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
  • 1
    Electronic Resource
    Electronic Resource
    Peristance of bacteria in the presence of viable, nonencysting, bacterivorous ciliates (1988)
    Springer
    Microbial ecology 16 (1988), S. 197-211 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Laboratory studies of the interactions between a bacterial population and a population of bacterivorous ciliates consistently show that the bacteria are able to persist in the presence of viable ciliates. Reproduction of the bacteria, presumably at the expense of substrates produced by death and lysis of the ciliates and/or by their metabolic activity, has been suggested to be a factor involved in the observed bacterial persistence. Rates and extents of growth ofEscherichia coli in broths of mixed cultures of this bacterium and the ciliateTetrahymena pyriformis were determined in order to provide some data necessary to assess the importance of the suggested factor. In addition, an attempt was made to suppress bacterial growth on produced substrates so that feeding of the ciliates could be studied free of this complication. However, the procedure tested—addition of the antibiotic chloramphenicol (CM) at a concentration of 150μg/ml—led to other complications that made it impossible to obtain the desired information about feeding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02018914
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Ammonium selectively inhibits the regulated pathway of protein secretion in two endocrine cell lines
    Amsterdam : Elsevier
    Enzyme and Microbial Technology 16 (1994), S. 90-98 
    Details
    ISSN: 0141-0229
    Keywords: Ammonium ; endocrine cells ; protein secretion
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0141-0229(94)90069-8
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Towards the development of artificial endocrine tissues: 31P NMR spectroscopic studies of immunoisolated, insulin-secreting AtT-20 cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 431-443 
    Details
    ISSN: 0006-3592
    Keywords: AtT-20 spheroids ; alginate entrapment ; 31P and 1H NMR ; pancreas, bioartificial ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transformed, insulin-secreting endocrine cells have been proposed as an alternative to islets for the development of a bioartificiat pancreas. With appropriate immunoprotection, such cells may be implanted without the need for patient immunosuppression. Use of continuous cell lines alleviates the cell availability limitation, but poses questions regarding thestability and biochemical and secretory function of the preparation, especially in the longterm. We have developed a bioreactor/perfusion system, compatible with a horizontal-bore NMR instrument, that can maintain immunoprotected endocrine cells for prolonged periods of time. 31P NMR spectroscopy was used to study the bioenergetics of recombinant, insulin-secreting mouse pituitary AtT-20 cells entrapped as spheroids in calcium alginate/poly-L-lysine/alginate beads. NMR provided data verifying the macroscopic homogeneity within the bioreactor and allowing the evaluation of changes in cellular bioenergetics for a period of 70 days under different culture conditions. Levels of high-energy phosphates changed slightly during the first 40 days of the experiment, then decreased considerably as cell death occurred. Rates of glucose consumption and insulin-related peptide secretion also remained constant for 40 days and decreased rapidly thereafter. This study constitutes the beginning of an extensive quantitative analysis of the biochemistry of transformed endocrine cell lines in a sequestered, artificial tissue environment. © 1995 John Wiley & Sons Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470404
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Coexistence of bacteria and feeding ciliates: Growth of bacteria on autochthonous substrates as a stabilizing factor for coexistence (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 714-728 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: There is good evidence that the specific feeding and growth rates of a population of suspension-feeding ciliates on a population of bacteria is described by the classic Monod model or something very like it. However, use of this model combined with the assumption that feeding of the ciliates is the only interaction between the populations leads to predictions grossly at variance with experimental observations. A second interaction between the populations, growth of the bacteria on products of lysis, and perhaps metabolism of the ciliates is known to occur and might be an important factor in determining the dynamics of ciliate-bacterial systems. Whether or not this is the case is examined in the present article. It is concluded that accounting for the second interaction does not remove the discrepancies between model predictions and experimental observations. It is concluded also that the second interaction is likely not important except in batchtype situations where the supply of available energy for supporting biological activity is not replenished.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260290608
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Use of regulated secretion in protein production from animal cells: An evaluation with the AtT-20 model cell line (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 771-780 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Regulated secretion, i.e., the ability of certain specialized animal cells to store secretory proteins intracellularly and release them upon stimulation, may be used to realize production schemes that facilitate downstream processing of protein products. Mouse AtT-20 cells expressing recombinant human insulin and human growth hormone (hGH) were found to secrete the proteins at relatively low and constant rates when exposed to media with no secretion agonists: basal rates were 1.0-1.6 μU insulin-reiated peptides and 0.38 ng hGH/105 cells-h. When induced with 8 brorno-cyclic AMP (BrcAMP), the cells secreted recombinant proteins at initial rates 3.5-9-fold higher. A cycling secretion experiment was conducted with the insulin-producing cells in which the cells were exposed alternately to complete growth medium and to secretion medium with BrcAMP. During the first three cycles, the cells secreted immunoreactive insulin at the foregoing high induced rates when they were exposed to BrcAMP. The cells then started to detach from the culture surface, leading to a reduction of BrcAMP-induced secretion. Operational modifications that may result in improved system performance are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350804
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Effect of addition of wall growth to a model of ciliate-bacterial interactions (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 875-881 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340619
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Cultivation of recombinant, insulin-secreting AtT-20 cells as free and entrapped spheroids (1993)
    Springer
    Cytotechnology 13 (1993), S. 1-12 
    Details
    ISSN: 1573-0778
    Keywords: tissue engineering ; AtT-20 cells ; AtT-20 spheroids ; alginate ; entrapped spheroids ; insulin secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Animal cells from endocrine glands have potential applications in bioprocessing, for the production of hormones, enzymes, possibly also recombinant proteins, and in tissue engineering, for the development of immunoisolated, implantable devices for long-term treatment of endocrine disorders. Immunoisolation can be achieved by surrounding cells with a biocompatible polymer which allows diffusion of nutrients and metabolites, including hormones, but excludes higher molecular weight antibodies and cytotoxic cells. Primary hormone-secreting cells cannot be effectively amplified in culture, so the large-scale application of implantable systems based on such cells is limited by cell availability. In this study, we conducted an initial assessment of the feasibility of using transformed, continuous cell lines in immunoisolated devices. The model system employed consisted of mouse pituitary tumor AtT-20 cells which secrete recombinant proinsulin and an insulin-like peptide and exhibit a high growth potential. Cells were cultivated as spheroids in spinner flasks and entrapped as such in alginate/polylysine/alginate beads. Free and entrapped spheroids were propagated in fed-batch, suspension cultures. Entrapment did not significantly affect spheroid metabolism or basal secretion. Entrapped spheroids did not increase in size or number and maintained roughly constant metabolic and basal secretory activities over a 15-day period. Free spheroids in suspension increased in size during the sami period, but also maintained constant metabolism and basal secretion, apparently because of a concomitant increase in hypoxic and/or necrotic cells. The potential of using continuous cell lines in the development of bioartificial endocrine organs is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749970
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Multiple episodes of induced secretion of human growth hormone from recombinant AtT-20 cells (1990)
    Springer
    Cytotechnology 4 (1990), S. 111-119 
    Details
    ISSN: 1573-0778
    Keywords: AtT-20 ; cycling operation ; human growth hormone ; regulated and constitutive secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Recombinant AtT-20 cells expressing human growth hormone (hGH) secreted the hormone at a constant, basal rate of 0.3–0.5 ng/105 cells-hour when exposed to medium without secretagogues. When triggered with 8 bromo-cyclic AMP, cells secreted hGH at an initial rate of 1.7 ng/105 cells-hour while intracellular hGH declined sharply. Upon extended exposure to secretagogue, secretion decreased gradually to the basal rate and intracellular hGH stabilized at a value 40% the initial. In cells switched from secretion to growth medium, the total rate of hGH accumulation intracellularly and in medium was 2.2 times that observed with cells never exposed to secretagogue; however, only a fraction of the hormone was stored intracellularly and the rest was secreted. When cells were exposed alternately to growth and secretion medium, induced cells secreted at rates at least two times higher than uninduced controls during the first five cycles. The induced response deteriorated with time, however, in parallel with outgrowth of attached cells by foci of round cells, and by the eighth cycle induced secretion did not occur. Operational modifications that may improve the performance of cycling schemes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365091
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Towards the development of a bioartificial pancreas: Immunoisolation and NMR monitoring of mouse insulinomas (1994)
    Springer
    Cytotechnology 15 (1994), S. 351-363 
    Details
    ISSN: 1573-0778
    Keywords: bioartificial pancreas ; βTC3 cells ; immunoisolation ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A promising method for diabetes treatment is the implantation of immunoisolated cells secreting insulin in response to glucose. Cell availability limits the application of this approach at a medically-relevant scale. We explore the use of transformed cells that can be grown to large homogeneous populations in developing artificial pancreatic tissues. We also investigate the use of NMR in evaluating, non-invasively, cellular bioenergetics in the tissue environment. The system employed in this study consisted of mouse insulinoma βTC3 cells entrapped in calcium alginate/poly-L-lysine (PPL)/alginate beads. The PPL layer imposed a molecular weight cutoff of approximately 60 kDa, allowing nutrients and insulin to diffuse through but excluding high molecular weight antibodies and cytotoxic cells of the host. We fabricated a radiofrequency coil that can be double-tuned to1H and31P, and an NMR-compatible perfusion bioreactor and support circuit that can maintain cells viable during prolonged studies. The bioreactor operated differentially, was macroscopically homogeneous and allowed the acquisition of1H images and31P NMR spectra in reasonable time intervals. Results indicated that entrapment had little effect on cell viability; that insulin secretion from beads was responsive to glucose; and that the bioenergetics of perfused, entrapped cells were not grossly different from those of cells never subjected to the immobilization procedure. These findings offer promise for developing an artificial pancreatic tissue for diabetes treatment based on continuous cell lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00762410
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    A model of secretory protein trafficking in recombinant AtT-20 cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 280-295 
    Details
    ISSN: 0006-3592
    Keywords: AtT-20 cells ; secretory proteins ; intracellular trafficking ; conversion compartment ; trans-Golgi ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: After their synthesis, secretory proteins in animal cells undergo a series of transport and processing steps before they are secreted. The amount and quality of protein obtained in culture medium depends on the rates of these intracellular steps. We present a model of recombinant protein trafficking in mouse pituitary AtT-20 cells based on currently available biological knowledge, plausible hypotheses, and quantitative secretion results, and we use it to simulate the dynamics of basal and induced secretion and to predict the dynamics of intracellular trafficking events. Besides the endoplasmic reticulum and Golgi, the model recognizes a conversion compartment (CC) where final processing of protein occurs, a storage compartment from which protein is secreted only in the presence of secretion stimulus, and constitutive and pseudoregulated (PR) pathways of secretion. The model further assumes that the protein flux is split between CC and PR and that the storage compartment exerts a negative feedback on protein flux through CC. The model predictions are compared with experimental results on secretion of human growth hormone (hGH) and insulin related peptides and on accumulation of hGH upon removal of secretion stimulus. The model is in agreement with data when either of two hypotheses is implemented: (a) cells always exhibit a high sorting efficiency at the trans-Golgi, but CC has the capacity to process only a fraction of the protein flux leaving the Golgi compartment; (b) the processing capacity of CC never becomes saturated, but significant missorting at the trans-Golgi occurs; in the case, the protein flux toward the plasma membrane becomes split both at the trans-Golgi cisternae and between CC and PR. The usefulness of the type of model considered in providing a quantitative description of intracellular events and in designing new experiments is discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380310
    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...