Imidazopurinones are markers of physiological genomic damage linked to DNA instability and glyoxalase 1-associated tumour multidrug resistance

Glyoxal and methylglyoxal are reactive dicarbonyl metabolites formed and metabolized in physiological systems. Increased exposure to these dicarbonyls is linked to mutagenesis and cytotoxicity and enhanced dicarbonyl metabolism by overexpression of glyoxalase 1 is linked to tumour multidrug resistance in cancer chemotherapy. We report herein that glycation of DNA by glyoxal and methylglyoxal produces a quantitatively important class of nucleotide adduct in physiological systems—imidazopurinones. The adduct derived from methylglyoxal-3-(2′-deoxyribosyl)-6,7-dihydro-6,7-dihydroxy-6/7-methylimidazo-[2,3-b]purine-9(8)one isomers—was the major quantitative adduct detected in mononuclear leukocytes in vivo and tumour cell lines in vitro. It was linked to frequency of DNA strand breaks and increased markedly during apoptosis induced by a cell permeable glyoxalase 1 inhibitor. Unexpectedly, the DNA content of methylglyoxal-derived imidazopurinone and oxidative marker 7,8-dihydro-8-oxo-2′-deoxyguanosine were increased moderately in glyoxalase 1-linked multidrug resistant tumour cell lines. Together these findings suggest that imidazopurinones are a major type of endogenous DNA damage and glyoxalase 1 overexpression in tumour cells strives to counter increased imidazopurinone formation in tumour cells likely linked to their high glycolytic activity

MODELOS ENERGÉTICOS EN PSICOANÁLISIS. DIFERENCIAS ENTRE SIGMUND FREUD Y JACQUES LACAN

There are in psychoanalysis different models to account for the dynamic dimension. This paper compares the models of "energy" proposed by both Sigmund Freud and Jacques Lacan and presents their main consequences for the clinic

Optimisation of batch culture conditions for cyclodextrin glucanotransferase production from <it>Bacillus circulans</it> DF 9R

Abstract Background The extracellular enzyme cyclodextrin glucanotransferase (CGTase) synthesizes cyclic malto-oligosaccharides called cyclodextrins (CDs) from starch and related α-1,4-glucans. CGTases are produced by a variety of bacteria, mainly Bacillus species, by submerged culture in complex medium. CGTases differ in the amount and types of CDs produced. In addition, CGTase production is highly dependent on the strain, medium composition and culture conditions. Therefore we undertook this study with a newly isolated strain of Bacillus circulans. Results CGTase activity produced from Bacillus circulans DF 9R was optimised in shake flasks using a combination of conventional sequential techniques and statistical experimental design. Effects of nutrients, including several carbon, nitrogen and mineral sources, were assayed. The selected minimal medium consisted of 1.5 % cassava starch, 0.4 % ammonium sulphate, 0.1 M phosphate buffer, 0.002 % MgSO4 and 0.002 % FeSO4. The optimal concentrations of carbon and nitrogen sources were determined using a central composite design. Maximum CGTase activity obtained in supernatants was 5.8 U/mL in 48 h of incubation. Optimal conditions for enzyme production also included an initial pH of 8.3 and 37°C as the incubation temperature. Cell growth and CGTase production profile were not linked to each other, suggesting that enzyme production/secretion is not growth–associated but mainly a late-log phase event. Conclusion We have screened conditions for optimal CGTase production. The selected minimal medium contained starch, ammonium, Mg2+ and Fe2+ as essential nutrients. As an additional advantage, this medium does not require complex nitrogen sources with varying and unknown composition.</p

Cyclodextrin production by cyclodextrin glycosyltransferase from Bacillus circulans DF 9R

Cyclodextrins (CD) are cyclic oligosaccharides with multiple applications in the food, pharmaceutical, cosmetic, agricultural and chemical industries. In this work, the conditions used to produce CD with cyclodextrin glycosyltransferase from Bacillus circulans DF 9R were optimized using experimental designs. The developed method allowed the partial purification and concentration of the enzyme from the cultural broth and, subsequently, the CD production, using the same cassava starch as enzyme adsorbent and as substrate. Heat-treatment of raw starch at 70 C for 15 min in the presence of adsorbed cyclodextrin glycosyltransferase allowed the starch liquefaction without enzyme inactivation. The optimum conditions for CD production were: 5% (w/v) cassava starch, 15 U of enzyme per gram of substrate, reaction temperature of 56 C and pH 6.4. After 4 h, the proportion of starch converted to CD reached 66% (w/w) and the weight ratio of a-CD:b-CD:c-CD was 1.00:0.70:0.16.Fil: Szerman, Natalia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Schroh, Ignacio. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Rossi, Ana Lía. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Rosso, Adriana Mabel. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Krymkiewicz, Norberto. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Ferrarotti, Susana Alicia. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina

Cyclodextrin glycosyltransferase from Bacillus circulans DF 9R: Activity and kinetic studies

Activity characteristics and kinetic aspects of a cyclodextrin glycosyltransferase (CGTase) from Bacillus circulans DF 9R were studied. A mixture of α-, β- and γ-cyclodextrins (CDs), glucose, maltose and negligible amounts of longer linear dextrins were produced from gelatinized amylose, amylopectin and starch from different sources. In the coupling reaction, CDs were the substrates in the presence of acceptors such as maltose and/or longer oligosaccharides. From oligosaccharides formed by three or more glucose units, this enzyme produced linear chains of several lengths which were then cyclized. CGTase catalytic efficiency was compared employing an analytical grade starch and cassava starch for food use. Since the results obtained were similar for both starches, the use of an economic starch is an advantage. CGTase was inhibited by the substrate and its own products. Starch concentrations over 20 mg/mL inhibited the cyclizing activity. CDs behaved as competitive inhibitors and maltose as an uncompetitive inhibitor while maltotriose showed a mixed inhibition pattern. Limit dextrins showed a scarce inhibitory effect on enzyme activity. CD production could be improved with an ultrafiltration membrane reactor for continuous removal of the products; the starch concentration should be maintained below an inhibitory concentration and limit dextrins would remain in the reactor without affecting enzyme activity.Fil: Szerman, Natalia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Rodríguez Gastón, Jorgelina Andrea. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Costa, Hernán. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Krymkiewicz, Norberto. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina.Fil: Ferrarotti, Susana Alicia. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina