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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract : The transcription factor E2F1 is known to mediate apoptosis in isolated quiescent and postmitotic cardiac myocytes, and its absence decreases the size of brain infarction following cerebral ischemia. To demonstrate directly that E2F1 modulates neuronal apoptosis, we used cultured cortical neurons to show a temporal association of the transcription and expression of E2F1 in neurons with increased neuronal apoptosis. Cortical neurons lacking E2F1 expression (derived from E2F1 -/- mice) were resistant to staurosporine-induced apoptosis as evidenced by the significantly lower caspase 3-like activity and a lesser number of cells with apoptotic morphology in comparison with cortical cultures derived from wild-type mice. Furthermore, overexpressing E2F1 alone using replication-deficient recombinant adenovirus was sufficient to cause neuronal cell death by apoptosis, as evidenced by the appearance of hallmarks of apoptosis, such as the threefold increase in caspase 3-like activity and increased laddered DNA fragmentation, in situ endlabeled DNA fragmentation, and numbers of neuronal cells with punctate nuclei. Taken together, we conclude that E2F1 plays a key role in modulating neuronal apoptosis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 85 (2003), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Multiple sclerosis (MS) is a neurological disorder characterized by myelin destruction and a variable degree of oligodendrocyte death. We have previously shown that overexpression of the transcription factor p53 can induce oligodendrocyte apoptosis. We investigated the mechanism of p53-induced apoptosis using primary cultures of central nervous system-derived adult human oligodendrocytes. Adenovirus-mediated p53 overexpression resulted in up-regulation of the death receptors Fas, DR4 and DR5 with subsequent caspase-mediated apoptosis of the oligodendrocytes. The oligodendrocytes were protected from p53-induced cell death by blocking signaling through Fas and/or tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors. Although lower levels of p53 did not induce apoptosis, the increase in death receptor expression was sufficient to render the oligodendrocytes susceptible to apoptosis in the presence of exogenous Fas ligand and TRAIL. These ligands are present in the inflammatory milieu of active MS lesions. In situ analysis of active MS lesions revealed increased p53 expression in oligodendrocytes in lesions that featured oligodendrocyte apoptosis and cell loss. Our data provide evidence for a novel role for p53 in the pathogenesis of MS.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The E2 protein of bovine viral diarrhea virus (BVDV) is a major viral glycoprotein and an attractive target for BVDV vaccines. Three replication defective recombinant adenoviruses expressing the BVDV/E2 protein (rAds/E2) were constructed. Two contain a constitutive promoter, and one an inducible promoter. All three recombinant adenoviruses induced very strong BVDV specific antibody responses in a mouse model as detected by enzyme-linked immunosorbant assay (ELISA) and neutralization tests. Induction of cellular immune responses was investigated in two recombinant adenoviruses with a constitutive promoter. The mononuclear cells from the immunized mice demonstrated a proliferative response after in vitro stimulation with an homologous BVDV strain, but only one of them induced the production of IFN-γ.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We have constructed a new adenovirus (Ad) expression vector, pAdBM5, that allows for the production of unprecedented levels of recombinant protein in the human 293 cell line using the Ad expression system. The main feature of this vector is a combination of enhancer sequences that increases the ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Methods in cell science 22 (2000), S. 137-145 
    ISSN: 1573-0603
    Keywords: Cell cloning ; Dicistronic vectors ; Fluorescence microscopy ; Green Fluorescent Protein ; Quixell™
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The inclusion of the gene encoding the Green Fluorescent Protein (GFP) or its derivatives into dicistronic transfer vectors is a useful method to visually identify cells that have incorporated a specific gene of interest. By combining this approach with the use of a micromanipulator, we have developed a protocol for the one-step isolation of cells expressing a specific transgene from a pool of transfected cells. Target fluorescent cells could be identified and isolated even when they occured at frequencies as low as 1/100,000. The use of Leibowitz L-15 serum-free medium and serum-coated non-charged petri dishes, along with minimal light exposure yielded maximal cell viability and high cloning efficiency (≈ 40%, on average) for a large number of cell lines, both adherent and suspension. Several variations of the basic method are presented, as well as guidelines for the choice of hardware components to implement our cloning workstation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1133-1140 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to develop an efficient process for large-scale production of recombinant protein, various factors were studied which affect the productivity of Sf-9 (Spodoptera frugiperda) insect cells when using the baculovirus expression system. It was shown that upon infection with the Bac-BRV6L recombinant baculovirus, the level per cell of VP6 (a bovine rotavirus nucleocapsid protein) would drop 10-fold when host cell density at the time of infection increased from 2 × 106 to 3 × 106 cells/mL. The decrease was found to be totally reversible by culture medium renewal after infection, even when cells were infected at the stationary phase. Recombinant protein production was 4-6 times higher using TNMFH medium supplemented with 10% fetal bovine serum (FBS) than in IPL/41 serum-free medium. Fine-tuning of infection parameters in a 4-L surface-aerated bioreactor resulted in the production of typically 350 mg/L of VP6 protein, representing more than 25% of total cell proteins.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 25-32 
    ISSN: 0006-3592
    Keywords: hybridoma culture ; monoclonal antibody production ; perfusion culture ; tangential filtration ; cell separation ; Nucleopore membranes ; alginate beads ; hollowfiber bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The efficiency of lgM production by hybridoma cells (1) cultured in suspension; (2) entrapped in alginate beads; or (3) packed in hollowfiber cartridge bioreactors, were compared in long-term perfusion cultures. The results showed that steady-state cell concentration and antibody production, per liter of perfused medium per day, were similar when cells were either entrapped in alginate beads of maintained in suspension. These values were also similar whether cells were maintained at high density in a hollowfiber cartridge bioreactro, or at low density in suspension. This work points out that cell behavior and antibody yield are comparable overall in the various perfusion systems currently used. However, a significant reduction of antibody production appeared whenever a part of the viable cells was lost in the filtrate. The reduction was due both to a decrease of viable cell yield and a decline of lgM productivity on a percell basis. This result is well in agreement with the previously presented model of “grow or die” cell cycle system of hybridoma, which proposes that the ratio of arrested to proliferating cells in perfusion cultures, should be increased in proportion to cell retention in the bioreactor, with a concomitant increase of lgM productivity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1140-1154 
    ISSN: 0006-3592
    Keywords: ammonia ; apoptosis ; hybridoma ; lactate ; myeloma ; nutrient deprivation ; programmed cell death ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present study, cell death was investigated in cultures of NS/0 myelomas and SP2/0-derived D5 hybridomas through morphological examination of cells stained with acridine orange and ethidium bromide. The relative contribution of elevated levels of lactic acid and ammonia, as well as deprivation of glutamine, cystine, and glucose on the induction of necrosis or apoptosis, was investigated. In batch culture of D5 hybridoma cells, induction of apoptotic cell death correlated with the exhaustion of glutamine, while in the case of NS/0 myelomas, it coincided with exhaustion of cystine. To determine whether limiting nutrients were the actual triggering factors for apoptosis in batch culture, exponentially growing cells were resuspended in glutamine or cystine-free media. Within 30 to 40 h, viability decreased to 50% and the nonviable cell population displayed typical apoptotic morphology, with crescents of condensed chromatin around the periphery of the nucleus, or with the entire nucleus present as one or a group of featureless, brightly staining spherical beads. Similarly, D5 hybridomas and NS/0 myelomas cultivated in glucose-free medium died mainly from apoptosis. Cells were also cultivated in fresh medium supplemented with elevated concentrations of ammonia (3.0 mM) and/or lactate (35 mM, 50 mM). This resulted in decreased viabilities and necrotic death in both cell lines. From these results, we conclude that D5 hybridomas and NS/0 myelomas deprived of essential nutrients die by apoptosis, whereas incubation in the presence of elevated levels of metabolic byproducts such as ammonia and lactate will induce necrotic cell death in these cells. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 781-787 
    ISSN: 0006-3592
    Keywords: hybridoma culture ; monoclonal antibody production ; perfusion culture ; continuous culture ; cell cycle ; tangential filtration ; cell separation ; nuclepore membranes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to elucidate the hybridoma life cycle and the limiting factors in perfusion systems, we performed cultures in a stirred tank bioreactor, coupled to an external tangential flow filtration unit. Cell density and antibody production in perfusion were consistent with previous studies. The average life span of the cells (2.1-2.2 days), antibody, productivity per cell produced (30-38 mg/109 cells) and cell size diameter evolution appeared similar to values observed in batch cultures. These observations highly suggest a similar “grow or die” life cycle. Cell and antibody production, strictly related to the medium perfusion rate, seem to be under the control of the nutrient availability. A hypothesis to explain such a life cycle of hybridoma cells in perfusion systems and a model for viable and dead cell density is proposed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 881-891 
    ISSN: 0006-3592
    Keywords: baculovirus ; recombinant proteins ; Sf-9 insect cells ; perfusion ; tangential filtration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A perfusion system based on a 4-L stirred tank bioreactor and a custom-designed tangential (cross-flow) filter was assembled to realize a scaleup of the Baculovirus Expression Vector System (BEVS). When perfused with 1 to 1.5 vol/day, Spodoptera frugiperda (Sf-9) insect cell cultures grew from 4 × 106 to 15 × 106 cells/mL over 3 to 4 days. The possibility of maintaining high specific production of recombinant VP6 protein (from bovine rotavirus) after baculovirus infection of the high-density cultures was then assessed. The process consisted of a growth phase in TNMFH + 10% FBS, followed by infection with Bac-BRV6L recombinant baculovirus and a shift to a low-serum (0 to 1%) medium for perfusion during the production phase. Multiple runs were executed, each including a battery of shaker flask controls at various cell densities and serum concentrations. On average, specific rVP6 production in the bioreactor amounted to 76% of that found in 20-mL shaker cultures simulatingthe bioreactor's high cell density, low serum concentration, and medium renewal rate. Mechanical stress generated by cell/medium separation in theperfusion process reduced cell growth rate but had minimal effect on rVP6production. Our results also indicated that serum concentration during the infection phase affected the rVP6 specific production in a cell density-dependent fashion. Although the feasibility of the cell density scale up was demonstrated, optimization is still needed to achieve a truly cost-effective process.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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