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PubMed1993

Mechanism of enhancement of neutrophil survival by granulocyte colony-stimulating factor and adenine.

An in vitro study was performed on the effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) and adenine on the survival of purified human neutrophils. The addition of rhG-CSF (1 to 100 ng/mL) or adenine (100 microM) enhanced the survival of neutrophils. The maintenance of O2- production in response to N-formylmethionyl-leucyl-phenyl-alanine (FMLP) suggested that these neutrophils were functionally alive. Neutrophils in cultures had shown two distinct biochemical changes during cell death: DNA fragmentation and depletion of cellular adenosine triphosphate (ATP) pools. Treatment with rhG-CSF (10 ng/mL) significantly delayed the appearance of DNA fragmentation as measured quantitatively by diphenylamine or by agarose gel electrophoresis. On the other hand, adenine had no effect on the generation of DNA fragmentation. The decrease of ATP during incubation for 12 hours was similar in control and rhG-CSF-treated neutrophils, while rhG-CSF prevented the further decline of ATP seen in control cultures. In contrast, adenine (100 microM) preserved ATP at levels significantly higher than in controls at both 12 hours and 24 hours of incubation. Our results suggest that rhG-CSF and adenine promote the survival of neutrophils in vitro by different mechanisms.

Adenine↗
PubMed1994

Adenine nucleotides regulate ADP-ribosylation of membrane-bound actin and actin-binding to membranes.

Adenine nucleotides were shown to increase the ADP-ribosylation of actin by Clostridium perfringens iota and Clostridium botulinum C2 toxin in membranes from human platelets, hamster fat cells, rat liver- and rat brain cells. ATP and ATP gamma S were the most effective agents with ATP showing half-maximal and maximal effects at about 2 and 10 microM, respectively. The rank order of various adenine nucleotides were ATP = ATP gamma S > ADP > AMP-PNP >> AMP = cAMP. Guanine nucleotides showed the same rank order of potencies but were less effective than adenine nucleotides. Adenine nucleotides which increased ADP-ribosylation were able to release actin from membranes. [32P]ADP-ribosylated rabbit skeletal muscle actin, which is unable to polymerize, was used as tool to study membrane-binding of actin. The [32P]ADP-ribosylated actin bound to stripped rat liver membranes in a saturable, time- and temperature-dependent manner. ATP inhibited the binding of ADP-ribosylated actin with a half-maximal and maximal inhibitory concentration at about 50 and 300 microM, respectively. The data indicate that actin-binding to membranes is prevented or reversed in the presence of adenine nucleotides thereby increasing the accessibility of actin for ADP-ribosylation by toxins.

ADP Ribose Transferases↗
PubMed1993

Development of storage granules during megakaryocyte maturation: accumulation of adenine nucleotides and the capacity for serotonin sequestration.

The specific release of platelet-dense body constituents such as adenine nucleotides and serotonin has a fundamental role in hemostasis. The content of adenine nucleotides in platelet dense bodies is probably established in megakaryocytes, but very little is known about this process. To gain a better understanding of platelet development, we studied the storage and metabolic pools of adenine nucleotides and the capacity for serotonin sequestration in storage granules during megakaryocyte maturation. Megakaryocytes were isolated from guinea pig bone marrow and separated in subgroups at different phases of maturation. The sequestration of adenine nucleotides and serotonin in storage granules was assessed by using calcium ionophore to induce secretion under nonlytic conditions, and metabolic pool adenine nucleotides were evaluated by using digitonin under controlled lysis conditions. The study showed that there were similar amounts of cytoplasmic adenosine triphosphate (ATP) in the mature and immature fractions based on digitonin-induced controlled lysis (1.26 +/- 0.37 nmol/microgram phosphorus vs 1.23 +/- 0.44 nmol/microgram phosphorus). However, only the mature cells contained a significant amount of storage pool ATP (0.41 +/- 0.19 nmol/microgram phosphorus vs 0.05 +/- 0.05 nmol/microgram phosphorus) released in response to A23187. The subgroups of megakaryocytes contained equal amounts of total adenosine diphosphate (ADP) extractable with ethanol (0.49 +/- 0.14 nmol/microgram phosphorus vs 0.55 +/- 0.50 nmol/microgram phosphorus) but only mature cells contained ADP in the storage granules (0.25 +/- 0.13 nmol/microgram phosphorus vs 0.07 +/- 0.05 nmol/microgram phosphorus).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1995

Fluorescence spectroscopic study of the interaction of adenine and nucleotide with trichosanthin.

Trichosanthin (TCS) is an N-glycosidase that can attack the 28s rRNA of the ribosome at a highly conserved adenine residue. The interactions of adenine and its derivative nucleotides with TCS are reported. The fluorescence of Trp 192 of TCS is sensitive to the proximity of adenine, and produces a marked red shift indicative of trytophan in a more hydrophilic environment. By contrast AMP and ATP quench the maximal emission at 328nm. The binding of the adenine and ATP with TCS result in lower tryptophan accessibility to the quencher acrylamide, but higher tryptophan accessibility to the quencher iodide, while AMP caused higher tryptophan accessibility to acrylamide, and lower tryptophan accessibility to iodide. Also, the binding of nucleotides induces tryptophan heterogeneity in the protein. These findings lead us to propose that binding of nucleotides and adenine base cause different microenvironmental changes of the tryptophan residue, and Trp 192 may be involved in the active site of TCS.

Adenine↗
PubMed1996

Three recognition events at the branch-site adenine.

An adenosine at the branch site, the nucleophile for the first transesterification step of splicing, is nearly invariant in mammalian pre-mRNA introns. The chemical groups on the adenine base were varied systematically and assayed for formation of early spliceosome complexes and execution of the first and second steps of splicing. Recognition of constituents of the adenine is critical in formation of a U2 snRNP-containing complex on a minimal branch-site oligonucleotide. Furthermore, the efficiencies of the first and second chemical steps have different dependencies on the functional groups of the adenine. In total, the chemical groups on the adenine base at the branch site are differentially recognized during at least three different processes in the splicing of pre-mRNA. Moreover, a protein, p14, interacts with the adenine in a base-specific fashion and may mediate early recognition of this base.

Adenine↗
PubMedDate not supplied

[Concentration of free nucleotides and turnover of adenine nucleotides in the liver of birds of different ages].

The content of free nucleotides and exchangeability of adenine nucleotides were studied in the liver of 1- and 18-month cocks. It is established that adenine nucleotides in the young cocks liver account for 40%, uridine nucleotides for 29%, cytidine nucleotides for 13% of the total amount of nucleotides. These ratios are maintained with age but the amount of adenine nucleotides decreases by 35% and that of uridine nucleotides by 22%. Against a background of a relatively constant level of adenine and uridine nucleotides the content of cytidine and guanine nucleotides varies synchronously within wide ranges, which can evidence for the presence of a common mechanism of regulating synthesis of these metabolites. A direct correlation is detected between the amount of adenine nucleotides and their specific radioactivity. This is due to a higher intensity of synthetic processes in young cocks. The inverse correlation is observed in adult cocks, that results from the effect of "label dilution".

Adenine Nucleotides↗
PubMed1997

Protective effect of adenine on DNA synthesis in irradiated Ehrlich ascites tumor cells.

Ehrlich ascites tumor cells were cultured in the presence of adenine for several hours before gamma irradiation. The inhibition of DNA synthesis that is normally observed when these cells are irradiated was prevented. More detailed analysis using the velocity sedimentation technique provided evidence that this protective effect occurred at the level of initiation of DNA replication. This conclusion is supported by the fact that adenine failed to prevent the inhibition of DNA synthesis induced by hydroxyurea. The ability of adenine to suppress the gamma-ray-induced inhibition of DNA synthesis was dependent on both its concentration and the exposure time. This suppression was already pronounced by about 4 h after exposure of the cells to adenine, and the maximum effect was observed within 6-20 h. The optimum concentration of adenine was about 0.1 mM. Among other purines tested, a similar effect was caused only by guanine.

Adenine↗
PubMed1997

Adenine nucleotides undergo rapid, quantitative conversion to adenosine in the extracellular space in rat hippocampus.

There are multiple mechanisms by which adenine nucleotides can be released into the extracellular space in brain. Adenine nucleotides are converted extracellularly to adenosine, which then acts on adenosine receptors to elicit physiological responses, but the rate at which this conversion takes place is unknown. In the present experiments, adenine nucleotides were applied to individual hippocampal neurons, and the subsequent activation of a postsynaptic K+ conductance by adenosine A1 receptors was used to determine the rate of adenosine formation. None of the adenine nucleotides tested (cAMP, AMP, ADP, and ATP) activated A1 receptors directly at the concentrations tested (</=200 microM). AMP, ADP, and ATP were all rapidly converted to adenosine, with a T1/2 for ATP conversion to adenosine of approximately 200 msec, and the last step in this pathway (transformation of AMP to adenosine by 5'-nucleotidase) seems to be the rate-limiting step. As we have reported previously, cAMP is converted to adenosine as well, but on a much slower time scale than any of the other nucleotides tested. These experiments demonstrate that fast, localized release of AMP, ADP, or ATP can result in a transient activation of adenosine receptors but that this is unlikely to occur with cAMP. The existence of a highly active ecto-nucleotidase pathway in brain provides a mechanism for the rapid generation of adenosine after the release of adenine nucleotides into the extracellular space.

Adenine Nucleotides↗
PubMed1997

Raman scattering tensors of adenine.

Polarized Raman scattering measurements have been made of a single crystal of adenine dihydrochloride (adenine-2H+) by the use of Raman microscope with 488.0 nm excitation. The adenine-2H+ crystal belongs to the space group Pnma (orthorhombic), and Raman intensities of Iaa, Ibb, Icc and Iac (which correspond to the aa, bb, cc and ac components of the crystal Raman tensor) have been determined for each Raman band. The depolarization ratios of Raman bands have been observed for fully random molecular orientations in an adenine 6N HCl aqueous solution. From these experimental data, and by taking the known crystal structure into account, anisotropic and isotropic molecular Raman scattering tensors have been determined for each vibrational mode of the adenine residue.

Adenine↗
PubMed1988

Adenosine induction of rapid catabolism of adenine ribonucleotides and independent elevation of the ATP content in quiescent mouse fibroblasts.

The influence of adenosine on the ribonucleotide metabolism in quiescent BALB/c 3T3 cells was studied. The cellular adenine ribonucleotides were labelled by pretreating the cells with [2-3H]-adenine. After addition of adenosine to the cell cultures, the amount and radioactivity of the cellular purine ribonucleotides and the radioactivity of the purine compounds in the medium were determined. It appeared that adenosine gave rise both to rapid catabolism of adenine ribonucleotides with inosine 5'-monophosphate (IMP) as an intermediate and to expansion of the cellular adenosine 5'-triphosphate (ATP) pool. The maximal rates and the apparent activation constants for the two processes have been determined. Experiments with varying concentrations of coformycin (an inhibitor of adenosine 5'-monophosphate [AMP] deaminase and adenosine deaminase) and of 5'-amino-5'-deoxyadenosine (an inhibitor of adenosine kinase), respectively, showed that each compound may almost completely inhibit the adenosine-induced catabolism. This effect can be obtained under conditions where there was little or no effect by the two inhibitors on the rate of expansion of the cellular ATP pool. These results may best be explained by assuming that the process of expansion of the ATP pool is independent of the induced catabolism of adenine ribonucleotides, even though both processes seem to depend on the phosphorylation of adenosine to AMP. The total increase in the pool size of ATP and of guanosine 5'-triphosphate (GTP), both caused by adenosine, seems not to have regulatory effect on adenine ribonucleotide catabolism.

Adenosine↗
PubMed2001

Electronic Properties of Q-CdS Clusters Stabilized by Adenine.

Adenine-capped Q-CdS has been synthesized in an aqueous medium. IR spectroscopy indicates an interaction between Q-CdS and adenine through Cd(2+). The amount of adenine controls the size of the clusters. A typical 5x10(-3) mol dm(-3) of adenine produces nanoclusters having the onset of absorption and an emission band at 2.8 and 2.35 eV, respectively. Adenine binds to the shallower traps and enhances the emission intensity of the 530-nm band without causing any shift in emission. Thermolysis of these colloids leads to the production of larger CdS clusters with changed electronic properties. Relaxation kinetics of charge carriers shows their average lifetime to increase with a decrease in particle size. Illumination of these particles does not lead to their photodissolution. This catalyst is, however, photoactive. The addition of indole causes the quenching of its emission. The photocatalytic oxidation of indole produces indigo with a quantum efficiency of 0.03. Copyright 2001 Academic Press.

Journal Article↗
PubMed1987

A review of the efficacy of adenine arabinoside and lymphoblastoid interferon in the Royal Free Hospital studies of hepatitis B virus carrier treatment: identification of factors influencing response rates.

We have reviewed the results of treating over 100 HBV carriers with adenine arabinoside, adenine arabinoside monophosphate and lymphoblastoid interferon. In the homosexual group of carriers, adenine arabinoside and its monophosphate have no value. However in this group, lymphoblastoid interferon will produce a response in over 50% of cases. This lack of effectiveness of adenine arabinoside monophosphate in this group may stem from its immunosuppressant properties. In heterosexual carriers both adenine arabinoside monophosphate and lymphoblastoid interferons are effective in approximately 50% to 60% of cases. However, the response rate is different in the various racial groups. Northern European and Mediterranean people appear to respond whereas those from the Far East do not. This may reflect the fact that there are at least two mechanisms by which the chronic carrier state may arise. In 5% to 10% of adults, a relative deficiency of alpha interferon production exists, and this defect is found in the majority of HBV carriers in Western Europe. In these, interferon acts as a replacement therapy and excellent results may be obtained if the patient is treated early in the course of the disease. It would appear that as the duration of the infection increases, the virus may integrate into interferon-reactive consensus sites and prevent the cell from responding to interferon. In patients infected at birth, transplacental anti-HBc appears to modulate the immune response and, along with immaturity of the immune system at this age, results in failure to lyse infected cells. These patients do not benefit from interferon treatment: some form of immune manipulation is required.(ABSTRACT TRUNCATED AT 250 WORDS)

Arabinonucleotides↗
PubMed1976

Role of the intramitochondrial adenine nucleotides as intermediates in the uncoupler-induced hydrolysis of extramitochondrial ATP.

1. A formula is given that describes the appearance of [14C]ATPADP outside the mitochondria after the addition of [14C] 1atp during the steady-state uncoupler-induced hydrolysis of extramitochondrial ATP. If the transported adenine nucleotides equilibrate with the intramitochondrial pool, [14C]ADP0 would be expected to appear with a lag phase that corresponds with the time needed for the radioactive labelling of the intramitochondrial adenine nucleotide pool. 2. The rates of formation of [14C]ADP outside the mitochondria after addition of [14C]ATP during the steady-state uncoupler-induced ATP hydrolysis catalysed by rat-liver mitochondria at 0 degree C were measured. 3. In the presence of carbonyl cyanide m-chlorophenylhydrazone the time course of the [14]ADPo formation was the same as that predicted on the basis of the above assumption. 4. In the presence of the less effective uncoupler, 2,4-dinitrophenol, the time course of [14C]ADPo formation was not consistent with the theoretical predictions: no lag phase was present and the measured rate was higher than the maximal calculated rate. These results can be explained by assuming a functional interaction between the adenine nucleotide translocator and the mitochondrial ATPase (F1). 5. It is concluded that under phosphorylating as well as dephosphorylating conditions, the adenine nucleotide translocator and the mitochondrial ATPase can be functionally linked to catalyse phosphorylation or dephosphorylation of extramitochondrial ADP or ATP, without participation of the intramitochondrial adenine nucleotides.

Adenosine Diphosphate↗
PubMed1983

Modification of liver mitochondrial lipids and of adenine nucleotide translocase and oxidative phosphorylation by cold adaptation.

The decrease in respiration rate following thyroidectomy is preceded by changes in the lipid composition of the mitochondrial membrane (Hoch, F.L., Subramanian, C., Dhopeshwarkar, G.A. and Mead, J.F. (1981) Lipids 16, 328-334) and in concert, changes in the kinetic parameters of the adenine nucleotide translocase (Mak, I.T., Shrago, E. and Elson, C.E. (1981) Fed. Proc. 40, 398). To demonstrate that physiological adaptation also involves this sequence of events, rats were housed at 8 degrees C for 3-4 weeks. Cold adaptation resulted in a modest (5%) increase in the unsaturation index for the mitochondrial fatty acids comprised of a significant increase in arachidonic acid and a reciprocal decrease in linoleic acid. Phospholipid analysis indicated that cold adaptation increased the mitochondrial phosphatidylethanolamine and reciprocally decreased the phosphatidylcholine content. Concomitantly, cold adaptation resulted in 25-30% increases in rat liver mitochondrial respiratory activities without changing the respiratory control or ADP/O ratios. The kinetic parameters of the adenine nucleotide translocase were determined by the back-exchange method (Pfaff, E. and Klingenberg, M. (1968) Eur. J. Biochem. 6, 66-79). At 0-4 and 10 degrees C, the Vmax and Km of the cold-adapted rat liver adenine nucleotide translocase were not distinguishable from the control values. The Ki values determined by Dixon plot studies for atractylate and palmitoyl-CoA were also comparable between the two groups. However, at 25 and 37 degrees C, cold-adapted rat liver adenine nucleotide translocase exhibited a 20% increase in Vmax and a 20% decrease in Km for external ADP. The results suggest that one adaption to a cold environment involves hormone-mediated changes in the lipid composition in the mitochondrial membranes which in turn modulate the adenine nucleotide translocase and subsequent respiratory activities.

Acclimatization↗
PubMed1984

Inhibition of the adenine nucleotide translocator by matrix-localized palmityl-CoA in rat heart mitochondria.

The activity of the adenine nucleotide translocator in rat heart mitochondria was quantitatively determined by the rate of [14C]ATP transport at 2 degrees C using the carboxyatractyloside inhibitor-stop technique. Linear uptake was obtained for 15 s, and with differing protein concentrations. The effect of matrix long-chain acyl-CoA esters upon the adenine nucleotide translocator activity was determined in these mitochondria. Incubation with palmitylcarnitine produced an increase in matrix long-chain acyl-CoA esters and decreased the velocity of [14C]ATP transport. Mitochondria isolated in the presence of KCN showed elevated levels of long-chain acyl-CoA esters, decreased transportable nucleotides, and very low adenine nucleotide translocator activity. Addition of potassium ferricyanide to these mitochondria caused a reduction in matrix acyl-CoA esters and partially restored adenine nucleotide translocator activity. Potassium ferricyanide also lowered matrix acyl-CoA in freshly isolated mitochondria and increased [14C]ATP transport. These findings show that the level of long-chain acyl-CoA esters within the mitochondrial matrix affects adenine nucleotide translocator activity and regulates mitochondrial activity.

Acyl Coenzyme A↗
PubMed1995

Irreversible inhibition of human natural killer cell natural cytotoxicity by modification of the extracellular membrane by the adenine nucleotide analog 5'-p-(fluorosulfonyl)benzoyl adenosine.

Extracellular adenine nucleotides are inhibitors of the human natural killer cell line NK3.3 natural cytotoxicity activity. Natural cytotoxicity was inhibited approximately 26% by 1 mM ATP and 21% by 1 mM ADP. 5'-Adenylyl imidodiphosphate, a nonhydrolyzable ATP analog, inhibited natural cytotoxicity by 41% at a concentration of 1 mM and > 97% at a concentration of 10 mM. In contrast, AMP was not inhibitory. Adenosine was a weak inhibitor of natural cytotoxicity and may represent an alternate regulatory pathway. Removal of the nucleotides resulted in the restoration of control levels of natural cytotoxicity activity. The affinity label 5'-p-(fluorosulfonyl)benzoyladenosine (5'-FSBA) is a synthetic analog of ATP or ADP containing an electrophilic fluorosulfonyl group capable of covalently modifying proteins at adenine di- and triphosphate nucleotide-binding sites. Natural cytotoxicity was irreversibly inhibited by modification of the extracellular membrane of NK3.3 cells by 5'-FSBA. This inhibition was concentration dependent with an I50 approximately 100 microM and complete inhibition at 1 mM. Modification of NK3.3 by 5'-FSBA did not affect the formation of effector-target cell conjugates; however, granule release was inhibited. This targets the site of inhibition by 5'-FSBA modification to a pathway preceding granule release. Irreversible, covalent modification of surface adenine nucleotide-binding proteins by 5'-FSBA provides a probe to study the role of specific adenine nucleotide-binding proteins in the extracellular regulation of natural killer cytolytic activity by adenine nucleotides.

Adenosine↗
PubMed1988

Morphology and distribution of nicotinamide adenine dinucleotide phosphate (reduced form) diaphorase reactive neurons in human brainstem.

Nicotinamide adenine dinucleotide phosphate diaphorase reactive neurons were found in several regions of human brainstem. Three major groups were located in the medulla: a dorsomedial group in the central gray and floor of the fourth ventricle, a ventromedial group in the vicinity of the medullary raphe, and a lateral group in the lateral reticular nucleus. In the upper pons a large cluster of reactive neurons was centered in the nucleus centralis oralis extending into the locus coeruleus and dorsal tegmental region. A second cluster in the lateral parabrachial nucleus merged with this group more rostrally and continued into the midbrain tegmentum (paracoeruleus-cuneiform group). Nicotinamide adenine dinucleotide phosphate diaphorase neurons in this region often contained acetylcholinesterase activity. A second midbrain group was seen in the nucleus paranigralis. Aside from these discrete neuronal collections, scattered reactive neurons were found in the medullary reticular formation, periaqueductal gray, inferior colliculus and superior colliculus. Nicotinamide adenine dinucleotide phosphate diaphorase neurons were classified into three groups based on somal size. Parvocellular neurons (10-20 micron) were primarily found in the ventromedial medulla and lateral parabrachial nucleus. Intermediate neurons (20-25 micron) were located in the paranigralis nucleus and dorsomedial medulla. Magnocellular neurons (25-35 micron) were characteristically found in the lateral reticular nucleus and paracoeruleus-cuneiform region. Nicotinamide adenine dinucleotide phosphate diaphorase reactive neurons are present in substantial numbers in human brainstem and their distribution is complex. They represent the caudal end of a widespread network of nicotinamide adenine dinucleotide phosphate diaphorase-enriched neurons that extend rostrally from the brainstem reticular formation into the basal forebrain, striatum, and cerebral cortex.

Adult↗
PubMed2005

Insight into the functional consequences of hMYH variants associated with colorectal cancer: distinct differences in the adenine glycosylase activity and the response to AP endonucleases of Y150C and G365D murine MYH.

Escherichia coli MutY and its eukaryotic homologues play an important role in preventing mutations by removing adenine from 7,8-dihydro-8-oxo-2'-deoxyguanosine (OG):A mismatches. It has recently been demonstrated that inherited biallelic mutations in the genes encoding the human homologue of MutY (hMYH) are correlated with a genetic predisposition for multiple colorectal adenomas and carcinomas. The two most common hMYH variants found in patients with colorectal cancer are Y165C and G382D. In this study, we examined the equivalent variants in the murine MutY homologue (mMYH), Y150C and G365D. The Y150C mMYH enzyme showed a large decrease in the rate of adenine removal from both OG:A- and G:A-containing substrates, while G365D mMYH showed a decrease in the ability to catalyze adenine removal only with a G:A-containing substrate. Both mMYH variants exhibit a significantly decreased affinity for duplexes containing noncleavable 2'-deoxyadenosine analogues. In addition, the human apurinic/apyrimidinic endonuclease (Ape1) stimulated product formation by wild-type and G365D mMYH with an OG:A substrate under conditions of multiple-turnover ([E]<[S]). In contrast, the presence of Ape1 nearly completely inhibited adenine removal by Y150C mMYH from the OG:A mismatch substrate. The more deleterious effect of Ape1 on the glycosylase activity of Y150C relative to G365D mMYH correlated with the more compromised binding affinity of Y150C to substrate analogue duplexes. These results suggest that the equivalent hMYH variants may be significantly compromised in substrate targeting in vivo due to a decrease in binding to substrate DNA; moreover, competition with other DNA binding proteins may further reduce the effective adenine glycosylase activity in vivo.

Animals↗