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  • Anaerobiosis  (2)
  • Development  (2)
  • Springer  (4)
  • National Academy of Sciences
  • Nature Publishing Group
  • Oxford University Press
  • 1995-1999  (4)
  • 1960-1964
  • 1950-1954
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  • Springer  (4)
  • National Academy of Sciences
  • Nature Publishing Group
  • Oxford University Press
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Year
  • 1
    ISSN: 1617-4623
    Keywords: Key words Gonococci ; Pilli ; Transcription ; Anaerobiosis ; Growth phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The type-4 pilus of Neisseria gonorrhoeae is a dominant surface antigen which facilitates adhesion to host target cells, an essential event in gonococcal infection. pilC2 encodes a 110-kDa protein involved in pilus assembly, pilus-mediated adherence to human epithelial cells in culture and natural competence for DNA transformation. Luciferase activity directed from a chromosomal pilC2::luxAB transcriptional fusion was reduced approximately 4-fold when cells were grown anaerobically. We observed a concomitant reduction in gonococcal piliation by electron microscopy and a reduction in the ability to adhere to ME-180 human epithelial cells when bacteria were grown in the absence of oxygen. Furthermore, we present evidence for growth-phase regulation of the gonococcal pilC2 gene in Escherichia coli, and show that all sequences necessary for growth-phase regulation are contained on a 121-bp pilC2 fragment. Expression from the minimal pilC2 fragment fused to lacZ in single-copy in E. coli was induced 2-fold when cells entered stationary phase. Surprisingly, induction does not require rpoS, the gene, which encodes the starvation-induced sigma factor RpoS. In summary, we have demonstrated that pilC2 is both positively and negatively regulated at the level of transcription. This regulation is most probably relevant to physiological conditions within the human host which influence gonococcal infections.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 256 (1997), S. 525-532 
    ISSN: 1617-4623
    Keywords: Key words Gonococci ; aniA ; Pan1 ; Nitrite reductase ; Anaerobiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aniA gene of Neisseria gonorrhoeae encodes an outer membrane lipoprotein which is strongly induced when gonococci are grown anaerobically in vitro in the presence of nitrite. Database searches with the amino acid sequence derived from the aniA structural gene revealed significant homologies to copper-containing nitrite reductases from several denitrifying bacteria. We constructed an insertional mutation in the aniA locus of strain MS11 by allelic replacement, to determine whether this locus was necessary for growth in oxygen-depleted environments, and to demonstrate that AniA was indeed a nitrite reductase. The mutant was severely impaired in its ability to grow microaerophilically in the presence of nitrite, and we observed a loss in viability over several hours of incubation. No measurable nitrite reductase activity was detected in the aniA mutant strain, and activity in the strain with a wild-type locus was inducible. Finally, we report investigations to determine whether AniA protein is involved in gonococcal pathogenesis.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 166 (1996), S. 319-324 
    ISSN: 1432-136X
    Keywords: Key words Compound eye ; Growth ; Development ; Age ; Crustacean ; Petrolisthes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Fifty randomly selected publications dealing with aspects of crustacean vision had their Materials and methods sections examined. In half of the articles gleaned, only the name of the animal under study was given; the other half mentioned “adult” or “mature” animals; twelve papers provided information on size or age of the experimental animal and six gave the sex. In Petrolisthes elongatus, rhabdom microvilli not only become more regular in outline as the animal grows, but also decrease in diameter from 90.4±21.2 nm in crabs of 5.0–8.9 mm carapace length via 86.6±13 nm in crabs of 9.0–12.9 mm carapace length to 79.7±7 nm in crabs of 13.0–16.9 mm carapace length. Approximately 400 cross sectional diameters of microvilli from identical regions in four eyes of each size class were measured and provided the basis for Anova-, Levene-, and t-tests. The three size classes possess microvilli of significantly different diameters and standard deviations. Our observations show that investigators of the crustacean photoreceptor have frequently neglected to consider the size of their experimental animals, but that this practice should not be continued as the now documented changes in microvillus diameters may influence the amount of visual pigment present and, thus, the photoreceptor’s sensitivity to light.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 166 (1996), S. 319-324 
    ISSN: 1432-136X
    Keywords: Compound eye ; Growth ; Development ; Age ; Crustacean ; Petrolisthes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Fifty randomly selected publications dealing with aspects of crustacean vision had theirMaterials and methods sections examined. In half of the articles gleaned, only the name of the animal under study was given; the other half mentioned “adult” or “mature” animals; twelve papers provided information on size or age of the experimental animal and six gave the sex. InPetrolisthes elongatus, rhabdom microvilli not only become more regular in outline as the animal grows, but also decrease in diameter from 90.4±21.2 nm in crabs of 5.0–8.9 mm carapace length via 86.6±13 nm in crabs of 9.0–12.9 mm carapace length to 79.7±7 nm in crabs of 13.0–16.9 mm carapace length. Approximately 400 cross sectional diameters of microvilli from identical regions in four eyes of each size class were measured and provided the basis for Anova-, Levene-, andt-tests. The three size classes possess microvilli of significantly different diameters and standard deviations. Our observations show that investigators of the crustacean photoreceptor have frequently neglected to consider the size of their experimental animals, but that this practice should not be continued as the now documented changes in microvillus diameters may influence the amount of visual pigment present and, thus, the photoreceptor's sensitivity to light.
    Type of Medium: Electronic Resource
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