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1

Effects of calcium and magnesium on strontium distribution coefficients  

USGS Publications Warehouse

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.

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

1997-01-01

2

Effects of extracellular calcium and magnesium on junctional intercellular communication in human fibroblasts.  

PubMed

The role of extracellular calcium and magnesium in intercellular communication via permeable junctions was studied by measuring metabolic co-operation between ASS- and ASL- human fibroblasts. Communication through pre-existing junctions was not affected by the removal of extracellular calcium and magnesium from the medium. On the other hand, the establishment of communication through new permeable junctions, when ASS- and ASL- cells were mixed, was dependent on the presence of extracellular calcium and magnesium. PMID:6499943

Davidson, J S; Baumgarten, I M; Harley, E H

1984-12-01

3

Automatic photometric titrations of calcium and magnesium in carbonate rocks  

USGS Publications Warehouse

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.

Shapiro, L.; Brannock, W.W.

1955-01-01

4

Effects of thyroid status on renal calcium and magnesium handling.  

PubMed Central

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

McCaffrey, C; Quamme, G A

1984-01-01

5

The magnesium ion-dependent adenosine triphosphatase of myosin. Two-step processes of adenosine triphosphate association and adenosine diphosphate dissociation  

PubMed Central

The kinetics of protein-fluorescence change when rabbit skeletal myosin subfragment 1 is mixed with ATP or adenosine 5?-(3-thiotriphosphate) in the presence of Mg2+ are incompatible with a simple bimolecular association process. A substrate-induced conformation change with ?G0

Bagshaw, Clive R.; Eccleston, John F.; Eckstein, Fritz; Goody, Roger S.; Gutfreund, Herbert; Trentham, David R.

1974-01-01

6

Influence of refined cellulose on human bowel function and calcium and magnesium balance13  

Microsoft Academic Search

The effect of cellulose purified from wood pulp on wet and dry stool weights, gastrointestinal transit time (TT), frequency of defecation, and calcium and magnesium balances was tested. Seven healthy women consumed a low fiber diet of constant composition (percentage of total kcal: 23% protein, 30% fat, 47% carbohydrate) and the same metabolically controlled diet to which 16 g of

J. L. Slavin; J. A. Marlett

7

Calcium and magnesium isotope systematics in rivers draining the Himalaya-Tibetan-Plateau region: Lithological  

E-print Network

Calcium and magnesium isotope systematics in rivers draining the Himalaya-Tibetan-Plateau region of average riverine d26 Mg values is in contrast to the main rock types (lime- stone, dolostone and silicate silicate rock of the HHCS is Ă?1.25, lower by 0.63 than the average silicate rock. These differences

Cambridge, University of

8

Computer-processed potentiometric titration for the determination of calcium and magnesium in sea water  

Microsoft Academic Search

An improved potentiometric titration method for the determination of calcium and magnesium in sea water has been newly devised. In this method, a mini-computer is used for the automation of titrations, and ion-selective electrodes are used as an end-point detector. Calcium is determined by titration with EGTA, and total alkaline earth metals (magnesium + calcium + strontium) by titration with

Satoru Kanamori; Hisashi Ikegami

1980-01-01

9

Stability and broad-sense heritability of mineral content in potato: calcium and magnesium  

Technology Transfer Automated Retrieval System (TEKTRAN)

Calcium and magnesium are two minerals with prominent roles in animal and plant metabolism. Advanced potato breeding lines were found to contain between 266 and 944 ľg per gram fresh weight of calcium and between 705 1089 ľg per gram fresh weight of magnesium. All trials had significant genotype b...

10

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

Microsoft Academic Search

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

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

1986-01-01

11

Minerals to Dairy Cows with Focus on Calcium and Magnesium Balance  

E-print Network

(0.49, 0.93, and 1.36 % of dry matter) on calcium and magnesium homeostasis was investigated in 29 fever. Finally, the effect of prepartum milking for 1 to 7 days on calcium homeostasis was investigated removal affects calcium homeostasis, but the effect on the risk of milk fever is unclear. Keywords

12

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

NASA Astrophysics Data System (ADS)

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.

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

2007-04-01

13

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

USGS Publications Warehouse

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.

Shapiro, Leonard; Brannock, Walter Wallace

1957-01-01

14

Original article Effect of calcium and magnesium ions on the intestinal  

E-print Network

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

Paris-Sud XI, UniversitĂŠ de

15

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

NASA Astrophysics Data System (ADS)

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 4ˇ2H 2O (brushite), CaHPO 4 (monetite), Ca 3(PO 4) 2ˇ xH 2O (amorphous calcium phosphate), MgNH 4PO 4ˇ6H 2O (struvite), and MgHPO 4ˇ3H 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.

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

1986-04-01

16

An examination of the relationship between calcium and magnesium and hypertension  

E-print Network

AN EXAMINATION QF Tl-IE RELATIONSHIP BETWEEN CALCILIM AND MAGNESIUM AND HYPERTENSION A Thesis by MARY ELIZABETH GEORGHIADES Submitted to the Graduate College of Texas ARM University in partial Fulfillment of the requirements For the degree... of MASTER QF SCIENCE May 1988 Major Subject. : Nutrition AN EXAMINATION OF THE RELATIONSHIP BETWEEN CALCIUM AND MAGNESIUM AND HYPERTENSION A Thesis by MARY ELIZABETH GEORGH I ADES Approved as to style and content by: Karen S. Kubena (Chair...

Georghiades, Mary Elizabeth

1988-01-01

17

Nephrolithiasis in a neonate with transient renal wasting of calcium and magnesium  

Microsoft Academic Search

Following an uneventful full-term pregnancy, a 3-day-old girl presented with a focal seizure. Serological evaluation revealed\\u000a hypomagnesemia and hypocalcemia. Renal ultrasonography performed because of hematuria showed bilateral nephrolithiasis. Renal\\u000a wasting of calcium and magnesium was detected and urine citrate excretion was low. The hypocalcemia was refractory to calcium\\u000a therapy, but responded briskly to magnesium supplementation. After 8 weeks of treatment

Matthew L. Stoll; James A. Listman

2002-01-01

18

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

Microsoft Academic Search

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

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

1975-01-01

19

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

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

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

2006-01-01

20

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...

21

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...

22

Continental weathering following a Cryogenian glaciation: Evidence from calcium and magnesium isotopes  

NASA Astrophysics Data System (ADS)

A marked ocean acidification event and elevated atmospheric carbon dioxide concentrations following the extreme environmental conditions of the younger Cryogenian glaciation have been inferred from boron isotope measurements. Calcium and magnesium isotope analyses offer additional insights into the processes occurring during this time. Data from Neoproterozoic sections in Namibia indicate that following the end of glaciation the continental weathering flux transitioned from being of mixed carbonate and silicate character to a silicate-dominated one. Combined with the effects of primary dolomite formation in the cap dolostones, this caused the ocean to depart from a state of acidification and return to higher pH after climatic amelioration. Differences in the magnitude of stratigraphic isotopic changes across the continental margin of the southern Congo craton shelf point to local influences modifying and amplifying the global signal, which need to be considered in order to avoid overestimation of the worldwide chemical weathering flux.

Kasemann, Simone A.; Pogge von Strandmann, Philip A. E.; Prave, Anthony R.; Fallick, Anthony E.; Elliott, Tim; Hoffmann, Karl-Heinz

2014-06-01

23

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

NASA Astrophysics Data System (ADS)

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 4ˇ2H 2O; monetite, CaHPO 4; newberyite, MgHPO 4ˇ3H 2O and struvite, MgNH 4PO 4ˇ6H 2O. At low concentration whitlockite, Ca 9MgH(PO 4) 7, occurs with the amorphous phase previously precipitated, Ca 3(PO 4) 2ˇnH 2O. The conditions for stability are discussed and the changes observed are interpreted.

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

1988-07-01

24

Structures and stability of calcium and magnesium carbonates at mantle pressures  

NASA Astrophysics Data System (ADS)

Ab initio random structure searching (AIRSS) and density functional theory methods are used to predict structures of calcium and magnesium carbonate (CaCO3 and MgCO3) at high pressures. We find a previously unknown CaCO3 structure which is more stable than the aragonite and "post aragonite" phases in the range 32-48 GPa. At pressures from 76 GPa to well over 100 GPa the most stable phase is a previously unknown CaCO3 structure of the pyroxene type with fourfold coordinated carbon atoms. We also predict a stable structure of MgCO3 in the range 85-101 GPa. Our results lead to a revision of the phase diagram of CaCO3 over more than half the pressure range encountered within the Earth's mantle, and smaller changes to the phase diagram of MgCO3. We predict CaCO3 to be more stable than MgCO3 in the Earth's mantle above 100 GPa, and that CO2 is not a thermodynamically stable compound under deep mantle conditions. Our results have significant implications for understanding the Earth's deep carbon cycle.

Pickard, Chris J.; Needs, Richard J.

2015-03-01

25

Dietary calcium and magnesium intakes and the risk of type 2 diabetes: the Shanghai Women's Health Study123  

PubMed Central

Background: Diet plays a key role in the development of type 2 diabetes (T2D), but little is known about the contributions of specific nutrients in populations in which dietary patterns differ from Western populations. Objective: We examined associations between calcium and magnesium intakes and the risk of T2D in a Chinese population. Design: We used data from a population-based, prospective study of 64,191 women who were free of T2D or other chronic diseases at study recruitment and were living in urban Shanghai, China. Dietary intake, physical activity, and anthropometric measurements were assessed through in-person interviews. A Cox regression model was used to evaluate the association of the exposures under study with the risk of T2D. Results: An inverse association between calcium and magnesium intakes and T2D risk was observed. The relative risks for the lowest to the highest quintiles of calcium intake were 1.00, 0.82, 0.73, 0.67, and 0.74 (P for trend < 0.001), and for magnesium they were 1.00, 0.84, 0.84, 0.79, and 0.86 (P for trend < 0.001). Milk intake was also inversely associated with the risk of T2D. Conclusion: Our data suggest that calcium and magnesium intakes may protect against the development of T2D in this population. PMID:19225116

Villegas, Raquel; Gao, Yu-Tang; Dai, Qi; Yang, Gong; Cai, Hui; Li, Honglan; Zheng, Wei; Shu, Xiao Ou

2009-01-01

26

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

SciTech Connect

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.

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

27

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

SciTech Connect

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.

Roomans, G.M.; Barnard, T.

1982-01-01

28

RIGOR MORTIS AND THE INFLUENCE OF CALCIUM AND MAGNESIUM SALTS UPON ITS DEVELOPMENT  

PubMed Central

Calcium salts hasten and magnesium salts retard the development of rigor mortis, that is, when these salts are administered subcutaneously or intravenously. When injected intra-arterially, concentrated solutions of both kinds of salts cause nearly an immediate onset of a strong stiffness of the muscles which is apparently a contraction, brought on by a stimulation caused by these salts and due to osmosis. This contraction, if strong, passes over without a relaxation into a real rigor. This form of rigor may be classed as work-rigor (Arbeitsstarre). In animals, at least in frogs, with intact cords, the early contraction and the following rigor are stronger than in animals with destroyed cord. If M/8 solutions—nearly equimolecular to "physiological" solutions of sodium chloride—are used, even when injected intra-arterially, calcium salts hasten and magnesium salts retard the onset of rigor. The hastening and retardation in this case as well as in the cases of subcutaneous and intravenous injections, are ion effects and essentially due to the cations, calcium and magnesium. In the rigor hastened by calcium the effects of the extensor muscles mostly prevail; in the rigor following magnesium injection, on the other hand, either the flexor muscles prevail or the muscles become stiff in the original position of the animal at death. There seems to be no difference in the degree of stiffness in the final rigor, only the onset and development of the rigor is hastened in the case of the one salt and retarded in the other. Calcium hastens also the development of heat rigor. No positive facts were obtained with regard to the effect of magnesium upon heat vigor. Calcium also hastens and magnesium retards the onset of rigor in the left ventricle of the heart. No definite data were gathered with regard to the effects of these salts upon the right ventricle. PMID:19867124

Meltzer, S. J.; Auer, John

1908-01-01

29

Continuous on-line feedback based flow titrations. Complexometric titrations of calcium and magnesium.  

PubMed

The methodology of continuous feedback-based flow titrations and the principle of compensating errors [Anal. Chem. 72 (2000) 4713; Anal. Chim. Acta 435 (2001) 289] were applied to the determination of calcium and magnesium ions with EDTA. The flow of the titrant, EDTA, varied linearly in response to a controller output voltage while the total flow (F(T), the sum of the metal ion sample flow and the titrant flow) was held constant. The sample was pre-doped with a metal ion indicator; the status of the indicator color in the mixed stream was monitored by an optical detector and was used for governing the controller output as well as for interpreting the results of the titrations. The titrant flow initially ramped upward linearly. As a change in the color corresponding to the equivalence point was sensed by the detector, the controller output (instantaneous value V(H)) reversed its ramp direction, thus decreasing the titrant flow linearly at the same ramp rate. When the predefined absorbance corresponding to the equivalence point was sensed again, the controller voltage (instantaneous value V(L)) was ramped in reverse once more, going upward. Because of the lag time between a change in the controller output and its effect being sensed by the detector, the controller voltage corresponding to the actual equivalence point was the average of V(H) and V(L). Continuous sensor-governed operation of the controller resulted in a triangular waveform. The mean of this waveform during any cycle gives the equivalence point controller voltage V(E). This principle allowed true titrations with good reproducibility (0.2-0.7% R.S.D.) and throughput (33-42 s per titration). PMID:18969033

Jo, Kyoo Dong; Dasgupta, Purnendu K

2003-05-28

30

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

PubMed

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

Hitchen, A; Zechanowitsch, G

1980-03-01

31

Effects of lanthanum on calcium and magnesium contents and cytoplasmic streaming of internodal cells of Chara corallina.  

PubMed

Biological and environmental effects of lanthanide series of elements have received much attention recently due to their wide applications. In this study, effects of La(3+) treatments on calcium and magnesium concentrations as well as cytoplasmic streaming of internodal cells of Chara corallina were investigated. At all treatment concentrations (10, 100, and 1,000 ?M), La(3+) significantly decreased calcium concentrations in the cell-wall fractions after 5-h treatments. Calcium concentrations in the cell contents and magnesium concentrations in the cell-wall fractions were reduced by 100 and 1,000 ?M La(3+) treatments. However, cytoplasmic streaming as an indicator of [Ca(2+)](cyt) was only inhibited at the highest La(3+) concentration (1,000 ?M). The results suggest that La(3+) may affect cellular calcium homeostasis by actions other than as a simple Ca(2+) antagonist. La(3+) could partially compensate for calcium deficiency at certain concentrations. PMID:20862562

Li, Zijie; Zhang, Zhiyong; Yu, Ming; Zhou, Yunlong; Zhao, Yuliang

2011-10-01

32

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

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

33

Thermodynamic Activities and Distributions of Calcium and Magnesium Between Silicon and CaO-MgO-SiO2 Slags at 1873 K (1600 °C)  

NASA Astrophysics Data System (ADS)

The distributions of calcium and magnesium between silicon and CaO-MgO-SiO2 slags have been determined in the present study at 1873 K (1600 °C). The distribution equilibria were used to estimate the activities of the slag components in the binary CaO-SiO2 and MgO-SiO2 systems. These activities were used to determine the Henrian activity coefficients of calcium and magnesium in liquid silicon at 1873 K (1600 °C). The distribution equilibria were also used to estimate the activity of SiO2 in the ternary CaO-MgO-SiO2 system. Finally, the activities of CaO and MgO were estimated in the ternary CaO-MgO-SiO2 system using the determined Henrian activity coefficients in liquid silicon together with the distribution equilibria and the estimated activities of SiO2.

Jakobsson, Lars Klemet; Tangstad, Merete

2015-01-01

34

Effects of calcium and magnesium ions on the toxicity of cadmium to the egg of the teleost, Oryzias latipes  

SciTech Connect

The effects of calcium and magnesium ions on the toxicity of cadmium to the eggs of the freshwater teleost, Oryzias latipes, were determined. Blastulae were immersed in free medium (Ca- and Mg-free), low-Ca medium (0.25 mM Ca), high-Ca medium (1.0 mM Ca), low-Mg medium (0.25 mM Mg), and high-Mg medium (1.0 mM Mg) with cadmium chloride at 10.0 mg/liter in each solution. Almost all eggs died within 24 hr in either free medium or low-Mg medium but high-Ca medium decreased mortality remarkably: 79.9% of the eggs survived. On the other hand, there was no statistically significant difference between the cadmium content of the eggs kept in Ca-containing media and those in Mg containing media at the corresponding molar concentrations. The present results revealed that of the two hardness constituents, calcium ions contributed to the suppression of the cadmium toxicity while magnesium ions did not.

Michibata, H.; Sahara, S.; Kojima, M.K.

1986-06-01

35

The Influence of Two Tree Species and the Synoptic Meteorological Setting on the Dry Deposition of Calcium and Magnesium to a Mixed Eastern Kansas Deciduous Canopy.  

NASA Astrophysics Data System (ADS)

The primary objective of this research was to investigate what factors influenced the dry deposition of calcium and magnesium to selected deciduous trees. As part of the overall research plan, data necessary to address (a) the depositional rate similarity between two tree species and (b) the influence of synoptic meteorology on the overall depositional process were collected and analyzed. This research represents the findings for data collected during the 1988 and 1989 growing seasons. Two tree species (red oak, Quercus rubra; shagbark hickory, Carya ovata) were selected for sampling during periods absent of precipitation. Leaves were collected from three individual canopies at similar geometric locations for each species at approximately three day intervals. Leaves were then washed using distilled, deionized water and the leaf areas were measured. Concentrations of calcium and magnesium were determined using atomic absorption; a mass per unit leaf area were subsequently calculated. The rate of dry deposition was calculated by dividing the mass per unit area difference between two sequential dry segment collections by the time difference. During all dry segments, the synoptic meteorological setting was determined. This was accomplished using on -site meteorological and upper air measurements. Each dry segment was subsequently analyzed using both numerical and subjective classification schemes. Rate data collected for the oak and hickory were compared and found to show significant differences in rate magnitude. The temporal and spatial trend of deposition was similar. Depositional rates were also compared with the synoptic meteorological setting using correlation matrices and multiple linear regression. Two synoptic variables, absolute humidity and relative humidity, typically showed the highest association with calcium and magnesium depositional rates. These variables in addition to other standard synoptic variables were used to generate a series of depositional models. In general these models predicted deposition in both trend and magnitude reasonably well.

Thomas, Mark James

1992-01-01

36

Calcium and magnesium disorders.  

PubMed

Hypocalcemia is a clinical disorder that can be life threatening to the cow (milk fever) and predisposes the animal to various other metabolic and infectious disorders. Calcium homeostasis is mediated primarily by parathyroid hormone, which stimulates bone calcium resorption and renal calcium reabsorption. Parathyroid hormone stimulates the production of 1,25-dihydroxyvitamin D to enhance diet calcium absorption. High dietary cation-anion difference interferes with tissue sensitivity to parathyroid hormone. Hypomagnesemia reduces tissue response to parathyroid hormone. PMID:24980727

Goff, Jesse P

2014-07-01

37

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)

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., Cerdŕ, 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

Pereira, Paulo; Martin, David

2014-05-01

38

The influence of calcium and magnesium in drinking water and diet on cardiovascular risk factors in individuals living in hard and soft water areas with differences in cardiovascular mortality  

Microsoft Academic Search

BACKGROUND: The role of water hardness as a risk factor for cardiovascular disease has been widely investigated and evaluated as regards regional differences in cardiovascular disease. This study was performed to evaluate the relation between calcium and magnesium in drinking water and diet and risk factors for cardiovascular disease in individuals living in hard and soft water areas with considerable

Christina Nerbrand; Lars Agréus; Ragnhild Arvidsson Lenner; Per Nyberg; Kurt Svärdsudd

2003-01-01

39

Phase III Randomized, Placebo-Controlled, Double-Blind Study of Intravenous Calcium and Magnesium to Prevent Oxaliplatin-Induced Sensory Neurotoxicity (N08CB/Alliance)  

PubMed Central

Purpose Cumulative neurotoxicity is a prominent toxicity of oxaliplatin-based therapy. Intravenous calcium and magnesium have been extensively used to reduce oxaliplatin-induced neurotoxicity. This trial was designed to definitively test whether calcium/magnesium decreases oxaliplatin-related neurotoxicity. Patients and Methods In all, 353 patients with colon cancer undergoing adjuvant therapy with FOLFOX (fluorouracil, leucovorin, and oxaliplatin) were randomly assigned to intravenous calcium/magnesium before and after oxaliplatin, a placebo before and after, or calcium/magnesium before and placebo after. The primary end point was cumulative neurotoxicity measured by the sensory scale of the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Chemotherapy-Induced Peripheral Neuropathy 20 tool. Results There were no statistically significant neuropathy differences among the study arms as measured by the primary end point or additional measures of neuropathy, including clinician-determined measurement of the time to grade 2 neuropathy by using the National Cancer Institute Common Terminology Criteria for Adverse Events scale or an oxaliplatin-specific neuropathy scale. In addition, calcium/magnesium did not substantially decrease oxaliplatin-induced acute neuropathy. Conclusion This study does not support using calcium/magnesium to protect against oxaliplatin-induced neurotoxicity. PMID:24297951

Loprinzi, Charles L.; Qin, Rui; Dakhil, Shaker R.; Fehrenbacher, Louis; Flynn, Kathleen A.; Atherton, Pamela; Seisler, Drew; Qamar, Rubina; Lewis, Grant C.; Grothey, Axel

2014-01-01

40

Abnormalities of serum calcium and magnesium  

Technology Transfer Automated Retrieval System (TEKTRAN)

Neonatal hypocalcemia is defined as a total serum calcium concentration of <7 mg/dL or an ionized calcium concentration of <4 mg/dL (1mmol/L). In very low birth weight (VLBW) infants, ionized calcium values of 0.8 to 1 mmol/L are common and not usually associated with clinical symptoms. In larger in...

41

Adenosine dysfunction in epilepsy.  

PubMed

Extracellular levels of the brain's endogenous anticonvulsant and neuroprotectant adenosine largely depend on an astrocyte-based adenosine cycle, comprised of ATP release, rapid degradation of ATP into adenosine, and metabolic reuptake of adenosine through equilibrative nucleoside transporters and phosphorylation by adenosine kinase (ADK). Changes in ADK expression and activity therefore rapidly translate into changes of extracellular adenosine, which exerts its potent anticonvulsive and neuroprotective effects by activation of pre- and postsynaptic adenosine A(1) receptors. Increases in ADK increase neuronal excitability, whereas decreases in ADK render the brain resistant to seizures and injury. Importantly, ADK was found to be overexpressed and associated with astrogliosis and spontaneous seizures in rodent models of epilepsy, as well as in human specimen resected from patients with hippocampal sclerosis and temporal lobe epilepsy. Several lines of evidence indicate that overexpression of astroglial ADK and adenosine deficiency are pathological hallmarks of the epileptic brain. Consequently, adenosine augmentation therapies constitute a powerful approach for seizure prevention, which is effective in models of epilepsy that are resistant to conventional antiepileptic drugs. The adenosine kinase hypothesis of epileptogenesis suggests that adenosine dysfunction in epilepsy undergoes a biphasic response: an acute surge of adenosine that can be triggered by any type of injury might contribute to the development of astrogliosis via adenosine receptor-dependent and -independent mechanisms. Astrogliosis in turn is associated with overexpression of ADK, which was shown to be sufficient to trigger spontaneous recurrent electrographic seizures. Thus, ADK emerges as a promising target for the prediction and prevention of epilepsy. PMID:22700220

Boison, Detlev

2012-08-01

42

Adenosine and adenosine receptors: Newer therapeutic perspective  

PubMed Central

Adenosine, a purine nucleoside has been described as a ‘retaliatory metabolite’ by virtue of its ability to function in an autocrine manner and to modify the activity of a range of cell types, following its extracellular accumulation during cell stress or injury. These effects are largely protective and are triggered by binding of adenosine to any of the four adenosine receptor subtypes namely A1, A2a, A2b, A3, which have been cloned in humans, and are expressed in most of the organs. Each is encoded by a separate gene and has different functions, although overlapping. For instance, both A1 and A2a receptors play a role in regulating myocardial oxygen consumption and coronary blood flow. It is a proven fact that adenosine plays pivotal role in different physiological functions, such as induction of sleep, neuroprotection and protection against oxidative stress. Until now adenosine was used for certain conditions like paroxysmal supraventricular tachycardia (PSVT) and Wolff Parkinson White (WPW) syndrome. Now there is a growing evidence that adenosine receptors could be promising therapeutic targets in a wide range of conditions including cardiac, pulmonary, immunological and inflammatory disorders. After more than three decades of research in medicinal chemistry, a number of selective agonists and antagonists of adenosine receptors have been discovered and some have been clinically evaluated, although none has yet received regulatory approval. So this review focuses mainly on the newer potential role of adenosine and its receptors in different clinical conditions. PMID:20442815

Manjunath, S.; Sakhare, Pranavkumar M.

2009-01-01

43

Adenosine dysfunction and adenosine kinase in epileptogenesis.  

PubMed

Traditionally, epilepsy has been considered to be a disorder of neuronal dysfunction. Based on this dogma, drug development efforts have largely focused on neurocentric model systems to screen for compounds that affect the function of neurons. Unfortunately, about 30% of all patients with epilepsy - or more than 20 million worldwide - are refractory to classical neurocentric pharmacotherapy. The failure of neurocentric pharmacotherapy in epilepsy requires radical rethinking and the search for novel therapeutic targets. Research from recent years suggests that epilepsy is a disorder of astrocyte dysfunction. Astrocytes are key regulators of the brain's own anticonvulsant adenosine. Thus, any dysfunction in astrocyte metabolism will drastically affect the brain's ability to control excitability via adenosinergic neuromodulation. This review will focus on the astrocyte-based enzyme adenosine kinase (ADK) as the key regulator of synaptic adenosine. Astrogliosis - a pathological hallmark of the epileptic brain - leads to overexpression of the adenosine-removing enzyme ADK and therefore to adenosine deficiency. Evidence from transgenic animals demonstrates that overexpression of ADK per se is sufficient to trigger seizures. Consequently, pharmacological inhibition of ADK is very effective in suppressing seizures that are refractory to classical antiepileptic drugs. The recent definition of ADK as rational target to predict and to prevent seizures in epilepsy has prompted the development of focal adenosine augmentation therapies (AATs) that have been designed to selectively reconstitute adenosinergic signalling within an area of astrogliosis-based adenosine-dysfunction. This therapeutic challenge has experimentally been met with polymeric or stem cell based brain implants to afford the focal delivery of adenosine. PMID:20730044

Boison, Detlev

2010-01-01

44

Modulation of adenosine release from rat spinal cord by adenosine deaminase and adenosine kinase inhibitors  

Microsoft Academic Search

Adenosine, a modulator of pain processing in the spinal cord, is metabolized by adenosine kinase and adenosine deaminase. In this study we determined which of these mechanisms is more important for the regulation of endogenous adenosine levels in the rat spinal cord. The effects of the adenosine kinase inhibitors, 5?-deoxyadenosine (NH2dAD) and iodotubercidin (IOT), and the adenosine deaminase inhibitor, 2?-deoxycoformycin

Krystyna Golembiowska; Thomas D. White; Jana Sawynok

1995-01-01

45

Adenosine kinase inhibitors attenuate opiate withdrawal via adenosine receptor activation  

Microsoft Academic Search

Previous studies have demonstrated a role for adenosine in mediating opiate effects. This study examines the effects of indirect activation of adenosine receptors, via treatment with adenosine kinase inhibitors, on the expression of opiate withdrawal in mice. Mice receive chronic morphine treatment via implantation of subcutaneous morphine pellets (75 mg) for 72 h. Mice then receive parenteral treatment with adenosine

Gary B. Kaplan; Tara Sharon Coyle

1998-01-01

46

Molecular Structure of Adenosine  

NSDL National Science Digital Library

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.

2002-08-19

47

Increases in interstitial adenosine and cerebral blood flow with inhibition of adenosine kinase and adenosine deaminase.  

PubMed

The purpose of this study was to determine the changes in interstitial fluid (ISF) adenosine and cerebral blood flow (CBF) during inhibition of adenosine kinase or adenosine deaminase. Brain microdialysis was used to (a) measure CBF (H2 clearance), (b) sample cerebral ISF, and (c) deliver drugs locally to the brain. Microdialysis probes were implanted bilaterally in the caudate nucleus of halothane-anesthetized rats (n = 11). One probe was perfused with artificial cerebrospinal fluid (CSF) containing iodotubercidin (IODO), an adenosine kinase inhibitor, while the other probe was perfused with erythro-2-(2-hydroxy-3-nonyl)adenine (EHNA), an adenosine deaminase inhibitor. Both probes were subsequently perfused with EHNA+IODO. Finally, 8-(p-sulfophenyl)theophylline (SPT), an adenosine receptor antagonist, was added to EHNA + IODO in one probe, while the other probe continued to receive only EHNA + IODO. CBF and dialysate adenosine levels increased with either EHNA or IODO; however, the increases were greater with IODO. EHNA + IODO further increased CBF and dialysate adenosine. The hyperemia observed with EHNA + IODO was abolished by adenosine receptor blockade. These data suggest that basal adenosine levels are influenced to a greater extent by adenosine kinase than by adenosine deaminase. In addition, the increased CBF observed with inhibition of adenosine metabolism and the attenuation of this vasodilatory response with adenosine receptor blockade support a role for adenosine in CBF regulation. PMID:8436611

Sciotti, V M; Van Wylen, D G

1993-03-01

48

Involvement of adenosine deaminase and adenosine kinase in regulating extracellular adenosine concentration in rat hippocampal slices  

Microsoft Academic Search

In this study the relative importance of adenosine deaminase and adenosine kinase in regulating extracellular adenosine concentration was investigated in rat hippocampal slices labelled with [3H]-adenine. The release of [3H]-purines evoked by electrical stimulation or energy depletion (oxygen and glucose deprivation) was measured and, using high-performance liquid chromatography (HPLC), the proportion of [3H]-label in the form of [3H]-adenosine, [3H]-inosine and

H. G. E. Lloyd; B. B. Fredholm

1995-01-01

49

Increases in Interstitial Adenosine and Cerebral Blood Flow with Inhibition of Adenosine Kinase and Adenosine Deaminase  

Microsoft Academic Search

Summary: The purpose of this study was to determine the changes in interstitial fluid (ISF) adenosine and cerebral blood flow (CBF) during inhibition of adenosine kinase or adenosine deaminase. Brain microdialysis was used to (a) measure CBF (H2 clearance), (b) sample cerebral ISF, and (c) deliver drugs locally to the brain. Microdialysis probes were implanted bilaterally in the caudate nucleus

Veronica M. Sciotti; David G. L. Van Wylen

1993-01-01

50

Adenosine and sleep  

SciTech Connect

Behavioral and biochemical approaches have been used to determine the relative contribution of endogenous adenosine and adenosine receptors to the sleep-wake cycle in the rat. Adenosine concentrations in specific areas of the rat brain were not affected by 24 hours of total sleep deprivation, or by 24 or 48 hours of REM sleep deprivation. In order to assess the effect of REM sleep deprivation on adenosine A/sub 1/ receptors, /sup 3/H-L-PIA binding was measured. The Bmax values for /sup 3/H-L-PIA binding to membrane preparations of the cortices and corpus striata from 48 hour REM sleep-deprived animals were increased 14.8% and 23%, respectively. These increases were not maintained following the cessation of sleep deprivation and recovered within 2 hours. The results of a 96 hour REM deprivation experiment were similar to those of the 48 hour REM sleep deprivation experiment. However, these increases were not evident in similar structures taken from stress control animals, and conclusively demonstrated that the changes in /sup 3/H-L-PIA binding resulted from REM sleep deprivation and not from stress.

Yanik, G.M. Jr.

1987-01-01

51

Adenosine and the Auditory System  

PubMed Central

Adenosine is a signalling molecule that modulates cellular activity in the central nervous system and peripheral organs via four G protein-coupled receptors designated A1, A2A, A2B, and A3. This review surveys the literature on the role of adenosine in auditory function, particularly cochlear function and its protection from oxidative stress. The specific tissue distribution of adenosine receptors in the mammalian cochlea implicates adenosine signalling in sensory transduction and auditory neurotransmission although functional studies have demonstrated that adenosine stimulates cochlear blood flow, but does not alter the resting and sound-evoked auditory potentials. An interest in a potential otoprotective role for adenosine has recently evolved, fuelled by the capacity of A1 adenosine receptors to prevent cochlear injury caused by acoustic trauma and ototoxic drugs. The balance between A1 and A2A receptors is conceived as critical for cochlear response to oxidative stress, which is an underlying mechanism of the most common inner ear pathologies (e.g. noise-induced and age-related hearing loss, drug ototoxicity). Enzymes involved in adenosine metabolism, adenosine kinase and adenosine deaminase, are also emerging as attractive targets for controlling oxidative stress in the cochlea. Other possible targets include ectonucleotidases that generate adenosine from extracellular ATP, and nucleoside transporters, which regulate adenosine concentrations on both sides of the plasma membrane. Developments of selective adenosine receptor agonists and antagonists that can cross the blood-cochlea barrier are bolstering efforts to develop therapeutic interventions aimed at ameliorating cochlear injury. Manipulations of the adenosine signalling system thus hold significant promise in the therapeutic management of oxidative stress in the cochlea. PMID:20190966

Vlajkovic, Srdjan M; Housley, Gary D; Thorne, Peter R

2009-01-01

52

Rat cardiac myocyte adenosine transport and metabolism  

SciTech Connect

Based on the importance of myocardial adenosine and adenine nucleotide metabolism, the adenosine salvage pathway in ventricular myocytes was studied. Accurate estimates of transport rates, separate from metabolic fllux, were determined. Adenosine influx was constant between 3 and 60 s. Adenosine metabolism maintained intracellular adenosine concentrations < 10% of the extracellular adenosine concentrations and thus unidirectional influx could be measured. Myocytes transported adenosine via saturable and nonsaturable processes. A minimum estimate of the V/sub max/ of myocytic adenosine kinase indicated the saturable component of adenosine influx was independent of adenosine kinase activity. Saturable transport was inhibited by nitrobenzylthioinosine and verapamil. Extracellular adenosine taken up myocytes was rapidly phosphorylated to adenine taken up by myocytes was rapidly phosphorylated to adenine nucleotides. Not all extracellular adenosine, though, was phosphorylated on entering myocytes, since free, as opposed to protein-bound, intracellular adenosine was detected after digitonin extraction of cells in the presence of 1 mM ethylene-diaminetetraacetic acid.

Ford, D.A.; Rovetto, M.J.

1987-01-01

53

Microdetermination of calcium and magnesium in biological materials  

PubMed Central

The use of the dye calcon (1-(2 hydroxy-1-naphthylazo)-2-naphthol-4 sulphonic acid) for the estimation of calcium using E.D.T.A. and a commercial photoelectric titrimeter is described. The interfering effects of magnesium and phosphate have been overcome. The method has been extended to estimations on biological materials. Results on 55 sera show that the E.D.T.A./calcon method gave slightly lower results (—0ˇ15 mg./100 ml. ą 0ˇ029) than the oxalate precipitation method. Magnesium may also be estimated by incorporating the use of Eriochrome black T. PMID:14014590

Bowden, C. H.; Patston, Valerie J.

1963-01-01

54

Spectrophotometric Titration of a Mixture of Calcium and Magnesium.  

ERIC Educational Resources Information Center

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…

Fulton, Robert; And Others

1986-01-01

55

Shear Strength and Consolidation Characteristics of Calcium and Magnesium Illite  

Microsoft Academic Search

In recent soil mechanics litcrature attempts have been made to explain the engineering properties of clays in terms of surface chemical theories, particularly the Gouy-Chapman theory. Experimental confirmation of these theoretical predictions have been restricted almost exclusively to studies performed on fine grain size fractions of montmorillonitc. it seemed d~sirable to determine experimentally the effect of physico-chemieal variables on the

Roy E. Olson; FREDERICK MITRONOVAS

1960-01-01

56

Urinary excretion of calcium and magnesium in children  

Microsoft Academic Search

Urine calcium excretion in healthy children was 2ˇ38ą0ˇ66 (SD; no. = 52) mg\\/kg per 24 hr and urinary magnesium excretion was 2ˇ82ą0ˇ79 (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

S. Ghazali; T. M. Barratt

1974-01-01

57

FK506 promotes adenosine release from endothelial cells via inhibition of adenosine kinase  

Microsoft Academic Search

The immunosuppressants, cyclosporin A and tacrolimus (FK506) induce an increase in plasma levels of adenosine and mimic ischemic preconditioning. However, the mechanism of action of the two drugs on adenosine metabolism is not clear. Since inhibition of adenosine kinase promotes an increase in endogenous adenosine release, we tested a hypothesis that FK506 induces adenosine release via inhibition of adenosine kinase

Kwan-Ki Hwang; Carolyn S Hall; William S Spielman; Harvey V Sparks

2001-01-01

58

Viral adenosine triphosphatase.  

PubMed

The catalytic and immunological properties of an adenosine triphosphatase from different types of virus have been studied. The avian myeloblastosis virus has been found to be specialized in holding this enzyme in a highly active state as compared to other virus with respect to their host cell enzyme. Catalytically myeloblastosis virus and Rous virus ATPase behave alike, while that of the Reo virus is significantly different. PMID:214324

Banerjee, R K

1978-11-15

59

Subclasses of external adenosine receptors.  

PubMed Central

Cell surface adenosine receptors mediate either stimulation or inhibition of adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1], and the receptors that mediate these different responses can be discriminated with selected adenosine analogs. 5'-N-Ethylcarboxamide-adenosine is a more potent agonist at stimulatory receptors (Ra) than is N6-phenylisopropyladenosine, whereas the reverse potency order is seen with inhibitory receptors (Ri). The potency of adenosine is intermediate between the potencies of these two analogs. The relative potencies of adenosine receptor agonists are maintained in physiological responses in intact cells, such as steroidogenesis and inhibition of lipolysis. As with adrenergic receptors, subclasses of adenosine receptors differ functionally and pharmacologically. PMID:6248853

Londos, C; Cooper, D M; Wolff, J

1980-01-01

60

Adenosine kinase inhibitors augment release of adenosine from spinal cord slices  

Microsoft Academic Search

Inhibitors of adenosine kinase, but not adenosine deaminase, produce antinociception when administered spinally. In this study, we evaluated the relative contribution of adenosine kinase and adenosine deaminase to the regulation of adenosine release into the extracellular space within the spinal cord by determining the effects of the adenosine kinase inhibitors 5?amino-5?deoxyadenosine and 5-iodotubercidin, and the adenosine deaminase inhibitor 2?deoxycoformycin on

Krystyna Golembiowska; Thomas D. White; Jana Sawynok

1996-01-01

61

Effects of Adenosine on Lymphangiogenesis  

PubMed Central

Background The lymphatic system controls tissue homeostasis by draining protein-rich lymph to the vascular system. Lymphangiogenesis, the formation of lymphatic vessels, is a normal event in childhood but promotes tumor spread and metastasis during adulthood. Blocking lymphangiogenesis may therefore be of therapeutic interest. Production of adenosine is enhanced in the tumor environment and contributes to tumor progression through stimulation of angiogenesis. In this study, we determined whether adenosine affects lymphangiogenesis. Methods Lymphatic endothelial cells (HMVEC-dLy) were cultured in presence of adenosine and their proliferation, migration and tube formation was assessed. Gelatin sponges embedded with the stable analogue of adenosine 2-chloro adenosine were implanted in mice ear and lymphangiogenesis was quantified. Mice were intravenously injected with adenoviruses containing expression vector for 5?-endonucleotidase, which plays a major role in the formation of adenosine. Results In vitro, we observed that adenosine decreased the proliferation of lymphatic endothelial cells, their migration and tube formation. However, in vivo, gelatin sponges containing 2-chloro adenosine and implanted in mice ear displayed an elevated level of lymphangiogenesis (2.5-fold, p<0.001). Adenovirus-mediated over-expression of cytosolic 5?-nucleotidase IA stimulated lymphangiogenesis and the recruitment of macrophages in mouse liver. Proliferation of lymphatic endothelial cells was enhanced (2-fold, p<0.001) when incubated in the presence of conditioned medium from murine macrophages. Conclusion We have shown that adenosine stimulates lymphangiogenesis in vivo, presumably through a macrophage-mediated mechanism. This observation suggests that blockade of adenosine receptors may help in anti-cancer therapies. PMID:24651845

Lenoir, Bénédicte; Wagner, Daniel R.; Blacher, Silvia; Sala-Newby, Graciela B.; Newby, Andrew C.; Noel, Agnčs; Devaux, Yvan

2014-01-01

62

Purine Metabolism in Adenosine Deaminase Deficiency  

Microsoft Academic Search

Purine and pyrimidine metabolites were measured in erythrocytes, plasma, and urine of a 5-month-old infant with adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) deficiency. Adenosine and adenine were measured using newly devised ion exchange separation techniques and a sensitive fluorescence assay. Plasma adenosine levels were increased, whereas adenosine was normal in erythrocytes and not detectable in urine. Increased amounts of adenine

Gordon C. Mills; Frank C. Schmalstieg; K. Bryan Trimmer; Armond S. Goldman; Randall M. Goldblum

1976-01-01

63

Subclasses of External Adenosine Receptors  

Microsoft Academic Search

Cell surface adenosine receptors mediate either stimulation or inhibition of adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1], and the receptors that mediate these different responses can be discriminated with selected adenosine analogs. 5'-N-Ethylcarboxamideadenosine is a more potent agonist at stimulatory receptors (Ra) than is N6-phenylisopropyladenosine, whereas the reverse potency order is seen with inhibitory receptors (Ri). The potency of

Constantine Londos; Dermot M. F. Cooper; J. Wolff

1980-01-01

64

Genetics Home Reference: Adenosine deaminase deficiency  

MedlinePLUS

... PubMed Recent literature OMIM Genetic disorder catalog Conditions > Adenosine deaminase deficiency (often shortened to ADA deficiency ) On this page: ... other health problems. How common is ADA deficiency? Adenosine deaminase deficiency is very rare and is estimated to occur ...

65

Xanthines as Adenosine Receptor Antagonists  

PubMed Central

The natural plant alkaloids caffeine and theophylline were the first adenosine receptor (AR) antagonists described in the literature. They exhibit micromolar affinities and are non-selective. A large number of derivatives and analogs have subsequently been synthesized and evaluated as AR antagonists. Very potent antagonists have thus been developed with selectivity for each of the four AR subtypes. PMID:20859796

Jacobson, Kenneth A.

2013-01-01

66

Overexpression of Adenosine Kinase in Epileptic Hippocampus Contributes to Epileptogenesis  

Microsoft Academic Search

Endogenous adenosine in the brain is thought to prevent the development and spread of seizures via a tonic anticonvulsant effect. Brain levels of adenosine are primarily regulated by the activity of adenosine kinase. To establish a link between adenosine kinase expression and seizure activity, we analyzed the expression of adenosine kinase in the brain of control mice and in a

Nicolette Gouder; Louis Scheurer; Jean-Marc Fritschy; Detlev Boison

2004-01-01

67

Fluorescent Ligands for Adenosine Receptors  

PubMed Central

Interest is increasing in developing fluorescent ligands for characterization of adenosine receptors (ARs), which hold a promise of usefulness in the drug discovery process. The size of a strategically labeled AR ligand can be greatly increased after the attachment of a fluorophore. The choice of dye moiety (e.g. Alexa Fluor 488), attachment point and linker length can alter the selectivity and potency of the parent molecule. Fluorescent derivatives of adenosine agonists and antagonists (e.g. XAC and other heterocyclic antagonist scaffolds) have been synthesized and characterized pharmacologically. Some are useful AR probes for flow cytometry, fluorescence correlation spectroscopy, fluorescence microscopy, fluorescence polarization, fluorescence resonance energy transfer, and scanning confocal microscopy. Thus, the approach of fluorescent labeled GPCR ligands, including those for ARs, is a growing dynamic research field. PMID:23200243

Kozma, Eszter; Jayasekara, P Suresh; Squarcialupi, Lucia; Paoletta, Silvia; Moro, Stefano; Federico, Stephanie; Spalluto, Giampiero; Jacobson, Kenneth A.

2012-01-01

68

Antinociception by adenosine analogs and inhibitors of adenosine metabolism in an inflammatory thermal hyperalgesia model in the rat  

Microsoft Academic Search

The present study examined the spinal antinociceptive effects of adenosine analogs and inhibitors of adenosine kinase and adenosine deaminase in the carrageenan-induced thermal hyperalgesia model in the rat. The possible enhancement of the antinociceptive effects of adenosine kinase inhibitors by an adenosine deaminase inhibitor also was investigated. Unilateral hindpaw inflammation was induced by an intraplantar injection of lambda carrageenan (2

Anthony Poon; Jana Sawynok

1998-01-01

69

Regulation of Macrophage Function by Adenosine  

PubMed Central

Following its release into the extracellular space in response to metabolic disturbances, the endogenous nucleoside adenosine exerts a range of immunomodulatory effects and cells of the mononuclear phagocyte system are among its major targets. Adenosine governs mononuclear phagocyte functions via 4 G-protein–coupled cell membrane receptors, which are denoted A1, A2A, A2B, and A3 receptors. Adenosine promotes osteoclast differentiation via A1 receptors and alters monocyte to dendritic cell differentiation through A2B receptors. Adenosine downregulates classical macrophage activation mainly through A2A receptors. In contrast A2B receptor activation upregulates alternative macrophage activation. Adenosine promotes angiogenesis, which is mediated by inducing the production of vascular endothelial growth factor by mononuclear phagocytes through A2A, A2B, and A3 receptors. By regulating mononuclear phagocyte function adenosine dictates the course of inflammatory and vascular diseases and cancer. PMID:22423038

Haskó, György; Pacher, Pál

2012-01-01

70

Ion-Dependent Dynamics of DNA Ejections for Bacteriophage l David Van Valen,6  

E-print Network

Ion-Dependent Dynamics of DNA Ejections for Bacteriophage l David Wu,6 David Van Valen,6 Qicong Hu studied the control parameters that govern the dynamics of in vitro DNA ejection in bacteriophage l. Previous work demonstrated that bacteriophage DNA is highly pressurized, and this pressure has been

Phillips, Rob

71

Magnesium Ion-dependent Activation of the RecA Protein Involves the C Terminus*  

E-print Network

Magnesium Ion-dependent Activation of the RecA Protein Involves the C Terminus* Received with ATP. We provide evi- dence that the free magnesium ion is required to medi- ate a conformational at low magnesium ion concentrations. The RecA protein of Escherichia coli plays a central role

Cox, Michael M.

72

Antinociceptive and anti-inflammatory properties of an adenosine kinase inhibitor and an adenosine deaminase inhibitor  

Microsoft Academic Search

Spinal administration of an adenosine kinase inhibitor, alone or in combination with an adenosine deaminase inhibitor, produces antinociception in inflammatory pain tests. In the present study, we examined the antinociceptive and anti-inflammatory effects produced by the peripheral (intraplantar) administration of 5?-amino-5?-deoxyadenosine (an adenosine kinase inhibitor), 2?-deoxycoformycin (an adenosine deaminase inhibitor), and combinations of both agents in the carrageenan-induced thermal hyperalgesia

Anthony Poon; Jana Sawynok

1999-01-01

73

Stimulation of nucleoside efflux and inhibition of adenosine kinase by A 1 adenosine receptor activation  

Microsoft Academic Search

Adenosine is produced intracellularly during conditions of metabolic stress and is an endogenous agonist for four subtypes of G-protein linked receptors. Nucleoside transporters are membrane-bound carrier proteins that transfer adenosine, and other nucleosides, across biological membranes. We investigated whether adenosine receptor activation could modulate transporter-mediated adenosine efflux from metabolically stressed cells. DDT1 MF-2 smooth muscle cells were incubated with 10

Christopher J. D Sinclair; P. Nicholas Shepel; Jonathan D Geiger; Fiona E Parkinson

2000-01-01

74

Regulation of neutrophil function by adenosine  

PubMed Central

Adenosine is an endogenously released purine nucleoside that signals via four widely expressed G-protein coupled receptors: A1, A2A, A2B, and A3. In the setting of inflammation, the generation and release of adenosine is greatly enhanced. Neutrophils play an important role in host defense against invading pathogens and are the cellular hallmark of acute inflammation. Neutrophils both release adenosine and can respond to it via expression of all four adenosine receptor subtypes. At low concentrations, adenosine can act via the A1 and A3 adenosine receptor subtypes to promote neutrophil chemotaxis and phagocytosis. At higher concentrations, adenosine acts at the lower-affinity A2A and A2B receptors to inhibit neutrophil trafficking and effector functions such as oxidative burst, inflammatory mediator production, and granule release. Modulation of neutrophil function by adenosine is relevant in a broad array of disease models, including ischemia reperfusion injury, sepsis, and non-infectious acute lung injury. This review will summarize relevant research in order to provide a framework for understanding how adenosine directly regulates various elements of neutrophil function. PMID:22423037

Barletta, Kathryn E.; Ley, Klaus; Mehrad, Borna

2012-01-01

75

Regulation of neutrophil function by adenosine.  

PubMed

Adenosine is an endogenously released purine nucleoside that signals via 4 widely expressed G protein-coupled receptors: A(1), A(2A), A(2B), and A(3). In the setting of inflammation, the generation and release of adenosine is greatly enhanced. Neutrophils play an important role in host defense against invading pathogens and are the cellular hallmark of acute inflammation. Neutrophils both release adenosine and can respond to it via expression of all 4 adenosine receptor subtypes. At low concentrations, adenosine can act via the A(1) and A(3) adenosine receptor subtypes to promote neutrophil chemotaxis and phagocytosis. At higher concentrations, adenosine acts at the lower-affinity A(2A) and A(2B) receptors to inhibit neutrophil trafficking and effector functions such as oxidative burst, inflammatory mediator production, and granule release. Modulation of neutrophil function by adenosine is relevant in a broad array of disease models, including ischemia reperfusion injury, sepsis, and noninfectious acute lung injury. This review will summarize relevant research in order to provide a framework for understanding how adenosine directly regulates various elements of neutrophil function. PMID:22423037

Barletta, Kathryn E; Ley, Klaus; Mehrad, Borna

2012-04-01

76

Clinical application of adenosine and ATP for pain control  

Microsoft Academic Search

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

Masakazu Hayashida; Ken-ichi Fukuda; Atsuo Fukunaga

2005-01-01

77

Substrate inhibition of adenosine phosphorylation in adenosine deaminase deficiency and adenosine-mediated inhibition of PP-ribose-P dependent nucleotide synthesis in hypoxanthine phosphoribosyltransferase deficient erythrocytes  

Microsoft Academic Search

Summary The metabolism of adenosine and its effects on phosphoribosylpyrophosphate, PP-ribose-P, dependent nucleotide synthesis were studied using erythrocytes from patients with adenosine deaminase and hypoxanthine phosphoribosyltransferase deficiency as models. The phosphorylation of adenosine was progressively inhibited by concentrations of adenosine greater than 1 ľmol L-1 for control and ADA deficient erythrocytes. There was essentially no initial rate of phosphorylation at

F. F. Snyder; C. Dyer; J. E. Seegmiller; R. M. Goldblum; G. C. Mills; F. C. Schmalstieg

1988-01-01

78

Potentiation of excitatory amino acid-evoked adenosine release from rat cortex by inhibitors of adenosine kinase and adenosine deaminase and by acadesine  

Microsoft Academic Search

Endogenous extracellular adenosine provides some protection against excitotoxicity in the central nervous system, but it appears to be incomplete. Potentiating the formation of extracellular adenosine that occurs when excitatory amino acid receptors are activated might provide additional protection. We studied the effects of AICAR (AICA riboside, acadesine) and of inhibitors of adenosine metabolism on the release of adenosine from rat

Thomas D. White

1996-01-01

79

Astrocytic adenosine kinase regulates basal synaptic adenosine levels and seizure activity but not activity-dependent adenosine release in the hippocampus  

Microsoft Academic Search

Adenosine is an endogenous inhibitor of excitatory synaptic transmission with potent anticonvulsant properties in the mammalian brain. Given adenosine's important role in modulating synaptic transmission, several mechanisms exist to regulate its extracellular availability. One of these is the intracellular enzyme adenosine kinase (ADK), which phosphorylates adenosine to AMP. We have investigated the role that ADK plays in regulating the presence

Lori-An V. Etherington; Graham E. Patterson; Louise Meechan; Detlev Boison; Andrew J. Irving; Nicholas Dale; Bruno G. Frenguelli

2009-01-01

80

Adenosine postsynaptically modulates supraoptic neuronal excitability.  

PubMed

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

Ponzio, Todd A; Hatton, Glenn I

2005-01-01

81

Resveratrol inhibits metal ion-dependent and independent peroxidation of porcine low-density lipoproteins  

Microsoft Academic Search

Resveratrol, a phytoalexin (3, 4?, 5, trihydroxystilbene) present in some red wines, has been reported to inhibit copper-mediated low-density lipoprotein (LDL) oxidation. In this study, we examined the efficiency of this compound in inhibiting metal ion-dependent and independent peroxidation of porcine LDL. At 0.5, 1, or 1.5 ?M, transresveratrol prolonged the lag time preceding the onset of conjugated diene formation

Leila Belguendouz; Lucie Fremont; Alain Linard

1997-01-01

82

Homeostatic control of synaptic activity by endogenous adenosine is mediated by adenosine kinase.  

PubMed

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

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

2014-01-01

83

A Role for Adenosine Deaminase in Drosophila Larval Development  

E-print Network

A Role for Adenosine Deaminase in Drosophila Larval Development Tomas Dolezal1 , Eva Dolezelova2 Budejovice, Czech Republic Adenosine deaminase (ADA) is an enzyme present in all organisms that catalyzes the effects of altered adenosine levels in vivo by genetic elimination of adenosine deaminase-related growth

Gibson, Matt

84

Adenosine receptors and behavioral actions of methylxanthines.  

PubMed Central

Central stimulant actions of 10 methylxanthines in mice correlate with affinities for adenosine receptors labeled with N6-[3H]cyclohexyladenosine. Affinities of methylxanthines for adenosine receptors are consonant with central levels attained at behaviorally effective doses. The much higher concentrations of methylxanthines required to influence benzodiazepine receptor binding do not correlate with behavioral potency. N6-(L-Phenylisopropyl)adenosine (L-PIA), a metabolically stable analog of adenosine with high affinity for adenosine receptors, is an extremely potent behavioral depressant, reducing locomotor activity of mice at doses as little as 0.05 mumol/kg. The D isomer, which has much less affinity for adenosine receptors, is much less active as a central depressant. Theophylline stimulates locomotor activity and reverses depressant effects of L-PIA. Caffeine or 1,7-dimethylxanthine, when administered alone, elicits biphasic effects, with locomotor depression at lower doses and stimulation at higher doses. When administered with L-PIA, even low doses of caffeine produce marked stimulation. 3-Isobutyl-1-methylxanthine given alone elicits only behavioral depression. However, like theophylline and caffeine, isobutylmethylxanthine reverses the L-PIA-evoked depression, converting it into pronounced locomotor stimulation. The data strongly suggest that the behavioral stimulant effects of methylxanthines involve a blockade of central adenosine receptors. PMID:6265942

Snyder, S H; Katims, J J; Annau, Z; Bruns, R F; Daly, J W

1981-01-01

85

Adenosine kinase: exploitation for therapeutic gain.  

PubMed

Adenosine kinase (ADK; EC 2.7.1.20) is an evolutionarily conserved phosphotransferase that converts the purine ribonucleoside adenosine into 5'-adenosine-monophosphate. This enzymatic reaction plays a fundamental role in determining the tone of adenosine, which fulfills essential functions as a homeostatic and metabolic regulator in all living systems. Adenosine not only activates specific signaling pathways by activation of four types of adenosine receptors but it is also a primordial metabolite and regulator of biochemical enzyme reactions that couple to bioenergetic and epigenetic functions. By regulating adenosine, ADK can thus be identified as an upstream regulator of complex homeostatic and metabolic networks. Not surprisingly, ADK dysfunction is involved in several pathologies, including diabetes, epilepsy, and cancer. Consequently, ADK emerges as a rational therapeutic target, and adenosine-regulating drugs have been tested extensively. In recent attempts to improve specificity of treatment, localized therapies have been developed to augment adenosine signaling at sites of injury or pathology; those approaches include transplantation of stem cells with deletions of ADK or the use of gene therapy vectors to downregulate ADK expression. More recently, the first human mutations in ADK have been described, and novel findings suggest an unexpected role of ADK in a wider range of pathologies. ADK-regulating strategies thus represent innovative therapeutic opportunities to reconstruct network homeostasis in a multitude of conditions. This review will provide a comprehensive overview of the genetics, biochemistry, and pharmacology of ADK and will then focus on pathologies and therapeutic interventions. Challenges to translate ADK-based therapies into clinical use will be discussed critically. PMID:23592612

Boison, Detlev

2013-07-01

86

Adenosine Kinase: Exploitation for Therapeutic Gain  

PubMed Central

Adenosine kinase (ADK; EC 2.7.1.20) is an evolutionarily conserved phosphotransferase that converts the purine ribonucleoside adenosine into 5?-adenosine-monophosphate. This enzymatic reaction plays a fundamental role in determining the tone of adenosine, which fulfills essential functions as a homeostatic and metabolic regulator in all living systems. Adenosine not only activates specific signaling pathways by activation of four types of adenosine receptors but it is also a primordial metabolite and regulator of biochemical enzyme reactions that couple to bioenergetic and epigenetic functions. By regulating adenosine, ADK can thus be identified as an upstream regulator of complex homeostatic and metabolic networks. Not surprisingly, ADK dysfunction is involved in several pathologies, including diabetes, epilepsy, and cancer. Consequently, ADK emerges as a rational therapeutic target, and adenosine-regulating drugs have been tested extensively. In recent attempts to improve specificity of treatment, localized therapies have been developed to augment adenosine signaling at sites of injury or pathology; those approaches include transplantation of stem cells with deletions of ADK or the use of gene therapy vectors to downregulate ADK expression. More recently, the first human mutations in ADK have been described, and novel findings suggest an unexpected role of ADK in a wider range of pathologies. ADK-regulating strategies thus represent innovative therapeutic opportunities to reconstruct network homeostasis in a multitude of conditions. This review will provide a comprehensive overview of the genetics, biochemistry, and pharmacology of ADK and will then focus on pathologies and therapeutic interventions. Challenges to translate ADK-based therapies into clinical use will be discussed critically. PMID:23592612

2013-01-01

87

Human 3-Phosphoadenosine 5-Phosphosulfate Synthetase (Isoform 1, Brain): Kinetic Properties of the Adenosine Triphosphate Sulfurylase and Adenosine  

E-print Network

of the Adenosine Triphosphate Sulfurylase and Adenosine 5-Phosphosulfate Kinase Domains Eric B. Lansdon, Andrew J triphosphate (ATP) sulfurylase and an adenosine 5-phosphosulfate (APS) kinase domain, catalyzes the overall and kinetically characterized. The native enzyme, a dimer with each 71 kDa subunit containing an adenosine

Fisher, Andrew J.

88

Antinociception by adenosine analogs and an adenosine kinase inhibitor: dependence on formalin concentration  

Microsoft Academic Search

Spinal administration of adenosine analogs and an adenosine kinase inhibitor produces antinociception in thermal threshold tests. In the present study, we determined the effects of N6-cyclohexyladenosine (adenosine A1 receptor selective), 2-[p-(2-carboxyethyl)phenylethylamino]-5?-N-ethyl-carboxamidoadenosine (CGS-21680) (adenosine A2A receptor selective), and 5?-N-ethylcarboxamidoadenosine (NECA) (non-selective), on formalin induced nociceptive responses (flinching\\/lifting and licking\\/biting) using two concentrations of formalin (2% and 5%). We also examined the

Anthony Poon; Jana Sawynok

1995-01-01

89

Adenosine, Adenosine Receptors and Their Role in Glucose Homeostasis and Lipid Metabolism  

PubMed Central

Adenosine is an endogenous metabolite that is released from all tissues and cells including liver, pancreas, muscle and fat, particularly under stress, intense exercise, or during cell damage. The role of adenosine in glucose homeostasis has been attributed to its ability to regulate, through its membrane receptors, processes such as insulin secretion, glucose release and clearance, glycogenolysis, and glycogenesis. Additionally, adenosine and its multiple receptors have been connected to lipid metabolism by augmenting insulin-mediated inhibition of lipolysis, and the subsequent increase in free fatty acids and glycerol levels. Furthermore, adenosine was reported to control liver cholesterol synthesis, consequently affecting plasma levels of cholesterol and triglycerides, and the amount of fat tissue. Alterations in the balance of glucose and lipid homeostasis have implications in both cardiovascular disease and diabetes. The ability of different adenosine receptors to activate and inhibit the same signaling cascades has made it challenging to study the influence of adenosine, adenosine analogs and their receptors in health and disease. This review focuses on the role and significance of different adenosine receptors in mediating the effect of adenosine on glucose and lipid homeostasis. PMID:23460239

Koupenova, Milka; Ravid, Katya

2013-01-01

90

Genetics Home Reference: Adenosine deaminase 2 deficiency  

MedlinePLUS

... diseases Additional NIH Resources National Institutes of Health Educational resources Information pages Patient support For patients and families ... or management of adenosine deaminase 2 deficiency in Educational resources and Patient support . General information about the diagnosis ...

91

Hot Spot Mutations in Adenosine Deaminase Deficiency  

Microsoft Academic Search

We have previously characterized mutant adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4) enzymes in seven children with partial ADA deficiency. Six children shared common origins, suggesting a common progenitor. However, we found evidence for multiple phenotypically different mutant enzymes. We hypothesized that many of the mutations would be at CpG dinucleotides, hot spots at which spontaneous deamination of 5-methylcytosine results

Rochelle Hirschhorn; Stephanie Tzall; Amy Ellenbogen

1990-01-01

92

Role of adenosine receptors in caffeine tolerance  

SciTech Connect

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.

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

1991-01-01

93

Functional selectivity of adenosine receptor ligands  

Microsoft Academic Search

Adenosine receptors are plasma membrane proteins that transduce an extracellular signal into the interior of the cell. Basically\\u000a every mammalian cell expresses at least one of the four adenosine receptor subtypes. Recent insight in signal transduction\\u000a cascades teaches us that the current classification of receptor ligands into agonists, antagonists, and inverse agonists relies\\u000a very much on the experimental setup that

Dennis Verzijl; Ad P. IJzerman

2011-01-01

94

Electrocardiographic profile of adenosine pharmacological stress testing  

PubMed Central

Adenosine stress testing in conjunction with radionuclide myocardial perfusion imaging has become a common approach for the detection of coronary artery diseases in patients who are unable to perform adequate levels of exercise. However, specific electrocardiographic alterations during the test have been rarely described. Using a Chinese population, the aim of the present study was to provide a detailed electrocardiographic profile of adenosine stress testing. The study population included 1,168 consecutive outpatients who had undergone adenosine-induced stress myocardial perfusion imaging. Electrocardiographic data during and immediately following the adenosine infusion were collected, and the corresponding myocardial perfusion images were assessed. During adenosine infusion, 174 transient and 47 persistent arrhythmic events occurred in 110 patients (9.42%). Furthermore, frequent premature atrial contractions occurred in 65 individuals and frequent premature ventricular contractions were observed in 73 individuals. Atrioventricular block (AVB) occurred in 75 patients [first degree (I°) AVB, 16; second degree (II°) AVB, 58; third degree AVB, 1), while sinoatrial block occurred in eight patients. ST depression emerged in 69 patients. Patients with a baseline I° AVB had an increased risk of a II° AVB, and patients exhibiting baseline ST depression were more likely to have a further depressed ST segment during the stress test (odds ratio, 28.68 and 5.01, respectively; both P<0.001). Following adenosine infusion, 10 patients (0.86%) exhibited newly occurred arrhythmic events. However, no patient presented with acute myocardial infarction or sudden mortality. In conclusion, the results demonstrated that adenosine infusion was a safe method, despite the relatively high incidence of arrhythmic events. The majority of arrhythmias that occurred during infusion were transient, were reversible with the termination of infusion and did not indicate abnormal perfusion results. PMID:25780406

SUN, HAO; TIAN, YUEQIN; ZHENG, LIHUI; PAN, QINGRONG; XIE, BOQIA

2015-01-01

95

Conversion of adenosine(5?)oligophospho(5?)adenosines into inosn(5?)oligophospho(5?)inosines by non-specific adenylate deaminase from the snail Helix pomatia  

Microsoft Academic Search

Until now, the catabolism of adenosine(5?)triphospho(5?)adenosine (Ap3A) and adenosine(5?)tetraphospho(5?)adenosine (Ap4A) has been thought to commence with either hydrolytic or phosphorolytic cleavage of their oligophosphate chains, depending on the organism. Here, we show that in the extracts from the retractile ‘foot’ of the snail Helix pomatia deamination predominates; the adenosine moieties of these and other adenosine(5?)oligophospho(5?)adenosines (ApnAs) undergo successive deamination leading,

A. Guranowski; E. Starzy?ska; M. A. Günther Sillero; A. Sillero

1995-01-01

96

Role of Adenosine Signaling in Penile Erection and Erectile Disorders  

PubMed Central

Introduction Penile erection is a hemodynamic process, which results from increased flow and retention of blood in the penile organ due to the relaxation of smooth muscle cells. Adenosine, a physiological vasorelaxant, has been shown to be a modulator of penile erection. Aim To summarize the research on the role of adenosine signaling in normal penile erection and erectile disorders. Main Outcome Measures Evidence in the literature on the association between adenosine signaling and normal and abnormal penile erection, i.e., erectile dysfunction (ED) and priapism. Methods The article reviews the literature on the role of endogenous and exogenous adenosine in normal penile erection, as well as in erectile disorders namely, ED and priapism. Results Adenosine has been shown to relax corpus cavernosum from various species including human in both in vivo and in vitro studies. Neuromodulatory role of adenosine in corpus cavernosum has also been demonstrated. Impaired adenosine signaling through A2B receptor causes partial resistance of corpus cavernosum, from men with organic ED, to adenosine-mediated relaxation. Increased level of adenosine has been shown to be a causative factor for priapism. Conclusion Overall, the research reviewed here suggests a general role of exogenous and endogenous adenosine signaling in normal penile erection. From this perspective, it is not surprising that impaired adenosine signaling is associated with ED, and excessive adenosine signaling is associated with priapism. Adenosine signaling represents a potentially important diagnostic and therapeutic target for the treatment of ED and priapism. PMID:19889148

Phatarpekar, Prasad V.; Wen, Jiaming; Xia, Yang

2010-01-01

97

Radioimmunochemical quantitation of human adenosine deaminase.  

PubMed Central

Markedly reduced or absent adenosine deaminase activity in man is associated with an autosomal recesive form of severe conbined immunodeficiency disease. To further define the genetic nature of this enzyme defect, we have quantitated immunologically active adenosine deaminase (CRM) in the hemolysate of homozygous deficient patients and their heterozygous parents. A highly specific radioimmunoassay was developed capable of detecting 0.05% of normal erythrocyte adenosine deaminase. Hemolysates from nine heterozygotes (five families) showed a wide range in CRM (32--100% of normal) and variable absolute specific activities with several being at least 1 SD BELOW THE NORMAL MEAN. Hemolysates from four unrelated patients showed less than 0.09% adenosine deaminase activity with CRM ranging from less than 0.06 to 5.6% of the normal mean. In conclusion, heterozygote and homozygote hemolysates from five of the eight families analyzed revealed variable levels of CRM suggesting heterogeneous genetic alteration or expression of the silent or defective allele(s) of adenosine deaminase. PMID:468994

Daddona, P E; Frohman, M A; Kelley, W N

1979-01-01

98

Adenosine hypothesis of schizophrenia –opportunities for pharmacotherapy  

PubMed Central

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

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

2011-01-01

99

The adenosine kinase hypothesis of epileptogenesis.  

PubMed

Current therapies for epilepsy are largely symptomatic and do not affect the underlying mechanisms of disease progression, i.e. epileptogenesis. Given the large percentage of pharmacoresistant chronic epilepsies, novel approaches are needed to understand and modify the underlying pathogenetic mechanisms. Although different types of brain injury (e.g. status epilepticus, traumatic brain injury, stroke) can trigger epileptogenesis, astrogliosis appears to be a homotypic response and hallmark of epilepsy. Indeed, recent findings indicate that epilepsy might be a disease of astrocyte dysfunction. This review focuses on the inhibitory neuromodulator and endogenous anticonvulsant adenosine, which is largely regulated by astrocytes and its key metabolic enzyme adenosine kinase (ADK). Recent findings support the "ADK hypothesis of epileptogenesis": (i) Mouse models of epileptogenesis suggest a sequence of events leading from initial downregulation of ADK and elevation of ambient adenosine as an acute protective response, to changes in astrocytic adenosine receptor expression, to astrocyte proliferation and hypertrophy (i.e. astrogliosis), to consequential overexpression of ADK, reduced adenosine and - finally - to spontaneous focal seizure activity restricted to regions of astrogliotic overexpression of ADK. (ii) Transgenic mice overexpressing ADK display increased sensitivity to brain injury and seizures. (iii) Inhibition of ADK prevents seizures in a mouse model of pharmacoresistant epilepsy. (iv) Intrahippocampal implants of stem cells engineered to lack ADK prevent epileptogenesis. Thus, ADK emerges both as a diagnostic marker to predict, as well as a prime therapeutic target to prevent, epileptogenesis. PMID:18249058

Boison, Detlev

2008-03-01

100

Adenosine kinase as a new selective marker in somatic cell genetics: Isolation of adenosine kinase-deficient mouse cell lines and human-mouse hybrid cell lines containing adenosine kinase  

Microsoft Academic Search

A new selective system for isolating somatic cell hybrids, using adenosine kinase as the selective marker, has been developed. The selective medium for forward selection (to select for cells containing adenosine kinase) contains alanosine, adenosine and uridine. To survive in the presence of alanosine, cells must have adenosine kinase in order to utilize exogenous adenosine as the sole source of

Teh-sheng Chan; Richard P. Creagan; M. Patricia Reardon

1978-01-01

101

Double-Stranded RNA Adenosine Deaminases ADAR1 and ADAR2 Have Overlapping Specificities  

E-print Network

Double-Stranded RNA Adenosine Deaminases ADAR1 and ADAR2 Have Overlapping Specificities Katrina A, 2000 ABSTRACT: Adenosine deaminases that act on RNA (ADARs) deaminate adenosines to produce inosines adenosine in vivo. Adenosine deaminases that act on RNA (ADARs)1 deami- nate adenosines to produce inosines

Bass, Brenda L.

102

Structure of Human Adenosine Kinase at 1.5 Ĺ Resolution † , ‡  

Microsoft Academic Search

Adenosine kinase (AK) is a key enzyme in the regulation of extracellular adenosine and intracellular adenylate levels. Inhibitors of adenosine kinase elevate adenosine to levels that activate nearby adenosine receptors and produce a wide variety of therapeutically beneficial activities. Accordingly, AK is a promising target for new analgesic, neuroprotective, and cardioprotective agents. We determined the structure of human adenosine kinase

Irimpan I. Mathews; Mark D. Erion; Steven E. Ealick

1998-01-01

103

Astrocytic adenosine kinase regulates basal synaptic adenosine levels and seizure activity but not activity-dependent adenosine release in the hippocampus.  

PubMed

Adenosine is an endogenous inhibitor of excitatory synaptic transmission with potent anticonvulsant properties in the mammalian brain. Given adenosine's important role in modulating synaptic transmission, several mechanisms exist to regulate its extracellular availability. One of these is the intracellular enzyme adenosine kinase (ADK), which phosphorylates adenosine to AMP. We have investigated the role that ADK plays in regulating the presence and effects of extracellular adenosine in area CA1 of rat hippocampal slices. Inhibition of ADK activity with 5'-iodotubercidin (IODO; 5 muM) raised extracellular adenosine, as measured with adenosine biosensors, and potently inhibited field excitatory post-synaptic potentials (fEPSPs) in an adenosine A(1)R-dependent manner. In nominally Mg(2+)-free aCSF, which facilitated the induction of electrically-evoked epileptiform activity, adenosine biosensor recordings revealed that seizures were accompanied by the transient release of adenosine. Under these conditions, IODO also inhibited the fEPSP and greatly suppressed epileptiform activity evoked by brief, high-frequency stimulation. During spontaneous seizures evoked by the A(1)R antagonist CPT, adenosine release was unaffected by IODO. This suggests that ADK activity does not limit activity-dependent adenosine release. On the basis of strong ADK immunoreactivity in GFAP-positive cells, astrocytes are likely to play a key role in regulating basal adenosine levels. It is this action of ADK on the basal adenosine tone that is permissive to seizure activity, and, by extension, other forms of activity-dependent neuronal activity such as synaptic plasticity. PMID:18957298

Etherington, Lori-An V; Patterson, Graham E; Meechan, Louise; Boison, Detlev; Irving, Andrew J; Dale, Nicholas; Frenguelli, Bruno G

2009-02-01

104

Renal Deoxyadenosine Transport and Immunodeficiency Associated with Adenosine Deaminase Deficiency  

Microsoft Academic Search

Accumulation of deoxyadenosine (or possibly adenosine) is thought to mediate the immune defect associated with adenosine deaminase deficiency. It is postulated that deoxyadenosine is particularly immunosuppressive in the neonate due to an undeveloped renal secretory mechanism.

J. Arly Nelson

1989-01-01

105

Pain-relieving prospects for adenosine receptors and ectonucleotidases  

PubMed Central

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

Zylka, Mark J.

2010-01-01

106

Working memory and the homeostatic control of brain adenosine by adenosine kinase.  

PubMed

The neuromodulator adenosine maintains brain homeostasis and regulates complex behaviour via activation of inhibitory and excitatory adenosine receptors (ARs) in a brain region-specific manner. AR antagonists such as caffeine have been shown to ameliorate cognitive impairments in animal disease models but their effects on learning and memory in normal animals are equivocal. An alternative approach to reduce AR activation is to lower the extracellular tone of adenosine, which can be achieved by up-regulating adenosine kinase (ADK), the key enzyme of metabolic adenosine clearance. However, mice that globally over-express an Adk transgene ('Adk-tg' mice) were devoid of a caffeine-like pro-cognitive profile; they instead exhibited severe spatial memory deficits. This may be mechanistically linked to cortical/hippocampal N-methyl-d-aspartate receptor (NMDAR) hypofunction because the motor response to acute MK-801 was also potentiated in Adk-tg mice. Here, we evaluated the extent to which the behavioural phenotypes of Adk-tg mice might be modifiable by up-regulating adenosine levels in the cortex/hippocampus. To this end, we investigated mutant 'fb-Adk-def' mice in which ADK expression was specifically reduced in the telencephalon leading to a selective increase in cortical/hippocampal adenosine, while the rest of the brain remained as adenosine-deficient as in Adk-tg mice. The fb-Adk-def mice showed an even greater impairment in spatial working memory and a more pronounced motor response to NMDAR blockade than Adk-tg mice. These outcomes suggest that maintenance of cortical/hippocampal adenosine homeostasis is essential for effective spatial memory and deviation in either direction is detrimental with increased expression seemingly more disruptive than decreased expression. PMID:22521820

Singer, P; McGarrity, S; Shen, H-Y; Boison, D; Yee, B K

2012-06-28

107

Working memory and the homeostatic control of brain adenosine by adenosine kinase  

PubMed Central

The neuromodulator adenosine maintains brain homeostasis and regulates complex behaviour via activation of inhibitory and excitatory adenosine receptors (ARs) in a brain region-specific manner. AR antagonists such as caffeine have been shown to ameliorate cognitive impairments in animal disease models but their effects on learning and memory in normal animals are equivocal. An alternative approach to reduce AR activation is to lower the extracellular tone of adenosine, which can be achieved by up-regulating adenosine kinase (ADK), the key enzyme of metabolic adenosine clearance. However, mice that globally over-express an Adk transgene (‘Adk-tg’ mice) were devoid of a caffeine-like pro-cognitive profile; they instead exhibited severe spatial memory deficits. This may be mechanistically linked to cortical/hippocampal N-methyl-D-aspartate receptor (NMDAR) hypofunction because the motor response to acute MK-801 was also potentiated in Adk-tg mice. Here, we evaluated the extent to which the behavioural phenotypes of Adk-tg mice might be modifiable by up-regulating adenosine levels in the cortex/hippocampus. To this end, we investigated mutant ‘fb-Adk-def’ mice in which ADK expression was specifically reduced in the telencephalon leading to a selective increase in cortical/hippocampal adenosine, while the rest of the brain remained as adenosine-deficient as in Adk-tg mice. The fb-Adk-def mice showed an even greater impairment in spatial working memory and a more pronounced motor response to NMDAR blockade than Adk-tg mice. These outcomes suggest that maintenance of cortical/hippocampal adenosine homeostasis is essential for effective spatial memory and deviation in either direction is detrimental with increased expression seemingly more disruptive than decreased expression. PMID:22521820

Singer, Philipp; McGarrity, Stéphanie; Shen, Hai-Ying; Boison, Detlev; Yee, Benjamin K.

2012-01-01

108

Differential distribution of adenosine receptors in rat cochlea  

Microsoft Academic Search

Adenosine is a constitutive cell metabolite that can be released from cells via specific bi-directional transporters and is\\u000a an end-point for nucleotide hydrolysis. In the extracellular space, adenosine becomes a signalling molecule for P1 (adenosine)\\u000a receptors that modulate physiological responses in a wide range of mammalian tissues. Whereas adenosine signalling has been\\u000a implicated in the regulation of cochlear blood flow

Srdjan M. Vlajkovic; Shukri Abi; Carol J. H. Wang; Gary D. Housley; Peter R. Thorne

2007-01-01

109

Mechanisms of adenosine-induced renal vasodilatation in hypertensive patients  

Microsoft Academic Search

BACKGROUND: Adenosine is an endogenous nucleoside with potent vasodilatory capacities, released under ischaemic conditions in particular. Its mechanisms of action, however, remain elusive. OBJECTIVE: To evaluate the role of adenosine, using a non-selective purinergic receptor antagonist, and the possible involvement of nitric oxide in this mechanism. In addition, the production of renin and catecholamines was studied during infusion of adenosine,

Thomas KA Wierema; Alphons JHM Houben; Abraham A Kroon; Cornelis T Postma; Derk Koster; Jos MA van Engelshoven; Paul Smits; Peter W de Leeuw

2005-01-01

110

Transgenic overexpression of adenosine kinase aggravates cell death in ischemia  

Microsoft Academic Search

Adenosine is an endogenous neuromodulator with anticonvulsive and neuroprotective activity. Adenosine levels are normally kept in the range of 20 to 200 nmol\\/L by low basal expression of its main metabolic enzyme, adenosine kinase (ADK). Dysfunction of the adenosinergic system has been demonstrated to contribute to epileptogenesis. To investigate whether upregulation of ADK may render the brain more susceptible to

Giuseppe Pignataro; Roger P Simon; Detlev Boison

2007-01-01

111

Neonatal hepatic steatosis by disruption of the adenosine kinase gene  

Microsoft Academic Search

Neonatal hepatic steatosis (OMIM 228100) is a fatal condition of unknown etiology characterized by a pale and yellow liver and early postnatal mortality. In the present study, a deficit in adenosine-dependent metabolism is proposed as a causative factor. Physiologically, adenosine is efficiently metabolized to AMP by adenosine kinase (ADK), an enzyme highly expressed in liver. ADK not only ensures normal

Detlev Boison; Louis Scheurer; Valérie Zumsteg; Thomas Rülicke; Piotr Litynski; Brian Fowler; Sebastian Brandner; Hanns Mohler

2002-01-01

112

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...

113

Mechanism of Hydrolysis of Adenosine Triphosphate catalysed by Lobster Muscle  

Microsoft Academic Search

In previous publications1 evidence has been presented for the occurrence of displacement mechanisms in a wide variety of enzymatic reactions to which those of adenosine triphosphate are closely analogous. Assuming that the adenosine triphosphate reactions proceed by the same mechanisms, it can be deduced from the nature of the products that the adenosine triphosphate can undergo nucleophilic attack at any

Edith Clarke; D. E. Koshland

1953-01-01

114

Adenosine Kinase Inhibitor Design Bull. Korean Chem. Soc. 2007, Vol. 28, No. 4 561 Adenosine Kinase Inhibitor Design Based on Pharmacophore Modeling  

E-print Network

Adenosine Kinase Inhibitor Design Bull. Korean Chem. Soc. 2007, Vol. 28, No. 4 561 Adenosine Kinase-mail: kwlee@gnu.ac.kr Received October 9, 2006 Adenosine kinase (AK) is a ubiquitous intracellular enzyme and the two best compound structures from them were posted. Key Words : Adenosine (ADO), Adenosine kinase (AK

Lee, Keun Woo

115

The stability of adenosine deaminase and adenosine monophosphate (AMP) deaminase as potential spoilage indicators for postmortem ice stored shrimp  

E-print Network

THE STABILITY OF ADENOSINE DEAMINASE AND ADENOSINE MONOPHOSPHATE (AMP) DEAMINASE AS POTENTIAL SPOILAGE INDICATORS FOR POSTMORTEM ICE STORED SHRIMP A Thesis by WAI LUN CHEUK Submitted to the Graduate College of Texas A&M University in partial... fulfillment of the requirement for the degree of MASTER OF SCIENCE December 1978 Major Subject: Food Science and Technology THE STABILITY OF ADENOSINE DEAMINASE AND ADENOSINE MONOPHOSPHATE (AMP) DEAMINASE AS POTENTIAL SPOILAGE INDICATORS FOR POSTMORTEM...

Cheuk, Wai Lun

1978-01-01

116

Adenosine reagent-free detection by co-immobilization of adenosine deaminase and phenol red on an optical biostrip.  

PubMed

Adenosine detection in human serum is important because this ribonucleoside has established clinical applications, modulating many physiological processes. Furthermore, a simple and cheap detection method is useful in adenosine production processes. Adenosine can be determined enzymatically using either S-adenosyl-homocysteine hydrolase and (3) [H]-adenosine, or adenosine kinase combined with GTP and luciferase, or an amperometric biosensor carrying adenosine deaminase (ADA), purine nucleoside phosphorylase, and xanthine oxidase. We developed a simple and cheap method relying on a transparent biostrip bearing ADA and the indicator phenol red (PR), co-immobilized to polyacrylamide, itself chemically adhered to a derivatized glass strip. The ADA-catalyzed conversion of adenosine to inosine and ammonia leads to a local pH alteration, changing the absorbance maximum of PR (from 425 to 567 nm), which is measured optically. The biostrip shows an analytical range 0.05-1.5 mM adenosine and is reusable when stored at 4 °C. When the biostrip was tested with serum, spiked with adenosine (70 and 100 ?M), and filtered for protein and adenosine phosphates depletion, it showed good adenosine recovery. In summary, we show the proof-of-concept that adenosine can be determined reagent-free, at moderate sensitivity on an easy to construct, cheap, and reusable biostrip, based on commercially available molecular entities. PMID:25293641

Bartzoka, Foteini; Venetsanou, Katerina; Clonis, Yannis

2015-01-01

117

Expression of Human Adenosine Deaminase after Fusion of Adenosine Deaminase-Deficient Cells with Mouse Fibroblasts  

Microsoft Academic Search

Two human choriocarcinoma cell lines were shown to be deficient in adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4) such that they did not produce bands on starch gels after electrophoresis and histochemical staining. Radiometric assay indicated that their ADA specific activity was approximately 2% that of HeLa (human) cell controls. Subclone analysis of one of the lines indicated that this

Michael J. Siciliano; Mary R. Bordelon; Peter O. Kohler

1978-01-01

118

Site and event specific increase of striatal adenosine release by adenosine kinase inhibition in rats  

Microsoft Academic Search

The effects of the systemically administered adenosine kinase (AK) inhibitor, 5?-deoxy-5-iodotubercidin (5?d-5IT) on the striatal adenosine (ADO) release evoked by the excitotoxin, kainic acid (KA) were examined using rat bilateral striatal microdialysis. Local KA perfusion of one rat striatum caused a significant ipsilateral elevation of striatal ADO levels compared to basal and contralateral (artificial CSF-perfused) striatal ADO levels. KA-evoked striatal

Donald R. Britton; Joe Mikusa; Chih-Hung Lee; Michael F. Jarvis; Michael Williams; Elizabeth A. Kowaluk

1999-01-01

119

Prenatal diagnosis for adenosine deaminase deficiency  

Microsoft Academic Search

Amniocentesis was performed in two successive pregnancies of the mother of a child with adenosine deaminase (ADA) deficient severe combined immunodeficiency. Assay of ADA in amniotic fluid fibroblasts showed the pregnancies to be normal and homozygous deficient, respectively. These findings were confirmed by the demonstration of a normal level of erythrocyte ADA in the cord blood of the healthy male

J B Ziegler; M B Van der Weyden; C H Lee; A Daniel

1981-01-01

120

Adenosine deaminase deficiency with mosaicism for a \\  

Microsoft Academic Search

Four patients from 3 Saudi Arabian fami- lies had delayed onset of immune defi- ciency due to homozygosity for a novel intronic mutation, g.31701T>A, in the last splice acceptor site of the adenosine deaminase (ADA) gene. Aberrant splicing mutated the last 4 ADA amino acids and added a 43-residue \\

Francisco X. Arredondo-Vega; Ines Santisteban; Eva Richard; Pawan Bali; Majed Koleilat; Michael Loubser; Abdulaziz Al-Ghonaium; Mariam Al-Helali; Michael S. Hershfield

2002-01-01

121

Upregulation of adenosine kinase in Rasmussen encephalitis.  

PubMed

Rasmussen encephalitis (RE) is a rare neurologic disorder of childhood characterized by unihemispheric inflammation, progressive neurologic deficits, and intractable focal epilepsy. The pathogenesis of RE is still enigmatic. Adenosine is a key endogenous signaling molecule with anticonvulsive and anti-inflammatory effects, and our previous work demonstrated that dysfunction of the adenosine kinase (ADK)-adenosine system and astrogliosis are the hallmarks of epilepsy. We hypothesized that the epileptogenic mechanisms underlying RE are related to changes in ADK expression and that those changes might be associated with the development of epilepsy in RE patients. Immunohistochemistry was used to examine the expression of ADK and glial fibrillary acidic protein in surgically resected human epileptic cortical specimens from RE patients (n = 12) and compared with control cortical tissues (n = 6). Adenosine kinase expression using Western blot and enzymatic activity for ADK were assessed in RE versus control samples. Focal astrogliosis and marked expression of ADK were observed in the lesions of RE. Significantly greater ADK expression in RE versus controls was demonstrated by Western blot, and greater enzymatic activity for ADK was demonstrated using an enzyme-coupled bioluminescent assay. These results suggest that upregulation of ADK is a common pathologic hallmark of RE and that ADK might be a target in the treatment of epilepsy associated with RE. PMID:24128682

Luan, Guoming; Gao, Qing; Guan, Yuguang; Zhai, Feng; Zhou, Jian; Liu, Changqing; Chen, Yin; Yao, Kun; Qi, Xueling; Li, Tianfu

2013-11-01

122

Fluorescence sensing of adenosine deaminase based on adenosine induced self-assembly of aptamer structures.  

PubMed

A new approach is proposed for simple detection of adenosine deaminase (ADA) based on adenosine induced self-assembly of two pieces of single-stranded DNA (ssDNA). These ssDNA are two fragments of the aptamer that has a strong affinity for adenosine and are labeled with carboxyfluorescein and black hole quencher-1, respectively. The complementarities of the bases in the two pieces of ssDNA are insufficient to form a stable structure. In the presence of adenosine, however, the ssDNA can be assembled into the intact aptamer tertiary structure, which results in fluorescence quenching of the carboxyfluorescein-labeled aptamer fragment. As a result, the adenosine-ssDNA complex shows a low background signal, which is rather desired for achieving sensitive detection. Reaction of the complex with ADA causes a great fluorescence enhancement by converting adenosine into inosine that has no affinity for the aptamer. This behaviour leads to the development of a simple and sensitive fluorescent method for assaying ADA activity, with a detection limit of 0.05 U mL(-1), which is more sensitive than most of the existing approaches. Furthermore, the applicability of the method has been demonstrated by detecting ADA in mouse serum samples. PMID:23462984

Feng, Tingting; Ma, Huimin

2013-04-21

123

The support of adenosine release from adenosine kinase deficient ES cells by silk substrates.  

PubMed

Adenosine kinase deficient (Adk-/-) embryonic stem cells (ESCs) encapsulated in synthetic polymers have previously been shown to provide therapeutic adenosine release and transient seizure suppression in epileptic rats. Here we explored the utility of biopolymer-substrates to promote long-term adenosine release from Adk-/- ESCs. Three different substrates were studied: (1) type I collagen (Col-1), (2) silk-fibroin (SF), and (3) poly(L-ornithine) (PO) coated tissue culture plastic. Adk-/- or wild type (wt) ESC-derived glial precursor cells were seeded on the substrates and cultured either in proliferation medium containing growth factors or in differentiation medium devoid of growth factors. In proliferation medium cell proliferation was higher and metabolic activity lower on Col-1 and PO substrates as compared to SF. Cells from both genotypes readily differentiated into astrocytes after growth factor removal on all substrates. Adk-/- cells cultured on biopolymers released significantly more adenosine than their wt counterparts at all developmental stages. Adenosine release was similar on SF and PO substrates and the amounts released from Adk-/- cells (>20 ng/ml) were considered to be of therapeutic relevance. Taken together, these results suggest that silk matrices are particularly suitable biomaterials for ESC encapsulation and for the design of adenosine releasing bioincubators for the treatment of epilepsy. PMID:16709437

Uebersax, Lorenz; Fedele, Denise E; Schumacher, Claudia; Kaplan, David L; Merkle, Hans P; Boison, Detlev; Meinel, Lorenz

2006-09-01

124

Adenosine augmentation ameliorates psychotic and cognitive endophenotypes of schizophrenia.  

PubMed

An emerging theory of schizophrenia postulates that hypofunction of adenosine signaling may contribute to its pathophysiology. This study was designed to test the "adenosine hypothesis" of schizophrenia and to evaluate focal adenosine-based strategies for therapy. We found that augmentation of adenosine by pharmacologic inhibition of adenosine kinase (ADK), the key enzyme of adenosine clearance, exerted antipsychotic-like activity in mice. Further, overexpression of ADK in transgenic mice was associated with attentional impairments linked to schizophrenia. We observed that the striatal adenosine A2A receptor links adenosine tone and psychomotor response to amphetamine, an indicator of dopaminergic signaling. Finally, intrastriatal implants of engineered adenosine-releasing cells restored the locomotor response to amphetamine in mice overexpressing ADK, whereas the same grafts placed proximal to the hippocampus of transgenic mice reversed their working memory deficit. This functional double dissociation between striatal and hippocampal adenosine demonstrated in Adk transgenic mice highlights the independent contributions of these two interconnected brain regions in the pathophysiology of schizophrenia and thus provides the rationale for developing local adenosine augmentation therapies for the treatment of schizophrenia. PMID:22706302

Shen, Hai-Ying; Singer, Philipp; Lytle, Nikki; Wei, Catherine J; Lan, Jing-Quan; Williams-Karnesky, Rebecca L; Chen, Jiang-Fan; Yee, Benjamin K; Boison, Detlev

2012-07-01

125

Adenosine augmentation ameliorates psychotic and cognitive endophenotypes of schizophrenia  

PubMed Central

An emerging theory of schizophrenia postulates that hypofunction of adenosine signaling may contribute to its pathophysiology. This study was designed to test the “adenosine hypothesis” of schizophrenia and to evaluate focal adenosine-based strategies for therapy. We found that augmentation of adenosine by pharmacologic inhibition of adenosine kinase (ADK), the key enzyme of adenosine clearance, exerted antipsychotic-like activity in mice. Further, overexpression of ADK in transgenic mice was associated with attentional impairments linked to schizophrenia. We observed that the striatal adenosine A2A receptor links adenosine tone and psychomotor response to amphetamine, an indicator of dopaminergic signaling. Finally, intrastriatal implants of engineered adenosine-releasing cells restored the locomotor response to amphetamine in mice overexpressing ADK, whereas the same grafts placed proximal to the hippocampus of transgenic mice reversed their working memory deficit. This functional double dissociation between striatal and hippocampal adenosine demonstrated in Adk transgenic mice highlights the independent contributions of these two interconnected brain regions in the pathophysiology of schizophrenia and thus provides the rationale for developing local adenosine augmentation therapies for the treatment of schizophrenia. PMID:22706302

Shen, Hai-Ying; Singer, Philipp; Lytle, Nikki; Wei, Catherine J.; Lan, Jing-Quan; Williams-Karnesky, Rebecca L.; Chen, Jiang-Fan; Yee, Benjamin K.; Boison, Detlev

2012-01-01

126

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

PubMed Central

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

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

2012-01-01

127

Effect of Mineral Water Containing Calcium and Magnesium on Calcium Oxalate Urolithiasis Risk Factors  

Microsoft Academic Search

Calcium oxalate kidney stone formers are invariably advised to increase their fluid intake. In addition, magnesium therapy is often administered. Recently, a prospective study showed that a high dietary intake of calcium reduces the risk of symptomatic kidney stones. The present study was performed to test whether simultaneous delivery of these factors – high fluid intake, magnesium ingestion and increased

Allen L. Rodgers

1997-01-01

128

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

129

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

SciTech Connect

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 and dicotyledonous higher plants. Formation constants for the CaSO{sub 4}{sup 0} formation was confirmed, but the value of 10{sup 2.7} for CaSeO{sub 4}{sup 0} was found to be in error; a value of 10{sup 2.0} is proposed here as the correct formation constant. Five solution culture experiments were conducted using alfalfa (Medicago sativa L.) or tall wheatgrass (Elytrigia pontica [Podp.] Holub) with treatments consisting of NaSeO{sub 4} levels in combination with various levels of MgCl{sub 2} or CaCl{sub 2}. Both shoot Se concentrations and whole-plant Se contents were highly correlated with the free SeO{sub 4}{sup 2{minus}} activity but were poorly correlated with the sum of the free ion plus Ca and Mg ion pair species. Thus, the authors have shown, for the first time, that the free ion model of trace metal bioavailability is also valid for oxyanions that form complexes with Ca and Mg in saline media but that this conclusion hinges critically on the accuracy of the pertinent formation constants.

Parker, D.R.; Tice, K.R.; Thomason, D.N. [Univ. of California, Riverside, CA (United States). Dept. of Soil and Environmental Sciences

1997-03-01

130

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

Microsoft Academic Search

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

David W. Franzen; Ted R. Peck

1995-01-01

131

Calcium and magnesium ions and the regulation of multiplication in normal and transformed cells  

Microsoft Academic Search

THE relative importance of Ca2+ and Mg2+ in the regulation of cellular multiplication and alteration of that regulation by viral transformation has recently become a subject of considerable interest1-5. Extracellular Ca2+ and Mg2+ both have effects on metabolic parameters and macromolecular synthesis in cultured cells. Mg2+, because of its substrate level intracellular concentration and its role in macromolecular synthesis and

W. L. McKeehan; R. G. Ham

1978-01-01

132

Calcium and magnesium enhance arsenate rhizotoxicity and uptake in Triticum aestivum.  

PubMed

Cations such as calcium (Ca) and magnesium (Mg) alleviate toxicities of cationic toxicants and increase those of anionic toxicants such as arsenic (As) present as arsenate under aerobic conditions. Increasing evidence exists that these phenomena are related to the outer surface electrical potential (??0°) of the root cell plasma membrane (PM). Short-term (48-h) nutrient culture experiments with wheat (Triticum aestivum L.) seedlings investigated Ca and Mg effects on arsenate rhizotoxicity and uptake. Increased Ca and Mg in solution from 0.2 to 3.5 mM equally reduced the negativity of ??0° from -45 to -15 mV. This increased arsenate activity at the PM surface from 0.3 to 0.9 ľM at the same bulk concentration of 2.0 ľM NaH(2) AsO(4) consequently increased arsenate uptake and rhizotoxicity. However, increased Mg was more effective than Ca in enhancing As uptake by roots, especially with the activity of As in the range of 0.5 to 1.5 ľM in the bulk medium. This was explained by a modified electrostatic uptake model which indicated a mechanism other than through an effect on ??0°. Subcellular fractionation of roots indicated that > 95% of As was associated with cellular debris and heat-stable protein (HSP). The results of the present study show that Ca and Mg reduce the negativity of ??0°, increasing arsenate uptake and rhizotoxicity, and suggest that Mg is more efficient than Ca in enhancing the uptake of As due, in large part, to inducing greater As binding by peptides in the HSP fraction. PMID:21538485

Wang, Peng; Zhou, Dongmei; Weng, Nanyan; Wang, Dengjun; Peijnenburg, Willie J G M

2011-07-01

133

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

SciTech Connect

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.

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

2008-01-01

134

Factors affecting ex-situ aqueous mineral carbonation using calcium and magnesium silicate minerals  

SciTech Connect

Carbonation of magnesium- and calcium-silicate minerals to form their respective carbonates is one method to sequester carbon dioxide. Process development studies have identified reactor design as a key component affecting both the capital and operating costs of ex-situ mineral sequestration. Results from mineral carbonation studies conducted in a batch autoclave were utilized to design and construct a unique continuous pipe reactor with 100% recycle (flow-loop reactor). Results from the flow-loop reactor are consistent with batch autoclave tests, and are being used to derive engineering data necessary to design a bench-scale continuous pipeline reactor.

Gerdemann, Stephen J.; Dahlin, David C.; O'Connor, William K.; Penner, Larry R.; Rush, G.E.

2004-01-01

135

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...

136

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

Microsoft Academic Search

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

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

1973-01-01

137

Chemical, microstructural and strength development of calcium and magnesium carbonate binders  

Microsoft Academic Search

The influence of magnesium on the chemistry of calcium carbonate formation has been studied. It was found that the type of carbonate formed by subjecting compacts of Ca(OH)2 and Mg(OH)2 to carbon dioxide (up to 20 atm CO2 pressure) for variable periods of time is largely controlled by the molar proportion of calcium to magnesium in the initial mixture. Increasing magnesium

P. De Silva; L. Bucea; V. Sirivivatnanon

2009-01-01

138

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...

139

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

E-print Network

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 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...

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

140

THE EFFECT OF CALCIUM AND MAGNESIUM ON THE ACTIVITY OF BOVICIN HC5 AND NISIN  

Technology Transfer Automated Retrieval System (TEKTRAN)

Nisin is a cationic peptide (lantibiotic) that inhibits bacteria by inserting into cell membranes to form pores that dissipate ion gradients. Nisin resistance has been correlated with alterations in the cell surface of previously sensitive bacteria. Nisin-resistant bacteria have more lipoteichoic ...

141

Nitrogen, calcium, and magnesium fertilization affects growth and leaf elemental content of ‘dormanred’ raspberry  

Microsoft Academic Search

’Dormanred’ raspberry (Rubus species) plants grown in sand culture were subjected to varying concentrations of N, Ca, and Mg over a two?year period. Increasing nitrogen fertilization resulted in linear reductions of leaf Ca, K, Zn, Fe, and Mn but did not affect leaf Mg. Leaf Ca and K increased linearly with Ca fertilization, but applied Ca had an antagonistic influence

James M. Spiers

1993-01-01

142

Relief of casein inhibition of Bacillus stearothermophilus by iron, calcium, and magnesium.  

PubMed

Growth of Bacillus stearothermophilus strain NCA 1518 Smooth in Dextrose Tryptone Agar (DTA) was inhibited by sodium caseinate. Binding studies indicated that sodium caseinate, when present in DTA, had the capacity to effect an iron deficiency which could cause inhibition of growth. Additions of essential cations, iron (1 mM), calcium (5 mM), magnesium (10 mM), or hydrogen ion (pH 5.7), relieved inhibition. Responses to and interactions among these relief factors were analyzed statistically. Equations were fitted to the data and were used to estimate responses to all treatment combinations within the ranges tested. Results from these studies indicated that calcium, magnesium, and hydrogen ion acted by decreasing the binding capacity of the protein for iron, rendering this metal available for metabolic needs. Evidence was obtained that ferrous rather than ferric iron was the limiting factor in DTA containing sodium caseinate. PMID:5694503

Ashton, D H; Busta, F F; Warren, J A

1968-04-01

143

The effects of calcium and magnesium on sodium fluxes through gills of Carassius auratus, L  

PubMed Central

1. Removal of calcium from Carassius either with chelating agents or by adaptation to deionized water increased sodium influx through the gills twofold. 2. Treatment of fish with chelating agents increased sodium outflux, whereas adaptation to deionized water reduced sodium outflux. The effects on outflux do not appear to result from calcium removal. 3. Addition of calcium (2-20 mM) reversed the effects on influx of chelating agents and of adaptation to deionized water. 4. Magnesium (2-10 mM) was without significant effect on sodium influx, but increased the outflow in fish adapted to deionized water. PMID:4622716

Cuthbert, A. W.; Maetz, J.

1972-01-01

144

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

E-print Network

bovine milk, and this is beneticial to complete digestion by the infant. Bovine milk also has a higher renal solute load and can be detrimental to an infant's immature renal system. The whey protein:casein ratio, and the solute load, can be adjusted... times more magnesium, sulfur, chloride, manganese, zinc, iodine, and selenium than human milk, resulting in a higher renal solute load for the infant (4). As a result, infants fed bovine milk have a greater obligatory water requirement for renal...

Gallaway, Sheila Ann

1988-01-01

145

Calcium and magnesium dependence of phospholipase A2-catalyzed hydrolysis of phosphatidylcholine small unilamellar vesicles.  

PubMed

The Ca2+ requirement for lipid hydrolysis catalyzed by phospholipase A2 from Agkistrodon piscivorus piscivorus (App-D49) and porcine pancreas has been examined using small, unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC SUV). Hydrolysis was affected by product inhibition even at early times, and the extent of this inhibition depended on the concentration of divalent cations. The Ca2+ requirement for half-maximal rates of hydrolysis reflected, in part, this non-catalytic role of divalent cations. The presence of 10 mM Mg2+, a cation which does not support catalysis, reduced the Ca2+ required for half-maximal rates of hydrolysis from millimolar concentrations to 40 microM for App-D49. Since the dissociation constant of the enzyme for Ca2+ in solution is 2 mM, these results indicate a change in the interaction of the enzyme with Ca2+ under catalytic conditions. The kinetic dissociation constant of Ca2+ for the pancreatic enzyme was 20 microM which is substantially lower than the dissociation constant in solution, 0.35 mM. The similarity of apparent kinetic dissociation constants for these enzymes suggests that structurally similar features determine the affinity for Ca2+ under catalytic conditions. Evidence is presented that the affinity of phospholipase A2 for Ca2+ changes subsequent to the initial interaction of the enzyme with the substrate interface. However, the apparent Michaelis constant, KMapp, for App-D49, 0.03-0.06 mM, is independent of [Ca2+] and is about the same as the equilibrium dissociation constant for DPPC SUV, 0.14 mM. We thus suggest that KMapp is a steady-state constant. PMID:1400456

Lathrop, B K; Biltonen, R L

1992-10-25

146

THE EFFECT OF CALCIUM AND MAGNESIUM ON THE ACTIVITY OF BOVICIN HC5 AND NISIN  

Technology Transfer Automated Retrieval System (TEKTRAN)

Some Gram-positive bacteria produce small peptides (bacteriocins) that have antimicrobial activity, but many bacteria can become bacteriocin-resistant. Bovicin HC5, an antibiotic produced by Streptococcus bovis HC5, has the ability to inhibit nisin-resistant bacteria. Because nisin resistance has,...

147

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

NASA Astrophysics Data System (ADS)

The objective of this work was to study nutrients release from two compressed nitrogen-potassium-phosphorous (NPK) fertilizers. In the Lourizán Forest Center, tablet-type controlled-release fertilizers (CRF) were prepared by compressing various mixtures of fertilizers without covers or binders. We used soil columns (50 cm long and 7.3 cm inner diameter) that were filled with soil from the surface layer (0-20 cm) of an A horizon corresponding to a Cambic Umbrisol. Tablets of two slow-release NPK fertilizers (11-18-11 or 8-8-16) were placed into the soil (within the first 3 cm), and then water was percolated through the columns in a saturated regime for 80 days. Percolates were analyzed for N, P, K+, Ca2+ and Mg2+. These elements were also determined in soil and fertilizer tablets at the end of the trials. Nutrient concentrations were high in the first leachates and reached a steady state when 1426 mm of water had been percolated, which is equivalent to approximately 1.5 years of rainfall in this geographic area. In the whole trial, both tablets lost more than 80% of their initial N, P and K contents. However, K+, Ca2+ and Mg2+ were the most leached, whereas N and P were lost in leachates to a lesser extent. Nutrient release was slower from the tablet with a composition of 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, with a significant increase of pH, available Ca2+, Mg2+, K+, P and effective cation exchange capacity (eCEC) in the fertilized columns, as well as a significant decrease in exchangeable Al3+, reaching values < 0.08 cmol (+) kg-1.

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

2014-12-01

148

Dietary calcium and magnesium supplements in spontaneously hypertensive rats and isolated arterial reactivity.  

PubMed Central

1. High calcium diet attenuates the development of hypertension but an associated undesirable effect is that Mg2+ loss to the urine is enhanced. Therefore, we studied the effects of high calcium diet alone and in combination with increased magnesium intake on blood pressure and arterial function. 2. Forty-eight young spontaneously hypertensive rats (SHR) were allocated into four groups, the dietary contents of Ca2+ and Mg2+ being: 1.1%, 0.2% (SHR); 2.5%, 0.2% (Ca-SHR); 2.5%, 0.8% (CaMg-SHR); and 1.1%, 0.8% (Mg-SHR), respectively. Development of hypertension was followed for 13 weeks, whereafter electrolyte balance, lymphocyte intracellular free calcium ([Ca2+]i), and mesenteric arterial responses in vitro were examined. Forty normotensive Wistar-Kyoto (WKY) rats were investigated in a similar manner. 3. Calcium supplementation comparably attenuated the development of Lypertension during normal and high magnesium intake in SHR, with an associated reduced lymphocyte [Ca2+]i and increased Mg2+ loss to the urine. 4. Endothelium-dependent arterial relaxation to acetylcholine was augmented in Ca-SHR and CaMg-SHR, while the relaxations to isoprenaline and the nitric oxide donor SIN-1 were similar in all SHR groups. Relaxation responses induced by the return of K+ to the organ bath upon precontractions in K(+)-free solution were used to evaluate the function of arterial Na+, K(+)-ATPase. The rate of potassium relaxation was similar in Ca-SHR and CaMg-SHR and faster than in untreated SHR.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8564205

Mäkynen, H.; Kähönen, M.; Arvola, P.; Wuorela, H.; Vapaatalo, H.; Pörsti, I.

1995-01-01

149

Adenosine A(2) receptors modulate tubuloglomerular feedback.  

PubMed

Adenosine can mediate the tubuloglomerular (TGF) response via activation of A(1) receptors on the afferent arteriole, but both adenosine A(1) and A(2) receptors can regulate preglomerular resistance. We tested the hypothesis that adenosine A(2) receptors offset the effect of A(1) receptors and modulate the TGF. Maximal TGF responses were measured in male Sprague-Dawley rats as changes in proximal stop-flow pressure (DeltaP(SF)) in response to increased perfusion of the loop of Henle (0 to 40 nl/min) with artificial tubular fluid (ATF). The maximal TGF response was studied after 5 min of intratubular perfusion (10 nl/min) with ATF alone, or with ATF plus the A(2A) receptor antagonist (ZM-241385; 10(-7) or 10(-5) mol/l), A(1) receptor antagonist (PSB-36; 10(-8) mol/l), or with a combination of A(1) (PSB-36; 10(-8) mol/l) and A(2A) (ZM-241385; 10(-7) mol/l) antagonists. The maximal TGF response (DeltaP(SF)) with ATF alone was 11.7 +/- 1.0 mmHg. Specific A(2) inhibition (low dose) enhanced the maximal TGF response (15.7 +/- 0.8 mmHg; P < 0.01), whereas a high dose (unspecific inhibition) attenuated the response (5.0 +/- 0.4 mmHg; P < 0.001). A(1) inhibition alone led to a paradoxical TGF response, with an increase in P(SF) of 3.1 +/- 0.5 mmHg (P < 0.05). Simultaneous application of A(1) and A(2) antagonists abolished the TGF response (DeltaP(SF): 0.4 +/- 0.3 mmHg). In conclusion, adenosine A(2) receptors modulate the TGF response by counteracting the effects of adenosine A(1) receptors. PMID:20519378

Carlström, Mattias; Wilcox, Christopher S; Welch, William J

2010-08-01

150

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

E-print Network

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

Jackson, Sophie

151

Significance of adenosine metabolism of coronary smooth muscle cells.  

PubMed

A detailed understanding of adenosine metabolism of vascular smooth muscle cells (VSMC) is highly desirable to critically evaluate possible autocrine effects of adenosine in this cell species. Therefore, this study quantified intra- and extracellular adenosine flux rates, the transmembrane concentration gradient, and the adenosine surface concentration in porcine VSMC and, for comparison, aortic endothelial cells (PAEC). Cell-covered microcarrier beads packed in a chromatography column were superfused with a HEPES buffer. With the use of specific inhibitors of adenosine kinase (iodotubericidine, 10 microM), adenosine deaminase [erythro-9-(2-hydroxy-3-nonyl)-adenine, 5 microM], ecto-5'-nucleotidase (alpha,beta-methylene-adenosine 5'-diphosphate, 50 microM), and adenosine membrane transport (n-nitrobenzylthioinosine, 1 microM), total production rates of 12.3 +/- 2.7 and 7.5 +/- 1.3 pmol x min(-1) x microl cell volume(-1) were obtained for VSMC and PAEC, respectively. Despite prevailing intracellular adenosine production (76 and 70% of total production, respectively), transmembrane concentration gradients under control conditions were directed toward the cytosol as a result of rapid intracellular adenosine rephosphorylation and continuous extracellular hydrolysis from 5'-AMP. Surface concentrations were approximately 18 nM in VSMC and PAEC under control conditions and increased to approximately 60 nM during partial inhibition of adenosine metabolism. Simultaneously, the transmembrane adenosine concentration gradient was reversed. We conclude that adenosine flux rates in VSMC and PAEC are quantitatively similar and that VSMC may influence the interstitial adenosine concentration under basal steady-state conditions. PMID:11123225

Mattig, S; Deussen, A

2001-01-01

152

Voltage- and ion-dependent conductances in solitary vertebrate hair cells.  

PubMed

An important function of the peripheral auditory system is the resolution of complex sounds into their constituent frequency components. It is well established that each mechanoreceptive hair cell of the cochlea is maximally sensitive to a particular frequency of sound, but the mechanisms by which this sharp frequency selectivity is achieved are still controversial. The complex mechanical and hydrodynamic properties of the receptor organs and of the hair cells themselves are certainly involved. However, in at least one auditory organ, the turtle cochlea, frequency tuning is greatly enhanced by the electrical properties of the hair-cell membrane; each cell in this organ behaves as an electrical resonator tuned to a narrow band of frequencies. Using the 'Gigaseal', whole-cell recording technique, we have investigated the biophysical basis of similar resonant behaviour in enzymatically isolated hair cells from the bullfrog sacculus. We report here the identification of three voltage- and ion-dependent conductances which may contribute to the electrical tuning mechanism: a non-inactivating calcium conductance, an A-type K+ conductance, and a Ca2+-activated K+ conductance. PMID:6603579

Lewis, R S; Hudspeth, A J

153

Extracellular adenosine-mediated modulation of regulatory T cells.  

PubMed

Extracellular adenosine-dependent suppression and redirection of pro-inflammatory activities are mediated by the signaling through adenosine receptors on the surface of most immune cells. The immunosuppression by endogenously-produced adenosine is pathophysiologically significant since inactivation of A2A/A2B adenosine receptor (A2AR/A2BR) and adenosine-producing ecto-enzymes CD39/CD73 results in the higher intensity of immune response and exaggeration of inflammatory damage. Regulatory T cells (Treg) can generate extracellular adenosine, which is implicated in the immunoregulatory activity of Tregs. Interestingly, adenosine has been shown to increase the numbers of Tregs and further promotes their immunoregulatory activity. A2AR-deficiency in Tregs reduces their immunosuppressive efficacy in vivo. Thus, adenosine is not only directly and instantly inhibiting to the immune response through interaction with A2AR/A2BR on the effector cells, but also adenosine signaling can recruit other immunoregulatory mechanisms, including Tregs. Such interaction between adenosine and Tregs suggests the presence of a positive feedback mechanism, which further promotes negative regulation of immune system through the establishment of immunosuppressive microenvironment. PMID:25071765

Ohta, Akio; Sitkovsky, Michail

2014-01-01

154

Extracellular Adenosine-Mediated Modulation of Regulatory T Cells  

PubMed Central

Extracellular adenosine-dependent suppression and redirection of pro-inflammatory activities are mediated by the signaling through adenosine receptors on the surface of most immune cells. The immunosuppression by endogenously-produced adenosine is pathophysiologically significant since inactivation of A2A/A2B adenosine receptor (A2AR/A2BR) and adenosine-producing ecto-enzymes CD39/CD73 results in the higher intensity of immune response and exaggeration of inflammatory damage. Regulatory T cells (Treg) can generate extracellular adenosine, which is implicated in the immunoregulatory activity of Tregs. Interestingly, adenosine has been shown to increase the numbers of Tregs and further promotes their immunoregulatory activity. A2AR-deficiency in Tregs reduces their immunosuppressive efficacy in vivo. Thus, adenosine is not only directly and instantly inhibiting to the immune response through interaction with A2AR/A2BR on the effector cells, but also adenosine signaling can recruit other immunoregulatory mechanisms, including Tregs. Such interaction between adenosine and Tregs suggests the presence of a positive feedback mechanism, which further promotes negative regulation of immune system through the establishment of immunosuppressive microenvironment. PMID:25071765

Ohta, Akio; Sitkovsky, Michail

2014-01-01

155

Therapeutic epilepsy research: from pharmacological rationale to focal adenosine augmentation.  

PubMed

Epilepsy is a common seizure disorder affecting approximately 70 million people worldwide. Current pharmacotherapy is neuron-centered, frequently accompanied by intolerable side effects, and fails to be effective in about one third of patients. Therefore, new therapeutic concepts are needed. Recent research suggests an astrocytic basis of epilepsy, presenting the possibility of novel therapeutic targets. In particular, dysfunction of the astrocyte-controlled, endogenous, adenosine-based seizure control system of the brain is implicated in seizure generation. Thus, astrogliosis - a pathological hallmark of the epileptic brain - is associated with upregulation of the adenosine-removing enzyme adenosine kinase (ADK), resulting in focal adenosine deficiency. Both astrogliotic upregulation of ADK in epilepsy and transgenic overexpression of ADK are associated with seizures, and inhibition of ADK prevents seizures in a mouse model of pharmacoresistant epilepsy. These findings link adenosine deficiency with seizures and predict that adenosine augmentation therapies (AATs) will likely be effective in preventing seizures. Given the wide-spread systemic and central side effects of systemically administered AATs, focal AATs (i.e., limited to the astrogliotic lesion) are a necessity. This Commentary will discuss the pharmacological rationale for the development of focal AATs. Additionally, several AAT strategies will be discussed: (1) adenosine released from silk-based brain implants; (2) adenosine released from locally implanted encapsulated cells; (3) adenosine released from stem cell-derived brain implants; and (4) adenosine augmenting gene therapies. Finally, new developments and therapeutic challenges in using focal AATs for epilepsy therapy will critically be evaluated. PMID:19682439

Boison, Detlev; Stewart, Kerry-Ann

2009-12-15

156

[Adenosine deaminase in severe combined immunodeficiency syndrome].  

PubMed

Adenosine deaminase is an enzyme of the purine metabolism whose function is to convert adenosine to inosine and deoxyadenosine to deoxyinosine. The ecto-ADA1 binding to the cell surface through CD26 contributes to the regulation of cytokines and stimulates the proliferation of T cells by activating CD45. The deficiency of this enzyme generates the severe combined immunodeficiency syndrome, characterized by the accumulation of deoxyadenosine and adenine metabolites, which have toxic effects on lymphocytes, affecting DNA synthesis and consequently, clonal expansion. Early diagnosis of this immunodeficiency is essential, as it significantly reduces morbidity and mortality associated with recurrent infections. Recent advances in molecular biology and genetics have led to the identification of genetic defects of many primary immunodeficiencies and the development of promising diagnostic tools and treatment. PMID:23248974

Pérez-Aguilar, Mary Carmen; Goncalves, Loredana; Bonfante-Cabarcas, Rafael

2012-09-01

157

Adenosine Receptors: Expression, Function and Regulation  

PubMed Central

Adenosine receptors (ARs) comprise a group of G protein-coupled receptors (GPCR) which mediate the physiological actions of adenosine. To date, four AR subtypes have been cloned and identified in different tissues. These receptors have distinct localization, signal transduction pathways and different means of regulation upon exposure to agonists. This review will describe the biochemical characteristics and signaling cascade associated with each receptor and provide insight into how these receptors are regulated in response to agonists. A key property of some of these receptors is their ability to serve as sensors of cellular oxidative stress, which is transmitted by transcription factors, such as nuclear factor (NF)-?B, to regulate the expression of ARs. Recent observations of oligomerization of these receptors into homo- and heterodimers will be discussed. In addition, the importance of these receptors in the regulation of normal and pathological processes such as sleep, the development of cancers and in protection against hearing loss will be examined. PMID:24477263

Sheth, Sandeep; Brito, Rafael; Mukherjea, Debashree; Rybak, Leonard P.; Ramkumar, Vickram

2014-01-01

158

Selective Deletion of the A1 Adenosine Receptor Abolishes Heart-Rate Slowing Effects of Intravascular Adenosine In Vivo  

PubMed Central

Objective Intravenous adenosine induces temporary bradycardia. This is due to the activation of extracellular adenosine receptors (ARs). While adenosine can signal through any of four ARs (A1AR, A2AAR, A2BAR, A3AR), previous ex vivo studies implicated the A1AR in the heart-rate slowing effects. Here, we used comparative genetic in vivo studies to address the contribution of individual ARs to the heart-rate slowing effects of intravascular adenosine. Methods and Results We studied gene-targeted mice for individual ARs to define their in vivo contribution to the heart-rate slowing effects of adenosine. Anesthetized mice were treated with a bolus of intravascular adenosine, followed by measurements of heart-rate and blood pressure via a carotid artery catheter. These studies demonstrated dose-dependent slowing of the heart rate with adenosine treatment in wild-type, A2AAR?/?, A2BAR?/?, or A3AR?/? mice. In contrast, adenosine-dependent slowing of the heart-rate was completely abolished in A1AR?/? mice. Moreover, pre-treatment with a specific A1AR antagonist (DPCPX) attenuated the heart-rate slowing effects of adenosine in wild-type, A2AAR?/?, or A2BAR?/? mice, but did not alter hemodynamic responses of A1AR?/? mice. Conclusions The present studies combine pharmacological and genetic in vivo evidence for a selective role of the A1AR in slowing the heart rate during adenosine bolus injection. PMID:19707555

Eltzschig, Holger K.

2009-01-01

159

Gene therapy for adenosine deaminase deficiency.  

PubMed

In the last decade, gene therapy for adenosine deaminase deficiency has been developed as a successful alternative strategy to allogeneic bone marrow transplant and enzyme replacement therapy. Infusion of autologous hematopoietic stem cells, corrected ex vivo by retroviral vectors and combined to low-intensity conditioning regimen, has resulted in immunologic improvement, metabolic correction, and long-term clinical benefits. These findings have opened the way to applications of gene therapy in other primary immune deficiencies using novel vector technology. PMID:20493400

Cappelli, Barbara; Aiuti, Alessandro

2010-05-01

160

Effect of adenosine and adenosine analogs on ( sup 14 C)aminopyrine accumulation by rabbit parietal cells  

SciTech Connect

Adenosine receptors that modulate adenylate cyclase activity have been identified recently in a number of tissues. Adenosine A2 receptor is stimulatory to adenylate cyclase, whereas adenosine A1 receptor is inhibitory to adenylate cyclase. We investigated the effect of adenosine and its analogs on (14C)aminopyrine accumulation by rabbit parietal cells. Rabbit gastric mucosal cells were isolated by enzyme digestion. Parietal cells were enriched by nonlinear percoll gradients. (14C)Aminopyrine accumulation was used as an indicator of acid secretion. The effect of 2-chloroadenosine on histamine-stimulated (14C)aminopyrine accumulation was studied. The effects of N-ethylcarboxamideadenosine, 2-chloroadenosine, stable analogs of adenosine, and adenosine on (14C)aminopyrine accumulation were assessed. Cyclic AMP content of parietal cells was determined by radioimmunoassay. Histamine and carbachol, known secretagogues, stimulated (14C)aminopyrine accumulation. 2-Chloroadenosine did not suppress histamine-stimulated (14C)aminopyrine accumulation. 2-Chloroadenosine, N-ethylcarboxamideadenosine, and adenosine dose dependently increased (14C)aminopyrine accumulation. The order of potency was N-ethylcarboxamideadenosine greater than 2-chloroadenosine greater than adenosine. 8-Phenyltheophylline and theophylline, adenosine-receptor antagonists, or cimetidine did not have significant effects on the increase of AP uptake induced by 2-chloroadenosine. Coadministration of dipyridamole, and adenosine uptake inhibitor, augmented the effect of adenosine on (14C)aminopyrine accumulation. 2-Chloroadenosine, N-ethylcarboxamideadenosine, and adenosine each induced a significant increase in cellular cyclic AMP. We conclude that there may be adenosine A2 receptors on rabbit parietal cells which modulate gastric acid secretion.

Ota, S.; Hiraishi, H.; Terano, A.; Mutoh, H.; Kurachi, Y.; Shimada, T.; Ivey, K.J.; Sugimoto, T. (Univ. of Tokyo (Japan))

1989-12-01

161

Use of adenosine echocardiography for diagnosis of coronary artery disease  

SciTech Connect

Two-dimensional echocardiography combined with exercise is sensitive and specific in the detection of coronary artery disease (CAD) by demonstrating transient abnormalities in wall motion. Frequently, however, patients cannot achieve maximal exercise because of various factors. Pharmacologic stress testing with intravenous adenosine was evaluated as a means of detecting CAD in a noninvasive manner. Patients with suspected CAD underwent echocardiographic imaging and simultaneous thallium 201 single-photon emission computed tomography during the intravenous administration of 140 micrograms/kg/min of adenosine. An increase in heart rate, decrease in blood pressure, and increase in double product were observed during adenosine administration. Initial observations revealed that wall motion abnormalities were induced by adenosine in areas of perfusion defects. The adenosine infusion was well tolerated, and symptoms disappeared within 1 to 2 minutes after termination of the infusion. Therefore preliminary observations suggest that adenosine echocardiography appears to be useful in the assessment of CAD.

Zoghbi, W.A. (Section of Cardiology Baylor College of Medicine, Methodist Hospital, Houston, TX (USA))

1991-07-01

162

Adenosine kinase, epilepsy and stroke: mechanisms and therapies.  

PubMed

Adenosine is an inhibitory modulator of brain activity with neuroprotective and anticonvulsant properties. Adenosine levels are regulated mainly by adenosine kinase (ADK), an enzyme that is responsible for the removal of adenosine via phosphorylation to AMP. Recent evidence indicates that expression of ADK undergoes rapid coordinated changes during brain development and following brain injury, such as after epileptic seizures and stroke. Thus, transient downregulation of ADK after acute brain injury protects the brain from seizures and cell death. Conversely, chronic overexpression of ADK causes seizures in epilepsy and promotes cell death in epilepsy and stroke. These findings have direct implications for the rational definition of ADK as a therapeutic target. In recent years, novel treatment strategies have been developed that make use of the intracerebral transplantation of cells that are ADK deficient and, thus, release adenosine. A new era of cell-based delivery of adenosine has begun, which holds great promise for novel therapies for epilepsy and stroke. PMID:17056128

Boison, Detlev

2006-12-01

163

Adenosine signaling promotes regeneration of pancreatic ?-cells in vivo  

PubMed Central

Diabetes can be controlled with insulin injections, but a curative approach that restores the number of insulin-producing ?-cells is still needed. Using a zebrafish model of diabetes, we screened ~7000 small molecules to identify enhancers of ?-cell regeneration. The compounds we identified converge on the adenosine signaling pathway and include exogenous agonists and compounds that inhibit degradation of endogenously produced adenosine. The most potent enhancer of ?-cell regeneration was the adenosine agonist 5?-N-Ethylcarboxamidoadenosine (NECA), which acting through the adenosine receptor A2aa increased ?-cell proliferation and accelerated restoration of normoglycemia in zebrafish. Despite markedly stimulating ?-cell proliferation during regeneration, NECA had only a modest effect during development. The proliferative and glucose-lowering effect of NECA was confirmed in diabetic mice, suggesting an evolutionarily conserved role for adenosine in ?-cell regeneration. With this whole-organism screen, we identified components of the adenosine pathway that could be therapeutically targeted for the treatment of diabetes. PMID:22608007

Andersson, Olov; Adams, Bruce A.; Yoo, Daniel; Ellis, Gregory C.; Gut, Philipp; Anderson, Ryan M.; German, Michael S.; Stainier, Didier Y. R.

2012-01-01

164

Role of adenosine receptor subtypes in methamphetamine reward and reinforcement.  

PubMed

The neurobiology of methamphetamine (MA) remains largely unknown despite its high abuse liability. The present series of studies explored the role of adenosine receptors on MA reward and reinforcement and identified alterations in the expression of adenosine receptors in dopamine terminal areas following MA administration in rats. We tested whether stimulating adenosine A1 or A2A receptor subtypes would influence MA-induced place preference or MA self-administration on fixed and progressive ratio schedules in male Sprague-Dawley rats. Stimulation of either adenosine A1 or A2A receptors significantly reduced the development of MA-induced place preference. Stimulating adenosine A1, but not A2A, receptors reduced MA self-administration responding. We next tested whether repeated experimenter-delivered MA administration would alter the expression of adenosine receptors in the striatal areas using immunoblotting. We observed no change in the expression of adenosine receptors. Lastly, rats were trained to self-administer MA or saline for 14 days and we detected changes in adenosine A1 and A2A receptor expression using immunoblotting. MA self-administration significantly increased adenosine A1 in the nucleus accumbens shell, caudate-putamen and prefrontal cortex. MA self-administration significantly decreased adenosine A2A receptor expression in the nucleus accumbens shell, but increased A2A receptor expression in the amygdala. These findings demonstrate that MA self-administration produces selective alterations in adenosine receptor expression in the nucleus accumbens shell and that stimulation of adenosine receptors reduces several behavioral indices of MA addiction. Together, these studies shed light onto the neurobiological alterations incurred through chronic MA use that may aid in the development of treatments for MA addiction. PMID:25301277

Kavanagh, Kevin A; Schreiner, Drew C; Levis, Sophia C; O'Neill, Casey E; Bachtell, Ryan K

2015-02-01

165

Adenosine kinase from rat liver: new biochemical properties.  

PubMed

Adenosine kinase is a well-known enzyme which catalyzes the phosphorylation of adenosine to AMP: Its metabolic and kinetic properties are well studied. Here, we report new properties of rat liver enzyme, demonstrating a new reaction: ADP can be a phosphate donor instead ATP, according to the reaction: adenosine + ADP --> 2AMP) demonstrating the efficiency of AdK to phosphorylate adenosine, also starting from ADP. Cells could exploited this property in situations in which ATP levels are strongly decreased and ADP decreases slowly. PMID:17065073

Leoncini, R; Vannoni, D; Santoro, A; Giglioni, S; Carli, R; Marinello, E

2006-01-01

166

Changes in extracellular adenosine during chemical or electrical brain stimulation.  

PubMed

The purpose of this study was to determine the changes in adenosine and adenosine metabolites during graded electrical stimulation or kainic acid-induced activation and to assess the role of adenosine in the cerebral blood flow (CBF) response to increased brain activity. A modified brain microdialysis technique was used to sample cerebral interstitial fluid (ISF), deliver drugs locally to the brain, electrically stimulate the brain, and measure local CBF (H2 clearance). Microdialysis probes were implanted bilaterally in the caudate nuclei of ketamine-anesthetized rats. Graded electrical stimulation at 5, 15, and 30 Hz increased dialysate adenosine 1.5-fold, 2.3-fold, and 4.7-fold, respectively. Local infusion of kainic acid, an agonist of the excitatory amino acid neurotransmitter glutamate, produced a transient increase (2-fold) in dialysate adenosine and sustained increases in dialysate inosine (2-fold), hypoxanthine (4-fold) and CBF (2.4-fold). When the adenosine receptor antagonist 8(p-sulphophenyl)-theophylline (SPT, 10(-3) M) was co-administered with kainic acid, CBF increased only 1.6-fold, while the increase in dialysate adenosine was augmented by 40%. These data demonstrate that ISF adenosine increases during brain activation and suggest that adenosine contributes to active hyperemia in the brain. PMID:8348299

Sciotti, V M; Park, T S; Berne, R M; Van Wylen, D G

1993-06-01

167

The Molecular Mechanism of Ion-Dependent Gating in Secondary Transporters  

PubMed Central

LeuT-like fold Na-dependent secondary active transporters form a large family of integral membrane proteins that transport various substrates against their concentration gradient across lipid membranes, using the free energy stored in the downhill concentration gradient of sodium ions. These transporters play an active role in synaptic transmission, the delivery of key nutrients, and the maintenance of osmotic pressure inside the cell. It is generally believed that binding of an ion and/or a substrate drives the conformational dynamics of the transporter. However, the exact mechanism for converting ion binding into useful work has yet to be established. Using a multi-dimensional path sampling (string-method) followed by all-atom free energy simulations, we established the principal thermodynamic and kinetic components governing the ion-dependent conformational dynamics of a LeuT-like fold transporter, the sodium/benzyl-hydantoin symporter Mhp1, for an entire conformational cycle. We found that inward-facing and outward-facing states of Mhp1 display nearly the same free energies with an ion absent from the Na2 site conserved across the LeuT-like fold transporters. The barrier separating an apo-state from inward-facing or outward-facing states of the transporter is very low, suggesting stochastic gating in the absence of ion/substrate bound. In contrast, the binding of a Na2 ion shifts the free energy stabilizing the outward-facing state and promoting substrate binding. Our results indicate that ion binding to the Na2 site may also play a key role in the intracellular thin gate dynamics modulation by altering its interactions with the transmembrane helix 5 (TM5). The Potential of Mean Force (PMF) computations for a substrate entrance displays two energy minima that correspond to the locations of the main binding site S1 and proposed allosteric S2 binding site. However, it was found that substrate's binds to the site S1 ?5 kcal/mol more favorable than that to the site S2 for all studied bound combinations of ions and a substrate. PMID:24204233

Zhao, Chunfeng; Noskov, Sergei Yu.

2013-01-01

168

Elevated adenosine signaling via adenosine A2B receptor induces normal and sickle erythrocyte sphingosine kinase 1 activity.  

PubMed

Erythrocyte possesses high sphingosine kinase 1 (SphK1) activity and is the major cell type supplying plasma sphingosine-1-phosphate, a signaling lipid regulating multiple physiological and pathological functions. Recent studies revealed that erythrocyte SphK1 activity is upregulated in sickle cell disease (SCD) and contributes to sickling and disease progression. However, how erythrocyte SphK1 activity is regulated remains unknown. Here we report that adenosine induces SphK1 activity in human and mouse sickle and normal erythrocytes in vitro. Next, using 4 adenosine receptor-deficient mice and pharmacological approaches, we determined that the A2B adenosine receptor (ADORA2B) is essential for adenosine-induced SphK1 activity in human and mouse normal and sickle erythrocytes in vitro. Subsequently, we provide in vivo genetic evidence that adenosine deaminase (ADA) deficiency leads to excess plasma adenosine and elevated erythrocyte SphK1 activity. Lowering adenosine by ADA enzyme therapy or genetic deletion of ADORA2B significantly reduced excess adenosine-induced erythrocyte SphK1 activity in ADA-deficient mice. Finally, we revealed that protein kinase A-mediated extracellular signal-regulated kinase 1/2 activation functioning downstream of ADORA2B underlies adenosine-induced erythrocyte SphK1 activity. Overall, our findings reveal a novel signaling network regulating erythrocyte SphK1 and highlight innovative mechanisms regulating SphK1 activity in normal and SCD. PMID:25587035

Sun, Kaiqi; Zhang, Yujin; Bogdanov, Mikhail V; Wu, Hongyu; Song, Anren; Li, Jessica; Dowhan, William; Idowu, Modupe; Juneja, Harinder S; Molina, Jose G; Blackburn, Michael R; Kellems, Rodney E; Xia, Yang

2015-03-01

169

Adenosine signaling in normal and sickle erythrocytes and beyond  

PubMed Central

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 A2B receptor (ADORA2B) activation, suggesting that elevated adenosine has an unrecognized role in normal erythrocytes to promote O2 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 A2A 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

Zhang, Yujin; Xia, Yang

2012-01-01

170

Adenosine: Tipping the balance towards hepatic steatosis and fibrosis  

PubMed Central

Fatty liver is commonly associated with alcohol ingestion and abuse. While the molecular pathogenesis of these fatty changes is well understood, the histochemical 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:20395005

Robson, Simon C.; Schuppan, Detlef

2010-01-01

171

Characterization of the Residual Adenosine Deaminating Activity in the Spleen of a Patient with Combined Immunodeficiency Disease and Adenosine Deaminase Deficiency  

Microsoft Academic Search

A number of infants with an autosomal recessive form of combined immunodeficiency disease also lack adenosine deaminase (adenosine aminohydrolase; EC 3.5.4.4) activity in their erythrocytes. Other tissues from these infants contain only a few percent of the adenosine-deaminating activity present in corresponding normal tissue. The residual adenosine-deaminating activity in extracts from the spleen of a combined immunodeficient, adenosine deaminase-deficient patient

William P. Schrader; Bernard Pollara; Hilaire J. Meuwissen

1978-01-01

172

Too much of a good thing: adenosine overload in adenosine-deaminase-deficient mice  

Microsoft Academic Search

Chronic lung diseases are associated with persistent lung inflammation and damage. The mechanisms that govern the chronic nature of these disorders are not known. Adenosine is a signaling nucleoside that is generated in hypoxic environments such as that found in the inflamed lung, which suggests that it might serve a regulatory role in chronic lung diseases. Support for this hypothesis

Michael R Blackburn

2003-01-01

173

Introduction to Adenosine Receptors as Therapeutic Targets  

PubMed Central

Adenosine acts as a cytoprotective modulator in response to stress to an organ or tissue. Although short-lived in the circulation, it can activate four sub-types of G protein-coupled adenosine receptors (ARs): A1, A2A, A2B, and A3. The alkylxanthines caffeine and theophylline are the prototypical antagonists of ARs, and their stimulant actions occur primarily through this mechanism. For each of the four AR subtypes, selective agonists and antagonists have been introduced and used to develop new therapeutic drug concepts. ARs are notable among the GPCR family in the number and variety of agonist therapeutic candidates that have been proposed. The selective and potent synthetic AR agonists, which are typically much longer lasting in the body than adenosine, have potential therapeutic applications based on their anti-inflammatory (A2A and A3), cardioprotective (preconditioning by A1 and A3 and postconditioning by A2B), cerebroprotective (A1 and A3), and antinociceptive (A1) properties. Potent and selective AR antagonists display therapeutic potential as kidney protective (A1), antifibrotic (A2A), neuroprotective (A2A), and antiglaucoma (A3) agents. AR agonists for cardiac imaging and positron-emitting AR antagonists are in development for diagnostic applications. Allosteric modulators of A1 and A3 ARs have been described. In addition to the use of selective agonists/antagonists as pharmacological tools, mouse strains in which an AR has been genetically deleted have aided in developing novel drug concepts based on the modulation of ARs. PMID:19639277

Jacobson, Kenneth A.

2012-01-01

174

RNA EDITING BY ADENOSINE DEAMINASES THAT ACT ON RNA  

E-print Network

RNA EDITING BY ADENOSINE DEAMINASES THAT ACT ON RNA Brenda L. Bass Department of Biochemistry-mail: bbass@howard.genetics.utah.edu Key Words double-stranded RNA, inosine, deaminase, neurotransmission f An Overview of RNA Editing by Adenosine Deamination . . . . . . . . . . . . . . 818 THE ENZYME FAMILY

Bass, Brenda L.

175

Human in vivo research on the vascular effects of adenosine.  

PubMed

In situations of impending tissue danger, such as during ischaemia, the concentration of the endogenous purine nucleoside adenosine rapidly increases. Subsequent stimulation of G-protein coupled adenosine receptors induces several cardiovascular effects, such as vasodilation, inhibition of inflammation, modulation of sympathetic nervous system activity, and increasing myocardial tolerance against ischaemia-reperfusion, which are all aimed at protecting the affected tissue. Although animal models have consistently shown profound cardiovascular protection by adenosine, up to now translation of this knowledge into clinical practice is limited. This current review is focused on human in vivo studies on the cardiovascular effects of adenosine. Several techniques, such as microdialysis, venous occlusion plethysmography, and (99m)Tc-annexin A5 scintigraphy can be used to study these effects of adenosine in healthy volunteers in vivo. By use of these techniques, recent studies have shown that the cardiovascular effects of adenosine can be modulated by genetic factors (e.g. a single nucleotide polymorphism in the gene encoding for adenosine monophosphate deaminase), by metabolic factors (e.g. by the plasma homocysteine concentration), and by drugs, such as caffeine, dipyridamole, and methotrexate. Given the cardiovascular protective properties of adenosine, these factors could well modulate the risk or extent of cardiovascular disease in patients and knowledge of these factors could be of benefit in daily clinical practice to optimize treatment in patients with cardiovascular disease. PMID:18417123

Riksen, Niels P; Rongen, Gerard A; Yellon, Derek; Smits, Paul

2008-05-13

176

Isolation, characterization and immunological properties of bovine liver adenosine kinase  

SciTech Connect

Adenosine kinase catalyzes the transfer of phosphate from nucleoside triphosphates to adenosine. It also is important in the phosphorylation of adenosine analogs active as anti-cancer and anti-viral drugs. Adenosine kinase from bovine liver was purified by sequential chromatography on DEAE-Sephacel, hydroxylapatite, Ultrogel AcA54, octyl Sepharose, and heptylamine-Sepharose. It exhibited one major band (approx.40 kDa) by sodium dodecylsulfate-polyacrylamide gel electrophoresis and a single peak of similar size by gel permeation chromatography. (/sup 35/S) GTP..gamma..S binding was stimulated in the presence of Mg/sup 2 +/ and adenosine. The K/sub m/ for adenosine was 2.6 ..mu..M. Antibodies raised in rabbits to adenosine kinase, after purification on Protein A-and adenosine kinase-Sepharose, were used to screen several bovine tissues. A 40 kDa immunoreactive protein was most abundant in liver, but was also detected in heart; it was found predominantly in soluble fractions. Antibodies did not significantly cross-react with other guanyl nucleotide-binding proteins.

Noda, M.; Kunz, B.C.; Tsai, S.C.; Adamik, R.; Murtagh, J.J.; Chen, H.C.; Moss, J.; Vaughan, M.

1987-05-01

177

Anticonvulsant and Antinociceptive Actions of Novel Adenosine Kinase Inhibitors  

Microsoft Academic Search

Adenosine (ADO) acts as an inhibitory neuromodulator throughout the central and peripheral nervous system and can regulate seizure and nociceptive activity. However, the positive actions of systemically administered ADO are usually accompanied by undesirable side effects such as hypomobility and cardio-suppression. Adenosine kinase (AK) is the primary metabolic enzyme regulating intra- and extracellular concentrations of ADO. We review the recent

Steve McGaraughty; Marlon Cowart; Michael F. Jarvis; Robert F. Berman

2005-01-01

178

Recombinant expression, purification, and characterization of Toxoplasma gondii adenosine kinase  

Microsoft Academic Search

Toxoplasma gondii lacks the capacity to synthesize purines de novo, and adenosine kinase (AK)-mediated phosphorylation of salvaged adenosine provides the major route of purine acquisition by this parasite. T. gondii AK thus represents a promising target for rational design of antiparasitic compounds. In order to further our understanding of this therapeutically relevant enzyme, an AK cDNA from T. gondii was

John A Darling; William J Sullivan; Darrick Carter; Buddy Ullman; David S Roos

1999-01-01

179

ORAL PRESENTATION Open Access Double-stranded RNA adenosine deaminase  

E-print Network

ORAL PRESENTATION Open Access Double-stranded RNA adenosine deaminase ADAR1 enhances both T cell. This family of cytokines activates the expression of antiviral proteins, such as the protein kinase R (PKR), an inhibitor of viral mRNA translation, and the double-stranded RNA adenosine deaminase ADAR1. ADAR1 has

Paris-Sud XI, UniversitĂŠ de

180

Minor-Groove-Modulating Adenosine Replacements Control Protein Binding and  

E-print Network

-binding proteins. The RNA-dependent protein kinase (PKR) and adenosine deaminase that acts on RNA 1 (ADAR1) are twoMinor-Groove-Modulating Adenosine Replacements Control Protein Binding and RNAi Activity in si (TLRs) 3 (8, 9), 7 (10, 11), and 8 (12) and the RNA- dependent protein kinase (PKR) (7). Retinoic acid

Beal, Peter A.

181

Novel carboxaldehyde mediated synthetic pathway for 5'-amino adenosine analogues.  

PubMed

Modifications of the 5'-position of adenosine have been prepared via a novel 5'-carboxaldehyde synthon. The described methodology should prove useful for making related compounds in which amine-derived moieties off the 5'-position of adenosine (or related nucleoside congeners) can be easily incorporated via reductive amination, especially for the incorporation of aromatic amines. PMID:25874943

Gibbons, Garrett S; Showalter, Hollis D; Nikolovska-Coleska, Zaneta

2015-05-01

182

Norepinephrines effect on adenosine transport in the proximal straight tubule  

SciTech Connect

The effect of norepinephrine on C/sup 14/-adenosine transport in the rabbit proximal tubule (S/sub 2/) was studied. The transepithelial transport of adenosine (0.02 mM0 from lumin to bathing solution was measured by its rate of appearance (J/sub A/) in the bathing solution and by its disappearances (J/sub D/) from the luminal fluid. Norepinephrine (0.24 ..mu..M) was added to the bathing solution after a control flux period. After three samples from the experiment period the tubules were quickly harvested and the cellular concentration of C/sup 14/-adenosine was determined. The high cellular adenosine concentration and th marked difference in adenosine appearance rate in the bathing solution compared to the luminal disappearance rate indicates the absorbed adenosine is trapped in the cells. This trapping may be due to adenosine metabolism or difficulty of crossing the basolateral membrane. Whichever is the case, norepinephrine appears to stimulate movement of adenosine or its metabolites into the bathing solution across the basolateral membrane.

Barfuss, D.W.; McCann, W.P.; Katholi, R.E.

1986-03-01

183

Role of adenosine in status epilepticus: a potential new target?  

PubMed

The homeostatic bioenergetic network regulator adenosine is an endogenous anticonvulsant of the brain that plays critical roles in seizure termination and postictal refractoriness. Adenosine homeostasis in the adult brain is largely under the control of metabolic clearance through adenosine kinase (ADK), expressed predominantly in astrocytes. The role of adenosine in status epilepticus (SE) appears to be a double-edged sword. We demonstrated that the severity of an SE clearly depends on the expression levels of ADK. A genetic knockdown of ADK prevented SE in a mouse model, whereas transgenic overexpression of the enzyme aggravated the SE. Therefore, ADK inhibition or adenosine augmentation might be a therapeutic strategy to terminate or attenuate an SE. On the other hand, SE triggers a surge of endogenous adenosine, which may initiate secondary events leading to epileptogenesis. Two new findings point into this direction: (1) Elevated adenosine triggers changes in the epigenome; and (2) SE triggers transient changes in ADK expression, which have been linked to neurogenesis. Although the ADK/adenosine system is an attractive target for the attenuation of an SE, the same system may also trigger downstream events related to epileptogenesis. PMID:24001064

Boison, Detlev

2013-09-01

184

Cultured astrocytes do not release adenosine during hypoxic conditions  

Microsoft Academic Search

Recent reports based on a chemiluminescent enzymatic assay for detection of adenosine conclude that cultured astrocytes release adenosine during mildly hypoxic conditions. If so, astrocytes may suppress neural activity in early stages of hypoxia. The aim of this study was to reevaluate the observation using high-performance liquid chromatography (HPLC). The HPLC analysis showed that exposure to 20 or 120 minutes

Takumi Fujita; Erika K Williams; Tina K Jensen; Nathan A Smith; Takahiro Takano; Kim Tieu; Maiken Nedergaard

2012-01-01

185

Neurologic abnormalities in patients with adenosine deaminase deficiency.  

PubMed

Defects in adenosine deaminase enzyme cause severe immunodeficiency. Without enzyme replacement or allogeneic bone marrow transplantation, patients often suffer fatal infection in infancy. Adenosine deaminase is expressed ubiquitously; deficiency may affect various organs, including the brain. Neurologic abnormalities occur in some adenosine deaminase-deficient patients, mostly in association with infection or after bone marrow transplantation. Three cases with significant neurologic abnormalities, including hypotonia, head lag, nystagmus, difficulty in focusing gaze, seizure disorder, and moderate-severe developmental delay but with no evidence of infection or transplant-related medication toxicity are presented. Computed tomographic scans and cranial MRI revealed volume loss and abnormalities of basal ganglia and thalamus, which may reflect accelerated nerve cell death or altered stimulation of adenosine receptors. Detailed neurologic and neuroimaging evaluation should be performed for all patients with adenosine deaminase deficiency upon diagnosis, to identify potentially significant brain lesions. PMID:17765813

Nofech-Mozes, Yehuda; Blaser, Susan I; Kobayashi, Jeff; Grunebaum, Eyal; Roifman, Chaim M

2007-09-01

186

Adenine\\/Ribose Supply Increases Adenosine Production and Protects ATP Pool in Adenosine Kinase-inhibited Cardiac Cells  

Microsoft Academic Search

The objective of the present study was to establish the optimal combination of inhibitors of adenosine metabolism and nucleotide precursors resulting in long-term increase in endogenous adenosine concentration without adverse metabolic consequences in non-ischemic cardiomyocytes and endothelial cells. Cardiomyocytes and endothelial cells were isolated after collagenase digestion of the rat heart. Freshly isolated cardiac myocytes or cultured endothelial cells were

Ryszard T Smolenski; Kameljit K Kalsi; Marek Zych; Zdzislaw Kochan; Magdi H Yacoub

1998-01-01

187

Adenosine or adenosine triphosphate for supraventricular tachycardias? Comparative double-blind randomized study in patients with spontaneous or inducible arrhythmias.  

PubMed

The effects of intravenous adenosine and adenosine triphosphate (ATP) were studied in a double-blind randomized study during 68 episodes of supraventricular tachycardia in 39 patients. Adenosine restored sinus rhythm in 20 patients (25 of 27 episodes) and produced atrioventricular block to reveal atrial arrhythmias in nine. ATP restored sinus rhythm in 17 patients (22 of 25 episodes) and revealed atrial tachyarrhythmias in six. In patients receiving both compounds, the effective dosage of adenosine was 3.8 mg and of ATP it was 6.6 mg (p less than 0.05), suggesting molar equipotency. Transient side effects were common, occurring in 81% of episodes with adenosine and in 94% with ATP. Symptom scores (0 to 10) were not significantly different (median score for adenosine was 5, for ATP it was 6). Adenosine and ATP were equally effective for the diagnosis and treatment of supraventricular tachycardias and the incidence and severity of side effects were similar. Adenosine has the advantage of being more stable. PMID:2405610

Rankin, A C; Oldroyd, K G; Chong, E; Dow, J W; Rae, A P; Cobbe, S M

1990-02-01

188

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

PubMed

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

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

2015-01-01

189

Adenosine deaminase in disorders of purine metabolism and in immune deficiency  

SciTech Connect

This book consists of five parts and a section of poster papers. Some of the selection titles are: Adenosine Deaminase Impairment and Ribonucleotide Reductase in Human Cells; Adenosine Deaminase and Malignant Cells; Inhibition of Adenosine Deaminase to Increase the Antitumor Activity of Adenine Nucleoside Analogues; and Molecular Biology of the Adenosine Deaminase Gene and Messenger RNA.

Tritsch, G.L.

1985-01-01

190

Adenosine-A3 receptors in neutrophil microdomains promotetheformationofbacteria-tetheringcytonemes  

E-print Network

MLP-mediated chemotaxis by addition of exogenous adenosine deaminase suggests that G-protein-coupled adenosine receptorsAdenosine-A3 receptors in neutrophil microdomains promotetheformationofbacteria of Pharmacy, University of Nottingham, Nottingham, UK The A3-adenosine receptor (A3AR) has recently emerged

Nizet, Victor

191

Nucleoside analog studies indicate mechanistic differences between RNA-editing adenosine  

E-print Network

Nucleoside analog studies indicate mechanistic differences between RNA-editing adenosine deaminases, 2012 ABSTRACT Adenosine deaminases acting on RNA (ADAR1 and ADAR2) are human RNA-editing adenosine is adenosine de- amination catalyzed by the ADAR family of enzymes (ad- enosine deaminases acting on RNA

Beal, Peter A.

192

Adenosine deamination in human transcripts generates novel microRNA binding sites  

E-print Network

RNAs), and adenosine-to-inosine (A-to-I) editing, generated by adenosine deaminases that act on double-stranded RNA-to-inosine (A-to-I) RNA editing catalyzed by dsRNA-specific ADAR (adenosine deaminase acting on RNA) refersAdenosine deamination in human transcripts generates novel microRNA binding sites Glen M. Borchert1

Bhattacharya, Debashish

193

Cloning and Expression of the Adenosine Kinase Gene from Rat and Human Tissues  

Microsoft Academic Search

Adenosine kinase is ubiquitous in eukaryotes and is a key enzyme in the regulation of the intracellular levels of adenosine, an important physiological effector of many cells and tissues. In this paper we report the cloning of cDNAs encoding adenosine kinase from both rat and human tissues. Two distinct forms of adenosine kinase mRNA were identified in human tissues. Sequence

Teresa McNally; Rosalind J. Helfrich; Marlon Cowart; Sarah A. Dorwin; Joseph L. Meuth; Kenneth B. Idler; Kimberly A. Klute; Robert L. Simmer; Elizabeth A. Kowaluk; Donald N. Halbert

1997-01-01

194

Decreased Expression of Adenosine Kinase in Streptozotocin-Induced Diabetes Mellitus Rats  

Microsoft Academic Search

Adenosine has been implicated as an important endogenous regulator of various tissue functions. In diabetes, the responsiveness of several tissues to adenosine is altered. The aim of this study was to investigate the activities of enzymes metabolizing adenosine in tissues of diabetic rats. The cytosolic activity (Vmax) of adenosine kinase (AK) was decreased by 50% in the kidney and by

Tadeusz Pawelczyk; Monika Sakowicz; Miroslawa Szczepanska-Konkel; Stefan Angielski

2000-01-01

195

Extracellular adenosine controls NKT-cell-dependent hepatitis induction.  

PubMed

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

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

2014-04-01

196

Identification of possible adenosine receptors in vascular smooth muscle  

SciTech Connect

Adenosine is a vasodilator and has been implicated in increased blood flow in tissues that undergo energy deficiency. During conditions such as hypoxia and ischemia, adenosine is produced and is said to increase blood flow by relaxing the vascular smooth muscle (VSM) lining the resistance vessels. The goal of this research was to identify receptors that might be responsible for adenosine-mediated VSM relaxation. When an insoluble fraction from calf aortic VSM was incubated with /sup 32/P-ATP, two components were phosphorylated. One was identified as myosin light chain by MW, pl, and immunoprecipitation. The other product was identified as phosphatidylinositol-4-phosphate (DPI) by tic. Both phosphorylations were inhibited by adenosine and by 5'-chloro-5'-deoxyadenosine (Cl-Ado). DPI production was much more sensitive to the nucleosides than was myosin phosphorylation. Neither inhibition involved change in cAMP production. Phosphatidylinositol (Pl) kinase in the VSM membranes required magnesium, was activated and solubilized by Triton X-100, and phosphorylated both endogenous and exogenous Pl. Cl-Ado inhibited Pl kinase in a manner competitive with respect to ATP and noncompetitive with respect to Pl. Adenosine and adenosine analogs modified in the ribose ring were inhibitors with potencies comparable to that of Cl-Ado. Adenine nucleotides and purine-modified adenosine analogs were weaker inhibitors than Cl-Ado.

Doctrow, S.R.

1985-01-01

197

Role of adenosine signalling and metabolism in ?-cell regeneration  

SciTech Connect

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?.

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

2014-02-01

198

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

Microsoft Academic Search

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

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

1992-01-01

199

Increased Cortical Extracellular Adenosine Correlates with Seizure Termination  

PubMed Central

Objective Seizures are currently defined by their electrographic features. However, neuronal networks are intrinsically dependent upon neurotransmitters of which little is known regarding their peri-ictal dynamics. Evidence supports adenosine as having a prominent role in seizure termination, as its administration can terminate and reduce seizures in animal models. Further, microdialysis studies in humans suggest adenosine is elevated peri-ictally, but the relationship to the seizure is obscured by its temporal measurement limitations. Because electrochemical techniques can provide vastly superior temporal resolution, we test the hypothesis that extracellular adenosine concentrations rise during seizure termination in an animal model and humans using electrochemistry. Methods White farm swine (n=45) were used in an acute cortical model of epilepsy and 10 human epilepsy patients were studied during intraoperative electrocorticography (Ecog). Wireless Instantaneous Neurotransmitter Concentration Sensor (WINCS) based fast scan cyclic voltametry (FSCV) and fixed potential amperometry were obtained utilizing an adenosine specific triangular waveform or biosensors respectively. Results Simultaneous Ecog and electrochemistry demonstrated an average adenosine rise of 260% compared to baseline at 7.5 ą 16.9 seconds with amperometry (n=75 events) and 2.6 ą 11.2 seconds with FSCV (n=15 events) prior to electrographic seizure termination. In agreement with these animal data, adenosine elevation prior to seizure termination in a human patient utilizing FSCV was also seen. Significance Simultaneous Ecog and electrochemical recording supports the hypothesis that adenosine rises prior to seizure termination, suggesting that adenosine itself may be responsible for seizure termination. Future work using intraoperative WINCS based FSCV recording may help to elucidate the precise relationship between adenosine and seizure termination. PMID:24483230

Van Gompel, Jamie J.; Bower, Mark R.; Worrell, Gregory A.; Stead, Matt; Chang, Su-Youne; Goerss, Stephan J.; Kim, Inyong; Bennet, Kevin E.; Meyer, Fredric B.; Marsh, W. Richard; Blaha, Charles D.; Lee, Kendall H.

2014-01-01

200

Serum adenosine deaminase activity in cutaneous anthrax  

PubMed Central

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

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

201

Adenosine-induced apoptosis in EL-4 thymoma cells is caspase-independent and mediated through a non-classical adenosine receptor.  

PubMed

Cell death caused by the accumulation of extracellular adenosine is believed to contribute to the profound loss of T lymphocytes in patients with severe combined immunodeficiency disease due to adenosine deaminase deficiency. Although adenosine is known to trigger apoptosis in thymocytes and peripheral T cells, the molecular basis of this effect is not understood. In this study, we show that adenosine-induced apoptosis in mouse EL-4 thymoma cells was associated with the generation of reactive oxygen species and a reduction in mitochondrial transmembrane potential. In addition, cell death was by a caspase-independent mechanism because caspase inhibitors did not protect EL-4 cells from adenosine-induced cytotoxicity. Although reverse transcriptase polymerase chain reaction revealed that EL-4 cells expressed A2b and A3 adenosine receptor subtypes, blockade of A2b and A3 adenosine receptors with receptor-selective antagonists did not attenuate adenosine-induced cell death. Nevertheless, the failure of nucleoside transport inhibitors to prevent adenosine cytotoxicity suggested that adenosine was acting through a cell-surface receptor. In addition, adenosine-induced apoptosis was not due to an accumulation of intracellular cyclic adenosine monophosphate (cAMP) since neither forskolin nor 8-Br-cAMP was cytotoxic for EL-4 cells. Adenosine therefore acts through a non-classical receptor at the cell surface to trigger caspase-independent apoptosis in mouse thymoma cells. PMID:16168410

El-Darahali, Asile; Fawcett, Helen; Mader, Jamie S; Conrad, David M; Hoskin, David W

2005-12-01

202

9-?-L(+) Adenosine: A new naturally occurring plant growth substance elicited by triacontanol in rice  

Microsoft Academic Search

The naturally occurring plant growth substance elicited by triacontanol was found to be 9-ß-L(+) adenosine by physical and spectral methods. At picomolar concentrations, 9-ß-L(+) adenosine stimulated growth as determined by dry weight measurements of several plant species. Reaction of adenosine deaminase with adenosine from rice showed that small quantities of 9-ß-L(+) adenosine exist in plants. We believe this is the

Stanley Ries; Violet Wert; N. F. D. O'Leary; Muraleedharan Nair

1990-01-01

203

N6-FUNCTIONALIZED CONGENERS OF ADENOSINE WITH HIGH POTENCY AT A2-ADENOSINE RECEPTORS: POTENTIAL LIGANDS FOR AFFINITY CHROMATOGRAPHY  

PubMed Central

SUMMARY Adenosine analogues substituted at N6 with spacer arms designed for attachment to soluble macromolecules or to solid supports for affinity chromatography are agonists at the A2–adenosine receptor that mediates coronary vasodilation in the dog. The most active analogues had spacer arms terminating in ?NH2, ?NHCH3 or in a biotin residue. Comparisons of coronary vasoactivity with affinity" for brain A1 adenosine receptors identified one biotin–containing analogue as relatively selective for coronary A2 receptors. The complex of this analogue with avidin retained coronary vasoactivity. PMID:3013167

Jacobson, Kenneth A.; Yamada, Noboyiuki; Kirk, Kenneth L.; Daly, John W.; Olsson, R.A.

2015-01-01

204

21 CFR 864.7040 - Adenosine triphosphate release assay.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

205

21 CFR 864.7040 - Adenosine triphosphate release assay.  

Code of Federal Regulations, 2014 CFR

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

2014-04-01

206

21 CFR 864.7040 - Adenosine triphosphate release assay.  

Code of Federal Regulations, 2012 CFR

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

2012-04-01

207

Research Article Northern Ring Conformation of Methanocarba-Adenosine  

E-print Network

Enabling Technology, Genomics, Proteomics Preclinical Research Preclinical Development ToxicologyResearch Article Northern Ring Conformation of Methanocarba-Adenosine 50 -Triphosphate Required College of Pharmacy and Medicinal Resources Research Center, Wonkwang University, Chonbuk, South Korea 3

Burnstock, Geoffrey

208

21 CFR 864.7040 - Adenosine triphosphate release assay.  

Code of Federal Regulations, 2010 CFR

...a device that measures the release of adenosine triphosphate (ATP) from platelets following aggregation. This measurement...extract. Simultaneous measurements of platelet aggregation and ATP release are used to evaluate platelet function disorders....

2010-04-01

209

Animal Model for Immune Dysfunction Associated with Adenosine Deaminase Deficiency  

Microsoft Academic Search

An in vivo murine model for immunodeficiency of both B and T cells is produced by continuous intraperitoneal infusion of 2'-deoxycoformycin (DCF), a specific tightly binding inhibitor of adenosine deaminase (ADase; adenosine aminohydrolase, EC 3.5.4.4). After DCF infusion, ADase of thymus, spleen, and lymph nodes was inhibited to varying degrees ranging from 57% to 100%. Immunodeficiency under these conditions was

Antonio Tedde; M. Earl Balis; Susumu Ikehara; Rajendra Pahwa; Robert A. Good; Paul P. Trotta

1980-01-01

210

Genetic Approaches to Studying Adenosine?to?Inosine RNA Editing  

Microsoft Academic Search

Increasing proteomic diversity via the hydrolytic deamination of adenosine to inosine (A?to?I) in select mRNA templates appears crucial to the correct functioning of the nervous system in several model organisms, including Drosophila, Caenorabditis elegans, and mice. The genome of the fruitfly, Drosophila melanogaster, contains a single gene encoding the enzyme responsible for deamination, termed ADAR (for adenosine deaminase acting on

James E. C. Jepson; Robert A. Reenan

2007-01-01

211

Adenosine promotes vascular barrier function in hyperoxic lung injury  

PubMed Central

Abstract Hyperoxic lung injury is characterized by cellular damage from high oxygen concentrations that lead to an inflammatory response in the lung with cellular infiltration and pulmonary edema. Adenosine is a signaling molecule that is generated extracellularly by CD73 in response to injury. Extracellular adenosine signals through cell surface receptors and has been found to be elevated and plays a protective role in acute injury situations. In particular, ADORA2B activation is protective in acute lung injury. However, little is known about the role of adenosine signaling in hyperoxic lung injury. We hypothesized that hyperoxia?induced lung injury leads to CD73?mediated increases in extracellular adenosine, which is protective through ADORA2B signaling pathways. To test this hypothesis, we exposed C57BL6, CD73?/?, and Adora2B?/? mice to 95% oxygen or room air and examined markers of pulmonary inflammation, edema, and monitored lung histology. Hyperoxic exposure caused pulmonary inflammation and edema in association with elevations in lung adenosine levels. Loss of CD73?mediated extracellular adenosine production exacerbated pulmonary edema without affecting inflammatory cell counts. Furthermore, loss of the ADORA2B had similar results with worsening of pulmonary edema following hyperoxia exposure without affecting inflammatory cell infiltration. This loss of barrier function correlated with a decrease in occludin in pulmonary vasculature in CD73?/? and Adora2B?/? mice following hyperoxia exposure. These results demonstrate that exposure to a hyperoxic environment causes lung injury associated with an increase in adenosine concentration, and elevated adenosine levels protect vascular barrier function in hyperoxic lung injury through the ADORA2B?dependent regulation of occludin. PMID:25263205

Davies, Jonathan; Karmouty?Quintana, Harry; Le, Thuy T.; Chen, Ning?Yuan; Weng, Tingting; Luo, Fayong; Molina, Jose; Moorthy, Bhagavatula; Blackburn, Michael R.

2014-01-01

212

Glial-derived adenosine modulates spinal motor networks in mice  

PubMed Central

The activation of purinergic receptors modulates central pattern generators controlling rhythmic motor behaviors, including respiration in rodents and swimming in frog tadpoles. The present study aimed to determine whether purinergic signaling also modulates the mammalian locomotor central pattern generator. This was investigated by using isolated spinal cord preparations obtained from neonatal mice in which locomotor-related activity can be induced pharmacologically. The application of either ATP or adenosine led to a reduction in the frequency of locomotor activity recorded from ventral roots. ATP had no effect when applied in the presence of both the adenosine receptor antagonist theophylline and the ectonucleotidase inhibitor ARL67156, demonstrating that the effects of ATP application result from the breakdown of ATP to adenosine and subsequent activation of adenosine receptors. The application of theophylline or the A1-specific antagonist cyclopentyl dipropylxanthine, but not the A2A-receptor antagonist SCH58261, caused an increase in locomotor burst frequency, demonstrating that endogenously derived adenosine activates A1 receptors during locomotor network activity. Furthermore, theophylline had no effect in the presence of the ectonucleotidase inhibitor ARL67156 or the glial toxins methionine sulfoximine or ethyl fluoracetate, suggesting that endogenous adenosine is derived from ATP, which is released from glia. Finally, adenosine had no effect on slow rhythmic activity recorded upon blockade of all inhibitory transmission, suggesting that adenosine may act via the modulation of inhibitory transmission. Together, these data highlight endogenous purinergic gliotransmission, involving activation of A1 receptors, as an important intrinsic modulatory system controlling the frequency of activity generated by spinal locomotor circuitry in mammals. PMID:22205649

Witts, Emily C.; Panetta, Kara M.

2012-01-01

213

Glial-derived adenosine modulates spinal motor networks in mice.  

PubMed

The activation of purinergic receptors modulates central pattern generators controlling rhythmic motor behaviors, including respiration in rodents and swimming in frog tadpoles. The present study aimed to determine whether purinergic signaling also modulates the mammalian locomotor central pattern generator. This was investigated by using isolated spinal cord preparations obtained from neonatal mice in which locomotor-related activity can be induced pharmacologically. The application of either ATP or adenosine led to a reduction in the frequency of locomotor activity recorded from ventral roots. ATP had no effect when applied in the presence of both the adenosine receptor antagonist theophylline and the ectonucleotidase inhibitor ARL67156, demonstrating that the effects of ATP application result from the breakdown of ATP to adenosine and subsequent activation of adenosine receptors. The application of theophylline or the A(1)-specific antagonist cyclopentyl dipropylxanthine, but not the A(2A)-receptor antagonist SCH58261, caused an increase in locomotor burst frequency, demonstrating that endogenously derived adenosine activates A(1) receptors during locomotor network activity. Furthermore, theophylline had no effect in the presence of the ectonucleotidase inhibitor ARL67156 or the glial toxins methionine sulfoximine or ethyl fluoracetate, suggesting that endogenous adenosine is derived from ATP, which is released from glia. Finally, adenosine had no effect on slow rhythmic activity recorded upon blockade of all inhibitory transmission, suggesting that adenosine may act via the modulation of inhibitory transmission. Together, these data highlight endogenous purinergic gliotransmission, involving activation of A(1) receptors, as an important intrinsic modulatory system controlling the frequency of activity generated by spinal locomotor circuitry in mammals. PMID:22205649

Witts, Emily C; Panetta, Kara M; Miles, Gareth B

2012-04-01

214

Adenosine Protects Against Indomethacin-Induced Gastric Damage in Rats  

Microsoft Academic Search

This study examines the putativegastroprotective effect of adenosine onindomethacininduced gastric lesions and the possiblemechanisms involved. After 24 hr of starvation, the ratswere treated either with indomethacin (Indo; 25 mg\\/kg,subcutaneously) alone or adenosine + Indo (Ado; 7.5mg\\/kg, subcutaneously, three times a day), or thevehicle (5% NaHCO3, subcutaneously). Thelength of hemorrhagic lesions in the stomachs was expressed as the lesionindex. The tissue-associated

Ayhan Bozkurt; Meral Yuksel; Goncagul Haklar; Hizir Kurtel; Berrak C. Yegen; Inci Alican

1998-01-01

215

The role of receptor structure in determining adenosine receptor activity  

Microsoft Academic Search

Adenosine produces a wide variety of physiological effects through the activation of cell surface adenosine receptors (ARs). ARs are members of the G-protein-coupled receptor family, and currently, four subtypes, the A1AR, A2AAR, A2BAR, and A3AR, are recognized. This review focuses on the role of receptor structure in governing various facets of AR activity. Ligand-binding properties of ARs are primarily dictated

Mark E Olah; Gary L Stiles

2000-01-01

216

Delayed treatment with an adenosine kinase inhibitor, GP683, attenuates infarct size in rats with temporary middle cerebral artery occlusion  

Microsoft Academic Search

BACKGROUND AND PURPOSE: Brain ischemia is associated with a marked increase in extracellular adenosine levels. This results in activation of cell surface adenosine receptors and some degree of neuroprotection. Adenosine kinase is a key enzyme controlling adenosine metabolism. Inhibition of this enzyme enhances the levels of endogenous brain adenosine already elevated as a result of the ischemic episode. We studied

Turgut Tatlisumak; Kentaro Takano; Richard A. D. Carano; Leonard P. Miller; Alan C. Foster; Marc Fisher

1998-01-01

217

Shift of adenosine kinase expression from neurons to astrocytes during postnatal development suggests dual functionality of the enzyme  

Microsoft Academic Search

Adenosine is a potent modulator of excitatory neurotransmission, especially in seizure-prone regions such as the hippocampal formation. In adult brain ambient levels of adenosine are controlled by adenosine kinase (ADK), the major adenosine-metabolizing enzyme, expressed most strongly in astrocytes. Since ontogeny of the adenosine system is largely unknown, we investigated ADK expression and cellular localization during postnatal development of the

F. E. Studer; D. E. Fedele; A. Marowsky; C. Schwerdel; K. Wernli; K. Vogt; J. M. Fritschy; D. Boison

2006-01-01

218

Genetic and biochemical consequences of adenosine deaminase deficiency in humans.  

PubMed

Adenosine deaminase deficiency accounts for approximately 15-20% of severe combined immunodeficiency in humans. The gene for adenosine deaminase is located on chromosome 20q12-q13.11 and codes for an aminohydrolase that catalyzes the deamination of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. Absence of the enzyme causes a build-up of the substrates in addition to excess deoxyadenosine triphosphate, thereby compromising the regenerative capacity of the immune system. Due to underlying allelic heterogeneity, the disorder manifests as a spectrum, ranging from neonatal onset severe combined immunodeficiency to apparently normal partial adenosine deaminase deficiency. Tandem mass spectrometry coupled with high efficiency separation systems enables postnatal diagnosis of the disorder, while prenatal diagnosis relies on assaying enzyme activity in cultured amniotic fibroblasts or chorionic villi sampling. Screening of adenosine deaminase deficiency for relatives-at-risk may reduce costs of treatment and ensure timely medical intervention as applicable. This article reviews the genetic, biochemical and clinical aspects of adenosine deaminase deficiency. PMID:24772956

Bose, Rahul; Nandagopal, Krishnadas

2013-10-01

219

Adenosine metabolism in kidney slices under normoxic conditions.  

PubMed

The effect of adenosine in rat kidney under normoxic conditions has been studied. It is demonstrated that adenosine modulates cell nucleotide levels. HPLC analysis of the purine compounds inside the cell indicates that adenosine improves the ATP/ADP ratio, whereas it diminishes the adenine content. This behaviour is not due to mediation by specific receptors, as agonists at P1 purinoceptors did not have any effect. Further evidence using inosine as well as dipyridamole and deoxycoformycin indicates that all effects are dependent on the previous uptake of adenosine. The origin of free adenine in the kidney has been investigated, and it appears to come from the phosphorolysis of 5'-methylthio-adenosine. This report is the first to describe the activity of methylthioadenosine phosphorylase (E.C. 2.4.2.28) in the kidney. It is concluded that 1) extracellular adenosine improves guinea pig renal function by increasing the ATP level and the ATP/ADP ratio; and 2) there exists a functional pathway in the kidney that produces adenine and AMP coming from methionine and ATP. This latter pathway probably produces spermine and spermidine, which are likely to be important for renal function. PMID:2332456

Blanco, J; Mallol, J; Lluis, C; Canela, E I; Franco, R

1990-05-01

220

Adenosine dysfunction in astrogliosis: cause for seizure generation?  

PubMed

Epilepsy is characterized by both neuronal and astroglial dysfunction. The endogenous anticonvulsant adenosine, the level of which is largely controlled by astrocytes, might provide a crucial link between astrocyte and neuron dysfunction in epilepsy. Here we have studied astrogliosis, a hallmark of the epileptic brain, adenosine dysfunction and the emergence of spontaneous seizures in a comprehensive approach that includes a new mouse model of focal epileptogenesis, mutant mice with altered brain levels of adenosine, and mice lacking adenosine A1 receptors. In wild-type mice, following a focal epileptogenesis-precipitating injury, astrogliosis, upregulation of the adenosine-removing astrocytic enzyme adenosine kinase (ADK), and spontaneous seizures coincide in a spatio-temporally restricted manner. Importantly, these spontaneous seizures are mimicked by untreated transgenic mice that either overexpress ADK in brain or lack A1 receptors. Conversely, mice with reduced ADK in the forebrain do not develop either astrogliosis or spontaneous seizures. Our studies define ADK as a crucial upstream regulator of A1 receptor-mediated modulation of neuronal excitability, and support the ADK hypothesis of epileptogenesis in which upregulation of ADK during astrogliosis provides a crucial link between astrocyte and neuron dysfunction in epilepsy. These findings define ADK as rational target for therapeutic intervention. PMID:18634566

Li, Tianfu; Quan Lan, Jing; Fredholm, Bertil B; Simon, Roger P; Boison, Detlev

2007-11-01

221

Modulation of sensory irritation responsiveness by adenosine and malodorants.  

PubMed

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

Willis, Daniel N; Morris, John B

2013-01-01

222

Attenuation of ischemia-induced extracellular adenosine accumulation by homocysteine.  

PubMed

The purpose of this study was to determine the effects of homocysteine, which consumes intracellular adenosine via formation of S-adenosylhomocysteine, on interstitial fluid (ISF) adenosine and cerebral blood flow (CBF) before, during, and after cerebral ischemia. Microdialysis probes, used to measure local CBF (H2 clearance) and to sample ISF, were implanted bilaterally into the caudate nucleus of halothane-anesthetized rats (n = 8). L-Homocysteine thiolactone was administered locally via one of the probes. Animals were exposed to 20 min of ischemia, induced by bilateral carotid occlusion plus hemorrhage to an arterial blood pressure of 50 mm Hg, followed by 60 min of reperfusion. Before ischemia, CBF and dialysate adenosine were decreased with homocysteine. During ischemia and early reperfusion, dialysate purine metabolites increased on both sides of the brain; however, the ischemia-induced increase in adenosine was attenuated on the side of local homocysteine. CBF was lower on the side of homocysteine throughout reperfusion. These data demonstrate that homocysteine (a) decreases basal ISF adenosine and CBF, (b) attenuates the increase in dialysate adenosine during ischemia, and (c) reduces hyperemia during early reperfusion. PMID:8436612

Sciotti, V M; Van Wylen, D G

1993-03-01

223

Seizure suppression and lack of adenosine A 1 receptor desensitization after focal long-term delivery of adenosine by encapsulated myoblasts  

Microsoft Academic Search

Adenosine is an important inhibitory modulator of brain activity. In a previous ex vivo gene therapy approach, local release of adenosine by encapsulated fibroblasts implanted into the vicinity of an epileptic focus, was sufficient to provide transient protection from seizures (Huber, A., Padrun, V., Deglon, N., Aebischer, P., Mohler, H., Boison, D., 2001. Grafts of adenosine-releasing cells suppress seizures in

Martin Güttinger; Vivianne Padrun; William F. Pralong; Detlev Boison

2005-01-01

224

Intracellular ATP Concentration Contributes to the Cytotoxic and Cytoprotective Effects of Adenosine  

PubMed Central

Extracellular adenosine (Ade) interacts with cells by two pathways: by activating cell surface receptors at nanomolar/micromolar concentrations; and by interfering with the homeostasis of the intracellular nucleotide pool at millimolar concentrations. Ade shows both cytotoxic and cytoprotective effects; however, the underlying mechanisms remain unclear. In the present study, the effects of adenosine-mediated ATP on cell viability were investigated. Adenosine treatment was found to be cytoprotective in the low intracellular ATP state, but cytotoxic under the normal ATP state. Adenosine-mediated cytotoxicity and cytoprotection rely on adenosine-derived ATP formation, but not via the adenosine receptor pathway. Ade enhanced proteasome inhibition-induced cell death mediated by ATP generation. These data provide a new pathway by which adenosine exerts dual biological effects on cell viability, suggesting an important role for adenosine as an ATP precursor besides the adenosine receptor pathway. PMID:24098558

Guo, Haiping; Liu, Shouting; Huang, Hongbiao; Liu, Ningning; Yang, Changshan; Tang, Ping; Liu, Jinbao

2013-01-01

225

Peripheral antinociceptive effect of an adenosine kinase inhibitor, with augmentation by an adenosine deaminase inhibitor, in the rat formalin test  

Microsoft Academic Search

This study examined the ability of an adenosine kinase inhibitor (5?-amino-5?-deoxyadenosine; NH2dAD), an adenosine deaminase inhibitor (2?-deoxycoformycin), and combinations of these agents to produce a peripheral modulation of the pain signal in the low concentration formalin model. Drugs were administered in combination with 0.5% formalin, or into the contralateral hindpaw to test for systemic effects, and episodes of flinching behaviors

Jana Sawynok; Allison Reid; Anthony Poon

1998-01-01

226

Hot spot mutations in adenosine deaminase deficiency  

SciTech Connect

The authors have previously characterized mutant adenosine deaminase enzymes in seven children with partial ADA deficiency. Six children shared common origins, suggesting a common progenitor. However, they found evidence for multiple phenotypically different mutant enzymes. They hypothesized that many of the mutations would be at CpG dinucleotides, hot spots at which spontaneous deamination of 5-methylcytosine results in C to T or G to A transitions. Digestion of DNA from these children with Msp I and Taq I, enzymes recognizing CpG dinucleotides, identified three different mutations, each correlating with expression of a different mutant enzyme. Sequencing of cDNA clones and genomic DNA amplified by polymerase chain reaction confirmed the presence of C to T or G to A transitions at CpG dinucleotides. To determine the true frequency of hot spot mutation in these children, consecutively ascertained through a newborn screening program, they sequenced cDNA from the remaining alleles. Two others were hot spot mutations each again resulting in expression of a phenotypically different mutant enzyme. These seven mutations account for all 14 chromosomes in these children. There is thus a very high frequency of hot spot mutations in partial ADA deficiency. They were able to correlate genotype and phenotype and to dissect the activity of individual mutant alleles.

Hirschhorn, R.; Tzall, S.; Ellenbogen, A. (New York Univ. Medical School, NY (USA))

1990-08-01

227

Auto-anti-idiotypic approach to adenosine receptors  

SciTech Connect

If an antibody (Abl) binds to and recognizes the same epitopes on a ligand that are recognized by a receptor, then among anti-idiotypic antibodies (Ab2) to Ab1, there may be some that have combining sites that mimic the ligand (internal image). In the case of the acetylcholine receptor and the glucocorticoid receptor these Ab2 antibodies could be raised through a naturally occurring idiotypic network by immunizing mice with the ligands of the receptors. To test the generality of this procedure and to raise antibodies to adenosine receptors, BALB/c mice were immunized with adenosine 6-aminocaproyl-BSA. Hyberidoma cell lines were raised. Cell lines which secreted antibodies that bound to rabbit anti-adenosine antibody were obtained. Two such mAbs, AA18 and AA21, inhibited the binding of (/sup 3/H)adenosine to rabbit anti-adenosine antibody. Furthermore, they bound to rat cerebral cortical membrane and binding could be inhibited by L-phenylisopropyladenosine (L-PIA), an adenosine receptor agonist. Rat cerebral membrane proteins were solubilized with 1% cholic acid, and analyzed by SDS-PAGE and Western blotting. Both AA18 and AA21 recognized a 62 kD band under non-reducing conditions, and 52 kD and 36 kD bands under reducing conditions. The 36 kD band is consistent with the A1 adenosine receptor binding subunit reported by Stiles, et al. The authors results extend the utility of the autoimmune approach for raising antibody to receptors without the necessity of using isolated receptor as immunogen.

Ku, H.H.; Erlanger, B.F.

1986-03-01

228

Adenosine deaminase from Streptomyces coelicolor: recombinant expression, purification and characterization.  

PubMed

The sequencing of the genome of Streptomyces coelicolor A3(2) identified seven putative adenine/adenosine deaminases and adenosine deaminase-like proteins, none of which have been biochemically characterized. This report describes recombinant expression, purification and characterization of SCO4901 which had been annotated in data bases as a putative adenosine deaminase. The purified putative adenosine deaminase gives a subunit Mr=48,400 on denaturing gel electrophoresis and an oligomer molecular weight of approximately 182,000 by comparative gel filtration. These values are consistent with the active enzyme being composed of four subunits with identical molecular weights. The turnover rate of adenosine is 11.5 s?š at 30 °C. Since adenine is deaminated ?10ł slower by the enzyme when compared to that of adenosine, these data strongly show that the purified enzyme is an adenosine deaminase (ADA) and not an adenine deaminase (ADE). Other adenine nucleosides/nucleotides, including 9-?-D-arabinofuranosyl-adenine (ara-A), 5'-AMP, 5'-ADP and 5'-ATP, are not substrates for the enzyme. Coformycin and 2'-deoxycoformycin are potent competitive inhibitors of the enzyme with inhibition constants of 0.25 and 3.4 nM, respectively. Amino acid sequence alignment of ScADA with ADAs from other organisms reveals that eight of the nine highly conserved catalytic site residues in other ADAs are also conserved in ScADA. The only non-conserved residue is Asn317, which replaces Asp296 in the murine enzyme. Based on these data, it is suggested here that ADA and ADE proteins are divergently related enzymes that have evolved from a common ?/? barrel scaffold to catalyze the deamination of different substrates, using a similar catalytic mechanism. PMID:21511036

Pornbanlualap, Somchai; Chalopagorn, Pornchanok

2011-08-01

229

Tween 20-stabilized gold nanoparticles combined with adenosine triphosphate-BODIPY conjugates for the fluorescence detection of adenosine with more than 1000-fold selectivity.  

PubMed

This study describes the development of a simple, enzyme-free, label-free, sensitive, and selective system for detecting adenosine based on the use of Tween 20-stabilized gold nanoparticles (Tween 20-AuNPs) as an efficient fluorescence quencher for boron dipyrromethene-conjugated adenosine 5'-triphosphate (BODIPY-ATP) and as a recognition element for adenosine. BODIPY-ATP can interact with Tween 20-AuNPs through the coordination between the adenine group of BODIPY-ATP and Au atoms on the NP surface, thereby causing the fluorescence quenching of BODIPY-ATP through the nanometal surface energy transfer (NSET) effect. When adenosine attaches to the NP surface, the attached adenosine exhibits additional electrostatic attraction to BODIPY-ATP. As a result, the presence of adenosine enhances the efficiency of AuNPs in fluorescence quenching of BODIPY-ATP. The AuNP-induced fluorescence quenching of BODIPY-ATP progressively increased with an increase in the concentration of adenosine; the detection limit at a signal-to-noise ratio of 3 for adenosine was determined to be 60nM. The selectivity of the proposed system was more than 1000-fold for adenosine over any adenosine analogs and other nucleotides. The proposed system combined with a phenylboronic acid-containing column was successfully applied to the determination of adenosine in urine. PMID:25604821

Hung, Szu-Ying; Shih, Ya-Chen; Tseng, Wei-Lung

2015-02-01

230

Mechanism of adenylate kinase. Dose adenosine 5'-triphosphate bind to the adenosine 5'-monophosphate site  

SciTech Connect

Although the subtrate binding properties of adenylate kinase (AK) have been studied extensively by various biochemical and biophysical techniques, it remains controversial whether uncomplexed adenosine 5'-triphosphate (ATP) binds to the adenosine 5'-monophosphate (AMP) site of AK. The authors present two sets of experiments which argue against binding of ATP to the AMP site. (a) /sup 31/P nuclear magnetic resonance titration of ATP with AK indicated a 1:1 stoichiometry on the basis of changes in coupling constants and line widths. This ruled out binding of ATP to both sites. (b) ATP and MgATP were found to behave similarly by protecting AK from spontaneous inactivation while AMP showed only a small degree of protection. Such inactivation could also be protected or reversed by dithioerythritol and is most likely due to oxidation of sulfhydryl groups, one of which (cysteine-25) is located near the MgATP site. The results support binding of ATP to the MgATP site predominantly, instead of the AMP site, in the absence of Mg/sup 2 +/.

Shyy, Y.J.; Tian, G.; Tsai, M.D.

1987-10-06

231

Engineered adenosine-releasing cells for epilepsy therapy: Human mesenchymal stem cells and human embryonic stem cells  

Microsoft Academic Search

Summary  Adenosine is a modulator of neuronal activity with anticonvulsant and neuroprotective properties. Conversely, focal deficiency\\u000a in adenosine contributes to ictogenesis. Thus, focal reconstitution of adenosine within an epileptogenic brain region constitutes\\u000a a rational therapeutic approach, whereas systemic augmentation of adenosine is precluded by side effects. To meet the therapeutic\\u000a goal of focal adenosine augmentation, genetic disruption of the adenosine metabolizing

Detlev Boison

2009-01-01

232

Intracoronary Versus Intravenous Adenosine-Induced Maximal Coronary Hyperemia for Fractional Flow Reserve Measurements  

PubMed Central

BACKGROUND Maximal hyperemia is the critical prerequisite for fractional flow reserve (FFR) assessment. Despite intravenous (IV) adenosine currently being the recommended approach, intracoronary (IC) administration of adenosine constitutes a valuable alternative in everyday practice. However, it is surprisingly unclear which IC strategy allows the achievement of FFR values that are comparable to IV adenosine. OBJECTIVES This study sought to compare increasing doses of IC adenosine versus IV adenosine for FFR. METHODS 30 intermediate coronary stenoses undergoing FFR measurement were prospectively and consecutively enrolled. Hyperemia was sequentially induced by bolus of IC adenosine (ADN; 150 ?g) followed by IV adenosine (IVADN) infusion over 3 minutes at dose of (140 ?g/kg/min). FFR values, symptoms, and development of atrioventricular block were recorded. RESULTS 150 ?g doses of IC adenosine were well tolerated and associated with fewer symptoms than IV adenosine. Intracoronary adenosine doses induced a significant decrease of FFR compared with baseline levels (P < 0.01). Among the 6 patients with FFR values less than 0.80 identified by IVADN, 4 were correctly identified also by 150 ?g bolus IC adenosine. Larger randomized studies with cross-over design are necessary to verify the results. CONCLUSIONS This small pilot study suggests that IC adenosine might be an alternative to IV adenosine. Larger randomized studies with a cross-over design are necessary. PMID:24558302

Khashaba, Ahmed; Mortada, Ayman; Omran, Azza

2014-01-01

233

A1 receptors self-regulate adenosine release in the striatum: evidence of autoreceptor characteristics  

PubMed Central

Adenosine A1 receptors are inhibitory G-protein coupled receptors that presynaptically regulate neurotransmitter release, but their role in self-regulating adenosine release is not known. In this study, we examined the modulation of evoked adenosine and dopamine efflux by A1 receptors and studied whether D1 receptors mediate these effects. Fast-scan cyclic voltammetry at carbon-fiber microelectrodes was used for the simultaneous detection of adenosine and dopamine efflux on a subsecond time scale. Short electrical stimulation trains delivered to the substantia nigra (60 pulses, 60 Hz) were used to evoke dopamine and adenosine release in the striatum. The adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA, 1 mg/kg i.p.) decreased both adenosine and dopamine efflux, although the effect for adenosine occurred more quickly than for dopamine. The A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 6 mg/kg i.p.) increased stimulated adenosine release. The effects of CPA were partially attenuated by the dopamine D1 receptor antagonist SCH-23390. Thus, A1 and D1 receptors have a synergistic interaction that modulates both stimulated adenosine and dopamine. The decrease in adenosine is not a downstream effect of lowered dopamine release, as decreasing dopamine synthesis and release with ?-methyl-p-tyrosine or increasing release with haloperidol had no effect on adenosine release. This study shows that A1 receptors have some characteristics of an autoreceptor, including self-regulation of adenosine release. PMID:20933584

Cechova, Sylvia; Elsobky, Angela M.; Venton, B. Jill

2010-01-01

234

Adenosine hypothesis of schizophrenia--opportunities for pharmacotherapy.  

PubMed

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 reversing 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 dysfunctions characteristic 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 (A(1)R and A(2A)R), and the regulatory enzyme adenosine kinase (ADK). Key preliminary clinical data and preclinical findings are reviewed. PMID:21315743

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

2012-03-01

235

Manipulation of adenosine kinase affects sleep regulation in mice.  

PubMed

Sleep and sleep intensity are enhanced by adenosine and its receptor agonists, whereas adenosine receptor antagonists induce wakefulness. Adenosine kinase (ADK) is the primary enzyme metabolizing adenosine in adult brain. To investigate whether adenosine metabolism or clearance affects sleep, we recorded sleep in mice with engineered mutations in Adk. Adk-tg mice overexpress a transgene encoding the cytoplasmic isoform of ADK in the brain but lack the nuclear isoform of the enzyme. Wild-type mice and Adk(+/-) mice that have a 50% reduction of the cytoplasmic and the nuclear isoforms of ADK served as controls. Adk-tg mice showed a remarkable reduction of EEG power in low frequencies in all vigilance states and in theta activity (6.25-11 Hz) in rapid eye movement (REM) sleep and waking. Adk-tg mice were awake 58 min more per day than wild-type mice and spent significantly less time in REM sleep (102 ą 3 vs 128 ą 3 min in wild type). After sleep deprivation, slow-wave activity (0.75-4 Hz), the intensity component of non-rapid eye movement sleep, increased significantly less in Adk-tg mice and their slow-wave energy was reduced. In contrast, the vigilance states and EEG spectra of Adk(+/-) and wild-type mice did not differ. Our data suggest that overexpression of the cytoplasmic isoform of ADK is sufficient to alter sleep physiology. ADK might orchestrate neurotransmitter pathways involved in the generation of EEG oscillations and regulation of sleep. PMID:20881134

Palchykova, Svitlana; Winsky-Sommerer, Raphaelle; Shen, Hai-Ying; Boison, Detlev; Gerling, Andrea; Tobler, Irene

2010-09-29

236

Investigating real-time activation of adenosine receptors by bioluminescence resonance energy transfer technique  

NASA Astrophysics Data System (ADS)

Adenosine receptors play important roles in many physiological and pathological processes, for example regulating myocardial oxygen consumption and the release of neurotransmitters. The activations of adenosine receptors have been studied by some kinds of techniques, such as western blot, immunohistochemistry, etc. However, these techniques cannot reveal the dynamical response of adenosine receptors under stimulation. In this paper, bioluminescence resonance energy transfer technique was introduced to study the real-time activation of adenosine receptors by monitoring the dynamics of cyclic adenosine monophosphate (cAMP) level. The results showed that there were significant differences between adenosine receptors on real-time responses under stimulation. Moreover, the dynamics of cAMP level demonstrated that competition between adenosine receptors existed. Taken together, our study indicates that monitoring the dynamics of cAMP level using bioluminescence resonance energy transfer technique could be one potential approach to investigate the mechanism of competitions between adenosine receptors.

Huang, Yimei; Yang, Hongqin; Zheng, Liqin; Chen, Jiangxu; Wang, Yuhua; Li, Hui; Xie, Shusen

2013-02-01

237

Crithidia fasciculata adenosine transporter 1 (CfAT1), a novel high-affinity equilibrative nucleoside transporter specific for adenosine.  

PubMed

Most eukaryotic organisms including protozoans like Crithidia, Leishmania, and Plasmodium encode a repertoire of equilibrative nucleoside transporters (ENTs). Using genomic sequencing data from Crithidia fasciculata, we discovered that this organism contains multiple ENT genes of highly similar sequence to the previously cloned and characterized adenosine transporter CfNT1: CfAT1 and CfNT3, and an allele of CfAT1, named CfAT1.2. Characterization of CfAT1 shows that it is an adenosine-only transporter, 87% identical to CfNT1 in protein sequence, with a 50-fold lower Km for adenosine. Site directed mutation of a key residue in transmembrane domain 4 (TM4) in both CfNT1 and CfAT1 shows that lysine at this position results in a high affinity phenotype, while threonine decreases adenosine affinity in both transporters. These results show that C. fasciculata has at least two adenosine transporters, and that as in other protozoan ENTs, a lysine residue in TM4 plays a key role in ligand affinity. PMID:24120444

Arendt, Cassandra S

2013-10-01

238

Delayed onset adenosine deaminase deficiency associated with acute disseminated encephalomyelitis.  

PubMed

Acute disseminated encephalomyelitis (ADEM) is a monophasic, immune-mediated demyelinating disorder that can appear after either immunizations or, more often, infections. Magnetic resonance imaging of patients shows inflammatory lesions in the brain and spinal cord. An immune-mediated mechanism may play a role in this disease, although its precise pathogenesis remains unclear. In this study, a 2-year-old boy presented with ADEM, and he showed improvement on treatment with high-dose intravenous corticosteroids. At the age of 3 years, the presence of recurrent bronchitis, bronchiectasia, and lymphopenia suggested that the patient was suffering from combined immunodeficiency. The patient was finally diagnosed with delayed onset adenosine deaminase deficiency. Delayed onset adenosine deaminase deficiency is frequently associated with autoimmune diseases, including thyroiditis and cytopenia, both of which were observed in the patient. The ADEM in this patient may be a presentation of delayed onset adenosine deaminase deficiency. PMID:22447032

Nakaoka, Hideyuki; Kanegane, Hirokazu; Taneichi, Hiromichi; Miya, Kazushi; Yang, Xi; Nomura, Keiko; Takezaki, Shunichiro; Yamada, Masafumi; Ohara, Osamu; Kamae, Chikako; Imai, Kohsuke; Nonoyama, Shigeaki; Wada, Taizo; Yachie, Akihiro; Hershfield, Michael S; Ariga, Tadashi; Miyawaki, Toshio

2012-06-01

239

[Adenosine deaminase as costimulatory molecule and marker of cellular immunity].  

PubMed

Adenosine deaminase (ADA) is an enzyme of purine metabolism which has been the subject of much interest because the congenital defect of this enzyme causes severe combined immunodeficiency syndrome. One of the three isoforms of the enzyme (ecto-ADA) is capable of binding to the glycoprotein CD26 and adenosine receptors A1 and A2B. ADA-CD26 interaction produces a costimulatory signal in the events of T cell activation and secretion of IFN-gamma, TNF-alpha and IL-6. During this activation, the enzyme activity is regulated positively by IL-2 and IL-12 and negatively by IL-4, based on the mechanism of translocation. Diverse studies suggest that seric and plasmatic levels of ADA rise in some diseases caused by microorganisms infecting mainly the macrophages and in hypertensive disorders, which may represent a compensatory mechanism resulting from increased adenosine levels and the release of hormones and inflammatory mediators estimulated by hipoxia. PMID:21365880

Pérez-Aguilar, Mary Carmen; Goncalves, Loredana; Ibarra, Alba; Bonfante-Cabarcas, Rafael

2010-12-01

240

Release of Adenosine and ATP During Ischemia and Epilepsy  

PubMed Central

Eighty years ago Drury & Szent-Györgyi described the actions of adenosine, AMP (adenylic acid) and ATP (pyrophosphoric or diphosphoric ester of adenylic acid) on the mammalian cardiovascular system, skeletal muscle, intestinal and urinary systems. Since then considerable insight has been gleaned on the means by which these compounds act, not least of which in the distinction between the two broad classes of their respective receptors, with their many subtypes, and the ensuing diversity in cellular consequences their activation invokes. These myriad actions are of course predicated on the release of the purines into the extracellular milieu, but, surprisingly, there is still considerable ambiguity as to how this occurs in various physiological and pathophysiological conditions. In this review we summarise the release of ATP and adenosine during seizures and cerebral ischemia and discuss mechanisms by which the purines adenosine and ATP may be released from cells in the CNS under these conditions. PMID:20190959

Dale, Nicholas; Frenguelli, Bruno G

2009-01-01

241

Feasibility of low-level treadmill exercise during adenosine stress in an outpatient office laboratory  

Microsoft Academic Search

Background: In patients referred for adenosine stress myocardial perfusion imaging, low-level treadmill exercise (LLTE) has been shown to reduce adenosine-related side effects and improve image quality. However, the feasibility of using LLTE during adenosine stress has not been well defined.Methods: We retrospectively reviewed the records of all patients referred to our outpatient office laboratory for adenosine stress myocardial perfusion imaging

D. A Calnon; K. S Grewal; P. B George; D. R Richards

2004-01-01

242

Edinburgh Research Explorer Adenosine receptor expression and function in rat striatal  

E-print Network

.95+0.05 in control), as did adenosine deaminase (S2/S1 ratio 0.69+0.05), whereas the A1 receptor antagonist DPCPX (100 nM) had no eect (S2/S1 1.05+0.14). 4 In the presence of adenosine deaminase the adenosine A2AEdinburgh Research Explorer Adenosine receptor expression and function in rat striatal cholinergic

MacDonald, Andrew

243

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

Microsoft Academic Search

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

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

1983-01-01

244

Adenosine kinase inhibition protects brain against transient focal ischemia in rats  

Microsoft Academic Search

Endogenous adenosine released locally during cerebral ischemia is neuroprotective, and agents which decrease adenosine inactivation may potentiate its protective effects. The effects of 5?-deoxy-5-iodotubercidin (5?d-5IT), an inhibitor of the adenosine-catabolizing enzyme, adenosine kinase, were studied in male Wistar rats subjected to 2 h of transient middle cerebral artery occlusion. 5?d-5IT or the vehicle (10% DMSO in saline) was administered i.p.

Ning Jiang; Elizabeth A Kowaluk; Chi-Hung Lee; Hormoz Mazdiyasni; Michael Chopp

1997-01-01

245

Cloning of Human Adenosine Kinase cDNA: Sequence Similarity to Microbial Ribokinases and Fructokinases  

Microsoft Academic Search

Adenosine kinase catalyzes the phosphorylation of adenosine to AMP and hence is a potentially important regulator of extracellular adenosine concentrations. Despite extensive characterization of the kinetic properties of the enzyme, its primary structure has never been elucidated. Full-length cDNA clones encoding catalytically active adenosine kinase were obtained from lymphocyte, placental, and liver cDNA libraries. Corresponding mRNA species of 1.3 and

Jozef Spychala; Nabanita S. Datta; Kenji Takabayashi; Milton Datta; Irving H. Fox; Thomas Gribbin; Beverly S. Mitchell

1996-01-01

246

Conformational Changes That Occur during an RNA-editing Adenosine Deamination Reaction*  

E-print Network

the Department of Chemistry, University of Utah, Salt Lake City, Utah 84112 ADARs are adenosine deaminases deamina- tion sites in other RNA sequences have also been identified (4, 5). ADAR2 (adenosine deaminaseConformational Changes That Occur during an RNA-editing Adenosine Deamination Reaction* Received

Beal, Peter A.

247

Demethylation of 6-O-Methylinosine by an RNA-Editing Adenosine Deaminase  

E-print Network

Demethylation of 6-O-Methylinosine by an RNA-Editing Adenosine Deaminase LaHoma M. Easterwood Lake City, Utah 84112 ReceiVed August 25, 2000 ADARs are adenosine deaminases that act on RNA-modifying enzyme adenosine deaminase (ADA).5-8 These experiments illustrate significant mechanistic similarities

Beal, Peter A.

248

Substrate Analogues for an RNA-Editing Adenosine Deaminase: Mechanistic Investigation and Inhibitor Design  

E-print Network

Substrate Analogues for an RNA-Editing Adenosine Deaminase: Mechanistic Investigation and Inhibitor@chem.utah.edu Abstract: ADARs are adenosine deaminases that act on RNA and are responsible for RNA-editing reactions,6-Diaminopurine ribonucleoside in RNA is not a substrate for ADAR, in contrast to adenosine deaminase (ADA), which

Beal, Peter A.

249

Adenosine deaminase-related growth factors stimulate cell proliferation in Drosophila  

E-print Network

Adenosine deaminase-related growth factors stimulate cell proliferation in Drosophila by depleting-A and ADGF-D are active adenosine deaminases (ADAs), and they cause polarization and serum: the imaginal disk growth factors (IDGFs) (4), which are related to chitinases, and the adenosine deaminase

Â?urovec, Michal

250

Downregulation of hippocampal adenosine kinase after focal ischemia as potential endogenous neuroprotective mechanism  

Microsoft Academic Search

The rate of ischemic brain injury varies with the brain region, requiring only hours in striatum but days in hippocampus. Such maturation implies the existence of endogenous neuroprotective mechanisms. Adenosine is an endogenous neuroprotectant regulated by adenosine kinase (ADK). To investigate, whether adenosine might play a role in protecting the hippocampus after focal ischemia, we subjected transgenic mice, which overexpress

Giuseppe Pignataro; Samaneh Maysami; Francesca E Studer; Andrew Wilz; Roger P Simon; Detlev Boison

2008-01-01

251

Comparative Transcriptome Analysis of Bacillus subtilis Responding to Dissolved Oxygen in Adenosine Fermentation  

Microsoft Academic Search

Dissolved oxygen (DO) is an important factor for adenosine fermentation. Our previous experiments have shown that low oxygen supply in the growth period was optimal for high adenosine yield. Herein, to better understand the link between oxygen supply and adenosine productivity in B. subtilis (ATCC21616), we sought to systematically explore the effect of DO on genetic regulation and metabolism through

Wen-Bang Yu; Shu-Hong Gao; Chun-Yun Yin; Ying Zhou; Bang-Ce Ye

2011-01-01

252

Temporal and mechanistic dissociation of ATP and adenosine release during ischaemia in the mammalian hippocampus1  

PubMed Central

Abstract Adenosine is well known to be released during cerebral metabolic stress and is believed to be neuroprotective. ATP release under similar circumstances has been much less studied. We have now used biosensors to measure and compare in real time the release of ATP and adenosine during in vitro ischaemia in hippocampal slices. ATP release only occurred following the anoxic depolarisation, whereas adenosine release was apparent almost immediately after the onset of ischaemia. ATP release required extracellular Ca2+. By contrast adenosine release was enhanced by removal of extracellular Ca2+, whilst TTX had no effect on either ATP release or adenosine release. Blockade of ionotropic glutamate receptors substantially enhanced ATP release, but had only a modest effect on adenosine release. Carbenoxolone, an inhibitor of gap junction hemichannels, also greatly enhanced ischaemic ATP release, but had little effect on adenosine release. The ecto-ATPase inhibitor ARL 67156, whilst modestly enhancing the ATP signal detected during ischaemia, had no effect on adenosine release. Adenosine release during ischaemia was reduced by pre-treament with homosysteine thiolactone suggesting an intracellular origin. Adenosine transport inhibitors did not inhibit adenosine release, but instead they caused a twofold increase of release. Our data suggest that ATP and adenosine release during ischaemia are for the most part independent processes with distinct underlying mechanisms. These two purines will consequently confer temporally distinct influences on neuronal and glial function in the ischaemic brain. PMID:17459147

Frenguelli, Bruno G; Wigmore, Geoffrey; Llaudet, Enrique; Dale, Nicholas

2007-01-01

253

Acceleration of ventricular response to atrial flutter after intravenous adenosine.  

PubMed

Adenosine may be of therapeutic and diagnostic value in the emergency management of arrhythmias. It causes transient atrioventricular nodal block and thus ends paroxysmal supraventricular tachycardias that involve the atrioventricular node. Also, it may uncover underlying atrial arrhythmias by slowing the ventricular response. Its duration of action is brief and serious adverse effects have not been reported. A 12 year old patient with atrial flutter is presented, in whom intravenous adenosine was followed by acceleration of the heart rate to a potentially dangerous arrhythmia. PMID:8461228

Rankin, A C; Rae, A P; Houston, A

1993-03-01

254

Phosphorylation of Adenosine with Trimetaphosphate Under Simulated Prebiotic Conditions  

NASA Astrophysics Data System (ADS)

The phosphorylation of adenosine with trimetaphosphate in solution, in solid phase and using wet-dry cycles was carried out and it was found that wet-dry cycles were the most efficient. The catalytic effects of some metal ions on the phosphorylation were also studied and it was discovered that Ni(II) is the most effective. The combination of wet-dry cycles (4 cycles) and catalysis by Ni(II) led to an unprecedented high conversion of adenosine to phosphorylated products (30%) near neutral pH. The main phosphorylated products were 2', 3'-cyclic AMP (10.4%) and 5'-ATP (13.0%).

Cheng, Changmei; Fan, Chang; Wan, Rong; Tong, Chunyuan; Miao, Zhiwei; Chen, Jing; Zhao, Yufen

2002-06-01

255

Synthesis of 1,N6-etheno-2-aza-adenosine (2-aza-?-adenosine): a new cytotoxic fluorescent nucleoside  

PubMed Central

1,N6-Etheno-2-aza-adenosine was synthesized by treating 1,N6-etheno-adenosine with alkali, followed by nitrosation. The mechanism of formation of this novel nucleoside was elucidated using adenosine tritiated at C-8 and C-2, and was found to deformylate exclusively at C-2. This new 2-aza nucleoside fluoresces at 494 nm when excited at 358 nm. Toxicity study showed the compound is active in a rat mammary tumor tissue culture line, but inactive in HeLa and Glioma 26 tissue culture lines. It was also found to selectively inhibit the thymidine incorporation into DNA in a rat mammary tumor, but exhibits no ill effect on normal proliferative tissue. The reactive intermediate 3-?-D-ribofuranosyl-4-amino-5-(imidazol-2-yl) imidazole was identified and was found to be an active agent in tissue culture. PMID:10793738

Tsou, K.C.; Yip, K.F.; Miller, E.E.; Lo, K.W.

1974-01-01

256

Purification and properties of adenylyl sulphate:ammonia adenylyltransferase from Chlorella catalysing the formation of adenosine 5?-phosphoramidate from adenosine 5?-phosphosulphate and ammonia  

PubMed Central

Extracts of Chlorella pyrenoidosa, Euglena gracilis var. bacillaris, spinach, barley, Dictyostelium discoideum and Escherichia coli form an unknown compound enzymically from adenosine 5?-phosphosulphate in the presence of ammonia. This unknown compound shares the following properties with adenosine 5?-phosphoramidate: molar proportions of constituent parts (1 adenine:1 ribose:1 phosphate:1 ammonia released at low pH), co-electrophoresis in all buffers tested including borate, formation of AMP at low pH through release of ammonia, mass and i.r. spectra and conversion into 5?-AMP by phosphodiesterase. This unknown compound therefore appears to be identical with adenosine 5?-phosphoramidate. The enzyme that catalyses the formation of adenosine 5?-phosphoramidate from ammonia and adenosine 5?-phosphosulphate was purified 1800-fold (to homogeneity) from Chlorella by using (NH4)2SO4 precipitation and DEAE-cellulose, Sephadex and Reactive Blue 2–agarose chromatography. The purified enzyme shows one band of protein, coincident with activity, at a position corresponding to 60000–65000 molecular weight, on polyacrylamide-gel electrophoresis, and yields three subunits on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of 26000, 21000 and 17000 molecular weight, consistent with a molecular weight of 64000 for the native enzyme. Isoelectrofocusing yields one band of pI4.2. The pH optimum of the enzyme-catalysed reaction is 8.8. ATP, ADP or adenosine 3?-phosphate 5?-phosphosulphate will not replace adenosine 5?-phosphosulphate, and the apparent Km for the last-mentioned compound is 0.82mm. The apparent Km for ammonia (assuming NH3 to be the active species) is about 10mm. A large variety of primary, secondary and tertiary amines or amides will not replace ammonia. One mol.prop. of adenosine 5?-phosphosulphate reacts with 1 mol.prop. of ammonia to yield 1 mol.prop. each of adenosine 5?-phosphoramidate and sulphate; no AMP is found. The highly purified enzyme does not catalyse any of the known reactions of adenosine 5?-phosphosulphate, including those catalysed by ATP sulphurylase, adenosine 5?-phosphosulphate kinase, adenosine 5?-phosphosulphate sulphotransferase or ADP sulphurylase. Adenosine 5?-phosphoramidate is found in old samples of the ammonium salt of adenosine 5?-phosphosulphate and can be formed non-enzymically if adenosine 5?-phosphosulphate and ammonia are boiled. In the non-enzymic reaction both adenosine 5?-phosphoramidate and AMP are formed. Thus the enzyme forms adenosine 5?-phosphoramidate by selectively speeding up an already favoured reaction. ImagesFig. 4. PMID:6274307

Fankhauser, Heinz; Schiff, Jerome A.; Garber, Leonard J.

1981-01-01

257

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

PubMed Central

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

2014-01-01

258

Ecto-5?-Nucleotidase (CD73)-Mediated Formation of Adenosine Is Critical for the Striatal Adenosine A2A Receptor Functions  

PubMed Central

Adenosine is a neuromodulator acting through inhibitory A1 receptors (A1Rs) and facilitatory A2ARs, which have similar affinities for adenosine. It has been shown that the activity of intracellular adenosine kinase preferentially controls the activation of A1Rs, but the source of the adenosine activating A2ARs is unknown. We now show that ecto-5?-nucleotidase (CD73), the major enzyme able to convert extracellular AMP into adenosine, colocalizes with A2ARs in the basal ganglia. In addition to astrocytes, striatal CD73 is prominently localized to postsynaptic sites. Notably, CD73 coimmunoprecipitated with A2ARs and proximity ligation assays confirmed the close proximity of CD73 and A2ARs in the striatum. Accordingly, the cAMP formation in synaptosomes as well as the hypolocomotion induced by a novel A2AR prodrug that requires CD73 metabolization to activate A2ARs were observed in wild-type mice, but not in CD73 knock-out (KO) mice or A2AR KO mice. Moreover, CD73 KO mice displayed increased working memory performance and a blunted amphetamine-induced sensitization, mimicking the phenotype of global or forebrain-A2AR KO mice, as well as upon pharmacological A2AR blockade. These results show that CD73-mediated formation of extracellular adenosine is responsible for the activation of striatal A2AR function. This study points to CD73 as a new target that can fine-tune A2AR activity, and a novel therapeutic target to manipulate A2AR-mediated control of striatal function and neurodegeneration. PMID:23843511

Augusto, Elisabete; Matos, Marco; Sévigny, Jean; El-Tayeb, Ali; Bynoe, Margaret S.; Müller, Christa E.

2013-01-01

259

Effect of water-soluble silicon supplementation on bone status and balance of calcium and magnesium in male mice.  

PubMed

Silicon (Si) is important for the growth and development of bone and connective tissues. Several studies have reported that Si supplementation improved bone mineral density (BMD) in female ovarectomized rats. However, few studies have investigated the effects of Si supplementation on bone status and bone metabolism in male animals. The purpose of this study was to investigate the effects of Si supplementation on BMD and balance of calcium (Ca) and magnesium (Mg) in adult male mice. Si was administrated orally through demineralized water containing different contents of Si as a form of sodium metasilicate (0 %, control; 0.025 %, Si50; 0.050 %, Si100; and 0.075 %, Si150) to 9-week-old male mice for 4 weeks. Si supplementation did not alter weight gain or BMD of femur and tibia in male mice. However, a high level of Si (0.05 and 0.075 %) supplementation significantly decreased Mg retention without changing Ca retention. Serum alkaline phosphatase of Si-supplemented groups significantly decreased compared with that of the control. According to these results, short-term Si supplementation did not affect BMD but showed a possible effect on increasing the need for Mg in adult male mice. PMID:24664270

Kim, Mi-Hyun; Kim, Eun-Jin; Jung, Ji-Youn; Choi, Mi-Kyeong

2014-05-01

260

The Effect of Calcium and Magnesium on Carbonate Mineral Precipitation during Reactive Transport in a Model Subsurface Pore Structure  

NASA Astrophysics Data System (ADS)

Carbonate mineral precipitation in the subsurface at the interface of two advecting fluids can result in physical and chemical changes in the pore network. This can affect various applications including carbon sequestration. In this work, we evaluate the precipitation kinetics of carbonates in a microfluidic pore network when carbonate in water is mixed transverse to flow with a synthetic brine containing an equimolar concentration of calcium (Ca, 10 mM) and concentrations of magnesium (Mg) ranging from 2 to 40 mM. Mineral precipitation was monitored using reflected brightfield microscopy and mineral polymorphs were determined using Raman spectroscopy. Although Mg was present, only calcium carbonate (CaCO3) polymorphs were observed. The presence of Mg affected both the rate of precipitation and the prevalence of different CaCO3 morphologies. The rate of precipitation with 40mM Mg was about half of the rate as when no Mg was present. The calcium carbonate polymorph aragonite increased from <5% of the precipitated crystal area to >20% as the Mg concentration increased from 0 mM to 40 mM. Energy dispersive spectroscopy (EDS) results showed Mg2+ incorporated into the crystal lattice of the CaCO3 polymorph calcite at 8 to 14 mole% when Mg concentration in solution was highest. The incorporation of Mg2+ into the crystals was likely responsible for the reduction in precipitation rate at high solution concentrations of Mg. Significant pore blockage occurred along the mixing zone, indicating that carbonate precipitation may be of concern along the CO2 plume margins and affect the efficiency of CO2 injection.

Boyd, V.; Werth, C. J.; Valocchi, A. J.; Fouke, B. W.

2012-12-01

261

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

PubMed

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

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

2013-12-01

262

Structural basis for calcium and magnesium regulation of a large conductance calcium-activated potassium channel with ?1 subunits.  

PubMed

Large conductance Ca(2+)- and voltage-activated potassium (BK) channels, composed of pore-forming ? subunits and auxiliary ? subunits, play important roles in diverse physiological activities. The ?1 is predominately expressed in smooth muscle cells, where it greatly enhances the Ca(2+) sensitivity of BK channels for proper regulation of smooth muscle tone. However, the structural basis underlying dynamic interaction between BK mSlo1 ? and ?1 remains elusive. Using macroscopic ionic current recordings in various Ca(2+) and Mg(2+) concentrations, we identified two binding sites on the cytosolic N terminus of ?1, namely the electrostatic enhancing site (mSlo1(K392,R393)-?1(E13,T14)), increasing the calcium sensitivity of BK channels, and the hydrophobic site (mSlo1(L906,L908)-?1(L5,V6,M7)), passing the physical force from the Ca(2+) bowl onto the enhancing site and S6 C-linker. Dynamic binding of these sites affects the interaction between the cytosolic domain and voltage-sensing domain, leading to the reduction of Mg(2+) sensitivity. A comprehensive structural model of the BK(mSlo1 ?-?1) complex was reconstructed based on these functional studies, which provides structural and mechanistic insights for understanding BK gating. PMID:24764303

Liu, Hao-Wen; Hou, Pan-Pan; Guo, Xi-Ying; Zhao, Zhi-Wen; Hu, Bin; Li, Xia; Wang, Lu-Yang; Ding, Jiu-Ping; Wang, Sheng

2014-06-13

263

Effects of oligofructose-enriched inulin on intestinal absorption of calcium and magnesium and bone turnover markers in postmenopausal women  

Technology Transfer Automated Retrieval System (TEKTRAN)

Deficiency of oestrogen at menopause decreases intestinal Ca absorption, contributing to a negative Ca balance and bone loss. Mg deficiency has also been associated with bone loss. The purpose of the present investigation was to test the hypothesis that treatment with a spray-dried mixture of chicor...

264

Changes in sodium, calcium and magnesium ion concentrations in sturgeon ( Huso huso ) urine and in kidney morphology  

Microsoft Academic Search

During adaptation to brackish water the young great sturgeon Huso huso is able to regulate its serum osmolarity and ion concentrations. After transfer from fresh water to brackish water the ion concentrations in the urine increase and the urine becomes isoosmotic to the blood serum after 24h. The Na+ and K+ concentrations in the urine increase during the first 12

L. S. Krayushkina; A. A. Panov; A. A. Gerasimov; W. T. W. Potts

1996-01-01

265

Calcium and magnesium transport in the cortical thick ascending limb of Henle’s loop: influence of age and gender  

Microsoft Academic Search

Previous studies from our laboratory have shown that Ca2+ and Mg2+ absorption in the mouse cortical thick ascending limb of Henle’s loop (cTAL) is a passive, paracellular process driven by\\u000a the transepithelial voltage. The passive permeability of the epithelium is enhanced by peptide hormones. The present study\\u000a investigated whether divalent cation absorption in the cTAL is influenced by cell maturation

M. Wittner; E. Desfleurs; S. Pajaud; G. Moine; S. Simeone; C. de Rouffignac; A. Di Stefano

1997-01-01

266

Calcium and magnesium transport in the cortical thick ascending limb of Henle's loop: influence of age and gender.  

PubMed

Previous studies from our laboratory have shown that Ca2+ and Mg2+ absorption in the mouse cortical thick ascending limb of Henle's loop (cTAL) is a passive, paracellular process driven by the transepithelial voltage. The passive permeability of the epithelium is enhanced by peptide hormones. The present study investigated whether divalent cation absorption in the cTAL is influenced by cell maturation and/or gender. For this purpose, mouse cTAL segments were microdissected from kidneys of female and male animals aged 4 and 8 weeks. The microdissected tubules were perfused in vitro at a luminal flow rate of 1.5 to 2.5 nl/min. Transepithelial Na+, Cl-, Ca2+ and Mg2+ net fluxes (JX, pmol.min-1.mm-1) were measured using electron microprobe analysis, and the transepithelial potential difference (PDte) was measured continuously. No differences were found in the PDte, JNa and JCl of the various animal groups but the transepithelial Ca2+ and Mg2+ transport capacity of the cTAL was higher in adults (8 weeks) than in young animals (4 weeks). Furthermore, irrespective of age, transepithelial Ca2+ net absorption was greater in male than in female animals. In contrast, the NaCl transport was maximal at 4 weeks in both genders. We conclude therefore that transepithelial divalent cation absorption in the mouse cTAL is an inductive process influenced by cell maturation and gender. The molecular basis of these inductions remains to be elucidated. PMID:9211812

Wittner, M; Desfleurs, E; Pajaud, S; Moine, G; Simeone, S; de Rouffignac, C; Di Stefano, A

1997-08-01

267

Calcium and Magnesium: Low Passive Permeability and Tubular Secretion in the Mouse Medullary Thick Ascending Limb of Henle's Loop (MTAL)  

Microsoft Academic Search

.   Recent studies from our laboratory have shown that in the mouse and rat nephron Ca2+ and Mg2+ are not reabsorbed in the medullary part of the thick ascending limb (mTAL) of Henle's loop. The aim of the present study\\u000a was to investigate whether the absence of transepithelial Ca2+ and Mg2+ transport in the mouse mTAL is due to its

M. Wittner; E. Desfleurs; S. Pajaud; G. Moine; C. de Rouffignac; A. Di Stefano

1996-01-01

268

Calcium and magnesium: low passive permeability and tubular secretion in the mouse medullary thick ascending limb of Henle's loop (MTAL).  

PubMed

Recent studies from our laboratory have shown that in the mouse and rat nephron Ca2+ and Mg2+ are not reabsorbed in the medullary part of the thick ascending limb (mTAL) of Henle's loop. The aim of the present study was to investigate whether the absence of transepithelial Ca2+ and Mg2+ transport in the mouse mTAL is due to its relative low permeability to divalent cations. For this purpose, transepithelial ion net fluxes were measured by electron probe analysis in isolated perfused mouse mTAL segments, when the transepithelial potential difference (PDte.) was varied by chemical voltage clamp, during active NaCl transport inhibition by luminal furosemide. The results show that transepithelial Ca2+ and Mg2+ net fluxes in the mTAL are not driven by the transepithelial PDte. At zero voltage, a small but significant net secretion of Ca2+ into the tubular lumen was observed. With a high lumen-positive PDte generated by creating a transepithelial bath-to-lumen NaCl concentration gradient, no Ca2+ and Mg2+ reabsorption was noted; instead significant and sustained Ca2+ and Mg2+ net secretion occurred. When a lumen-positive PDte was generated in the absence of apical furosemide, but in the presence of a transepithelial bath-to-lumen NaCl concentration gradient, a huge Ca2+ net secretion and a lesser Mg2+ net secretion, not modified by ADH, were observed. Replacement of Na+ by K+ in the lumen perfusate induced, in the absence of PDte changes, important but reversible net secretions of Ca2+ and Mg2+. In conclusion, our results indicate that the passive permeability of the mouse mTAL to divalent cations is very low and not influenced by ADH. This nephron segment can secrete Ca2+ and Mg2+ into the luminal fluid under conditions which elicit large lumen-positive transepithelial potential differences. Given the impermeability of this epithelium to Ca2+ and Mg2+, the secretory processes would appear to be of cellular origin. PMID:8694904

Wittner, M; Desfleurs, E; Pajaud, S; Moine, G; de Rouffignac, C; Di Stefano, A

1996-09-01

269

Effects of head-out water immersion on the urinary excretion of phosphate, calcium and magnesium in the awake dog.  

PubMed

The present study was undertaken to define the effects of heat-out water immersion on the urinary excretion of phosphate (UPO4V), calcium (UCaV), and magnesium (UMgV) in the awake dog. 53 dogs were divided into three groups: group I, time-control, from 10 a.m. to 4 p.m.; group II, immersion for 2 h, studied from 10 a.m. to 4 p.m., and group III, immersion for 2 h, studied from 4 p.m. to 10 p.m. Our results show that head-out water immersion did not alter the spontaneous pattern of UPO4V. When immersion was performed from 1 p.m. to 3. p.m. (group II), it had no effect on UCaV but induced a significant increase in UMgV although fractional excretion of Mg (FEMg) remained unchanged. When immersion was performed from 7 p.m. to 9 p.m. (group III), however, both UCaV and UMgV increased significantly. FECa also increased significantly in this group but FEMg again remained unchanged. The changes in UCaV were dissociated with UNaV. Changes in plasma PO4 (PPO4) and arterial pH were unrelated to changes in UCaV or UPO4V. Our findings show that head-out water immersion induces significant increases in UCaV and UMgV by mechanisms which are independent of parathyroid hormone (PTH) or acid base changes. The rise in UMgV seems to be related to an increase in the filtered load, while the increases in UCaV are secondary to changes in the renal tubular handling of calcium. Thus, under these experimental circumstances, Ca and Mg reabsorption seem to occur via different distal tubular pathways.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6738466

Ayus, J C; Frommer, J P; Eknoyan, G; Divine, G; Suki, W N

1984-01-01

270

Ion chromatographic determination of calcium and magnesium cations in human saliva and urine with a piezoelectric detector  

Microsoft Academic Search

A rapid sample extraction procedure for the determination of ascorbic acid (AA) by high performance liquid chromatography (HPLC) in multivitamin-mineral formulations containing interfering copper has been developed. The method takes special precautions to prevent degradation of AA in contact with high concentrations of interfering elements such as copper. Sample preparation involved addition of pyrogallol, citric acid solution and short time

Bing-Sheng Yu; Qian-Gen Yuan; Li-Hua Nie; Shou-Zhuo Yao

2001-01-01

271

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...

272

Dietary inulin intake and age can significantly affect intestinal absorption of calcium and magnesium in rats: a stable isotope approach  

PubMed Central

Background previous studies have shown that non-digestible inulin-type fructan intake can increase intestinal mineral absorption in both humans and animals. However, this stimulatory effect on intestinal absorption may depend on experimental conditions such as duration of fermentable fiber intake, mineral diet levels and animals' physiological status, in particular their age. Objectives the aim of this study was to determine the effect of inulin intake on Ca and Mg absorption in rats at different age stages. Methods eighty male Wistar rats of four different ages (2, 5, 10 and 20 months) were randomized into either a control group or a group receiving 3.75% inulin in their diet for 4 days and then 7.5% inulin for three weeks. The animals were fed fresh food and water ad libitum for the duration of the experiment. Intestinal absorption of Ca and Mg was determined by fecal monitoring using stable isotopic tracers. Ca and Mg status was also assessed. Results absorption of Ca and Mg was significantly lower in the aged rats (10 and 20 mo) than in the young and adult rat groups. As expected, inulin intake increased Ca and Mg absorption in all four rat groups. However, inulin had a numerically greater effect on Ca absorption in aged rats than in younger rats whereas its effect on Mg absorption remained similar across all four rat age groups. Conclusion the extent of the stimulatory effect of inulin on absorption of Ca may differ according to animal ages. Further studies are required to explore this effect over longer inulin intake periods, and to confirm these results in humans. PMID:16253138

Coudray, Charles; Rambeau, Mathieu; Feillet-Coudray, Christine; Tressol, Jean Claude; Demigne, Christian; Gueux, Elyett; Mazur, Andrzej; Rayssiguier, Yves

2005-01-01

273

Influence of NPK fertilization on calcium and magnesium in Poa pratensis L. with reference to dietary requirements of grazing cattle  

Microsoft Academic Search

A two?year experiment was conducted on Edwards muck (Limnic Medisaprist) on the Pinney?Purdue Agricultural Center at Wanatah, Indiana to study the effect of NPK fertilization on Ca and Mg concentrations in Kentucky bluegrass (Poa pratensis L.). Eight combinations of N?P?K fertilizer (0–0–0, 0–99–0, 0–0–372, 0–99–372, 168–0–0, 168–99–0, 168–0–372, 168–99–372 kg\\/ha), were applied each spring. Four cuttings were taken annually during

J. W. Lightner; C. L. Rhykerd; D. B. Mengel; G. E. Van Scoyoc; E. L. Hood; C. H. Noller

1983-01-01

274

Individual effects of sodium, potassium, calcium, and magnesium chloride salts on Lactobacillus pentosus and Saccharomyces cerevisiae growth.  

PubMed

A quantitative investigation on the individual effects of sodium (NaCl), potassium (KCl), calcium (CaCl2), and magnesium (MgCl2) chloride salts against Lactobacillus pentosus and Saccharomyces cerevisiae, two representative microorganisms of table olives and other fermented vegetables, was carried out. In order to assess their potential activities, both the kinetic growth parameters and dose-response profiles in synthetic media (deMan Rogosa Sharpe broth medium and yeast-malt-peptone-glucose broth medium, respectively) were obtained and analyzed. Microbial growth was monitored via optical density measurements as a function of contact time in the presence of progressive chloride salt concentrations. Relative maximum specific growth rate and lag-phase period were modeled as a function of the chloride salt concentrations. Moreover, for each salt and microorganism tested, the noninhibitory concentrations and the MICs were estimated and compared. All chloride salts exerted a significant antimicrobial effect on the growth cycle; particularly, CaCl2 showed a similar effect to NaCl, while KCl and MgCl2 were progressively less inhibitory. Microbial susceptibility and resistance were found to be nonlinearly dose related. PMID:18680941

Bautista-Gallego, J; Arroyo-López, F N; Durán-Quintana, M C; Garrido-Fernandez, A

2008-07-01

275

A2A receptor dependent and A2A receptor independent effects of extracellular adenosine on murine thymocytes in conditions of adenosine deaminase deficiency  

Microsoft Academic Search

Adenosine deaminase (ADA) deficiency causes severe combined immunodefi- ciency (SCID) and is accompanied by T-cell depletion and accumulation of both intracellular and extracellular adenosine (extAdo) and deoxyadenosine. To better understand the causes of T-cell depletion in vivo and to discriminate between extracellular and intracellular effects of exogenously added adenosine in vitro, we investigated mechanisms of 2 differ- ent effects of

Sergey Apasov; Jiang-Fan Chen; Patrick Smith; Michail Sitkovsky

2000-01-01

276

Role of adenosine kinase in the control of Streptomyces differentiations: Loss of adenosine kinase suppresses sporulation and actinorhodin biosynthesis while inducing hyperproduction of undecylprodigiosin in Streptomyces lividans  

Microsoft Academic Search

Adenosine kinase (ADK) catalyses phosphorylation of adenosine (Ado) and generates adenosine monophosphate (AMP). ADK gene (adkSli, an ortholog of SCO2158) was disrupted in Streptomyces lividans by single crossover-mediated vector integration. The adkSli disruption mutant (?adkSli) was devoid of sporulation and a plasmid copy of adkSli restored sporulation ability in ?adkSli, thus indicating that loss of adkSli abolishes sporulation in S.

Arishma Rajkarnikar; Hyung-Jin Kwon; Joo-Won Suh

2007-01-01

277

Role of Extracellular Adenosine in Acute Lung Injury  

NSDL National Science Digital Library

Acute lung injury (ALI) is a lung disease characterized by pulmonary edema and severe hypoxia. The past decade hosted a search for endogenous mechanisms controlling lung inflammation and pulmonary edema during ALI. As such, recent evidence indicates extracellular adenosine in orchestrating the resolution of pulmonary edema and inflammation during ALI.

Tobias Eckle (University of Colorado Denver Anesthesiology, Mucosal Inflammation Program)

2009-10-01

278

Sensorineural deafness in siblings with adenosine deaminase deficiency  

Microsoft Academic Search

Two siblings with adenosine deaminase deficiency were successfully treated with allogeneic bone marrow transplantation without conditioning. Although the patients were free from infections after immumologic reconstitution, both showed sensorineural deafness at 1 year of age. Because there were no structural abnormalities in the inner and middle ears, no evidence of prenatal infections of rubella, cytomegalovirus or toxoplasma, and no postnatal

Chitose Tanaka; Toshiro Hara; Ichiro Suzaki; Yoshihiro Maegaki; Kenzo Takeshita

1996-01-01

279

Gene Therapy for Immunodeficiency Due to Adenosine Deaminase Deficiency  

Microsoft Academic Search

Background We investigated the long-term outcome of gene therapy for severe combined immu- nodeficiency (SCID) due to the lack of adenosine deaminase (ADA), a fatal disorder of purine metabolism and immunodeficiency. Methods We infused autologous CD34+ bone marrow cells transduced with a retroviral vec- tor containing the ADA gene into 10 children with SCID due to ADA deficiency who lacked

Alessandro Aiuti; Federica Cattaneo; Stefania Galimberti; Ulrike Benninghoff; Barbara Cassani; Luciano Callegaro; Samantha Scaramuzza; Grazia Andolfi; Massimiliano Mirolo; Immacolata Brigida; Antonella Tabucchi; Filippo Carlucci; Martha Eibl; Memet Aker; Shimon Slavin; Hamoud Al-Mousa; Abdulaziz Al Ghonaium; Alina Ferster; Andrea Duppenthaler; Luigi Notarangelo; Uwe Wintergerst; Rebecca H. Buckley; Marco Bregni; Sarah Marktel; Maria Grazia Valsecchi; Paolo Rossi; Fabio Ciceri; Roberto Miniero; Claudio Bordignon; Maria-Grazia Roncarolo

2009-01-01

280

Intravascular adenosine: the endothelial mediators of its negative dromotropic effects  

Microsoft Academic Search

Intravascular adenosine may exert its negative dromotropic effect via activation of luminal coronary endothelial receptors, which suggests the presence of transcellular dromotropic mediators of endothelial origin, perhaps nitric oxide (NO) and prostaglandins. We decided to test this hypothesis in isolated guinea pig hearts retrogradely perfused with Krebs–Henseleit solution. A pair of stimulating electrodes were placed in the right atria and

Rafael Rubio; Guillermo Ceballos; Eduardo Balcells

1999-01-01

281

Synthesis of oligo-RNAs with photocaged adenosine 2-hydroxyls  

E-print Network

caged adenosine, modified at the 2˘ position as a nitro-benzyl ether, can be incorporated into short, a caging approach might be used to block either chemical reactivity of the RNA or formation of secondary- tions with 2˘-hydroxyl groups are critical in the formation of higher order RNA struc- tures as well

Glover, Mark

282

Adenosine is crucial for deep brain stimulationmediated attenuation of tremor  

E-print Network

Adenosine is crucial for deep brain stimulation­mediated attenuation of tremor Lane Bekar1 (DBS) is a widely used neurosurgical approach to treating tremor and other movement disorders1 excitatory transmission in the thalamus and reduces both tremor- and DBS-induced side effects. Intrathalamic

Newman, Eric A.

283

Acceleration of ventricular response to atrial flutter after intravenous adenosine  

Microsoft Academic Search

Adenosine may be of therapeutic and diagnostic value in the emergency management of arrhythmias. It causes transient atrioventricular nodal block and thus ends paroxysmal supraventricular tachycardias that involve the atrioventricular node. Also, it may uncover underlying atrial arrhythmias by slowing the ventricular response. Its duration of action is brief and serious adverse effects have not been reported. A 12 year

A C Rankin; A P Rae; A Houston

1993-01-01

284

Transgenic overexpression of adenosine kinase aggravates cell death in ischemia.  

PubMed

Adenosine is an endogenous neuromodulator with anticonvulsive and neuroprotective activity. Adenosine levels are normally kept in the range of 20 to 200 nmol/L by low basal expression of its main metabolic enzyme, adenosine kinase (ADK). Dysfunction of the adenosinergic system has been demonstrated to contribute to epileptogenesis. To investigate whether upregulation of ADK may render the brain more susceptible to ischemic cell death, mutant mice overexpressing an Adk transgene in brain were subjected to middle cerebral artery occlusion (MCAO). One day after either 15 or 60 mins of MCAO, wild-type (WT) animals had infarct areas encompassing about 5% and 50% of their ischemic hemisphere, respectively. In marked contrast, the volume of the infarcts increased three-fold in Adk transgenic mutants after 15 mins of MCAO, and after 60 mins of MCAO all mutants died within 24 h. Pretreatment of the mutants with the ADK inhibitor 5-iodotubercidin led to lesions similar to those in WT mice. Thus, low levels of ADK are essential to maintain adenosine-mediated neuroprotection. We conclude that pathologic overexpression of ADK as in epilepsy may also render the brain more susceptible to injury from ischemia. Consequently, ADK emerges as a rational therapeutic target to enhance neuroprotection. PMID:16685255

Pignataro, Giuseppe; Simon, Roger P; Boison, Detlev

2007-01-01

285

Crystal Structure of Adenosine 5-Phosphosulfate Kinase from Penicillium chrysogenum,  

E-print Network

Crystal Structure of Adenosine 5-Phosphosulfate Kinase from Penicillium chrysogenum, Ian J. Mac crystal structure of ligand-free APS kinase from the filamentous fungus, Penicillium chrysogenum focuses on APS kinase from the filamentous fungus, Penicillium chrysogenum, an enzyme possessing several

Fisher, Andrew J.

286

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

PubMed Central

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

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

2014-01-01

287

Adenosine augmentation therapies (AATs) for epilepsy: prospect of cell and gene therapies.  

PubMed

Deficiencies in the brain's own adenosine-based seizure control system contribute to seizure generation. Consequently, reconstitution of adenosinergic neuromodulation constitutes a rational approach for seizure control. This review will critically discuss focal adenosine augmentation strategies and their potential for antiepileptic and disease modifying therapy. Due to systemic side effects of adenosine focal adenosine augmentation--ideally targeted to an epileptic focus--becomes a therapeutic necessity. This has experimentally been achieved in kindled seizure models as well as in post-status epilepticus models of spontaneous recurrent seizures using three different therapeutic strategies that will be discussed here: (i) polymer-based brain implants that were loaded with adenosine; (ii) brain implants comprised of cells engineered to release adenosine and embedded in a cell-encapsulation device; (iii) direct transplantation of stem cells engineered to release adenosine. To meet the therapeutic goal of focal adenosine augmentation, genetic disruption of the adenosine metabolizing enzyme adenosine kinase (ADK) in rodent and human cells was used as a molecular strategy to induce adenosine release from cellular brain implants, which demonstrated antiepileptic and neuroprotective properties. New developments and therapeutic challenges in using AATs for epilepsy therapy will critically be evaluated. PMID:19428218

Boison, Detlev

2009-08-01

288

Neuronal adenosine release, and not astrocytic ATP release, mediates feedback inhibition of excitatory activity  

PubMed Central

Adenosine is a potent anticonvulsant acting on excitatory synapses through A1 receptors. Cellular release of ATP, and its subsequent extracellular enzymatic degradation to adenosine, could provide a powerful mechanism for astrocytes to control the activity of neural networks during high-intensity activity. Despite adenosine's importance, the cellular source of adenosine remains unclear. We report here that multiple enzymes degrade extracellular ATP in brain tissue, whereas only Nt5e degrades AMP to adenosine. However, endogenous A1 receptor activation during cortical seizures in vivo or heterosynaptic depression in situ is independent of Nt5e activity, and activation of astrocytic ATP release via Ca2+ photolysis does not trigger synaptic depression. In contrast, selective activation of postsynaptic CA1 neurons leads to release of adenosine and synaptic depression. This study shows that adenosine-mediated synaptic depression is not a consequence of astrocytic ATP release, but is instead an autonomic feedback mechanism that suppresses excitatory transmission during prolonged activity. PMID:22421436

Lovatt, Ditte; Xu, Qiwu; Liu, Wei; Takano, Takahiro; Smith, Nathan A.; Schnermann, Jurgen; Tieu, Kim; Nedergaard, Maiken

2012-01-01

289

Acyl Coenzyme A Synthetase from Pseudomonas fragi Catalyzes the Synthesis of Adenosine 59-Polyphosphates and Dinucleoside Polyphosphates  

Microsoft Academic Search

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-(g-thiotriphosphate) (ATPgS), 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.

RUI FONTES; MARIA A. GUNTHER SILLERO; ANTONIO SILLERO

1998-01-01

290

Burkitt's lymphoma in a patient with adenosine deaminase deficiency-severe combined immunodeficiency treated with polyethylene glycol-adenosine deaminase.  

PubMed

We describe a patient with severe combined immunodeficiency because of aberrations in adenosine deaminase (ADA) who despite adequate replacement with polyethylene glycol-linked ADA (PEG-ADA) for 13 years developed Burkitt's lymphoma. Although treatment corrected the metabolic abnormalities caused by ADA deficiency, it failed to fully restore cellular immunity. PMID:17586199

Husain, Maitham; Grunebaum, Eyal; Naqvi, Ahmed; Atkinson, Adelle; Ngan, Bo-Yee; Aiuti, Alessandro; Roifman, Chaim M

2007-07-01

291

Studies on the adenosine deaminase-catalyzed conversion of adenosine and nucleoside prodrugs by different capillary electrophoresis modes.  

PubMed

Four kinds of fast and efficient capillary electrophoresis modes, i.e., immobilized enzymatic reactor (IER), electrophoretically mediated microanalysis (EMMA), capillary zone electrophoresis (CZE), and micellar electrokinetic chromatography (MEKC), were first developed to study the adenosine deaminase (ADA)-catalyzed conversion of adenosine and nucleoside prodrugs, which is critical for releasing prodrugs into the intracellular compartment for phosphorylation. The enzyme-activated prodrug approach is a strategy that has been successfully employed to improve physicochemical and pharmacokinetic properties of potential therapeutic agents, especially in the search for antiviral nucleoside analogues. Adenosine, amino-ddG, and amino-D4G could be converted by ADA to different extents under our experimental conditions. Steady-state parameters K(m), V(max), and k(cat) were also determined. The substrate efficiencies (k(cat)/K(m)) of adenosine, amino-ddG, and amino-D4G were 0.19ą0.01, 0.047ą0.005, and 0.017ą0.010 ?M(-1) s(-1), respectively. The enzymatic reaction could be performed at a nanoliter scale and all manipulation steps were combined into a fully automated assay in on-line modes, which opened the possibilities of high-throughput screening of large libraries of synthetic nucleoside analogues for biological activity and a relative mechanism study of nucleoside and its analogues. PMID:21402044

Pei, Lu; Xie, Lujia; Lin, Qian; Ling, Xiaomei; Guan, Zhu; Yang, Zhenjun

2011-07-01

292

Sustained adenosine exposure causes lung endothelial apoptosis: a possible contributor to cigarette smoke-induced endothelial apoptosis and lung injury.  

PubMed

Pulmonary endothelial cell (EC) apoptosis has been implicated in the pathogenesis of emphysema. Cigarette smoke (CS) causes lung EC apoptosis and emphysema. In this study, we show that CS exposure increased lung tissue adenosine levels in mice, an effect associated with increased lung EC apoptosis and the development of emphysema. Adenosine has a protective effect against apoptosis via adenosine receptor-mediated signaling. However, sustained elevated adenosine increases alveolar cell apoptosis in adenosine deaminase-deficient mice. We established an in vitro model of sustained adenosine exposure by incubating lung EC with adenosine in the presence of an adenosine deaminase inhibitor, deoxycoformicin. We demonstrated that sustained adenosine exposure caused lung EC apoptosis via nucleoside transporter-facilitated intracellular adenosine uptake, subsequent activation of p38 and JNK in mitochondria, and ultimately mitochondrial defects and activation of the mitochondria-mediated intrinsic pathway of apoptosis. Our results suggest that sustained elevated adenosine may contribute to CS-induced lung EC apoptosis and emphysema. Our data also reconcile the paradoxical effects of adenosine on apoptosis, demonstrating that prolonged exposure causes apoptosis via nucleoside transporter-mediated intracellular adenosine signaling, whereas acute exposure protects against apoptosis via activation of adenosine receptors. Inhibition of adenosine uptake may become a new therapeutic target in treatment of CS-induced lung diseases. PMID:23316066

Lu, Qing; Sakhatskyy, Pavlo; Newton, Julie; Shamirian, Paul; Hsiao, Vivian; Curren, Sean; Gabino Miranda, Gustavo Andres; Pedroza, Mesias; Blackburn, Michael R; Rounds, Sharon

2013-03-01

293

Antiepileptic effects of silk-polymer based adenosine release in kindled rats  

PubMed Central

Pharmacotherapy for epilepsy is limited by high incidence of pharmacoresistance and failure to prevent development and progression of epilepsy. Using the rat hippocampal kindling model, we report on the therapeutic potential of novel silk-based polymers engineered to release the anticonvulsant adenosine. Polymers were designed to release 1000 ng adenosine per day during a time span of ten days. In the first experiment rats were kindled by hippocampal electrical stimulation until all animals reacted with stage 5 seizures. Adenosine-releasing or control polymers were then implanted into the infrahippocampal fissure ipsilateral to the site of stimulation. Subsequently, only recipients of adenosine-releasing implants were completely protected from generalized seizures over a period of ten days corresponding to the duration of sustained adenosine release. To monitor seizure-development in the presence of adenosine, adenosine-releasing or control polymers were implanted prior to kindling. After 30 stimulations – delivered from days 4–8 after implantation – control animals had developed convulsive stage 5 seizures, whereas recipients of adenosine-releasing implants were still protected from convulsive seizures. Kindling was resumed after nine days to allow expiration of adenosine-release. During additional 30 stimulations, recipients of adenosine-releasing implants gradually resumed kindling development at seizure stages corresponding to those when kindling was initially suspended, while control rats resumed kindling development at convulsive seizure stages. Blockade of adenosine A1 receptors did not exacerbate seizures in protected animals. We conclude that silk-based adenosine-delivery exerts potent anti-ictogenic effects, but might also have at least partial anti-epileptogenic effects. Thus, silk-based adenosine augmentation holds promise for the treatment of epilepsy. PMID:19460372

Szybala, Cory; Pritchard, Eleanor M.; Lusardi, Theresa A.; Li, Tianfu; Wilz, Andrew; Kaplan, David L.; Boison, Detlev

2009-01-01

294

Characterization of cardiac adenosine receptors using N/sup 6/-phenyladenosines and a new radioligand, (/sup 125/I)-(m-aminophenyl)adenosine  

SciTech Connect

The chick heart contains adenosine receptors with characteristics similar to the R adenosine receptors found in the CNS. They have synthesized several N/sup 6/-phenyladenosines and tested their potencies for inhibiting the binding of (/sup 125/I)(p-aminobenzyl)adenosine )(/sup 125/I)ABA) to chick heart membranes. Of the 12 compounds tested, N/sup 6/-(p-aminobenzyl) adenosine (ABA) was the least potent (IC/sub 50/ approx. 40 nM) while N/sup 6/-(m-nitrophenyl)adenosine(MNPA) was the most potent (IC/sub 50/ approx. 1 nM). The IC/sub 50/ of N/sup 6/-(m-aminophenyl)adenosine(MAPA) was greater than that of N/sup 6/-phenyladenosine(PA) while that of MNPA was less than that of PA. The effects of these electron-releasing (-NH/sub 2/) and electron-withdrawing (-NO/sub 2/) groups along with data obtained with other phenyl-substituted N/sup 6/-phenyladenosines suggest that the electron density of the N/sup 6/-nitrogen may affect the affinities of these compounds for the cardiac adenosine receptor. MAPA can be iodinated to produce a new ligand, (/sup 125/I)MAPA. This iodination, like that of ABA, increases the affinity of the compound and produces a ligand with good affinity and low nonspecific binding suitable for studies on tissues with low concentrations of adenosine receptors.

Kwatra, M.M.; Hosey, M.M.; Green, R.

1986-03-05

295

Abiotic regioselective phosphorylation of adenosine with borate in formamide.  

PubMed

Nearly 40 years ago, Schoffstall and his coworkers used formamide as a solvent to permit the phosphorylation of nucleosides by inorganic phosphate to give nucleoside phosphates, which (due to their thermodynamic instability with respect to hydrolysis) cannot be easily created in water by an analogous phosphorylation (the "water problem" in prebiotic chemistry). More recently, we showed that borate could stabilize certain carbohydrates against degradation (the "asphalt problem"). Here, we combine the two concepts to show that borate can work in formamide to guide the reactivity of nucleosides under conditions where they are phosphorylated. Specifically, reaction of adenosine in formamide with inorganic phosphate and pyrophosphate in the presence of borate gives adenosine-5'-phosphate as the only detectable phosphorylated product, with formylation (as opposed to hydrolysis) being the competing reaction. Key Words: Prebiotic chemistry-Nucleoside phosphates-Phosphorylation-Borate-Formamide. Astrobiology 15, 259-267. PMID:25826074

Furukawa, Yoshihiro; Kim, Hyo-Joong; Hutter, Daniel; Benner, Steven A

2015-04-01

296

Glial Adenosine Kinase – a Neuropathological Marker of the Epileptic Brain  

PubMed Central

Experimental research over the past decade has supported the critical role of astrocytes activated by different types of injury and the pathophysiological processes that underlie the development of epilepsy. In both experimental and human epileptic tissues astrocytes undergo complex changes in their physiological properties, which can alter glio-neuronal communication, contributing to seizure precipitation and recurrence. In this context, understanding which of the molecular mechanisms are crucially involved in the regulation of glio-neuronal interactions under pathological conditions associated with seizure development is important to get more insight into the role of astrocytes in epilepsy. This article reviews current knowledge regarding the role of glial adenosine kinase as a neuropathological marker of the epileptic brain. Both experimental findings in clinically relevant models, as well as observations in drug-resistant human epilepsies will be discussed, highlighting the link between astrogliosis, dysfunction of adenosine homeostasis and seizure generation and therefore suggesting new strategies for targeting astrocyte-mediated epileptogenesis. PMID:23385089

Aronica, Eleonora; Sandau, Ursula S; Iyer, Anand; Boison, Detlev

2013-01-01

297

5'-C-Ethyl-tetrazolyl-N(6)-Substituted Adenosine and 2-Chloro-adenosine Derivatives as Highly Potent Dual Acting A1 Adenosine Receptor Agonists and A3 Adenosine Receptor Antagonists.  

PubMed

A series of N(6)-substituted-5'-C-(2-ethyl-2H-tetrazol-5-yl)-adenosine and 2-chloro-adenosine derivatives was synthesized as novel, highly potent dual acting hA1AR agonists and hA3AR antagonists, potentially useful in the treatment of glaucoma and other diseases. The best affinity and selectivity profiles were achieved by N(6)-substitution with a 2-fluoro-4-chloro-phenyl- or a methyl- group. Through an in silico receptor-driven approach, the molecular bases of the hA1- and hA3AR recognition and activation of this series of 5'-C-ethyl-tetrazolyl derivatives were explained. PMID:25699637

Petrelli, Riccardo; Torquati, Ilaria; Kachler, Sonja; Luongo, Livio; Maione, Sabatino; Franchetti, Palmarisa; Grifantini, Mario; Novellino, Ettore; Lavecchia, Antonio; Klotz, Karl-Norbert; Cappellacci, Loredana

2015-03-12

298

Adenosine deaminase activity in the diagnosis of tuberculous peritonitis.  

PubMed Central

We studied the activity of adenosine deaminase in the peritoneal fluid of 66 patients who were divided into five groups according to causes of ascites as follows: tuberculous peritonitis (group I), septic peritonitis (group II), secondary to malignant tumours (group III), miscellaneous conditions (group IV), and control subjects of transudates (group V). In patients with tuberculous peritonitis the enzyme activity was significantly higher than for the rest of the groups (p less than 0.001), and enzyme concentrations in all patients were well above the upper non-tuberculous value. Adenosine deaminase activity in the peritoneal fluid has proved to be a simple and reliable method for early diagnosis of tuberculous peritonitis. PMID:3758818

Martinez-Vazquez, J M; Ocańa, I; Ribera, E; Segura, R M; Pascual, C

1986-01-01

299

Soluble ecto-5'-nucleotidase (5'-NT), alkaline phosphatase, and adenosine deaminase (ADA1) activities in neonatal blood favor elevated extracellular adenosine.  

PubMed

Extracellular adenosine, a key regulator of physiology and immune cell function that is found at elevated levels in neonatal blood, is generated by phosphohydrolysis of adenine nucleotides released from cells and catabolized by deamination to inosine. Generation of adenosine monophosphate (AMP) in blood is driven by cell-associated enzymes, whereas conversion of AMP to adenosine is largely mediated by soluble enzymes. The identities of the enzymes responsible for these activities in whole blood of neonates have been defined in this study and contrasted to adult blood. We demonstrate that soluble 5'-nucleotidase (5'-NT) and alkaline phosphatase (AP) mediate conversion of AMP to adenosine, whereas soluble adenosine deaminase (ADA) catabolizes adenosine to inosine. Newborn blood plasma demonstrates substantially higher adenosine-generating 5'-NT and AP activity and lower adenosine-metabolizing ADA activity than adult plasma. In addition to a role in soluble purine metabolism, abundant AP expressed on the surface of circulating neonatal neutrophils is the dominant AMPase on these cells. Plasma samples from infant observational cohorts reveal a relative plasma ADA deficiency at birth, followed by a gradual maturation of plasma ADA through infancy. The robust adenosine-generating capacity of neonates appears functionally relevant because supplementation with AMP inhibited whereas selective pharmacologic inhibition of 5'-NT enhanced Toll-like receptor-mediated TNF-? production in neonatal whole blood. Overall, we have characterized previously unrecognized age-dependent expression patterns of plasma purine-metabolizing enzymes that result in elevated plasma concentrations of anti-inflammatory adenosine in newborns. Targeted manipulation of purine-metabolizing enzymes may benefit this vulnerable population. PMID:23897810

Pettengill, Matthew; Robson, Simon; Tresenriter, Megan; Millán, José Luis; Usheva, Anny; Bingham, Taiese; Belderbos, Mirjam; Bergelson, Ilana; Burl, Sarah; Kampmann, Beate; Gelinas, Laura; Kollmann, Tobias; Bont, Louis; Levy, Ofer

2013-09-20

300

Soluble Ecto-5?-nucleotidase (5?-NT), Alkaline Phosphatase, and Adenosine Deaminase (ADA1) Activities in Neonatal Blood Favor Elevated Extracellular Adenosine*  

PubMed Central

Extracellular adenosine, a key regulator of physiology and immune cell function that is found at elevated levels in neonatal blood, is generated by phosphohydrolysis of adenine nucleotides released from cells and catabolized by deamination to inosine. Generation of adenosine monophosphate (AMP) in blood is driven by cell-associated enzymes, whereas conversion of AMP to adenosine is largely mediated by soluble enzymes. The identities of the enzymes responsible for these activities in whole blood of neonates have been defined in this study and contrasted to adult blood. We demonstrate that soluble 5?-nucleotidase (5?-NT) and alkaline phosphatase (AP) mediate conversion of AMP to adenosine, whereas soluble adenosine deaminase (ADA) catabolizes adenosine to inosine. Newborn blood plasma demonstrates substantially higher adenosine-generating 5?-NT and AP activity and lower adenosine-metabolizing ADA activity than adult plasma. In addition to a role in soluble purine metabolism, abundant AP expressed on the surface of circulating neonatal neutrophils is the dominant AMPase on these cells. Plasma samples from infant observational cohorts reveal a relative plasma ADA deficiency at birth, followed by a gradual maturation of plasma ADA through infancy. The robust adenosine-generating capacity of neonates appears functionally relevant because supplementation with AMP inhibited whereas selective pharmacologic inhibition of 5?-NT enhanced Toll-like receptor-mediated TNF-? production in neonatal whole blood. Overall, we have characterized previously unrecognized age-dependent expression patterns of plasma purine-metabolizing enzymes that result in elevated plasma concentrations of anti-inflammatory adenosine in newborns. Targeted manipulation of purine-metabolizing enzymes may benefit this vulnerable population. PMID:23897810

Pettengill, Matthew; Robson, Simon; Tresenriter, Megan; Millán, José Luis; Usheva, Anny; Bingham, Taiese; Belderbos, Mirjam; Bergelson, Ilana; Burl, Sarah; Kampmann, Beate; Gelinas, Laura; Kollmann, Tobias; Bont, Louis; Levy, Ofer

2013-01-01

301

Differential adenosine uptake in mixed neuronal/glial or purified glial cultures of avian retinal cells: modulation by adenosine metabolism and the ERK cascade.  

PubMed

Adenosine is an important modulator of neuronal survival and differentiation in the CNS. Our previous work showed that nucleoside transporters (NTs) are present in cultures of chick retinal cells, but little is known about the mechanisms regulating adenosine transport in these cultures. Our aim in the present work was to study the participation of the adenosine metabolism as well as the ERK pathway on adenosine uptake in different types of retinal cultures (mixed and purified glial cultures). Kinetic analysis in both cultures revealed that the uptake reached equilibrium after 30 min and presented two components. Incubation of cultures with S-(p-nitrobenzyl)-6-thioinosine (NBTI) or dipyridamole, different inhibitors of equilibrative nucleoside transporters (ENTs), produced a significant and concentration-dependent uptake reduction in both cultures. However, while dipyridamole presented similar maximal inhibitory effects in both cultures (although in different concentrations), the inhibition by NBTI was smaller in glial cultures than in mixed cultures, suggesting the presence of different transporters. Moreover, pre-incubation of [(3)H]-adenosine with adenosine deaminase (ADA) or adenosine kinase (ADK) inhibition with iodotubercidin promoted significant uptake inhibition in both cultures, indicating that the uptake is predominantly for adenosine and not inosine, and that taken up adenosine is preferentially directed to the synthesis of adenine nucleotides. In both cultures, the MEK inhibitors PD98059 or UO126, but not the inactive analog U0124, induced a significant and concentration-dependent uptake decrease. We have not observed any change in adenosine metabolism induced by MEK inhibitors, suggesting that this pathway is mediating a direct effect on NTs. Our results show the expression of different NTs in retinal cells in culture and that the activity of these transporters can be regulated by the ERK pathway or metabolic enzymes such as ADK which are then potential targets for regulation of Ado levels in normal or pathological conditions. PMID:21945936

dos Santos-Rodrigues, Alexandre; Ferreira, Jainne Martins; Paes-de-Carvalho, Roberto

2011-10-14

302

Capillary Electrophoresis in Diagnosis and Monitoring of Adenosine Deaminase Deficiency  

Microsoft Academic Search

Background: The diagnosis and monitoring of severe combined immunodeficiency disease (SCID) attribut- able to adenosine deaminase (ADA) deficiency requires measurements of ADA, purine nucleoside phosphory- lase (PNP), and S-adenosyl-L-homocysteine-hydrolase (SAHH) activity and of deoxyadenosine metabolites. We developed capillary electrophoresis (CE) methods for the detection of key diagnostic metabolites and evalua- tion of enzyme activities. Methods: Deoxyadenosine metabolites were separated in

Filippo Carlucci; Antonella Tabucchi; Alessandro Aiuti; Francesca Rosi; Federica Floccari; Roberto Pagani; Enrico Marinello

303

Gene therapy for adenosine-deaminase-deficient severe combined immunodeficiency  

Microsoft Academic Search

Adenosine-deaminase-deficient SCID was the first inherited disease to be treated with gene therapy. This life-threatening disorder is characterized by a purine defect that leads to impaired immune functions, recurrent infections and systemic metabolic abnormalities. The early gene therapy trials showed the safety and feasibility of engineering haematopoietic stem cells and peripheral blood lymphocytes using retroviral vectors. However, all patients were

Alessandro Aiuti

2004-01-01

304

Severe combined immunodeficiency due to adenosine deaminase deficiency.  

PubMed

Severe Combined Immunodeficiency is the term applied to a group of rare genetic disorders characterised by defective or absent T and B cell functions. Patients usually present in first 6 months of life with respiratory/gastrointestinal tract infections and failure to thrive. Among the various types of severe combined immunodeficiency, enzyme deficiencies are relatively less common. We report the case of a 6 years old girl having severe combined immunodeficiency due to adenosine deaminase deficiency. PMID:22764473

Hussain, Waqar; Batool, Asma; Ahmed, Tahir Aziz; Bashir, Muhammad Mukarram

2012-03-01

305

Modulation of Synapse Formation by Cyclic Adenosine Monophosphate  

Microsoft Academic Search

Synapses between neuroblastoma-hybrid cells and myotubes exhibit a high degree of plasticity. Increase of cyclic adenosine monophosphate (AMP) levels of the hybrid cells for several days results in the appearance of functional voltagesensitive Ca2+ channels, which are required for evoked secretion of acetylcholine. The results show that cyclic AMP regulates synaptogenesis by regulating the expression of voltage-sensitive Ca2+ channels, and

M. Nirenberg; S. Wilson; H. Higashida; A. Rotter; K. Krueger; N. Busis; R. Ray; J. G. Kenimer; M. Adler

1983-01-01

306

Adenosine Diphosphate as an Intracellular Regulator of Insulin Secretion  

Microsoft Academic Search

Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels couple the cellular metabolic state to electrical activity and are a critical link between blood glucose concentration and pancreatic insulin secretion. A mutation in the second nucleotide-binding fold (NBF2) of the sulfonylurea receptor (SUR) of an individual diagnosed with persistent hyperinsulinemic hypoglycemia of infancy generated KATP channels that could be opened by diazoxide but

C. G. Nichols; S.-L. Shyng; A. Nestorowicz; B. Glaser; J. P. Clement IV; G. Gonzalez; L. Aguilar-Bryan; M. A. Permutt; J. Bryan

1996-01-01

307

Hydrolysis of adenosine 5'-triphosphate: an isotope-labeling study  

Microsoft Academic Search

A combination of š⁸O-labeling experiments and kinetic studies to clarify the nonenzymatic hydrolytic pathways of adenosine 5'-triphosphate (ATP) at pH values ranging from 0 to 8.3 has been used in this experiment. In 1 N and 0.1 N HCl, the data are consistent with the hypothesis that hydrolysis occurs by addition-elimination, with initial attack 93% ..gamma.. and 7% ..beta..; both

Seymour Meyerson; E. S. Kuh; Fausto Ramirez; James F. Marecek

1982-01-01

308

The Crystal and Molecular Structure of Adenosine Triphosphate  

Microsoft Academic Search

The three-dimensional structure of the hydrated disodium salt of adenosine triphosphate (Na2ATP) has been determined from an X-ray diffraction study to a resolution of 0.9 angstrom. The crystals are orthorhombic, space group P212121, with a = 30.45(4), b = 20.88(3), c = 7.07(1) angstrom. There are two molecules of ATP, four sodium ions, and six water molecules in the asymmetric

Olga Kennard; N. W. Isaacs; W. D. S. Motherwell; J. C. Coppola; D. L. Wampler; A. C. Larson; D. G. Watson

1971-01-01

309

Attenuation of Ischemia-Induced Extracellular Adenosine Accumulation by Homocysteine  

Microsoft Academic Search

Summary: The purpose of this study was to determine the effects of homocysteine, which consumes intracellular adenosine via formation of S-adenosylhomocysteine, on interstitial fluid (ISF) adeonsine and cerebral blood flow (CBF) before, during, and after cerebral ischemia. Microdialysis probes, used to measure local CBF (H2 clearance) and to sample ISF, were implanted bilaterally into the caudate nucleus of halothane-anesthetized rats

Veronica M. Sciotti; David G. L. Van Wylen

1993-01-01

310

Adenosine: An Effective and Safe Antiarrhythmic Drug in Pediatrics  

Microsoft Academic Search

.   Adenosine is an effective, safe drug for the diagnosis and treatment of paroxysmal tachycardias in adult and pediatric patients.\\u000a A starting dose of 0.05–0.10 mg\\/kg as a rapid bolus injection is recommended for infants and children. An electrophysiologic\\u000a effect can be expected within 20 seconds after injection. Dosage may be increased up to 0.3 mg\\/kg in steps of 0.05–0.10

T. Paul; J. P. Pfammatter

1997-01-01

311

Pathophysiological roles for purines: adenosine, caffeine and urate  

PubMed Central

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

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

2011-01-01

312

Identification of widespread adenosine nucleotide binding in Mycobacterium tuberculosis  

SciTech Connect

The annotation of protein function is almost completely performed by in silico approaches. However, computational prediction of protein function is frequently incomplete and error prone. In Mycobacterium tuberculosis (Mtb), ~25% of all genes have no predicted function and are annotated as hypothetical proteins. This lack of functional information severely limits our understanding of Mtb pathogenicity. Current tools for experimental functional annotation are limited and often do not scale to entire protein families. Here, we report a generally applicable chemical biology platform to functionally annotate bacterial proteins by combining activity-based protein profiling (ABPP) and quantitative LC-MS-based proteomics. As an example of this approach for high-throughput protein functional validation and discovery, we experimentally annotate the families of ATP-binding proteins in Mtb. Our data experimentally validate prior in silico predictions of >250 ATPases and adenosine nucleotide-binding proteins, and reveal 73 hypothetical proteins as novel ATP-binding proteins. We identify adenosine cofactor interactions with many hypothetical proteins containing a diversity of unrelated sequences, providing a new and expanded view of adenosine nucleotide binding in Mtb. Furthermore, many of these hypothetical proteins are both unique to Mycobacteria and essential for infection, suggesting specialized functions in mycobacterial physiology and pathogenicity. Thus, we provide a generally applicable approach for high throughput protein function discovery and validation, and highlight several ways in which application of activity-based proteomics data can improve the quality of functional annotations to facilitate novel biological insights.

Ansong, Charles; Ortega, Corrie; Payne, Samuel H.; Haft, Daniel H.; Chauvigne-Hines, Lacie M.; Lewis, Michael P.; Ollodart, Anja R.; Purvine, Samuel O.; Shukla, Anil K.; Fortuin, Suereta; Smith, Richard D.; Adkins, Joshua N.; Grundner, Christoph; Wright, Aaron T.

2013-01-24

313

[Effects of dopamine and adenosine on regulation of water-electrolyte exchange in Amoeba proteus].  

PubMed

Dopamine and adenosine both regulate transport of sodium chloride in the renal tubules in mammals. We have studied the effect of dopamine and adenosine on spontaneous activity of contractile vacuole of Amoeba proteous. Both substances stimulated contractile vacuole. The effect of dopamine was suppressed by D2 receptor antagonist, haloperidol, but not by D1 antagonist, SCH 39166. Adenylate cyclase inhibitor, 2.5-dideoxyadenosine, suppressed the effect of dopamine, but not of adenosine. Inhibitor of protein kinase C, staurosporine, in contrast, blocked the effect of adenosine, but not dopamine. Notably, dopamine opposed effect of adenosine and vice versa. These results suggest that similar effects of dopamine and adenosine could be mediated by different intracellulare mechanisms. PMID:25509166

Bagrov, Ia Iu; Manusova, N B

2014-01-01

314

Deoxyadenosine Triphosphate as a Potentially Toxic Metabolite in Adenosine Deaminase Deficiency  

Microsoft Academic Search

The inherited deficiency of adenosine deaminase (adenosine aminohydrolase; EC 3.5.4.4) activity in humans is associated with an immunodeficiency. Some of the immunodeficient and enzyme-deficient patients respond immunologically to periodic infusions of irradiated erythrocytes containing adenosine deaminase. It has been previously reported that erythrocytes and lymphocytes from immunodeficient and enzyme-deficient children contained increased concentrations of ATP, and in the one child

Amos Cohen; Rochelle Hirschhorn; Sheldon D. Horowitz; Arieh Rubinstein; Stephen H. Polmar; Richard Hong; David W. Martin

1978-01-01

315

Action of adenosine on energetics, protein synthesis and K(+) homeostasis in teleost hepatocytes.  

PubMed

In a comparative study, we analysed the effects of adenosine on the energetics, protein synthesis and K(+ )homeostasis of hepatocytes from the anoxia-tolerant goldfish Carassius auratus and the anoxia-intolerant trout Oncorhynchus mykiss. The rate of oxygen consumption did not respond immediately to the addition of adenosine to the cells from either species, but showed a significant decrease in trout hepatocytes after 30 min. The anaerobic rate of lactate formation was not significantly affected by adenosine in goldfish hepatocytes, but was increased in trout cells. We also studied the effects of adenosine on the two most prominent ATP consumers in these cells, protein synthesis and Na(+)/K(+)-ATPase activity. Under aerobic conditions, adenosine inhibited protein synthesis of hepatocytes from goldfish by 51% and of hepatocytes from trout by 32%. During anoxia, the rate of protein synthesis decreased by approximately 50% in goldfish hepatocytes and by 90% in trout hepatocytes, and this decrease was not altered by the presence of adenosine. Adenosine inhibited normoxic Na(+)/K(+)-ATPase activity and K(+ )efflux by 20-35% in the cells of both species. An investigation into the mechanism underlying the inhibition of protein synthesis by adenosine indicated that, in the goldfish cells, adenosine acts via a membrane receptor-mediated pathway, i.e. the effect of adenosine was abolished by applying the A1 receptor antagonist 8-phenyltheophylline. In the trout, however, the uptake of adenosine into hepatocytes seems to be required for an effect on protein synthesis. [Ca(2+)](i) does not seem to be involved in the inhibition of protein synthesis by adenosine. PMID:10934006

Krumschnabel, G; Biasi, C; Wieser, W

2000-09-01

316

PAP and NT5E inhibit nociceptive neurotransmission by rapidly hydrolyzing nucleotides to adenosine  

PubMed Central

Background Prostatic acid phosphatase (PAP) and ecto-5'-nucleotidase (NT5E, CD73) produce extracellular adenosine from the nucleotide AMP in spinal nociceptive (pain-sensing) circuits; however, it is currently unknown if these are the main ectonucleotidases that generate adenosine or how rapidly they generate adenosine. Results We found that AMP hydrolysis, when measured histochemically, was nearly abolished in dorsal root ganglia (DRG) neurons and lamina II of spinal cord from Pap/Nt5e double knockout (dKO) mice. Likewise, the antinociceptive effects of AMP, when combined with nucleoside transport inhibitors (dipyridamole or 5-iodotubericidin), were reduced by 80-100% in dKO mice. In addition, we used fast scan cyclic voltammetry (FSCV) to measure adenosine production at subsecond resolution within lamina II. Adenosine was maximally produced within seconds from AMP in wild-type (WT) mice but production was reduced >50% in dKO mice, indicating PAP and NT5E rapidly generate adenosine in lamina II. Unexpectedly, we also detected spontaneous low frequency adenosine transients in lamina II with FSCV. Adenosine transients were of short duration (<2 s) and were reduced (>60%) in frequency in Pap-/-, Nt5e-/- and dKO mice, suggesting these ectonucleotidases rapidly hydrolyze endogenously released nucleotides to adenosine. Field potential recordings in lamina II and behavioral studies indicate that adenosine made by these enzymes acts through the adenosine A1 receptor to inhibit excitatory neurotransmission and nociception. Conclusions Collectively, our experiments indicate that PAP and NT5E are the main ectonucleotidases that generate adenosine in nociceptive circuits and indicate these enzymes transform pulsatile or sustained nucleotide release into an inhibitory adenosinergic signal. PMID:22011440

2011-01-01

317

Adenosine-induced bronchoconstriction of isolated lung and trachea from sensitized guinea-pigs.  

PubMed Central

1. The bronchoconstriction of airway-perfused lungs and contraction of superfused tracheal spirals from guinea-pigs in response to adenosine were examined. 2. In lungs from untreated animals, adenosine had little effect unless the perfusion pressure was raised with carbachol (1.1 microM), when it caused a fall in perfusion pressure. However, if removed from guinea-pigs sensitized with ovalbumin (5 mg and 10 mg i.p. 14 and 12 days before use), adenosine was bronchoconstrictor, exerting bronchodilator effects only at high (1 mg) doses. The constrictor response to adenosine (300 micrograms) was significantly greater than that in lungs from untreated or sham-injected animals. 3. In superfused trachea from untreated animals, adenosine exerted only relaxant responses. In tissues from ovalbumin-sensitized guinea-pigs adenosine produced contractile responses, with relaxation appearing only at high (1 mg) doses. 4. Thus sensitization by antigen challenge revealed a bronchoconstrictor response of isolated airway preparations to adenosine. This is related to the clinical situation where only asthmatic subjects respond to adenosine by bronchoconstriction and suggests that the sensitization may destabilize inflammatory cells for mediator release by adenosine. 5. The response to a second exposure to adenosine was consistently reduced (lungs) or converted to a relaxation (trachea) indicating tachyphylaxis and consistent with a mediator release mechanism. 6. The P1-purinoceptor antagonist, 8-phenyltheophylline (3.9 microM), antagonized the relaxant responses to higher doses of adenosine. However, it did not affect the contractile responses to lower doses of adenosine.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1393296

Thorne, J. R.; Broadley, K. J.

1992-01-01

318

Adenosine A 1 receptor antagonist versus montelukast on airway reactivity and inflammation  

Microsoft Academic Search

Adenosine produces bronchoconstriction in allergic rabbits, primates, and humans by activating adenosine A1 receptors. Previously, it is reported that a high dose of L-97-1, a water-soluble, small molecule adenosine A1 receptor antagonist, blocks early and late allergic responses, and bronchial hyper-responsiveness to histamine in a hyper-responsive rabbit model of allergic asthma. Effects of a lower dose of L-97-1 are compared

Ahmed Nadeem; Peter C. M. Obiefuna; Constance N. Wilson; S. Jamal Mustafa

2006-01-01

319

Increase in plasma free fatty acids and natriuresis by xanthines may reflect adenosine antagonism  

Microsoft Academic Search

The hypothesis has been examined that adenosine is involved in the diuretic and free fatty acid (FFA) — releasing action of xanthines. The effects of theophylline (T), a potent adenosine antagonist, were compared with those of enprofylline (3-propyl xanthine, E), which exerts negligible antagonism of adenosine. Eight healthy male volunteers were given E 1.5 mg\\/kg, T 5.0mg\\/kg or placebo 0.9%

K.-E. Andersson; N. Johannesson; B. Karlberg; C. G. A. Persson

1984-01-01

320

Caffeine Acts via A1 Adenosine Receptors to Disrupt Embryonic Cardiac Function  

Microsoft Academic Search

BackgroundEvidence suggests that adenosine acts via cardiac A1 adenosine receptors (A1ARs) to protect embryos against hypoxia. During embryogenesis, A1ARs are the dominant regulator of heart rate, and A1AR activation reduces heart rate. Adenosine action is inhibited by caffeine, which is widely consumed during pregnancy. In this study, we tested the hypothesis that caffeine influences developing embryos by altering cardiac function.Methodology\\/Principal

Daniela L. Buscariollo; Gregory A. Breuer; Christopher C. Wendler; Scott A. Rivkees

2011-01-01

321

Identification and Characterization of a Unique Adenosine Kinase from Mycobacterium tuberculosis  

Microsoft Academic Search

Adenosine kinase (AK) is a purine salvage enzyme that catalyzes the phosphorylation of adenosine to AMP. In Mycobacterium tuberculosis, AK can also catalyze the phosphorylation of the adenosine analog 2-methylad- enosine (methyl-Ado), the first step in the metabolism of this compound to an active form. Purification of AK from M. tuberculosis yielded a 35-kDa protein that existed as a dimer

Mary C. Long; Vincent Escuyer; William B. Parker

2003-01-01

322

Adenosine A2A receptors play a role in the pathogenesis of hepatic cirrhosis  

PubMed Central

Adenosine is a potent endogenous regulator of inflammation and tissue repair. Adenosine, which is released from injured and hypoxic tissue or in response to toxins and medications, may induce pulmonary fibrosis in mice, presumably via interaction with a specific adenosine receptor. We therefore determined whether adenosine and its receptors contribute to the pathogenesis of hepatic fibrosis. As in other tissues and cell types, adenosine is released in vitro in response to the fibrogenic stimuli ethanol (40?mg?dl?1) and methotrexate (100?nM). Adenosine A2A receptors are expressed on rat and human hepatic stellate cell lines and adenosine A2A receptor occupancy promotes collagen production by these cells. Liver sections from mice treated with the hepatotoxins carbon tetrachloride (CCl4) (0.05?ml in oil, 50?:?50 v?:?v, subcutaneously) and thioacetamide (100?mg?kg?1 in PBS, intraperitoneally) released more adenosine than those from untreated mice when cultured ex vivo. Adenosine A2A receptor-deficient, but not wild-type or A3 receptor-deficient, mice are protected from development of hepatic fibrosis following CCl4 or thioacetamide exposure. Similarly, caffeine (50?mg?kg?1?day?1, po), a nonselective adenosine receptor antagonist, and ZM241385 (25?mg?kg?1 bid), a more selective antagonist of the adenosine A2A receptor, diminished hepatic fibrosis in wild-type mice exposed to either CCl4 or thioacetamide. These results demonstrate that hepatic adenosine A2A receptors play an active role in the pathogenesis of hepatic fibrosis, and suggest a novel therapeutic target in the treatment and prevention of hepatic cirrhosis. PMID:16783407

Chan, Edwin S L; Montesinos, Maria Carmen; Fernandez, Patricia; Desai, Avani; Delano, David L; Yee, Herman; Reiss, Allison B; Pillinger, Michael H; Chen, Jiang-Fan; Schwarzschild, Michael A; Friedman, Scott L; Cronstein, Bruce N

2006-01-01

323

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

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

324

Characterization of adenosine receptors on rat ileum, ileal longitudinal muscle and muscularis mucosae  

Microsoft Academic Search

Adenosine receptors were studied in isolated rat ileum, ileal longitudinal muscle and muscularis mucosae, using a range of agonists and an antagonist. In the rat ileal longitudinal muscle adenosine receptor agonists relaxed the tissues. N6-cyclopentyladenosine (CPA) was more potent than 5?-N-ethylcarboxamidoadenosine (NECA) or adenosine and 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) (1 nM) gave a 5-fold parallel shift to the right of the concentration–response

Julia Nicholls; Susanna M. O Hourani

1997-01-01

325

John Montgomery's Legacy: Carbocyclic Adenosine Analogues as Sah Hydrolase Inhibitors with Broad-Spectrum Antiviral Activity  

Microsoft Academic Search

Ever since the S-adenosylhomocysteine (AdoHcy, SAH) hydrolase was recognized as a pharmacological target for antiviral agents (J. A. Montgomery et al., J. Med. Chem. 25:626–629, 1982), an increasing number of adenosine, acyclic adenosine, and carbocyclic adenosine analogues have been described as potent SAH hydrolase inhibitors endowed with broad-spectrum antiviral activity. The antiviral activity spectrum of the SAH hydrolase inhibitors include

E. De Clercq

2005-01-01

326

NAD(P)H oxidase activity in cultured human podocytes: Effects of adenosine triphosphate  

Microsoft Academic Search

NAD(P)H oxidase activity in cultured human podocytes: Effects of adenosine triphosphate. Reactive oxygen species contribute to glomerular damage and proteinuria. In this study, we show that cultured human podocytes produce superoxide in response to extracellular adenosine triphosphate (ATP), and we identified the oxidases involved in this process. Adenosine triphosphate (10?4 M for 4 hr) raised superoxide production from 1.28 ą

Stefan Greiber; Thomas Münzel; Stefanie Kästner; Barbara Müller; Peter Schollmeyer; Hermann Pavenstädt

1998-01-01

327

Adenosine as an adjunct to thrombolytic therapy for acute myocardial infarction  

Microsoft Academic Search

OBJECTIVESThe Acute Myocardial Infarction STudy of ADenosine (AMISTAD) trial was designed to test the hypothesis that adenosine as an adjunct to thrombolysis would reduce myocardial infarct size.BACKGROUNDReperfusion therapy for acute myocardial infarction (MI) has been shown to reduce mortality, but reperfusion itself also may have deleterious effects.METHODSThe AMISTAD trial was a prospective, open-label trial of thrombolysis with randomization to adenosine

Kenneth W Mahaffey; Joseph A Puma; N. Alejandro Barbagelata; Marcelo F DiCarli; Massoud A Leesar; Kevin F Browne; Paul R Eisenberg; Roberto Bolli; A. Cecilia Casas; Victor Molina-Viamonte; Cesare Orlandi; Roger Blevins; Raymond J Gibbons; Robert M Califf; Christopher B Granger

1999-01-01

328

Adenosine levels in serum and adenosine deaminase activity in blood cells of dogs infected by Rangelia vitalii.  

PubMed

Ecto-adenosinedeaminase (E-ADA) plays an important role in the production and differentiation of blood cells as well as in the control of extracellular adenosine levels. Infectious diseases can influence the synthesis of new cells or cause cell destruction, as occurs in canine rangeliosis, which results in anemia, thrombocytopenia, leukocytosis, and/or leukopenia. Thus, this study aimed to evaluate E-ADA activity in sera, erythrocytes, lymphocytes, and adenosine levels in sera samples of dogs infected by Rangelia vitalii. Twelve animals were divided into 2 groups: noninfected (n = 5) and infected by R. vitalii (n = 7). Animals were infected with 2 ml of blood containing the parasite, and parasitemia was estimated daily for 20 days by microscopic examination of peripheral blood smears. Blood collection was performed on days 0, 10, and 20 post-infection (PI) in order to evaluate the evolution of the disease. The blood collected was used to assess the activity of E-ADA. We observed an increase of E-ADA activity in sera (day 20 PI) and erythrocytes (days 10 and 20 PI) in the infected group (P < 0.05). E-ADA activity in lymphocytes was decreased on day 10, when the parasitemia was high, and increased after 20 days, when the number of circulating parasites was low. HPLC measured adenosine levels in the serum and found a reduction on days 10 and 20 PI. In conclusion, our results showed that E-ADA activity was altered in sera, lymphocytes, and erythrocytes of dogs experimentally infected by R. vitalii as well as the serum concentration of adenosine. These alterations may contribute to the pathogenesis of anemia and immune response in infected dogs. PMID:23777319

Da Silva, Aleksandro S; França, Raqueli T; Costa, Marcio M; Paim, Francine C; Pimentel, Victor C; Schmatz, Roberta; Jaques, Jeandre A; Schetinger, Maria R C; Mazzanti, Cinthia M; Tonin, Alexandre A; Monteiro, Silvia G; Lopes, Sonia T A

2013-12-01

329

Novel thiazole-thiophene conjugates as adenosine receptor antagonists: Synthesis, biological evaluation and docking studies.  

PubMed

Here we report novel thiazole-thiophene conjugates as adenosine receptor antagonists. All the molecules were evaluated for their binding affinity for adenosine receptors. Most of the molecules were found to interact with the A1, A2A and A3 adenosine receptor subtypes with good affinity values. The most potent and selective compound 8n showed an A3Ki value of 0.33?M with selectivity ratios of >90 versus the A1 and >30 versus the A2 subtypes. For compound 8n docking studies into the binding site of the A3 adenosine receptor are provided to visualize its binding mode. PMID:25686851

Pandya, Dhaivat H; Sharma, Jayesh A; Jalani, Hitesh B; Pandya, Amit N; Sudarsanam, V; Kachler, Sonja; Klotz, Karl Norbert; Vasu, Kamala K

2015-03-15

330

A rapid enzymatic assay for high-throughput screening of adenosine-producing strains  

PubMed Central

Adenosine is a major local regulator of tissue function and industrially useful as precursor for the production of medicinal nucleoside substances. High-throughput screening of adenosine overproducers is important for industrial microorganism breeding. An enzymatic assay of adenosine was developed by combined adenosine deaminase (ADA) with indophenol method. The ADA catalyzes the cleavage of adenosine to inosine and NH3, the latter can be accurately determined by indophenol method. The assay system was optimized to deliver a good performance and could tolerate the addition of inorganic salts and many nutrition components to the assay mixtures. Adenosine could be accurately determined by this assay using 96-well microplates. Spike and recovery tests showed that this assay can accurately and reproducibly determine increases in adenosine in fermentation broth without any pretreatment to remove proteins and potentially interfering low-molecular-weight molecules. This assay was also applied to high-throughput screening for high adenosine-producing strains. The high selectivity and accuracy of the ADA assay provides rapid and high-throughput analysis of adenosine in large numbers of samples. PMID:25580842

Dong, Huina; Zu, Xin; Zheng, Ping; Zhang, Dawei

2015-01-01

331

Characterization and regulation of adenosine transport in T84 intestinal epithelial cells.  

PubMed

Adenosine release from mucosal sources during inflammation and ischemia activates intestinal epithelial Cl- secretion. Previous data suggest that A2b receptor-mediated Cl- secretory responses may be dampened by epithelial cell nucleoside scavenging. The present study utilizes isotopic flux analysis and nucleoside analog binding assays to directly characterize the nucleoside transport system of cultured T84 human intestinal epithelial cells and to explore whether adenosine transport is regulated by secretory agonists, metabolic inhibition, or phorbol ester. Uptake of adenosine across the apical membrane displayed characteristics of simple diffusion. Kinetic analysis of basolateral uptake revealed a Na(+)-independent, nitrobenzylthioinosine (NBTI)-sensitive facilitated-diffusion system with low affinity but high capacity for adenosine. NBTI binding studies indicated a single population of high-affinity binding sites basolaterally. Neither forskolin, 5'-(N-ethylcarboxamido)-adenosine, nor metabolic inhibition significantly altered adenosine transport. However, phorbol 12-myristate 13-acetate significantly reduced both adenosine transport and the number of specific NBTI binding sites, suggesting that transporter number may be decreased through activation of protein kinase C. This basolateral facilitated adenosine transporter may serve a conventional function in nucleoside salvage and a novel function as a regulator of adenosine-dependent Cl- secretory responses and hence diarrheal disorders. PMID:9486178

Mun, E C; Tally, K J; Matthews, J B

1998-02-01

332

Modulation of adenosine signaling prevents scopolamine-induced cognitive impairment in zebrafish.  

PubMed

Adenosine, a purine ribonucleoside, exhibits neuromodulatory and neuroprotective effects in the brain and is involved in memory formation and cognitive function. Adenosine signaling is mediated by adenosine receptors (A1, A2A, A2B, and A3); in turn, nucleotide and nucleoside-metabolizing enzymes and adenosine transporters regulate its levels. Scopolamine, a muscarinic cholinergic receptor antagonist, has profound amnesic effects in a variety of learning paradigms and has been used to induce cognitive deficits in animal models. This study investigated the effects of acute exposure to caffeine (a non-selective antagonist of adenosine receptors A1 and A2A), ZM 241385 (adenosine receptor A2A antagonist), DPCPX (adenosine receptor A1 antagonist), dipyridamole (inhibitor of nucleoside transporters) and EHNA (inhibitor of adenosine deaminase) in a model of pharmacological cognitive impairment induced by scopolamine in adult zebrafish. Caffeine, ZM 241385, DPCPX, dipyridamole, and EHNA were acutely administered independently via i.p. in zebrafish, followed by exposure to scopolamine dissolved in tank water (200?M). These compounds prevented the scopolamine-induced amnesia without impacting locomotor activity or social interaction. Together, these data support the hypothesis that adenosine signaling may modulate memory processing, suggesting that these compounds present a potential preventive strategy against cognitive impairment. PMID:25490060

Bortolotto, Josiane Woutheres; de Melo, Gabriela Madalena; Cognato, Giana de Paula; Vianna, Mônica Ryff Moreira; Bonan, Carla Denise

2015-02-01

333

Adenosine deaminase deficiency with normal immune function. An acidic enzyme mutation.  

PubMed Central

In most instances, marked deficiency of the purine catabolic enzyme adenosine deaminase results in lymphopenia and severe combined immunodeficiency disease. Over a 2-yr period, we studied a white male child with markedly deficient erythrocyte and lymphocyte adenosine deaminase activity and normal immune function. We have documented that (a) adenosine deaminase activity and immunoreactive protein are undetectable in erythrocytes, 0.9% of normal in lymphocytes, 4% in cultured lymphoblasts, and 14% in skin fibroblasts; (b) plasma adenosine and deoxyadenosine levels are undetectable and deoxy ATP levels are only slightly elevated in lymphocytes and in erythrocytes; (c) no defect in deoxyadenosine metabolism is present in the proband's cultured lymphoblasts; (d) lymphoblast adenosine deaminase has normal enzyme kinetics, absolute specific activity, S20,w, pH optimum, and heat stability; and (e) the proband's adenosine deaminase exhibits a normal apparent subunit molecular weight but an abnormal isoelectric pH. In contrast to the three other adenosine deaminase-deficient healthy subjects who have been described, the proband is unique in demonstrating an acidic, heat-stable protein mutation of the enzyme that is associated with less than 1% lymphocyte adenosine deaminase activity. Residual adenosine deaminase activity in tissues other than lymphocytes may suffice to metabolize the otherwise lymphotoxic enzyme substrate(s) and account for the preservation of normal immune function. Images FIGURE 1 FIGURE 2 FIGURE 3 PMID:6603477

Daddona, P E; Mitchell, B S; Meuwissen, H J; Davidson, B L; Wilson, J M; Koller, C A

1983-01-01

334

The role of adenosine receptors in the central action of caffeine  

PubMed Central

The behavioral effects of caffeine appear likely to be due in large measure to antagonism of the action of endogenous adenosine at A1- and A2a-receptors in the central nervous system. Other biochemical mechanisms of action of caffeine, such as release of intracellular calcium, inhibition of phosphodiesterases and blockade of regulatory sites of GABAA-reccptors, would require much higher concentrations than the micromolar concentrations of caffeine associated with behavioral stimulation. However, micromolar concentrations of caffeine also would be expected to cause only a modest blockade of adenosine receptors. Selective adenosine agonists and xanthine antagonists have provided some insights into central roles for adenosine receptor subtypes. Thus, behavioral stimulation by xanthines appears to require blockade of both A1- and A2a-receptors. Chronic blockade of adenosine receptors by caffeine would be expected to result in alterations in the central receptors and pathways that are regulated by adenosine through A1- and A2a-receptors. Indeed, chronic caffeine docs alter the density not only of adenosine receptors, but also of adrenergic, cholinergic, GABAergic and serotonergic receptors. Behavioral responses to agents acting through dopaminergic and cholinergic pathways arc altered. As yet, a coherent explanation of the acute and chronic effects of caffeine in terms of blockade of adenosine receptors has not emerged. Interactions between pathways subserved by A1 - and A2a-adcnosine receptors complicate attempts to interpret caffeine pharmacology, as does the complex control by adenosine receptors of dopamincrgic, cholinergic and other central pathways.

Daly, John W.; Shi, Dan; Nikodijevic, Olga; Jacobson, Kenneth A.

2013-01-01

335

Adenosine and Glutamate Signaling in Neuron-Glial interactions: Implications in Alcoholism and Sleep Disorders  

PubMed Central

Recent studies have demonstrated that the function of glia is not restricted to the support of neuronal function. Especially, astrocytes are essential for neuronal activity in the brain. Astrocytes actively participate in synapse formation and brain information processing by releasing or uptaking gliotransmitters such as glutamate, D-serine, adenosine 5?-triphosphate (ATP) and adenosine. In the central nervous system, adenosine plays an important role in regulating neuronal activity as well as in controlling other neurotransmitter systems such as GABA, glutamate and dopamine. Ethanol increases extracellular adenosine levels, which regulates the ataxic and hypnotic/sedative (somnogenic) effects of ethanol. Adenosine signaling is also involved in the homeostasis of major inhibitory-excitatory neurotransmission (i.e. GABA or glutamate) through neuron-glial interactions, which regulates the effect of ethanol and sleep. Adenosine transporters or astrocytic SNARE-mediated transmitter release regulates extracellular or synaptic adenosine levels. Adenosine then exerts its function through several adenosine receptors and regulates glutamate levels in the brain. This review presents novel findings on how neuron-glial interactions, particularly adenosinergic signaling and glutamate uptake activity involving glutamate transporter 1 (GLT1), are implicated in alcoholism and sleep disorders. PMID:22309182

Nam, Hyung Wook; McIver, Sally R.; Hinton, David J.; Thakkar, Mahesh M.; Sari, Youssef; Parkinson, Fiona E.; Haydon, Phillip G.; Choi, Doo-Sup

2012-01-01

336

Adenosine receptor blockade augments interstitial fluid levels of excitatory amino acids during cerebral ischemia.  

PubMed

The excitotoxic hypothesis suggests that cerebral ischemic damage results in part from the accumulation of the excitatory and potentially toxic neurotransmitters glutamate and aspartate. Adenosine, which also increases during cerebral ischemia, is proposed to inhibit neurotransmitter release. The purpose of this study was to determine if adenosine receptor blockade exacerbates the accumulation of glutamate and aspartate during cerebral ischemia. Microdialysis probes, implanted bilaterally in the caudate nucleus of halothane-anesthetized rats, were used to (1) assess changes in interstitial fluid (ISF) glutamate, aspartate, adenosine, and adenosine metabolites; (2) measure local cerebral blood flow (H2 clearance); and (3) deliver 8-(p-sulfophenyl)theophylline (SPT), an adenosine receptor antagonist, locally to the brain. The probe on one side of the brain was perfused with artificial cerebrospinal fluid (CSF) containing 10(-3) M SPT, while the probe on the opposite side received only artificial CSF. Animals were exposed to 20 min of ischemia (carotid occlusion+arterial blood pressure = 50 mm Hg) followed by 60 min of reperfusion. Dialysate glutamate and aspartate increased during and after cerebral ischemia, but were increased to a greater extent in the presence of adenosine receptor blockade. Likewise, the increase in dialysate adenosine and adenosine metabolites was enhanced on the side of locally administered SPT. These data suggest that endogenous adenosine attenuates the accumulation of glutamate and aspartate during cerebral ischemia. PMID:1352304

Sciotti, V M; Roche, F M; Grabb, M C; Van Wylen, D G

1992-07-01

337

Insulin resistance and vasodilation in essential hypertension. Studies with adenosine.  

PubMed Central

Insulin-mediated vasodilation has been proposed as a determinant of in vivo insulin sensitivity. We tested whether sustained vasodilation with adenosine could overcome the muscle insulin resistance present in mildly overweight patients with essential hypertension. Using the forearm technique, we measured the response to a 40-min local intraarterial infusion of adenosine given under fasting conditions (n = 6) or superimposed on a euglycemic insulin clamp (n = 8). In the fasting state, adenosine-induced vasodilation (forearm blood flow from 2.6 +/- 0.6 to 6.0 +/- 1.2 ml min-1dl-1, P < 0.001) was associated with a 45% rise in muscle oxygen consumption (5.9 +/- 1.0 vs 8.6 +/- 1.7 mumol min-1dl-1, P < 0.05), and a doubling of forearm glucose uptake (0.47 +/- 0.15 to 1.01 +/- 0.28 mumol min-1dl-1, P < 0.05). The latter effect remained significant also when expressed as a ratio to concomitant oxygen balance (0.08 +/- 0.03 vs 0.13 +/- 0.04 mumol mumol-1, P < 0.05), whereas for all other metabolites (lactate, pyruvate, FFA, glycerol, citrate, and beta-hydroxybutyrate) this ratio remained unchanged. During euglycemic hyperinsulinemia, whole-body glucose disposal was stimulated (to 19 +/- 3 mumol min-1kg-1), but forearm blood flow did not increase significantly above baseline (2.9 +/- 0.2 vs 3.1 +/- 0.2 ml min-1dl-1, P = NS). Forearm oxygen balance increased (by 30%, P < 0.05) and forearm glucose uptake rose fourfold (from 0.5 to 2.3 mumol min-1dl-1, P < 0.05). Superimposing an adenosine infusion into one forearm resulted in a 100% increase in blood flow (from 2.9 +/- 0.2 to 6.1 +/- 0.9 ml min-1dl-1, P < 0.001); there was, however, no further stimulation of oxygen or glucose uptake compared with the control forearm. During the clamp, the ratio of glucose to oxygen uptake was similar in the control and in the infused forearms (0.27 +/- 0.11 and 0.23 +/- 0.09, respectively), and was not altered by adenosine (0.31 +/- 0.9 and 0.29 +/- 0.10). We conclude that in insulin-re15-76sistant patients with hypertension, adenosine-induced vasodilation recruits oxidative muscle tissues and exerts a modest, direct metabolic effect to promote muscle glucose uptake in the fasting state. Despite these effects, however, adenosine does not overcome muscle insulin resistance. Images PMID:7929833

Natali, A; Bonadonna, R; Santoro, D; Galvan, A Q; Baldi, S; Frascerra, S; Palombo, C; Ghione, S; Ferrannini, E

1994-01-01

338

IL-4 Amplifies the Pro-Inflammatory Effect of Adenosine in Human Mast Cells by Changing Expression Levels of Adenosine Receptors  

PubMed Central

Adenosine inhalation produces immediate bronchoconstriction in asthmatics but not in normal subjects. The bronchospastic effect of adenosine is largely mediated through adenosine-induced mast cell activation, the mechanism of which is poorly understood due to limitations in culturing human primary mast cells. Here, we show that human umbilical cord blood -derived mast cells incubated with the Th2 cytokine IL-4 develop increased sensitivity to adenosine. Potentiation of anti-IgE- induced and calcium ionophore/PMA-induced degranulation was augmented in mast cells cultured with IL-4, and this effect was reduced or abolished by pre-treatment with A2BsiRNA and selective A2B receptor antagonists, respectively. IL-4 incubation resulted in the increased expression of A2B and reduced expression of A2A adenosine receptors on human mast cells. These results suggest that Th2 cytokines in the asthmatic lung may alter adenosine receptor expression on airway mast cells to promote increased responsiveness to adenosine. PMID:21966389

Hua, Xiaoyang; Chason, Kelly D.; Patel, Janki Y.; Naselsky, Warren C.; Tilley, Stephen L.

2011-01-01

339

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

PubMed Central

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

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

2003-01-01

340

Activity-Dependent Adenosine Release May Be Linked to Activation of Na+-K+ ATPase: An In Vitro Rat Study  

PubMed Central

In the brain, extracellular adenosine increases as a result of neuronal activity. The mechanisms by which this occurs are only incompletely understood. Here we investigate the hypothesis that the Na+ influxes associated with neuronal signalling activate the Na+-K+ ATPase which, by consuming ATP, generates intracellular adenosine that is then released via transporters. By measuring adenosine release directly with microelectrode biosensors, we have demonstrated that AMPA-receptor evoked adenosine release in basal forebrain and cortex depends on extracellular Na+. We have simultaneously imaged intracellular Na+ and measured adenosine release. The accumulation of intracellular Na+ during AMPA receptor activation preceded adenosine release by some 90 s. By removing extracellular Ca2+, and thus preventing indiscriminate neuronal activation, we used ouabain to test the role of the Na+-K+ ATPase in the release of adenosine. Under conditions which caused a Na+ influx, brief applications of ouabain increased the accumulation of intracellular Na+ but conversely rapidly reduced extracellular adenosine levels. In addition, ouabain greatly reduced the amount of adenosine released during application of AMPA. Our data therefore suggest that activity of the Na+-K+ ATPase is directly linked to the efflux of adenosine and could provide a universal mechanism that couples adenosine release to neuronal activity. The Na+-K+ ATPase-dependent adenosine efflux is likely to provide adenosine-mediated activity-dependent negative feedback that will be important in many diverse functional contexts including the regulation of sleep. PMID:24489921

Sims, Robert Edward; Dale, Nicholas

2014-01-01

341

Adenosine analogs inhibit adipocyte adenylate cyclase by a GTP-dependent process: basis for actions of adenosine and methylxanthines on cyclic AMP production and lipolysis.  

PubMed Central

Adenylate cyclase in purified membranes from rat adipocytes is inhibited by low concentrations of purine-modified adenosine analogs, particularly those modified in the N6 position. Such inhibition is antagonized competitively by methylxanthines, but not by other cyclic nucleotide phosphodiesterase inhibitors, and it is dependent on "inhibitory" concentrations of GTP in the assay medium. Ribose-modified adenosine analogs inhibit adenylate cyclase through a process that is neither dependent upon the GTP concentration nor antagonized by methylxanthines. These results explain the potent effects of adenosine and methylxanthines on fat cell metabolism and demonstrate the importance of GTP in mediating inhibition by agents that act at cell surface receptors. PMID:214785

Londos, C; Cooper, D M; Schlegel, W; Rodbell, M

1978-01-01

342

Characterization of the adenosine receptors of the rat superior cervical ganglion.  

PubMed Central

1. Adenosine analogues caused hyperpolarization and inhibition of the depolarizing response to muscarine of the rat isolated superior cervical ganglion (SCG) measured by a 'grease gap' recording technique. The receptors mediating these responses have been characterized by use of a range of selective adenosine analogues and adenosine receptor antagonists. 2. In decreasing order of potency N6-cyclopentyladenosine (CPA), 2-chloroadenosine (2CA), adenosine, 2-phenylaminoadenosine (PAA), caused concentration-dependent hyperpolarizations whilst N6-(9-fluorenylmethyl)adenosine (PD 117,413) was inactive at up to 100 microM. 3. The order of potency of adenosine analogues in depressing depolarization caused by a submaximal concentration of muscarine (100 nM) was: CPA > R-PIA = 2CA > NECA > S-PIA > BZA > adenosine > PAA, where R- and S-PIA = R(-)- and S(+)-N6-(2-phenylisopropyl)adenosine, NECA = 5'N-ethylcarboxamidoadenosine and BZA = N6-benzyladenosine. PD 117,413 was inactive at concentrations up to 100 microM. The maximum inhibitions of the muscarine-induced depolarization by CPA, 2CA, NECA and BZA were similar. R-PIA, S-PIA and PAA produced similar maximal inhibitions which were significantly smaller than those produced by CPA. 4. Hyperpolarizations caused by adenosine were antagonized by the P1-purinoceptor selective antagonist 1,3-dimethyl-8-phenylxanthine (8PT) and by the selective A1-adenosine receptor antagonist, 1,3-dipropyl-8-(4-((2-aminoethyl)amino)carbonylmethyloxyphenyl++ +)xanthine (XAC). Hyperpolarizations caused by CPA, adenosine and PAA were antagonized by the A1-selective antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) but not by the A2-selective antagonist, 3,7-dimethyl-1-propargylxanthine (DMPX).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8242261

Connolly, G. P.; Stone, T. W.; Brown, F.

1993-01-01

343

Suppression of kindling epileptogenesis by adenosine releasing stem cell-derived brain implants.  

PubMed

Epilepsy therapy is largely symptomatic and no effective therapy is available to prevent epileptogenesis. We therefore analysed the potential of stem cell-derived brain implants and of paracrine adenosine release to suppress the progressive development of seizures in the rat kindling-model. Embryonic stem (ES) cells, engineered to release the inhibitory neuromodulator adenosine by biallelic genetic disruption of the adenosine kinase gene (Adk-/-), and respective wild-type (wt) cells, were differentiated into neural precursor cells (NPs) and injected into the hippocampus of rats prior to kindling. Therapeutic effects of NP-derived brain implants were compared with those of wt baby hamster kidney cells (BHK) and adenosine releasing BHK cell implants (BHK-AK2), which were previously shown to suppress seizures by paracrine adenosine release. Wild-type NP-graft recipients were characterized by an initial delay of seizure development, while recipients of adenosine releasing NPs displayed sustained protection from developing generalized seizures. In contrast, recipients of wt BHK cells failed to display any effects on kindling development, while recipients of BHK-AK2 cells were only moderately protected from seizure development. The therapeutic effect of Adk(-/-)-NPs was due to graft-mediated adenosine release, since seizures could transiently be provoked after blocking adenosine A1 receptors. Histological analysis of NP-implants at day 26 revealed cell clusters within the infrahippocampal cleft as well as intrahippocampal location of graft-derived cells expressing mature neuronal markers. In contrast, BHK and BHK-AK2 cell implants only formed cell clusters within the infrahippocampal cleft. We conclude that ES cell-derived adenosine releasing brain implants are superior to paracrine adenosine release from BHK-AK2 cell implants in suppressing seizure progression in the rat kindling-model. These findings may indicate a potential antiepileptogenic function of stem cell-mediated adenosine delivery. PMID:17472985

Li, Tianfu; Steinbeck, Julius A; Lusardi, Theresa; Koch, Philipp; Lan, Jing Q; Wilz, Andrew; Segschneider, Michaela; Simon, Roger P; Brüstle, Oliver; Boison, Detlev

2007-05-01

344

Adenosine signaling contributes to ethanol-induced fatty liver in mice  

PubMed Central

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

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

2009-01-01

345

75 FR 8981 - Prospective Grant of Exclusive License: Treatment of Glaucoma by Administration of Adenosine A3...  

Federal Register 2010, 2011, 2012, 2013, 2014

...benzopyran one-, and triazoloquinazoline derivatives, their preparation and use as adenosine...benzopyran one-, and triazoloquinazoline derivatives, their preparation and use as adenosine...benzopyran one-, and triazoloquinazoline derivatives, their preparation and use as...

2010-02-26

346

Bone marrow transplantation and alternatives for adenosine deaminase deficiency.  

PubMed

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

Gaspar, H Bobby

2010-05-01

347

The Role of Uridine Adenosine Tetraphosphate in the Vascular System  

PubMed Central

The endothelium plays a pivotal role in vascular homeostasis, and endothelial dysfunction is a major feature of cardiovascular diseases, such as arterial hypertension, atherosclerosis, and diabetes. Recently, uridine adenosine tetraphosphate (Up4A) has been identified as a novel and potent endothelium-derived contracting factor (EDCF). Up4A structurally contains both purine and pyrimidine moieties, which activate purinergic receptors. There is an accumulating body of evidence to show that Up4A modulates vascular function by actions on endothelial and smooth muscle cells. In this paper, we discuss the effects of Up4A on vascular function and a potential role for Up4A in cardiovascular diseases. PMID:22110488

Matsumoto, Takayuki; Tostes, Rita C.; Webb, R. Clinton

2011-01-01

348

Adenosine triphosphatases of thermophilic archaeal double-stranded DNA viruses  

PubMed Central

Adenosine triphosphatases (ATPases) of double-stranded (ds) DNA archaeal viruses are structurally related to the AAA+?hexameric helicases and translocases. These ATPases have been implicated in viral life cycle functions such as DNA entry into the host, and viral genome packaging into preformed procapsids. We summarize bioinformatical analyses of a wide range of archaeal ATPases, and review the biochemical and structural properties of those archaeal ATPases that have measurable ATPase activity. We discuss their potential roles in genome delivery into the host, virus assembly and genome packaging in comparison to hexameric helicases and packaging motors from bacteriophages. PMID:25105011

2014-01-01

349

Adenosine triphosphate (ATP) as a possible indicator of extraterrestrial biology  

NASA Technical Reports Server (NTRS)

The ubiquity of adenosine triphosphate (ATP) in terrestrial organisms provides the basis for proposing the assay of this vital metabolic intermediate for detecting extraterrestrial biological activity. If an organic carbon chemistry is present on the planets, the occurrence of ATP is possible either from biosynthetic or purely chemical reactions. However, ATP's relative complexity minimizes the probability of abiogenic synthesis. A sensitive technique for the quantitative detection of ATP was developed using the firefly bioluminescent reaction. The procedure was used successfully for the determination of the ATP content of soil and bacteria. This technique is also being investigated from the standpoint of its application in clinical medicine.

Chappelle, E. W.; Picciolo, G. L.

1974-01-01

350

Regulation of Adenosine Receptor Subtypes during Cultivation of Human Monocytes: Role of Receptors in Preventing Lipopolysaccharide-Triggered Respiratory Burst  

PubMed Central

Adenosine is a potent anti-inflammatory agent that modulates the function of cells involved in the inflammatory response. Here we show that it inhibits lipopolysaccharide (LPS)-induced formation of reactive oxygen intermediates (ROI) in both freshly isolated and cultured human monocytes. Blocking of adenosine uptake and inactivation of the adenosine-degrading enzyme adenosine deaminase enhanced the inhibitory action of adenosine, indicating that both pathways regulate the extracellular adenosine concentration. Adenosine-mediated inhibition could be reversed by XAC (xanthine amine congener), an antagonist of the adenosine receptor A2A, and MRS 1220 {N-9-chloro-2-(2-furanyl)[1, 2, 4]-triazolo[1,5-c]quinazolin-5-benzeneacetamide}, an A3 receptor antagonist, in both cell populations, while DPCPX (1,3-dipropyl-8-cyclopentylxanthine), an A1 receptor antagonist, had no effect. Similar to what was seen with adenosine, CGS 21680, an A2A and A3 receptor agonist, and IB-MECA, a nonselective A1 and A3 receptor agonist, dose dependently prevented ROI formation, indicating the involvement of A3 and probably also A2A in the suppressive effect of adenosine. Pretreatment of monocytes with adenosine did not lead to changes in the LPS-induced increase in intracellular calcium levels ([Ca2+]i). Thus, participation of [Ca2+]i in the action of adenosine seems unlikely. The adenosine-mediated suppression of ROI production was found to be more pronounced when monocytes were cultured for 18 h, a time point at which changes in the mRNA expression of adenosine receptors were observed. Most prominent was the increase in the A2A receptor mRNA. These data demonstrate that cultivation of monocytes is accompanied by changes in the inhibitory action of adenosine mediated by A3 and probably also the A2A receptor and that regulation of adenosine receptors is an integral part of the monocyte differentiation program. PMID:14977938

Thiele, Andrea; Kronstein, Romy; Wetzel, Anne; Gerth, Anja; Nieber, Karen; Hauschildt, Sunna

2004-01-01

351

Spreading depolarization-induced adenosine accumulation reflects metabolic status in vitro and in vivo.  

PubMed

Spreading depolarization (SD), a pathologic feature of migraine, stroke and traumatic brain injury, is a propagating depolarization of neurons and glia causing profound metabolic demand. Adenosine, the low-energy metabolite of ATP, has been shown to be elevated after SD in brain slices and under conditions likely to trigger SD in vivo. The relationship between metabolic status and adenosine accumulation after SD was tested here, in brain slices and in vivo. In brain slices, metabolic impairment (assessed by nicotinamide adenine dinucleotide (phosphate) autofluorescence and O2 availability) was associated with prolonged extracellular direct current (DC) shifts indicating delayed repolarization, and increased adenosine accumulation. In vivo, adenosine accumulation was observed after SD even in otherwise healthy mice. As in brain slices, in vivo adenosine accumulation correlated with DC shift duration and increased when DC shifts were prolonged by metabolic impairment (i.e., hypoglycemia or middle cerebral artery occlusion). A striking pattern of adenosine dynamics was observed during focal ischemic stroke, with nearly all the observed adenosine signals in the periinfarct region occurring in association with SDs. These findings suggest that adenosine accumulation could serve as a biomarker of SD incidence and severity, in a range of clinical conditions. PMID:25160669

Lindquist, Britta E; Shuttleworth, C William

2014-11-01

352

Adenosine Deaminase Deficiency: Metabolic Basis of Immune Deficiency and Pulmonary Inflammation  

Microsoft Academic Search

Genetic deficiencies in the purine catabolic enzyme adenosine deaminase (ADA) in humans results primarily in a severe lymphopenia and immunodeficiency that can lead to the death of affected individuals early in life. The metabolic basis of the immunodeficiency is likely related to the sensitivity of lymphocytes to the accumulation of the ADA substrates adenosine and 2?-deoxyadenosine. Investigations using ADA-deficient mice

Michael R. Blackburn; Rodney E. Kellems

2005-01-01

353

Early prenatal investigation of a pregnancy at risk of adenosine deaminase deficiency using chorionic villi  

Microsoft Academic Search

A pregnancy at risk for adenosine deaminase deficiency and severe combined immunodeficiency disease was investigated using samples of chorionic villi obtained during the eighth week of pregnancy. Adenosine deaminase levels suggested that the fetus was a probable carrier and that a diagnosis of severe combined immunodeficiency disease could be excluded. Enzyme and chromosome results were available within 24 hours of

D A Aitken; D H Gilmore; C A Frew; M E Ferguson-Smith; M J Carty; W R Chatfield

1986-01-01

354

The role of adenosine receptors A2A and A2B signaling in renal fibrosis.  

PubMed

Renal fibrosis, the key histopathological lesion in the development and progression of chronic kidney disease (CKD), has been the focus of much research in recent decades. The growing burden of CKD in both developed and developing nations highlights a need for novel therapies to halt the progression of renal disease. Insights into the pathogenesis of renal fibrosis and the key cellular and molecular mediators have been critical in the process of identifying potential targets of therapy. Adenosine signaling is an innate biological autocrine and paracrine cellular signaling pathway involving several key mediators: ectonucleotidases, adenosine, and adenosine receptors. Short-term activation of the adenosine A2A and A2B receptors decreases inflammation, which precedes renal fibrosis. However, in conditions of persistent, excessive adenosine exposure, such as in patients born with adenosine deaminase (ADA) deficiency, adenosine signaling via A2B receptor promotes renal fibrosis, as seen in chronic inflammation. This review will describe the increasingly recognized complex role of adenosine signaling in the development of renal fibrosis. We will speculate how the knowledge gained may be employed in the search for more effective therapies based on these complex signaling pathways. PMID:25054776

Roberts, Veena S; Cowan, Peter J; Alexander, Stephen I; Robson, Simon C; Dwyer, Karen M

2014-10-01

355

High-Throughput Screening for Functional Adenosine to Inosine RNA Editing Systems  

E-print Network

High-Throughput Screening for Functional Adenosine to Inosine RNA Editing Systems Subhash Pokharel 84112-0850 D eamination of adenosine (A) in RNA is an example of base-modification RNA editing (1 A deamination in mRNA and have been given the name A deaminases that act on RNA (ADARs) (6). A related family

Beal, Peter A.

356

Depression of NMDA-evoked acetylcholine release by endogenous adenosine in striatum slices.  

PubMed

The mechanisms of NMDA-evoked transmitter release are still not clear. We demonstrate for the first time that NMDA-evoked acetylcholine release is depressed by endogenous liberated adenosine in functionally-hypoxic and non-hypoxic brain slices. Adenosine deaminase potentiates the release of 3H-acetylcholine from rat striatum slices in response to N-Methyl-D-Aspartate (NMDA) stimulation, whereas (-)-R-phenylisopropyl-adenosine (R-PIA) decreases the NMDA-evoked transmitter release. The NMDA-evoked transmitter release is potentiated by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) only in adenosine depleted slices. The increase of extraneuronal adenosine by dipyridamole also depresses the presynaptic transmitter release. Our results indicate: (i) that stimulation of NMDA-receptors induces a complex neuronal response, e.g., release of acetylcholine and release of adenosine, (ii) that adenosine induces an agonist high affinity conformation of the A1-receptors which apparently are insensitive to an A1-adenosine receptor-antagonist (DPCPX) and (iii) that brain slices 0.5 mm thick can serve as an experimental model for testing antihypoxic substances. PMID:1759610

Porsche, E; Schwan, T

1991-01-01

357

Adenosine A1 and A2a receptors modulate insulinemia, glycemia, and lactatemia in fetal sheep  

PubMed Central

Adenosine A1 and A2A receptor subtypes modulate metabolism in adult mammals. This study was designed to determine the role of these receptors in regulating plasma levels of insulin, glucose, and lactate in 20 chronically catheterized fetal sheep (>0.8 term). In normoxic fetuses (PaO2 ?24 Torr), systemic blockade of A1 receptors with DPCPX (n = 6) increased plasma concentrations of insulin, glucose, and lactate, but antagonism of A2A receptors with ZM-241385 (n = 5) had no significant effects. Intravascular administration of adenosine (n = 9) reduced insulin concentrations and elevated glucose and lactate levels. DPCPX (n = 6) augmented the glycemic and lactatemic responses of adenosine. In contrast, ZM241385 (n = 5) virtually abolished adenosine-induced hyperglycemia and hyperlactatemia. Isocapnic hypoxia (PaO2 ?13 Torr) suppressed insulinemia and enhanced glycemia and lactatemia, but only the hyperglycemia was blunted by blockade of A1 (n = 6) or A2A (n = 6) receptors. We conclude that 1) endogenous adenosine via A1 receptors depresses plasma concentrations of insulin, glucose, and lactate; 2) exogenous adenosine via A2A receptors increases glucose and lactate levels, but these responses are dampened by stimulation of A1 receptors; and 3) hypoxia, which increases endogenous adenosine concentrations, induces hyperglycemia that is partly mediated by activation of A1 and A2A receptors. We predict that adenosine, via A1 receptors, facilitates at least 12% of glucose uptake and utilization in normoxic fetuses. PMID:19118101

Maeda, Takatsugu; Koos, Brian J.

2009-01-01

358

Modulatory effects of adenosine on inhibitory postsynaptic potentials in the lateral amygdala of the rat  

PubMed Central

Adenosine is a depressant in the central nervous system with pre- and postsynaptic effects. In the present study, intracellular recording techniques were applied to investigate the modulatory effects of adenosine on projection neurons in the lateral rat amygdala (LA), maintained as slices in vitro. Adenosine reversibly reduced the amplitude of a fast inhibitory postsynaptic potential (IPSP) that was evoked by electrical stimulation of the external capsule and pharmacologically isolated by applying an N-methyl-D-aspartate and non-N-methyl-D-aspartate receptor antagonist, DL-(?)-2-amino-5-methyl-4-isoxazolepropionic acid and 6,7-Dinitroquinoxaline-2,3-dione, respectively, and the ?-aminobutyric acidB (GABAB) receptor antagonist CGP 35348. The postsynaptic potential that remained was abolished by locally applying bicuculline. Adenosine reduced the amplitude of the fast IPSP on average by 40.3%. It had no significant effect on responses to exogenously applied GABA, on membrane potential or on input resistance, suggesting that the site of action was at presynaptic inhibitory interneurons in the LA. The response to adenosine was mimicked by the selective adenosine A1 receptor agonist N6-cyclohexyladenosine and blocked by the selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine. Neuronal responsiveness in the amygdala is largely controlled by inhibitory processes. Adenosine can presynaptically downregulate inhibitory postsynaptic responses and could exert dampening effects likely by depression of both excitatory and inhibitory neurotransmitter release. PMID:10498851

Heinbockel, Thomas; Pape, Hans-Christian

1999-01-01

359

Colocalization and Regulated Physical Association of Presynaptic Serotonin Transporters with A3 Adenosine  

E-print Network

Adenosine ReceptorsS Chong-Bin Zhu, Kathryn M. Lindler, Nicholas G. Campbell, James S. Sutcliffe, William A; accepted June 24, 2011 ABSTRACT Activation of A3 adenosine receptors (A3ARs) rapidly enhances the activity by protein kinase G1 (PKGI)- and p38 mitogen-activated protein kinase (MAPK)- linked pathways that support

Blakely, Randy

360

Monoclonal antibodies to adenosine receptor by an auto-anti-idiotypic approach  

SciTech Connect

BALB/c mice were immunized with adenosine 6-aminocaproyl-BSA. Hybridoma cell lines that secreted anti-idiotypic antibodies were identified by their binding to rabbit anti-adenosine antibodies, but not to normal rabbit immunoglobulins. Two such monoclonal antibodies, AA18 and AA21, also inhibited the binding of ({sup 3}H)adenosine to the rabbit anti-adenosine antibodies. Therefore, both appeared to recognize idiotypic determinants on the rabbit anti-adenosine antibodies. The monoclonal antibodies AA18 and AA21 were established as being directed at adenosine receptors by the following criteria: (1) they bound to both rat and bovine brain membranes, and binding could be inhibited by CHA, an adenosine receptor agonist, (2) they inhibited the binding of ({sup 3}H)R-PIA, an adenosine receptor agonist, to rat brain membranes; and (3) they inhibited the adenylate cyclase of rat brain membranes. The monoclonal antibodies were used to screen cDNA libraries in lambda gt11.

Ku, Hsing-Hsu.

1988-01-01

361

Adenosine kinase determines the degree of brain injury after ischemic stroke in mice  

Microsoft Academic Search

Adenosine kinase (ADK) is the major negative metabolic regulator of the endogenous neuroprotectant and homeostatic bioenergetic network regulator adenosine. We used three independent experimental approaches to determine the role of ADK as a molecular target for predicting the brain's susceptibility to ischemic stroke. First, when subjected to a middle cerebral artery occlusion model of focal cerebral ischemia, transgenic fb-Adk-def mice,

Hai-Ying Shen; Theresa A Lusardi; Rebecca L Williams-Karnesky; Jing-Quan Lan; David J Poulsen; Detlev Boison

2011-01-01

362

Adenosine Kinase Modulates Root Gravitropism and Cap Morphogenesis in Arabidopsis1(W)(OA)  

Microsoft Academic Search

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. Unfortu- nately, 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.

Li-Sen Young; Benjamin R. Harrison; Narayana Murthy; Barbara A. Moffatt; Simon Gilroy; Patrick H. Masson

363

Upregulation of adenosine kinase in astrocytes in experimental and human temporal lobe epilepsy  

Microsoft Academic Search

Purpose: Adenosine kinase (ADK) represents the key metabolic enzyme for the regulation of extracellular adenosine levels in the brain. In adult brain, ADK is primarily present in astrocytes. Several lines of experimental evidence support a critical role of ADK in different types of brain injury associated with astrogliosis, which is also a prominent morphologic feature of temporal lobe epilepsy (TLE).

E. Aronica; E. Zurolo; A. Iyer; Groot de M; J. Anink; C. Carbonell; Vliet van E. A; J. C. Baayen; D. Boison; J. A. Gorter

2011-01-01

364

REVIEW Adenosine A2A receptors in Parkinson’s disease treatment  

E-print Network

Abstract Latest results on the action of adenosine A2A receptor antagonists indicate their potential therapeutic usefulness in the treatment of Parkinson’s disease. Basal ganglia possess high levels of adenosine A2A receptors, mainly on the external surfaces of neurons located at the indirect tracts between the striatum, globus pallidus, and substantia nigra. Experiments with animal models of Parkinson’s disease indicate that adenosine A2A receptors are strongly involved in the regulation of the central nervous system. Co-localization of adenosine A2A and dopaminergic D2 receptors in striatum creates a milieu for antagonistic interaction between adenosine and dopamine. The experimental data prove that the best improvement of mobility in patients with Parkinson’s disease could be achieved with simultaneous activation of dopaminergic D2 receptors and inhibition of adenosine A2A receptors. In animal models of Parkinson’s disease, the use of selective antagonists of adenosine A2A receptors, such as istradefylline, led to the reversibility of movement dysfunction. These compounds might improve mobility during both monotherapy and co-administration with L-DOPA and dopamine receptor agonists. The use of adenosine A2A receptor antagonists in combination therapy enables the reduction of the L-DOPA doses, as well as a reduction of

Marek Cie?lak; Micha? Komoszy?ski; Andrzej Wojtczak; M. Cie?lak; M. Komoszy?ski; A. Wojtczak

2007-01-01

365

Kinetic characterization of adenosine deaminase activity in zebrafish (Danio rerio) brain.  

PubMed

Adenosine deaminase (ADA; EC 3.5.4.4) activity is responsible for cleaving adenosine to inosine. In this study we described the biochemical properties of adenosine deamination in soluble and membrane fractions of zebrafish (Danio rerio) brain. The optimum pH for ADA activity was in the range of 6.0-7.0 in soluble fraction and reached 5.0 in brain membranes. A decrease of 31.3% on adenosine deamination in membranes was observed in the presence of 5 mM Zn(2+), which was prevented by 5 mM EDTA. The apparent K(m) values for adenosine deamination were 0.22+/-0.03 and 0.19+/-0.04 mM for soluble and membrane fractions, respectively. The apparent V(max) value for soluble ADA activity was 12.3+/-0.73 nmol NH(3) min(-1) mg(-1) of protein whereas V(max) value in brain membranes was 17.5+/-0.51 nmol NH(3) min(-1) mg(-1) of protein. Adenosine and 2'-deoxyadenosine were deaminated in higher rates when compared to guanine nucleosides in both fractions. Furthermore, a significant inhibition on adenosine deamination in both soluble and membrane fractions was observed in the presence of 0.1 mM of erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA). The presence of ADA activity in zebrafish brain may be important to regulate the adenosine/inosine levels in the CNS of this species. PMID:18582589

Rosemberg, Denis Broock; Rico, Eduardo Pacheco; Senger, Mario Roberto; Dias, Renato Dutra; Bogo, Maurício Reis; Bonan, Carla Denise; Souza, Diogo Onofre

2008-09-01

366

Chlorophyll a and adenosine triphosphate levels in Antarctic and temperate lake sediments  

Microsoft Academic Search

Analysis of adenosine triphosphate (ATP) from surficial sediment layers in two antarctic lakes and two temperate lakes showed a high degree of similarity in spite of differences between trophic state, mictic state, or geographic location. Adenosine triphosphate was found at all levels sampled in temperate lake sediment cores but occasionally was present only in surficial layers of antarctic cores. Surficial

G. M. Simmons; R. A. Wharton; B. C. Parker; D. Andersen

1983-01-01

367

Adenosine Receptor Blockade Augments Interstitial Fluid Levels of Excitatory Amino Acids During Cerebral Ischemia  

Microsoft Academic Search

Summary: The excitotoxic hypothesis suggests that cerebral ischemic damage results in part from the accumulation of the xcitatory and potentially toxic neurotransmitters glutamate and aspartate. Adenosine, which also increases during cerebral ischemia, is proposed to inhibit neurotransmitter release. The purpose of this study was to determine if adenosine receptor blockade exacerbates the accumulation of glutamate and aspartate during cerebral ischemia.

Veronica M. Sciotti; Francis M. Roche; Margaret C. Grabb; David G. L. Van Wylen

1992-01-01

368

Nitric Oxide-Stimulated Increase in Extracellular Adenosine Accumulation in Rat Forebrain Neurons in Culture Is Associated with ATP Hydrolysis and Inhibition of Adenosine Kinase Activity  

Microsoft Academic Search

Adenosine is a putative endogenous sleep-inducing substance, and nitric oxide has been implicated in arousal and sleep mech- anisms. We found that various nitric oxide donors, including diethylamine NONOate (DEA\\/NO), stimulated large increases in extracellular adenosine in nearly pure cultures of forebrain neu- rons. The effect of DEA\\/NO could be blocked by 2-phenyl- 4,4,5,5-tetramethyl-imidazoline-1-oxyl-oxide and could not be mimicked by

Paul A. Rosenberg; Ya Li; Minou Le; Yumin Zhang

2000-01-01

369

Study of A2A adenosine receptor gene deficient mice reveals that adenosine analogue CGS?21680 possesses no A2A receptor-unrelated lymphotoxicity  

PubMed Central

Cell surface A2A adenosine receptor (A2AR) mediated signalling affects a variety of important processes and adenosine analogues possess promising pharmacological properties. Demonstrating the receptor specificity of potentially lymphotoxic adenosine-based drugs facilitates their development for clinical applications. To distinguish between the receptor-dependent and -independent lymphotoxicity and apoptotic activity of adenosine and its analogues we used lymphocytes from A2AR-deficient mice. Comparison of A2AR-expressing (+/+) and A2AR-deficient (?/?) cells in cyclic AMP accumulation assays confirmed that the A2AR agonist CGS?21680 is indeed selective for A2A receptors in T-lymphocytes. Incubation of A2AR-expressing thymocytes with extracellular adenosine or CGS?21680 in vitro results in the death of about 7–15% of thymocytes. In contrast, no death was induced in parallel assays in cells from A2AR-deficient mice, providing genetic evidence that CGS?21680 does not display adenosine receptor-independent intracellular cytotoxicity. The A2A receptor-specific lymphotoxicity of CGS 21680 is also demonstrated in a long-term (6-day) in vitro model of thymocyte positive selection where addition of A2AR antagonist ZM?241,385 did block the effects of CGS?21680, allowing the survival of T cells. The use of cells from adenosine receptor-deficient animals is proposed as a part of the screening process for potential adenosine-based drugs for their receptor-independent cytotoxicity and lymphotoxicity. PMID:10960067

Apasov, Sergey G; Chen, Jiang-Fan; Smith, Patrick T; Schwarzschild, Michael A; Fink, J Stephen; Sitkovsky, Michail V

2000-01-01

370

Interaction centres of purine nucleotides: adenosine-5?-diphosphate and adenosine-5?-triphosphate in their reactions with tetramines and Cu(II) ions  

Microsoft Academic Search

The interactions between the nucleotides: adenosine-5?-diphosphate (ADP) and adenosine-5?-triphosphate (ATP) with spermine (Spm) and 1,11-diamine-4,8-diazaundecane (3,3,3-tet), as well as Cu(II) ions are studied. In the metal-free systems nucleotide–polyamine molecular complexes have been found to form, in which the interaction centres are the nitrogen atoms of the purine ring N(1) and N(7), oxygen atoms of the phosphate group of the nucleotide

A. Gasowska

2003-01-01

371

Adenosine inhibits excitatory but not inhibitory synaptic transmission in the hippocampus.  

PubMed

We examined the effects of adenosine and baclofen on inhibitory (IPSC) and excitatory (EPSC) synaptic currents in dissociated rat hippocampal neurons. Adenosine dramatically reduced monosynaptic EPSCs but failed to diminish IPSCs. This selective effect on EPSCs is likely due to inhibition of excitatory transmitter release because adenosine did not directly alter any properties of postsynaptic neurons. Baclofen depressed both EPSCs and IPSCs to approximately the same extent. These experiments indicate that the presynaptic effects of adenosine and baclofen are clearly separable and that transmitter sensitivities of inhibitory and excitatory neurons can differ. These differences could be exploited in the design of antiepileptic drugs that act at adenosine receptors to limit excitatory neurotransmission without blocking tonic inhibition. PMID:1851219

Yoon, K W; Rothman, S M

1991-05-01

372

Effect of Glucose and Adenosine Phosphates on Production of Extracellular Carbohydrases of Alternaria solani1  

PubMed Central

Production of carbohydrases by Alternaria solani is inhibited by glucose under low growth conditions. In an enriched medium, glucose has little effect on the production of polygalacturonase and cellulase while it still suppresses production of ?-glucosidase. Low levels of all three enzymes were produced in the absence of their respective substrates. Such regulation has been found with many organisms. However, far greater production of these carbohydrases occurred with additions of adenosine phosphates to the growth media. Highest stimulation of enzyme production was by adenosine 5?-phosphate. Adenosine 5?-triphosphate and cyclic 3?, 5?-adenosine monophosphate gave lesser amounts. Starvation appears to induce production of extracellular carbohydrases and adenosine 5?-phosphate may have a role in the starvation process. PMID:16658949

Sands, David C.; Lukens, Raymond J.

1974-01-01

373

Adenosine and ATP Link PCO2 to Cortical Excitability via pH  

PubMed Central

Summary In addition to affecting respiration and vascular tone, deviations from normal CO2 alter pH, consciousness, and seizure propensity. Outside the brainstem, however, the mechanisms by which CO2 levels modify neuronal function are unknown. In the hippocampal slice preparation, increasing CO2, and thus decreasing pH, increased the extracellular concentration of the endogenous neuromodulator adenosine and inhibited excitatory synaptic transmission. These effects involve adenosine A1 and ATP receptors and depend on decreased extracellular pH. In contrast, decreasing CO2 levels reduced extracellular adenosine concentration and increased neuronal excitability via adenosine A1 receptors, ATP receptors, and ecto-ATPase. Based on these studies, we propose that CO2-induced changes in neuronal function arise from a pH-dependent modulation of adenosine and ATP levels. These findings demonstrate a mechanism for the bidirectional effects of CO2 on neuronal excitability in the forebrain. PMID:16364904

Dulla, Chris G.; Dobelis, Peter; Pearson, Tim; Frenguelli, Bruno G.; Staley, Kevin J.; Masino, Susan A.

2007-01-01

374

Reconstruction of the adenosine system by bone marrow-derived mesenchymal stem cell transplantation?  

PubMed Central

In the present study, we transplanted bone marrow-derived mesenchymal stem cells into the CA3 area of the hippocampus of chronic epilepsy rats kindled by lithium chloride-pilocarpine. Immunofluorescence and western blotting revealed an increase in adenosine A1 receptor expression and a decrease in adenosine A2a receptor expression in the brain tissues of epileptic rats 3 months after transplantation. Moreover, the imbalance in the A1 adenosine receptor/A2a adenosine receptor ratio was improved. Electroencephalograms showed that frequency and amplitude of spikes in the hippocampus and frontal lobe were reduced. These results suggested that mesenchymal stem cell transplantation can reconstruct the normal function of the adenosine system in the brain and greatly improve epileptiform discharges.

Kang, Huicong; Hu, Qi; Liu, Xiaoyan; Liu, Yinhe; Xu, Feng; Li, Xiang; Zhu, Suiqiang

2012-01-01

375

Enhanced release of adenosine in rat hind paw following spinal nerve ligation: involvement of capsaicin-sensitive sensory afferents  

Microsoft Academic Search

Modulation of endogenous adenosine levels by inhibition of adenosine metabolism produces a peripheral antinociceptive effect in a neuropathic pain model. The present study used microdialysis to investigate the neuronal mechanisms modulating extracellular adenosine levels in the rat hind paw following tight ligation of the L5 and L6 spinal nerves. Subcutaneous injection of 50 ?l saline into the nerve-injured paw induced

X. J Liu; T. D White; J Sawynok

2002-01-01

376

Adenosine A1 and Prostaglandin EP3 Receptors Mediate Global Airway Contraction after Local Epithelial Injury1  

E-print Network

- osine with adenosine deaminase), cyclooxygenase (COX)-2 or EP3 receptors, epidermal growth factorAdenosine A1 and Prostaglandin EP3 Receptors Mediate Global Airway Contraction after Local (VGCC)­mediated Ca21 influx. We found that inhibition of adenosine A1 receptors (or removal of aden

George, Steven C.

377

An adenosine-to-inosine tRNA-editing enzyme that can perform C-to-U deamination of DNA  

E-print Network

for viability. Enzymes mediating tRNA adenosine deamination in bacteria and yeast contain cytidine deaminase-binding pocket: (i) the adenosine deaminases acting on RNAs (ADARs) and (ii) the polynucle- otide cytidineAn adenosine-to-inosine tRNA-editing enzyme that can perform C-to-U deamination of DNA Mary Anne T

Papavasiliou, F. Nina

378

Adenosine promotes alternative macrophage activation via A2A and A2B receptors  

PubMed Central

Adenosine has been implicated in suppressing the proinflammatory responses of classically activated macrophages induced by Th1 cytokines. Alternative macrophage activation is induced by the Th2 cytokines interleukin (IL)-4 and IL-13; however, the role of adenosine in governing alternative macrophage activation is unknown. We show here that adenosine treatment of IL-4- or IL-13-activated macrophages augments the expression of alternative macrophage markers arginase-1, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), and macrophage galactose-type C-type lectin-1. The stimulatory effect of adenosine required primarily A2B receptors because the nonselective adenosine receptor agonist 5?-N-ethylcarboxamidoadenosine (NECA) increased both arginase activity (EC50=261.8 nM) and TIMP-1 production (EC50=80.67 nM), and both pharmacologic and genetic blockade of A2B receptors prevented the effect of NECA. A2A receptors also contributed to the adenosine augmentation of IL-4-induced TIMP-1 release, as both adenosine and NECA were less efficacious in augmenting TIMP-1 release by A2A receptor-deficient than control macrophages. Of the transcription factors known to drive alternative macrophage activation, CCAAT-enhancer-binding protein ? was required, while cAMP response element-binding protein and signal transducer and activator of transcription 6 were dispensable in mediating the effect of adenosine. We propose that adenosine receptor activation suppresses inflammation and promotes tissue restitution, in part, by promoting alternative macrophage activation.—Csóka, B., Selmeczy, Z., Koscsó, B., Németh, Z. H., Pacher, P., Murray, P. J., Kepka-Lenhart, D., Morris S. M., Jr., Gause, W. C., Leibovich, S. J., Haskó, G. Adenosine promotes alternative macrophage activation via A2A and A2B receptors. PMID:21926236

Csóka, Balázs; Selmeczy, Zsolt; Koscsó, Balázs; Németh, Zoltán H.; Pacher, Pál; Murray, Peter J.; Kepka-Lenhart, Diane; Morris, Sidney M.; Gause, William C.; Leibovich, S. Joseph; Haskó, György

2012-01-01

379

Adenosine regulates the proinflammatory signaling function of thrombin in endothelial cells.  

PubMed

The plasma level of the regulatory metabolite adenosine increases during the activation of coagulation and inflammation. Here we investigated the effect of adenosine on modulation of thrombin-mediated proinflammatory responses in HUVECs. We found that adenosine inhibits the barrier-disruptive effect of thrombin in HUVECs by a concentration-dependent manner. Analysis of cell surface expression of adenosine receptors revealed that A2A and A2B are expressed at the highest level among the four receptor subtypes (A2B ?>?A2A ?>?A1 ?>?A3 ) on HUVECs. The barrier-protective effect of adenosine in response to thrombin was recapitulated by the A2A specific agonist, CGS 21680, and abrogated both by the siRNA knockdown of the A2A receptor and by the A2A -specific antagonists, ZM-241385 and SCH-58261. The thrombin-induced RhoA activation and its membrane translocation were both inhibited by adenosine in a cAMP-dependent manner, providing a molecular mechanism through which adenosine exerts a barrier-protective function. Adenosine also inhibited thrombin-mediated activation of NF-?B and decreased adhesion of monocytic THP-1 cells to stimulated HUVECs via down-regulation of expression of cell surface adhesion molecules, VCAM-1, ICAM-1, and E-selectin. Moreover, adenosine inhibited thrombin-induced elevated expression of proinflammatory cytokines, IL-6 and HMGB-1; and chemokines, MCP-1, CXCL-1, and CXCL-3. Taken together, these results suggest that adenosine may inhibit thrombin-mediated proinflammatory signaling responses, thereby protecting the endothelium from injury during activation of coagulation and inflammation. PMID:24477600

Hassanian, Seyed Mahdi; Dinarvand, Peyman; Rezaie, Alireza R

2014-09-01

380

Effects of extracellular adenosine 5'-triphosphate on human sperm motility.  

PubMed

Extracellular adenosine 5'-triphosphate (ATP) previously has been shown to increase the fertilization percentage in human in vitro fertilization (IVF) performed for male factor infertility. The objective of this study is to determine the effects of extracellular adenosine 5'-triphosphate (ATPe) on human sperm function by examining its effects on end points of sperm capacitation. Sperm obtained from healthy volunteers with normal semen parameters, asthenozoospermic men, and cryopreserved samples were incubated in medium with or without 2.5 mM ATPe. The effects of ATPe on acrosomal exocytosis, protein tyrosine phosphorylation, and sperm motility parameters were quantified. Although ATPe did not affect acrosomal exocytosis or protein tyrosine phosphorylation in sperm from healthy donors, it significantly altered several motility parameters, with the largest effects manifested in increased curvilinear velocity and percentage hyperactivation. ATPe similarly affected sperm selected for poor motility and thawed cryopreserved sperm but to a lesser extent than its effects on sperm with normal motility. ATPe increased straight-line velocity and linearity of sperm obtained from asthenozoospermic men. Human sperm motility characteristics are altered by ATPe; this finding may explain its previously reported beneficial effect on human IVF. These results suggest that ATPe could constitute a new therapeutic modality in the treatment of male infertility. PMID:18000227

Edwards, Scott E; Buffone, Mariano G; Knee, Gerald R; Rossato, Marco; Bonanni, Guglielmo; Masiero, Stefano; Ferasin, Sergio; Gerton, George L; Moss, Stuart B; Williams, Carmen J

2007-10-01

381

Extracellular adenosine regulates naive T cell development and peripheral maintenance  

PubMed Central

Adenosine produced as a byproduct of metabolic activity is present in all tissues and produces dose-dependent suppression of TCR signaling. Naive T cell maintenance depends on inhibition of TCR signals by environmental sensors, which are yet to be fully defined. We produced mice with a floxed adenosine A2A receptor (A2AR) gene, Adora2a, and show that either global A2AR deletion or cre-mediated T cell deletion elicits a decline in the number of naive but not memory T cells. A2AR signaling maintains naive T cells in a quiescent state by inhibiting TCR-induced activation of the phosphatidylinositide 3-kinase (PI3K)–AKT pathway, thereby reducing IL-7R? down-regulation and naive T cell apoptosis. Patterns of IL-7R? expression on T cells in chimeric mice reconstituted with Adora2a+/+ and Adora2a?/? bone marrow cells suggest that decreased IL-7R? in naive T cells is a cell-intrinsic consequence of Adora2a deletion. In addition, A2AR expression increases in early thymic T cell development and contributes to progression of double-negative thymic precursors to single-positive thymocytes with increased IL-7R? expression. Therefore, A2AR signaling regulates T cell development and maintenance to sustain normal numbers of naive T cells in the periphery. PMID:24145516

Cekic, Caglar; Sag, Duygu; Day, Yuan-Ji

2013-01-01

382

Cyclic Adenosine Monophosphate in the Nervous System of Aplysia californica  

PubMed Central

In the isolated abdominal ganglion of Aplysia, previously incubated in adenine-3H, the amount of 3H-labeled adenosine-3',5' monophosphate (cAMP) doubled after electrical stimulation of nerves at a physiological rate (1/sec). No change was detected after 4 min of stimulation. An increase in cAMP was first seen after 15 min; lengthening the period of stimulation to 1 hr did not increase the extent of the effect. ATP contained 50% of the total radioactivity taken up from adenine-3H, cAMP about 0.1%. During stimulation both the total amount and the specific radioactivity of adenosine triphosphate (ATP) did not change. Thus, the increased amount of radioactivity found in cAMP after stimulation represented an increase in its rate of synthesis. During stimulation formation of cAMP-3H was not altered in nerves or in the cell body of an identified neuron (R2). In addition, no changes were detected in the total amounts of cAMP in the ganglion and in the cell body of R2. It seems likely that the increase was initiated by synaptic activity rather than by action potentials. It was blocked by elevating the concentration of Mg, which also blocks synaptic activity without impairing conduction of impulses. Moreover, impulse activity induced by ouabain and glutamate did not result in increased formation of cAMP. PMID:4345439

Cedar, Howard; Kandel, Eric R.; Schwartz, James H.

1972-01-01

383

Genetic approaches to studying adenosine-to-inosine RNA editing.  

PubMed

Increasing proteomic diversity via the hydrolytic deamination of adenosine to inosine (A-to-I) in select mRNA templates appears crucial to the correct functioning of the nervous system in several model organisms, including Drosophila, Caenorabditis elegans, and mice. The genome of the fruitfly, Drosophila melanogaster, contains a single gene encoding the enzyme responsible for deamination, termed ADAR (for adenosine deaminase acting on RNA). The mRNAs that form the substrates for ADAR primarily function in neuronal signaling, and, correspondingly, deletion of ADAR leads to severe nervous system defects. While several ADAR enzymes are present in mice, the presence of a single ADAR in Drosophila, combined with the diverse genetic toolkit available to researchers and the wide range of ADAR target mRNAs identified to date, make Drosophila an ideal organism to study the genetic basis of A-to-I RNA editing. This chapter describes a variety of methods for genetically manipulating Drosophila A-to-I editing both in time and space, as well as techniques to study the molecular basis of ADAR-mRNA interactions. A prerequisite for experiments in this field is the ability to quantify the levels of editing in a given mRNA. Therefore, several commonly used methods for the quantification of editing levels will also be described. PMID:17662845

Jepson, James E C; Reenan, Robert A

2007-01-01

384

Adenosine diphosphate and strain sensitivity in myosin motors.  

PubMed Central

The release of adenosine diphosphate (ADP) from the actomyosin cross-bridge plays an important role in the adenosine-triphosphate-driven cross-bridge cycle. In fast contracting muscle fibres, the rate at which ADP is released from the cross-bridge correlates with the maximum shortening velocity of the muscle fibre, and in some models the rate of ADP release defines the maximum shortening velocity. In addition, it has long been thought that the rate of ADP release could be sensitive to the load on the cross-bridge and thereby provide a molecular explanation of the Fenn effect. However, direct evidence of a strain-sensitive ADP-release mechanism has been hard to come by for fast muscle myosins. The recently published evidence for a strain-sensing mechanism involving ADP release for slower muscle myosins, and in particular non-muscle myosins, is more compelling and can provide the mechanism of processivity for motors such as myosin V. It is therefore timely to examine the evidence for this strain-sensing mechanism. The evidence presented here will argue that a strain-sensitive mechanism of ADP release is universal for all myosins but the basic mechanism has evolved in different ways for different types of myosin. Furthermore, this strain-sensing mechanism provides a way of coordinating the action of multiple myosin motor domains in a single myosin molecule, or in complex assemblies of myosins over long distances without invoking a classic direct allosteric or cooperative communication between motors. PMID:15647162

Nyitrai, Miklós; Geeves, Michael A

2004-01-01

385

Adenosine amine congener mitigates noise-induced cochlear injury  

PubMed Central

Hearing loss from noise exposure is a leading occupational disease, with up to 5% of the population at risk world-wide. Here, we present a novel purine-based pharmacological intervention that can ameliorate noise-induced cochlear injury. Wistar rats were exposed to narrow-band noise (8–12 kHz, 110 dB SPL, 2–24 h) to induce cochlear damage and permanent hearing loss. The selective adenosine A1 receptor agonist, adenosine amine congener (ADAC), was administered intraperitoneally (100 ľg/kg/day) at time intervals after noise exposure. Hearing thresholds were assessed using auditory brainstem responses and the hair cell loss was evaluated by quantitative histology. Free radical damage in the organ of Corti was assessed using nitrotyrosine immunohistochemistry. The treatment with ADAC after noise exposure led to a significantly greater recovery of hearing thresholds compared with controls. These results were upheld by increased survival of sensory hair cells and reduced nitrotyrosine immunoreactivity in ADAC-treated cochlea. We propose that ADAC could be a valuable treatment for noise-induced cochlear injury in instances of both acute and extended noise exposures. PMID:20806018

Lee, Kyu-Hyun; Wong, Ann Chi Yan; Guo, Cindy X.; Gupta, Rita; Housley, Gary D.; Thorne, Peter R.

2010-01-01

386

Adenosine A2A receptors and basal ganglia physiology  

PubMed Central

Adenosine A2A receptors are highly enriched in the basal ganglia system. They are predominantly expressed in enkephalin-expressing GABAergic striatopallidal neurons and therefore are highly relevant to the function of the indirect efferent pathway of the basal ganglia system. In these GABAergic enkephalinergic neurons, the A2A receptor tightly interacts structurally and functionally with the dopamine D2 receptor. Both by forming receptor heteromers and by targeting common intracellular signaling cascades, A2A and D2 receptors exhibit reciprocal antagonistic interactions that are central to the function of the indirect pathway and hence to basal ganglia control of movement, motor learning, motivation and reward. Consequently, this A2A / D2 receptors antagonistic interaction is also central to basal ganglia dysfunction in Parkinson's disease. However, recent evidence demonstrates that, in addition to this postsynaptic site of action, striatal A2A receptors are also expressed and have physiological relevance on presynaptic glutamatergic terminals of the cortico-limbic-striatal and thalamo-striatal pathways, where they form heteromeric receptor complexes with adenosine A1 receptors. Therefore, A2A receptors play an important fine-tuning role, boosting the efficiency of glutamatergic information flow in the indirect pathway by exerting control, either pre- and/or post-synaptically, over other key modulators of glutamatergic synapses, including D2 receptors, group I metabotropic mGlu5 glutamate receptors and cannabinoid CB1 receptors, and by triggering the cAMP-protein kinase A signaling cascade. PMID:17646043

Schiffmann, S.N.; Fisone, G.; Moresco, R.; Cunha, R.A.; Ferré, S.

2007-01-01

387

Methylthioadenosine Reprograms Macrophage Activation through Adenosine Receptor Stimulation  

PubMed Central

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

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

2014-01-01

388

Methylthioadenosine reprograms macrophage activation through adenosine receptor stimulation.  

PubMed

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

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

2014-01-01

389

Adenosine Amine Congener as a Cochlear Rescue Agent  

PubMed Central

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

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

390

Adenosine suppresses protein kinase A- and C-induced enhancement of glutamate release in the hippocampus.  

PubMed

Cultured hippocampal neurons from neonatal rats were used to investigate the effect of adenosine on the release of glutamate. Spontaneous tetrodotoxin-resistant miniature excitatory postsynaptic currents (mEPSCs) through AMPA receptor channels were recorded by means of the whole-cell patch-clamp technique. Adenosine (50 microM) reversibly reduced the frequency of mEPSCs by approximately 50-60%, but did not change their amplitudes. The protein kinase A inhibitor Rp-cyclic adenosine monophosphate (100-150 microM) did not block the adenosine-dependent reduction of the mEPSC frequency, showing that adenosine is not depressing synaptic transmission via a protein kinase A (PKA)-dependent mechanism. The D1 dopamine agonist SKF-38393 (250 microM), forskolin (5 microM) and 8Br-cAMP (2 mM), known to activate the cAMP/PKA-dependent signalling pathway, all enhanced the mEPSC frequency. A subsequent application of adenosine (50 microM) strongly reduced the potentiation produced by any one of these three drugs. It also reversed protein kinase C (PKC)-dependent stimulation of glutamate release induced by phorbol myristate acetate (100 nM). Taken together, adenosine not only inhibits the spontaneous release of glutamate independently of protein kinases A and C but also reverses the enhancement of exocytosis produced by protein kinases A and C activators. PMID:10594671

Bouron, A

1999-12-01

391

Comparative genomic and expression analysis of the adenosine signaling pathway members in Xenopus.  

PubMed

Adenosine is an endogenous molecule that regulates many physiological processes via the activation of four specific G-protein-coupled ADORA receptors. Extracellular adenosine may originate either from the hydrolysis of released ATP by the ectonucleotidases or from cellular exit via the equilibrative nucleoside transporters (SLC29A). Adenosine extracellular concentration is also regulated by its successive hydrolysis into uric acid by membrane-bound enzymes or by cell influx via the concentrative nucleoside transporters (SLC28A). All of these members constitute the adenosine signaling pathway and regulate adenosine functions. Although the roles of this pathway are quite well understood in adults, little is known regarding its functions during vertebrate embryogenesis. We have used Xenopus laevis as a model system to provide a comparative expression map of the different members of this pathway during vertebrate development. We report the characterization of the different enzymes, receptors, and nucleoside transporters in both X. laevis and X. tropicalis, and we demonstrate by phylogenetic analyses the high level of conservation of these members between amphibians and mammals. A thorough expression analysis of these members during development and in the adult frog reveals that each member displays distinct specific expression patterns. These data suggest potentially different developmental roles for these proteins and therefore for extracellular adenosine. In addition, we show that adenosine levels during amphibian embryogenesis are very low, confirming that they must be tightly controlled for normal development. PMID:25319637

Tocco, Alice; Pinson, Benoît; Thiébaud, Pierre; Thézé, Nadine; Massé, Karine

2015-03-01

392

Adenosine A1 receptors presynaptically modulate excitatory synaptic input onto subiculum neurons  

PubMed Central

Adenosine is an endogenous neuromodulator previously shown to suppress synaptic transmission and membrane excitability in the CNS. In this study we have determined the actions of adenosine on excitatory synaptic transmission in the subiculum, the main output area for the hippocampus. Adenosine (10 ?M) reversibly inhibited excitatory post synaptic currents (EPSCs) recorded from subiculum neurons. These actions were mimicked by the A1 receptor specific agonist, N6-cyclopentyl-adenosine (CPA, 10 nM) and blocked by the A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 500 nM), but were unaffected by the A2A antagonist ZM 241385 (50 nM). In membrane excitability experiments, bath application of adenosine and CPA reversibly inhibited action potentials (AP) in subiculum neurons that were evoked by stimulation of the pyramidal cell layer of the CA1, but not by depolarizing current injection steps in subiculum neurons, suggesting a presynaptic mechanism of action. In support, adenosine and CPA application reduced mEPSC frequency without modulating mEPSC amplitude. These studies suggest that modulation of subiculum neuron excitability by adenosine is mediated via presynaptic A1 receptors. PMID:19450566

Hargus, Nicholas J.; Bertram, Edward H.; Patel, Manoj K.

2009-01-01

393

Adenosine A1 receptor-mediated presynaptic inhibition at the calyx of Held of immature rats  

PubMed Central

At the calyx of Held synapse in brainstem slices of 5- to 7-day-old (P5–7) rats, adenosine, or the type 1 adenosine (A1) receptor agonist N6-cyclopentyladenosine (CPA), inhibited excitatory postsynaptic currents (EPSCs) without affecting the amplitude of miniature EPSCs. The A1 receptor antagonist 8-cyclopentyltheophylline (CPT) had no effect on the amplitude of EPSCs evoked at a low frequency, but significantly reduced the magnitude of synaptic depression caused by repetitive stimulation at 10 Hz, suggesting that endogenous adenosine is involved in the regulation of transmitter release. Adenosine inhibited presynaptic Ca2+ currents (IpCa) recorded directly from calyceal terminals, but had no effect on presynaptic K+ currents. When EPSCs were evoked by IpCa during simultaneous pre- and postsynaptic recordings, the magnitude of the adenosine-induced inhibition of IpCa fully explained that of EPSCs, suggesting that the presynaptic Ca2+ channel is the main target of A1 receptors. Whereas the N-type Ca2+ channel blocker ?-conotoxin attenuated EPSCs, it had no effect on the magnitude of adenosine-induced inhibition of EPSCs. During postnatal development, in parallel with a decrease in the A1 receptor immunoreactivity at the calyceal terminal, the inhibitory effect of adenosine became weaker. We conclude that presynaptic A1 receptors at the immature calyx of Held synapse play a regulatory role in transmitter release during high frequency transmission, by inhibiting multiple types of presynaptic Ca2+ channels. PMID:12963795

Kimura, Masahiro; Saitoh, Naoto; Takahashi, Tomoyuki

2003-01-01

394

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

PubMed

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 A(1) 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 (1.5mg/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 16kHz 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

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

2011-11-01

395

Adenosine kinase is a new therapeutic target to prevent ischemic neuronal death.  

PubMed

The brain has evolved several endogenous mechanisms to protect itself from the deleterious consequences of stroke. One of those endogenous neuroprotective systems is centered on the purine ribonucleoside adenosine, which exerts potent neuroprotective functions within the brain. One major goal in therapeutic stroke research is to explore and utilize such endogenous neuroprotective mechanisms therapeutically. This review illustrates molecular approaches to study the role of the adenosine system within the context of stroke and highlights innovative therapeutic approaches aimed at increasing adenosinergic function. New research data suggest that the major adenosine regulating enzyme adenosine kinase (ADK) plays a prominent role in determining the brain's susceptibility to ischemic injury. Thus, endogenous ADK is rapidly downregulated following a stroke, possibly an endogenous neuroprotective mechanism aimed at raising ambient levels of adenosine in brain. Conversely, transgenic overexpression of ADK in brain renders the brain more susceptible to stroke-induced neuronal cell loss. In the present review we will first summarize the physiological role of adenosine metabolism within the context of ischemic brain injury. Next, we will highlight the key role of ADK in determining the brain's susceptibility to ischemic injury, and finally we will discuss potential therapeutic applications of adenosine augmentation to provide neuroprotection in stroke. PMID:24089624

Boison, Detlev; Shen, Hai-Ying

2010-01-01

396

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

PubMed Central

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

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

2001-01-01

397

Release of Adenosine from Human Hearts during Angina Induced by Rapid Atrial Pacing  

PubMed Central

This study was designed to determine whether human hearts release adenosine, a possible regulator of coronary flow, during temporary myocardial ischemia and, if so, to examine the mechanisms involved. Release of adenosine from canine hearts had been reported during reactive hyperemia following brief coronary occlusion, and we initially confirmed this observation in six dogs hearts. Angina was then produced in 15 patients with anginal syndrome and severe coronary atherosclerosis by rapid atrial pacing during diagnostic studies. In 13 of these patients, adenosine appeared in coronary sinus blood, at a mean level of 40 nmol/100 ml blood (SE = ą9). In 11 of these 13, adenosine was not detectable in control or recovery samples; when measured, there was concomitant production of lactate and minimal leakage of K+, but no significant release of creatine phosphokinase, lactic acid dehydrogenase, creatine, or Na+. There was no detectable release of adenosine by hearts during pacing or exercise in three control groups of patients: nine with anginal syndrome and severe coronary atherosclerosis who did not develop angina or produce lactate during rapid pacing, five with normal coronaries and no myocardial disease, and three with normal coronaries but with left ventricular failure. The results indicate that human hearts release significant amounts of adenosine during severe regional myocardial ischemia and anaerobic metabolism. Adenosine release might provide a useful supplementary index of the early effects of ischemia on myocardial metabolism, and might influence regional coronary flow during or after angina pectoris. PMID:4825235

Fox, Arthur C.; Reed, George E.; Glassman, Ephraim; Kaltman, Alfred J.; Silk, Barbara B.

1974-01-01

398

The NLRP3 inflammasome is activated by nanoparticles through ATP, ADP and adenosine.  

PubMed

The NLR pyrin domain containing 3 (NLRP3) inflammasome is a major component of the innate immune system, but its mechanism of activation by a wide range of molecules remains largely unknown. Widely used nano-sized inorganic metal oxides such as silica dioxide (nano-SiO2) and titanium dioxide (nano-TiO2) activate the NLRP3 inflammasome in macrophages similarly to silica or asbestos micro-sized particles. By investigating towards the molecular mechanisms of inflammasome activation in response to nanoparticles, we show here that active adenosine triphosphate (ATP) release and subsequent ATP, adenosine diphosphate (ADP) and adenosine receptor signalling are required for inflammasome activation. Nano-SiO2 or nano-TiO2 caused a significant increase in P2Y1, P2Y2, A2A and/or A2B receptor expression, whereas the P2X7 receptor was downregulated. Interestingly, IL-1? secretion in response to nanoparticles is increased by enhanced ATP and ADP hydrolysis, whereas it is decreased by adenosine degradation or selective A2A or A2B receptor inhibition. Downstream of these receptors, our results show that nanoparticles activate the NLRP3 inflammasome via activation of PLC-InsP3 and/or inhibition of adenylate cyclase (ADCY)-cAMP pathways. Finally, a high dose of adenosine triggers inflammasome activation and IL-1? secretion through adenosine cellular uptake by nucleotide transporters and by its subsequent transformation in ATP by adenosine kinase. In summary, we show for the first time that extracellular adenosine activates the NLRP3 inflammasome by two ways: by interacting with adenosine receptors at nanomolar/micromolar concentrations and through cellular uptake by equilibrative nucleoside transporters at millimolar concentrations. These findings provide new molecular insights on the mechanisms of NLRP3 inflammasome activation and new therapeutic strategies to control inflammation. PMID:25654762

Baron, L; Gombault, A; Fanny, M; Villeret, B; Savigny, F; Guillou, N; Panek, C; Le Bert, M; Lagente, V; Rassendren, F; Riteau, N; Couillin, I

2015-01-01

399

Value and limitations of adenosine in the diagnosis and treatment of narrow and broad complex tachycardias.  

PubMed

The diagnostic and therapeutic potential of intravenous adenosine was studied in 64 patients during 92 episodes of regular sustained tachycardia. In 40 patients who had narrow complex tachycardias (QRS less than 0.12 s) adenosine (2.5-25 mg) restored sinus rhythm in 25 with junctional tachycardias (46 of 48 episodes) and produced atrioventricular block to reveal atrial or sinus tachycardia in 15. In 24 patients with broad complex tachycardias (QRS greater than or equal to 0.12 s) adenosine terminated the tachycardias in six patients and revealed atrial or sinus arrhythmias in four. The tachycardias persisted in 14 patients despite doses up to 20 mg, but adenosine allowed the diagnosis of ventricular tachycardia with retrograde atrial activation in two patients by producing transient ventriculoatrial dissociation. Diagnosis based on adenosine induced atrioventricular nodal block was correct in all patients with narrow complex tachycardias and in 92% of those with broad complex tachycardias, compared with correct electrocardiographic diagnoses in 90% and 75% respectively. Adenosine gave diagnostic information additional to the electrocardiogram in 25%. The response to adenosine in broad complex tachycardias identified those of supraventricular origin with 90% sensitivity, 93% specificity, and 92% predictive accuracy. Adenosine restored sinus rhythm in all patients with junctional reentrant tachycardias, but in 10 (35%) the arrhythmias recurred within two minutes. Symptomatic side effects (dyspnoea, chest pain, flushing, headache) were reported by 40 (63%) patients and, although transient, were severe in 23 (36%). There were ventricular pauses of over 2 s in 16% of patients, the longest pause being 6.1 s. Adenosine is of value in the diagnosis and treatment of narrow and broad complex tachycardias, but its use is limited by symptomatic side effects, a tenfold range in minimal effective dosage, occasional action at sites other than the atrioventricular node, and early recurrence or arrhythmia. PMID:2789911

Rankin, A C; Oldroyd, K G; Chong, E; Rae, A P; Cobbe, S M

1989-09-01

400

Adenosine modulates light responses of rat retinal ganglion cell photoreceptors througha cAMP-mediated pathway.  

PubMed

Adenosine is an established neuromodulator in the mammalian retina, with A1 adenosine receptors being especially prevalent in the innermost ganglion cell layer. Activation of A1 receptors causes inhibition of adenylate cyclase, decreases in intracellular cyclic AMP (cAMP) levels and inhibition of protein kinase A (PKA). In this work, our aim was to characterize the effects of adenosine on the light responses of intrinsically photosensitive retinal ganglion cells (ipRGCs) and to determine whether these photoreceptors are subject to neuromodulation through intracellular cAMP-related signalling pathways. Using multielectrode array recordings from postnatal and adult rat retinas, we demonstrated that adenosine significantly shortened the duration of ipRGC photoresponses and reduced the number of light-evoked spikes fired by these neurons. The effects were A1 adenosine receptor-mediated, and the expression of this receptor on melanopsin-containing ipRGCs was confirmed by calcium imaging experiments on isolated cells in purified cultures. While inhibition of the cAMP/PKA pathway by adenosine shortened ipRGC light responses, stimulation of this pathway with compounds such as forskolin had the opposite effect and lengthened the duration of ipRGC spiking. Our findings reveal that the modification of ipRGC photoresponses through a cAMP/PKA pathway is a general feature of rat ganglion cell photoreceptors, and this pathway can be inhibited through activation of A1 receptors by adenosine. As adenosine levels in the retina rise at night, adenosinergic modulation of ipRGCs may serve as an internal regulatory mechanism to limit transmission of nocturnal photic signals by ipRGCs to the brain. Targeting retinal A1 adenosine receptors for ipRGC inhibition represents a potential therapeutic target for sleep disorders and migraine-associated photophobia. PMID:25038240

Sodhi, Puneet; Hartwick, Andrew T E

2014-10-01

401

Chemiosmotic coupling in Methanobacterium thermoautotrophicum: hydrogen-dependent adenosine 5'-triphosphate synthesis by subcellular particles.  

PubMed Central

Hydrogenase and the adenosine 5'-triphosphate (ATP) synthetase complex, two enzymes essential in ATP generation in Methanobacterium thermoautotrophicum, were localized in internal membrane systems as shown by cytochemical techniques. Membrane vesicles from this organism possessed hydrogenase and adenosine triphosphatase (ATPase) activity and synthesized ATP driven by hydrogen oxidation or a potassium gradient. ATP synthesis depended on anaerobic conditions and could be inhibited in membrane vesicles by uncouplers, nigericin, or the ATPase inhibitor N,N'-dicyclohexylcarbodiimide. The presence of an adenosine 5'-diphosphate-ATP translocase was postulated. With fluorescent dyes, a membrane potential and pH gradient were demonstrated. Images PMID:160408

Doddema, H J; van der Drift, C; Vogels, G D; Veenhuis, M

1979-01-01

402

The transmethylation pathway as a source for adenosine in the isolated guinea-pig heart.  

PubMed Central

In order to quantify adenosine production from the transmethylation pathway [S-adenosylmethionine (AdoMet)----S-adenosylhomocysteine (AdoHcy) in equilibrium adenosine + L-homocysteine] in the isolated guinea-pig heart under basal conditions (normoxic perfusion with 95% O2) and during elevated adenosine production (hypoxic perfusion with 30% O2), two methods were used. (1) Hearts were perfused with normoxic medium containing [2,5,8-3H]adenosine (5 microM) and L-homocysteine thiolactone (0.1 mM), which brings about net AdoHcy synthesis via reversal of the AdoHcy hydrolase reaction and labels the intracellular pool of AdoHcy. From the decrease in AdoHcy pool size and specific radioactivity of AdoHcy in the post-labelling period, the rate of transmethylation, which is equivalent to the rate of adenosine production, was calculated to be 0.98 nmol/min per g. Adenosine release from the hearts was 40-50 pmol/min per g. (2) Hearts were perfused with hypoxic medium containing [35S]homocysteine (50 microM). Owing to the hypoxia-induced increase in adenosine production, this procedure also results in expansion and labelling of the AdoHcy pool. From the dilution of the specific radioactivity of AdoHcy relative to that of [35S]homocysteine, the rate of AdoHcy synthesis from AdoMet (transmethylation) was calculated to be 1.12 nmol/min per g. It is concluded that in the oxygenated heart the transmethylation pathway is quantitatively an important intracellular source of adenosine, which exceeds the rate of adenosine wash-out by the coronary system by about 15-fold. Most of the adenosine formed by this pathway is re-incorporated into the ATP pool, most likely by adenosine kinase. The transmethylation pathway is essentially O2-independent, and the known hypoxia-induced production of adenosine must be derived from an increase in 5'-AMP hydrolysis. PMID:3415668

Lloyd, H G; Deussen, A; Wuppermann, H; Schrader, J

1988-01-01

403

Probing GPCR Structure: Adenosine and P2Y Nucleotide Receptors  

PubMed Central

The adenosine receptors (ARs) provide an example of how to accurately predict ligand recognition, even prior to the availability of a crystallographic structure. Homology modeling has been used to gain structural insight, in conjunction with site-directed mutagenesis and structure activity relationships of small molecular ligands. Recent X-ray structures greatly improved the accuracy of knowledge of AR ligand recogntion and furthermore characterized conformational changes induced by receptor activation. Now homology modeling extends these structural insights to related GPCRs and suggests new ligand structures. This strategy is also being applied to the eight subtypes of P2Y receptors for extracellular nucleotides, which lack X-ray structures and are best modeled by homology to the CXCR4 (peptide) receptor. Neoceoptors, as studied for three of the four AR subtypes, create a molecular complementarity between a mutant receptor and a chemically tailored agonist ligand to selectively enhance affinity, implying direct physical contact and thus validating docking hypotheses. PMID:23332701

Jacobson, Kenneth A.; Costanzi, Stefano; Deflorian, Francesca

2013-01-01

404

Late-onset adenosine deaminase deficiency presenting with Heck's disease.  

PubMed

Focal epithelial hyperplasia, also known as Heck's disease, is a rare but distinctive entity of viral etiology with characteristic clinical and histopathological features. It is a benign, asymptomatic disease of the oral mucosa caused by human papilloma viruses (HPV). Previous studies postulated an association between these lesions and immunodeficiency. Genetic deficiency of adenosine deaminase (ADA) results in varying degrees of immunodeficiency, including neonatal onset severe combined immunodeficiency (ADA-SCID), and milder, later onset immunodeficiency. We report a 12-year-old girl with the late onset-ADA deficiency presenting with Heck's disease. Our case report should draw attention to the possibility of immunodeficiency in patients with HPV-induced focal epithelial hyperplasia. PMID:20039061

Artac, Hasibe; Göktürk, Bahar; Bozdemir, Sefika Elmas; Toy, Hatice; van der Burg, Mirjam; Santisteban, Ines; Hershfield, Michael; Reisli, Ismail

2010-08-01

405

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

PubMed

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

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

1994-10-01

406

Recent Developments in A 2B Adenosine Receptor Ligands  

Microsoft Academic Search

\\u000a A selective, high-affinity A2B adenosine receptor (AR) antagonist will be useful as a pharmacological tool to help determine the role of the A2BAR in inflammatory diseases and angiogenic diseases. Based on early A2BAR-selective ligands with nonoptimal pharmaceutical properties, such as 15 (MRS 1754: Ki(hA2B)  =  2 nM; Ki(hA1)  =  403 nM; Ki(hA2A)  =  503 nM{K}_{\\\\mathrm{i}}(\\\\mathrm{h{A}_{2B}})\\\\;=\\\\;2\\\\,\\\\mathrm{nM};\\\\ {K}_{\\\\mathrm{i}}({\\\\mathrm{hA}}_{1})\\\\;=\\\\;403\\\\,\\\\mathrm{nM};\\\\ {K}_{\\\\mathrm{i}}(\\\\mathrm{h{A}_{2A}})\\\\;=\\\\;503\\\\,\\\\mathrm{nM}, and K\\u000a i(hA3) = 570 nM), several groups have discovered second-generation A2BAR ligands that

Rao V. Kalla; Jeff Zablocki; Mojgan Aghazadeh Tabrizi; Pier Giovanni Baraldi

407

Stimulation of postmortem platelets with adenosine-5-diphosphate and epinephrine.  

PubMed

In an earlier study, we assessed the aggregation of postmortem platelets following stimulation with collagen and arachidonic acid [1]. We now extend those investigations to include the effects of stimulation with various concentrations of adenosine-5-diphosphate (ADP) and epinephrine on the aggregation of platelets in 463 blood samples during the first 10 h postmortem (hpm). Stimulation with low concentrations of ADP and of the weak in vivo agent epinephrine evoked only potentially reversible 1st order aggregation and not irreversible 2nd order aggregation, indicating that the release reaction of platelets is already impaired in the early postmortem hours by milieu changes within the cadaver. These findings, like those of our previous study, demonstrate the feasibility of utilizing the aggregation behaviour of postmortem platelets as a tool for estimating time of death as well as for differentiating between intravital and postmortem hematomas. PMID:9306663

Thomsen, H; Schmidtke, E

1997-09-19

408

N6-Adenosine Methylation in MiRNAs  

PubMed Central

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

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

2015-01-01

409

Footprint traversal by adenosine-triphosphate-dependent chromatin remodeler motor  

NASA Astrophysics Data System (ADS)

Adenosine-triphosphate (ATP)-dependent chromatin remodeling enzymes (CREs) are biomolecular motors in eukaryotic cells. These are driven by a chemical fuel, namely, ATP. CREs actively participate in many cellular processes that require accessibility of specific segments of DNA which are packaged as chromatin. The basic unit of chromatin is a nucleosome where 146 bp ˜ 50 nm of a double-stranded DNA (dsDNA) is wrapped around a spool formed by histone proteins. The helical path of histone-DNA contact on a nucleosome is also called “footprint.” We investigate the mechanism of footprint traversal by a CRE that translocates along the dsDNA. Our two-state model of a CRE captures effectively two distinct chemical (or conformational) states in the mechanochemical cycle of each ATP-dependent CRE. We calculate the mean time of traversal. Our predictions on the ATP dependence of the mean traversal time can be tested by carrying out in vitro experiments on mononucleosomes.

Garai, Ashok; Mani, Jesrael; Chowdhury, Debashish

2012-04-01

410

Adenosine Monophosphate-Based Detection of Bacterial Spores  

NASA Technical Reports Server (NTRS)

A method of rapid detection of bacterial spores is based on the discovery that a heat shock consisting of exposure to a temperature of 100 C for 10 minutes causes the complete release of adenosine monophosphate (AMP) from the spores. This method could be an alternative to the method described in the immediately preceding article. Unlike that method and related prior methods, the present method does not involve germination and cultivation; this feature is an important advantage because in cases in which the spores are those of pathogens, delays involved in germination and cultivation could increase risks of infection. Also, in comparison with other prior methods that do not involve germination, the present method affords greater sensitivity. At present, the method is embodied in a laboratory procedure, though it would be desirable to implement the method by means of a miniaturized apparatus in order to make it convenient and economical enough to encourage widespread use.

Kern, Roger G.; Chen, Fei; Venkateswaran, Kasthuri; Hattori, Nori; Suzuki, Shigeya

2009-01-01

411

Structural and Metabolic Specificity of Methylthiocoformycin for Malarial Adenosine Deaminases  

SciTech Connect

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.

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

2009-01-01

412

Adenosine Deaminases Acting on RNA, RNA Editing, and Interferon Action  

PubMed Central

Adenosine deaminases acting on RNA (ADARs) catalyze adenosine (A) to inosine (I) editing of RNA that possesses double-stranded (ds) structure. A-to-I RNA editing results in nucleotide substitution, because I is recognized as G instead of A both by ribosomes and by RNA polymerases. A-to-I substitution can also cause dsRNA destabilization, as I:U mismatch base pairs are less stable than A:U base pairs. Three mammalian ADAR genes are known, of which two encode active deaminases (ADAR1 and ADAR2). Alternative promoters together with alternative splicing give rise to two protein size forms of ADAR1: an interferon-inducible ADAR1-p150 deaminase that binds dsRNA and Z-DNA, and a constitutively expressed ADAR1-p110 deaminase. ADAR2, like ADAR1-p110, is constitutively expressed and binds dsRNA. A-to-I editing occurs with both viral and cellular RNAs, and affects a broad range of biological processes. These include virus growth and persistence, apoptosis and embryogenesis, neurotransmitter receptor and ion channel function, pancreatic cell function, and post-transcriptional gene regulation by microRNAs. Biochemical processes that provide a framework for understanding the physiologic changes following ADAR-catalyzed A-to-I (?=?G) editing events include mRNA translation by changing codons and hence the amino acid sequence of proteins; pre-mRNA splicing by altering splice site recognition sequences; RNA stability by changing sequences involved in nuclease recognition; genetic stability in the case of RNA virus genomes by changing sequences during viral RNA replication; and RNA-structure-dependent activities such as microRNA production or targeting or protein–RNA interactions. PMID:21182352

George, Cyril X.; Gan, Zhenji; Liu, Yong

2011-01-01

413

Adenosine A?a receptors and O? sensing in development.  

PubMed

Reduced mitochondrial oxidative phosphorylation, via activation of adenylate kinase and the resulting exponential rise in the cellular AMP/ATP ratio, appears to be a critical factor underlying O? sensing in many chemoreceptive tissues in mammals. The elevated AMP/ATP ratio, in turn, activates key enzymes that are involved in physiologic adjustments that tend to balance ATP supply and demand. An example is the conversion of AMP to adenosine via 5'-nucleotidase and the resulting activation of adenosine A(?A) receptors, which are involved in acute oxygen sensing by both carotid bodies and the brain. In fetal sheep, A(?A) receptors associated with carotid bodies trigger hypoxic cardiovascular chemoreflexes, while central A(?A) receptors mediate hypoxic inhibition of breathing and rapid eye movements. A(?A) receptors are also involved in hypoxic regulation of fetal endocrine systems, metabolism, and vascular tone. In developing lambs, A(?A) receptors play virtually no role in O? sensing by the carotid bodies, but brain A(?A) receptors remain critically involved in the roll-off ventilatory response to hypoxia. In adult mammals, A(?A) receptors have been implicated in O? sensing by carotid glomus cells, while central A(?A) receptors likely blunt hypoxic hyperventilation. In conclusion, A(?A) receptors are crucially involved in the transduction mechanisms of O? sensing in fetal carotid bodies and brains. Postnatally, central A(?A) receptors remain key mediators of hypoxic respiratory depression, but they are less critical for O? sensing in carotid chemoreceptors, particularly in developing lambs. PMID:21677265

Koos, Brian J

2011-09-01

414

Adenosine kinase modulates root gravitropism and cap morphogenesis in Arabidopsis.  

PubMed

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

Young, Li-Sen; Harrison, Benjamin R; Narayana Murthy, U M; Moffatt, Barbara A; Gilroy, Simon; Masson, Patrick H

2006-10-01

415

Alteration of sodium, potassium-adenosine triphosphatase activity in rabbit ciliary processes by cyclic adenosine monophosphate-dependent protein kinase  

SciTech Connect

The response of sodium, potassium-adenosine triphosphatase (Na,K-ATPase) to cyclic adenosine monophosphate (cAMP)-dependent protein kinase was examined in membranes obtained from rabbit iris-ciliary body. In the presence of the protein kinase together with 10(-5) M cAMP, Na,K-ATPase activity was reduced. No change in Na,K-ATPase activity was detected in response to the protein kinase without added cAMP. Likewise cAMP alone did not alter Na,K-ATPase activity. Reduction of Na,K-ATPase activity was also observed in the presence of the cAMP-dependent protein kinase catalytic subunit. The response of the enzyme to the kinase catalytic subunit was also examined in membranes obtained from rabbit ciliary processes. In the presence of 8 micrograms/ml of the catalytic subunit, ciliary process Na,K-ATPase activity was reduced by more than 50%. To examine whether other ATPases were suppressed by the protein kinase, calcium-stimulated ATPase activity was examined; its activity was stimulated by the catalytic subunit. To test whether the response of the ciliary process Na,K-ATPase is unique, experiments were also performed using membrane preparations from rabbit lens epithelium or rabbit kidney; the catalytic subunit significantly reduced the activity of Na,K-ATPase from the kidney but not the lens. These Na,K-ATPase studies suggest that in the iris-ciliary body, cAMP may alter sodium pump activity. In parallel 86Rb uptake studies, we observed that ouabain-inhibitable potassium uptake by intact pieces of iris-ciliary body was reduced by exogenous dibutryl cAMP or by forskolin.

Delamere, N.A.; Socci, R.R.; King, K.L. (Univ. of Louisville School of Medicine, KY (USA))

1990-10-01

416

Association of adenosine receptor gene polymorphisms and in vivo adenosine A1 receptor binding in the human brain.  

PubMed

Adenosine A1 receptors (A1ARs) and the interacting adenosine A2A receptors are implicated in neurological and psychiatric disorders. Variants within the corresponding genes ADORA1 and ADORA2A were shown associated with pathophysiologic alterations, particularly increased anxiety. It is unknown so far, if these variants might modulate the A1AR distribution and availability in different brain regions. In this pilot study, the influence of ADORA1 and ADORA2A variants on in vivo A1AR binding was assessed with the A1AR-selective positron emission tomography (PET) radioligand [(18)F]CPFPX in brains of healthy humans. Twenty-eight normal control subjects underwent PET procedures to calculate the binding potential BPND of [(18)F]CPFPX in cerebral regions and to assess ADORA1 and ADORA2A single nucleotide polymorphism (SNP) effects on regional BPND data. Our results revealed SNPs of both genes associated with [(18)F]CPFPX binding to the A1AR. The strongest effects that withstood even Bonferroni correction of multiple SNP testing were found in non-smoking subjects (N=22) for ADORA2A SNPs rs2236624 and rs5751876 (corr. Pall<0.05). SNP alleles previously identified at risk for increased anxiety like the rs5751876 T-allele corresponded to consistently higher A1AR availability in all brain regions. Our data indicate for the first time that variation of A1AR availability was associated with ADORA SNPs. The finding of increased A1AR availability in regions of the fear network, particularly in ADORA2A risk allele carriers, strongly warrants evaluation and replication in further studies including individuals with increased anxiety. PMID:24943643

Hohoff, Christa; Garibotto, Valentina; Elmenhorst, David; Baffa, Anna; Kroll, Tina; Hoffmann, Alana; Schwarte, Kathrin; Zhang, Weiqi; Arolt, Volker; Deckert, Jürgen; Bauer, Andreas

2014-12-01

417

Antibody Responses to Bacteriophage +X174 in Patients With Adenosine Deaminase Deficiency  

Microsoft Academic Search

ENETICALLY DETERMINED deficiency of the G enzyme adenosine deaminase (ADA) is a cause of the clinical syndrome of severe combined immunodefi- ciency (SCID) with its associated recurrent infections and failure to thrive. If untreated, the condition is usually fatal

Hans D. Ochs; Rebecca H. Buckley; Roger H. Kobayashi; Ai Lan Kobayashi; Ricardo U. Sorensen; Steven D. Douglas; Brian L. Hamilton; Michael S. Hershfield

1992-01-01

418

Crystal Structure of Saccharomyces cereVisiae 3-Phosphoadenosine-5-phosphosulfate Reductase Complexed with Adenosine  

E-print Network

Complexed with Adenosine 3,5-Bisphosphate, Zhihao Yu,§ Donna Lemongello,|, Irwin H. Segel,| and Andrew J-6). APS can be phosphorylated by APS kinase to generate PAPS, the universal sulfate donor (7). In plants

Fisher, Andrew J.

419

Passive targeting of ischemic-reperfused myocardium with adenosine-loaded silica nanoparticles  

PubMed Central

Pharmacological agents suggested for infarct size limitation have serious side effects when used at cardioprotective doses which hinders their translation into clinical practice. The solution to the problem might be direct delivery of cardioprotective drugs into ischemic-reperfused myocardium. In this study, we explored the potential of silica nanoparticles for passive delivery of adenosine, a prototype cardioprotective agent, into ischemic-reperfused heart tissue. In addition, the biodegradation of silica nanoparticles was studied both in vitro and in vivo. Immobilization of adenosine on the surface of silica nanoparticles resulted in enhancement of adenosine-mediated infarct size limitation in the rat model. Furthermore, the hypotensive effect of adenosine was attenuated after its adsorption on silica nanoparticles. We conclude that silica nanoparticles are biocompatible materials that might potentially be used as carriers for heart-targeted drug delivery. PMID:22619519

Galagudza, Michael; Korolev, Dmitry; Postnov, Viktor; Naumisheva, Elena; Grigorova, Yulia; Uskov, Ivan; Shlyakhto, Eugene

2012-01-01

420

Laboratory procedures manual for the firefly luciferase assay for adenosine triphosphate (ATP)  

NASA Technical Reports Server (NTRS)

A manual on the procedures and instruments developed for the adenosine triphosphate (ATP) luciferase assay is presented. Data cover, laboratory maintenance, maintenance of bacterial cultures, bacteria measurement, reagents, luciferase procedures, and determination of microbal susceptibility to antibiotics.

Chappelle, E. W.; Picciolo, G. L.; Curtis, C. A.; Knust, E. A.; Nibley, D. A.; Vance, R. B.

1975-01-01

421

Adenosine A1 and A2A Receptors in Mouse Prefrontal Cortex Modulate Acetylcholine Release and Behavioral Arousal  

PubMed Central

During prolonged intervals of wakefulness brain adenosine levels rise within the basal forebrain and cortex. The view that adenosine promotes sleep is supported by the corollary that N-methylated xanthines such as caffeine increase brain and behavioral arousal by blocking adenosine receptors. The four subtypes of adenosine receptors are distributed heterogeneously throughout the brain, yet the neurotransmitter systems and brain regions through which adenosine receptor blockade causes arousal are incompletely understood. This study tested the hypothesis that adenosine A1 and A2A receptors in the prefrontal cortex contribute to the regulation of behavioral and cortical arousal. Dependent measures included acetylcholine (ACh) release in the prefrontal cortex, cortical electroencephalographic (EEG) power, and time to waking after anesthesia. Sleep and wakefulness were also quantified after microinjecting an adenosine A1 receptor antagonist into the prefrontal cortex. The results showed that adenosine A1 and A2A receptors in the prefrontal cortex modulate cortical ACh release, behavioral arousal, EEG delta power, and sleep. Additional dual microdialysis studies revealed that ACh release in the pontine reticular formation is significantly altered by dialysis delivery of adenosine receptor agonists and antagonists to the prefrontal cortex. These data, and early brain transection studies demonstrating that the forebrain is not needed for sleep cycle generation, suggest that the prefrontal cortex modulates EEG and behavioral arousal via descending input to the pontine brainstem. The results provide novel evidence that adenosine A1 receptors within the prefrontal cortex comprise part of a descending system that inhibits wakefulness. PMID:19158311

Van Dort, Christa J.; Baghdoyan, Helen A.; Lydic, Ralph

2012-01-01

422

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

Microsoft Academic Search

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, the authors determined whether a 48-hr pretreatment with methotrexate affected adenosine release from (š⁴C)adenine-labeled human fibroblasts and umbilical vein endothelial cells. Methotrexate significantly increased adenosine release

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

1991-01-01

423

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

E-print Network

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...

VanDuker, Frank Cal

1988-01-01

424

Generation of normal lymphocyte populations following transplantation of adenosine–deaminase-deficient fetal liver cells  

Microsoft Academic Search

Adenosine–deaminase-deficient mice were generated to investigate the role of adenosine deaminase (ADA) in lymphocyte maturation and to test treatment options for the severe combined immunodeficiency (SCID) associated with the absence of ADA in man. Whereas either genetic absence or postnatal inhibition of ADA affect primarily the haematopoietic system in both humans and mice, ADA-deficient mice die in the perinatal period.

AAJ Migchielsen; S Knaän-Schanzer; ML Breuer; D Valerio

1997-01-01

425

Synthesis of 3?-Acetamidoadenosine Derivatives as Potential A3 Adenosine Receptor Agonists  

Microsoft Academic Search

On the basis of high binding affinity of 3?-aminoadenosine derivatives 2b at the human A3 adenosine receptor (AR), 3?-acetamidoadenosine derivatives 3a–e were synthesized from 1,2:5,6-di-O-isopropylidene-D-glucose via stereoselective hydroboration as a key step. Although all synthesized compounds were totally devoid of binding affinity at the human A3AR, our results revealed that 3?-position of adenosine can only be tolerated with small size

Moon Woo Chun; Sung Wook Choi; Tae Kyung Kang; Won Jun Choi; Hea Ok Kim; Zhan-Guo Gao; Kenneth A. Jacobson; Lak Shin Jeong

2008-01-01

426

Spectroscopic studies on molecular recognition capabilities of a nucleolipid bearing thymine headgroup to adenosine  

Microsoft Academic Search

The Langmuir–Blodgett (LB) films of octadecanoyl ester of 1-(2-carboxyethyl) thymine deposited from pure water and aqueous adenosine subphases were investigated by ultraviolet–visible (UV–vis), Fourier transform infrared-attenuated total reflection (FTIR-ATR), and Fourier transform surface-enhanced Raman scattering (FT-SERS) spectroscopy. The obtained spectral results indicate that the adenosine molecules in the subphase can be transferred onto solid substrates by LB techniques as a

Chun Li; Jianguo Huang; Yingqiu Liang

2001-01-01

427

Opiate-induced Changes in Brain Adenosine Levels and Narcotic Drug Responses  

PubMed Central

We have very little information about the metabolomic changes that mediate neurobehavioral responses, including addiction. It was possible that opioid-induced metabolomic changes in brain could mediate some of the pharmacodynamic effects of opioids. To investigate this, opiate-induced brain metabolomic responses were profiled using a semi-targeted method in C57BL/6 and 129Sv1 mice, which exhibit extreme differences in their tendency to become opiate dependent. Escalating morphine doses (10–40 mg/kg) administered over a 4-day period selectively induced a two-fold decrease (p<0.00005) in adenosine abundance in the brainstem of C57BL/6 mice, which exhibited symptoms of narcotic drug dependence; but did not decrease adenosine abundance in 129Sv1 mice, which do not exhibit symptoms of dependence. Based on this finding, the effect of adenosine on dependence was investigated in genetically engineered mice with alterations in adenosine tone in the brain and in pharmacologic experiments. Morphine withdrawal behaviors were significantly diminished (P<0.0004) in genetically engineered mice with reduced adenosine tone in the brainstem, and by treatment with an adenosine receptor1 (A1) agonist (2-chloro-N6-cyclopentyladenosine, 0.5 mg/kg) or an A2a receptor (A2a) antagonist (SCH 58261 1 mg/kg). These results indicate that adenosine homeostasis plays a crucial role in narcotic drug responses. Opiate-induced changes in brain adenosine levels may explain many important neurobehavioral features associated with opiate addiction and withdrawal. PMID:23098802

Wu, Manhong; Sahbaie, Peyman; Zheng, Ming; Lobato, Robert; Boison, Detlev; Clark, J. David; Peltz, Gary

2012-01-01

428

A Kinetic Comparison on the Inhibition of Adenosine Deaminase by Purine Drugs  

Microsoft Academic Search

The effects of allopurinol, acyclovir and theophylline on the activity of adenosine deaminase (ADA) were studied in 50 mM sodium phosphate buffer pH 7.5 at 27 °C, using a UV- Vis spectrophotometer. Adenosine deaminase is inhibited by these ligands, via different types of inhibition. Allopurinol, as a transition state analog of xanthine oxidase, and acyclovir competitively inhibit the catalytic activity

Ghasem Ataie; Soghra Bagheri; Adeleh Divsalar; Ali Akbar Saboury; Shahrokh Safarian; Saeed Namaki

429

Endogenous adenosine differentially modulates 5-hydroxytryptamine release from a human enterochromaffin cell model  

Microsoft Academic Search

Background & Aims: The aim was to determine whether adenosine receptors modulate cAMP, intracellular free calcium ([Ca2+]i), and 5-hydroxytryptamine (5-HT) release in human carcinoid BON cells.Methods: Adenosine receptor (R) mRNA, proteins, and function were identified by Western blots, immunofluorescent labeling, Fluo-4\\/AM [Ca2+]i imaging, and pharmacologic\\/physiologic techniques. Results: A1, A2, and A3Rs were present in BON cells and carcinoid tumors. Baseline

Fievos L. Christofi; Minsoo Kim; Jacqueline E. Wunderlich; Jianjing Xue; Zach Suntres; Arturo Cardounel; Najma H. Javed; Jun Ge Yu; Iveta Grants; Helen J. Cooke

2004-01-01

430

Pharmacological characterization of the porcine atrial A sub 1 adenosine receptor  

SciTech Connect

The objective of these studies was to increase our understanding of molecular processes involved in ligand interactions with receptors mediating cardioinhibitory effects of adenosine and the interactions of these receptors with guanine nucleotide binding regulatory proteins. Porcine atrial A{sub 1} receptors were characterized using both agonist (N{sup 6}-(3-({sup 125}I)iodo-4-hydroxyphenylisopropyl)adenosine, ({sup 125}I)HPIA) and antagonist (8-cyclopentyl-1,3({sup 3}H)dipropyl-xanthine, ({sup 3}H)DPCPX) radioligands. ({sup 3}H)DPCPX was shown to be the first useful antagonist radioligand for labeling atrial A{sub 1} adenosine receptors. The atrial adenosine receptor displayed two agonist affinity states: a guanine nucleotide-sensitive high affinity state and a guanine nucleotide-insensitive low affinity state. The former was demonstrated to be entirely the result of ternary complex formation in porcine atrial membranes (agonist-receptor-G protein). ({sup 125}I)HPIA labeled a homogeneous population of membrane-bound atrial A{sub 1} adenosine receptors which appeared to exist pre-coupled (in the absence of agonist) to a guanine nucleotide binding protein. Guanine nucleotides negatively modulated ({sup 125}I)HPIA binding by increasing the rate of dissociation of the agonist radioligand, providing direct evidence for ternary complex formation in porcine atrial membranes. Solubilization of atrial adenosine receptors using a mixed detergent system resulted in a 2.5-fold enrichment of adenosine receptor specific activity over that of porcine atrial membrane preparations. Both pharmacological specificity and receptor-G protein interactions were preserved in detergent solution. ({sup 125}I)HPIA interacted via a simple bimolecular reaction with solubilized atrial adenosine receptors that existed precoupled to G protein(s).

Leid, M.E.

1989-01-01

431

Postconditioning protects rabbit hearts through a protein kinase C-adenosine A2b receptor cascade  

Microsoft Academic Search

Objective: Ischemic postconditioning protects the reperfused heart from infarction, and this protection is dependent on the occupancy of adenosine receptors. We further explored the role of adenosine receptors in this salvage. Methods: In situ rabbit hearts underwent 30min of regional ischemia and 3h of reperfusion, and postconditioning was effected with four cycles of 30-s reperfusion\\/30-s coronary artery occlusion at the

Sebastian Philipp; Xi-Ming Yang; Lin Cui; Amanda M. Davis; James M. Downey; Michael V. Cohen

432

The role of adenosine in rat coronary flow regulation during respiratory and metabolic acidosis  

Microsoft Academic Search

The role of adenosine in rat coronary flow regulation during acidosis was evaluated in isolated, perfused, Langendorff rat heart preparations exposed to brief periods of hypercapnic or metabolic acidosis. Acidosis resulted in increases in coronary flow rate, in conjunction with decreases in ventricular contractile tensions. Heart rates were non-significantly increased. Two non-selective adenosine antagonists, caffeine and 8-phenyltheophylline, markedly attenuated the

John W. Phillis; Dekun Song; Michael H. O'Regan

1998-01-01

433

Inhibition of adenosine kinase during oxygen-glucose deprivation in rat cortical neuronal cultures  

Microsoft Academic Search

Adenosine kinase (AK) inhibitors potentiate the actions of endogenous adenosine (ADO) and ameliorate cerebral ischemic damage in animal models. The present study examined the effects of the AK inhibitor, 5-iodotubercidin (5-IT) in an in vitro model of neuronal ischemia, specifically, combined oxygen-glucose deprivation of rat cortical mixed neuronal-glial cultures. Oxygen-glucose deprivation caused extensive neuronal loss which was accompanied by a

James J Lynch III; Karen M Alexander; Michael F Jarvis; Elizabeth A Kowaluk

1998-01-01

434

Structureactivity relationship for the binding of nucleoside ligands to adenosine kinase from Toxoplasma gondii  

Microsoft Academic Search

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

Max H. Iltzsch; Sheri S. Uber; Kevin O. Tankersley; Mahmoud H. el Kouni

1995-01-01

435

Value and limitations of adenosine in the diagnosis and treatment of narrow and broad complex tachycardias  

Microsoft Academic Search

The diagnostic and therapeutic potential of intravenous adenosine was studied in 64 patients during 92 episodes of regular sustained tachycardia. In 40 patients who had narrow complex tachycardias (QRS less than 0.12 s) adenosine (2.5-25 mg) restored sinus rhythm in 25 with junctional tachycardias (46 of 48 episodes) and produced atrioventricular block to reveal atrial or sinus tachycardia in 15.

A C Rankin; K G Oldroyd; E Chong; A P Rae; S M Cobbe

1989-01-01

436

8-Cl-Adenosine Induces Growth Arrest without Differentiation of Primary Mouse Epidermal Keratinocytes  

Microsoft Academic Search

In some cell systems, the antiproliferative effects of 8-Cl-cAMP, a site-selective cAMP analog specific for the type I cAMP-dependent protein kinase, are mediated by its metabolite, 8-Cl-adenosine. These effects were once thought to be specific to transformed cells. We investigated the ability of 8-Cl-adenosine to regulate growth and differentiation in primary cultures of mouse epidermal keratinocytes. A 24 h exposure

Daniel T. Dransfield; Richard D. Griner; Sagarika Ray; Meral Keskintepe; Wendy B. Bollag

2001-01-01

437

Characterization, Distribution, and Ontogenesis of Adenosine Binding Sites in Cat Visual Cortex  

Microsoft Academic Search

In vitro autoradiographic techniques were used to characterize binding sites for 3H-cyclohexyladenosine (CHA) and 3H-5'-IV- ethylcarboxamidoadenosine (NECA) in cat and kitten visual cortex. 3H-CHA binding sites in adult cat have a B,, of 1363 fmol\\/mg protein and a Kd of 6.8 nM. Displacement experiments indicate that 3H-CHA binds to an adenosine receptor similar to the A,-adenosine receptor described by other

C. Shaw; M. Cynader

438

A2A Adenosine Receptor Binding Parameters in Platelets from Patients Affected by Pathological Gambling  

Microsoft Academic Search

Background\\/Aims: A structural and functional interaction between A2A adenosine receptors and D2 dopamine receptors has been implicated in the pathophysiology of impulse control disorders. The aim of this study was to use platelet membranes to assess A2A adenosine receptor affinity and density in patients affected by pathological gambling (PG; which is classified as a specific impulse control disorder) with respect

Claudia Martini; Simona Daniele; Michela Picchetti; Anna Panighini; Marina Carlini; Maria Letizia Trincavelli; Daniela Cesari; Eleonora Da Pozzo; Francesca Golia; Liliana Dell’Osso

2011-01-01

439

Sitagliptin attenuates sympathetic innervation via modulating reactive oxygen species and interstitial adenosine in infarcted rat hearts  

PubMed Central

We investigated whether sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, attenuates arrhythmias through inhibiting nerve growth factor (NGF) expression in post-infarcted normoglycemic rats, focusing on adenosine and reactive oxygen species production. DPP-4 bound adenosine deaminase has been shown to catalyse extracellular adenosine to inosine. DPP-4 inhibitors increased adenosine levels by inhibiting the complex formation. Normoglycemic male Wistar rats were subjected to coronary ligation and then randomized to either saline or sitagliptin in in vivo and ex vivo studies. Post-infarction was associated with increased oxidative stress, as measured by myocardial superoxide, nitrotyrosine and dihydroethidium fluorescent staining. Measurement of myocardial norepinephrine levels revealed a significant elevation in vehicle-treated infarcted rats compared with sham. Compared with vehicle, infarcted rats treated with sitagliptin significantly increased interstitial adenosine levels and attenuated oxidative stress. Sympathetic hyperinnervation was blunted after administering sitagliptin, as assessed by immunofluorescent analysis and western blotting an