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PubMed1996

Slow bolus injection of ribose in the identification of thallium-201 redistribution following combined adenosine/dynamic exercise stress.

AIM: A simple stress/redistribution thallium-201 myocardial perfusion imaging protocol may underestimate the degree of thallium redistribution in a defect identified on the stress images. We sought to investigate whether a slow-bolus injection of D-ribose improves the identification of thallium redistribution following combined adenosine/dynamic exercise stress. MATERIALS AND METHODS: Fifteen patients (10 males, five female, median age 63 years, range 50-75) were enrolled in the study. All underwent two successive adenosine plus exercise myocardial perfusion scintigraphy protocols 7-14 days apart. Adenosine was infused at 140 micrograms.kg-1.min-1 coupled with 25 W ergometer pedalling for 6 min with 74 Mbq of thallium-201 being injected at 4 min. Immediately following the stress image acquisition, patients received the one of either 60 mg.kg-1 of D-ribose or normal saline, injected over 5 min. Redistribution images were acquired after 4 h. The identical stress procedure was conducted in the crossover arm of the study, and patients received the alternative test article. SPECT images were visually analysed and scored in a nine segment model by two blinded observers. In addition, circumferential profile analysis was conducted. RESULTS: By visual interpretation 25 segments displayed redistribution of the ribose, but not in the saline study, 14 reversible segments were seen on the saline study alone and 18 were seen on both studies (P = ns). In six patients ribose identified a greater number of redistributing segments and in a further six patients saline identified more reversible segments. Comparison of mean values of defect extent severity and percentage reversibility scores generated from the circumferential profile analysis showed no significant difference between the two arms of the study. CONCLUSION: A 5 min bolus injection of D-ribose following combined adenosine/dynamic exercise stress confers little benefit on the identification of redistribution of thallium-201. These results differ from those of previous studies which showed that a 30 min infusion of D-ribose following treadmill exercise significantly enhanced thallium redistribution. The duration of the ribose infusion is likely to be an important factor influencing the effect brought to bear on the redistribution of the tracer, and should be run over 30 min, or longer.

Adenosine↗
PubMed1980

Poly(ADP-ribose) and differentiation of Friend Erythroleukemia cells. Restriction of the chain lenght.

1. Poly(ADP-ribose) synthesized in nuclei isolated from Friend erythroleukemic cells was characterized. Although the activity of poly(ADP-ribose) synthesis of cells induced to differentiate was suppressed to about one-third of that of uninduced cells, the chain length were identical, and were clearly restricted within a narrow band in polyacrylamide gels, moving at about half the speed of bromphenol blue. 2. The restriction of chain length was also observed in rat liver nuclei, though some poly(ADP-ribose) chains could be degraded into smaller pieces during incubation. Treatment of nuclei with a high concentration of detergent and sonication before incubation caused aberrant synthesis of poly(ADP-ribose) chains which were not restricted in size. 3. In contrast, the average chain length of the 3H-labeled portion of poly(ADP-ribose) synthesized during incubation of nuclei with 3H-NAD+ was found to be reduced to 50% of that in the induced cells. 4. Under our reaction conditions, about 95% of newly synthesized poly(ADP-ribose) was linked to non-histone nuclear proteins. The total content of the non-histones was reduced to about 50% by treatment with inducers. 5. In view of the above findings, it is suggested that the decrease of chain initiation frequency caused by the partial loss of available acceptor sites may be correlated with the suppression of poly(ADP-ribose) synthesis in induced cells.

Acetamides↗
PubMed1975

The entry of D-ribose into some yeasts of the genus Pichia.

The utilization of D-ribose by yeasts of the genus Pichia was examined with respect to aerobic growth, respiration and entry of ribose into the cells. Pichia etchellsii (CBS2011) could respire D-ribose, but not use it for aerobic growth. Pichia fermentans (CBS187) neither respired nor grew on D-ribose, though it entered the cells of this yeast either by simple diffusion, or possibly, by the D-glucose carrier, this having a very low affinity for D-ribose. Pichia pinus (CBS5097) respired and grew on D-ribose; kinetic evidence is given for this yeast having two ribose carriers, one inducible and the other constitutive.

Aerobiosis↗
PubMed1993

Role of D-ribose as a cometabolite in D-xylose metabolism by Saccharomyces cerevisiae.

The influence of D-ribose as a cosubstrate on the uptake and metabolism of the non-growth substrate D-xylose by Saccharomyces cerevisiae ATCC 26602 was investigated. Xylose was taken up by means of low- and high-affinity glucose transport systems. In cells exposed for 2 days to a mixture of xylose and ribose, only the high-affinity system could be detected. Glucose strongly inhibited the transport of xylose by both systems. Starvation or exposure to either xylose or ribose resulted in inactivation of xylose transport, which did not occur in the presence of a mixture of ribose and xylose. A constitutive non-glucose-repressible NADPH2-dependent xylose reductase with a specific activity of ca. 5 mU/mg of protein that converted xylose to xylitol was present in a glucose-grown culture. No activity converting xylitol to xylulose or vice versa was found in crude extracts. Both xylose and ribose were converted to their corresponding polyols, xylitol and ribitol, as indicated by 13C nuclear magnetic resonance spectroscopy. Furthermore, ethanol was detected, and this implied that pathways for the complete catabolism of xylose and ribose exist. However, the NADPH2 required for the conversion of xylose to xylitol is apparently not supplied by the pentose phosphate pathway since the ethanol produced from D-[1-13C]xylose was labelled only in the C-2 position. Acetic acid was produced from ribose and may assist in the conversion of xylose to xylitol by cycling NADPH2.

Aldehyde Reductase↗
PubMed1974

Mechanism of energy coupling for transport of D-ribose in Escherichia coli.

In Escherichia coli ML 308-225, d-ribose is transported into the cell by a constitutive active transport system of high activity. The activity of this transport system is severely reduced in cells subjected to osmotic shock, and the system is not present in membrane vesicles. The mechanism by which metabolic energy is coupled to transport of ribose was investigated. Substrates which generate adenosine 5'-triphosphate primarily through oxidative phosphorylation are poor energy sources for ribose uptake in DL-54, a mutant of ML 308-225 which lacks activity for the membrane-bound Ca(2+), Mg(2+)-dependent adenosine triphosphatase required for oxidative phosphorylation. Arsenate severely inhibits ribose uptake, whereas, under the same conditions, uptake of l-proline is relatively insensitive to arsenate. Anaerobiosis does not significantly inhibit ribose uptake in ML 308-225 or DL-54 when glucose is the energy source. A significant amount of ribose uptake is resistant to uncouplers of oxidative phosphorylation such as 2,4-dinitrophenol. These results indicate that the phosphate bond energy of adenosine 5'-triphosphate, rather than an energized membrane state, couples energy to ribose transport in ML 308-225.

Adenosine Triphosphatases↗
PubMed2003

Preischemic administration of ribose to delay the onset of irreversible ischemic injury and improve function: studies in normal and hypertrophied hearts.

Compared with normal hearts, those with pathology (hypertrophy) are less tolerant of metabolic stresses such as ischemia. Pharmacologic intervention administered prior to such stress could provide significant protection. This study determined, firstly, whether the pentose sugar ribose, previously shown to improve postischemic recovery of energy stores and function, protects against ischemia when administered as a pretreatment. Secondly, the efficacy of this same pretreatment protocol was determined in hearts with pathology (hypertrophy). For study 1, Sprague-Dawley rats received equal volumes of either vehicle (bolus i.v. saline) or ribose (100 mg/kg) before global myocardial ischemia. In study 2, spontaneously hypertensive rats (SHR; blood pressure approximately 200/130) with myocardial hypertrophy underwent the same treatment protocol and assessments. In vivo left ventricular function was measured and myocardial metabolites and tolerance to ischemia were assessed. In normal hearts, ribose pretreatment significantly elevated the heart's energy stores (glycogen), and delayed the onset of irreversible ischemic injury by 25%. However, in vivo ventricular relaxation was reduced by 41% in the ribose group. In SHR, ribose pretreatment did not produce significant elevations in the heart's energy or improvements in tolerance to global ischemia, but significantly improved ventricular function (maximal rate of pressure rise (+dP/dt(max)), 25%; normalized contractility ((+dP/dt)/P), 13%) despite no change in hemodynamics. Thus, administration of ribose in advance of global myocardial ischemia does provide metabolic benefit in normal hearts. However, in hypertrophied hearts, ribose did not affect ischemic tolerance but improved ventricular function.

Adenosine Triphosphate↗
PubMed1983

Effects of ribose on cardiac metabolism and function in isoproterenol-treated rats.

Continuous iv infusion of ribose for 5 h in unanesthetized and unrestrained rats treated with isoproterenol (25 mg/kg sc) further enhanced the available pool of 5-phosphoribosyl-1-pyrophosphate and the biosynthesis of adenine nucleotides in the myocardium. The increase in adenine nucleotide biosynthesis was of such an extent that the isoproterenol-induced decline of the ATP level (mumol/g) was attenuated after 5 h (isoproterenol + ribose infusion 4.0 +/- 0.2, n = 10; isoproterenol + NaCl infusion 3.5 +/- 0.1, n = 23; control 4.5 + 0.1, n = 38) and prevented after 24 h (isoproterenol + ribose infusion 4.6 +/- 0.3, n = 5; isoproterenol + NaCl infusion 3.2 +/- 0.1, n = 9). Ribose, however, did not affect the isoproterenol-elicited elevation of the adenosine 3',5'-cyclic monophosphate (cAMP) and glucose 6-phosphate content nor did it influence the decline in glycogen. Thus ribose acts primarily via elevation of the cardiac 5-phosphoribosyl-1-pyrophosphate pool. Measurements of hemodynamic parameters with an ultraminiature catheter pressure transducer in intact rats anesthetized with thiobutabarbital sodium revealed that ribose infusion for at least 3 h further enhanced the isoproterenol-elicited increase in left ventricular dP/dtmax by about 20% but did not influence appreciably the rise in heart rate and the fall in left ventricular systolic pressure. Since ribose did not affect the immediate hemodynamic alterations induced by isoproterenol, it appears that it exerts its hemodynamic effects via the pronounced influence on cardiac adenine nucleotide metabolism.

Adenine Nucleotides↗
PubMed1983

Immunohistochemical demonstration of poly(adenosine diphosphate-ribose) synthetase in bovine tissues.

The inter- and intracellular localization of poly(adenosine diphosphate-ribose)(poly(ADP-ribose] synthetase was investigated using an indirect immunofluorescence technique and a specific antibody against the enzyme purified from calf thymus. In various bovine tissues, including liver, heart, pancrease, thyroid, spleen, adrenal, and skeletal muscle, the specific immunofluorescence of poly(ADP-ribose) synthetase was localized exclusively in the nucleus. Immunostaining was inhibited by preabsorption of the antibody with purified calf thymus poly(ADP-ribose) synthetase. Nuclear immunofluorescence appeared to be more prominent in the marginal area than in the central region in most nuclei. This staining pattern is similar to that of naturally occurring poly(ADP-ribose). In bovine peripheral blood the immunofluorescence of poly(ADP-ribose) synthetase was detected in nuclei of lymphocytes, but not in granulocytes, in agreement with the finding that the enzymatic activity of poly(ADP-ribose) synthetase was barely detectable in nuclei isolated from granulocytes.

Animals↗
PubMed2000

Noncovalent binding of poly(ADP-ribose) to nuclear matrix proteins: developmental changes and tissue specificity.

Poly(ADP-ribose) is a nuclear polynucleotide involved in the regulation of chromatin functions via covalent and/or noncovalent modification of nuclear proteins. Using a binding assay on protein blots, we searched for poly(ADP-ribose) binding proteins in nuclear matrices from testes of differently aged rats as well as from various adult rat tissues (brain, liver, spleen). We found that nuclear matrix proteins represent a significant subset of the nuclear proteins that can establish noncovalent interactions with poly(ADP-ribose). The profiles of poly(ADP-ribose) binding nuclear matrix proteins appeared to be tissue-specific and changed during postnatal development in the testis. The isolation and analysis of endogenous poly-(ADP-ribose) from rat testes showed that the ADP-ribose polymers that bind nuclear matrix proteins in vitro are also present under physiologic conditions in vivo. These results further substantiate the possibility that poly(ADP-ribose) may affect chromatin functions through noncovalent interaction with specific protein targets, including nuclear matrix components.

Animals↗
PubMed1976

Poly(adenosine diphosphate ribose) is covalently linked to nuclear proteins by two types of bonds.

(ADP-ribose)n residues formed by short-term incubation of adult rat liver and Ehrlich carcinoma nuclei with labeled NAD were analyzed by Cs2SO4/guanidinium chloride/urea density gradient centrifugation. Comparison with samples in which the protein had been completely digested revealed that most, or probably all, acid-insoluble (ADP-ribose)n chains are covalently bound to nuclear proteins, as is true for the short, acid-soluble (ADP-ribose)n chains. Complete release of (ADP-ribose)n chains is effected by dilute alkali. In contrast, NH2OH liberated only part of the long and the short (ADP-ribose)n residues from the protein conjugates, indicating two types of bonds, both alkali-labile, but only one susceptible to neutral hydroxylamine. Both types of bonds were equally distributed among acid-soluble and acid-insoluble (ADP-ribose)n chains. -Stability of the (ADP-ribose)n protein conjugates during isolation is only guaranteed at pH values below 7.

Animals↗
PubMedDate not supplied

Poly(ADP-ribose) synthesis in blocked and damaged cells and its relation to carcinogenesis.

There is compelling evidence showing that repair of DNA damage depends on the synthesis of poly(ADP-ribose) molecules at specific sites on histones and other proteins in nuclei of injured cells. In the present study, we have studied the effect of long-term exposure of mouse cells to nicotinamide and various cell cycle blockers on the ability of the cells to increase their levels of poly(ADP-ribose) in response to DNA methylation damage with dimethylsulfate (DMS). Of the cell cycle blockers used, hydroxyurea (HU) and cytosine arabinofuranoside (ara-C) inhibit DNA elongation at the replication fork and cause the appearance of small DNA molecules, whereas butyrate and colcemid block cells without interfering with DNA synthesis. In addition, cells were treated with nicotinamide, an inhibitor of poly(ADP-ribose) polymerase but also a precursor in NAD+ biosynthesis. Long-term exposure of cultured cells to these agents was followed with a short-term damage with DMS. The size-class distribution and concentration of poly(ADP-ribose) molecules were determined using high resolution polyacrylamide gel electrophoresis and were found to contain 1 to more than 30 ADP-ribosyl groups. On the contrary, histones from blocked cell nuclei were found to be mono- and oligo(ADP-ribosyl)ated. Thus, the large molecules of poly(ADP-ribose) were associated with nonhistone proteins and most likely with the enzyme pADP-R polymerase. DMS damage caused an increase in the levels of poly(ADP-ribose) that was synthesized in lysates from cells treated with any one drug alone. On the other hand, a dramatic decrease in total protein poly(ADP-ribosyl)ation resulted from DMS damage of cells treated with nicotinamide + HU or nicotinamide + ara-C. This decrease was not observed in combinations of nicotinamide with cell-cycle blockers that do not directly interfere with DNA synthesis (butyrate and colcemid). We suggest that nicotinamide + ara-C or nicotinamide + HU might be used as effective antineoplastic treatments by virtue of their ability simultaneously to damage DNA and reduce poly(ADP-ribosyl)ation and presumably DNA repair. A model for the facilitation of DNA repair by poly(ADP-ribosyl)ation of histones and of poly(ADP-ribose) polymerase is presented.

Animals↗
PubMed1979

Erythroid differentiation and poly(ADP-ribose) synthesis in Friend leukemia cells.

Nicotinamide, a specific inhibitor of poly(ADP-ribose) synthetase, was found to be a moderate inducer of hemoglobin synthesis in Friend erythroid leukemia cells (FLC). Therefore, the effect of other inducers, s-ch as dimethyl sulfoxide (DMSO), hexamethylene-bisacetamide (HMBA), and butyrate, on poly(ADP-ribose) synthesis was examined. The extent of poly(ADP-ribose) synthesis in nuclei of FLC treated with DMSO or HMBA began to decrease before many phenotypic changes including hemoglobin production and reached 30--50% of the level of nontreated control when the cells enter the stationary phase. FLC variants unresponsive to HMBA or DMSO did not exhibit as low an activity of poly(ADP-ribose) synthesis as their parent cells did by treatment with these inducers. In contrast, butyrate stimulated poly(ADP-ribose) synthesis transiently but distinctly (about 50%) at an early stage of culture (6--24 hr), but suppressed it at a later stage. Neither the cell growth nor degradation of poly(ADP-ribose) is correlated with the effect of inducers. These results suggest that the level of poly(ADP-ribose) synthesis is correlated with the differentiation of FLC.

Acetamides↗
PubMed2006

[Reversible inhibitory action of adenosine diphosphate ribose on isolated rat heart and rat heart in vivo].

Cardiotropic effects of endogenous regulator of intracellular ionic balance adenosine diphosphate ribose (ADP-ribose) was studied on isolated rat heart using standard retrograde perfusion and on rat heart in vivo by means of implanted arterial catheters. Parameters registered were heart rate, pressure developed in left ventricle of isolated heart and blood pressure of rats in vivo. It was shown that ADP-ribose exerted cardiotropic action on isolated rat heart and that its effects did not depend on effects of its metabolite AMP. In concentrations 10-70 microM ADP-ribose caused negative dose dependent chronotropic effect. Amplitude of contraction of isolated heart changed equivocally. In concentration 70 microM ADP-ribose in 50% of cases produced biphasic action: negative inotropic effect was preceded by positive inotropic effect. In other cases this concentration exerted negative inotropic effect. In concentration 10 microM only negative inotropic effect was observed. Contrary to ADP-ribose its metabolite AMP exerted only monophasic positive inotropic effect on isolated heart. The preparations studied differed in dynamics of cardiotropic action. In experiments in vivo ADP-ribose and AMP caused monophasic negative chronotropic and monophasic positive inotropic effects.

Adenosine Diphosphate Ribose↗
PubMed1991

Baseline sister chromatid exchange in human cell lines with different levels of poly(ADP-ribose) polymerase.

Poly(ADP-ribose) polymerase is a chromatin enzyme which adds long chains of ADP-ribose to various acceptor proteins in response to DNA strand breaks. Its primary function is unknown; however, a role in DNA repair and radiation resistance has been postulated based largely on experiments with enzyme inhibitors. Recent reports of mutant cell lines, deficient in poly(ADP-ribose) polymerase activity, have supported previous studies with inhibitors, which suggests the involvement of poly(ADP-ribose) polymerase in maintaining baseline levels of sister chromatid exchanges. Mutant cells with even slightly depressed enzyme levels show large elevation of baseline sister chromatid exchanges. Since intracellular poly(ADP-ribose) polymerase levels can vary greatly between different nonmutant cell lines, we surveyed levels of baseline sister chromatid exchange in normal and tumor human cell lines and compared them with endogenous levels of poly(ADP-ribose) polymerase. Despite 10-fold differences in poly(ADP-ribose) polymerase, the baseline level of sister chromatid exchanges remained relatively constant in the different cell lines (0.13 +/- 0.03 SCE/chromosome), with no indication of a protective effect for cells with high levels of the enzyme.

Humans↗
PubMed1988

Effect of ribose on thallium-201 myocardial redistribution.

Myocardial 201Tl redistribution after transient ischemia may be too slow to allow identification of a reversible myocardial defect within the routine 201Tl imaging period. To determine whether 201Tl redistribution could be affected by a metabolic intervention, intravenous ribose was administered postischemia. Seventeen domestic swine were subjected to a 10-min ischemic period followed by either a 30-min i.v. ribose (n = 8) or saline (n = 9) infusion. Thallium-201 was injected during ischemia and myocardial 201Tl activity was continuously monitored in ischemic and nonischemic regions with miniature CdTe radiation detection probes. Coronary flow in the ischemic region was reduced to 25% of that in the nonischemic regions in both saline and ribose groups. The 201Tl time-activity curves demonstrated a significant enhancement of % 201Tl redistribution in the ribose-treated animals at the end of ribose infusion: Ribose (48 +/- 11%), Saline (20 +/- 4%), p less than 0.05. Alteration of 201Tl kinetics by ribose may permit earlier recognition of 201Tl myocardial redistribution after transient ischemia.

Animals↗
PubMed1983

Poly(ADP-ribose) metabolism in ultraviolet irradiated human fibroblasts.

Exposure of human fibroblasts to 5 J/m2 of UV light resulted in a rapid increase of up to 1500% in the intracellular content of poly(ADP-ribose) and a rapid depletion of its metabolic precursor, NAD. When added just prior to UV treatment, the poly(ADP-ribose) polymerase inhibitor, 3-aminobenzamide, totally blocked both the increase of poly(ADP-ribose) and decrease in NAD for up to 2.5 h. Addition of 3-aminobenzamide at the time of maximal accumulation of poly(ADP-ribose) resulted in a decrease to basal levels with a half-life of approximately 6 min. The rates of accumulation of poly(ADP-ribose) and depletion of NAD were increased in the presence of either 1-beta-arabinofuranosylcytosine or hydroxyurea. Since these agents are known to cause an additional accumulation of DNA strand breaks following UV irradiation, these data provide evidence for a mechanism in which the rate of poly(ADP-ribose) synthesis following DNA damage is regulated in intact cells by the number of DNA strand breaks. Under conditions in which the synthesis of poly(ADP-ribose) was blocked, DNA repair replication induced by UV light was neither stimulated nor inhibited.

Cells, Cultured↗
PubMedDate not supplied

Biotransformation of the antiviral agent 1,3,4-thiadiazol-2-ylcyanamide (LY217896) and characteristics of a mesoionic ribose metabolite.

The biotransformation of the antiinfluenza agent 1,3,4-thiadiazol-2-ylcyanamide (LY217896, I) was studied. In addition to a urea metabolite (II) formed by transformation of the cyanamide functionality, another highly polar metabolite was found in mouse urine and in BSC-1, MDCK, and other cell culture incubations of [14C]LY217896. Using 13C-labeled LY217896 together with NMR and MS techniques, this highly polar metabolite was identified as a ribose derivative (III), which apparently exists in a mesoionic form (i.e. positive and negative charges within the same ring system). It was also found that this ribose is formed from LY217896 and ribose-1-phosphate in a reaction catalyzed by the enzyme purine nucleoside phosphorylase, but that the reverse reaction (cleavage of the ribose) is not observed under the conditions used. When tested in vitro using the same assay as that used to measure the antiviral activity of LY217896, this ribose and the urea metabolite exhibit essentially no activity. The presence of a ribose has been implicated in the activity of antiviral compounds such as ribavirin and anticancer agents like 2-aminothiadiazole and tiazofurin, which are structurally similar to LY217896. These activities have been postulated to involve either mono- or triphosphorylated forms, or NAD-type analogs. Possible implications of the formation of this mesoionic ribose metabolite for the mechanism of antiviral activity of LY217896 are discussed.

Animals↗
PubMed1997

Correlation between HLA-DR expression and level of poly(ADP-ribose) synthetase in human thyroid carcinoma cells.

The expression of MHC class II molecules is normally restricted to antigen presenting cells. Aberrant expression of class II molecules, however, was detected in the thyrocytes of autoimmune thyroid diseases. We attempted to regulate the expression of HLA-DR molecules in thyroid carcinoma cells by expressing the exogenous poly(ADP-ribose) synthetase gene. We transfected a metal inducible expression plasmid capable of expressing poly(ADP-ribose) synthetase gene into thyroid carcinoma 8505C cells and the transformants, treated with metal and IFN-gamma, were separated by Magnetic Cell Separation. The activity of the synthetase was increased in the HLA-DR-enriched transformants as compared with that in control or the HLA-DR+ transformants. RNA blot analysis and flow cytometric analysis revealed that the IFN-gamma-inducible expression of HLA-DR molecules was depressed by the induction of exogenous poly(ADP-ribose) synthetase gene. This result indicates that HLA-DR expression was correlated with the level of poly(ADP-ribose) synthetase in human thyroid carcinoma cells. Furthermore we examined the level of poly(ADP-ribose) synthetase in patients with autoimmune thyroid diseases. We observed a significant decrease in poly(ADP-ribose) synthetase in the patients. Taken together with the previous observation, the decrease in poly(ADP-ribose) synthetase is closely linked to the aberrant expression of HLA-DR molecules in some autoimmune thyroid diseases.

Autoimmune Diseases↗