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  • Articles  (5)
  • Drosophila
  • Ultrastructure
  • stability
  • Springer  (5)
  • Process Engineering, Biotechnology, Nutrition Technology  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Recombinant protein expression in aDrosophila cell line: comparison with the baculovirus system (1994)
    Springer
    Cytotechnology 15 (1994), S. 139-144 
    Details
    ISSN: 1573-0778
    Keywords: Baculovirus ; cell culture ; Drosophila ; gene expression ; insect cell ; metallothionein promoter ; recombinant protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In this report, we compare two different expression systems: baculovirus/Sf9 and stable recombinantDrosophila Schneider 2 (S2) cell lines. The construction of a recombinant S2 cell line is simple and quick, and in batch fermentations the cells have a doubling time of 20 hours until reaching a plateau density of 20 million cells/ml. Protein expression is driven by theDrosophila Metallothionein promoter which is tightly regulated. When expressed in S2 cells, the extracellular domain of human VCAM, an adhesion molecule, is indistinguishable from the same protein produced by baculovirus-infected Sf9 cells. Additionally, we present data on the expression of a seven trans-membrane protein, the dopamine D4 receptor, which has been successfully expressed in both systems. The receptor integrates correctly in the S2 membrane, binds [3H]spiperone with high affinity and exhibits pharmacological characteristics identical to that of the receptor expressed in Sf9 and mammalian cells. The general implications for large scale production of recombinant proteins are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00762388
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  • 2
    Electronic Resource
    Electronic Resource
    Yeast communities associated withDrosophila species and related flies in an eastern oak-pine forest: A comparison with western communities (1995)
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 484-494 
    Details
    ISSN: 1476-5535
    Keywords: Yeasts ; Drosophila ; Community ecology ; Cacti ; Tree-fluxes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Intestinal yeast mycobiota were studied in 14 species ofDrosophila and in the drosophilid speciesChymomyza amoena, captured at Pinery Provincial Park, Ontario. Over 56 yeast species, some undescribed, were isolated. These yeast communities were compared with those from two similar surveys conducted in western portions of North America. The community structures were influenced significantly by the habitat rather than phylogeny of the flies. Geographic separation was a factor affecting yeast taxa frequencies in the fly species, but it was largely overshadowed by ecological factors when the communities were described physiologically. The notion that habitats are filled by yeasts which add up to a suitable physiological potential, more or less independently of their taxonomic affinities, was thus confirmed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01573963
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  • 3
    Electronic Resource
    Electronic Resource
    Activity and thermostability of carboxymethylcellulase from Aspergillus niger is strongly influenced by noncovalently attached polysaccharides (1996)
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 213-216 
    Details
    ISSN: 1573-0972
    Keywords: Activity ; Aspergillus niger ; CMCase ; polysaccharides ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Removal of non-covalently attached polysaccharides from carboxymethylcellulase (CMCase) of Aspergillus niger improved its activity but decreased its thermostability and protease resistance. The activation energy profile of the hydrolysis of carboxymethylcellulose (CMC) was triphasic with increasing values of 17,-55 and-562 kJ/mol for polysaccharide-free and 19, -21 and -207 kJ/mol for polysaccharide-complexed CMCase. The specificity constant (Vmax/Km) of polysaccharide-free CMCase was 1.41 compared to polysaccharide-complexed CMCase which was only 0.68. The polysaccharide free CMCase had lower thermostability (‘melting point’ = 82°C) and higher protease susceptibility compared to polysaccharide-complexed CMCase (‘melting point’〉100°C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00360917
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  • 4
    Electronic Resource
    Electronic Resource
    The gel microdrop secretion assay: Identification of a low productivity subpopulation arising during the production of human antibody in CHO cells (2000)
    Springer
    Cytotechnology 34 (2000), S. 27-37 
    Details
    ISSN: 1573-0778
    Keywords: CHO cells ; gel microdrops ; human antibody ; population parameters ; productivity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The long-term stability of high-level expression is the mostimportant factor to consider when choosing cell lines for the expression of recombinant proteins. Declining volumetricyields in large-scale fermentation can be caused by changes affecting the cell population as a whole such as loss in viability, depletion of nutrients or accumulation of metabolites affecting cell growth. Alternatively, geneticinstability may lead to the outgrowth of a less productive,metabolically favored sub-population. Currently a variety ofparameters are measured to monitor the condition of cells infermenters including glucose uptake, lactate accumulation andoxygen consumption; in addition, periodic viable cell countsallow the determination of the growth rate and viability of the population. All of these methods measure the condition ofthe cell population as a whole and changes must involve a significantly large proportion of the total culture in orderto be detectable. Here we report on a method that allows theevaluation of the productivity of individual cells. Using the gel microdrop secretion assay, we detected the appearance ofa sub-population of cells with lower productivity. Subsequentanalysis of the culture confirmed the existence of lower productivity cells with a lower vector copy number. Therefore,the single cell secretion assay proved to be a rapid method todetect and isolate a low productivity variant of the producer cell line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008186113245
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  • 5
    Electronic Resource
    Electronic Resource
    Stable, recombinant expression of human insulin-like growth factor binding protein-1 (hIGFBP-1) in Chinese hamster ovary (CHO) cells (1997)
    Springer
    Cytotechnology 24 (1997), S. 193-200 
    Details
    ISSN: 1573-0778
    Keywords: CHO cells ; DHFR ; IGFBP-1 ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Stable expression of human insulin-like growth factor of binding protein-1 (hIGFBP-1)at high levels has been achieved in Chinese hamster ovary (CHO) cells by co-transfection and subsequent co-amplification of expression vectors containing the hIGFBP-1 cDNA and a dihydrofolate reductase (DHFR) cDNA gene into DHFR-deficient cells. Stepwise selection of the DHFR+ transformants in increasing concentrations of methotrexate (MTX) generated cells which had high copy numbers of the hIGFBP-1 gene (around 100 copies in cells amplified in medium containing 100 nM MTX). Expression of hIGFBP-1 in mixed clones was found to increase with increasing copy number and an apparent correlation between intra- and extracellular levels of hIGFBP-1 produced by these cells was observed. It was further observed that continuous cultivation over eight months in medium supplemented with 100 nM MTX increased the production of hIGFBP-1 25 times. The productivity did not increase further after five more months cultivation in MTX containing medium. A subcloning of this cell line gave clones with an even higher productivity. Further amplification in 500 nM or 1 uM MTX did not increase the hIGFBP-1 production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007999512662
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