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  • Electronic Resource  (5)
  • oral bacteria  (3)
  • Electroporation  (2)
  • 1
    Electronic Resource
    Electronic Resource
    PEG- and electroporation-induced transformation in Nicotiana tabacum: influence of genotype on transformation frequencies (1989)
    Springer
    Theoretical and applied genetics 78 (1989), S. 287-292 
    Details
    ISSN: 1432-2242
    Keywords: Direct gene transfer ; Electroporation ; Genotype influence ; Kanamycin resistance ; Nicotiana tabacum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Experimental parameters for direct gene transfer with recombinant DNA encoding neomycin phosphotransferase II (NPTII) under control of eukaryotic expression signals were established. The introduced gene was shown by the growth of transformants on media containing kanamycin, by genomic blotting and by assaying NPTII activity. Leaf protoplasts from three green genotypes of varieties xanthii and petit havanna, and from four plastome-encoded albino genotypes of Nicotiana tabacum were analyzed with respect to cell division kinetics and yield of kanamycin-tolerant colonies after direct gene transfer. No clear correlation was found between the time of onset of cell division and transformation frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288813
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Lipofectin: direct gene transfer to higher plants using cationic liposomes (1991)
    Springer
    Theoretical and applied genetics 83 (1991), S. 1-5 
    Details
    ISSN: 1432-2242
    Keywords: Cationic liposomes ; Direct gene transfer ; Electroporation ; Plant transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It has recently been shown that lipofectin, a commercially available preparation of cationic liposomes is capable of animal and plant cell line transfection. Here, it is analyzed with respect to its toxicity for higher plant protoplasts and used for transient expression and stable transformation experiments with mesophyll protoplasts of Nicotiana tabacum and Nicotiana plumbaginifolia. Transient expression of the β-glucuronidase gene (GUS) under control of the CaMV-35S-promoter was lower than after introduction of the same gene by polyethylene glycol. By transferring the neomycin phosphotransferase gene (NPTII) and subsequent culture and regeneration under selection with kanamycin, stably transformed plants were recovered after using Lipofectin in various protocols with or without additional application of electroporation. Efficiencies of stable transformation were comparable to those achieved with PEG and/or electroporation. Confirmation of transformants included assaying the enzyme activity of the gene product, genomic blotting, and transfer of the resistant phenotype to the progeny produced from selfed primary transformants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229218
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  • 3
    Electronic Resource
    Electronic Resource
    Aggregation of oral bacteria by human salivary mucins in comparison to salivary and gastric mucins of animal origin (1990)
    Springer
    Antonie van Leeuwenhoek 58 (1990), S. 255-263 
    Details
    ISSN: 1572-9699
    Keywords: aggregation ; animal mucins ; human salivary mucin ; oral bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seventeen strains of oral bacteria of the genera Actinomyces (5), Bacteroides (3), and Streptococcus (9) were tested for aggregation by the human whole salivary mucin fraction (HWSM) in comparison to three types of animal mucin preparations from submandibular glands of cow (BSM) and sheep (OSM), and from the stomach of pig (PGM). Considerable variation was seen with respect to the rate and titer of aggregation induced by these mucins. The aggregating activity of HWSM varied widely among the different bacterial strains. The Bacteroides group showed hardly any induced aggregation, whereas the final aggregation titers varied for S. sanguis (3 strains) between 12 and 48, for S. oralis (3 strains) between 6 and 48, for the S. mutans group (3 strains) between 6 and 96, and for the five Actinomyces strains even between 6 and 192. For a particular strain, similar differences in titer were seen between the four mucins. For a human salivary mucin (MG-2) it has been described that sialic acid in the sequence NeuAc (α2,3)Gal(β1,3)GalNac- was specifically involved in the interaction with S. sanguis strains, in contrast to S. rattus BHT. Our results, however, indicate that this sugar sequence is not a prerequisite for the aggregation of S. sanguis, as animal mucins, devoid of this structure, were equally well or even better capable of inducing aggregation. On the other hand, desialization of BSM and OSM largely abolished their aggregating capability towards S. rattus BHT. Moreover, it was found that BSM and OSM, which are comparable with respect to their major oligosaccharide structure, show considerable differences in aggregating activity towards the same bacterial strain. The results indicate that the interaction and aggregation of oral bacteria with mucins is not necessarily dictated by specific oligosaccharide structures of the mucins, but may be caused instead by common physico-chemical features of the mucins as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399337
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of different assays for the aggregation of oral bacteria by human whole saliva (1989)
    Springer
    Antonie van Leeuwenhoek 55 (1989), S. 109-122 
    Details
    ISSN: 1572-9699
    Keywords: aggregation ; microtiterplate assay ; oral bacteria ; phase-contrast microscopy ; saliva ; spectrophotometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract For comparison, human whole saliva-induced aggregation was studied by phase-contrast microscopy, spectrophotometry combined with macroscopic observations, and in microtiterplate assay under identical experimental conditions for Actinomyces viscosus HG 85 (T14-V) and HG 380 (T14-AV), Bacteroides gingivalis HG 66 (W 83), Streptococcus rattus HG 59 (BHT), and Streptococcus sanguis I HG 169. The entire process of formation, extension, and sedimentation of aggregates could merely be observed by the combination of these assays. The very first stages of aggregation could only be detected and quantitated by phase-contrast microscopy. Within 2 1/2 min. 50% of the A. viscosus, S. rattus, and S. sanguis cells were aggregated, denoted as T50. In microtiterplates, however, aggregates were observed in general only after sedimentation at 30–45 min of incubation, expressed as TA. For interpretation of the spectrophotometric curves, additional microscopic and macroscopic data were a prerequisite. The small decline in absorbance during the first 30–45 min (phase 1) corresponded to the formation and extension of non-sedimenting aggregates, whereas the subsequent pronounced fall in absorbance (phase 2) was caused by the massive sedimentation of aggregates. The moment of inflexion between both phases, TI, marked the onset of sedimentation of aggregates and corresponded very well with TA, at which time already 92–98% of the cells were aggregated as quantitated by microscopy. In conclusion, only by microscopy the formation and extension of aggregates could be observed within a few minutes and quantitated in terms of aggregation rate. From 30–45 min, merely the sedimentation of aggregates was visualized in microtiterplates, whereas the time course of the overall process was recorded indirectly by spectrophotometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404751
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Aggregation of 27 oral bacteria by human whole saliva (1989)
    Springer
    Antonie van Leeuwenhoek 55 (1989), S. 277-290 
    Details
    ISSN: 1572-9699
    Keywords: Actinomyces ; aggregation ; Bacteroides ; oral bacteria ; saliva ; Streptococcus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Twenty-seven oral strains of the genera Actinomyces (5), Bacteroides (3), and Streptococcus (19) were tested for aggregation by human whole saliva, as well as the effect of culture medium, Ca-ions, and bacteria concentration thereupon. Of the media tested, GF-broth gave rise to less interference by autoaggregation or higher aggregation titers than BHI and TSB, and was used throughout this study. In most cases, Ca-ions (1 mM) only enhanced the rate of induced aggregation, whereas raising the bacteria concentration increased the rate of both induce- and autoaggregation. The final titers, ranging from 1–64, were hardly affected by these parameters, except those of S. rattus HG 59 and S. mutans HG 199, which were respectively increased and decreased by Ca-ions. Saliva-induced aggregation was observed for 21 strains of A. viscosus, A. naeslundii, A. israelii, B. gingivalis, B. intermedius, S. cricetus, S. mutans, S. rattus, S. sanguis, and S. sobrinus, mostly within 15 min to 3 h. Seventeen of these strains also showed autoaggregation, usually well after the onset of induced aggregation. Any potential induced aggregation of B. gingivalis HG 91 was always masked by autoaggregation, as well as that of the S. mutans strains under a particular set of conditions. The aggregation rate and titer varied considerably in a mutually unrelated and strain-dependent way. These microtiterplate data were matched by the 5 spectrophotometric patterns observed for saliva-bacterial interaction, which moreover, gave the better differentiation between induced and autoaggregation. In conclusion, most strains tested can show rapid saliva-induced aggregation in a strain-dependent way, yet strongly affected by the experimental conditions and interference from autoaggregation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393856
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