Artículos de revistas: "Purines"

1

Balcells, J., J. A. Guada, C. Castrillo y J. Gasa. "Urinary excretion of allantoin and allantoin precursors by sheep after different rates of purine infusion into the duodenum". Journal of Agricultural Science 116, n.º 2 (abril de 1991): 309–17. http://dx.doi.org/10.1017/s002185960007773x.

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SUMMARYTwo experiments were carried out to determine endogenous losses and the response of urinary purine derivatives to increased duodenal inputs of purine bases. Four ewes each fitted with a re-entrant cannula at the proximal duodenum, and conventionally fed, were subjected to full replacement of duodenal digesta followed by the administration of a solution either free of purines (Expt 1) or enriched with increasing amounts of purines, to supply 0·48–21·27 mmol/animal per day (Expt 2). Basal daily urinary excretions of allantoin, uric acid, hypoxanthine and xanthine were 11·5 ± 0·94, 9·9 ± 0·67, 6·9 ± 0·46 and 1·2 ±0·16 mg/kg W0·75. Allantoin was the only purine derivative which increased in response to incremental inputs of duodenal purines. The relationship between allantoin excretion and infused purines showed a urinary recovery of 0·8 for purines infused at > 220 μmol/kg W0·76. Lower rates of infusion did not alter allantoin excretion. The results show urinary allantoin to be a useful index to estimate duodenal input of purines when animals are fed close to or above their energy maintenance requirements.

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2

ZINN, R. A. y F. N. OWENS. "A RAPID PROCEDURE FOR PURINE MEASUREMENT AND ITS USE FOR ESTIMATING NET RUMINAL PROTEIN SYNTHESIS". Canadian Journal of Animal Science 66, n.º 1 (1 de marzo de 1986): 157–66. http://dx.doi.org/10.4141/cjas86-017.

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A rapid method for separation and quantitation of purines was applied to ruminal and intestinal digesta for estimating net microbial protein synthesis in the rumen. The procedure combines standard literature methods for hydrolysis of nucleotides by perchloric acid followed by precipitation of free purines with silver nitrate to separate the purines from interfering compounds. Acid resolubilized purines were quantitated spectrophotometrically at 260 nm. Microbial protein was estimated by the ratio of purines to N of isolated bacteria. The procedure is rapid, simple, precise and not costly. Duodenal passage of microbial N estimated by this procedure for steers fed semipurified and purified diets containing no protein was highly correlated (R2 = 0.98; P < 0.01) with duodenal passage of tungstic acid precipitable N. Results indicate that purines may be useful as a marker for quantitating microbial protein. Key words: Purine, RNA, DNA, microbial protein

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3

Hasník, Zbyněk, Radek Pohl, Blanka Klepetářová y Michal Hocek. "Synthesis of (purin-6-yl)acetates and their transformations to 6-(2-hydroxyethyl)- and 6-(carbamoylmethyl)purines". Collection of Czechoslovak Chemical Communications 74, n.º 7-8 (2009): 1035–59. http://dx.doi.org/10.1135/cccc2009042.

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A novel approach to the synthesis of (purin-6-yl)acetates was developed based on Pd-catalyzed cross-coupling reactions of 6-chloropurines with a Reformatsky reagent. Their reduction with NaBH4 and treatment with MnO2 gave 6-(2-hydroxyethyl)purines, while reactions with amines in presence of NaCN afforded 6-(carbamoylmethyl)purines. Mesylation of the 6-(2-hydroxyethyl)purines followed by nucleophilic substitutions gave rise to several 6-(2-substituted ethyl)purines. This methodology was successfully applied to the synthesis of substituted purine bases and nucleosides for cytostatic and antiviral activity screening. None of the compounds exerted significant activity.

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4

Verbic, J., X. B. Chen, N. A. MacLeod y E. R. Ørskov. "Excretion of purine derivatives by ruminants. Effect of microbial nucleic acid infusion on purine derivative excretion by steers". Journal of Agricultural Science 114, n.º 3 (junio de 1990): 243–48. http://dx.doi.org/10.1017/s0021859600072610.

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SUMMARYTwo steers totally nourished by intragastric infusion of volatile fatty acids and casein were given an abomasal infusion of a microbial protein preparation (Pruteen) at eight rates with a purine input ranging from 0 to 170 mmol/day over 11 successive 5-day periods. The urinary excretion of purine derivatives relative to the purine input was measured. Negligible amounts of xanthine plus hypoxanthine were present in the urine. The relative contributions of allantoin and uric acid to the total excretion were not affected by the rate of purine infusion. Total purine derivative excretion (uric acid and allantoin) was linearly correlated with purine input. Recovery in the urine of the infused purines was 0·77. It is suggested that utilization of exogenous purines may only occur in the intestinal mucosa and that the remaining purines may be completely converted, before entering the liver, to uric acid and allantoin, which are subsequently eliminated by the renal and extrarenal routes. The differences between cattle and sheep in excretion of purine derivatives, and the implications of these differences for the use of purine excretion values in order to estimate microbial protein supply to the ruminant, are discussed.

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5

Pons, F. W., U. Neubert y P. Müller. "Evidence for frameshift mutations in the hisH gene of Escherichia coli causing synthesis of a partially active glutamine amidotransferase." Genetics 120, n.º 3 (1 de noviembre de 1988): 657–65. http://dx.doi.org/10.1093/genetics/120.3.657.

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Abstract Among eight strains carrying acridine-induced mutations in hisH, five which mapped at four different sites in the promoter-distal region of the gene showed His+ phenotypes on media containing a purine. By complementation analysis, hisH enzyme was shown to be required for growth on purines. Purine-sensitive His+ revertants of strains able to grow on purines carried second-site mutations which in one case could be shown to map in hisG. Strains able to grow on purines were able to grow on 2-thiazolyl-DL-alanine, too. We conclude that frameshift mutations in the promoter-distal part of the hisH gene of E. coli do not completely abolish the activity of the gene product.

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6

Hristov, A. N., T. A. McAllister, D. R. Ouellet y G. A. Broderick. "Comparison of purines and nitrogen-15 as microbial flow markers in beef heifers fed barley- or corn-based diets". Canadian Journal of Animal Science 85, n.º 2 (1 de junio de 2005): 211–22. http://dx.doi.org/10.4141/a04-054.

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The objective of this study was to estimate the contribution of microbial purine bases to duodenal purines and to purine derivatives [allantoin and uric acid (PD)] excreted in the urine. Additionally, microbial protein (MCP) flow estimated using duodenal flow of purine bases was compared to estimates using 15N as a microbial marker. Four beef heifers were fed two diets, barley silage/barley grain/soybean meal (diet B) or corn silage/corn grain/corn gluten meal (diet C), in a cross-over design study. (15NH4)2SO4 was infused in the rumen for 8 d to label ruminal microorganisms and their purine bases. Rumen contents, duodenal digesta, urine, and feces were sampled during the last 2 d of tracer infusion and for 48 h after the infusion ceased. The animals consumed more (P < 0.01) dry matter (DM), organic matter (OM), N, and neutral detergent fiber (NDF) with diet B than with diet C. Total tract digestibilities of DM, OM, and NDF were also higher (P < 0.01) with diet B. Ruminal ammonia (P < 0.01), volatile fatty acids (P < 0.05), and acetate (P < 0.01) concentrations and xylanase activity (P < 0.05) were higher with diet B compared with diet C. Flow of MCP to the duodenum was estimated from duodenal samples using purines or 15N as microbial markers, or from urinary PD excretion. The effects of diet or method of measurement on MCP flow were not significant. However, when the urinary PD method was excluded from the analysis, MCP flow was greater (by 26%; P = 0.01) when estimated using 15N vs. the purine-based method. The difference was mainly due to underestimation of the proportion of microbial N in the liquid duodenal digesta with the purine method. Feed purines contributed from 3.5 (liquid digesta phase) to 19.7% (solid digesta phase) of the total purine flow at the duodenum. 15N enrichment of urinary PD was 1.08 of the enrichment of duodenal purines, suggesting that feed purines contributed little N to urinary allantoin and uric acid in cattle. Key words: Allantoin, cattle, microbial protein synthesis, nitrogen-15, purine derivative

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7

Walsh, M. J., A. Sanchez-Pozo y N. S. Leleiko. "A regulatory element is characterized by purine-mediated and cell-type-specific gene transcription". Molecular and Cellular Biology 10, n.º 8 (agosto de 1990): 4356–64. http://dx.doi.org/10.1128/mcb.10.8.4356-4364.1990.

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Purines and purine nucleotides were found to affect transcription of the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene in whole nuclei isolated from intestinal mucosa of adult rats fed a purine- and purine nucleotide-free diet. Nuclear run-on transcription assays, performed on whole nuclei from different tissues and cell types, identified an intestine-specific decrease in the overall incorporation of [alpha-32P]UTP in HPRT transcripts from intestinal epithelial cell nuclei when exogenous purines or purine nucleotides were omitted from either the diet or culture medium. Using a 990-base-pair genomic fragment that contains the 5'-flanking region from the HPRT gene, we generated plasmid constructs with deletions, transfected the DNA into various cell types, and assayed for chloramphenicol acetyltransferase (CAT) reporter activity in vitro. We determined that an element upstream from the putative transcriptional start site is necessary to maintain the regulatory response to purine and nucleotide levels in cultured intestinal epithelial cells. These results were tissue and cell type specific and suggest that in the absence of exogenous purines, the presence of specific factors influences transcriptional initiation of HPRT. This information provides evidence for a mechanism by which the intestinal epithelium, which has been reported to lack constitutive levels of de novo purine nucleotide biosynthetic activity, could maintain and regulate the salvage of purines and nucleotides necessary for its high rate of cell and protein turnover during fluctuating nutritional and physiological conditions. Furthermore, this information may provide more insight into regulation of the broad class of genes recognized by their lack of TATA and CCAAT box consensus sequences within the region proximal to the promoter.

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8

Walsh, M. J., A. Sanchez-Pozo y N. S. Leleiko. "A regulatory element is characterized by purine-mediated and cell-type-specific gene transcription." Molecular and Cellular Biology 10, n.º 8 (agosto de 1990): 4356–64. http://dx.doi.org/10.1128/mcb.10.8.4356.

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Purines and purine nucleotides were found to affect transcription of the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene in whole nuclei isolated from intestinal mucosa of adult rats fed a purine- and purine nucleotide-free diet. Nuclear run-on transcription assays, performed on whole nuclei from different tissues and cell types, identified an intestine-specific decrease in the overall incorporation of [alpha-32P]UTP in HPRT transcripts from intestinal epithelial cell nuclei when exogenous purines or purine nucleotides were omitted from either the diet or culture medium. Using a 990-base-pair genomic fragment that contains the 5'-flanking region from the HPRT gene, we generated plasmid constructs with deletions, transfected the DNA into various cell types, and assayed for chloramphenicol acetyltransferase (CAT) reporter activity in vitro. We determined that an element upstream from the putative transcriptional start site is necessary to maintain the regulatory response to purine and nucleotide levels in cultured intestinal epithelial cells. These results were tissue and cell type specific and suggest that in the absence of exogenous purines, the presence of specific factors influences transcriptional initiation of HPRT. This information provides evidence for a mechanism by which the intestinal epithelium, which has been reported to lack constitutive levels of de novo purine nucleotide biosynthetic activity, could maintain and regulate the salvage of purines and nucleotides necessary for its high rate of cell and protein turnover during fluctuating nutritional and physiological conditions. Furthermore, this information may provide more insight into regulation of the broad class of genes recognized by their lack of TATA and CCAAT box consensus sequences within the region proximal to the promoter.

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9

Safranow, Krzysztof y Zygmunt Machoy. "Methylated Purines in Urinary Stones". Clinical Chemistry 51, n.º 8 (1 de agosto de 2005): 1493–98. http://dx.doi.org/10.1373/clinchem.2005.048033.

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Abstract Background: The aim of the study was to measure the content of methylated purines that appear as admixtures in uric acid stones. Methods: We analyzed urinary calculi from 48 residents of Western Pomerania who underwent surgery at the urology ward in Szczecin. Stone samples were dissolved in 0.1 mol/L NaOH. Extracts were diluted in 50 mmol/L KH2PO4 and analyzed by reversed-phase HPLC with ultraviolet detection and use of a gradient of methanol concentration and pH. Results: Uric acid was the main component of 9 stones. All 9 showed admixtures of 9 other purine derivatives: endogenous purine breakdown products (xanthine, hypoxanthine, and 2,8-dihydroxyadenine) and exogenous methyl derivatives of uric acid and xanthine (1-, 3-, and 7-methyluric acid; 1,3-dimethyluric acid; and 3- and 7-methylxanthine). Amounts of these purine derivatives ranged from the limit of detection to 12 mg/g of stone weight and showed a strong positive correlation (Spearman rank correlation coefficients, 0.63–0.94) with the uric acid content of the samples. The main methylated purine in the stones was 1-methyluric acid. Conclusions: Urinary purines at concentrations below their saturation limits may coprecipitate in samples supersaturated with uric acid and appear as admixtures in urinary stones. The amount of each purine depends on its average urinary excretion, similarity to the chemical structure of uric acid, and concentration of the latter in the stone. These findings suggest that purines in stones represent a substitutional solid solution with uric acid as solvent. Methylxanthines, which are ubiquitous components of the diet, drugs, and uric acid calculi, may be involved in the pathogenesis of urolithiasis.

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10

Burres, Neal S. y Carol E. Cass. "The effects of hypoxanthine on methotrexate-induced differentiation of cultured human choriocarcinoma (BeWo) cells". Biochemistry and Cell Biology 64, n.º 8 (1 de agosto de 1986): 811–15. http://dx.doi.org/10.1139/o86-109.

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When cultured human choriocarcinoma (BeWo) cells arc exposed to methotrexate, proliferation ceases and cells undergo a complex differentiative response that resembles development of normal trophoblast. Although thymidylate starvation has been shown to be causative in methotrexate-induced expression of syncytiotrophoblastic markers by BeWo cells, the role of purine deprivation is uncertain since previous studies utilized growth media containing exogenous purines. This work investigated the effects of hypoxanthine on methotrexate-induced cell enlargement, expression of placental alkaline phosphatase, and morphological differentiation to the syncytiotrophoblast-like phenotype. When methotrexate exposures (1 μM, 48 h) were conducted in a purine-frec basal medium supplemented with dialyzed fetal bovine serum, RNA synthesis was greatly reduced and cell enlargement did not occur. Specific methods for removing purines (charcoal extraction and xanthine oxidase treatment) decreased the ability of serum to support cell enlargement during methotrexate exposures, whereas addition of hypoxanthine to culture fluids restored its ability to support maximal increases in cell mass, confirming that purines were the factors lost during dialysis. In contrast, morphological differentiation to the syncytiotrophoblast-like phenotype and increased expression of placental alkaline phosphatase were unaffected by the availability of purines during exposure to methotrexate.

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11

Cicero, Arrigo F. G., Federica Fogacci, Valentina Di Micoli, Cristina Angeloni, Marina Giovannini y Claudio Borghi. "Purine Metabolism Dysfunctions: Experimental Methods of Detection and Diagnostic Potential". International Journal of Molecular Sciences 24, n.º 8 (10 de abril de 2023): 7027. http://dx.doi.org/10.3390/ijms24087027.

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Purines, such as adenine and guanine, perform several important functions in the cell. They are found in nucleic acids; are structural components of some coenzymes, including NADH and coenzyme A; and have a crucial role in the modulation of energy metabolism and signal transduction. Moreover, purines have been shown to play an important role in the physiology of platelets, muscles, and neurotransmission. All cells require a balanced number of purines for growth, proliferation, and survival. Under physiological conditions, enzymes involved in purines metabolism maintain a balanced ratio between their synthesis and degradation in the cell. In humans, the final product of purine catabolism is uric acid, while most other mammals possess the enzyme uricase that converts uric acid to allantoin, which can be easily eliminated with urine. During the last decades, hyperuricemia has been associated with a number of human extra-articular diseases (in particular, the cardiovascular ones) and their clinical severity. In this review, we go through the methods of investigation of purine metabolism dysfunctions, looking at the functionality of xanthine oxidoreductase and the formation of catabolites in urine and saliva. Finally, we discuss how these molecules can be used as markers of oxidative stress.

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12

Li, Tingting, Likun Ren, Dangfeng Wang, Minjie Song, Qiuying Li y Jianrong Li. "Optimization of extraction conditions and determination of purine content in marine fish during boiling". PeerJ 7 (6 de mayo de 2019): e6690. http://dx.doi.org/10.7717/peerj.6690.

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Background Gout is the second most common metabolic disease affecting human health. The disease of gout is closely related to the level of uric acid, which is the end-product of human purine metabolism. Moreover, food is the main way of external ingestion of purine. Method A simple and time-saving method was developed to extract purines like adenine, hypoxanthine, guanine, and xanthine from marine fish by single factor design combined with Box–Behnken. The contents of these purines in the edible parts and internal organs of marine fish, as well as Scophthalmus maximus, were determined by high-performance liquid chromatography to investigate the relationship between the boiling process and purine content. Result The mixed-acid method was chosen for the extraction of purine bases and the extraction conditions were as follows: mixture acid 90.00% TFA/80.00% FA (v/v, 1:1); hydrolysis temperature 90.00 °C; time 10.00 min; liquid-to-solid ratio 30:1. The total purine content of the edible parts (eyes, dorsal muscles, abdominal muscles, and skin) was the highest in Scophthalmus maximus, followed by sphyraena, Sardinella, Trichiurus lepturus, Scomberomorus niphonius, Pleuronectiformes, Sea catfish, Anguillidae, and Rajiformes. Moreover, boiling significantly reduced the purine content in the marine fish because of the transfer of the purines to the cooking liquid during boiling. Scophthalmus maximus, Sphyraena, and Sardinella were regard as high-purine marine fish, which we should eat less. We also confirmed that boiling significantly transferred purine bases from fish to cooking liquid. Thus, boiling could reduce the purine content of fish, thereby reducing the risk of hyperuricemia and gout.

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13

Chen, X. B., F. D. DeB Hovell, E. R. Ørskov y D. S. Brown. "Excretion of purine derivatives by ruminants: effect of exogenous nucleic acid supply on purine derivative excretion by sheep". British Journal of Nutrition 63, n.º 1 (enero de 1990): 131–42. http://dx.doi.org/10.1079/bjn19900098.

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The present study examined the relationship between the supply of exogenous nucleic acid (NA) purines and their recovery as the derivatives hypoxanthine, xanthine, uric acid and allantoin in urine. Six lambs, totally nourished by intragastric infusions of volatile fatty acids (VFA) and casein (i.e. no rumen fermentation), were given by abomasal infusion a microbial NA concentrate at six levels (from zero to 24·5 mmol purines/d). The true digestibility between the abomasum and terminal ileum of the NA purines was measured in a separate experiment using three lambs. The relative proportion of urinary allantoin increased, and that of other derivatives decreased, as the amount of NA infused was increased. The relationship between total excretion of purine derivatives (Y; mmol/d) and exogenous purines absorbed (X; mmol/d) was Y = 0·84 X + 0.150W0·75e-0.25X, where W is body-weight (kg). This implies that the endogenous contribution to the total excretion of derivative decreased as the supply of exogenous purines increased, with an associated progressive replacement of de novo synthesis by exogenous purines. The model also implies that 0·16 of the purines were eliminated through routes other than derivative excretion in urine. Once excretion exceeded 0·6 mmol/kg W0·75 per d, endogenous excretion was effectively zero and thus Y = 0·84 X. In normally fed sheep, derivative excretion should therefore relate to the microbial purines and, hence, microbial protein absorbed according to these models. The changing proportions of allantoin and other derivatives in urine were probably due to changes in the relative importance of endogenous and exogenous purines as precursors.

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14

Li, Luyong, Jie Hu, Yuqing Fu, Xiaolin Shi, Hongguang Du, Jiaxi Xu y Ning Chen. "Direct Regioselective C-H Cyanation of Purines". Molecules 28, n.º 3 (17 de enero de 2023): 914. http://dx.doi.org/10.3390/molecules28030914.

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A direct regioselective C-H cyanation of purines was developed through a sequential triflic anhydride activation, nucleophilic cyanation with TMSCN, followed by a process of base-mediated elimination of triflous acid (CF3SO2H). In most cases, the direct C-H cyanation occurred on the electron-rich imidazole motif of purines, affording 8-cyanated purine derivatives in moderate to excellent yields. Various functional groups, including allyl, alkynyl, ketone, ester, nitro et al. were tolerated and acted as a C8 directing group. The electron-donating 6-diethylamino, as C2-directing group substituent, can switch the regioselectivity of purine from 8- to 2-position, enabling the synthesis of 8- and 2-cyano 6-dialkylaminopurines from corresponding 6-chloropurine in different reaction order. Further functional manipulations of the cyano group allow the conversions of 8-cyanopurines to corresponding purine amides, imidates, imidothioates, imidamides, oxazolines, and isothiazoles.

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15

Enchev, Venelin y Sofia Slavova. "Self-catalytic mechanism of prebiotic reactions: from formamide to pterins and guanine". Physical Chemistry Chemical Physics 23, n.º 34 (2021): 19043–53. http://dx.doi.org/10.1039/d1cp02158c.

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16

Boerth, Donald W. y Pradip K. Bhowmik. "Protonation-deprotonation of purines and purine nucleosides". Journal of Molecular Structure: THEOCHEM 183, n.º 3-4 (enero de 1989): 381–92. http://dx.doi.org/10.1016/0166-1280(89)80018-1.

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17

Zuccarini, Mariachiara, Patricia Giuliani, Francesco Caciagli, Renata Ciccarelli y Patrizia Di Iorio. "In Search of a Role for Extracellular Purine Enzymes in Bone Function". Biomolecules 11, n.º 5 (30 de abril de 2021): 679. http://dx.doi.org/10.3390/biom11050679.

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Bone is one of the major tissues that undergoes continuous remodeling throughout life, thus ensuring both organic body growth during development and protection of internal organs as well as repair of trauma during adulthood. Many endogenous substances contribute to bone homeostasis, including purines. Their role has increasingly emerged in recent decades as compounds which, by interacting with specific receptors, can help determine adequate responses of bone cells to physiological or pathological stimuli. Equally, it is recognized that the activity of purines is closely dependent on their interconversion or metabolic degradation ensured by a series of enzymes present at extracellular level as predominantly bound to the cell membrane or, also, as soluble isoforms. While the effects of purines mediated by their receptor interactions have sufficiently, even though not entirely, been characterized in many tissues including bone, those promoted by the extracellular enzymes providing for purine metabolism have not been. In this review, we will try to circumstantiate the presence and the role of these enzymes in bone to define their close relationship with purine activities in maintaining bone homeostasis in normal or pathological conditions.

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18

Karwatowska-Prokopczuk, E., G. Ciabattoni y A. Wennmalm. "Effects of hydrodynamic forces on coronary production of prostacyclin and purines". American Journal of Physiology-Heart and Circulatory Physiology 256, n.º 6 (1 de junio de 1989): H1532—H1538. http://dx.doi.org/10.1152/ajpheart.1989.256.6.h1532.

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Prostacyclin and purine efflux rates from the isolated rabbit heart in response to variations of flow rate or perfusion pressure were investigated. Increases in coronary flow by 25, 50, and 100% augmented the effluxes of 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) and purines equally, by up to four times. Increases in coronary pressure by 25, 50, and 100% augmented the outflow of 6-keto-PGF1 alpha by up to 20 times, whereas the outflow of purines increased no more than 6.5 times. Neither reduction of perfusate Ca2+ by 50% nor administration of quinacrine (1 microM) affected the basal efflux of 6-keto-PGF1 alpha or its response to an increase in coronary pressure. Both interventions did, however, reduce the pressure-induced purine efflux by approximately 50%. Pulsatile flow did not affect either the outflow of 6-keto-PGF1 alpha or that of purines, in comparison to steady flow at the same rate. The data demonstrate that an increase in coronary pressure activates a specific mechanism for prostacyclin production that appears independent of extracellular Ca2+ and of phospholipase activity.

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Párkányi, Cyril, Christian Boniface, Jean-Jacques Aaron, Mihaela Bulaceanu-MacNair y Marwan Dakkouri. "Theoretical and Experimental Dipole Moments of Purines". Collection of Czechoslovak Chemical Communications 67, n.º 8 (2002): 1109–24. http://dx.doi.org/10.1135/cccc20021109.

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As a follow-up on our previous study of a series of purines (purine, 6-chloropurine, purine-6-thiol, hypoxanthine, theobromine, theophylline, caffeine, and uric acid), we have investigated six additional biologically important purines (adenine, guanine, isoguanine, thioguanine, xanthine, and kinetin). Their ground-state dipole moments were measured in dioxane at 293 K. The first excited singlet-state dipole moments were obtained using the solvatochromic shift equations (McRae, Suppan, Bakhshiev, and Kawski-Chamma-Viallet). The theoretical dipole moments were calculated as a combination of the π-moment (PPP method) and the σ-moment (vector sum of the σ-bond and σ-group moments). The same approach was used to obtain their first excited singlet-state dipole moments (excited state π-moment; σ-moment assumed to be the same as in the ground state). Ab initio HF 6-31G** calculations were also used to obtain ground-state dipole moments for all the fourteen purines under study. In addition, a DFT/B3PW91/6311++(2df,2p) calculation has been carried out for purine for comparison. The different sets of theoretical dipole moments were compared with the respective experimental values. There is an approximately equally good agreement among the experimental dipole moments and the PPP + σ dipole moments (±6.9%) and the ab initio dipole moments (±7.4%). The effect of structure on the dipole moments is discussed.

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20

Makkar, H. P. S. y K. Becker. "Purine quantification in digesta from ruminants by spectrophotometric and HPLC methods". British Journal of Nutrition 81, n.º 2 (febrero de 1999): 107–12. http://dx.doi.org/10.1017/s0007114599000227.

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The method of Zinn & Owens (1986;Canadian Journal of Animal Science66, 157–166), based on release of purine bases by HClO4followed by their precipitation with AgNO3, was used to study recovery of purines from lyophilized rumen microbial orEscherichia colipreparations added to matrices such as cellulose, starch and neutral-detergent fibre. The recovery of purines was poor (approximately 50 %). Under the hydrolysis conditions (12 M-HClO4, 90–95° for 1 h) used in the method of Zinn & Owens (1986), the recovery of purines from the rumen microbial preparations added to matrices measured using an HPLC method was 95–102 %, suggesting that the lower recovery of purines in the method of Zinn & Owens (1986) was not due to incomplete hydrolysis of nucleic acids. Using the HPLC method, adenine and allopurinol (an internal standard) were found to be heat-labile as substantial destruction was observed on heating at 121°. On the other hand, another commonly used internal standard, caffeine, was stable at 121°. A complete hydrolysis of nucleic acids from the rumen microbial preparation was observed with 2·5 ml 0·6 M-HClO4in a total volume of 3 ml (0·5 M-HClO4during hydrolysis) at 90–95° for 1 h, and under these conditions adenine, guanine, allopurinol and caffeine were stable. Moreover, under these milder hydrolysis conditions, the recovery of purine bases from the rumen microbial orE. colipreparations added to matrices ranged from 92 to 108 % using the method of Zinn & Owens (1986). Based on the results, changes in hydrolysis conditions have been proposed for accurate determination of purine bases using spectrophotometric or HPLC methods.

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21

Itakura, M., N. Maeda y K. Yamashita. "Increased rate of purine biosynthesis in rat liver after bilateral adrenalectomy". American Journal of Physiology-Endocrinology and Metabolism 251, n.º 4 (1 de octubre de 1986): E373—E378. http://dx.doi.org/10.1152/ajpendo.1986.251.4.e373.

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In bilaterally adrenalectomized rat liver the increased rate of de novo purine synthesis was shown by the increased [14C]glycine incorporation into hepatic acid-soluble purines with unchanged rapidly miscible glycine pool size and its turnover rate and by the increased rate of chasing of radiolabeled purines. At 24 h after adrenalectomy, the rate of de novo purine synthesis increased by 70%, 5-phosphoribosyl-1-pyrophosphate (PRPP) content increased by 200%, the specific activity of amidophosphoribosyltransferase (EC 2.4.2. 14; ATase) did not change, ATP and GTP showed a 33 and 24% decrease, and AMP and ADP showed a 245 and 38% increase. Combined, the metabolic pool size data reflected an unchanged total inhibitory potential on ATase. Replacement with corticosterone acetate for 24 h partially restored some of these abnormalities. These results suggest that the increase in the rate of de novo purine synthesis in adrenalectomized rat liver is secondary to increased catabolism of purine ribonucleotides and mediated by increased PRPP concentrations.

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22

Tomlinson, Patricia Tolson y Carol J. Lovatt. "Nucleotide Metabolism in ‘Washington’ Navel Orange Fruit: I. Pathways of Synthesis and Catabolism". Journal of the American Society for Horticultural Science 112, n.º 3 (mayo de 1987): 529–35. http://dx.doi.org/10.21273/jashs.112.3.529.

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Abstract The capacity of ‘Washington’ navel orange fruit [Citrus sinensis (L.) Osbeck] to synthesize and catabolize purines and pyrimidines was assessed. De novo biosynthesis of purine nucleotide was demonstrated by [14C] bicarbonate incorporation into purine nucleotides, blockage of this process by four known inhibitors, and assimilation of radiolabeled carbon from formate, both carbons of glycine, and carbon-3 of serine into the adenine ring. De novo synthesis of pyrimidines via the orotate pathway in young fruit was demonstrated by incorporation of [14C] bicarbonate and [6-14C]orotic acid into uridine nucleotides, release of 14CO2 from [7-14C]orotic acid, and blockage of these processes by 6-azauridine. Synthesis of purine and pyrimidine nucleotides via salvage reactions was demonstrated by incorporation of radiolabeled bases and ribonucleosides into nucleotides and into nucleic acids. Release of 14CO2 from radiolabeled adenine, adenosine, hypoxanthine, and xanthine, uric acid, urea (purines), uracil, and uridine (pyrimidines) provided evidence the pathways for catabolism (degradation) of purines and pyrimidines in navel orange fruit are similar to those found in microorganisms and animal tissues. To the best of our knowledge, this report is the first to assess the capacity of anabolic and catabolic pathways of purine and pyrimidine nucleotide metabolism in fruit of any species. De novo synthetic activities in orange fruit permit increases in the pools of purine and pyrimidine nucleotides using simple precursors. Further, the patterns of salvage and catabolism suggest riboside pools are reused predominantly as nucleotides, while the majority of base pools are degraded to permit recycling of carbon and nitrogen into other metabolites.

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23

Stentoft, Charlotte, Betina Amdisen Røjen, Søren Krogh Jensen, Niels B. Kristensen, Mogens Vestergaard y Mogens Larsen. "Absorption and intermediary metabolism of purines and pyrimidines in lactating dairy cows". British Journal of Nutrition 113, n.º 4 (26 de enero de 2015): 560–73. http://dx.doi.org/10.1017/s0007114514004000.

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About 20 % of ruminal microbial N in dairy cows derives from purines and pyrimidines; however, their intermediary metabolism and contribution to the overall N metabolism has sparsely been described. In the present study, the postprandial patterns of net portal-drained viscera (PDV) and hepatic metabolism were assessed to evaluate purine and pyrimidine N in dairy cows. Blood was sampled simultaneously from four veins with eight hourly samples from four multi-catheterised Holstein cows. Quantification of twenty purines and pyrimidines was performed with HPLC–MS/MS, and net fluxes were estimated across the PDV, hepatic tissue and total splanchnic tissue (TSP). Concentration differences between veins of fifteen purine and pyrimidine nucleosides (NS), bases (BS) and degradation products (DP) were different from zero (P≤ 0·05), resulting in the net PDV releases of purine NS (0·33–1·3 mmol/h), purine BS (0·0023–0·018 mmol/h), purine DP (7·0–7·8 mmol/h), pyrimidine NS (0·30–2·8 mmol/h) and pyrimidine DP (0·047–0·77 mmol/h). The hepatic removal of purine and pyrimidine was almost equivalent to the net PDV release, resulting in no net TSP release. One exception was uric acid (7·9 mmol/h) from which a large net TSP release originated from the degradation of purine NS and BS. A small net TSP release of the pyrimidine DP β-alanine and β-aminoisobutyric acid ( − 0·032 to 0·37 mmol/h) demonstrated an outlet of N into the circulating N pool. No effect of time relative to feeding was observed (P>0·05). These data indicate that considerable amounts of N are lost in the dairy cow due to prominent intermediary degradation of purines, but that pyrimidine N is reusable to a larger extent.

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24

Szyk, Piotr, Beata Czarczynska-Goslinska, Dariusz T. Mlynarczyk, Barbara Ślusarska, Tomasz Kocki, Marta Ziegler-Borowska y Tomasz Goslinski. "Polymer-Based Nanoparticles as Drug Delivery Systems for Purines of Established Importance in Medicine". Nanomaterials 13, n.º 19 (26 de septiembre de 2023): 2647. http://dx.doi.org/10.3390/nano13192647.

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Many purine derivatives are active pharmaceutical ingredients of significant importance in the therapy of autoimmune diseases, cancers, and viral infections. In many cases, their medical use is limited due to unfavorable physicochemical and pharmacokinetic properties. These problems can be overcome by the preparation of the prodrugs of purines or by combining these compounds with nanoparticles. Herein, we aim to review the scientific progress and perspectives for polymer-based nanoparticles as drug delivery systems for purines. Polymeric nanoparticles turned out to have the potential to augment antiviral and antiproliferative effects of purine derivatives by specific binding to receptors (ASGR1—liver, macrophage mannose receptor), increase in drug retention (in eye, intestines, and vagina), and permeation (intranasal to brain delivery, PEPT1 transport of acyclovir). The most significant achievements of polymer-based nanoparticles as drug delivery systems for purines were found for tenofovir disoproxil in protection against HIV, for acyclovir against HSV, for 6-mercaptopurine in prolongation of mice ALL model life, as well as for 6-thioguanine for increased efficacy of adoptively transferred T cells. Moreover, nanocarriers were able to diminish the toxic effects of acyclovir, didanosine, cladribine, tenofovir, 6-mercaptopurine, and 6-thioguanine.

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25

Sudhakar Rao, T. y Ganapathi R. Revankar. "Synthesis of certain alkenyl purines and purine analogs". Journal of Heterocyclic Chemistry 32, n.º 3 (mayo de 1995): 1043–49. http://dx.doi.org/10.1002/jhet.5570320362.

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26

He, Z., M. Zhao, C. Y. Wang, L. Sun, Y. Y. Jiang y Y. Feng. "Purine and uric acid contents of common edible insects in Southwest China". Journal of Insects as Food and Feed 5, n.º 4 (25 de octubre de 2019): 293–99. http://dx.doi.org/10.3920/jiff2018.0023.

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Edible insects have recently been considered as a potential food source that may solve problems of malnutrition and starvation worldwide. However, studies exploring insects as food sources are mainly focused on entomophagy and nutrition rather than the potential risks of excessive metabolite contents, such as purine and uric acid. In this study, we analysed guanine, hypoxanthine, xanthine, adenine and uric acid concentrations in 11 species of edible insects from Yunnan and Guizhou provinces in Southwest China, including 5 species of dragonfly, 3 species of wasp and a single species of locust, mealworm and silkworm. Purine and uric acid contents differed distinctly between these insects, and guanine and xanthine were the dominant purines in all samples. The proportions of 4 purines in the total purine content of these insects differed markedly from those in meat samples from poultry and livestock, and uric acid contents varied significantly between aquatic insects and terricolous insects, such as silkworm pupa. Taken together, the present data show that most edible insects are potent food sources of purine.

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27

Tullson, P. C., J. Bangsbo, Y. Hellsten y E. A. Richter. "IMP metabolism in human skeletal muscle after exhaustive exercise". Journal of Applied Physiology 78, n.º 1 (1 de enero de 1995): 146–52. http://dx.doi.org/10.1152/jappl.1995.78.1.146.

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This study addressed whether AMP deaminase (AMPD)myosin binding occurs with deamination during intense exercise in humans and the extent of purine loss from muscle during the initial minutes of recovery. Male subjects performed cycle exercise (265 +/- 2 W for 4.39 +/- 0.04 min) to stimulate muscle inosine 5'-monophosphate (IMP) formation. After exercise, blood flow to one leg was occluded. Muscle biopsies (vastus lateralis) were taken before and 3.6 +/- 0.2 min after exercise from the occluded leg and 0.7 +/- 0.0, 1.1 +/- 0.0, and 2.9 +/- 0.1 min postexercise in the nonoccluded leg. Exercise activated AMPD; at exhaustion IMP was 3.5 +/- 0.4 mmol/kg dry muscle. Before exercise, 16.0 +/- 1.6% of AMPD cosedimented with the myosin fraction; the extent of AMPD:myosin binding was unchanged by exercise. Inosine content increased about threefold during exercise and twofold more during recovery; by 2.9 min postexercise it was 0.43 +/- 0.02 mmol/kg dry muscle. IMP decreased 2.1 +/- 0.3 mmol/kg dry muscle with no change in total adenylates. Total purines declined significantly (P < 0.05) during the recovery period in the nonoccluded leg, consistent with a loss of purines to the circulation, whereas total purines were unchanged in the occluded leg. Regulation of muscle purine content is a dynamic process that must accommodate rapid changes due to degradation and efflux.

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28

Logan, Samantha R., Mark Seegobin, R. J. Neil Emery y Craig R. Brunetti. "Components of the Nucleotide Salvage Pathway Increase Frog Virus 3 (FV3) Replication". Viruses 15, n.º 8 (10 de agosto de 2023): 1716. http://dx.doi.org/10.3390/v15081716.

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Viruses are obligate intracellular parasites that alter host metabolic machinery to obtain energy and macromolecules that are pivotal for replication. Ranavirus, including the type species of the genus frog virus 3 (FV3), represent an ecologically important group of viruses that infect fish, amphibians, and reptiles. It was established that fatty acid synthesis, glucose, and glutamine metabolism exert roles during iridovirus infections; however, no information exists regarding the role of purine metabolism. In this study, we assessed the impact of exogenously applied purines adenine, adenosine, adenosine 5′-monophosphate (AMP), inosine 5′-monophosphate (IMP), inosine, S-adenosyl-L-homocysteine (SAH), and S-adenosyl-L-methionine (SAM) on FV3 replication. We found that all compounds except for SAH increased FV3 replication in a dose-dependent manner. Of the purines investigated, adenine and adenosine produced the most robust response, increasing FV3 replication by 58% and 51%, respectively. While all compounds except SAH increased FV3 replication, only adenine increased plaque area. This suggests that the stimulatory effect of adenine on FV3 replication is mediated by a mechanism that is at least in part independent from the other compounds investigated. Our results are the first to report a response to exogenously applied purines and may provide insight into the importance of purine metabolism during iridoviral infection.

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29

Herrera Gomez, F., F. D. Deb Hovell y C. A. Sandoval Castro. "Urinary recovery of allantoin in normally fed steers". Proceedings of the British Society of Animal Science 1998 (1998): 80. http://dx.doi.org/10.1017/s1752756200597324.

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Studies in the use of the purine derivatives technique in ruminants have been stimulated by the possible use of this technique as an estimator of the rumen microbial-N supplied to the host animal. The recovery factor influences the estimation of the total purines absorbed and therefore the microbial-N supply. The relationship between exogenous purine input and urinary excretion and recovery has been studied using cattle maintained with the intragastric infusion technique (Orskov et al., 1979). The urinary recovery of exogenous purines has been estimated to be 0.77-0.85 (Chen et al., 1990a, Verbic et al., 1990), and this relationship has been assumed to be applicable to normal feeding situations. To our knowledge there is no data to support or reject this approach. This study examined the urinary recovery of exogenous allantoin input in steers under normal feeding conditions.

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30

Herrera Gomez, F., F. D. Deb Hovell y C. A. Sandoval Castro. "Urinary recovery of allantoin in normally fed steers". Proceedings of the British Society of Animal Science 1998 (1998): 80. http://dx.doi.org/10.1017/s0308229600032931.

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Studies in the use of the purine derivatives technique in ruminants have been stimulated by the possible use of this technique as an estimator of the rumen microbial-N supplied to the host animal. The recovery factor influences the estimation of the total purines absorbed and therefore the microbial-N supply. The relationship between exogenous purine input and urinary excretion and recovery has been studied using cattle maintained with the intragastric infusion technique (Orskov et al., 1979). The urinary recovery of exogenous purines has been estimated to be 0.77-0.85 (Chen et al., 1990a, Verbic et al., 1990), and this relationship has been assumed to be applicable to normal feeding situations. To our knowledge there is no data to support or reject this approach. This study examined the urinary recovery of exogenous allantoin input in steers under normal feeding conditions.

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31

Gallagher, P. E. y N. J. Duker. "Detection of UV purine photoproducts in a defined sequence of human DNA". Molecular and Cellular Biology 6, n.º 2 (febrero de 1986): 707–9. http://dx.doi.org/10.1128/mcb.6.2.707-709.1986.

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The UV-irradiated, 3'-end-labeled, 92-base-pair terminus of the human alphoid sequence was incubated with purified endonuclease v. Previously unreported photoproducts were incised at purine loci. These were not pyrimidine photodimers, 6-4'-(pyrimidin-2'-one)-pyrimidines, base loss sites, or ring-opened purines. Therefore, purine-containing photoproducts, possibly dimers, were incised by the enzyme preparation.

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32

Gallagher, P. E. y N. J. Duker. "Detection of UV purine photoproducts in a defined sequence of human DNA." Molecular and Cellular Biology 6, n.º 2 (febrero de 1986): 707–9. http://dx.doi.org/10.1128/mcb.6.2.707.

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The UV-irradiated, 3'-end-labeled, 92-base-pair terminus of the human alphoid sequence was incubated with purified endonuclease v. Previously unreported photoproducts were incised at purine loci. These were not pyrimidine photodimers, 6-4'-(pyrimidin-2'-one)-pyrimidines, base loss sites, or ring-opened purines. Therefore, purine-containing photoproducts, possibly dimers, were incised by the enzyme preparation.

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33

Jin, Wei Jun, Hai Rong Zhang, Xin Yang y Chang Song Liu. "Comparison of Room-Temperature Phosphorescence Properties of Three Purine Compounds with Cadmium Acetate as a Source of Heavy Atom Perturbation". Applied Spectroscopy 49, n.º 3 (marzo de 1995): 320–23. http://dx.doi.org/10.1366/0003702953963481.

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Cadmium acetate salts can greatly enhance room-temperature phosphorescence (RTP) of purine and 6-mercaptopurine. 6-Mercapto-substituent and 6-hydroxy-substituent appear quite different in their effect on the RTP of purine. The effects of cadium salt matrix and pH on the RTP of purine compounds were also investigated in detail. With cadmium acetate as a source of heavy atom perturbation, nanogram or subnanogram amounts of purines can be detected.

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34

Harnden, M. R. y L. J. Jennings. "Antiviral 9-[2-(Phosphonomethylthio)Alkoxy]purines". Antiviral Chemistry and Chemotherapy 4, n.º 4 (agosto de 1993): 215–27. http://dx.doi.org/10.1177/095632029300400404.

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A series of 9-[2-(phosphonomethylthio)alkoxy]purine analogues of recently reported antiviral 9-[2-(phosphonomethoxy)alkoxy]purines (Duckworth et al., 1991) has been prepared and evaluated as antiviral agents. 9–[2-(Phosphonomethylthio)ethoxy]guanine (8) has potent activity against herpesviruses, and (R)-9-[3-hydroxy-2-(phosphonomethylthio)propoxy]guanine (37) has potent and selective activity against visna virus and good activity against HIV-1.

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35

Xu, Zhongnan, Yuqing Wang, Yucheng Zheng, Zhixing Huang, Lutz Ackermann y Zhixiong Ruan. "Manganese- and rhenium-catalyzed C–H enaminylation: expedient access to novel indole–purine hybrids with anti-tumor bioactivities". Organic Chemistry Frontiers 7, n.º 22 (2020): 3709–14. http://dx.doi.org/10.1039/d0qo01120g.

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The C–H enaminylation of novel 6-(1H-indol-1-yl)-purines with ketenimines was accomplished by means of aqueous manganese and rhenium catalysis, which sets the stage for the facile synthesis of indole–purine hybrids with anti-tumor bioactivities.

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36

Hintze, Bradley J., Jane S. Richardson y David C. Richardson. "Mismodeled purines: implicit alternates and hidden Hoogsteens". Acta Crystallographica Section D Structural Biology 73, n.º 10 (1 de octubre de 2017): 852–59. http://dx.doi.org/10.1107/s2059798317013729.

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Hoogsteen base pairs are seen in DNA crystal structures, but only rarely. This study tests whether Hoogsteens or othersynpurines are either under-modeled or over-modeled, which are known problems for rare conformations. Candidate purines needing asyn/anti180° flip were identified by diagnostic patterns of difference electron-density peaks. Manual inspection narrowed 105 flip candidates to 20 convincing cases, all at ≤2.7 Å resolution. Rebuilding and refinement confirmed that 14 of these were authentic purine flips. Seven examples are modeled as Watson–Crick base pairs but should be Hoogsteens (commonest at duplex termini), and three had the opposite issue.Syn/antiflips were also needed for some single-stranded purines. Five of the 20 convincing cases arose from an unmodeled alternate duplex running in the opposite direction. These are in semi-palindromic DNA sequences bound by a homodimeric protein and show flipped-purine-like difference peaks at residues where the palindrome is imperfect. This study documents types of incorrect modeling which are worth avoiding. However, the primary conclusions are that such mistakes are infrequent, the bias towards fittingantipurines is very slight, and the occurrence rate of Hoogsteen base pairs in DNA crystal structures remains unchanged from earlier estimates at ∼0.3%.

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37

Xi, Hualin, Barbara L. Schneider y Larry Reitzer. "Purine Catabolism in Escherichia coliand Function of Xanthine Dehydrogenase in Purine Salvage". Journal of Bacteriology 182, n.º 19 (1 de octubre de 2000): 5332–41. http://dx.doi.org/10.1128/jb.182.19.5332-5341.2000.

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ABSTRACT Escherichia coli is not known to utilize purines, other than adenine and adenosine, as nitrogen sources. We reinvestigated purine catabolism because a computer analysis suggested several potential ς54-dependent promoters within a 23-gene cluster whose products have homology to purine catabolic enzymes. Our results did not provide conclusive evidence that the ς54-dependent promoters are active. Nonetheless, our results suggest that some of the genes are metabolically significant. We found that even though several purines did not support growth as the sole nitrogen source, they did stimulate growth with aspartate as the nitrogen source. Cells produced 14CO2 from minimal medium containing [14C]adenine, which implies allantoin production. However, neither ammonia nor carbamoyl phosphate was produced, which implies that purine catabolism is incomplete and does not provide nitrogen during nitrogen-limited growth. We constructed strains with deletions of two genes whose products might catalyze the first reaction of purine catabolism. Deletion of one eliminated 14CO2 production from [14C]adenine, which implies that its product is necessary for xanthine dehydrogenase activity. We changed the name of this gene to xdhA. The xdhA mutant grew faster with aspartate as a nitrogen source. The mutant also exhibited sensitivity to adenine, which guanosine partially reversed. Adenine sensitivity has been previously associated with defective purine salvage resulting from impaired synthesis of guanine nucleotides from adenine. We propose that xanthine dehydrogenase contributes to this purine interconversion.

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38

Jain, Sunny, Selina Sutchu, Patricia A. Rosa, Rebecca Byram y Mollie W. Jewett. "Borrelia burgdorferi Harbors a Transport System Essential for Purine Salvage and Mammalian Infection". Infection and Immunity 80, n.º 9 (18 de junio de 2012): 3086–93. http://dx.doi.org/10.1128/iai.00514-12.

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ABSTRACTBorrelia burgdorferiis the tick-borne bacterium that causes the multistage inflammatory disease Lyme disease.B. burgdorferihas a reduced genome and lacks the enzymes required forde novosynthesis of purines for synthesis of RNA and DNA. Therefore, this obligate pathogen is dependent upon the tick vector and mammalian host environments for salvage of purine bases for nucleic acid biosynthesis. This pathway is vital forB. burgdorferisurvival throughout its infectious cycle, as key enzymes in the purine salvage pathway are essential for the ability of the spirochete to infect mice and critical for spirochete replication in the tick. The transport of preformed purines into the spirochete is the first step in the purine salvage pathway and may represent a novel therapeutic target and/or means to deliver antispirochete molecules to the pathogen. However, the transport systems critical for purine salvage byB. burgdorferihave yet to be identified. Herein, we demonstrate that the genesbbb22andbbb23, present onB. burgdorferi's essential plasmid circular plasmid 26 (cp26), encode key purine transport proteins. BBB22 and/or BBB23 is essential for hypoxanthine transport and contributes to the transport of adenine and guanine. Furthermore,B. burgdorferilackingbbb22-23was noninfectious in mice up to a dose of 1 × 107spirochetes. Together, our data establish thatbbb22-23encode purine permeases critical forB. burgdorferimammalian infectivity, suggesting that this transport system may serve as a novel antimicrobial target for the treatment of Lyme disease.

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39

Morningstar, Jordan, Jangwoen Lee, Sari Mahon, Matthew Brenner y Anjali K. Nath. "Mass Spectrometric Analysis of Purine Intermediary Metabolism Indicates Cyanide Induces Purine Catabolism in Rabbits". Metabolites 14, n.º 5 (10 de mayo de 2024): 279. http://dx.doi.org/10.3390/metabo14050279.

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Purines are the building blocks of DNA/RNA, energy substrates, and cofactors. Purine metabolites, including ATP, GTP, NADH, and coenzyme A, are essential molecules in diverse biological processes such as energy metabolism, signal transduction, and enzyme activity. When purine levels increase, excess purines are either recycled to synthesize purine metabolites or catabolized to the end product uric acid. Purine catabolism increases during states of low oxygen tension (hypoxia and ischemia), but this metabolic pathway is incompletely understood in the context of histotoxic hypoxia (i.e., inhibition of oxygen utilization despite normal oxygen tension). In rabbits exposed to cyanide—a classical histotoxic hypoxia agent—we demonstrated significant increases in several concordant metabolites in the purine catabolic pathway (including plasma levels of uric acid, xanthosine, xanthine, hypoxanthine, and inosine) via mass spectrometry-based metabolite profiling. Pharmacological inhibition of the purine catabolic pathway with oxypurinol mitigated the deleterious effects of cyanide on skeletal muscle cytochrome c oxidase redox state, measured by non-invasive diffuse optical spectroscopy. Finally, plasma uric acid levels correlated strongly with those of lactic acid, an established clinical biomarker of cyanide exposure, in addition to a tissue biomarker of cyanide exposure (skeletal muscle cytochrome c oxidase redox state). Cumulatively, these findings not only shed light on the in vivo role(s) of cyanide but also have implications in the field of medical countermeasure (MCM) development.

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40

Ruan, Zhixiong, Debasish Ghorai, Giuseppe Zanoni y Lutz Ackermann. "Nickel-catalyzed C–H activation of purine bases with alkyl halides". Chemical Communications 53, n.º 65 (2017): 9113–16. http://dx.doi.org/10.1039/c7cc05011a.

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C–H alkylations of purine nucleosides were achieved by means of user-friendly nickel catalysis with ample substrate scope and high levels of chemo, site and regio control, which among others enabled the direct fluorescent labeling of purines in terms of late stage diversification.

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41

Durnin, Leonie, Andrea Lees, Sheerien Manzoor, Kent C. Sasse, Kenton M. Sanders y Violeta N. Mutafova-Yambolieva. "Loss of nitric oxide-mediated inhibition of purine neurotransmitter release in the colon in the absence of interstitial cells of Cajal". American Journal of Physiology-Gastrointestinal and Liver Physiology 313, n.º 5 (1 de noviembre de 2017): G419—G433. http://dx.doi.org/10.1152/ajpgi.00045.2017.

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Regulation of colonic motility depends on the integrity of enteric inhibitory neurotransmission mediated by nitric oxide (NO), purine neurotransmitters, and neuropeptides. Intramuscular interstitial cells of Cajal (ICC-IM) and platelet-derived growth factor receptor-α-positive (PDGFRα+) cells are involved in generating responses to NO and purine neurotransmitters, respectively. Previous studies have suggested a decreased nitrergic and increased purinergic neurotransmission in KitW/KitW-v ( W/Wv) mice that display lesions in ICC-IM along the gastrointestinal tract. However, contributions of NO to these phenotypes have not been evaluated. We used small-chamber superfusion assays and HPLC to measure the spontaneous and electrical field stimulation (EFS)-evoked release of nicotinamide adenine dinucleotide (NAD+)/ADP-ribose, uridine adenosine tetraphosphate (Up4A), adenosine 5′-triphosphate (ATP), and metabolites from the tunica muscularis of human, monkey, and murine colons and circular muscle of monkey colon, and we tested drugs that modulate NO levels or blocked NO receptors. NO inhibited EFS-evoked release of purines in the colon via presynaptic neuromodulation. Colons from W/Wv, Nos1−/−, and Prkg1−/− mice displayed augmented neural release of purines that was likely due to altered nitrergic neuromodulation. Colons from W/Wv mice demonstrated decreased nitrergic and increased purinergic relaxations in response to nerve stimulation. W/Wv mouse colons demonstrated reduced Nos1 expression and reduced NO release. Our results suggest that enhanced purinergic neurotransmission may compensate for the loss of nitrergic neurotransmission in muscles with partial loss of ICC. The interactions between nitrergic and purinergic neurotransmission in the colon provide novel insight into the role of neurotransmitters and effector cells in the neural regulation of gastrointestinal motility. NEW & NOTEWORTHY This is the first study investigating the role of nitric oxide (NO) and intramuscular interstitial cells of Cajal (ICC-IM) in modulating neural release of purines in colon. We found that NO inhibited release of purines in human, monkey, and murine colons and that colons from KitW/KitW-v ( W/Wv) mice, which present with partial loss of ICC-IM, demonstrated augmented neural release of purines. Interactions between nitrergic and purinergic neurotransmission may affect motility in disease conditions with ICC-IM deficiencies.

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42

Alexander, Steve P. H. y Anthony P. D. W. Ford. "Purines '96". Trends in Pharmacological Sciences 17, n.º 11 (noviembre de 1996): 385–88. http://dx.doi.org/10.1016/s0165-6147(96)30019-9.

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43

Headrick, John. "Purines 2002". Drug Development Research 56, n.º 4 (agosto de 2002): 545. http://dx.doi.org/10.1002/ddr.10123.

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44

Headrick, John. "Purines 2002". Drug Development Research 58, n.º 4 (abril de 2003): 291–92. http://dx.doi.org/10.1002/ddr.10211.

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45

Giráldez, F. J., R. Peláez, E. Zorita y C. Valdés. "Purine derivatives excretion in sheep urine in relation to metabolizable energy and rumen degradable protein intake". Proceedings of the British Society of Animal Production (1972) 1993 (marzo de 1993): 186. http://dx.doi.org/10.1017/s0308229600025083.

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Recently has been shown that allantoin or total purine derivatives excretion in urine are strongly related to the amount of purines reaching the small intestine (Chen et al., 1990; Balcells et al., 1992) and as consequence purine derivative output is propouse to be used as an index of microbial protein flow to small intestine.Because energy and rumen degradable protein supplies are the main factors affecting rumen microbial growth, the effect of changes in rumen degradable protein supplies at different levels of ME intake on urinary excretion of purine derivatives was studied in this work.

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46

Zilles, Julie L., T. Joseph Kappock, JoAnne Stubbe y Diana M. Downs. "Altered Pathway Routing in a Class ofSalmonella enterica Serovar Typhimurium Mutants Defective in Aminoimidazole Ribonucleotide Synthetase". Journal of Bacteriology 183, n.º 7 (1 de abril de 2001): 2234–40. http://dx.doi.org/10.1128/jb.183.7.2234-2240.2001.

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ABSTRACT In Salmonella enterica serovar Typhimurium, purine nucleotides and thiamine are synthesized by a branched pathway. The last known common intermediate, aminoimidazole ribonucleotide (AIR), is formed from formylglycinamidine ribonucleotide (FGAM) and ATP by AIR synthetase, encoded by the purI gene in S. enterica. Reduced flux through the first five steps of de novo purine synthesis results in a requirement for purines but not necessarily thiamine. To examine the relationship between the purine and thiamine biosynthetic pathways, purI mutants were made (J. L. Zilles and D. M. Downs, Genetics 143:37–44, 1996). Unexpectedly, some mutantpurI alleles (R35C/E57G and K31N/A50G/L218R) allowed growth on minimal medium but resulted in thiamine auxotrophy when exogenous purines were supplied. To explain the biochemical basis for this phenotype, the R35C/E57G mutant PurI protein was purified and characterized kinetically. The Km of the mutant enzyme for FGAM was unchanged relative to the wild-type enzyme, but theV max was decreased 2.5-fold. TheKm for ATP of the mutant enzyme was 13-fold increased. Genetic analysis determined that reduced flux through the purine pathway prevented PurI activity in the mutant strain, andpurR null mutations suppressed this defect. The data are consistent with the hypothesis that an increased FGAM concentration has the ability to compensate for the lower affinity of the mutant PurI protein for ATP.

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47

Delyani, J. A. y D. G. Van Wylen. "Endocardial and epicardial interstitial purines and lactate during graded ischemia". American Journal of Physiology-Heart and Circulatory Physiology 266, n.º 3 (1 de marzo de 1994): H1019—H1026. http://dx.doi.org/10.1152/ajpheart.1994.266.3.h1019.

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The purpose of this study was to compare interstitial fluid (ISF) levels of purine metabolites and lactate in the endocardium and the epicardium during graded regional myocardial ischemia and reperfusion. Anesthetized dogs were subjected to 60 min of regional myocardial ischemia induced by either partial or complete occlusion of the left anterior descending coronary artery (LAD), followed by 60 min of reperfusion. To sample ISF, cardiac microdialysis probes were implanted in the LAD-perfused myocardium; dialysate levels served as indexes of ISF concentrations. During severe ischemia, dialysate adenosine increased transiently in both the endocardium and epicardium, reaching maximal values at approximately 20 min of ischemia. Inosine, hypoxanthine, xanthine, and lactate increased most rapidly during the first 30 min of severe ischemia, after which the rate of increase was diminished. The ISF profiles of these metabolites were qualitatively similar during moderate ischemia, although the ISF levels achieved during ischemia were not as great. With both severe and moderate ischemia, ISF purines and lactate were greater in the endocardium than epicardium, consistent with a greater energy imbalance in the endocardium during ischemia. ISF total purines (the sum of the individual purine metabolites) were relatively stable until myocardial blood flow was reduced below 50 ml.min-1 x 100 g-1, after which ISF total purines increased in proportion to the severity of the blood flow deficit. These data suggest that functional and metabolic adaptations keep the myocardium in energy balance until blood flow is reduced below approximately 50% of control, and they attest to the usefulness of cardiac microdialysis for establishing transmural profiles of ISF metabolites.

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48

Weiner, Matthew A., Timothy D. Read y Philip C. Hanna. "Identification and Characterization of the gerH Operon of Bacillus anthracis Endospores: a Differential Role for Purine Nucleosides in Germination". Journal of Bacteriology 185, n.º 4 (15 de febrero de 2003): 1462–64. http://dx.doi.org/10.1128/jb.185.4.1462-1464.2003.

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ABSTRACT We identified a tri-cistronic operon, gerH, in Bacillus anthracis that is important for endospore germination triggered by two distinct germination response pathways termed inosine-His and purine-Ala. Together, the two pathways allow B. anthracis endospores a broader recognition of purines and amino acids that may be important for host-mediated germination.

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49

Linden, Joel, Friedrich Koch-Nolte y Gerhard Dahl. "Purine Release, Metabolism, and Signaling in the Inflammatory Response". Annual Review of Immunology 37, n.º 1 (26 de abril de 2019): 325–47. http://dx.doi.org/10.1146/annurev-immunol-051116-052406.

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ATP, NAD+, and nucleic acids are abundant purines that, in addition to having critical intracellular functions, have evolved extracellular roles as danger signals released in response to cell lysis, apoptosis, degranulation, or membrane pore formation. In general ATP and NAD+have excitatory and adenosine has anti-inflammatory effects on immune cells. This review focuses on recent advances in our understanding of purine release mechanisms, ectoenzymes that metabolize purines (CD38, CD39, CD73, ENPP1, and ENPP2/autotaxin), and signaling by key P2 purinergic receptors (P2X7, P2Y2, and P2Y12). In addition to metabolizing ATP or NAD+, some purinergic ectoenzymes metabolize other inflammatory modulators, notably lysophosphatidic acid and cyclic GMP-AMP (cGAMP). Also discussed are extracellular signaling effects of NAD+mediated by ADP-ribosylation, and epigenetic effects of intracellular adenosine mediated by modification of S-adenosylmethionine-dependent DNA methylation.

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50

Vakil Faraji, Yashar, Mojtaba Zahedifar y Jafari Khorshidi Kaveh. "Measurement of microbial protein synthesis in Iranian buffalo rumen (Mazandran Province) by purine derivatives excretion method". Proceedings of the British Society of Animal Science 2007 (abril de 2007): 216. http://dx.doi.org/10.1017/s1752756200021190.

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Rumen microbes are rich in nucleic acid: around 18% of total nitrogen is present on nucleic acids or 11% in purines. Rumen microbes constitue the major source of protein supply to the ruminant. The purines from the rumen microbes are metabolized and excreted in the urine as their end products: hypoxanthine, xanthine, uric acid and allantoin. In buffalo and cattle because of high xanthine oxidase activity in intestine and blood, hypoxanthine and xanthine convert to uric acid therefore only uric acid and allantoin excreted in urine way (Chen, X. B., Ørskov, E. R., 2003). This research carried out to use excretion of purine derivatives namely allantoin and uric acid as a parameter to estimate the microbial protein synthesis in the rumen of native swamp buffalo in north of iran, Mazandaran Province.

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