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  • 1
    Electronic Resource
    Electronic Resource
    Expansion of Human Bone Marrow Progenitor Cells in a High Cell Density Continuous Perfusion System (1993)
    [s.l.] : Nature Publishing Company
    Nature biotechnology 11 (1993), S. 368-372 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We describe here a continuous perfusion bioreactor system that enables a population of unselected human mononuclear bone marrow cells obtained from adult donors to expand up to 20 to 25-fold over a two-week period. Colony-forming units of granulocyte-macrophage (CFU-GM) progenitor cells expand 10 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt0393-368
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of pyridine on the fatty acid composition of Pimelobacter sp. (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 141 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The fatty acid composition of Pimelobacter sp. is of the complex type. When pyridine was used as a sole inhibitory substrate, the fatty acid composition of Pimelobacter sp. was quite different from that within other readily available substrates. When compared with the fatty acid composition in a complex medium, the proportion of isopalmitic acid (iso-C16:0) drastically decreased from 68.4% to 7.7%, while the proportion of anteisoheptadecanoic acid (anteiso-C17:0) remained almost constant at ca. 7%. Concomitantly, this decrease of the branched-chain fatty acid was accompanied by the increase of the straight-chain, especially long-chain, fatty acid such as heptadecanoic (C17:0), octadecenoic (Cig:i), 10-methylheptadecanoic (10-me-18) and 10-methyloctadecanoic (10-me-19) acids. Consequently, in response to membrane active organic solvents, Pimelobacter sp. was found to regulate its membrane fatty acid composition in a fashion different from Gram-negative bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08375.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of serum type and concentration on the expression ofβ-galactosidase in recombinant vaccinia virus infected HeLa S3 cells (1995)
    Springer
    Cytotechnology 19 (1995), S. 153-159 
    Details
    ISSN: 1573-0778
    Keywords: vaccinia virus ; HeLa S3 cells ; β-galactosidase ; calf and horse serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of serum type and concentration on recombinant protein expression in vaccinia virus infected HeLa S3 cells was studied in both static and suspension culture. A model heterologous protein,β-galactosidase (β-gal), was used. Calf and horse sera in the range of 0.5–10%(v/v) were investigated. In static culture, the calf serum concentration did not show any significant influence on the β-gal production which was almost completed within 24h postinfection (pi). Higher horse serum concentration, on the other hand, resulted in higher β-gal concentration which continued to increase until 48 h pi. Total β-gal concentrations in 0.5% calf serum at 24 h pi and 10% horse serum at 48 h pi were 2.2±0.7 and 2.2±0.1 IU/ml, respectively. In suspension culture, both sera showed their respective effects on the β-gal production similar to those observed in static culture, indicating that the cultivation method had little influence on β-gal production. Accordingly, the use of 0.5% calf serum after virus infection in recommended for economical β-gal production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749770
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced specific antibody productivity of calcium alginate-entrapped hybridoma is cell line-specific (1994)
    Springer
    Cytotechnology 16 (1994), S. 1-15 
    Details
    ISSN: 1573-0778
    Keywords: Flow cytometry ; hybridoma ; immobilization ; specific antibody productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In order to determine whether the enhanced specific antibody productivity (q MAb ) of calcium alginate-entrapped hybridoma is cell line-specific, calcium alginate-entrapped hybridomas (4A2 and DB9G8) were cultivated under the condition where we had previously observed significantly enhancedq MAb of calcium alginate-entrapped S3H5/γ2bA2 hybridoma. Unlike S3H5/γ2bA2 hybridoma, neither 4A2 nor DB9G8 hybridomas showed persistently enhancedq MAb when they were entrapped in calcium alginate beads. The enhancedq MAb of entrapped 4A2 and DB9G8 hybridomas, which was 2–3 times higher than theq MAb of free-suspended cells in a control experiment, was observed only during the early stage of the culture. During the early stage of the culture, the viable cell concentration decreased probably due to cell damage during the entrapment process. As cell growth resumed, theq MAb decreased to the similar level ofq MAb of free-suspended cells within 5–7 days. Thus, we conclude that the enhancedq MAb of calcium alginate-entrapped hybridomas is cell line-specific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00761774
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  • 5
    Electronic Resource
    Electronic Resource
    High cell density perfusion cultures of anchorage-dependent Vero cells in a depth filter perfusion system (1995)
    Springer
    Cytotechnology 17 (1995), S. 173-183 
    Details
    ISSN: 1573-0778
    Keywords: depth filter perfusion system ; Vero cell culture ; gelatin coating ; polypropylene fiber ; air sparging ; high cell density culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A depth filter perfusion system (DFPS) with polypropylene fibers had been demonstrated to support high density cultures of anchorage-independent hybridoma cells. The DFPS provides advantages of high surface-to-volume ratio of 450–600 cm2/cm3, low cost set-up, easy operation and scale-up. To test the feasibility of using DFPS for high density cultures of anchorage-dependent cells, Vero cells were cultivated in the DFPS. Gelatin coating on polypropylene fibers in the DFPS was necessary to promote cell attachment and growth. Dissolved oxygen (DO) concentrations could be controlled by sparging air into the reservoir vessel through a filter sparger. When DO concentration was controlled above 40% of air saturation in the DFPS with 40 μm pore size, the maximum cell concentration as estimated on specific lactate production rate, was 3.81×107 cells/ml of the total reactor volume. This viable cell concentration is approximately 18 times higher than that obtained in a T-flask batch culture. Taken together, the results obtained here showed the potential of DFPS for high-density cultures of anchorage-dependent cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749655
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  • 6
    Electronic Resource
    Electronic Resource
    Justification of continuous packed-bed reactor for retroviral vector production from amphotropic ΨCRIP murine producer cell (2000)
    Springer
    Cytotechnology 34 (2000), S. 151-158 
    Details
    ISSN: 1573-0778
    Keywords: anchorage-dependent cell ; cell culture ; packed-bedreactor ; retroviral vector ; viral production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract To indentify a plausible large-scale production system forretroviral vector, three culture systems, i.e., batch culturewith medium exchange, microcarrier culture, and packed-bedreactor culture were compared. In batch cultures with mediumexchange, high cell concentrations were maintained for about amonth, and the harvested retroviral titer remained constant. Inmicrocarrier cultures, although cell growth was rapid, theretroviral titer was unexpectedly low, suggesting that the lowtiter was due either to serious damage to the retroviral vectoror to a reduction in the production rate of retroviral vector,caused by mechanical shear forces. Although the retroviral titer(maximum titer, 1.56 × 106) in the packed-bedreactor was a little bit lower than that obtained in the batchculture with medium exchange (maximum titer, 1.91 ×106), continuous production made it possible to increasethe cumulative titer up to 16-fold of that from the batchculture with medium exchange. Moreover, as the packed-bedreactor system requires less labor and shows excellentvolumetric productivity in comparison to batch cultures withmedium exchanges, it will be an appropriate production systemfor retroviral vector in large quantities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008120313175
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  • 7
    Electronic Resource
    Electronic Resource
    Immobilization can improve the stability of hybridoma antibody productivity in serum-free media (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1049-1055 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hybridoma cells (S3H5/γ2bA2) were cultivated in spinner flasks with 1% serum media and serum-free media. Monoclonal antibody productivity was maintained in 1% serum media. However, cells in serum-free media showed a decrease in antibody productivity, and it completely disappeared in IMDM-based low protein medium. This loss of antibody productivity was not observed when the cells were immobilized in alginate beads. In fact, immobilization enhanced the specific MAb productivity.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260361010
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  • 8
    Electronic Resource
    Electronic Resource
    Cell Culture conditions determine the enhancement of specific monoclonal antibody productivity of calcium alginate-entrapped S3H5/γ2bA2 hybridoma cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 330-340 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; Immobilization ; monoclonal antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Immobilization offers several intrinsic advantages over free suspension cultures for the production of monoclonal antibodies. An important advantage of immobilization is the improved specific monoclonal antibody (MAb) productivity (qMAb) that can be obtained. However, there are conflicting reports in the literature on the enhancement of the qMAb with immobilization. The discrepancies between these reports can be attributed to the different to either the cultivation methods used for immobilized cell or to difference between the cell lines used in the various studies. We show that these differences may be attributed to the different cultivation methods used for one model hybridoma cell line. S3H5/ϒ2bA2 hybridoma cells entrapped in different sizes of calcium alginate beads were cultivated in both T- and spinner flasks in order to determine whether cultivation methods (T- and spinner flasks) and bead size influence the qMAb Free-suspended cell cultures inoculated with cells recovered from alginate beads were also carried out in order to determine whether changes in the qMab of the entrapped cells are reversible.The cultivation methods was found to influence significantly the qMAb of the entrapped cells. When the entrapped cells in 1-mn diameter beads were cultivated in T-flasks, the qMAb was not increased by 200% as previously observed in an entrapped cell culture using 1-mm-diameter alginate beads in spinner flasks. The qMAb of the entrapped cell was approximately 58% higher than that of the free-suspended cells in a control experiment. Unlike the cultivation method, the bead size in the range of 1- to 3-mm diameter did not significantly influence the qMAb, regardless of cultivations methods. The changes in qMAb of an entrapped cells were reversible. When the free-suspended cells recovered from the T- and spinner flasks were sub-cultured in T- and spinner flasks enhanced qMAb of the entrapped cells in both cases decreased to the level of the free-suspended cell in a control experiments. Taken together, these results shows that the method of cultivation of hybridoma cells immobilized in alginate beads determines the extent of enhancement of the qMAb. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410307
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  • 9
    Electronic Resource
    Electronic Resource
    Microencapsulated human bone marrow cultures: A potential culture system for the clonal outgrowth of hematopoietic progenitor cells (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 734-739 
    Details
    ISSN: 0006-3592
    Keywords: bone marrrow cultures ; hematopoietic progenitor cells ; microencapsulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Currently the most successful methods for culturing human hematopoietic cells employ some form of perfused bioreactor system. However, these systems do not permit the clonal outgrowth of single progenitor cells. Therefore, we have investigated the use of alginate-poly-L-lysine microencapsulation of human bone marrow, combined with rapid medium exchange, as a system that may overcome this limitation for the purpose of studying the kinetics of progenitor cell growth. We report that a 12 to 24-fold multilineage expansion of adult human bone marow cells was achieved in about 16 to 19 days with this system and that visually identifiable colonies within the capsules were responsible for the increase in cell number. The colonies that represented the majority of cell growth originated from cells that appeared to be present in a frequency of about 1 in 4000 in the encapsulated cell population. These colonies were predominantly granulocytic and contained greater than 40,000 cells each. Large erythroid colonies were also present in the capsules, and they often contained over 10,000 cells each. Time profiles of the erythroid progenitor cell density over time were obtained. Burst-forming units erythroid (BFU-E) peaked around day 5, and the number of morphologically identifiable erythroid cells (erythroblasts through reticulocytes) peaked on day 12. We also report the existence of a critical inoculum density and how growth was improved with the use of conditioned medium derived from a microcapsule culture initiated above the critical inoculum density. Taken together, these results suggest that microencapsulation of human hematopoietic cells allows for outgrowth of progenitor, and possible preprogenitor, cells and could serve as a novel culture system for monitoring the growth and differentiation kinetics of these cells.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430807
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  • 10
    Electronic Resource
    Electronic Resource
    Stability of antibody productivity is improved when hybridoma cells are entrapped in calcium alginate beads (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1131-1135 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; instability ; immobilization ; monoclonal antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Loss of monoclonal antibody (MAb) productivity in long-term, free-suspended cell culture is often attributed to the appearance of a nonproducing population of hybridoma cell (NP) in the culture which has a growth advantage over the producing population (P). However, when an NP appears in long-term culture of entrapped cells, it may not be able to take over the whole culture in a short period of time due to the limited growth of the entrapped cells. In order to examine the hypothesis that entrapped cells can have improved stability of MAb productivity due to limited cell growth, free-suspended cell culture and calcium alginate-entrapped cell culture with inocula consisting of a P and an NP were compared with regard to stability of MAb productivity in a repeated fed-batch culture. In free-suspended cell culture, the NP appeared to take over the whole culture within three batches, and thereby MAb production completely disappeared. In entrapped cell culture, an NP appeared to outgrow the P rapidly only during an exponential growth phase, resulting in a significant decrease in specific MAb productivity, qMAb, from 11.58 μg/106 cell/day to 2.76 μg/106 cell/day. However, when the cell growth was limited in entrapped cell culture, the NP no longer outgrew the P rapidly, as indicated by the stable value of qMAb. In addition, when the cells recovered from the alginate beads by citrate buffer treatment were subcultured in free-suspended cell culture, MAb production rapidly deteriorated and completely disappeared within two batches. Thus, the P present at a small fraction of viable cell concentration in the beginning of the free-suspended cell culture, which were previously entrapped in alginate beads, seemed to be outgrown rapidly by the NP. Taken together, the results obtained from these experiments support the hypothesis that the limited cell growth in entrapped cell culture, which keeps an NP from taking over the whole culture, is responsible, in part, for the improved stability of MAb productivity. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420917
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