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  • Mutation  (214)
  • Applied geophysics
  • Drosophila
  • American Association for the Advancement of Science (AAAS)  (198)
  • Springer  (188)
  • Elsevier  (3)
  • Institute of Physics
  • 1985-1989  (376)
  • 1970-1974  (13)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 3 (1988), S. 299-304 
    ISSN: 1476-5535
    Keywords: Anaerobe ; Antibiotic resistance ; Irradiation ; Mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Based on a dose-survival curve, a radiation dose of 3.99 C/kg was used to induce antibiotic-resistant mutants inBacteroides fragilis. Escherichia coli B/r membrane fragments were employed as a reducing agent. Antibiotic-resistant mutants ofB. fragilis were utilized to study the mechanism by which these organisms become resistant to selected chemotherapeutic agents. Decreased accumulation of tetracycline by resistant mutants ofB. fragilis suggests that the resistance to this antibiotic is associated with the outer membrane permeability. There is a marked difference in the inhibitory action of rifampicin on RNA polymerase activity in rifampicin-sensitive and-resistant strains ofB. fragilis. This enzyme is, therefore, the likely target for inhibition of bacterial growth in this anaerobe by rifampicin.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of insect behavior 1 (1988), S. 3-15 
    ISSN: 1572-8889
    Keywords: host preference ; habitat selection ; experience ; learning ; Drosophila ; host races ; population genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A field experiment with Drosophila melanogasterrevealed that when flies encounter a particular food type soon after emergence, the probability of their subsequently being attracted to such a resource is increased. In this experiment, the length of time flies experienced their postemergence environments was under the control of the flies themselves. The experiment thus realistically mimicked one form of experiential effect that may be important in nature. A theoretical model is developed which shows that enhanced adult preferences for the types of resources fed on as larvae can substantially increase the degree of host-based genetic subdivision within a polyphagous population.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 39 (1985), S. 143-147 
    ISSN: 1570-7458
    Keywords: Hymenoptera ; Drosophila ; parasitoid ; habitat toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé L'étude a porté sur la tolérance et l'utilisation de vapeurs d'éthanol, d'acide acétique et d'acétaldéhyde par Asobara persimilis (Hym. Braconidae), parasitoïde de Drosophila récemment découvert en Australie. Aux faibles concentrations, il n'y a pas d'utilisation significative d'éthanol et d'acide (respectivement moins de 1,5% et 0,1%), cependant la longévité des mâles et des femelles ont augmenté avec les concentrations d'acide acétique de 1,0 et 1,5%. Toutes ces substances sont toxiques à plus forte concentrations, bien qu'il y ait un dimorphisme sexuel et que les femelles survivent significativement plus longtemps que les mâles. La tolérance des braconides est inférieure à celle de leurs hôtes, les Drosophiles cosmopolites et endémiques à l'Australie. Ceci peut faire que ces parasites limitent l'exploitation de leurs hôtes aux habitats avec une faible concentration de produits de fermentation.
    Notes: Abstract The tolerance and utilization of ethanol, acetic acid and acetaldehyde vapour was investigated in Asobara persimilis (Hymenoptera: Braconidae), a parasitoid of Drosophila. No significant utilization of ethanol or acetaldehyde occurred at low concentrations (〈 1.5% and 0.1% respectively), however both female and male longevity was increased at concentrations of 1.0 and 1.5% acetic acid. All substances were toxic at higher concentrations, but there was sexual dimorphism in that females survived significantly longer than males.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 43 (1987), S. 193-201 
    ISSN: 1570-7458
    Keywords: Leptopilina boulardi ; Cynipidae ; Hymenoptera ; parasitoid ; Drosophila ; Diptera ; field egg laying strategy ; functional response ; switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Le concept de réponse optimale d'un parasite vis-à-vis de l'hôte le plus favorable pour son développement demeure surtout théorique et n'a pu être vérifié que dans les conditions de laboratoire. Nous avons montré que Drosophila melanogaster s'avère être, par rapport à D. simulans, l'hôte le plus favorable pour le développement du cynipide parasite Leptopilina boulardi. Une étude sur le terrain a démontré que ce parasite présente une réponse fonctionnelle densité dépendante vis-à-vis de D. melanogaster et non vis-à-vis de D. simulans, avec un effet de bascule. D'autre part, il s'avère que ce parasite exploite beaucoup mieux son hôte, en évitant le superparasitisme, ceci étant démontré au laboratoire et dans la nature. Enfin, il apparaît qu'il est capable d'allonger sa période de ponte lorsque cet hôte est rare, ce qui ne se produit pas avec D. simulans.
    Notes: Abstract The hypothesis of optimal host species selection predicts that when a parasitoid has the choice between two host species, it will choose the species thay gives the best survival chances for its progeny. We confirmed this hypothesis by laboratory experiments with Leptopilina boulardi Barb. et al., a cynipid parasitoid which prefers Drosophila melanogaster Meigen (the host species most suitable for parasitoid survival) above D. simulans Sturt. As far as fitness parameters are concerned, the fertility of L. boulardi is higher with D. melanogaster; the egg laying can be spread out over a long period when this host is relatively scarce. This does not occur with D. simulans in which parasitic oviposition stops soon when this host is not abundant. Investigations of this foraging strategy were done under more complex natural conditions. We found that L. boulardi has a type III functional response with D. melanogaster only; furthermore, it seems that a switching effect may exist with this host. Parasitoid females appear to distribute their eggs more regularly on D. melanogaster, thus avoiding superparasitism. This seems to be independent of the relative frequency of this host. However, superparasitism of D. simulans did occur more frequently when this host was scarce.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 47 (1988), S. 81-88 
    ISSN: 1570-7458
    Keywords: imaginal diapause ; male mating activity ; genetics ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Les femelles de D. triauraria Bock & Wheeler (Dipt. Drosophilidae) sont connues pour présenter une diapause reproductrice aux photophases courtes. Les mâles eux aussi ont révélé une activité sexuelle réduite aux photophases courtes, c'est-à-dire qu'ils sont entrés comme les femelles en diapause reproductive. Les photophases critiques pour l'induction de la diapause des mâles et des femelles n'ont pas présenté de différences. Les diapause des mâles et des femelles s'achèvent même sous courtes photophases, mais la diapause mâle était quelque peu plus faible que la diapause femelle. La photophase critique et le taux de diapause ont varié en fonction de l'origine géographique dans l'espèce actuelle. Lors de croisements entre lignées diapausantes et non-diapausantes, la photophase critique et la durée de la diapause ont été héritées quantitativement. A partir de ces expériences et d'expériences précédentes de croisements (Kimura, 1983), quelques modèles de méchnisme d'induction de la diapause de cette espèce sont proposés.
    Notes: Abstract In Drosophila triauraria Bock & Wheeler (Diptera: Drosophilidae) of which females were known to enter reproductive diapause at short daylengths, males also showed reduced mating activity at short daylengths, i.e., males as well as females entered reproductive diapause. The critical daylength for diapause induction did not differ between females and males. Both male and female diapause ended even under short daylengths, but the male diapause was somewhat weaker than the female diapause. The critical daylength and the diapause rate varied geographically in this species. In the cross between diapausing and non-diapausing strains, the critical daylength and the diapause duration inherited in a quantitative manner. On the basis of the present and previous crossing experiments, some models are proposed on the mechanism of diapause induction of this species.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 4 (1989), S. 19-27 
    ISSN: 1476-5535
    Keywords: Zymomonas mobilis ; Growth on lactose ; Cloning ; Mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Wild-type strains ofZymomonas mobilis have a limited substrate range of glucose, fructose and sucrose. In order to expand this substrate range, transconjugants ofZ. mobilis containing Lac+ plasmids have been constructed. Although β-galactosidase is expressed in such strains, they lack the ability to grow on lactose. We now report the development ofZ. mobilis strains capable of growth on lactose. This was achieved in two stages. First, a broad host range plasmid was constructed (pRUT102) which contained the lactose operon under the control of aZ. mobilis promoter plus genes for galactose utilization.Z. mobilis CP4.45 containing pRUT102 was then subjected to mutagenesis combined with continued selection pressure for growth on lactose. One strain,Z. mobilis SB6, produced a turbid culture that yielded 0.25% ethanol from 5% lactose (plus 2% yeast extract) in 15 days.
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  • 7
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein gene ; Transcription activation ; Mutation ; Methylation interference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Most ribosomal protein (rp-)genes in yeast are preceded by conserved sequence motifs that act as upstream transcription-activating sites (RPG box). These sequence elements have previously been shown to represent specific binding sites for a protein factor, TUF. Comparison of the various nucleotide elements identified so far indicates a remarkably high degree of variation in the respective sequences. On the other hand, a methylation interference study performed with one RPG box revealed close contact points with the TUF protein along the entire sequence. To investigate the sequence requirements of the RPG box, we inserted synthetic oligonucleotides that differed from the general consensus sequence ACACCCATACATTT at single positions into a deletion mutant of the L25 promoter that lacked its natural RPG elements. Transcription activity was estimated by Northern analyses of the cellular level of L25-galK hybrid transcripts. The results show that in the 3′ part of this sequence element single substitutions are allowed at all positions, in the 5′ part, however, the nucleotide requirements appear to be more stringent. In particular, the invariant C at position 5 of the consensus sequence is absolutely necessary for its enhancer function.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 28 (1988), S. 145-150 
    ISSN: 1432-1432
    Keywords: Alcohol dehydrogenase ; Drosophila ; Enzyme kinetics ; Product inhibition ; Microevolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Because natural populations ofDrosophila melanogaster are polymorphic for different allozymes of alcohol dehydrogenase (ADH) and becauseD. melanogaster is more tolerant to the toxic effects of ethanol than its sibling speciesD. simulans, information regarding the sensitivities of the different forms of ADH to the products of ethanol degradation are of ecological importance. ADH-F, ADH-S, ADH-71k ofD. melanogaster and the ADH ofD. simulans were inhibited by NADH, but the inhibition was relieved by NAD+. The order of sensitivity of NADH was ADH-F〈ADH-71k, ADH-S〈ADH-simulans with ADH-F being about four times less sensitive than theD. melanogaster enzymes and 12 times less sensitive than theD. simulans enzyme. Acetaldehyde inhibited the ethanolto-acetaldehyde activity of the ADHs, but at low acetaldehyde concentrations ethanol and NAD+ reduced the inhibition. ADH-71k and ADH-F were more subject to the inhibitory action of acetaldehyde than ADH-S and ADH-simulans, with ADH-71k being seven times more sensitive than ADH-S. The pattern of product inhibition of ADH-71k suggests a rapid equilibrium random mechanism for ethanol oxidation. Thus, although the ADH variants only differ by a few amino acids, these differences exert a far larger impact on their intrinsic properties than previously thought. How differences in product inhibition may be of significance in the evolution of the ADHs is discussed.
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  • 9
    ISSN: 1432-1432
    Keywords: Drosophila ; Foldback element ; Transposable element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Foldback elements are a family of transposable elements described inDrosophila melanogaster. The members of this dispersed repetitive family have terminal inverted repeats that sometimes flank a central region. The inverted repeats of all the family members are homologous. The study of the distribution and conservation of the foldback elements in differentDrosophila species shows that this distribution is different from that of the hybrid dysgenesis systems (PM and IR). Sequences homologous to foldback elements were observed by Southern blots and in situ hybridization in all species of themelanogaster subgroup and in some species of themontium andtakahashii subgroups. The element was probably already present before the radiation of these subgroups. No evidence of horizontal transmission of the foldback element could be observed.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 1 (1972), S. 258-262 
    ISSN: 1432-1432
    Keywords: Calcitonin ; Evolution ; Genetic Code ; Mutation ; Amino Acid Sequences ; Base Changes ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The amino acid replacements in the calcitonins from five different species (human, bovine, ovine, porcine and salmon) have been analyzed according to the genetic code. More mutations separate the presumed common mammal from the artiodactyls than from either salmon or man.
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