ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (133)
  • cell culture  (92)
  • Electronic structure and strongly correlated systems
  • Humans
  • dispersion
  • Process Engineering, Biotechnology, Nutrition Technology  (79)
  • Technology  (54)
Collection
  • Articles  (133)
Source
Keywords
Publisher
Years
Topic
  • 1
    Electronic Resource
    Electronic Resource
    An Electrophoretic Method for Microstamping Biomolecule Gradients (2000)
    Springer
    Biomedical microdevices 2 (2000), S. 255-264 
    Details
    ISSN: 1572-8781
    Keywords: microstamping ; gradients ; electrophoresis ; bio- molecule ; cell culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract We have developed a technique for producing patterned biomolecule gradients on glass substrates using microstamping. The technique uses a microfabricated polydimethylsiloxane (PDMS) stamp with micrometer length features to transfer biomolecules to silane-derivatized substrates. The soaking solution for the stamp is subjected to an electric field to electrophoretically produce a gradient in solution and hence on the stamp. To test the efficacy of the procedure we tested substrates stamped with poly-D-lysine by fluorescently labeling the amine groups and measuring the fluorescence. It is possible to modify the steepness of the gradient using both voltage and electrode spacing, and the profile can be modeled using an isoelectric focusing model. Since gradients have been implicated in roles in guidance and patterning of neurons and other cell types, a flexible method to produce biomolecule gradients using microstamping may further extend the usefulness of microstamping to studies of cell patterning and guidance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009999004367
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A computerized technique for measuringin-situ concentrations during miscible displacements in porous media (1992)
    Springer
    Transport in porous media 7 (1992), S. 127-145 
    Details
    ISSN: 1573-1634
    Keywords: Miscible displacement ; dispersion ; in-situ concentration measurement ; computerized data acquisition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A technique for measurement of thein-situ concentration in an unconsolidated porous medium has been developed. The method involves measurement of electrical conductivityin-situ, under dynamic conditions, for flow involving brine of differing concentrations, at selected locations along the porous medium and relating it to the brine strength. Data acquisition and analysis is carried out using a Hewlett — Packard micro-computer and its interface. A user-friendly software was designed and developed for the system. The measurement technique was evaluated by studying the effect of brine concentration, brine flow rate, and by conducting miscible displacements experiment. The experimentally measured dispersion coefficients for the porous medium agreed closely with the value predicted by the correlation available in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647393
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Analytic Solution to a Problem of Seepage in a Chequer-Board Porous Massif (1997)
    Springer
    Transport in porous media 28 (1997), S. 109-124 
    Details
    ISSN: 1573-1634
    Keywords: seepage ; conductivity ; double-periodic structure ; advection ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A study is made of steady two-dimensional seepage in a porous massif composed by a double-periodic system of ‘white’ and ‘black’ chequers of arbitrary conductivity. Rigorous matching of Darcy's flows in zones of different conductivity is accomplished. Using the methods of complex analysis, explicit formulae for specific discharge are derived. Stream lines, travel times, and effective conductivity are evaluated. Deflection of marked particles from the ‘natural’ direction of imposed gradient and stretching of prescribed composition of these particles enables the elucidation of the phenomena of transversal and longitudinal dispersion. A model of pure advection is related with the classical one-dimensional vective dispersion equation by selection of dispersivity which minimizes the difference between the breakthrough curves calculated from the two models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006505908858
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Waves in partially saturated porous media (1992)
    Springer
    Transport in porous media 9 (1992), S. 25-37 
    Details
    ISSN: 1573-1634
    Keywords: Waves ; dispersion ; shock tube ; gas bubbles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The propagation of compressional waves in a porous medium is investigated in case the pore liquid contains a small volume fraction of gas. The effect of oscillating gas bubbles is taken into account by introducing a frequency-dependent fluid bulk modulus, which is incorporated in the Biot theory. Using a shock tube technique, new experimental data are obtained for a porous column subjected to a pressure step wave. An oscillatory behaviour is observed, consisting of two distinct frequency bands, which is predicted by the theoretical analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01039623
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    The prophylactic use of antibiotics in cell culture (1995)
    Springer
    Cytotechnology 19 (1995), S. 95-105 
    Details
    ISSN: 1573-0778
    Keywords: antibiotics ; cell culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This article describes the historical development of the prophylactic use of antibiotics in cell culture as well as their effects on cells. The influence of antibiotics on cell morphology, cellular degeneration and cell death and cellular function is summarized. Cellular DNA as well as protein synthesis are affected which can lead to interference with, or even changes in, metabolic processes. Such effects must be considered in cell culture research. As antibiotics are used in multifold ways, the otherwise standardized conditions in cell culture are no longer comparable. The prophylactic use of antibiotics is rejected for scientific reasons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749764
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    The use of a transport medium (L15M15) for bulk tissue storage and retention of viability (1989)
    Springer
    Cytotechnology 2 (1989), S. 181-185 
    Details
    ISSN: 1573-0778
    Keywords: culture ; media ; skin ; hypertrophic scar ; cell culture ; electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Twenty-five human or mouse tissue samples, some up to 8×4×2 cm, were immersed in a special transport medium (TM), L15M15, up to 7 days before being processed or placed in tissue culture. To test the efficacy of this medium, we concurrently placed pieces of the same tissues in a sterile phosphate buffered solution (PBS). We also tested the preservative capabilities of TM and PBS at room temperature and with refrigeration. Differences between TM and PBS are demonstrated, which are more pronounced using room temperature up to 4 days time. The tissues stored in TM show fewer degenerative or autolytic changes than the same tissue stored in PBS under identical conditions. Using regrigeration further enhanced the preservative qualities of TM up to 4 days, but not PBS. There were no obvious differences between tissues stored in TM and PBS with refrigeration after 7 days. We conclude that transport medium L15M15 is a useful medium for preserving tissue viability, especially large tissue samples, up to 4 days, especially if refrigerated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00133243
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Altered DNA topoisomerase II in multidrug resistance (1993)
    Springer
    Cytotechnology 11 (1993), S. 115-119 
    Details
    ISSN: 1573-0778
    Keywords: anticancer drugs ; at-MDR ; cell culture ; DNA topoisomerase II ; drug resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The characteristic feature of multidrug resistance (MDR) associated with drugs that interact with DNA topoisomerase II (topo II) is alterations in topo II activity or amount (at-MDR). We have characterized the at-MDR phenotype in human leukemic CEM cells selected for resistance to the topo II inhibitor, VM-26. Compared to drug-sensitive cells, the key findings are that at-MDR cells exhibit (i) decreased topo II activity; (ii) decreased drug sensitivity, activity and amount of nuclear matrix topo II; (iii) increased ATP requirement of topo II; (iv) a single base mutation in topo II resulting in a change of Arg to Gln at position 449, at the start of the motif B/nucleotide binding site; and (v) decreased topo II phosphorylation, suggesting decreased kinase or increased phosphatase activities. Recent results using single-stranded conformational polymorphism analysis reveals the presence of a mutation in the motif B/nucleotide binding site of the topo IIα gene in CEM at-MDR cells and in another leukemic cell line selected for resistance to m-AMSA. Finally, we have observed marked changes in the nuclear distribution of topo II in cells treated with anti-topo II drugs and have also found these changes to be attenuated in drug-resistant cells. We postulate that traditional inhibitors of topo II alter the equilibrium of the strand-passing reaction such that the number of enzyme-DNA covalent complexes increases. We further suggest that when the enzyme is bound to DNA it is protected from proteolysis, thus allowing more topo II molecules to be detected. We propose that MDR associated with alterations in topo II may have clinical consequences, and our current efforts involve exploiting these biochemical and molecular observations in the development of probes that may be useful to identify such drug resistant cells in the tumors of patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749000
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    A serum-free medium for hybridoma cell culture (1993)
    Springer
    Cytotechnology 11 (1993), S. 169-174 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; hybridoma ; monoclonal antibody ; serum-free medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effects of several different substances, including insulin, transferrin, ethanolamine, selenite and butyrate on the growth of murine hybridoma 2F7 cells, which secrete monoclonal antibody against small cell lung cancer, were investigated, and a serum-free medium SFMI was formulated. The effects of taurine, spermidine, progesterone and adenine on the cell growth were tested further on the basis of the medium SFMI, and a modified serum-free medium SFM II was established. On the basis of medium SFM II, the substitution tests of ferric citrate for transferrin were carried out, and it was found that transferrin could be replaced. The experiments suggested that the formulated serum-free medium was suitable for 2F7 cell growth and monoclonal antibody secretion, and thus facilitated subsequent purification of monoclonal antibody.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749866
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Growth of cells in a new defined protein-free medium (1993)
    Springer
    Cytotechnology 11 (1993), S. 219-231 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; chelators ; metal ion buffer ; serum-free medium ; serum replacement (serum substitute) ; trace elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The development of a new stable synthetic serum replacement (SSR) is described, which allows the cultivation of mammalian cells in a defined, protein-free medium containing only dialyzable components. With a low concentration of insulin (RPMI-SR2 medium), growth rates of the transformed cell lines L929, HELA S3, and the hybridoma 1E6 were comparable to growth rates obtained with a serum-containing medium. The same medium also supported long-term cultivation of non-dividing mouse macrophages. The main principle of SSR is a metal ion buffer containing a balanced mixture of iron and trace metals. Stability against precipitation of important metals is achieved by the combined use of EDTA and citric acid as chelating agents. Efficient iron supply is mediated through the inclusion of the compound Aurintricarboxylic acid as a synthetic replacement for transferrin. SSR also contains a growth-promoting surfactant, Pluronic F68. Thus SSR provides a general foundation for growth and differentiation normally provided by serum. Limitations of other serum-free medium designs are discussed here: 1) the inability of transferrin to chelate all metals in the medium; and 2) the use of inorganic iron salts or iron citrate as an iron supplement leads to rapid precipitation of iron hydroxide in the medium. Both these problems are solved in the design of SSR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749873
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Pilot production of u-PA with porous microcarrier cell culture (2000)
    Springer
    Cytotechnology 33 (2000), S. 13-19 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; porous microcarrier ; prourokinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A recombinant DNA CHO cell line secretingurokinase-type plasminogen activator (u-PA) wascultivated with Cytopore cellulose porousmicrocarriers in a 30l Biostat UC stirred tankreactor. After 26 days of culture, using a spinfilter toretain cells in bioreactor, the cell density couldreach 1.33 × 107 ml-1. The maximal u-PAactivity in supernatant was 7335 IU·ml-1, and204l supernatant containing 7.1 g u-PA was harvested.After 100 days of culture with 0.1% fetal bovineserum medium, a modified cell retention system whichcan be washed-out backward, substituted thespinfilter to prevent filter clogging. The maximalcell density was over 107 ml-1, the maximalu-PA activity in supernatant reached 6250IU·ml-1, and 1604l supernatant containing about51 g u-PA was harvested. Compared to perfusionculture, batch medium-replaced culture could raiseutilizing efficiency of the medium, increase cell specificproductivity and improve the quality of the product which wasnot steady in a 37 °C environment. Cells can movefrom seed porous microcarriers occupied by cells tovacant microcarriers spontaneously, withouttrypsinization, and continue to grow until all microcarriers contained cells. It shows that Cytoporeporous microcarriers are very useful and convenient toscale up cultivation step by step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008127310890
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    Flow Injection Analysis for Simultaneous Quantification of Prolactin Concentration and Glycosylation Macroheterogeneity in Cell Culture Samples (2000)
    Springer
    Cytotechnology 34 (2000), S. 237-242 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; flow injection analysis ; glycosylation ; macro-heterogeneity ; prolactin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A flow injection analysis (FIA) system is presented for a twostep immunoassay-based determination of the total humanprolactin (hPRL) concentration along with its degree ofglycosylation. Separate measurement of total hPRL and nonglysosylated human prolactin (nG-hPRL) were made using twoflow-through cartridges each containing immobilized antibodiesof different specificity. The antibodies are immobilized on thesurface of a carrier. Glycosylated hPRL (G-hPRL) and, thus, thedegree of glycosylation were calculated by the differencebetween the two specific determinations. Enhanced specificityfor the determination of nG-hPRL was obtained using unfavorablebinding conditions through incorporation of alkaline pH andchaotropic agents into the carrier/dispersion buffer. The assayfor total hPRL and nG-hPRL were each found to be linear withinthe relevant concentration range. The results of the two-stepFIA method were found to agree with those obtained by thestandard methods of ELISA and western blotting while offeringthe advantage of minimal analysis time (10 min) and eliminationof manual manipulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008170023099
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Kinetics of retroviral production from the amphotropic ΨCRIP murine producer cell line (1996)
    Springer
    Cytotechnology 22 (1996), S. 185-195 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; half-life ; packaging cells ; retrovirus ; titer ; ΨCRIP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Rapidly expanding development and practice of gene therapy requires the availability of large quantities of high titer retroviral supernatants. One way to achieve high retroviral titers is through improved understanding of the kinetics of retroviral production and decay, and the subsequent development of improved cell culture methods. In the present study we investigated the effects of different operational modes on the retroviral production of the NIH 3T3 fibroblast derived amphotropic murine retroviral producing cell line pMFG/ΨCRIP. Semi-continuous culture (exchange of 50% of medium volume daily) was found to promote cell growth and enhance retroviral production. The rapid medium exchange resulted in significantly larger amounts of high titer supernatants and an extended production phase as compared to the batch control cultures. The specific viral productivity of the pMFG/ΨCRIP cells was in the range of 10 to 40 infectious viruses produced per thousand producer cells per day. The CV-1 African Green Monkey kidney cell line was used as the infection target. Lowering the serum level form 20% to 10% improved retroviral production slightly. However, at lower serum levels (1%, 5% and 10% (v/v)) growth of the producer cell line, and thus retroviral production, was directly proportional to the serum level. The half-life of the virus at 37°C was found to be 5.5 hours. Promoting the growth of producer cell lines can improve retroviral vectors titers and viral production. High cell density systems that allow for rapid cell growth and waste product removal are likely to be used to generate high-titer retroviral supernatants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353938
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Studies of serum-free medium for the generation of lymphokine-activated killer cells (1991)
    Springer
    Cytotechnology 6 (1991), S. 39-47 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; lymphocyte ; lymphokine-activated killer cell ; recombinant interleukin 2 ; serum-free medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We examined a serum-free medium (designated as TYI 101) for the generation of lymphokine-activated killer (LAK) cells from human lymphocytes, regional lymph node lymphocytes (RLNL) and peripheral blood lymphocytes (PBL). TYI 101 medium consisted of, in addition to nutrient mixture, transferrin, insulin, fetuin, sodium selenite, 2-mercaptoethanol, o-phosphorylethanolamine, chick egg yolk and porcine kidney extract. These hormones were effective for supporting RLNL proliferation as assessed by (3H)-thymidine uptake. When human lymphocytes from two different sources were cultivated with recombinant interleukin 2 (rIL-2) in TYI 101 medium, LAK activity was generated. In cultures of PBL from a healthy donor, LAK cells were generated in TYI 101 medium as efficiently as in RPMI 1640 medium supplemented with 10% human AB-type serum (RPMI-AB). In cultures of RLNL from lung cancer patients, LAK activity obtained in TYI 101 medium was about sixty-five percent of that in RPMI-AB. However, the addition of a small amount of AB-type serum improved the generation of LAK activity, LAK cell expansion, and cell viability in TYI 101 medium. We conclude that TYI 101 medium can be used for the generation of LAK cells from human lymph node lymphocytes with supplementation of none or only a reduced amount of human serum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353701
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Development of a new culture system for human lymphokine-activated killer cells: Comparison with a conventional static culture method (1991)
    Springer
    Cytotechnology 7 (1991), S. 75-83 
    Details
    ISSN: 1573-0778
    Keywords: adoptive immunotherapy ; cell culture ; cell culture apparatus ; Interleukin-2 ; lymphokine-activated killer cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We recently developed a new culture system based on dialysis perfusion (designated JCC-device) for the generation and expansion of human lymphokine-activated killer (LAK) cells (Murata et al., 1990). More recently we have scaled up the volume of the culture vessel of the JCC-device from 100 ml to 400 ml for clinical use. In the present study, using this new 400 ml JCC-device, we cultured human lymph node lymphocytes (LNL) obtained from 8 surgical patients with primary lung cancer, and investigated the cellular characteristics in comparison with a conventional batchwise culture system using tissue culture dishes. With the JCC-device, the cell density reached a maximum 2.7×107 cells/ml with greater than 90% viability by the appropriate exchange of perfusion medium and by making additions at the appropriate intervals for recombinant interleukin-2 (rIL-2). The expansion fold of LNL with the JCC-device, ranging 6.6- to 19.2-fold (mean 13.8-fold), was not significantly different from that in dish cultures. There was no marked difference in cell surface phenotypes between the two culture systems in 7 out of 8 cases. As for LAK activity of LNL, the JCC culture was either superior or equal in 4 out of 8 cases, but inferior in the other 4 cases to the conventional dish cultures. In the latter cases, the usage of serum for the JCC culture was limited, which might have resulted in the low LAK activity. The JCC-device was able to reduce the consumption of basal medium, rIL-2 and serum by 20%, 84% and 96%, respectively compared to the conventional tissue culture systems. The JCC-device improved the routine performance of adoptive immunotherapy with LAK cells and rIL-2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350913
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Production of interferon-β in a culture of fibroblast cells on some polymeric films (2000)
    Springer
    Cytotechnology 34 (2000), S. 165-173 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; enhanced production ; fibroblast cells ; interferon-β ; Langmuir-Blodgett film
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Normal human skin (NB1-RGB) cells were cultured in the presenceof polyinosinic and polycytidylic acids, diethylaminoethyldextran, cycloheximide and actinomycin D, which induced humaninterferon-β. The simplest induction method, that requiredonly polyinosinic and polycytidylic acids and diethylaminoethyldextran was found to give the highest production ofinterferon-β by the cells. The cell growth and productionof interferon-β were investigated for NB1-RGB cellscultured on silk fibroin, poly(γ-methyl-L-glutamate),poly(γ-benzyl-L-glutamate) and collagen films prepared bythe Langmuir-Blodgett (LB) and casting methods. The cell densityof NB1-RGB cells cultured on the LB films was found to be higherthan that on the cast films made of the same polymer. Thisindicates that not only the chemical structure of the polymersused for the preparation of the films but the preparationmethods of the films, i.e., casting and LB methods, are also astrong factor affecting the cell growth. The production ofinterferon-β per unit number of cells was found to behigher on the cast films than that on the LB films made of thesame polymer. This is explained by the fact that the optimalsuppressed growth of NB1-RGB cells on the cast films leads tothe enhanced production of interferon-β on the cast filmscompared to those on the LB films prepared by the same polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008130223190
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    The usefulness of CHAPS as a non-cytotoxic stabilizing agent in purification of growth factors (1988)
    Springer
    Cytotechnology 1 (1988), S. 309-318 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; FGF ; growth factors ; protein sequencing ; zwitterionic detergent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Among several detergents, a zwitterionic detergent, 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS), was found to be least cytotoxic for cultured mammalian cells. CHAPS improved the activity recovery and elution profile of crude and purified fibroblast growth factors (FGFs) during chromatographies. Diluted preparations of FGFs were stabilized by CHAPS against the loss during storage. Amino acid sequence analysis was not disturbed by CHAPS. CHAPS was removable by reversed-phase high-performance liquid chromatography. These results indicate that CHAPS is useful as a non-cytotoxic stabilizing agent in purification of various kinds of bioactive polypeptides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365076
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Distinct volume distribution of viable and non-viable hybridoma cells: A flow cytometric study (1989)
    Springer
    Cytotechnology 2 (1989), S. 85-94 
    Details
    ISSN: 1573-0778
    Keywords: hybridoma ; cell volume ; cell culture ; flow cytometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Light scattering properties of hybridoma cells were examined with flow cytometry. Viable and dead cells form two distinct populations. The distribution of the two populations changes during a batch culture. the concentration of dead cells measured by flow cytometry correlates well to that measured by hemacytometer. The distribution based on small-angle light scattering is similar to the distribution based on volume as measured by Elzone particle counter. It thus appears that viable cells form the population with a larger mean cell volume. The results also indicate that the volume of viable cells decreases during the cultivation while that of dead cells remains relatively constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386140
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Homogenisation and oxygen transfer rates in large agitated and sparged animal cell bioreactors: Some implications for growth and production (1996)
    Springer
    Cytotechnology 22 (1996), S. 87-94 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; mixing time ; oxygen demand ; oxygen transfer ; pH and dO2 sensitivity ; scale-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Because of concern for cell damage, very low agitation energy inputs have been used in industrial animal cell bioreactors, typical values being two orders of magnitude less than those found in bacterial fermentations. Aeration rates are also very small. As a result, such bioreactors might be both poorly mixed and also unable to provide the higher oxygen up-take rates demanded by more intensive operation. This paper reports experimental studies both of K L a and of mixing (via pH measurements) in bioreactors up to 8 m3 at Wellcome and of scaled down models of such reactors at Birmingham. Alongside these physical measurements, sensitivity of certain cell lines to continuously controlled dO2 has been studied and the oxygen up-take rates measured in representative growth conditions. An analysis of characteristic times and mixing theory, together with other recent work showing that more vigorous agitation and aeration can be used especially in the presence of Pluronic F-68, indicates ways of improving their performance. pH gradients offer a special challenge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353927
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Engineering challenges in high density cell culture systems (1996)
    Springer
    Cytotechnology 22 (1996), S. 3-16 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; process monitoring ; oxygenation ; CO2 transfer ; aggregation ; segregation ; diffusion, on-line monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract High density cell culture systems offer the advantage of production of bio-pharmaceuticals in compact bioreactors with high volumetric production rates; however, these systems are difficult to design and operate. First of all, the cells have to be retained in the bioreactor by physical means during perfusion. The design of the cell retention is the key to performance of high density cell culture systems. Oxygenation and media design are also important for maximizing the cell number. In high density perfusion reactors, variable cell density, and hence the metabolic demand, require constant adjustment of perfusion rates. The use of cell specific perfusion rate (CSPR) control provides a constant environment to the cells resulting in consistent production. On-line measurement of cell density and metabolic activities can be used for the estimation of cell densities and the control of CSPR. Issues related to mass transfer and mixing become more important at high cell densities. Due to the difference in mass transfer coefficients for oxygen and CO2, a significant accumulation of dissolved CO2 is experienced with silicone tubing aeration. Also, mixing is observed to decrease at high densities. Base addition, if not properly done, could result in localized cell lysis and poor culture performance. Non-uniform mixing in reactors promotes the heterogeneity of the culture. Cell aggregation results in segregation of the cells within different mixing zones. This paper discusses these issues and makes recommendations for further development of high density cell culture bioreactors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353919
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    The changing role of cell culture in the generation of transgenic livestock (1999)
    Springer
    Cytotechnology 31 (1999), S. 3-8 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; livestock ; milk ; nuclear transfer ; transgenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Transgenesis may allow the generation of farm animals with altered phenotype, animal models for research and animal bioreactors. Although such animals have been produced, the time and expense involved in generating transgenic livestock and then evaluating the transgene expression pattern is very restrictive. If questions about the ability and efficiency of expression could be asked solely in vitro rapid progress could be achieved. Unfortunately, experiments addressing transcriptional control in vitro have proved unreliable in their ability to indicate whether a transgene will be transcribed or not. However, initial studies suggest that cell culture may be able to predict in vivo post-transcriptional events. We review these issues and propose that strategies which engineer the transgene integration site could enhance the probability for efficient expression. This approach has now become feasible with the development of techniques allowing animals to be generated from somatic cells by nuclear transfer. The important step in this procedure is the use of cells grown in culture as the source of genetic information, allowing the selection of specific transgene integration events. This technology which has dramatically increased the potential use of transgenic livestock for both agricultural and biotechnological applications, is based on standard cell culture methodology. We are now at the start of a new era in large animal transgenics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008044517150
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 21
    Electronic Resource
    Electronic Resource
    Improved culture conditions forCowdria ruminantium (Rickettsiales), the agent of heartwater disease of domestic ruminants (1990)
    Springer
    Cytotechnology 4 (1990), S. 285-290 
    Details
    ISSN: 1573-0778
    Keywords: heartwater ; cell culture ; Cowdria ruminantium ; bovine vascular endothelial cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The causal agent of heartwater disease of domestic ruminants,Cowdria ruminantium, can, with difficulty, be isolated and passaged in lines of bovine endothelial cells grown in the presence of the Glasgow modification of Eagle's minimal essential medium. However, when Leibovitz's L-15 medium supplemented with 0.45% glucose at pH 6.0–6.5 is used as maintenance medium for these cells, isolation and serial passage may routinely be achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00563789
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 22
    Electronic Resource
    Electronic Resource
    Adaptation of mammalian cells to non-ammoniagenic media (1994)
    Springer
    Cytotechnology 15 (1994), S. 87-94 
    Details
    ISSN: 1573-0778
    Keywords: Adaptation ; ammonia ; cell culture ; glutamine ; glutamate ; dipeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Although glutamine is used as a major substrate for the growth of mammalian cells in culture, it suffers from some disadvantages. Glutamine is deaminated through storage or by cellular metabolism, leading to the formation of ammonia which can result in growth inhibition. Non-ammoniagenic alternatives to glutamine have been investigated in an attempt to develop strategies for obtaining improved cell yields for ammonia sensitive cell lines. Glutamate is a suitable substitute for glutamine in some culture systems. A period of adaptation to glutamate is required during which the activity of glutamine synthetase and the rate of transport of glutamate both increase. The cell yield increases when the ammonia accumulation is decreased following culture supplementation with glutamate rather than glutamine. However some cell lines fail to adapt to growth in glutamate and this may be due to a low efficiency transport system. The glutamine-based dipeptides, ala-gln and gly-gln can substitute for glutamine in cultures of antibody-secreting hybridomas. The accumulation of ammonia in these cultures is less and cell yields in dipeptide-based media may be improved compared to glutamine-based controls. In murine hybridomas, a higher concentration of gly-gln is required to obtain comparable cell growth to ala-gln or gln-based cultures. This is attributed to a requirement for dipeptide hydrolysis catalyzed by an enzyme with higher affinity for ala-gln than gly-gln.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00762382
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 23
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 24
    Electronic Resource
    Electronic Resource
    Detection of mycoplasma contaminations by the polymerase chain reaction (1994)
    Springer
    Cytotechnology 16 (1994), S. 67-77 
    Details
    ISSN: 1573-0778
    Keywords: Mycoplasma ; cell culture ; clinical testing ; microbial screening ; PCR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The polymerase chain reaction (PCR) has been used for the general detection ofMollicutes. 25Mycoplasma andAcholeplasma species were detected including important contaminants of cell cultures such asM. orale, M. arginini, M. hyorhinis, M. fermentans, A. laidlawii and additional human and animal mycoplasmas. PCR reactions were performed using a set of nested primers defined from conserved regions of the 16S rRNA gene. The detection limit was determined to be 1 fg mycoplasma DNA, which is equivalent to 1–2 genome copies of the 16S rRNA coding region. The identity of the amplification products was confirmed by agarose gel electrophoresis and restriction enzyme analysis. DNA from closely and distantly related micro-organisms did not give rise to specific amplification products. The method presented here offers a much more sensitive, specific and rapid assay for the detection of mycoplasmas than the existing ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00754609
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 25
    Electronic Resource
    Electronic Resource
    Effects of peptone on hybridoma growth and monoclonal antibody formation (1994)
    Springer
    Cytotechnology 16 (1994), S. 147-150 
    Details
    ISSN: 1573-0778
    Keywords: Hybridoma ; peptone ; monoclonal antibody ; cell culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hybridoma WuT3 secreting a monoclonal antibody against T lymphocytes was grown in RPMI 1640 medium supplemented with 1% human serum. The effect of the concentration of peptone, as an additive, was investigated on cell growth, monoclonal antibody formation, and cell metabolism over 0–10 g l−1 range. It was found that 1–5 g l−1 peptone can significantly promote the growth of cells and increase the formation of monoclonal antibody, especially at 3–5 g l−1, when both the accumulating level and secretion rate of monoclonal antibody are higher than that at other peptone concentrations. Based on glucose, lactate and ammonia analysis data, the efficiency of glycolysis was assessed and the utilization of amino acids was more efficient at 3–5 g l−1 peptone. The cell growth and monoclonal antibody formation were inhibited at higher peptone concentrations, e.g. 10 g l−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749901
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 26
    Electronic Resource
    Electronic Resource
    A new method for the encapsulation of mammalian cells (1991)
    Springer
    Cytotechnology 7 (1991), S. 121-130 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; cellulose sulphate ; encapsulation ; monoclonal antibodies ; poly-dimethyl-diallyl-ammoniumchloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A new encapsulation method was developed for the cultivation of mammalian cells. The capsules were produced using a solution of sodium cellulose sulphate (CS)(1.5%) and poly-dimethyl-diallyl-ammoniumchloride (PDMDAAC). When CS droplets fell into the precipitation bath consisting of a 2% solution of PDMDAAC, immediately a membrane at the interphase was built up. The influences of varying encapsulation process parameters on capsule characteristics, cell growth, and monoclonal antibody production were tested. This new method showed advantages when compared to other methods mainly due to time simplicity of the whole process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350918
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 27
    Electronic Resource
    Electronic Resource
    A compatible support system for cell culture in biomedical research (1990)
    Springer
    Cytotechnology 4 (1990), S. 181-189 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; microperfusion ; luminal-antiluminal media gradients ; specific support ; extracellular matrix proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The lack of a suitable system to culture epithelial cells for a long period under a luminal-antiluminal medium gradient, was the reason to develop a new system. It consists of an interchangeable sheet of permeable support material, which is set in place by two tight fitting holding rings. For special demands the supports can be coated with extracellular matrix proteins improving cellular attachment and terminal differentiation. The handling of the sheets by forceps proceeds easily and quickly, thus fastening the transfer of cultured cells without additional manipulations. The sheets can be transferred to a newly developed microperfusion chamber on which an apical and a basal perfusion over a long culture period parallel to a transepithelial electrophysiological registration becomes possible. The chamber has an extremely low amount of fluid dead space. The separate perfusion of cultured cells under isotonic, hypotonic or hypertonic conditions opens new possibilities. Thus, culture can be performed under most natural conditions e.g., that found within the kidney.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365099
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 28
    Electronic Resource
    Electronic Resource
    Serum-free culture of carcinoma cell lines (1991)
    Springer
    Cytotechnology 5 (1991), S. 31-46 
    Details
    ISSN: 1573-0778
    Keywords: serum-free ; cell culture ; carcinoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365532
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 29
    Electronic Resource
    Electronic Resource
    On the transient non-Fickian dispersion theory (1996)
    Springer
    Transport in porous media 23 (1996), S. 107-124 
    Details
    ISSN: 1573-1634
    Keywords: solute transport ; Fick's law ; dispersion ; dispersivity ; equation of motion ; non-Fickian dispersion equation ; scale effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The Fickian dispersion equation is the basic relationship used to describe the nonconvective mass flux of a solute in a porous medium. This equation prescribes a linear relationship between the dispersive mass flux and the concentration gradient. An important characteristic of the Fickian relationship is that it is independent of the history of dispersion (e.g. the time rate of change of the dispersion flux). Also, the dispersivities are supposed to be medium constants and invariant with temporal and spatial scales of observation. It is believed that in general these restrictions do not hold. A number of authors have proposed various alternative relationships. For example, differential equations have been employed that prescribe a relationship between the dispersion flux and its time and space derivatives. Also, stochastic theories result in integro-differential equations in which dispersion tensor grow asymptotically with time or distance. In this work, three different approaches, which lead to three different non-Fickian equations with a transient character, are discussed and their primary features and differences are highlighted. It is shown that an effective dispersion tensor defined in the framework of the transient non-Fickian theory, grows asymptotically with time and distance; a result which also follows from stochastic theories. Next, principles of continuum mechanics are employed to provide a solid theoretical basis for the non-Fickian transient dispersion theory. The equation of motion of a solute in a porous medium is used to provide a rigorous derivation of various dispersion relationships valid under different conditions. Under various simplifying assumptions, the generalized theory is found to agree with the conventional Fickian theory as well as several other non-Fickian relationships found in the literature. Moreover, it is shown that for nonconservative solutes, the traditional dispersion tensor is affected by the rate of mass exchange of the solute.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00145268
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 30
    Electronic Resource
    Electronic Resource
    Two-dimensional adaptive Eulerian-Lagrangian method for mass transport with spatial velocity distribution (1988)
    Springer
    Transport in porous media 3 (1988), S. 473-489 
    Details
    ISSN: 1573-1634
    Keywords: Advection ; dispersion ; particles ; characteristics ; finite-element ; continuous fluid velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A Eulerian-Lagrangian scheme is used to solve the two-dimensional advection-dispersion equation. Concentration and its partial differential operator are decomposed into advection and dispersion terms. Thus, advection is formally decoupled from dispersion and solved by continuous forward particle tracking. Dispersion is handled by implicit finite elements on a fixed Eulerian grid. Translation of steep gradients of concentration in advection-dominated flow regimes, is done without numerical distortion. Continuous spatial distribution of velocities are evaluated by using Galerkin's approach in conjunction with Darcy's law based on hydraulic input data from each element. The method was implemented on coarse FE grid with linear shape functions, demonstrating no over/under shooting and practically no numerical dispersion. Simulations, covering a wide range of Peclet numbers, yield high agreement with analytic and practical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00138612
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 31
    Electronic Resource
    Electronic Resource
    The effect of dispersion model on the linear stability of miscible displacement in porous media (1989)
    Springer
    Transport in porous media 4 (1989), S. 85-96 
    Details
    ISSN: 1573-1634
    Keywords: Stability ; linear stability analysis ; miscible displacement ; aspect ratio ; mobility control ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Chang and Slattery (1986, 1988b) introduced a simplified model of dispersion that contains only two empirical parameters. The traditional model of dispersion (Nikolaevskii, 1959; Bear, 1961; Scheidegger, 1961; de Josselin de Jong and Bossen, 1961; Peaceman, 1966; Bear, 1972) has three empirical parameters, two of which can be measured in one-dimensional experiments while the third, the transverse dispersivity, must be measured in experiments in which a two-dimensional concentration profile develops. It is found that nearly the same linear stability behavior results from using either model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00134743
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 32
    Electronic Resource
    Electronic Resource
    The influence of free convection on soil salinization in arid regions (1996)
    Springer
    Transport in porous media 23 (1996), S. 275-301 
    Details
    ISSN: 1573-1634
    Keywords: free convection ; through flow ; vadoze zone ; salinization ; dispersion ; multigrid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Evaporation of groundwater in a region with a shallow water table and small natural replenishment causes accumulation of salts near the ground surface. Water in the upper soil layer becomes denser than in the depth. This is a potentially unstable situation which may result in convective currents. When free convection takes place, estimates of the salinity profile, salt precipitation rate, etc., obtained within the framework of a 1-D (vertical) model fail. Very simplified model of the process is proposed, in which the unsaturated zone is represented by a horizontal soil layer at a constant water saturation, and temperature changes are neglected. The purpose of the model is to obtain a rough estimate of the role of natural convection in the salinization process. A linear stability analysis of a uniform vertical flow is given, and the stability limit is determined numerically as a function of evaporation rate, salt concentration in groundwater, and porous medium dispersivity. The loss of stability corresponds to quite realistic Rayleigh numbers. The stability limit depends in nonmonotonic way on the evaporation rate. The developed convective regime was simulated numerically for a 2-D vertical domain, using finite volume element discretization and FAS multigrid solver. The dependence of the average salt concentration in the upper layer on the Rayleigh number was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167100
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 33
    Electronic Resource
    Electronic Resource
    Influence of capillary pressure, adsorption and dispersion on chemical flood transport phenomena (1996)
    Springer
    Transport in porous media 24 (1996), S. 275-296 
    Details
    ISSN: 1573-1634
    Keywords: chemical flooding ; ternary ; immiscible ; surfactant ; numerical simulation ; interfacial tension ; phase behavior ; miscibility ; capillarity ; numerical grid ; adsorption ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This is the second of two joint papers which study the influence of several physical properties on the transport phenomena in chemical flooding. To that aim, we use a previously reported ternary two-phase model into which representative physical properties have been incorporated as concentration-dependent functions. Physical properties such as phase behavior, interfacial tensions, residual saturations, relative permeabilities, phase viscosities and wettability have been analyzed in the first paper. In this paper, we discuss the influence of capillary pressure, adsorption of the chemical component onto the rock and dispersion. Although arising from different phenomenological sources, these transport mechanisms show some similar effects on concentration profiles and on oil recovery. They are studied for systems with different phase behavior. A numerical analysis is also presented in order to determine the relevance of the number of grid blocks taken in the discretization of the differential equations. This numerical analysis provides useful guidelines for the selection of the appropriate numerical grid in each type of displacement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154094
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 34
    Electronic Resource
    Electronic Resource
    Saltwater transport in a heterogeneous formation: A case study (1988)
    Springer
    Transport in porous media 3 (1988), S. 217-256 
    Details
    ISSN: 1573-1634
    Keywords: Salinity ; advection ; dispersion ; aquifers ; flow model ; transport model ; simulation ; sea water ; connate water ; leakage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Historical information of the hydraulic and salinity aspect, detailed geological information, and information on the physical characteristics of the different layers comprising the formation, are needed for simulating the saltwater transport process in aquifers. In most simulation studies of field situations, there is an inadequacy of data and the modeller has to make justifiable assumptions to analyze a particular situation in order to provide an insight into the problem. A quasi-three-dimensional solute transport model is used to analyze the saltwater encroachment phenomena in aquifers underlying the City of Bangkok; first by calibrating the model's performance with available historical data and then by assessing the extent of future saltwater encroachment with the implementation of the regulatory pumpage to be followed in order to restrict the alarming rate of land subsidence. Model simulation indicates a substantial reduction in the rate of encroachment of the saltwater front with a reduction of pumpage after 1987.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235330
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 35
    Electronic Resource
    Electronic Resource
    An adaptive domain decomposition method for simulation of transport in porous media (1988)
    Springer
    Transport in porous media 3 (1988), S. 549-562 
    Details
    ISSN: 1573-1634
    Keywords: Adaptive mesh ; finite element method ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A Galerkin finite element method is used along with a self-adaptive strategy of domain discretisation to model dispersion in an axisymmetric cylindrical porous medium. A solution strategy is proposed based on the use of a Gear scheme for the time stepping and partial vectorisation of the code. The domain is highly discretised in the area of the sharp transient front, while the remainder is coarsely discretised. The area covered by the fine mesh is determined by the value of the local concentration gradients. Numerical results are presented for the one and two dimensional cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00959102
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 36
    Electronic Resource
    Electronic Resource
    On the Influence of Pore-Scale Dispersion in Nonergodic Transport in Heterogeneous Formations (1998)
    Springer
    Transport in porous media 30 (1998), S. 57-73 
    Details
    ISSN: 1573-1634
    Keywords: groundwater ; nonergodic transport ; dispersion ; heterogeneous formations ; hydrogeology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Flow of an inert solute in an heterogeneous aquifer is usually considered as dominated by large-scale advection. As a consequence, the pore-scale dispersion, i.e. the pore scale mechanism acting at scales lower than that characteristic of the heterogeneous field, is usually neglected in the computation of global quantities like the solute plume spatial moments. Here the effect of pore-scale dispersion is taken into account in order to find its influence on the longitudinal asymptotic dispersivity D11we examine both the two-dimensional and the three-dimensional flow cases. In the calculations, we consider the finite size of the solute initial plume, i.e. we analyze both the ergodic and the nonergodic cases. With Pe the Péclat number, defined as Pe=Uλ/D, where U, λ, D are the mean fluid velocity, the heterogeneity characteristic length and the pore-scale dispersion coefficient respectively, we show that the infinite Péclat approximation is in most cases quite adequate, at least in the range of Péclat number usually encountered in practice (Pe 〉 102). A noteworthy exception is when the formation log-conductivity field is highly anisotropic. In this case, pore-scale may have a significant impact on D11, especially when the solute plume initial dimensions are not much larger than the heterogeneities' lengthscale. In all cases, D11 appears to be more sensitive to the pore-scale dispersive mechanisms under nonergodic conditions, i.e. for plume initial size less than about 10 log-conductivity integral scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006548529015
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 37
    Electronic Resource
    Electronic Resource
    A Solute Transport in Stratified Media (1998)
    Springer
    Transport in porous media 31 (1998), S. 133-143 
    Details
    ISSN: 1573-1634
    Keywords: transport ; solute ; flux-averaged concentration ; stratification ; conductivity ; distribution ; arrival time ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Two-dimensional and steady solute transport in a stratified porous formation is analysed under assumption that the effect of pore-scale dispersion is negligible. The longitudinal dispersion produced as a result of the vertical variation of hydraulic conductivity is analysed by averaging the variability of a solute flux concentration and conductivity. The evolution of the solute flux concentration is expressed with respect to the correlated variable, that is the travel (arrival) time τ at a fixed location and the averaging procedure is constructed to satisfy the boundary condition where the inlet concentration is a known function of time. In such a statement, a velocity-averaged solute flux concentration is described by a conventional dispersion model (CDM) with a dispersion coefficient which is a function of the arrival time. It is demonstrated that such CDM satisfies the assumption that hydraulic conductivity of the layers is gamma distributed with the parameter of distribution which is chosen to represent a reasonable value of the field scale solute dispersion. The overall behaviour of the model is illustrated by several examples of two-dimensional mass transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006557032656
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 38
    Electronic Resource
    Electronic Resource
    Comment on ‘fractal and superdiffusive transport and hydrodynamic dispersion in heterogeneous porous media’, by Muhammad Sahimi (1995)
    Springer
    Transport in porous media 21 (1995), S. 175-188 
    Details
    ISSN: 1573-1634
    Keywords: diffusion ; dispersion ; percolation ; fractals ; scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Two fundamental questions regarding the application of percolation theory to transport in porous media are addressed. First, when ‘critical path’ arguments (based on a sufficiently wide spread of microscopic transition rates) are invoked (in analogy to the case of transport in disordered semiconductors) to justify the application of percolation theory to the determination of relevant transport properties, then for long time scales (compared to the inverse of the ‘critical’ percolation rate), the fractal structure of the ‘critical’ path is relevant to transport, but not at short time scales. These results have been demonstrated concretely in the case of disordered semiconductors, and are in direct contradiction to the claims of the review. Second, the relevance of deterministic or stochastic methods to transport has been treated heretofore by most authors as a question of practicality. But, at least under some conditions, concrete criteria distinguish between the two types of transport. Percolative (deterministic) transport is temporally reproducible and spatially inhomogeneous while diffusive (stochastic) transport is temporally irreproducible, but homogeneous, and a cross-over from stochastic to percolative transport occurs when the spread of microscopic transition rates exceeds 4–5 orders of magnitude. It is likely that such conditions are frequently encountered in soil transport. Moreover, clear evidence for deterministic transport (although not necessarily percolative) exists in such phenomena as preferential flow. On the other hand, the physical limitation of transport to (fractally connected) pore spaces within soils (analogously to transport in metal-insulator composites) can make transport diffusive on a fractal structure, rather than percolative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613755
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 39
    Electronic Resource
    Electronic Resource
    A Fickian diffusion model for the spreading of liquid plumes infiltrating in heterogeneous media (1996)
    Springer
    Transport in porous media 24 (1996), S. 1-33 
    Details
    ISSN: 1573-1634
    Keywords: unsaturated flow ; large-scale averaging ; dispersion ; high-resolution numerical simulations ; NAPL spills
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Infiltration of water and non-aqueous phase liquids (NAPLs) in the vadose zone gives rise to complex two- and three-phase immiscible displacement processes. Physical and numerical experiments have shown that ever-present small-scale heterogeneities will cause a lateral broadening of the descending liquid plumes. This behavior of liquid plumes infiltrating in the vadose zone may be similar to the familiar transversal dispersion of solute plumes in single-phase flow. Noting this analogy we introduce a mathematical model for ‘phase dispersion’ in multiphase flow as a Fickian diffusion process. It is shown that the driving force for phase dispersion is the gradient of relative permeability, and that addition of a phase-dispersive term to the governing equations for multiphase flow is equivalent to an effective capillary pressure which is proportional to the logarithm of the relative permeability of the infiltrating liquid phase. The relationship between heterogeneity-induced phase dispersion and capillary and numerical dispersion effects is established. High-resolution numerical simulation experiments in heterogeneous media show that plume spreading tends to be diffusive, supporting the proposed convection-dispersion model. Finite difference discretization of the phase-dispersive flux is discussed, and an illustrative application to NAPL infiltration from a localized source is presented. It is found that a small amount of phase dispersion can completely alter the behavior of an infiltrating NAPL plume, and that neglect of phase-dispersive processes may lead to unrealistic predictions of NAPL behavior in the vadose zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175602
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 40
    Electronic Resource
    Electronic Resource
    A linear stability analysis for miscible displacements (1986)
    Springer
    Transport in porous media 1 (1986), S. 179-199 
    Details
    ISSN: 1573-1634
    Keywords: Stability ; linear stability analysis ; miscible displacement ; dispersion ; mobility control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A linear stability analysis has been performed for a miscible displacement in a semi-infinite system of finite thickness and unbounded width. A more general description of dispersion has been adopted than those used by previous workers. It is shown that, when there is a step change in concentration and the mobility ratio is unfavorable, the displacement can be unstable at the injection boundary. But, if the concentration is changed sufficiently slowly with time at the entrance to the system, the displacement is stable to infinitesimal perturbations, no matter how unfavorable the mobility ratio. When the mobility ratio is favorable, the displacement is unconditionally stable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714691
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 41
    Electronic Resource
    Electronic Resource
    Issues in flow and transport in heterogeneous porous media (1986)
    Springer
    Transport in porous media 1 (1986), S. 319-338 
    Details
    ISSN: 1573-1634
    Keywords: heterogeneity ; dispersion ; saturated flow ; unsaturated flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This invited lecture enumerates various categories of flow and transport in heterogeneous media with particular reference to this Symposium. Specific attention is given to five topics within these categories. (1) We explore the compounding of spatially variable local permeability K to produce an apparent permeability K * on a scale large compared with that of variation of K. An inverse method generates and analyzes flow systems with K spatially periodic in two and three dimensions. (2) Physical arguments indicate that apparent hydraulic properties of an unsaturated composite medium may not represent any conceivable mean of the properties of the component media. (3) Conventionally, buried holes are thought to stay empty during generally unsaturated soil-water flow. The hole, however, acts as an obstacle to flow so that water may seep through it. The larger the hole the more likely this will happen. (4) Dispersion in heterogeneous porous systems with no maximum scale of variation is explored using a Lagrangian mode of analysis. (5) Comments are offered on ‘geostatistics’ and its application to heterogeneous soils and aquifers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208041
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 42
    Electronic Resource
    Electronic Resource
    Advective and dispersive mixing in stratified formations (1995)
    Springer
    Transport in porous media 18 (1995), S. 231-243 
    Details
    ISSN: 1573-1634
    Keywords: Stratified formations ; kinematic mixing ; dispersion ; random fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The mixing process in fluid flow is presented as the bending and stretching of material lines or filaments. A mixing exponent, which quantifies their specific rate of stretching, is defined and analyzed for the case of groundwater flow though stratified formations characterized by a Gaussian autocovariance function. The analysis is performed for purely advective mixing as well as for advective-dispersive mixing. The mixing exponent was found to be proportional to the variance of hydraulic conductivity and inversely proportional to the correlation scale of hydraulic conductivity and to the pore-level dispersion coefficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616933
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 43
    Electronic Resource
    Electronic Resource
    Scaling mixing during miscible displacement in heterogeneous porous media (1991)
    Springer
    Transport in porous media 6 (1991), S. 607-626 
    Details
    ISSN: 1573-1634
    Keywords: dispersion ; dispersivity ; heterogenity ; miscible ; porous media ; scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper discusses scaling of mixing during miscible flow in heterogeneous porous media. In large field systems dispersivity appears to depend on system length due to heterogeneities. Three types of scaling are discussed to investigate the heterogeneous effects. Dimensional analysis of mixing during flow through geometerically scaled heterogeneous models is illustrated using measured dispersion. Fractal analysis of mixing in statistically scaled heterogeneous porous media is discussed. Analog scaling of pressure transients in heterogeneous porous media is suggested as an in-situ method of estimating dispersion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00137852
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 44
    Electronic Resource
    Electronic Resource
    Modelling fluid flow in cross-bedded sections (1993)
    Springer
    Transport in porous media 12 (1993), S. 143-159 
    Details
    ISSN: 1573-1634
    Keywords: Heterogeneity ; layers ; displacement ; numerical simulation ; flow in porous media ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Beadpack experiments and numerical simulations have been carried out to study flow displacements, effluent profiles and streamline patterns for layered systems with flow not parallel to the layers. The effects of layer thickness, permeability contrast, angle of layer to flow direction, mobility ratio and flood rate have been examined. Each of these parameters influence the displacement profiles, and disperse the flood front. Such real effects must be considered when subsuming reservoir heterogeneities in average reservoir parameters in simulation studies, or interpreting core tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616977
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 45
    Electronic Resource
    Electronic Resource
    Fractal and superdiffusive transport and hydrodynamic dispersion in heterogeneous porous media (1993)
    Springer
    Transport in porous media 13 (1993), S. 3-40 
    Details
    ISSN: 1573-1634
    Keywords: Diffusion ; dispersion ; percolation ; fractals ; scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We review and discuss diffusion and hydrodynamic dispersion in a heterogeneous porous medium. Two types of heterogeneities are considered. One is percolation disorder in which a fraction of the pores do not allow transport to take place at all. In the other type, the permeabilities of various regions of the pore space are fractally distributed with long-range correlations. Both systems give rise to unusual transport in which the mean square displacement 〈r 2(t)〉 of a particle grows nonlinearly with time. Depending on the heterogeneities and the mechanism of diffusion and disperison, we may havefractal transport in which 〈r 2〉 growsslower than linearly with time, orsuperdiffusive transport in which 〈r 2〉 growsfaster than linearly with time. We show that percolation models can give rise to both types of transport with scale-dependent transport coefficients such as diffusivity and dispersion coefficients, which are consistent with many experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613269
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 46
    Electronic Resource
    Electronic Resource
    A theory of macrodispersion for the scale-up problem (1993)
    Springer
    Transport in porous media 13 (1993), S. 97-122 
    Details
    ISSN: 1573-1634
    Keywords: Scale up ; dispersion ; porous media ; random field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Dispersion is the result, observable on large length scales, of events which are random on small length scales. When the length scale on which the randomness operates is not small, relative to the observations, then classical dispersion theory fails. The scale up problem refers to situations in which randomness occurs on all length scales, and for which classical dispersion theory necessarily fails. The purpose of this article is to present non-Fickian, theories of dispersion, which do not assume a scale separation between the randomness and the observed consequences, and which do not assume a single length scale. Porous media flow properties are heterogeneous on all length scales. The geological variation on length scales below the observational length scale can be regarded as unknown and unknowable, and thus as a random variable. We develop a systematic theory relating scaling behavior of the geological heterogeneity to the scaling behavior of the fluid dispersivity. Three qualitatively distinct regimes (Fickian, non-Fickian and nonrenormalizable) are found. The theory gives consistent answers within several distinct analytic approximations, and with numerical simulation of the equations of porous media flow. Comparison to field data is made. The use of Kriging to generate constrained ensembles for conditional simulation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613272
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 47
    Electronic Resource
    Electronic Resource
    An experimental investigation of dispersion in layered porous media (1994)
    Springer
    Transport in porous media 15 (1994), S. 15-30 
    Details
    ISSN: 1573-1634
    Keywords: Experiment ; dispersion ; layered heterogeneity ; permeability ; averaging ; permutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Experiments were run in three linear, homogeneous, nonuniform porous media constructed in lucite columns using spherical glass beads. The columns were also joined end to end to create an in series layered heterogeneous porous media. Each column, all combinations of columns and several permutations were studied with a factorial experimental design to determine the effects of porosity, permeability, velocity, length, and column order upon dispersion. Attempts to predict the heterogeneous results from the homogeneous results were made, and a statistical regression based on the factorial design was calculated. Results showed that no simple averaging procedure accurately predicted the heterogeneous results. The statistical regression showed permeability, velocity, viscosity, length and column order to be significant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01046156
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 48
    Electronic Resource
    Electronic Resource
    A LGA model for dispersion in heterogeneous porous media (1994)
    Springer
    Transport in porous media 17 (1994), S. 19-32 
    Details
    ISSN: 1573-1634
    Keywords: LGA model ; heterogeneous porous media ; miscible displacement ; dispersion ; tracer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The lattice gas automaton (LGA) model proposed in the previous paper is applied to the problem of simulating dispersion and mixing in heterogeneous porous media. We demonstrate here that tracer breakthrough profiles and longitudinal dispersion coefficients can be computed for heterogeneous porous media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00624048
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 49
    Electronic Resource
    Electronic Resource
    A stream tube model for miscible flow (1995)
    Springer
    Transport in porous media 18 (1995), S. 245-261 
    Details
    ISSN: 1573-1634
    Keywords: Porous media ; miscible flow ; tracer ; dispersion ; convective flow ; stochastic ; stream tube ; continuous time random walk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A simple theoretical model is described for deriving a 1-dimensional equation for the spreading of a tracer in a steady flow at the field scale. The originality of the model is to use a stochastic appoach not in the 3-dimensional space but in the 1-D space of the stream tubes. The simplicity of calculation comes from the local relationship between permeability and velocity in a 1-D flow. The spreading of a tracer front is due to local variations in the cross-sectional area of the stream tubes, which induces randomness in travel time. The derived transport equation is averaged in the main flow direction. It differs from the standard dispersion equation. The roles of time and space variables are exchanged. This result can be explained by using the statistical theory of Continuous Time Random Walk instead of a standard Random Walk. However, the two equations are very close, since their solutions have the same first and second moments. Dispersivity is found to be equal to the product of the correlation length by the variance of the logarithm of permeability, a result similar to Gelhar's macrodispersion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616934
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 50
    Electronic Resource
    Electronic Resource
    A stream tube model for miscible flow (1995)
    Springer
    Transport in porous media 18 (1995), S. 263-282 
    Details
    ISSN: 1573-1634
    Keywords: Porous media ; dispersion ; miscible flow ; heterogeneities ; stochastic ; stream tube ; layered ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Large-scale dispersion in heterogeneous porous media is studied by using a simple model based on stochastic calculation of convective flow in a bundle of stream tubes. The advantage of this approach is that there is a local relationship between velocity and permeability in the 1-dimensional space of the stream tubes. Dispersion is due to the variation in stream tube cross-section, related to the permeability field. First, the arrival times of the tracer in the stream tubes are related to the stochastic properties of the permeability field (variance and covariance). Then, transport equations are derived from the moments of the arrival times. The results agree with more complicated studies. For a permeability field with long-range correlation, the transport equation is not unique. It depends on the assumptions involving moments higher than two. Assuming a Gaussian shape for the tracer flux leads to equations similar to the ones obtained in previous studies of time-dependent dispersivity. Without this approximation, the equation is non-local (integrodifferential) and leads to a memory effect. In the last part of this paper, the general results are illustrated with several correlation functions for the permeability field: purely random, exponential and power law covariance, and perfectly layered media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616935
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 51
    Electronic Resource
    Electronic Resource
    Experimental investigation of solute transport in large, homogeneous and heterogeneous, saturated soil columns (1995)
    Springer
    Transport in porous media 18 (1995), S. 283-302 
    Details
    ISSN: 1573-1634
    Keywords: Solute transport experiments ; heterogeneous media ; dispersion ; scale-dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Laboratory tracer experiments were conducted to investigate solute transport in 12.5-m long, horizontally placed soil columns during steady saturated water flow. Two columns having cross-sectional areas of 10×10cm2 were used: a uniformly packed homogeneous sandy column and a heterogeneous column containing layered, mixed, and lenticular formations of various shapes and sizes. The heterogeneous soil column gradually changed, on average, from coarse-textured at one end to fine-textured at the other end. NaCl breakthrough curves (BTC's) in the columns were measured with electrical conductivity probes inserted at 50- or 100-cm intervals. Observed BTC's in the homogeneous sandy column were relatively smooth and sigmoidal (S-shaped), while those in the heterogeneous column were very irregular, nonsigmoidal, and exhibited extensive tailing. Effective average pore-water velocities (v eff) and dispersion coefficients (D eff) were estimated simultaneously by fitting an analytical solution of the convection-dispersion equation to the observed BTC's. Velocity variations in the heterogeneous medium were found to be much larger than those in the homogeneous sand. Values of the dispersivity,α=D eff/v eff, for the homogeneous sandy column ranged from 0.1 to 5.0 cm, while those for the heterogeneous column were as high as 200cm. The dispersivity for transport in both columns increased with travel distance or travel time, thus exhibiting scale-dependency. The heterogeneous soil column also showed the effects of preferential flow, i.e., some locations in the column showed earlier solute breakthrough than several locations closer to the inlet boundary. Spatial fluctuations in the dispersivity could be explained qualitatively by the particular makeup of the heterogeneities in the column.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616936
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 52
    Electronic Resource
    Electronic Resource
    Dispersion in consolidated sandstone with radial flow (1995)
    Springer
    Transport in porous media 19 (1995), S. 37-66 
    Details
    ISSN: 1573-1634
    Keywords: dispersion ; sandstone ; radial flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper presents some experimental and theoretical results for dispersion processes occurring in consolidated Berea sandstone with radial flow geometry. A comprehensive review of the derivation and application of several analytical solutions is also presented. The Galerkin finite element method is applied to solve the advection-dispersion equation for unidimensional radial flow. Individual and combined effects of mechanical dispersion and molecular diffusion are examined using velocity-dependent dispersion models. Comparison of simulated results with experimental data is made. The effect of flow rates is examined. The results suggest that a linear dispersion model,D=αu, whereD is the dispersion coefficient,u the velocity andα a constant, is not a good approximation despite its wide acceptance in the literature. The most suitable mathematical formulation is given by an empirical form of $$D = D_0 + \mathop \alpha \limits^` u^m$$ , whereD ois the molecular diffusion coefficient. For the range of Péclet number (Pe=vd/D m,wherev is the characteristic velocity,d the characteristic length andD mthe molecular diffusion coefficient in porous media) examined (Pe=0.5 to 285), a power constant ofm=1.2 is obtained which agrees with the value reported by some other workers for the same regime. From the results of experiments and numerical modelling, the effect of mobility ratios (defined as the ration of viscosities of displaced and displacing fluids) on dispersion is found to be negligible, provided that the ratio is favourable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00716048
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 53
    Electronic Resource
    Electronic Resource
    Dispersion and Attenuation of Surface Waves in a Fluid-Saturated Porous Medium (1997)
    Springer
    Transport in porous media 29 (1997), S. 207-223 
    Details
    ISSN: 1573-1634
    Keywords: dispersion ; attenuation ; surface waves ; Rayleigh wave ; Love wave
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An investigation is conducted of propagation of surface waves in a porous medium consisting of a microscopically incompressible solid skeleton in which a microscopically incompressible liquid flows within the interconnected pores, and particularly the case where the solid skeleton deforms linear elastically. The frequency equations of Rayleigh- and Love-type waves are derived relating the dependence of wave numbers, being complex quantities, on frequency, as a result those waves are dispersive as well as inhomogeneous. Nevertheless, the amplitudes of both surface waves attenuate along the surface of the porous medium, whereas they decay exponentially receding from the surface of the medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006590119031
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 54
    Electronic Resource
    Electronic Resource
    Experiments on Solute Transport in Aggregated Porous Media: Are Diffusions Within Aggregates and Hydrodynamic Dispersion Independent? (1997)
    Springer
    Transport in porous media 29 (1997), S. 281-307 
    Details
    ISSN: 1573-1634
    Keywords: solute transport ; nonequilibrium ; heterogeneous porous media ; dispersion ; diffusion ; experiments ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Two region models for solute transport in porous media assume that hydrodynamic dispersion in mobile water and solute diffusion within immobile water regions are independent. Experimental and theoretical results for transport through a macropore indicate that hydrodynamic dispersion and solute exchange are interdependent. Experiments were carried out to investigate this problem for a column packed with spherical porous aggregates. The effective diffusion coefficient of a tracer within the agreggates was determined from specific experiments. The dispersivity of the bed was determined from experiments carried out with a column filled with nonporous beads. We took advantage of the dependence of hydrodynamic dispersion on density ratios between the invading and displaced solutions to obtain a set of breakthrough curves corresponding to situations where the diffusion coefficient remains constant, whereas the dispersivity varies. Simulations reproduce correctly the experiments. Small discrepancies are noted that can be corrected either by increasing the dispersion coefficient or by fitting the external mass transfer coefficient. Increased dispersion coefficients probably reveal a modification of Taylor dispersion due to solute exchange. The fitted external mass transfer coefficients are close to the values obtained with classical correlations of the chemical engineering literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006513725029
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 55
    Electronic Resource
    Electronic Resource
    Stability of vertical miscible displacements with developing density and viscosity gradients (1988)
    Springer
    Transport in porous media 3 (1988), S. 277-297 
    Details
    ISSN: 1573-1634
    Keywords: Stability ; linear stability analysis ; miscible displacement ; aspect ratio ; mobility control ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Viscous fingering and gravity tonguing are the consequences of an unstable miscible displacement. Chang and Slattery (1986) performed a linear stability analysis for a miscible displacement considering only the effect of viscosity. Here the effect of gravity is included as well for either a step change or a graduated change in concentration at the injection face during a downward, vertical displacement. If both the mobility ratio and the density ratio are favorable (the viscosity of the displacing fluid is greater than the viscosity of the displaced fluid and, for a downward vertical displacement, the density of the displacing fluid is less than the density of the displaced fluid), the displacement will be stable. If either the mobility ratio or the density ratio is unfavorable, instabilities can form at the injection boundary as the result of infinitesimal perturbations. But if the concentration is changed sufficiently slowly with time at the entrance to the system, the displacement can be stabilized, even if both the mobility ratio and the density ratio are unfavorable. A displacement is more likely to be stable as the aspect ratio (ratio of thickness to width, which is assumed to be less than one) is increased. Commonly the laboratory tests supporting a field trial use nearly the same fluids, porous media, and displacement rates as the field trial they are intended to support. For the laboratory test, the aspect ratio may be the order of one; for the field trial, it may be two orders of magnitude smaller. This means that a laboratory test could indicate that a displacement was stable, while an unstable displacement may be observed in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235332
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 56
    Electronic Resource
    Electronic Resource
    An analysis of the viability of polymer flooding as an enhanced oil recovery technology (1988)
    Springer
    Transport in porous media 3 (1988), S. 591-618 
    Details
    ISSN: 1573-1634
    Keywords: Polymer flooding ; viscous fingering ; multiphase flow ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The concept of improving oil recovery through polymer flooding is analysed. It is shown that while the injection of a polymer solution improves reservoir conformance, this beneficial effect ceases as soon as one attempts to push the polymer solution with water. Once water injection begins, the water quickly passes through the polymer creating a path along which all future injected water flows. Thus, the volume of the polymer slug is important to the process and an efficient recovery would require that the vast majority of the reservoir be flooded by polymer. It is also shown that the concept of grading a polymer slug to match the mobilities of the fluids at the leading and trailing edges of a polymer slug does not work in a petroleum reservoir. While this process can supply some additional stability to the slug, it is shown that for the purposes of enhanced oil recovery this additional stability is not great enough to be of any practical use. It is found that in this case the instability has simply been hidden in the interior of the slug and causes the same sort of instability to occur as was the case for the uniform slug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00959104
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 57
    Electronic Resource
    Electronic Resource
    Tracer Dispersion in Rough Open Cracks (1998)
    Springer
    Transport in porous media 32 (1998), S. 97-116 
    Details
    ISSN: 1573-1634
    Keywords: dispersion ; anomalous diffusion ; Taylor dispersion ; roughness ; self-affine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Tracer dispersion is studied in an open crack where the two rough crack faces have been translated with respect to each other. The different dispersion regimes encountered in rough-wall Hele-Shaw cell are first introduced, and the geometric dispersion regime in the case of self-affine crack surfaces is treated in detail through perturbation analysis. It is shown that a line of tracer is progressively wrinkled into a self-affine curve with an exponent equal to that of the crack surface. This leads to a global dispersion coefficient which depends on the distance from the tracer inlet, but which is still proportional to the mean advection velocity. Besides, the tracer front is subjected to a local dispersion (as could be revealed by point measurements or echo experiments) very different from the global one. The expression of this anomalous local dispersion coefficient is also obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006553902753
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 58
    Electronic Resource
    Electronic Resource
    Automaton Simulations of Dispersion in Porous Media (1998)
    Springer
    Transport in porous media 32 (1998), S. 187-198 
    Details
    ISSN: 1573-1634
    Keywords: diffusion ; dispersion ; miscible ; automaton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A thermodynamic lattice gas (automaton) model is used to simulate dispersion in porous media. Simulations are constructed at two distinctly different scales, the pore scale at which capillary models are constructed and large scale or Darcy scale at which probabilistic collision rules are introduced. Both models allow for macroscopic (pore scale) phase separation. The pore scale models clearly show the effect of pore structure on dispersion. The large scale (mega scale) simulations indicate that when the pressure difference between the displacing phase and displaced phase is properly chosen (representing the average pressure gradient between the phases). The simulation results are consistent with both theoretical predictions and experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006566117582
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 59
    Electronic Resource
    Electronic Resource
    Stochastic-Perturbation Analysis of a One-Dimensional Dispersion-Reaction Equation: Effects of Spatially-Varying Reaction Rates (1998)
    Springer
    Transport in porous media 32 (1998), S. 139-161 
    Details
    ISSN: 1573-1634
    Keywords: dispersion ; reaction ; perturbation theory ; stochastic modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We carry out a stochastic-perturbation analysis of a one-dimensional convection–dispersion-reaction equation for reversible first-order reactions. The Damköhler number, Da, is distributed randomly from a distribution that has an exponentially decaying correlation function, controlled by a correlation length, ξ. Zeroth- and first-order approximations of the dispersion coefficient, D are computed from moments of the residence-time distribution obtained by solving a one-dimensional network model, in which each unit of the network represents a Darcy-level transport unit, and the solution of the transfer function in zeroth- and first-order approximations of the transport equation. In the zeroth-order approximation, the dispersion coefficient is calculated using the convection–dispersion-reaction equation with constant parameters, that is, perturbation corrections to the local equation are ignored. This zeroth-order dispersion coefficient is a linear function of the variance of the Damköhler number, 〈(ΔDa)2〉. A similar result was reported in a two-dimensional network simulation. The zeroth-order approximation does not give accurate predictions of mixing or spreading of a plume when Damköhler numbers, Da ≪ 1 and its variance, 〈(ΔDa)2〉 〉 0.25 〈Da2〉. On the other hand, the first-order theory leads to a dispersion coefficient that is independent of the reaction parameters and to equations that do accurately predict mixing and spreading for Damköhler numbers and variances in the range √〈(ΔDa)2〉/〈Da〉≤0.3
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006575527731
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 60
    Electronic Resource
    Electronic Resource
    On the Modelling of Generalized Taylor–Aris Dispersion in Chromatographs via Multiple Scales Expansions (1999)
    Springer
    Transport in porous media 36 (1999), S. 307-339 
    Details
    ISSN: 1573-1634
    Keywords: dispersion ; chromatography ; porous media ; adsorption ; homogenization ; multiple scales expansions.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper is devoted to the computation of effective equations for the transport of a solute in a chromatograph. We focus our attention on models that retain dispersion effects. A chromatograph is a biporous periodic heterogeneous medium, made up of macropores, and of small porous adsorbing crystals that have a retention effect on the solute. We use the method of multiple scales expansions. Various macroscopic behaviours appear, according to the respective orders of magnitude of the dimensionless characteristic parameters: Peclet number in the macropores, ratio of the characteristic time of diffusion in the macropores to the characteristic time of diffusion in the crystals, adsorption coefficient. Dispersion occurs for a Peclet number of order ε−1. We then discuss the effective behaviour of the solute, with respect to the orders of magnitude of the other characteristic parameters. To our knowledge, most of the models are new. Our modelling is not restricted to chromatographs. It applies to various situations of physic and chemical engineering: fixed bed reactors, catalytic cracking, ground water for instance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006654621514
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 61
    Electronic Resource
    Electronic Resource
    Experimental Investigation of Mixing in Aperiodic Heterogeneous Porous Media: Comparison with Stochastic Transport Theory (1999)
    Springer
    Transport in porous media 37 (1999), S. 169-182 
    Details
    ISSN: 1573-1634
    Keywords: experiment ; aperiodic heterogeneity ; dispersion ; stochastic modeling.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An electrochemical technique was used to measure concentration distributions in an aperiodic heterogeneous model for comparison with a stochastic transport theory. Four identical columns, each filled with a homogeneous distribution of glass beads, were threaded together to create a single model with aperiodic heterogeneity. The layers in the model were arranged in different ways providing 24 realizations of the permeability distribution. Comparisons between experimental moment data and moments of simulated mean concentration distributions showed that the model was not able to accurately predict experimentally observed mixing behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006602620606
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 62
    Electronic Resource
    Electronic Resource
    Sparging and agitation-induced injury of cultured animals cells: Do cell-to-bubble interactions in the bulk liquid injure cells? (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 399-409 
    Details
    ISSN: 0006-3592
    Keywords: cell damage ; cell culture ; bubble aeration ; agitation ; bubble coalescence and breakup ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has been established that the forces resulting from bubbles rupturing at the free air (gas)/liquid surface injure animal cells in agitated and/or sparged bioreactors. Although it has been suggested that bubble coalescence and breakup within agitated and sparged bioreactors (i.e., away from the free liquid surface) can be a source of cell injury as well, the evidence has been indirect. We have carried out experiments to examine this issue. The free air/liquid surface in a sparged and agitated bioractor was eliminated by completely filling the 2-L reactor and allowing sparged bubbles to escape through an outlet tube. Two identical bioreactors were run in parallel to make comparisons between cultures that were oxygenated via direct air sparging and the control culture in which silicone tubing was used for bubble-free oxygenation. Thus, cell damage from cell-to-bubble interactions due to processes (bubble coalescence and breakup) occurring in the bulk liquid could be isolated by eliminating damage due to bubbles rupturing at the free air/liquid surface of the bioreactor. We found that Chinese hamster ovary (CHO) cells grown in medium that does not contain shear-protecting additives can be agitated at rates up to 600 rpm without being damaged extensively by cell-to bubble interactions in the bulk of the bioreactor. We verified this using both batch and high-density perfusion cultures. We tested two impeller designs (pitched blade and Rushton) and found them not to affect cell damage under similar operational conditions. Sparger location (above vs. below the impeller) had no effect on cell damage at higher agitation rates but may affect the injury process at lower agitation intensities (here, below 250 rpm). In the absence of a headspace, we found less cell damage at higher agitation intensities (400 and 600 rpm), and we suggest that this nonintuitive finding derives from the important effect of bubble size and foam stability on the cell damage process. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 63
    Electronic Resource
    Electronic Resource
    Initial culture conditions affect the sensitivity of HepG2 cells to excessive mechanical agitation (1989)
    Springer
    Cytotechnology 2 (1989), S. 135-140 
    Details
    ISSN: 1573-0778
    Keywords: hepatoma ; cell culture ; microcarrier ; agitation rate ; cell inoculation density ; growth rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hepatoma cells, HepG2, grew normally on microcarriers even at a relatively high agitation rate if sufficient time was allowed for cell attachment and adhesion. However, if a high agitation rate was applied shortly after initial cell attachment, the growth rate was retarded. This sensitivity to mechanical agitation appears to be dependent on the inoculation cell density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386146
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 64
    Electronic Resource
    Electronic Resource
    Bcl-2 inhibits apoptosis and extends recombinant protein production in cells infected with Sindbis viral vectors (1996)
    Springer
    Cytotechnology 22 (1996), S. 169-178 
    Details
    ISSN: 1573-0778
    Keywords: apoptosis ; bcl-2 ; cell culture ; chloramphenicol acetyltransferase ; recombinant protein ; Sindbis virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Viruses carrying foreign genes are often used for the production of recombinant proteins in mammalian cells and other eukaryotic expression systems. Though high levels of gene expression are possible using viral vectors, the host cell generally responds to the infection by inducing apoptotic cell death within several days, abruptly ending protein production. It has recently been demonstrated, however, that apoptosis can be suppressed in virally infected cells using anti-apoptotic genes, such as bcl-2. In this study, stably transfected rat carcinomal cell lines, AT3-bcl2 and AT3-neo, were infected with a Sindbis virus carrying the gene for chloramphenicol acetyltransferase (CAT) in an effort to determine the effect of bcl-2 on cell viability and recombinant protein production. Infected AT3-bcl2 cells consistently maintained viabilities close to 100% and a growth rate equivalent to that of uninfected cells (0.040 h-1). In contrast, the Sindbis viral vector induced apoptosis in the AT3-neo cells, which were all dead by three days post-infection. Though infected AT3-neo cells generated higher levels of heterologous protein, over 1000 mUnits per well, CAT activity fell to zero by two days post-infection. In contrast, chloramphenicol acetyltransferase was present in AT3-bcl2 cells for almost a week, reaching a maximum level of 580 mUnits per well. In addition, recombinant protein production in AT3-bcl2 cells was extended and amplified by the regular addition of virus to the culture medium, a process which resulted in expression for the duration of the cell culture process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353936
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 65
    Electronic Resource
    Electronic Resource
    The growth and phenotypic expression of human osteoblasts (1996)
    Springer
    Cytotechnology 22 (1996), S. 263-267 
    Details
    ISSN: 1573-0778
    Keywords: biodegradable ; bone regeneration ; cell culture ; human cell osteoblasts ; polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The care of patients with a skeletal deficiency currently involves the use of bone graft or a non-biologic material such as a metal or polymer. There are alternate possibilities in development which involve the growth of bone cells (osteoblasts) on degradable polymer scaffolds. These tissue engineering strategies require production of the polymeric scaffold, cellular harvest followed by either ex vivo or in vivo growth of the cells on the scaffold, and exploration of the interaction between the cell and scaffold. Research into these strategies utilizes cells from a variety of species, but clinical applications will likely require human osteoblasts. This study explores the process whereby human osteoblasts are harvested under sterile conditions during joint replacement surgery from normally discarded cancellous bone, transported from the operating room to the lab, and grown in culture. This process is feasible, and the cells express their phenotype via the production of alkaline phosphatase and collagen in culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353947
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 66
    Electronic Resource
    Electronic Resource
    Chinese hamster ovary cells produce sufficient recombinant insulin-like growth factor I to support growth in serum-free medium. Serum-free growth of IGF-I-producing CHO cells (1997)
    Springer
    Cytotechnology 24 (1997), S. 55-64 
    Details
    ISSN: 1573-0778
    Keywords: CHO ; IGF-I ; serum-free ; autocrine growth ; cell culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Insulin-like growth factor I has similar mitogenic effects to insulin, a growth factor required by most cells in culture, and it can replace insulin in serum-free formulations for some cells. Chinese Hamster Ovary cells grow well in serum-free medium with insulin and transferrin as the only exogenous growth factors. An alternative approach to addition of exogenous growth factors to serum-free medium is transfection of host cells with growth factor-encoding genes, permitting autocrine growth. Taking this approach, we constructed an IGF-I heterologous gene driven by the cytomegalovirus promoter, introduced it into Chinese Hamster Ovary cells and examined the growth characteristics of Insulin-like growth factor I-expressing clonal cells in the absence of the exogenous factor. The transfected cells secreted up to 500 ng/106 cells/day of mature Insulin-like growth factor I into the conditioned medium and as a result they grew autonomously in serum-free medium containing transferrin as the only added growth factor. This growth-stimulating effect, observed under both small and large scale culture conditions, was maximal since no further improvement was observed in the presence of exogenous insulin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007969502256
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 67
    Electronic Resource
    Electronic Resource
    A novel acid proteinase relased by hybridoma cells (1990)
    Springer
    Cytotechnology 3 (1990), S. 157-169 
    Details
    ISSN: 1573-0778
    Keywords: acid proteinase ; cell culture ; hybridoma ; immunoglobulin cleavage ; lysosomal proteinases ; recycling reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An acid proteinase has been detected in culture supernate of the 9.2.27 murine hybridoma. This enzyme extensively degrades albumin and transferrin during short incubations at pH 3 and below. Limited proteolysis of the 9.2.27 IgG2a appears to occur in the culture supernate. Proteolysis is enhanced at low pH in the presence of urea or 1 M acetic acid. The proteinase activity accumulates in continuous perfusion, total cell recycle cultures, beginning during exponential growth of the hybridoma. It is destroyed by boiling and blocked by pepstatin, but not by inhibitors of cysteine or serine proteinases or by EDTA. The low pH optimum may distinguish this enzyme from the known rat and mouse aspartic acid proteinases including cathepsin D and cathepsin E.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00143678
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 68
    Electronic Resource
    Electronic Resource
    A simple and rapid reverse transcriptase assay for the detection of retroviruses in cell cultures (1999)
    Springer
    Cytotechnology 29 (1999), S. 221-227 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; polymerase chain reaction ; retrovirus ; reverse transcriptase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Reverse transcriptase (RT) is a good diagnostic tool for the detection of retroviruses. We have developed a simple and rapid assay for RT activity in culture supernatants. A 370-base RNA sequence from the tetracycline-resistance gene in pBR322 plasmid DNA was used as a template for RT-mediated cDNA synthesis. To detect the resultant cDNA, we used the nested polymerase chain reaction. A sensitivity test using purified recombinant RT of human immunodeficiency virus type 1 demonstrated that the detection limit of this method was 10-7–10-8 units of RT activity in 20 μl of a test sample (2 × 10-9–2 × 10-10 units ml-1). This method detected RT activity in unconcentrated supernatants of cell cultures infected with human T-cell leukemia virus, Moloney murine leukemia virus, Moloney murine sarcoma virus, or Rous sarcoma virus. This nonisotopic method provides results within 10 h and is useful for quality control to detect retroviruses in cell cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008000210125
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 69
    Electronic Resource
    Electronic Resource
    A new culture system for the cultivation of mammalian cells for the production of several biologically active substances (1993)
    Springer
    Cytotechnology 13 (1993), S. 143-148 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; cell culture apparatus ; dialysis membrane ; perfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We recently developed a new dialysis culture system (termed LIFROC-device) for the cultivation of lymphokine-activated killer cells (Murataet al., 1990, 1991). In the present study, we applied the LIFROC-device (400 ml culture vessel) to the cultivation of mammalian cells for the production of biologically active substances. We cultured mouse-mouse hybridoma TP-709, secreting anti-tissue plasminogen activator (tPA) monoclonal antibody (mAb), recombinant CHO GT19, secreting hGH, and human melanoma Bowes cells, secreting tPA. With the LIFROC-device, TP-709 grew to a maximal cell density of 3.8×106 cells/ml and and produced 480 μg/ml (192 mg in total) of mAb. GT19 reached a cell density of 2.2×106 cells/ml and produced 302 μg/ml (120 mg in total) of hGH. Bowes cells expanded to 4.4×106 cells/ml and secreted 8.5 μg/ml (3.3 mg in total) of tPA. The protein concentration in the culture broths of the LIFROC-device became 7–200 times higher than that of batch culture. Thus, the LIFROC-device can be applied to protein production as well as cell growth with high efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749941
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 70
    Electronic Resource
    Electronic Resource
    Growing colorectal tumors: minimizing microbial and stromal competition and assessing in vitro selection pressures (2000)
    Springer
    Cytotechnology 34 (2000), S. 205-211 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; colorectal cancer ; microbial contamination ; stroma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Development of primary colorectal cancer cell lines ishampered by contamination from regional microbes, overgrowthof stromal cells, and purported genetic drift from selectionpressures in vitro. We initiated 32 primaryadenocarcinomas, 3 recurrences and 6 distant metastases incell culture. Twelve cell lines from eleven tumors weregenerated (26.8%) overall. Nine of 32 primary tumorsyielded 10 cell lines, 5 were lost to contamination, 13 wereoverwhelmed by stromal cells, and 5 demonstrated no growth.Addition of isobutyl methyl xanthine (IBMX) to culturelimited fibroblastoid growth. There was no associationbetween tumor location (p = 0.535, mid-P), degree ofdifferentiation (p = 0.850, mid-P) or clinicopathologic stage(p = 0.400, mid-P), and the ability of cells to becomeestablished in culture. The majority of cell lines hadsimilar nuclear DNA content and expression of cell-surfaceantigens compared with their parent tumors. Microbialcontamination and stromal cell overgrowth present thegreatest obstacle to capturing a representative bank ofcolon tumors in vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008131428992
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 71
    Electronic Resource
    Electronic Resource
    Nutrient optimization for high density biological production applications (1991)
    Springer
    Cytotechnology 5 (1991), S. 15-30 
    Details
    ISSN: 1573-0778
    Keywords: high density ; cell culture ; serum-free medium ; hybridoma ; CHO cells ; virus production ; insect cells ; adoptive immunotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conclusion At the 1989 annual meeting of the U.S. Tissue Culture Associations, Ricahrd am, a leading investigator in the serum-free nutrient requirements of cultured cells, commented on the process of medium development. He noted that a survey of major media manufacturers revealed that, among the top selling mammalian cell culture media formulations, most were nearly thirty years old. This commentary is noteworthy considering the tremendous changes in cell culture understanding and derived applications which have emerged over these three decades. Fastidious cell types relatively unknown to investigators of the 1950s and 1960s are now being cultivated in defined, serum-free environments. Culture environments range from limiting dilution clonal recoveries to maintenance cultures approaching tissue densities. While research applications continue to predominate, applications of cell culture have expanded to the engineered production of biopharmaceuticals, to replacement of animal models for toxicology testing, and to the preservation, activation and expansion of human cells, tissues and organs. It is likely that future nutrient medium development will be predicated upon the design of a minimal number of defined formulations of relatively generic utility to a broad class of cell types. Analytical techniques derived from those described herein will be exploited in the user laboratory and in collaboration with the supplier to optimize the nutrient composition for the desired biological response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365531
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 72
    Electronic Resource
    Electronic Resource
    Discrimination of normal and transformed cells in vitro by cytologic and morphologic analysis (1989)
    Springer
    Cytotechnology 2 (1989), S. 187-201 
    Details
    ISSN: 1573-0778
    Keywords: bronchus ; cell culture ; cytology ; morphometry ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Malignant A-549 lung carcinoma and adenovirus-12 SV40 hybrid virus transformed non-tumorigenic human bronchial epithelial cells (BEAS-2B) were objectively discriminated from normal bronchial epithelial (BE) cells on the basis of Papanicolaou stained nuclear features (e.g. shape, chromatin texture, hyperchromasia) and nucleolar morphology (e.g. number per cell, irregular contours). Morphometric analysis indicated that significant differences in cellular morphology existed between BE, BEAS-2B, and A-549 cells. Similar analyses of transformed, tumorigenic cell lines demonstrated that nuclear features (i.e., chromatin texture, clearing of parachromatin, hyperchromasia, variation in thickness of the nuclear envelope, sharp indentations in the nuclear envelope), and nucleolar features (i.e., degree of roundness, presence of angular projections, number per cell) discriminated chemically and virally transformed cells from spontaneously transformed cells. Nuclear and nucleolar features were correlated with the growth rate of tumorigenic cell lines. These analytical approaches will be helpful in studies of the effects of various factors (e.g. vitamin A, phorbol ester, oncogene transfection) on cellular proliferation and/or differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00133244
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 73
    Electronic Resource
    Electronic Resource
    Processing of mutated human proinsulin to mature insulin in the non-endocrine cell line, CHO (1996)
    Springer
    Cytotechnology 21 (1996), S. 279-288 
    Details
    ISSN: 1573-0778
    Keywords: proinsulin processing ; CHO ; mutant human proinsulin ; cell culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Heterologous genes encoding proproteins, including proinsulin, generally produce mature protein when expressed in endocrine cells while unprocessed or partially processed protein is produced in non-endocrine cells. Proproteins, which are normally processed in the regulated pathway restricted to endocrine cells, do not always contain the recognition sequence for cleavage by furin, the endoprotease specific to the constitutive pathway, the principal protein processing pathway in non-endocrine cells. Human proinsulin consists of B-Chain — C-peptide — A-Chain and cleavage at the B/C and C/A junctions is required for processing. The B/C, but not the C/A junction, is recognised and cleaved in the constitutive pathway. We expressed a human proinsulin and a mutated proinsulin gene with an engineered furin recognition sequence at the C/A junction and compared the processing efficiency of the mutant and native proinsulin in Chinese Hamster Ovary cells. The processing efficiency of the mutant proinsulin was 56% relative to 0.7% for native proinsulin. However, despite similar levels of mRNA being expressed in both cell lines, the absolute levels of immunoreactive insulin, normalized against mRNA levels, were 18-fold lower in the mutant proinsulin-expressing cells. As a result, there was only a marginal increase in absolute levels of insulin produced by these cells. This unexpected finding may result from preferential degradation of insulin in non-endocrine cells which lack the protection offered by the secretory granules found in endocrine cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365350
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 74
    Electronic Resource
    Electronic Resource
    Disposable bioreactor for cell culture using wave-induced agitation (1999)
    Springer
    Cytotechnology 30 (1999), S. 149-158 
    Details
    ISSN: 1573-0778
    Keywords: bioreactor ; cell culture ; disposable ; wave agitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This work describes a novel bioreactor system for the cultivation of animal, insect, and plant cells using wave agitation induced by a rocking motion. This agitation system provides good nutrient distribution, off-bottom suspension, and excellent oxygen transfer without damaging fluid shear or gas bubbles. Unlike other cell culture systems, such as spinners, hollow-fiber bioreactors, and roller bottles, scale-up is simple, and has been demonstrated up to 100 L of culture volume. The bioreactor is disposable, and therefore requires no cleaning or sterilization. Additions and sampling are possible without the need for a laminar flow cabinet. The unit can be placed in an incubator requiring minimal instrumentation. These features dramatically lower the purchase cost, and operating expenses of this laboratory/pilot scale cell cultivation system. Results are presented for various model systems: 1) recombinant NS0 cells in suspension; 2) adenovirus production using human 293 cells in suspension; 3) Sf9 insect cell/baculovirus system; and 4) human 293 cells on microcarrier. These examples show the general suitability of the system for cells in suspension, anchorage-dependent culture, and virus production in research and GMP applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008025016272
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 75
    Electronic Resource
    Electronic Resource
    Enhanced CEA production associated with aspirin in a culture of CW-2 cells on some polymeric films (1999)
    Springer
    Cytotechnology 31 (1999), S. 233-242 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; carcinoembryonic antigen ; aspirin ; enhanced production ; Langmuir-Blodgett film
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Human colorectal adenocarcinoma tumor (CW2) cells were cultivated in RPMI 1640 media containing 0–7.5 mM aspirin and 10% fetal bovine serum for the production of carcinoembryonic antigen (CEA). By adding aspirin to the media, the production of CEA per cell increased by up to one hundred fold compared to cultivation in normal media containing no aspirin, even though the total cell concentration decreased with the increase in aspirin in the media. The production of CEA was also investigated for CW2 cells cultured on silk fibroin, poly(γ-benzyl-L-glutamate) and poly(γ-benzyl-L-glutamate)/poly(ethylene oxide) diblock copolymer films prepared by the Langmuir-Blodgett and casting methods. The highest production of CEA per cell was observed for the CW2 cells on poly(γ-benzyl-L-glutamate) and its diblock copolymer films prepared by the Langmuir-Blodgett method in the medium containing 5 mM aspirin after 168 hr of inoculation. This originates from the fact that the cell density on the films in the medium containing 5 mM aspirin was the lowest under these conditions. It is suggested that CW2 cells produce CEA more effectively when the cell growth is suppressed by addition of toxic chemicals such as aspirin or by culture on unfavorable films for cell growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008030730814
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 76
    Electronic Resource
    Electronic Resource
    Comparison of cell growth in T-flasks, in micro hollow fiber bioreactors, and in an industrial scale hollow fiber bioreactor system (2000)
    Springer
    Cytotechnology 34 (2000), S. 111-119 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; hollow fiber bioreactor ; hybridoma ; micro bioreactor ; optimization ; T-flask
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In this article, cell growth in a novel micro hollow fiberbioreactor was compared to that in a T-flask and theAcuSyst-Maximizer®, a large scale industrial hollowfiber bioreactor system. In T-flasks, there was relativelylittle difference in the growth rates of one murine hybridomacultured in three different media and for three other murinehybridomas cultured in one medium. However, substantialdifferences were seen in the growth rates of cells in themicro bioreactor under these same conditions. These differencecorrelated well with the corresponding rates of initial cellexpansion in the Maximizer. Quantitative prediction of thesteady-state antibody production rate in the Maximizer was moreproblematic. However, conditions which lead to faster initialcell growth and higher viable cell densities in the microbioreactor correlated with better performance of a cell line inthe Maximizer. These results demonstrate that the microbioreactor is more useful than a T-flask for determining optimalconditions for cell growth in a large scale hollow fiberbioreactor system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008167713696
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 77
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 78
    Electronic Resource
    Electronic Resource
    3-Amino-6-methoxy-9-(2-hydroxyethylamino) acridine: A new fluorescent dye to detect mycoplasma contamination in cell cultures (1990)
    Springer
    Cytotechnology 4 (1990), S. 191-194 
    Details
    ISSN: 1573-0778
    Keywords: acridine derivative ; cell culture ; fluorescence microscopy ; mycoplasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A new fluorescent acridine orange derivative, 3-amino-6-methoxy-9-(2-hydroxyethylamino) acridine (AMHA), has been applied to Hela cells in order to set up appropriate conditions for the detection of mycoplasma contaminations. Since AMHA staining reveals intensely fluorescent nuclei and slight fluorescent cytoplasm, we can visualize and localize mycoplasma contamination on each cell. In combination with a shortened Chen's staining method (1977), AMHA should allow a better detection of mycoplasma in animal cell cultures than the well established Hoechst dye.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365100
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 79
    Electronic Resource
    Electronic Resource
    Growth and protein production kinetics of a murine myeloma cell line transfected with the human growth hormone gene (1991)
    Springer
    Cytotechnology 5 (1991), S. 223-231 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; kinetics ; Ig promoter/enhancer ; plasmacytoma ; recombinant protein production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A model mammalian cell system for the production of recombinant proteins was investigated. Murine myeloma cells which had lost the ability to produce both heavy and light chain immunoglobulin molecules were transfected with a vector containing the immunoglobulin heavy chain promoter and enhancer elements linked to the human growth hormone gene. The growth kinetics of G32, a clonal isolate, were found to be similar to both the parent myeloma and hybridomas. However, production of hGH by G32 was growth associated, rather than as a secondary metabolite as is the case for hybridomas. In addition, G32 produced hGH at molar levels greater than most hybridomas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00556292
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 80
    Electronic Resource
    Electronic Resource
    Primary cell culture from embryos of the Japanese scallop Mizuchopecten yessoensis (Bivalvia) (1991)
    Springer
    Cytotechnology 6 (1991), S. 49-54 
    Details
    ISSN: 1573-0778
    Keywords: Bivalvia ; cell culture ; embryo ; mitosis ; scallop
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Primary cell cultures obtained from embryos of Mizuchopecten yessoensis (Bivalvia) survived for four months. Although the number of cells progressively decreased during the cultivation, mitotic cells were observed both at the first stages and at the end. A possibility of growing marine invertebrates cells in long term primary culture is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353702
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 81
    Electronic Resource
    Electronic Resource
    Characterization of endosteal osteoblasts isolated from human maxilla and mandible: An experimental system for biocompatibility tests (1991)
    Springer
    Cytotechnology 7 (1991), S. 39-48 
    Details
    ISSN: 1573-0778
    Keywords: cell culture ; endosteal human osteoblasts ; maxilla ; mandible ; titanium ; biocompatibility ; alkaline phosphatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Fragments of cancellous and cortical bone from human maxilla and mandible were cultured by the explant technique. Cells isolated by trypsinization of primary cultures were characterized as osteoblasts on the basis of intracellular alkaline phosphatase activity, the constituents of the extracellular matrix, and response to human parathormone (PTH). In culture, the osteoblasts often gave rise to superposed clumps of large cells whose cytoplasm contained endoplasmic reticulum, numerous mitochondria, vacuoles, and a dense network of intermediate filaments, often at the level of the plasma membrane. In the presence of vitamin C and 1,25-dihydroxyvitamin D3, the osteoblasts produced an extracellular matrix composed of collagen type I and various non-collagenous proteins, including osteocalcin. Biochemical test results were comparable to those reported for osteoblasts of other origins (rat calvaria, human iliac crest), and namely elevated intracellular alkaline phosphatase activity and cAMP accumulation in response to stimulation by human PTH (1–34). Osteoblasts isolated in this manner were cultured in the presence of pure titanium disks to determine the effects of exposure to this metal. Electron microscopy revealed few significant differences in cell growth and specific enzyme activity compared to control osteoblasts grown on plastic dishes, reflecting the excellent biologic and biochemical relationship between the osteoblasts and pure titanium. This experimental system thus appears suitable for biocompatibility studies, and in particular, evaluation of dental implants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00135637
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 82
    Electronic Resource
    Electronic Resource
    Influence of the viscoelastic properties of the respiratory system on the energetically optimum breathing frequency (1993)
    Springer
    Annals of biomedical engineering 21 (1993), S. 489-499 
    Details
    ISSN: 1573-9686
    Keywords: Work of breathing ; Inspiratory pressure-time integral ; Respiratory modeling ; Dogs ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract We hypothesized that the viscoelastic properties of the respiratory system should have significant implications for the energetically optimal frequency of breathing, in view of the fact that these properties cause marked dependencies of overall system resistance and elastance on frequency. To test our hypothesis we simulated two models of canine and human respiratory system mechanics during sinusoidal breathing and calculated the inspiratory work ( $$\dot W$$ ) and pressure-time integral (PTI) per minute under both resting and exercise conditions. The two models were a two-compartment viscoelastic model and a single-compartment model. Requiring minute alveolar ventilation to be fixed, we found that both models predicted almost identical optimum breathing frequencies. The calculated PTI was very insensitive to increases in breathing frequency above the optimal frequencies, while $$\dot W$$ was found to increase slowly with frequency above its optimum. In contrast, both $$\dot W$$ and PTI increased sharply as frequency decreased below their respective optima. A sensitivity analysis showed that the model predictions were very insensitive to the elastance and resistance values chosen to characterize tissue viscoelasticity. We conclude that the $$\dot W$$ criterion for choosing the frequency of breathing is compatible with observations in nature, whereas the optimal frequency predictions of the PTI are rather too high. Both criteria allow for a fairly wide margin of choice in frequency above the optimum values without incurring excessive additional energy expenditure. Furthermore, contrary to our expectations, the viscoelastic properties of the respiratory system tissues do not pose a noticeable problem to the respiratory controller in terms of energy expenditure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000004
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 83
    Electronic Resource
    Electronic Resource
    Preparation of conditioned medium to stimulate anthocyanin production using suspension cultures of Fragaria ananassa cells (1999)
    Springer
    World journal of microbiology and biotechnology 15 (1999), S. 635-637 
    Details
    ISSN: 1573-0972
    Keywords: Anthocyanin ; cell culture ; conditioned medium ; strawberry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A conditioned medium (CM) prepared from strawberry suspension cultures greatly stimulated anthocyanin accumulation. CM separated by dialysis membrane showed a significant increase (p 0.05) in anthocyanin synthesis at a fraction smaller than 10,000 Da. The stimulation by CM was eliminated when the CM was treated with alkali.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008946506287
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 84
    Electronic Resource
    Electronic Resource
    The multiple-scale averaging and dynamics of dispersion-managed optical solitons (1999)
    Springer
    Journal of engineering mathematics 36 (1999), S. 163-184 
    Details
    ISSN: 1573-2703
    Keywords: fiber optics ; nonlinear Schrödinger equation ; multiple scales ; dispersion ; solitons.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract Multiple-scale averaging is applied to the nonlinear Schrödinger equation with rapidly varying coefficients, and use the results to analyze pulse propagation in an optical fiber when a periodic dispersion map is employed. The effects of fiber loss and repeated amplification are taken into account by use of a coordinate transformation to relate the pulse dynamics in lossy fibers to that in equivalent lossless fibers. Second-order averaging leads to a general evolution equation that is applicable to both return-to-zero (soliton) and non-return-to-zero encoding schemes. The resulting equation is then applied to the specific case of solitons, and an asymptotic theory for the pulse dynamics is developed. Based upon the theory, a simple and effective design of two-step dispersion maps that are advantageous for wavelength-division-multiplexed soliton transmission is proposed. Theuse of these specifically designed dispersion maps allows simultaneous minimization of dispersive radiation in several different channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004554209222
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 85
    Electronic Resource
    Electronic Resource
    Preparation and application of poly(vinylamine)/alginate microcapsules to culturing of a mouse erythroleukemia cell line (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1115-1118 
    Details
    ISSN: 0006-3592
    Keywords: microencapsulation ; poly(vinylamine) ; cell culture ; mechanical strength ; erythropoietin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Poly(vinylamine) was synthesized and used to replace poly-L-lysine in forming microcapsule with alginate. Test results indicated that capsules with good mechanical strength and permeability could be obtained under the controlled treatment conditions of poly(vinylamine) and alginate. Application of the current microcapsular system to cell culture was demonstrated by the usage of erythropoietin- (EPO-) producing IW32 mouse erythroleukemia cells. The encapsulated IW32 cells grew to a density of 8 × 107 cells/mL, two times that found in the corresponding poly-L-lysine/alginate capsules. The EPO accumulation inside the microcapsule with the current encapsulation system was also higher. A concentration of 7.3 U/mL was attained as compared to 4.3 U/mL in the poly-L-lysine/alginate microcapsule. © 1992 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400916
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 86
    Electronic Resource
    Electronic Resource
    Improved taxol yield by aromatic carboxylic acid and amino acid feeding to cell cultures of taxus cuspidata (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 967-971 
    Details
    ISSN: 0006-3592
    Keywords: taxol production ; Taxus cuspidata ; cell culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cell culture of Taxus cuspidata represents an alternative to whole plant extraction as a source of taxol and related taxanes. Feeding phenylalanine to callus cultures was previously shown to result in increased taxol yields, probably due to the involvement of this amino acid as a precursor for the N-benzoylphenylisoserine side chain of taxol. Inthis study, we have examined the effect of various concentrations of phenylalanine, benzoic acid, N-benzoylglycine, serine, glycine, alanine, and 3-amino-3-phenyl-propionic acid on taxol accumulation in 2-year-old cell suspensions of Taxus cuspidata, cell line FCL1F, and in developing callus cultures of T. cuspidata. All compounds tested were included in media at stationary phase (suspensions) or after the period of fastest growth (calli). Alanine and 3-amino-3-phenyl-propionicacid were tested only in callus cultures and did not affect taxol accumulation. Significant increases or trends toward increases in taxol accumulationin callus and suspensions were observed in the presence of phenylalanine, benzoic acid, N-benzoylglycine, serine, and glycine. The greatest increases in taxol accumulation were observed in the presence of various concentrations of phenylalanine (1 mM for callus; 0.05, 0.1, and 0.2 mM for suspensions) and benzoic acid (0.2 and 1 mM for callus and 0.05, 0.1, and 0.2 mM for suspensions). Increases in taxol yields of cell suspensions in the presence of the most effective precursors brought taxol amounts at stationary phase from 2 μg · g-1 to approximately 10 μg . g-1 of the extracted dry weight. The results are discussed in termsof possible implications to taxol biosynthesis and in terms of practical applications to large-scale cell culture systems for the production ofthis drug. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440813
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 87
    Electronic Resource
    Electronic Resource
    Effect of light irradiation on anthocyanin production by suspended culture of Perilla frutescens (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 653-658 
    Details
    ISSN: 0006-3592
    Keywords: light irradiation ; anthocyanin production ; Perilla frutescens ; cell culture ; bioreactor cultivation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: After a series of experiments on photoperiodicity and light intensity under daylight supplied by an ordinary fluorescent lamp in cultivations using a flask and a roux bottle, it was found that irradiation at 27.2 W/m2 for the whole period was effective for anthocyanin production by a suspended culture of Perilla frutescens (shiso). A high amount of anthocyanin pigments, 3.0 g/L, was obtained in a bubble column bioreactor after 10 days of cultivation at an aeration rate of 0.1 vvm with light irradiation at 27.2 W/m2, while 2 g/L was obtained at 13.6 W/m2 and very little at 54.4 W/m2. A high amount of anthocyanin pigments, 2.9 g/L, was also produced using an aerated and agitated bioreactor at an agitation speed of 130 rpm, an aeration rate of 0.1 vvm and light irradiation intensity of 27.2 W/m2. The amount of anthocyanin produced was more than twice that without light irradiation, Keeping the other cultivation conditions the same. The results obtained also showed that the amount of anthocyanin pigment accumulated in a shake flask could be rather well reproduced in bioreactors for both aerated culture, and aerated and agitated culture, by improving the conditions of light irradiation, which conspicuously affects metabolite formation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380610
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 88
    Electronic Resource
    Electronic Resource
    Proliferation of anchorage-dependent contact-inhibited cells: I. Development of theoretical models based on cellular automata (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 459-470 
    Details
    ISSN: 0006-3592
    Keywords: cell culture ; contact inhibition phenomena ; discrete mathematical model ; cell proliferation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We report the development of new class of discrete models that can accurately describe the contact-inhibited proliferation of anchorage-dependent cells. The models are based on cellular automata, and they quantitatively account for contact inhibition phenomena occurring during all stages of the proliferation process: (a) the initial stage of “exponential” growth of cells without contact inhibition; (b) the second stage where cell colonies form and grow with few colony mergings; and (c) the final stage where proliferation rates are dominated by colony merging events. Model prediction are presented and analyzed to study the complicated dynamics of large cell populations and determine how the initial spatial cell distribution, the seeding density, and the geometry of the growth surface affect the observed proliferation rates. Finally, we present a model variant that can simulate contact-inhibited proliferation of asynchronous cell populations with arbitrary cell cycle-time distribution. The latter model can also compute the percentage of cells that are in a specific phase of their division cycle at a given time.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380504
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 89
    Electronic Resource
    Electronic Resource
    Kinetics of recombinant immunoglobulin production by mammalian cells in continuous culture (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 972-976 
    Details
    ISSN: 0006-3592
    Keywords: cell culture ; antibody production ; fermentation ; continuous culture ; cell growth ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A clonal derivative of a transfectant of the SP2/O myeloma cell line producing a chimeric monoclonal antibody was maintained in steady-state, continuous culture at dilution rates ranging from 0.21 to 1.04 day-1. The steady-state values for nonviable and total cell concentrations increased as the dilution rate decreased, while the viable cell concentration was roughly independent of the dilution rate. At steady state, the specific growth rate increased and the specific death rate decreased as the dilution rate increased. The maximum specific growth rate was 1.15 day-1. Antibody production was growth associated and the specific rate of antibody production increased linearly as the specific growth rate increased.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380903
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 90
    Electronic Resource
    Electronic Resource
    Kinetic study of hybridoma cell growth in continuous culture: II. Behavior of producers and comparison to nonproducers (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1020-1028 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; cell culture ; continuous culture ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A hybridoma cell line, AFP-27-P, was cultivated in continuous culture under glucose-limited conditions. The viable cell concentration, dead-cell concentration, and cell volume all varied with the dilution rate. A model previously developed for a nonproducing clone of the same cell line, AFP-27-NP, was extended to describe the behavior of the cells. The relationship between the specific growth rate and glucose concentration is described by a function similar to the Monod model. A threshold glucose concentration and a minimum specific growth rate are incorporated; the model is meaningful only at glucose concentration and a minimum specific growth rate are incorporated; the model is meaningful only at glucose concentrations and specific growth rates above these levels. The relationship between the death rate and the glucose concentration is described by an inverted Monod-type function. Furthermore, the yield coefficient based on glucose is constant in the lower range of specific growth rates and changes to a new constant value in the upper range of specific growth rates. No maintenance term for glucose consumption is used; in the plot of specific glucose consumption rate vs. specific growth rate, the line intercepts the specific growth rate at a value close to the minimum growth rate. The productivity of antibody as a function of the specific growth rate is described by a mixed type model with a noon-growth-associated term and a negative-growth-associated term. The values for the model parameters were determined from regression analysis of the steady state data.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380910
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 91
    Electronic Resource
    Electronic Resource
    Damaging agitation intensities increase DNA synthesis rate and alter cell-cycle phase distributions of CHO cells (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 978-990 
    Details
    ISSN: 0006-3592
    Keywords: DNA synthesis rate ; agitation ; cell-cycle kinetics ; flow cytometry ; cell culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of fluid-mechanical force (agitation) on the cell cycle kinetics of Chinese hamster ovary (CHO) cells cultured in suspension in 2-L bioreactors has been examined. A two-color flow cytometry method was used to determine the fraction rate of DNA synthesis. With increased agitation intensity, cell viability decreased as a result of increased cell death. However, increased agitation induced the viable cells of the culture to a higher proliferative state relative to a control culture. The fraction of viable cells of the high-agitation culture (250 rpm) in S phase was higher (up to 45%) and in G1 phase was lower (up to 50%) compared with the viable cells of the control culture (80 rpm). The DNA synthesis rate per viable S-phase cell of the high-agitation culture was confirmed by recovery experiments, which were conducted to measure the apparent specific growth rate and the cell cycle kinetics of the high-agitation culture upon reduction in the agitation rate from 250 rpm back to 80 rpm. The apparent specific growth rate of the test culture, calculated for the first 12 h of the recovery period, was greater than the apparent specific growth rate of the control culture. Furthermore, the proliferative state of the viable cells of the test culture, which had become higher relative to the control culture during the high agitation period, gradually approached the level of the control culture during recovery. Results also show that the magnitude of the agitation intensity; the culture agitated at 250 rpm attained a greater proliferative state than a parallel culture agitated at 235 rpm. The 250-rpm culture had a higher fraction of S-phase and a lower fraction of G1-phase cells than the 235-rpm culture. The DNA sunthesis rate per viable S-phase cell of the 250-rpm culture was greater than of the 235-rpm culture. © 1992 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400814
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 92
    Electronic Resource
    Electronic Resource
    Cultivation of virus antigen in fibroblast cells using a glass fiber bed reactor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 635-642 
    Details
    ISSN: 0006-3592
    Keywords: MRC-5 ; anchorage-dependent ; fibers ; cell culture ; hepatitis A ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The anchorage-dependent cell line, MRC-5, was cultivated successfully on glass fibers with diameters ranging from 24 to 120 μm, despite vast differences in substrate curvature. Multilayer cell growth was observed, particularly for fiber diameters 30 μm and below, which differed from the typical monolayer growth observed in T-flask cultivations. Cells were maintainable at a reduced incubation temperature and were demonstrated to support virus replication for the 21-day antigen production period. Direct microscopic observation, along with indirect calculations, indicated that only a small fraction (about 10%) of the total available fiber surface area was occupied by cells. Thus, productivity per unit surface area was replaced by productivity per unit medium volume when evaluating fiber bed performance. Antigen and protein yields, as well as nutrient uptakes, were 1.5- to 2.5-fold greater than parallel T-flask cultures when compared on this basis. Corresponding available surface area-based values were 10- to 15-fold lower for the fiber bed reactor. The multilayer cell morphology obtained in the fiber bed was attractive for antigen production when immobilized in a column reactor system. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420512
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 93
    Electronic Resource
    Electronic Resource
    Characterization of a recombinant antibody produced in the course of a high yield fed-batch process (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 727-735 
    Details
    ISSN: 0006-3592
    Keywords: monoclonal antibody ; glycosylation ; cell culture ; fed-batch ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many mammalian cell fed-batch processes rely on maintaining the cells in a viable and productive state for extended periods of time in order to reach high final concentrations of secreted protein. In the work described herein, a nonamplified NSO cell line was transfected with a vector expressing a recombinant human anti-HIV gp 120 monoclonal antibody (Mab) and a selectable marker, glutamine synthetase. A fed-batch process was developed which improved product yields tenfold over the yields reached in batch culture. In this case, the clone was cultured for a period of 22 days and produced 0.85 g Mab/L. To gauge the effect of extended culture lifetime on product quality, biochemical characteristics of MAb isolated from different time points in the fed-batch culture were determined. The apparent molecular weight of the MAb was constant throughout the course of the culture. Isoelectric focusing revealed four major charged species, with a fifth more acidic species appearing later in the culture. The antigen binding kinetics were constant for MAb isolated throughout the culture period. Glycosylation analysis, on the other hand, revealed that MAb produced later in the culture contained greater percentages of truncated N-acetylglucosamine and highmannose N-glycans. Possible contributions to this underglycosylated material from either cell lysis or synthesis from noviable cells were found to be negligible. Instead, the viable cells appeared to be secreting more truncated and high mannose MAb glycoforms as the culture progressed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440609
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 94
    Electronic Resource
    Electronic Resource
    Preferential release of one daughter cell during division of immobilized chinese hamster ovary cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 374-378 
    Details
    ISSN: 0006-3592
    Keywords: cell culture ; patterened surfaces ; cell adhesion ; hydrogel ; polyHEMA ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chinese hamster ovary (CHO) cells were attached to tiny adhesive sites in poly-2-hydroxyethyl methacrylate(polyHEMA-) coated glass, and their divison properties were examined. The adhesive sites were produced by placing a metal mask, containing 8-μm-diameter holes arranged in a regular pattern, on top of the coated glass and exposing the sandwich to glow discharge treatment. This treatment produced an ordered array of circular cavities in the polyHEMA down to the glass. These adhesive sites were smaller in diameter than a newborn CHO cell, so that, upon division, there would theoretically be room for only one of the two new daughter cells to remain attached. It was found that individual CHO cells attached to, and grew upon, the sites, and that division normally resulted in the releas of one of the two new daughters. It is concluded that this culture technique has applications in research on the mammalian cell cycle, cell partitioning, and cellular senescence. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450412
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 95
    Electronic Resource
    Electronic Resource
    Heterogeneity within populations of recombinant Chinese hamster ovary cells expressing human interferon-γ (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 147-158 
    Details
    ISSN: 0006-3592
    Keywords: CHO cell ; cell aggregation ; recombinant human interferon-γ ; mammalian cell culture ; cell culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Chinese hamster ovary (CHO) cell line has great commercial importance in the production of recombinant human proteins, especially those for therapeutic use. Much attention has been paid to CHO cell population physiology in order to define factors affecting product fidelity and yield. Such studies have revealed that recombinant proteins, including human interferon-γ (IFN-γ), can be heterogeneous both in glycosylation and in proteolytic processing. The type of heterogeneity observed depends on the growth physiology of the cell population, although the relationship between them is complex. In this article we report results of a cytological study of the CHO320 line which expresses recombinant human IFN-γ. When grown in suspension culture, this cell line exhibited three types of heterogeneity: (1) heterogeneity of the production of IFN-γ within the cell population, (2) heterogeneity of the number of nuclei and mitotic spindles in dividing cells, and (3) heterogeneity of cellular environment. The last of these arises from cell aggregates which form in suspension culture: Some cells are exposed to the culture medium; others are fully enclosed within the mass with little or no direct access to the medium. Thus, live cells producing IFN-γ are heterogeneous in their environment, with variable access to O2 and nutrients. Within the aggregates, it appears that live cells proliferate on a dead cell mass. The layer of live cells can be several cells deep. Specific cell-cell attachments are observed between the living cells in these aggregates. Two proteins, known to be required for the formation of certain types of intercellular junctions, spectrin and vinculin, have been localized to the regions of cell-cell contact. The aggregation of the cells appears to be an active process requiring protein synthesis. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260460208
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 96
    Electronic Resource
    Electronic Resource
    A fiber-bed bioreactor for anchorage-dependent animal cell cultures: Part I. Bioreactor design and operations (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 755-761 
    Details
    ISSN: 0006-3592
    Keywords: cell culture ; fiber-bed bioreactor ; anchorage-dependent cell cultures ; airlift ; bioreactor design ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A concentric-cylinder airlift reactor, in which the annulus is a packed bed of glass fibers, has been developed in order to facilitate the scaleup and enhance the volumetric productivity of anchorage-dependent animal cell cultures. In this bio-reactor, oxygen-containing gas is sparged through the inner draft tube, causing bubble-free medium to flow through the fiber bed in the outer cylinder and providing both oxygenation and convective nutrient transfer to the cells. Several other desirable features for reactor operation are also provided by this design. Cell cultivations in this bioreactor have been successfully carried out and provide data for the feasibility of the large-scale cell cultivation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370810
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 97
    Electronic Resource
    Electronic Resource
    Development of a single-pass ceramic matrix bioreactor for large-scale mammalian cell culture (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1056-1068 
    Details
    ISSN: 0006-3592
    Keywords: cell culture ; bioreactor ; ceramic matrix ; hybridoma cells ; oxygen transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A single-pass, plug-flow bioreactor has been developed in which oxygen is supplied to entrapped hybridoma cells via sllicone tubes threaded through the square channels of a macroporous ceramic monolith. Oxygen diffuses from the gas phase, through the silicone tubing, across the open square channel, and into the pores of the ceramic wall where it is consumed by entrapped cells. Advantages of such a reactor include higher product yields, protection of cells from detrimental hydrodynamic effects, no internal moving parts to compromise asepsis, and simplicity of operation. A prototype bioreactor was constructed and operated over a range of residence times. A side-by-side experimental comparison with a conventional recycle bioreactor was performed by inoculating both bioreactors with cells from the same stock culture and feeding medium from the same reservoir. Final antibody titers were 80% higher in the single-pass bioreactor at a residence time of 200 minutes compared with those of the recycle bioreactor at a residence time of 800 minutes. A theoretical analysis of oxygen transport in this bioreactor is developed to highlight important design criteria and operating strategies for scale-up. © 1992 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400909
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 98
    Electronic Resource
    Electronic Resource
    Rheological properties of mammalian cell culture suspensions: Hybridoma and HeLa cell lines (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 745-754 
    Details
    ISSN: 0006-3592
    Keywords: viscoelsticity ; cell culture ; oscillatory dynamic shear ; steady shear ; shear sensitivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Data on viscous (η′) and elastic (η″) components of the complex viscosity versus oscillatory angular frequency (0.01 to 4.0 rad/s) with increasing strains were obtained for hybridoma cell (62′D3) and HeLa cell (S3) suspensions in PBS at 0.9 (mL/mL) cell volume fraction using a Weissenberg rheogoniometer equipped with two parallel plate geometry at ambient temperature. Both cell suspensions exhibited shear thinning behavior. From the measured viscoelastic properties, the yield stress was calculated. Hybridoma cell suspension (15 μm as the mean diameter of cells) showed the yield stress at 550 dyne/cm2 that was 1.8 times higher than the value of HeLa cell suspension (22 μm mean diameter) as measured at the oscillatory angular frequency, 4.0 rad/s. The apparent viscosities of HeLa cell suspension at four concentrations and varying steady shear rate were also determined using the Brookfield rotational viscometer. The yield stress to steady shear test was about 130 dyne/cm2 for HeLa cell suspension at 0.9 (mL/mL) cell volume fraction. The apparent viscosity was in the range about 1 ∼ 1000 Poise depending on the cell concentration and shear rate applied. A modified semiempirical Mooney equation, \documentclass{article}\pagestyle{empty}\begin{document}$ \eta = \eta _0 \exp [K\dot \gamma ^{ - \beta } \phi /(1 - K''\sigma \phi _c /D)] $\end{document} was derived based on the cell concentration, the cell morphology, and the steady shear rate. The β, shear rate index, was estimated as 0.159 in the range of shear rate, 0.16 to 22.1 s-1, for the cell volume fractions from 0.6 to 0.9 (mL/mL). In this study, the methods of determining the shear sensitivity and the viscous and the elastic components of mammalian cell suspensions are described under the steady shear field. © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410709
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 99
    Electronic Resource
    Electronic Resource
    On-line characterization of a hybridoma cell culture process (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 170-177 
    Details
    ISSN: 0006-3592
    Keywords: cell culture ; laser turbidity probe ; on-line measurements ; process control ; specific rates ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The on-line determination of the physiological state of a cell culture process requires reliable on-line measurements of various parameters and calculations of specific rates from these measurements. The cell concentration of a hybridoma culture was estimated on-line by measuring optical density (OD) with a laser turbidity probe. The oxygen uptake rate (OUR) was determined by monitoring dynamically dissolved oxygen concentration profiles and closing oxygen balances in the culture. The base addition for neutralizing lactate produced by cells was also monitored on-line via a balance. Using OD and OUR measurements, the specific growth and specific oxygen consumption rates were determined on-line. By combining predetermined stoichiometric relationships among oxygen and glucose consumption and lactate production, the specific glucose consumption and lactate production rates were also calculated on-line. Using these on-line measurements and calculations, the hybridoma culture process was characterized on-line by identifying the physiological states. They will also facilitate the implementation of nutrient feeding strategies for fed-batch and perfusion cultures. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440205
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 100
    Electronic Resource
    Electronic Resource
    Kinetics of taxol production, growth, and nutrient uptake in cell suspensions of Taxus cuspidata (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 205-210 
    Details
    ISSN: 0006-3592
    Keywords: taxol production ; Taxus cuspidata ; cell culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cell culture of Taxus cuspidata may represent an alternative to extraction of bark as a source of taxol and related taxanes. Cell suspensions of a cell line of T. cuspidata were grown for 44 days in shake flasks containing B5C2 medium. Throughout the growth cycle, fresh and dry weight accumulation, taxol yield on a dry weight basis, taxol accumulation in the medium, pH and pigmentation variation in the medium, as well as the uptake of sucrose, glucose, fructose, nitrate, and inorganic phosphate from the culture medium were examined. The results showed that the growth was relatively slow (doubling times of 17 and 20 days for fresh and dry weight, respectively), and taxol accumulation in the cells was non-growth related (higher in the stationary phase) and at relatively low levels (up to 4 μg/g of the extracted dry weight). Taxol concentration in the medium had two peaks: one during the early (0.4μg/mL) and another during the late (0.1-μg/mL) parts of the growth cycle. On a volumetric basis, the average total amount of taxol produced during the stationary phase (day 38) was 0.15 μg/mL, of which approximately 66% was in the medium and 34% was in the cells. Total carbohydrate uptake was closely associated with the increase in dry biomass. Sucrose was apparently extracellularly hydrolyzed after the first 6 days of culture; glucose was used before fructose. Nitrate was assimilated throughout the growth cycle, but phosphate was absorbed within the first week of culture. The pH variation showed an initial drop followed by a trend toward alkalinization for most of the growth period. Dark pigmentation in the medium increased progressively, particularly during the stationary phase. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440209
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...