosine receptor antagonists. A3 receptor immunoreactivity was differentially expressed in enteric neurons of different parts of colon. After tetrodotoxin, IB-MECA caused circular muscle relaxation. The data support the novel concept that eADO acts at low-affinity A3 receptors in addition to high-affinity A1 receptors to suppress coordinated responses triggered by immune-histamine H2 receptor activation. The short interplexus circuit activated by histamine involves adenosine, acetylcholine, substance P, and serotonin. We postulate that A3 receptor modulation may occur in gut inflammatory diseases or allergic responses involving mast cell and histamine release. PMID:19808660

  4. Wireless Instantaneous Neurotransmitter Concentration System–based amperometric detection of dopamine, adenosine, and glutamate for intraoperative neurochemical monitoring

    PubMed Central

    Agnesi, Filippo; Tye, Susannah J.; Bledsoe, Jonathan M.; Griessenauer, Christoph J.; Kimble, Christopher J.; Sieck, Gary C.; Bennet, Kevin E.; Garris, Paul A.; Blaha, Charles D.; Lee, Kendall H.

    2009-01-01

    Object In a companion study, the authors describe the development of a new instrument named the Wireless Instantaneous Neurotransmitter Concentration System (WINCS), which couples digital telemetry with fast-scan cyclic voltammetry (FSCV) to measure extracellular concentrations of dopamine. In the present study, the authors describe the extended capability of the WINCS to use fixed potential amperometry (FPA) to measure extracellular concentrations of dopamine, as well as glutamate and adenosine. Compared with other electrochemical techniques such as FSCV or high-speed chronoamperometry, FPA offers superior temporal resolution and, in combination with enzyme-linked biosensors, the potential to monitor nonelectroactive analytes in real time. Methods The WINCS design incorporated a transimpedance amplifier with associated analog circuitry for FPA; a microprocessor; a Bluetooth transceiver; and a single, battery-powered, multilayer, printed circuit board. The WINCS was tested with 3 distinct recording electrodes: 1) a carbon-fiber microelectrode (CFM) to measure dopamine; 2) a glutamate oxidase enzyme-linked electrode to measure glutamate; and 3) a multiple enzyme-linked electrode (adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase) to measure adenosine. Proof-of-principle analyses included noise assessments and in vitro and in vivo measurements that were compared with similar analyses by using a commercial hardwired electrochemical system (EA161 Picostat, eDAQ; Pty Ltd). In urethane-anesthetized rats, dopamine release was monitored in the striatum following deep brain stimulation (DBS) of ascending dopaminergic fibers in the medial forebrain bundle (MFB). In separate rat experiments, DBS-evoked adenosine release was monitored in the ventrolateral thalamus. To test the WINCS in an operating room setting resembling human neurosurgery, cortical glutamate release in response to motor cortex stimulation (MCS) was monitored using a large-mammal animal model, the pig. Results The WINCS, which is designed in compliance with FDA-recognized consensus standards for medical electrical device safety, successfully measured dopamine, glutamate, and adenosine, both in vitro and in vivo. The WINCS detected striatal dopamine release at the implanted CFM during DBS of the MFB. The DBS-evoked adenosine release in the rat thalamus and MCS-evoked glutamate release in the pig cortex were also successfully measured. Overall, in vitro and in vivo testing demonstrated signals comparable to a commercial hardwired electrochemical system for FPA. Conclusions By incorporating FPA, the chemical repertoire of WINCS-measurable neurotransmitters is expanded to include glutamate and other nonelectroactive species for which the evolving field of enzyme-linked biosensors exists. Because many neurotransmitters are not electrochemically active, FPA in combination with enzyme-linked microelectrodes represents a powerful intraoperative tool for rapid and selective neurochemical sampling in important anatomical targets during functional neurosurgery. PMID:19425899

  5. Activation of adenosine low-affinity A3 receptors inhibits the enteric short interplexus neural circuit triggered by histamine

    PubMed Central

    Bozarov, Andrey; Wang, Yu-Zhong; Yu, Jun Ge; Wunderlich, Jacqueline; Hassanain, Hamdy H.; Alhaj, Mazin; Cooke, Helen J.; Grants, Iveta; Ren, Tianhua

    2009-01-01

    We tested the novel hypothesis that endogenous adenosine (eADO) activates low-affinity A3 receptors in a model of neurogenic diarrhea in the guinea pig colon. Dimaprit activation of H2 receptors was used to trigger a cyclic coordinated response of contraction and Cl? secretion. Contraction-relaxation was monitored by sonomicrometry (via intracrystal distance) simultaneously with short-circuit current (Isc, Cl? secretion). The short interplexus reflex coordinated response was attenuated or abolished by antagonists at H2 (cimetidine), 5-hydroxytryptamine 4 receptor (RS39604), neurokinin-1 receptor (GR82334), or nicotinic (mecamylamine) receptors. The A1 agonist 2-chloro-N6-cyclopentyladenosine (CCPA) abolished coordinated responses, and A1 antagonists could restore normal responses. A1-selective antagonists alone [8-cyclopentyltheophylline (CPT), 1,3-dipropyl-8-(2-amino-4-chlorophenyl)xanthine (PACPX), or 8-cyclopentyl-N3-[3-(4-(fluorosulfonyl)benzoyloxy)propyl]-xanthine (FSCPX)] caused a concentration-dependent augmentation of crypt cell secretion or contraction and acted at nanomolar concentrations. The A3 agonist N6-(3-iodobenzyl)-adenosine-5?-N-methyluronamide (IB-MECA) abolished coordinated responses and the A3 antagonist 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(±)-dihydropyridine-3,5-dicarboxylate (MRS1191) could restore and further augment responses. The IB-MECA effect was resistant to knockdown of adenosine A1 receptor with the irreversible antagonist FSCPX; the IC50 for IB-MECA was 0.8 ?M. MRS1191 alone could augment or unmask coordinated responses to dimaprit, and IB-MECA suppressed them. MRS1191 augmented distension-evoked reflex Isc responses. Adenosine deaminase mimicked actions of adenosine receptor antagonists. A3 receptor immunoreactivity was differentially expressed in enteric neurons of different parts of colon. After tetrodotoxin, IB-MECA caused circular muscle relaxation. The data support the novel concept that eADO acts at low-affinity A3 receptors in addition to high-affinity A1 receptors to suppress coordinated responses triggered by immune-histamine H2 receptor activation. The short interplexus circuit activated by histamine involves adenosine, acetylcholine, substance P, and serotonin. We postulate that A3 receptor modulation may occur in gut inflammatory diseases or allergic responses involving mast cell and histamine release. PMID:19808660

  6. Molecular Characterization of Adenosine 5?-monophosphate Deaminase—The Key Enzyme Responsible for the Umami Taste of Nori ( Porphyra yezoensis Ueda, Rhodophyta)

    Microsoft Academic Search

    Seiko Minami; Minoru Sato; Yoshihiro Shiraiwa; Koji Iwamoto

    The enzyme adenosine 5?-monophosphate deaminase (AMPD, EC 3.5.4.6) catalyzes the conversion of adenosine 5?-monophosphate\\u000a to inosine 5?-mononucleotide (IMP). IMP is generally known as the compound responsible for the umami taste of the edible red alga Porphyra yezoensis Ueda that is known in Japan as nori. Therefore, we suspect that AMPD plays a key role in providing a favorable nori taste.

  7. Adenosine A1 receptor activation is arrhythmogenic in the developing heart through NADPH oxidase\\/ERK and PLC\\/PKC-dependent mechanisms

    Microsoft Academic Search

    Elodie Robin; Jessica Sabourin; Rachel Benoit; Sarah Pedretti; Eric Raddatz

    2011-01-01

    Whether adenosine, a crucial regulator of the developing cardiovascular system, can provoke arrhythmias in the embryonic\\/fetal heart remains controversial. Here, we aimed to establish a mechanistic basis of how an adenosinergic stimulation alters function of the developing heart. Spontaneously beating hearts or dissected atria and ventricle obtained from 4-day-old chick embryos were exposed to adenosine or specific agonists of the

  8. Regulation of p42\\/p44 MAPK and p38 MAPK by the adenosine A 1 receptor in DDT 1MF2 cells

    Microsoft Academic Search

    Alex J. Robinson; John M. Dickenson

    2001-01-01

    The mitogen-activated protein kinase (MAPK) family consists of the p42\\/p44 MAPKs and the stress-activated protein kinases, c-Jun N-terminal kinase (JNK) and p38 MAPK. We have previously reported that the human adenosine A1 receptor stimulates p42\\/p44 MAPK in transfected Chinese hamster ovary cells. In this study, we have investigated whether the endogenous adenosine A1 receptor in the smooth muscle cell line,

  9. Ischemic preconditioning prevents the impairment of hypoxic coronary vasodilatation caused by ischemia/reperfusion: role of adenosine A1/A3 and bradykinin B2 receptor activation.

    PubMed

    Giannella, E; Mochmann, H C; Levi, R

    1997-09-01

    We previously reported that hypoxic coronary vasodilatation (HCVD) is initiated by endothelial NO and sustained by adenosine. Prolonged ischemia/reperfusion impairs endothelium-dependent coronary vasodilatation, whereas transient ischemia (ie, preconditioning) protects the myocardium from subsequent ischemic events. Accordingly, we assessed whether prolonged ischemia/reperfusion impairs HCVD and whether preconditioning prevents this dysfunction. HCVD, elicited in isolated guinea pig hearts by a 1-minute exposure to 100% N2, consisted of an approximately 70% increase in coronary flow associated with enhanced nitrite/nitrate and adenosine overflow (+40% and 5-fold, respectively). After 30-minute global ischemia and 20-minute reperfusion, HCVD was decreased by approximately 60%, and the increases in nitrite/nitrate and adenosine overflow were abolished. Preconditioning (ie, three cycles of 5-minute global ischemia+5-minute reperfusion) prevented the impairment of HCVD and fully restored the increase in nitrite/nitrate overflow, but not that of adenosine. The protective effect of preconditioning was mimicked by perfusion with the adenosine A1 receptor agonist N6-cyclopentyladenosine and prevented by the A1 receptor antagonist N-0861. In addition, the A3 receptor agonist N6-(3-iodobenzyl)adenosine-5'-N-methyl-carboxamide had a similar protective effect. The bradykinin B2 receptor antagonist HOE 140 abolished the protective effect of preconditioning, whereas the NO synthase inhibitor N(omega)-methyl-L-arginine and the cycloxygenase inhibitor indomethacin did not. Our data indicate that preconditioning restores HCVD by a process that is triggered by activation of adenosine A1/A3 and bradykinin B2 receptors. The action of bradykinin is independent of NO and prostacyclin production. Once restored by preconditioning, HCVD is mediated by NO but no longer sustained by adenosine. PMID:9285644

  10. Synthesis and biological effects of a new series of 2-amino-3-benzoylthiophenes as allosteric enhancers of A 1-adenosine receptor

    Microsoft Academic Search

    Pier Giovanni Baraldi; Abdel Naser Zaid; Ilaria Lampronti; Francesca Fruttarolo; Maria Giovanna Pavani; Mojgan Aghazadhe Tabrizi; John C Shryock; Edward Leung; Romeo Romagnoli

    2000-01-01

    New derivatives of PD 81,723, an allosteric enhancer of agonist binding to the A1-adenosine receptor, have been synthesized and evaluated in an intact cell assay. Compounds 3a, 3o and 3p appeared to be more potent than PD 81,723 and at a concentration of 0.1?M caused significant reductions of cAMP content of CHO cells expressing the human A1-adenosine receptor. Compounds 4e

  11. Direct Growth Graphene on Cu Nanoparticles by Chemical Vapor Deposition as Surface-Enhanced Raman Scattering Substrate for Label-Free Detection of Adenosine

    E-print Network

    Xu, Shicai; Jiang, Shouzhen; Wang, Jihua; Wei, Jie; Xu, Shida; Liu, Hanping

    2015-01-01

    We present a graphene/Cu nanoparticle hybrids (G/CuNPs) system as a surface-enhanced Raman scattering (SERS) substrate for adenosine detection. The Cu nanoparticles wrapped around a monolayer graphene shell were directly synthesized on flat quartz by chemical vapor deposition in a mixture of methane and hydrogen. The G/CuNPs showed an excellent SERS enhancement activity for adenosine. The minimum detected concentration of the adenosine in serum was demonstrated as low as 5 nM, and the calibration curve showed a good linear response from 5 to 500 nM. The capability of SERS detection of adenosine in real normal human urine samples based on G/CuNPs was also investigated and the characteristic peaks of adenosine were still recognizable. The reproducible and the ultrasensitive enhanced Raman signals could be due to the presence of an ultrathin graphene layer. The graphene shell was able to enrich and fix the adenosine molecules, which could also efficiently maintain chemical and optical stability of G/CuNPs. Based...

  12. ?-Nicotinamide adenine dinucleotide acts at prejunctional adenosine A1 receptors to suppress inhibitory musculomotor neurotransmission in guinea pig colon and human jejunum.

    PubMed

    Wang, Guo-Du; Wang, Xi-Yu; Liu, Sumei; Xia, Yun; Zou, Fei; Qu, Meihua; Needleman, Bradley J; Mikami, Dean J; Wood, Jackie D

    2015-06-01

    Intracellular microelectrodes were used to record neurogenic inhibitory junction potentials in the intestinal circular muscle coat. Electrical field stimulation was used to stimulate intramural neurons and evoke contraction of the smooth musculature. Exposure to ?-nicotinamide adenine dinucleotide (?-NAD) did not alter smooth muscle membrane potential in guinea pig colon or human jejunum. ATP, ADP, ?-NAD, and adenosine, as well as the purinergic P2Y1 receptor antagonists MRS 2179 and MRS 2500 and the adenosine A1 receptor agonist 2-chloro-N(6)-cyclopentyladenosine, each suppressed inhibitory junction potentials in guinea pig and human preparations. ?-NAD suppressed contractile force of twitch-like contractions evoked by electrical field stimulation in guinea pig and human preparations. P2Y1 receptor antagonists did not reverse this action. Stimulation of adenosine A1 receptors with 2-chloro-N(6)-cyclopentyladenosine suppressed the force of twitch contractions evoked by electrical field stimulation in like manner to the action of ?-NAD. Blockade of adenosine A1 receptors with 8-cyclopentyl-1,3-dipropylxanthine suppressed the inhibitory action of ?-NAD on the force of electrically evoked contractions. The results do not support an inhibitory neurotransmitter role for ?-NAD at intestinal neuromuscular junctions. The data suggest that ?-NAD is a ligand for the adenosine A1 receptor subtype expressed by neurons in the enteric nervous system. The influence of ?-NAD on intestinal motility emerges from adenosine A1 receptor-mediated suppression of neurotransmitter release at inhibitory neuromuscular junctions. PMID:25813057

  13. Adenosine postconditioning protects against myocardial ischemia-reperfusion injury though modulate production of TNF-? and prevents activation of transcription factor NF-kappaB.

    PubMed

    Ke, Jian-Juan; Yu, Feng-Xu; Rao, Yan; Wang, Yan-Lin

    2011-01-01

    Adenosine serves a number of important physiological roles in the body, which is the most widely studied endogenous signal molecules, and the underlying mechanism responsible for such cardioprotection needs more understood, particularly adenosine postconditioning in myocardial ischemia/reperfusion model. In the present study we performed to investigate the inflammatory response of adenosine postconditioning on the cardiac TNF-? expression and NF-?B activation. Eighteen rats were randomly divided into 4 groups: (1) Group A: sham operation group; (2) Group B: ischemia/reperfusion group; (3) Group C: postconditioned groups, four cycles of 30-s reperfusion/30-s occlusion were started immediately after release of the index ischemia (n=6 each); (4) Group D: adenosine was infused 40 ?g kg(-1) min(-1) 5 min before the onset of reperfusion without subsequent postconditioning cycles. Hearts were removed at the termination of experiments, which were preserved in frozen tube and stored at -70°C refrigerator for Measurement of malonyldialdehyde (MDA), activities of the NF-?B and TNF-? and IL-10 assay. The results of this study indicate that adenosine postconditioning immediately after myocardial ischemia can reduce the myocardial tissue MDA generation and infarct size, improve cardiac function, which is coincidence with conventional postconditioning. The study also found that modulation of NF-?B activation and accordingly reduces inflammatory factor TNF-? expression may be a molecular mechanism of adenosine down-regulation of inflammatory cytokine production. PMID:20379781

  14. Roles for adenosine A1- and A2-receptors in the control of thyrotrophin and prolactin release from the anterior pituitary gland.

    PubMed

    Kumari, M; Buckingham, J C; Poyser, R H; Cover, P O

    1999-01-01

    Adenosine has been implicated in various aspects of pituitary function but little is known of its role in the regulation of thyrotrophin (TSH) release. This study examined the effects of adenosine deaminase (ADA, which provokes adenosine breakdown) and selective adenosine-receptor ligands on the secretion of immunoreactive (ir-) TSH and prolactin (PRL) by rat anterior pituitary segments in vitro. ADA (5 U/ml) stimulated the release of both hormones (P<0.01) as also did the selective adenosine A1-receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 0.1 & 1 nM, P<0.01); the responses to ADA were inhibited by an A1-receptor agonist, N6-cyclohexyladenosine (0.1-10 nM, P<0.01). A non-selective A1/A2-receptor agonist, N-cyclopropylcarboxamidoadenosine (1-100 nM) had mixed effects on ir-TSH release. However, the A2A-receptor selective agonist, CGS 21680 (1-100 nM) increased ir-TSH (P<0.05) and ir-PRL release (P<0.01); its effects on ir-TSH were blocked by concentrations of DPCPX (100 nM, P<0.01) sufficient to antagonize A2-receptors. These data suggest that adenosine acts via A1-receptors to tonically suppress ir-PRL and ir-TSH release but that A2A-receptor activation enhances the release of both hormones. PMID:9930581

  15. Serum glucose and insulin response in rats administered with sucrose or starch containing adenosine, inosine or cytosine.

    PubMed

    Fukumori, Y; Maeda, N; Takeda, H; Onodera, S; Shiomi, N

    2000-02-01

    Blood glucose and insulin responses and gastric emptying were examined in rats intubated with sucrose or soluble starch that contained adenosine, inosine and cytosine. The increase in serum glucose and insulin levels in the rats following loading with sucrose (2.5 g/kg of body weight) or soluble starch (1.875 g/kg of body weight) was significantly reduced by the administration of adenosine, inosine and cytosine (0.0625-0.125 g/kg of body weight). The gastric emptying rates were only marginally affected by the nucleoside administration. The activities of sucrase, maltase, isomaltase and glucoamylase in a crude preparation from the small intestinal mucosa of rats were mildly inhibited by the nucleosides. The decrease in blood glucose and insulin levels may have been in response to a decrease in glucose absorption caused by the inhibiting effect of the nucleosides on the mucosal enzymes that digest sucrose, maltose, and malto- and isomalto-oligosaccharides. PMID:10737175

  16. Distal administration of very high doses of intracoronary adenosine for the treatment of resistant no-reflow

    PubMed Central

    Movahed, Mohammad-Reza; Baweja, Gurpreet

    2008-01-01

    No-reflow is a serious condition, and is associated with substantial morbidity and mortality after percutaneous coronary intervention. The most feared complication of no-reflow is a case of no-reflow that is resistant to multiple drug therapy. This condition usually occurs in patients with distal coronary disease or high thrombus burden. In the present case, a patient with resistant no-reflow that could be reversed by distal intracoronary administration of very high doses of adenosine (1 mg) is described. Administration of very high doses of adenosine via a balloon catheter was safe and did not cause any changes in the heart rate or blood pressure. The present case is the first to be reported in the literature. PMID:19343130

  17. Conserved Seed Pairing, Often Flanked by Adenosines, Indicates that Thousands of Human Genes are MicroRNA Targets

    Microsoft Academic Search

    Benjamin P. Lewis; Christopher B. Burge; David P. Bartel

    2005-01-01

    We predict regulatory targets of vertebrate microRNAs (miRNAs) by identifying mRNAs with conserved complementarity to the seed (nucleotides 2–7) of the miRNA. An overrepresentation of conserved adenosines flanking the seed complementary sites in mRNAs indicates that primary sequence determinants can supplement base pairing to specify miRNA target recognition. In a four-genome analysis of 3? UTRs, approximately 13,000 regulatory relationships were

  18. 4-Coumarate:Coenzyme A Ligase Has the Catalytic Capacity to Synthesize and Reuse Various (Di)Adenosine Polyphosphates1

    PubMed Central

    Pietrowska-Borek, Ma?gorzata; Stuible, Hans-Peter; Kombrink, Erich; Guranowski, Andrzej

    2003-01-01

    4-Coumarate:coenzyme A ligase (4CL) is known to activate cinnamic acid derivatives to their corresponding coenzyme A esters. As a new type of 4CL-catalyzed reaction, we observed the synthesis of various mono- and diadenosine polyphosphates. Both the native 4CL2 isoform from Arabidopsis (At4CL2 wild type) and the At4CL2 gain of function mutant M293P/K320L, which exhibits the capacity to use a broader range of phenolic substrates, catalyzed the synthesis of adenosine 5?-tetraphosphate (p4A) and adenosine 5?-pentaphosphate when incubated with MgATP?2 and tripolyphosphate or tetrapolyphosphate (P4), respectively. Diadenosine 5?,5?,-P1,P4-tetraphosphate represented the main product when the enzymes were supplied with only MgATP2?. The At4CL2 mutant M293P/K320L was studied in more detail and was also found to catalyze the synthesis of additional dinucleoside polyphosphates such as diadenosine 5?,5?-P1,P5-pentaphosphate and dAp4dA from the appropriate substrates, p4A and dATP, respectively. Formation of Ap3A from ATP and ADP was not observed with either At4CL2 variant. In all cases analyzed, (di)adenosine polyphosphate synthesis was either strictly dependent on or strongly stimulated by the presence of a cognate cinnamic acid derivative. The At4CL2 mutant enzyme K540L carrying a point mutation in the catalytic center that is critical for adenylate intermediate formation was inactive in both p4A and diadenosine 5?,5?,-P1,P4-tetraphosphate synthesis. These results indicate that the cinnamoyl-adenylate intermediate synthesized by At4CL2 not only functions as an intermediate in coenzyme A ester formation but can also act as a cocatalytic AMP-donor in (di)adenosine polyphosphate synthesis. PMID:12644689

  19. The role of adenosine A 1 receptors in the interaction between amygdala and entorhinal cortex of kindled rats

    Microsoft Academic Search

    Mohammad Mohammad-Zadeh; Azam Amini; Javad Mirnajafi-Zadeh; Yaghoub Fathollahi

    2005-01-01

    In this study the effect of adenosine A1 receptors of the entorhinal cortex (EC) and amygdala on kindled seizures was investigated. Animals were kindled by daily electrical stimulation of amygdala (group 1) or EC (group 2). In the fully kindled animals, N6-cyclohexyladenosine (CHA), a selective A1 receptor agonist, and 1,3-dimethyl-8-cyclopenthylxanthine (CPT), a selective A1 receptor antagonist, were microinjected bilaterally into

  20. Inhibition of Protein Kinase C, (Sodium plus Potassium)-activated Adenosine Triphosphatase, and Sodium Pump by Synthetic Phospholipid Analogues1

    Microsoft Academic Search

    Bin Zheng; Kazuhiko Oishi; Mamoru Shoji; Wolfgang E. Berdel; Joseph Hajdu; William R. Vogler; J. F. Kuo

    1990-01-01

    The effects and modes of action of certain antineoplastic phospholipid analogues (racemic l-O-octadecyl-2-O-methyl glycero-3-phosphocho- line, BM 41.440, JH-1, CV-3988, and HePC) on (sodium plus potas- sium)-activated adenosine triphosphatase (Na,K-ATPase) and sodium pump activities were investigated. Inhibition of Na,K-ATPase in purified rat brain synaptosomal membranes by these lipids, in contrast to ouabain, was subject to membrane surface dilution and unaffected by