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  • 1
    Electronic Resource
    Electronic Resource
    CYTOGENETICS AND EVOLUTION OF PRIMATES (1962)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 102 (1962), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1962.tb13644.x
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  • 2
    Electronic Resource
    Electronic Resource
    MUTATION SYSTEMS IN CULTURED MAMMALIAN CELLS (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 407 (1983), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1983.tb47827.x
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  • 3
    Electronic Resource
    Electronic Resource
    Partial trisomy of the long arm of human chromosome 1 as demonstrated by in situ hybridization with 5S ribosomal RNA (1977)
    Springer
    Human genetics 〈Berlin〉 36 (1977), S. 25-33 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In a newborn boy with multiple malformations, a tandem duplication was detected at the distal end of the long arm of one human chromosome 1. The Giemsa bands, 1q31 to 1q43–44, were repeated serially. Since 5S rRNA genes are located at 1q42–43, in situ hybridization of 125I 5S rRNA with fixed chromosome preparations was used to confirm the chromosomal duplication. The infant exhibited numerous developmental and clinical abnormalities as might be expected with an abnormality of chromosome structure relating to a ribosome component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390432
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  • 4
    Electronic Resource
    Electronic Resource
    Pleiotropic mutants of Chinese hamster cells with altered cytidine 5′-triphosphate synthetase (1984)
    Springer
    Biochemical genetics 22 (1984), S. 701-715 
    Details
    ISSN: 1573-4927
    Keywords: cytidine 5′-triphosphate synthetase ; Chinese hamster cells ; pyrimidine metabolism ; K m mutants ; nucleotide pools ; feedback inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Following chemical mutagenesis and multiple-step indirect selection, four clones of Chinese hamster V79 cells were isolated which exhibited auxotrophy for thymidine, deoxycytidine, or deoxyuridine but not for cytidine or uridine. All were resistant to uridine, 3-deazauridine, 5-fluorouridine, thymidine, and cytosine arabinoside at concentrations that were toxic to wild-type V79 cells. The cytidine 5′-triphosphate (CTP) and deoxycytidine 5′-triphosphate (dCTP) pools in the mutants were expanded, but the uridine 5′-triphosphate (UTP) pool either decreased or remained unchanged relative to the wild-type level. Furthermore, since the parental cells appear to be deficient in dCMP deaminase activity and CTP (or one of its metabolites) has been shown to inhibit uridine 5′-diphosphate (UDP) reduction, an elevated CTP level should lead to the observed thymidine auxotrophy. It also explains the joint resistance of mutant clones to thymidine and cytosine arabinoside. The change in the ratio of intracellular dCTP to thymidine 5′-triphosphate (dTTP) may be responsible for the elevation in the rates of spontaneous mutations in these mutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00485854
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  • 5
    Electronic Resource
    Electronic Resource
    The kinetics and feedback inhibition of cytidine 5′-triphosphate synthetase in wild-type and mutant Chinese hamster cells (1984)
    Springer
    Biochemical genetics 22 (1984), S. 717-727 
    Details
    ISSN: 1573-4927
    Keywords: cytidine 5′-triphosphate (CTP) ; uridine 5′-triphosphate ; CTP synthetase ; Chinese hamster fibroblasts ; enzyme kinetics ; feedback inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The kinetics and cytidine 5′-triphosphate (CTP) feedback inhibition of CTP synthetase in wild-type and four mutants of Chinese hamster V79 cells have been studied. The enzymes of the wild type and three of the four mutants exhibited positive cooperativity with the substrate uridine 5′-triphosphate (UTP). Three of the mutants had K m app and S 50 valuves distinctly greater than those of the wild type, while the fourth mutant had values similar to those of the wild type. all four mutants exhibited resistance to CTP feedback inhibition, while the wild type was sensitive to such inhibition. It is postulated that a single mutational event in each mutant had caused a concomitant change of the enzyme in its binding both to the substrate UTP and to the end-product CTP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00485855
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  • 6
    Electronic Resource
    Electronic Resource
    Apparent synergism between amino donors for CTP synthesis in Chinese hamster fibroblasts (1983)
    Springer
    Molecular and cellular biochemistry 57 (1983), S. 167-175 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary The synergistic effects of potential amino donors were studied in the assay of CTP synthetase in extracts of Chinese hamster fibroblasts. We found that L-glutamine was not effective as the sole amino donor, but combinations of L-glutamine with NH4HCO3, L-arginine or potassium phosphate did result in the conversion of UTP to CTP. L-arginine or potassium phosphate were also not effective when used alone, and NH4HCO3 was only slightly effective. Our studies demonstrate that the individual synergistic combinations were not additive; multiple combinations of components decreased rather than increased the formation of CTP. The synergistic combinations of L-glutamine with either NH4HCO3 or L-arginine had an absolute requirement for ATP; when ATP and PEP were absent no conversion of UTP to CTP occurred. The presence of GTP in a reaction mixture slightly increased the formation of CTP when L-glutamine and NH4HCO3 were used and substantially increased CTP formation when L-glutamine and L-arginine were used.De novo CTP synthesis was greatly reduced when nonradioactive CTP was added to an assay mixture, suggesting feedback inhibition. A TLC procedure has been developed that allows for the direct separation of UTP and CTP without requiring prior conversion to the mononucleotide or nucleoside level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00849193
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  • 7
    Electronic Resource
    Electronic Resource
    Apparent synergism between amino donors for CTP synthesis in Chinese hamster fibroblasts (1983)
    Springer
    Molecular and cellular biochemistry 57 (1983), S. 167-175 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary The synergistic effects of potential amino donors were studied in the assay of CTP synthetase in extracts of Chinese hamster fibroblasts. We found that L-glutamine was not effective as the sole amino donor, but combinations of L-glutamine with NH4HCO3, L-arginine or potassium phosphate did result in the conversion of UTP to CTP. L-arginine or potassium phosphate were also not effective when used alone, and NH4HCO3 was only slightly effective. Our studies demonstrate that the individual synergistic combinations were not additive; multiple combinations of components decreased rather than increased the formation of CTP. The synergistic combinations of L-glutamine with either NH4HCO3 or L-arginine had an absolute requirement for ATP; when ATP and PEP were absent no conversion of UTP to CTP occurred. The presence of GTP in a reaction mixture slightly increased the formation of CTP when L-glutamine and NH4HCO3 were used and substantially increased CTP formation when L-glutamine and L-arginine were used. De novo CTP synthesis was greatly reduced when nonradioactive CTP was added to an assay mixture, suggesting feedback inhibition. A TLC procedure has been developed that allows for the direct separation of UTP and CTP without requiring prior conversion to the mononucleotide or nucleoside level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223531
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  • 8
    Electronic Resource
    Electronic Resource
    Single-step selection of mammalian cell mutants deficient in CTP synthetase (1989)
    Springer
    Somatic cell and molecular genetics 15 (1989), S. 85-91 
    Details
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A single-step selection of Chinese hamster V79 cells deficient in CTP synthetase (CTPS −)is presented. The underlying principle of the direct selection is the differential and efficient killing of synchronized wild-type cells through incorporation of [3H]uridine and [3 H]thymidine. The CTPS − mutant cells were recovered by virtue of their not engaging in DNA synthesis, because (1) CTPS − cells are deficient in CTP synthetase and thus are unable to convert [3 H]UTP into [3 H]CTP, which eventually is converted into [3 H]dCTP and incorporated into DNA; (2) the growth of CTPS − mutant cells was arrested as a result of cytidine deprivation, thus escaping the killing by the incorporation of [3 H]thymidine. The isolated mutant clones are auxotrophic for cytidine and are stable in phenotype with a reversion frequency of less than 1 × 10 −7.The mutant cells have no or very low CTP synthetase activity when tested by in vitro CTP synthetase assay or by whole-cell [3 H]uridine labeling assay. This modified “tritium suicide” method combined with the S-phase cell synchronization could provide a powerful means for the recovery from the cell population of nondividing mutant cells that are auxotrophic for some special nutrient requirement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01534673
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  • 9
    Electronic Resource
    Electronic Resource
    Chromosomal location of human genes encoding major heat-shock protein HSP70 (1987)
    Springer
    Somatic cell and molecular genetics 13 (1987), S. 119-130 
    Details
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The HSP70 family of heat-shock proteins constitutes the major proteins synthesized in response to elevated temperatures and other forms of stress. In eukaryotes members of the HSP70 family also include a protein similar if not identical to bovine brain uncoating ATPase and glucose-regulated proteins. An intriguing relation has been established between expression of heat-shock proteins and transformation in mammalian cells. Elevated levels of HSP70 are found in some transformed cell lines, and viral and cellular gene products that are capable of transforming cells in vitro can also stimulate transcription of HSP70genes. To determine the organization of this complex multigene family in the human genome, we used complementary approaches: Southern analysis and protein gels of Chinese hamster-human somatic cell hybrids, and in situ hybridization to human chromosomes. We demonstrate that functional genes encoding HSP70 proteins map to human chromosomes 6, 14, 21, and at least one other chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01534692
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  • 10
    Electronic Resource
    Electronic Resource
    Inverse relationship between galactokinase activity and 2-deoxygalactose resistance in Chinese hamster ovary cells (1978)
    Springer
    Somatic cell and molecular genetics 4 (1978), S. 699-713 
    Details
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Galactokinase activity is reduced in 12 independent clones of Chinese hamster ovary cells resistant to 2-deoxygalactose. The frequency of resistant colonies is increased with chemical mutagens. The resistant phenotype is stable in the absence of selection. There is an inverse correlation between the levels of galactokinase activity and the cloning efficiency in deoxygalactose. Cells with high resistance have 1%or less of the enzyme activity observed in the parental cells; while cells with low resistance have 10–30% galactokinase activity. Studies with tetraploid hybrid cells reveal that resistance to deoxygalactose is a recessive trait and that cells with high resistance do not complement those with low resistance. In cell lines with low resistance, the K m for galactose, K i for deoxygalactose, K m for ATP, and thermolability were not significantly altered compared to sensitive parental cells. Although the possibility of mutation at the structural gene locus has not been ruled out, the reduced enzyme activity may also be due to mutation at a regulatory site which affects the number of galactokinase molecules per cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543159
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