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  • Activator  (2)
  • Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry  (2)
  • Life and Medical Sciences  (2)
  • Polya's theorem  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Complexes of block copolymers in solution: Tree approximation (1989)
    Springer
    Journal of statistical physics 57 (1989), S. 1069-1098 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Block copolymers ; generating function ; Polya's theorem ; gelation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We determine the statistical properties of block copolymer complexes in solution. These complexes are assumed to have the topological structure of (i) a tree or of (ii) a line-dressed tree. In case the structure is that of a tree, the system is shown to undergo a gelation transition at sufficiently high polymer concentration. However, if the structure is that of a line-dressed tree, this transition is absent. Hence, we show the assumption about the topological structure to be relevant for the statistical properties of the system. We determine the average size of the complexes and calculate the viscosity of the system under the assumption that the complexes geometrically can be treated as porous spheres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01020049
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  • 2
    Digitale Medien
    Digitale Medien
    Analysis of the chromosomal distribution of transposon-carrying T-DNAs in tomato using the inverse polymerase chain reaction (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 573-585 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Tomato ; Agrobacterium T-DNA ; Inverse PCR ; Activator ; Transposon tagging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We are developing a system for isolating tomato genes by transposon mutagenesis. In maize and tobacco, the transposon Activator (Ac) transposes preferentially to genetically linked sites. To identify transposons linked to various target genes, we have determined the RFLP map locations of Ac- and Dissociation (Ds)-carrying T-DNAs in a number of transformants. T-DNA flanking sequences were isolated using the inverse polymerase chain reaction (IPCR) and located on the RFLP map of tomato. The authenticity of IPCR reaction products was tested by several criteria including nested primer amplification, DNA sequence analysis and PCR amplification of the corresponding insertion target sequences. We report the RFLP map locations of 37 transposon-carrying T-DNAs. We also report the map locations of nine transposed Ds elements. T-DNAs were identified on all chromosomes except chromosome 6. Our data revealed no apparent chromosomal preference for T-DNA integration events. Lines carrying transposons at known map locations have been established which should prove a useful resource for isolating tomato genes by transposon mutagenesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00285281
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  • 3
    Digitale Medien
    Digitale Medien
    Complexes of block copolymers in solution: A graph-theoretical approach (1989)
    Springer
    Journal of statistical physics 57 (1989), S. 1099-1122 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Block copolymers ; generating function method ; Polya's theorem ; gelation ; nonnested structures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We determine the statistical properties of block copolymers in solution. These complexes are assumed to have the topological structure of connected graphs with “nonnested” loops and cycles. The generating function method is used to determine the number of topologically different complexes containing a given number of block copolymers. It is shown that at sufficiently high concentration the system undergoes a transition to a gel phase. Furthermore, the average number of polymers per complex is calculated. Finally, the relative increase in viscosity is found under the assumption that the complexes can be treated as porous spheres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01020050
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  • 4
    Digitale Medien
    Digitale Medien
    Use of the maize transposonsActivator andDissociation to show that phosphinothricin and spectinomycin resistance genes act non-cell-autonomously in tobacco and tomato seedlings (1993)
    Springer
    Transgenic research 2 (1993), S. 63-78 
    Details
    ISSN: 1573-9368
    Schlagwort(e): transposon ; Activator ; Dissociation ; cell-autonomous ; spectinomycin ; tomato ; phosphinothricin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cell-autonomous genes have been used to monitor the excision of both endogenous transposons in maize andAntirrhinum, and transposons introduced into transgenic plants. In tobacco andArabidopsis, the streptomycin phosphotransferase (SPT) gene reveals somatic excision of the maize transposonActivator (Ac) as green sectors on a white background in cotyledons of seedlings germinated in the presence of streptomycin. Cotyledons of tomato seedlings germinated on streptomycin-containing medium do not bleach, suggesting that a different assay for transposon excision in tomato is desirable. We have tested the use of the spectinomycin resistance (SPEC) gene (aadA) and a Basta resistance (BAR) gene (phosphinothricin acetyltransferase, or PAT) for monitoring somatic excision ofAc in tobacco and tomato. Both genetic and molecular studies demonstrate that genotypically variegated individuals that carry clones of cells from whichAc orDs have excised from either SPEC or BAR genes, can be phenotypically completely resistant to the corresponding antibiotic. This demonstrates that these genes act non-cell-autonomously, in contrast to the SPT gene in tobacco. Possible reasons for this difference are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01969379
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  • 5
    Digitale Medien
    Digitale Medien
    Duchenne muscular dystrophy and the neuromuscular junction: The utrophin link (1997)
    New York, NY : Wiley-Blackwell
    BioEssays 19 (1997), S. 747-750 
    Details
    ISSN: 0265-9247
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Although the precise function of utrophin at the postsynaptic membrane of the neuromuscular junction still remains unclear, despite recent genetic ‘knockout’ experiments(1,2), a separate study in a transgenic mouse model system for Duchenne muscular dystrophy (DMD) has nonetheless shown that overexpression of utrophin into extrasynaptic regions of muscle fibers can functionally compensate for the lack of dystrophin and alleviate the muscle pathology(3). In this context, the next step is to identify the mechanisms presiding over expression of utrophin at the neuromuscular synapse in attempts to induce its expression throughout DMD muscle fibers. In fact, additional studies have shown that an important DNA element contained with the utrophin promoter may confer synapse-specific expression to the utrophin gene(4,5). Identification of the events culminating in the transaction of the utrophin gene within synaptic myonuclei should provide important cues for the development of an effective therapeutic strategy for DMD.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bies.950190903
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  • 6
    Digitale Medien
    Digitale Medien
    How do insect herbivores cope with the extreme oxidative stress of phototoxic host plants? (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 29 (1995), S. 211-226 
    Details
    ISSN: 0739-4462
    Schlagwort(e): antioxidants ; phototoxins ; glutathione ; lipid peroxidation ; detoxification ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Plants of the Asteraceae and Hypericaceae possess secondary compounds that induce photooxidation in insect herbivores that consume them. One of the well-established modes of action of these substances is peroxidation of membrane lipids. Some herbivores counteract these defences by avoidance of light and tissues rich in phototoxins or the ability to detoxify these secondary substances. The cytochrome P-450 polysubstrate monooxygenase systems involved, the metabolic products, and a new putative toxin pump have been described. Dietary antioxidants (β-carotene, vitamin E, ascorbate) are additional defences against phototoxicity. They reduce mortality in herbivores exposed to phototoxins and some specialist herbivores have high constitutive levels. Adapted specialist insects also have higher constitutive levels of superoxide dismutase (SOD) and respond to phototoxins in their diet by the induction of catalase (CAT), glutathione reductase (GR), and increased levels of reduced glutathione (GSH). Artificial inhibition of the enzymes SOD and CAT had little effect on phototoxicity but inhibition of GSH synthesis in herbivores enhanced photooxidative effects of administered phototoxins on lipid peroxidation. While insects have many mechanisms to overcome plant photooxidants, the Asteraceae appear to have adopted a strategy of counterattack. We suggest and provide preliminary evidence that a second group of secondary substances, the sesquiterpene lactones, occurring in the Asteraceae can attack key antioxidant defences to synergise phototoxins. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/arch.940290210
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  • 7
    Digitale Medien
    Digitale Medien
    The effect of low sulfate concentrations on the glycosaminoglycan synthesis in anatomically intact articular cartilage of the mouse (1989)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 7 (1989), S. 645-653 
    Details
    ISSN: 0736-0266
    Schlagwort(e): Sulfate ; Cartilage ; Glycosaminoglycans ; Mouse ; Articular ; Life and Medical Sciences
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We have studied the effect of environmental sulfate concentration on the glycosaminoglycan synthesis of anatomically intact patellar cartilage of the mouse in vitro. Incubation of mouse patellae in medium with sulfate concentrations below 0.5 mM resulted in a diminished incorporation of sulfate but in unaltered incorporation of glucosamine. This suggested the synthesis of undersulfated glycosaminoglycans under these conditions. We characterized glycosaminoglycans synthesized at three different sulfate concentrations: a sulfate concentration physiological for the mouse (1.0 mM), a sulfate concentration in the range where sulfate incorporation was strongly diminished (0.1 mM), and an extremely low sulfate concentration (10 nM). Analysis of glycosaminoglycan disaccharides and DEAE anion chromatography of the glycosaminoglycans could not confirm the synthesis of undersulfated glycosaminoglycans at 0.1 mM. The chromatogram of glycosaminoglycans synthesized in medium containing 10 nM showed the presence of a very low sulfated glycosaminoglycan pool not observed at higher medium sulfate concentrations. Intermediately sulfated glycosaminoglycans were also synthesized during incubation with 10 nM sulfate. So, our data indicate that only very low sulfate concentrations in the medium lead to the synthesis of undersulfated glycosaminoglycans and that the sulfation mechanism of murine patellar cartilage chondrocytes does not seem to fit completely in an “all-or-nothing” pattern.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jor.1100070504
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  • 8
    Digitale Medien
    Digitale Medien
    Antioxidant enzymes as biochemical defenses against phototoxin-induced oxidative stress in three species of herbivorous lepidoptera (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 16 (1991), S. 139-152 
    Details
    ISSN: 0739-4462
    Schlagwort(e): superoxide dismutase ; catalase ; glutathione peroxidase ; glutathione reductase ; hypericin ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Many secondary plant compounds are capable of photoactivation resulting in the production of toxic species of oxygen. One mechanism of defense for insects feeding on phototoxic plants may be the presence of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPOX), and glutathione reductase (GR). The activities of these enzymes were examined in larvae of three lepidoptera: Ostrinia nubilalis, Manduca sexta, and Anaitis plagiata. Highest levels of antioxidant enzyme activity were found in A. plagiata, a specialist feeder on Hypericum perforatum, which contains high levels of the phototoxin hypericin. Larvae of A. plagiata fed leaf discs treated with hypericin exhibited a short-term, concentration-dependent decline in enzyme activity. Longer term studies with A. palgiata fed either the photoxic H. perforatum, or the closely related but non-phototoxic H. calycinum, resulted in increased CAT and GR activity in larvae fed the phototoxic plant whereas SOD activity was not significantly different. These results suggest that CAT and GR may be inducible defenses against phototoxins.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/arch.940160206
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