Alteration of purine metabolism by AICA-riboside in human B lymphoblasts.

The effect of 5-amino-4-imidazole-carboximide (AI-CA)-riboside on different pathways of purine metabolism (biosynthesis de novo, salvage pathways, adenosine metabolism, ATP catabolism) was studied in human B lymphoblasts (WI-L2). AICA-Riboside markedly decreased intracellular levels of 5-phosphoribosyl-1-pyrophosphate and in consequence affected purine biosynthesis de novo and purine salvage pathways. AICA-riboside inhibited incorporation of glycine into purine nucleotides, but when formate was used as the precursor of purine biosynthesis de novo, a biphasic effect was observed. The incorporation of formate into purine nucleotides was increased by AICA-riboside at concentrations up to 2 mM but decreased at higher concentrations. Salvage of the purine bases adenine, hypoxanthine, and guanine was markedly inhibited and utilization of extracellular adenosine in B lymphoblasts was reduced by AICA-riboside. AICA-riboside increased ribose 1-phosphate concentrations and increased degradation of prelabeled ATP. No effect on the intracellular levels of orthophosphate was found. Proliferation of WI-L2 lymphoblasts was only slightly affected at concentrations of AICA-riboside below 500 microM but markedly inhibited by higher concentrations.     

Relationship between 5-aminoimidazole-4-carboxamide-ribotide and AMP-activated protein kinase activity in the perfused mouse heart

AMP-activated protein kinase (AMPK) is a cellular energy sensor whose activity responds to AMP concentration ([AMP]). An agent that activates AMPK in cells is 5-aminoimidazole-4-carboxamide-1-riboside (AICA-riboside). Phosphorylated AICA-riboside or AICA-ribotide (ZMP) is an AMP analog. It is generally assumed that ZMP accumulation does not alter [AMP]. Additionally, the effect of AICA-riboside on AMPK activity of the heart is uncertain. Two hypotheses were tested in the isolated mouse heart: 1) sufficient ZMP concentration ([ZMP]) forms to increase AMPK activity, and 2) [ZMP] accumulation increases [AMP]. Perfusion of isolated mouse hearts with Krebs-Henseleit buffer containing 0.15-2 mM AICA-riboside concentration resulted in [ZMP] of 2-8 mM. ZMP accumulation reduced phosphocreatine concentration, which increased cytosolic [AMP]. In hearts with [ZMP] less than approximately 3 mM, in vivo AMPK allosteric activity effects of ZMP were observed; AMPK phosphorylation and [AMP] were not increased. With [ZMP] between 3 and 5 mM, in vitro AMPK activity and phosphorylation increased with unchanged [AMP]. This occurred in hearts perfused with 0.25 mM AICA-riboside for 48 min and 0.5 mM AICA-riboside for 24 min. The [ZMP] resulting in 50% AMPK activity (covalent phosphorylation of AMPK) was 4.1 +/- 0.6 mM. Hearts with [ZMP] >5 mM displayed increased [AMP] and AMPK activity that was not different from hearts with similar [AMP] with no [ZMP]; the half-maximal activity of AMP was 5.6 +/- 1.6 microM. Thus, in mouse hearts, AICA-riboside was metabolized to [ZMP] adequately to increase AMPK activity. Higher [ZMP] also increased cytosolic [AMP], which affects AMPK activity.     

Studies on the Accumulation of 5(4)-Amino-4(5)-imidazole- carboxamide by Escherichia coli in a Shaking Culture

Various attempts were made to accumulate 5 (4) -amino-4 (5) -imidazolecarboxamide (abreviated as AICA; in this paper, separate analyses for the riboside forms were not attempted, and hence AICA and AICA-riboside will be presented as total AICA) in a shaking culture medium by Escherichia coli strain B. The accumulation of non-acetylatable, diazotizable amines was accomplished by the addition of 0.01% of sulfadiazine, 0.2% of glucose, and 2% of peptone in the medium for sixteen hours at 30°C. E coli strain B was able to accumulate the amines in the pepton medium, even when glucose and the sulfonamide inhibtor were omitted. Although paper chromatographic and spectrophotometric analyses proved the accumulation of AICA and AICA-riboside by E. coli train B in the medium, another substance colored by the Bratton and Marshall method was also accumulated.     

Consequences of activation and adenosine-mediated inhibition of granulocytes during myocardial ischemia

During acute myocardial ischemia, granulocytes accumulate and obstruct the microcirculation. Granulocytes remain plugged in individual myocardial capillaries on reperfusion and are the major cause of the no-reflow phenomenon. During 3 h of ischemia, the granulocyte content of myocardium measured by 111In labeling increases from 1.0 X 10(6) to 1.5 X 10(6) cells/g, and after 5 min of reperfusion increases to 2.4 X 10(6) cells/g. The effects of granulocytes during 1 h of acute ischemia were determined by comparing agranulocytic to whole blood perfusion. With whole blood collateral flow decreased, water content increased (edema), ventricular fibrillation was common, and 27% of capillaries had no-reflow, whereas in the absence of granulocytes, collateral flow increased, there was no edema, arrhythmias were rare, and the no-reflow phenomenon was completely prevented. It is unfortunate that the inflammatory signals triggered by ischemia remain active on acute reperfusion, limit tissue salvage, and perhaps cause reperfusion injury. Several activating stimuli for granulocytes are known, but what inhibits them? Adenosine is known to inhibit superoxide radical formation by granulocytes, and 5-amino-4-imidazole carboxamide-riboside (AICA-riboside) augments adenosine release from energy-deprived cells. In dogs subjected to 1 h of ischemia, AICA-riboside pretreatment augmented adenosine release by nearly 10-fold, which was accompanied by a significant increase in collateral blood flow and decreased arrhythmias. We propose a new hypothesis: adenosine acts as a natural antiinflammatory autacoid during transient injury linking the ability to catabolize ATP (an indicator of viability) to granulocyte inhibition, thus preventing premature activation of the inflammatory response to cell death. Granulocytes are active participants in acute myocardial ischemia and means to prevent their activation, remove them from the reperfusate, or inhibit them will be necessary for optimum reperfusion salvage.     

Aerobic biodegradation of alkylphenol ethoxylates

Primary aerobic biodegradation of alkylphenol ethoxylates (APEOs) was studied using a new simple and fast porphyrin method, which did not require the extraction step. Extent of primary biodegradation of a nonylphenol ethoxylates (NP-10) was excess of 92% after 1.5 days, and reached 99% after 2 days, which was similar to the results obtained using modified CTAS (thiocyanate active substances) method. Degradation of benzene ring of NP-10 was studied using UV-absorbance at 277 nm in chloroform. Results showed that only little of benzene ring was degraded.     

Closing the ring: historical biogeography of the salamander ring species Ensatina eschscholtzii

Aim The salamander Ensatina eschscholtzii Gray is a classic example of a ring species, or a species that has expanded around a central barrier to form a secondary contact characterized by species‐level divergence. In the original formulation of the ring species scenario, an explicit biogeographical model was proposed to account for the occurrence of intraspecific sympatry between two subspecies in southern California (the ‘southern closure’ model). Here we develop an alternative ring species model that is informed by the geomorphological development of the California Coast Ranges, and which situates the point of ring closure in the Monterey Bay region of central coastal California (the ‘Monterey closure’ model). Our study has two aims. The first is to use phylogenetic methods to evaluate the two competing biogeographical models. The second is to describe patterns of phylogeographical diversity throughout the range of the Ensatina complex, and to compare these patterns with previously published molecular systematic data. Location Western North America, with a focus on the state of California, USA. Methods We obtained mitochondrial DNA sequence data from 385 individuals from 224 populations. A phylogeny was inferred using Bayesian techniques, and the geographical distributions of haplotypes and clades were mapped. The two biogeographical ring species models were tested against our Bayesian topology, including the associated Bayesian 95% credible set of trees. Results High levels of phylogeographical diversity were revealed, especially in central coastal and northern California. Our Bayesian topology contradicts the Monterey closure model; however, 0.08% of the trees in our Bayesian 95% credible set are consistent with this model. In contrast, the classic ring species biogeographical model (the southern closure model) is consistent with our Bayesian topology, as were 99.92% of the trees in our 95% credible set. Main conclusions Our Bayesian phylogenetic analysis most strongly supports the classic ring species model, modified to accommodate an improved understanding of the complex geomorphological evolution of the California Coast Ranges. In addition, high levels of phylogeographical diversity in central and northern California were identified, which is consistent with the striking levels of allozymic differentiation reported previously from those regions.     

Studies on the Accumulation of 5(4)-Amino-4(5)-imidazolecarboxamide by Escherichia coli in a Shaking Culture

In the previous paper the author reported that 5(4)-amino-4(5) -imidazolecarboxamide (AICA) was accumulated in peptone medium by Escherichia coli strain B grown as a shaking culture in the absence of sulfonamide inhibitor and glucose. It appeared from the further investigations that l-tryptophan would not replace peptone for the accumulation. However, it was found that indole produced from l-tryptophan by E. coli gave pink color by the Bratton nad Marshall method. In order to eliminate the effect of indole, the procedure by petroleum-ether treatment was applied and it was ascertained that E. coli had an ability to accumulate AICA and AICA-riboside in the peptone or L-tryptophan medium without glucose and sulfonamide inhibitor. But the concentrations of AICA and AICA-riboside measured by the above procedure were smaller than those determined by the Bratton and Marshall method which measured indole produced by the bacteria at the same time.     

Synthesis of single- and double-13C-labeled cholesterol oleate

Cholesterol oleate with the 13C-label in oleic acid at the carbonyl and/or in the sterol ring at position 4 was synthesized by two methods: (1) cholesterol was condensed with oleic anhydride, prepared from [1-13C] oleic acid, in the presence of dimethylaminopyridine (DMAP) in anhydrous chloroform at room temperature for 4--5 h; (2) cholesterol or 13C-enriched cholesterol at position 4 were reacted with 90% [1-13C]-oleic acid in the presence of dicyclohexylcarbodiimide (DCC) and DMAP at room temperature in anhydrous chloroform for 1.25 h. The single-13C and double-13C-labeled cholesterol oleate were obtained in 90% yields after purification by silicic acid column chromatography. Their purity was assessed by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) and 13C-NMR spectroscopy. Tritium-labeled cholesterol oleate was also synthesized by method 1 using the fatty acid anhydride.     

Novel Acyclic Derivatives of Aica-Riboside (1-(β-D-Ribopuranosyl)5-Amino-4-Imidazolecarboxamide), Potential Antiviral Agents

Abstract

A synthetic approach is described to obtain from AICA-riboside acyclic analogues of 2′-deoxyribosides in which the C(2′)-C(3′) bond is cleaved and the natural configuration (E) at the anomeric C (1′)-position is retained.     

Synthesis of guanosine and its derivatives from 5-amino-1-beta-D-ribofuranosyl-4-imidazolecarboxamide. III. Formation of a novel cycloimidazole nucleoside and its cleavage reactions.

A new cycloimidazole nucleoside, 5-(1 inch -benzamido-1 inch-hydroxymethylene) amino-2', 1 inch-anhydro-1-beta-D-ribofuranosyl-4-imidazolecarboxamide (III) was synthesized by reaction of 5-amino-1-beta-D-ribofuranosyl-4-imidazolecarboxamide (AICA-riboside) with benzoyl isothiocyanate followed by methylation with methyl iodide. The structure of III was elucidated on the basis of its nmr spectra and chemical reactions. Of special interest are reactions of III with various nucleophiles. For example, guanosine (IX) was obtained by amination of III wtih ammonia in 72% yield. Analogous reactions of III with methylamine and dimethylamine gave N2-methylguanosine (X) and N2-dimethylguanosine (XI), respectively. Refluxing of III in alkaline solution afforded xanthosine (VII). The probable mechanism of formation and facile ring-opening of III is also discussed.     

Synthesis and structural studies of N-p-toluensulfonyl cyclodipeptides

In view of the chemical and structural interest of cyclopeptides bearing an electron withdrawing substituent directly bonded at the amide nitrogen atom, the two N-p-toluensulfonyl (N-tosyl) derivatives cyclo[-Phe(Tos)-D-Phe-] (I) and cyclo[-Phe(Tos)-D-Pro-] (II) have been synthesized and their stereochemistry defined. The molecular structure of I, as determined by x-ray diffraction analysis, is reported together with 1H-nmr parameters indicating the preferred rotameric conformation in chloroform solution. The N-tosyl group alters the geometry of the cyclodipeptide ring by lengthening both the N-C bonds departing from the tosylated nitrogen and reducing the corresponding ring angle. The 6-membered peptide ring adopts an unusual "sofa" conformation with the Tos-Phe C alpha atom deviating 0.230(3) A out of the mean plane of the other five ring atoms. One of the two S-O bonds forms a planar system that involves the tosylated nitrogen and the corresponding amide carbonyl. In the crystal, both the benzylic side chains are folded over the heterocyclic ring, whereas in chloroform solution, the benzylic side chain of the D-Phe prefers an extended conformation.     

Two distinct modes of myosin assembly and dynamics during epithelial wound closure

Actomyosin contraction powers the sealing of epithelial sheets during embryogenesis and wound closure; however, the mechanisms are poorly understood. After laser ablation wounding of Madin-Darby canine kidney cell monolayers, we observed distinct steps in wound closure from time-lapse images of myosin distribution during resealing. Immediately upon wounding, actin and myosin II regulatory light chain accumulated at two locations: (1) in a ring adjacent to the tight junction that circumscribed the wound and (2) in fibers at the base of the cell in membranes extending over the wound site. Rho-kinase activity was required for assembly of the myosin ring, and myosin II activity was required for contraction but not for basal membrane extension. As it contracted, the myosin ring moved toward the basal membrane with ZO-1 and Rho-kinase. Thus, we suggest that tight junctions serve as attachment points for the actomyosin ring during wound closure and that Rho-kinase is required for localization and activation of the contractile ring.     

Highly enantioselective synthesis, crystal structure, and circular dichroism spectroscopy of (R)-bambuterol hydrochloride

The present article describes the asymmetric synthesis of (R)-bambuterol hydrochloride based on 1-(3,5-dihydroxyphenyl)ethanone as starting material, which was esterified by dimethylcarbamic chloride, and brominated by copper (II) bromide. Then the carbonyl group was reduced efficiently using (-)-B-chlorodiisopinocamphenylborane [(-)-DIP-chloridetrade mark] as an asymmetrical reducing agent. Followed by epoxide ring closure with NaOH and ring expansion with tert-butylamine led to the desired product (R)-bambuterol with e.e. up to 99%. The optical properties and absolute configuration of (R)-bambuterol hydrochloride were further investigated using circular dichroism spectroscopy and X-ray single crystal analysis.     

Synthesis and biological activity of a cyclic pseudohexapeptide analog of somatostatin

A cyclic pseudohexapeptide analog of somatostatin, cyclo(Pro psi[ CH2S ]Phe-D-Trp-Lys-Thr-Phe) was synthesized by solid phase methods and diphenylphosphoryl azide ring closure. The resulting crystalline compound possessed 23% of the growth hormone inhibitory activity of the parent tetradecapeptide and approximately 6% of the activity of the all-amide cyclic hexapeptide analog in spite of the absence of one of two postulated intramolecular hydrogen bonds.     

Fungal Transformation of the Tricyclic Antidepressant Amoxapine: Identification of N-Carbomethoxy Compounds Formed as Artifacts by Phosgene in Chloroform used for the Extraction of Metabolites

The biotransformation of the antidepressant drug amoxapine by Cunninghamella elegans formed three metabolites, 7-hydroxyamoxapine, N-formyl-7-hydroxyamoxapine, and N-formylamoxapine; two other compounds were only present when chloroform was used in the extraction process. All five of the compounds were separated by reversed-phase HPLC, then analyzed by ¹H NMR and mass spectrometry, and by ¹³C NMR when sample quantities permitted. The artifacts were identified as N-carbomethoxy-7-hydroxyamoxapine and N-carbomethoxyamoxapine. Phosgene is a decomposition product of chloroform that can form carbomethoxy compounds at the secondary nitrogen of a piperazine ring in an alcoholic solution. Since N-carbomethoxy compounds were not observed when ethyl acetate was used for extraction of the culture medium, they were considered artifacts and not metabolites. These findings suggest that chloroform should be tested for the formation of phosgene before using it to extract any compound with a piperazine ring or any other amine-containing structure.     

Determination of the extent of DNA bending by an adenine-thymine tract

We determined the magnitude of the bend induced in DNA by an adenine-thymine tract by measuring the rate of cyclization of DNA oligonucleotides containing phased A tracts. A series of linear multimers with 2-bp single-stranded ends, in which the (A.T)6 tracts are separated by CG2-3C sequences and are positioned 10 and 11 bp apart alternately, were prepared from 21 bp long synthetic duplexed deoxyoligonucleotides. The cyclization rates of the multimers (105-210 bp) and the bimolecular association rate of the 84 bp long multimer were measured in the presence of DNA ligase. From the rate constants of the cyclization and bimolecular association reactions, ring closure probabilities were obtained for the multimers. The systematically bent molecules were simulated by Monte Carlo methods, and the ring closure probabilities were calculated for a given set of junction bend angles. By comparing the calculated values of ring closure probabilities to experimental values and adjusting the junction bend angles to fit experimental values, the extent of bending at the junctions (or the extent of bending for an adenine tract) was determined. We conclude that an A6 tract bends the DNA helix by 17-21 degrees.     

Bond-optimized ring closure for proline: comparison of conformations and semiempirical energies with small molecule X-ray structures

A method is described for generating proline ring structures by successive addition of atoms, wherein ring closure is achieved by optimizing the fit to known ring bond-angles and one closing bond-length ("bond-optimized ring closure"). Two ring torsion angles are fixed independently within broad, allowed ranges, and the remaining torsion angles are determined uniquely in most cases. The independent torsion angles are chosen as phi and chi 2, and ring closure is achieved without prohibitive strain through most of the ranges -130 degrees less than phi less than -20 degrees and -60 degrees less than chi 2 less than 60 degrees. Comparisons of predicted ring structures to 191 X-ray diffraction structures from the literature, starting with the known values of phi and chi 2, yielded root-mean-square deviations of 4.8 degrees in chi 1, 4.7 degrees in chi 3, 8.3 degrees in chi 4, and 0.3-2% in the ring bond angles and the N-C delta distance. Semiempirical energies were calculated for the optimized structures using three sets of energy parameters from the literature. The energy surfaces show broad minima coinciding with the torsion angle regions in which the highest concentrations of observed structures are found. Two of the sets of energy parameters produce double minima corresponding to the "up" and "down" puckered conformations.     

AICA-ribosiduria: a novel, neurologically devastating inborn error of purine biosynthesis caused by mutation of ATIC

In a female infant with dysmorphic features, severe neurological defects, and congenital blindness, a positive urinary Bratton-Marshall test led to identification of a massive excretion of 5-amino-4-imidazolecarboxamide (AICA)-riboside, the dephosphorylated counterpart of AICAR (also termed "ZMP"), an intermediate of de novo purine biosynthesis. ZMP and its di- and triphosphate accumulated in the patient's erythrocytes. Incubation of her fibroblasts with AICA-riboside led to accumulation of AICAR, not observed in control cells, suggesting impairment of the final steps of purine biosynthesis, catalyzed by the bifunctional enzyme AICAR transformylase/IMP cyclohydrolase (ATIC). AICAR transformylase was profoundly deficient, whereas the IMP cyclohydrolase level was 40% of normal. Sequencing of ATIC showed a K426R change in the transformylase region in one allele and a frameshift in the other. Recombinant protein carrying mutation K426R completely lacks AICAR transformylase activity.     

Stability and fine structure of eukaryotic DNA rings in formamide

Folded rings formed from Drosophila and Necturus DNA fragments were examined by electron microscopy in increasing concentrations of formamide, in an effort to identify regions of non-homology within the closure region. Unusual closure regions of this type were not found, in spite of an extensive search. If such regions exist, they must be too short to be detectable (<50 nucleotides), or longer than 1000 nucleotides. In this latter case, they could not be contained within the overlap region of the ring. A study of the thermal (formamide) stability of these rings in relation to the observed closure lengths suggests that extensive (>2 to 3%) mismatching is not possible. At higher formamide concentrations, some rings will partly denature, yet remain circular because the closure region remains intact.     

Isolation and identification of antitumor promoters from the seeds of Cassia tora

A methanol extract of Cassia tora seeds was successively partitioned with diethyl ether, chloroform, ethyl acetate, and water, and the antitumor-promoting activity of the solvent fractions was determined by inhibition of Epstein- Barr virus early antigen (EBV-EA) activation induced by teleocidin B-4 in Raji cells. The diethyl ether (68.7%) and chloroform (91.2%) fractions and the hydrolysate (94.3%) of the ethyl acetate fraction had strong inhibitory activities. The chloroform and ethyl acetate fractions were chromatographed on silica gel and further purified by HPLC. Three active compounds, obtusifolin-2-glucoside (75.0%), chryso-obtusin-6-glucoside (56.8%), and norrubrofusarin- 6-glucoside (39.4%), were obtained from the ethyl acetate fraction, and two active compounds, questin (97.9%) and chryso-obtusin (53.8%), were isolated from the chloroform fraction.