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Cytogenetics and Cell Genetics 1981The role of guanine deaminase in selective cellular resistance to 8-azaguanine was examined, using eight mammalian cell lines and their subclonal derivatives isolated on...
The role of guanine deaminase in selective cellular resistance to 8-azaguanine was examined, using eight mammalian cell lines and their subclonal derivatives isolated on the basis of increasing resistance to this drug. 8-Azaguanine and 6-thioguanine are synthetic analogs of guanine and are lethal to cells with normal hypoxanthine phosphoribosyltransferase (HPRT) activity. In principle, however, HPRT-positive cells could become selectively resistant to 8-azaguanine if, by any mechanism, the cells expressed higher levels of guanine deaminase. This is because 8-azaguanine, but not 6-thioguanine, is converted by this enzyme to a noncytotoxic metabolite, 8-azaxanthine. Our study shows that HPRT-positive cells inherently resistant to relatively high levels of 8-azaguanine contain high levels of guanine deaminase. In general, guanine deaminase activity was higher in 8-azaguanine-resistant cells, regardless of their HPRT activity. Our results support the view that elevated guanine deaminase activity constitutes a potential mechanism of selective 8-azaguanine resistance in cells with normal HPRT activity. Guanine deaminase levels were significantly elevated in HPRT-positive cells briefly exposed to sublethal concentrations of 8-azaguanine, but this elevation was transient. Long-term exposure of cells to increasingly higher levels of the drug did not lead to high stable levels of guanine deaminase, indicating that 8-azaguanine is not an inducer of guanine deaminase in the cells examined.
Topics: Aminohydrolases; Azaguanine; Cell Line; Clone Cells; Drug Resistance; Guanine Deaminase; Guanosine; Hypoxanthine Phosphoribosyltransferase
PubMed: 7273856
DOI: 10.1159/000131598 -
Experientia Jan 1972
Topics: Azaguanine; Hydroxyurea
PubMed: 5013040
DOI: 10.1007/BF01928230 -
Journal of Immunological Methods Dec 1991A simple and rapid one-step method for establishing azaguanine resistant (Agr) hybridomas, which can be used as a fusion partner for the construction of triomas...
A simple and rapid one-step method for establishing azaguanine resistant (Agr) hybridomas, which can be used as a fusion partner for the construction of triomas (hybridoma x splenocyte), has been developed. The method relies on cloning the hybridoma cells in soft agar supplemented with 20 micrograms/ml 8-azaguanine. The drug-resistant subclones were isolated after 3-5 days, in comparison with 4-5 weeks reported for the conventional adaptation method. The high frequency (about 10(-3) of Agr-mutants achieved by the cloning method was demonstrated with five different hybridoma clones. One of the derived Agr-hybridomas was fused with mouse immune spleen cells in order to demonstrate its suitability for the generation of triomas secreting bispecific monoclonal antibodies.
Topics: Animals; Antibody Specificity; Azaguanine; Cell Fusion; Drug Resistance; Horseradish Peroxidase; Hybridomas; In Vitro Techniques; Mice; Rabies virus; Spleen
PubMed: 1765658
DOI: 10.1016/0022-1759(91)90333-b -
Humangenetik 1972
Topics: Adenine; Azaguanine; Cells, Cultured; Diploidy; Drug Resistance; Electrophoresis; Fibroblasts; Gels; Genes; Genetics, Medical; Humans; Hypoxanthines; Lesch-Nyhan Syndrome; Male; Molecular Biology; Mutation; Pentosyltransferases; Sex Chromosomes
PubMed: 4647448
DOI: 10.1007/BF00393992 -
Mutation Research Feb 1983Chinese hamster V79 cells were mutagenized with ethyl methanesulfonate at various concentrations. Clones resistant to 8-azaguanine (20 and 80 micrograms/ml) or... (Comparative Study)
Comparative Study
Chinese hamster V79 cells were mutagenized with ethyl methanesulfonate at various concentrations. Clones resistant to 8-azaguanine (20 and 80 micrograms/ml) or 6-thioguanine (4 micrograms/ml) were selected at different times after the treatments. The total yield of induced mutations was only slightly affected by the kind and concentration of purine analog used in the selection. However, full phenotypic expression of the mutants selected with 8-azaguanine was achieved earlier than that of mutants resistant to 6-thioguanine. This result seems to be best explained by the reported lower affinity of 8-azaguanine for the wild-type HGPRT enzyme, thus providing evidence that, in this gene-mutation assay, the phenotypic expression time has a physiological component.
Topics: Animals; Azaguanine; Cell Survival; Clone Cells; Cricetinae; Cricetulus; Drug Resistance; Ethyl Methanesulfonate; Hypoxanthine Phosphoribosyltransferase; Mutation; Phenotype; Thioguanine; Time Factors
PubMed: 6865989
DOI: 10.1016/0027-5107(83)90179-3 -
Mutation Research Mar 1976Synchronous Chinese hamster ovary cells were irradiated in G1 or S phase. Colony survival in Alpha MEM medium with dialyzed serum was determined with or without 15...
Synchronous Chinese hamster ovary cells were irradiated in G1 or S phase. Colony survival in Alpha MEM medium with dialyzed serum was determined with or without 15 mug/ml 8-azaguanine (AG). An expression period of over three generations (multiplicity of 20) was utilized, with expression times ranging from 58 to 114 h. Both G1 and S phase were practically identical in sensitivity to X-ray-induced mutations, with mutant frequency/viable cell/rad ranging from 1 X 10(-7) (75-100 rad) to 8 X 10(-7) (1000 rad). The spontaneous mutation rate, shown by Luria-Delbruck fluctuation analysis, was 5 X 10(-7) per generation. Thirty-three mutants, isolated at random and grown for over 30 generations in the absence of AG, were analyzed for plating efficiency (PE) in different concentrations of AG or in hypoxanthine-aminopterin-thymidine (HAT) medium. Of these, 64% were resistant (PE greater than 0.1) to 7.5 mug/ml AG, 85% to 5.0 mug/ml, and 91% to 3.5 mug/ml. Only 42% showed possible hypoxanthine-phosphoribosyltransferase (hprtase) deficiency as evidenced by HAT sensitivity (PE less than 0.1). Wild type controls exhibited PE's in 3.5 mug/ml AG of less than 0.001 and in HAT of greater than 0.5. Of ten mutants studied, all demonstrated survival response to radiation similar to wild type cells (D0 of approx. 120 rad). For radiation protection standards, the radiation dose required to induce mutations at a rate equal to that occurring spontaneously is called the doubling dose. The doubling dose observed for acute irradiation was about 3 rad and was estimated to be 10-60 rad for chronic irradiation, similar to that often reported for in vivo studies.
Topics: Aminopterin; Azaguanine; Cell Division; Cell Survival; Clone Cells; Dose-Response Relationship, Radiation; Drug Resistance; Hypoxanthines; Karyotyping; Mutation; Radiation Genetics; Thymidine; X-Rays
PubMed: 1264111
DOI: 10.1016/0027-5107(76)90223-2 -
The Journal of Biological Chemistry Nov 1951
Topics: Animals; Azaguanine; Guanine; Haplorhini; Mice
PubMed: 14907690
DOI: No ID Found -
Chembiochem : a European Journal of... Sep 2019The impact of 7-deaza-8-azaguanine (DAG) and 7-deaza-8-azaisoguanine (DAiG) modifications on the geometry and stability of the G:C Watson-Crick (cWW) base pair and the...
Structural and Energetic Impact of Non-natural 7-Deaza-8-azaguanine, 7-Deaza-8-azaisoguanine, and Their 7-Substituted Derivatives on Hydrogen-Bond Pairing with Cytosine and Isocytosine.
The impact of 7-deaza-8-azaguanine (DAG) and 7-deaza-8-azaisoguanine (DAiG) modifications on the geometry and stability of the G:C Watson-Crick (cWW) base pair and the G:iC and iG:C reverse Watson-Crick (tWW) base pairs has been characterized theoretically. In addition, the effect on the same base pairs of seven C7-substituted DAG and DAiG derivatives, some of which have been previously experimentally characterized, has been investigated. Calculations indicate that all of these modifications have a negligible impact on the geometry of the above base pairs, and that modification of the heterocycle skeleton has a small impact on the base-pair interaction energies. Instead, base-pair interaction energies are dependent on the nature of the C7 substituent. For the 7-substituted DAG-C cWW systems, a linear correlation between the base-pair interaction energy and the Hammett constant of the 7-substituent is found, with higher interaction energies corresponding to more electron-withdrawing substituents. Therefore, the explored modifications are expected to be accommodated in both parallel and antiparallel nucleic acid duplexes without perturbing their geometry, while the strength of a base pair (and duplex) featuring a DAG modification can, in principle, be tuned by incorporating different substituents at the C7 position.
Topics: Azaguanine; Base Pairing; Cytosine; Hydrogen Bonding; Molecular Structure; Thermodynamics
PubMed: 30983115
DOI: 10.1002/cbic.201900245 -
Journal of Bacteriology Dec 1964Johnson, Russell C. (University of Minnesota, Minneapolis), and Palmer Rogers. Differentiation of pathogenic and saprophytic leptospires with 8-azaguanine. J. Bacteriol....
Johnson, Russell C. (University of Minnesota, Minneapolis), and Palmer Rogers. Differentiation of pathogenic and saprophytic leptospires with 8-azaguanine. J. Bacteriol. 88:1618-1623. 1964.-The use of the purine analogue, 8-azaguanine, as a differential agent for the separation of pathogenic and saprophytic leptospires was investigated. Growth of strains of the saprophyte Leptospira biflexa was almost insensitive to the bacteriostatic action of 8-azaguanine at concentrations varying from 25 to 600 mug/ml; these saprophytic leptospires were serially transferred five times in media containing 225 mug without any change in growth rate or cell yield. In contrast, decreased growth rate and cell yield of the pathogenic serotypes were observed with 25 to 50 mug/ml of 8-azaguanine. Complete inhibition of growth occurred at concentrations of 100 mug/ml and above. A medium containing 225 mug/ml of 8-azaguanine was successfully used to differentiate 20 serotypes of pathogenic leptospires and 10 saprophytic strains. L. andaman CH11, L. semarang Veldrat S1 73, and L. andaman Correa, were classified with the L. biflexa strains on the basis of their growth response to 8-azaguanine.
Topics: Antimetabolites; Azaguanine; Fluorouracil; Leptospira; Leptospira interrogans serovar icterohaemorrhagiae; Leptospirosis; Pharmacology; Research
PubMed: 14244050
DOI: 10.1128/jb.88.6.1618-1623.1964 -
Molecular & General Genetics : MGG Dec 1976Anomalies in selection render 8-azaguanine unsuitable as a selective agent for screening forward mutations in continuour cultures of Sch. pombe. This system may,...
Anomalies in selection render 8-azaguanine unsuitable as a selective agent for screening forward mutations in continuour cultures of Sch. pombe. This system may, however, provide tha basis for an enrichment method for the simultaneous isolation of mutants at two loci.
Topics: Ascomycota; Azaguanine; Drug Resistance, Microbial; Genetic Techniques; Mutation; Schizosaccharomyces; Selection, Genetic
PubMed: 796682
DOI: 10.1007/BF00332895