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61.
Semicontinuously grown wild carrot ( Daucus carota L.) cells were used in an investigation of the effect of culture medium pH on ammonium uptake in suspension cultures as a first step in exploring the relationship between pH and anthocyanin biosynthesis. In contrast to published data showing decreasing uptake rates with decreasing culture medium pH, ammonium-limited, semicontinuous carrot cell cultures showed a 25% greater ammonium uptake rate at pH 4.5 than at pH 5.5. When cells that had been grown semicontinuously in medium with a pH of 4.5 or 5.5 were grown in batch cultures at pH 4.5, 5.5 or 6.5 the ammonium uptake rates were those of the semicontinuous cultures, indicating that the pH of the batch culture medium had no effect on ammonium uptake rates over 7 days. The cell culture was composed of very small aggregates when it was grown semicontinuously in medium at pH 4.5, but was composed of large aggregates when it was grown semicontinuously in medium at pH 5.5. The aggregation/disaggregation of the cells was pH dependent, as changing the pH of the semicontinuous culture medium altered the extent of the aggregation. We conclude that the change in culture medium pH caused the cells to aggregate or disaggregate which in turn decreased or increased the rate of ammonium uptake from the medium. 相似文献
62.
Evaluation of the serum-free medium MDSS2 for the production of poliovirus on vero cells in bioreactors 总被引:2,自引:0,他引:2
The serum-free medium MDSS2 (Merten et al., 1994), was used for cultivating Vero cells as well as for producing poliovirus
(Sabin type 1) in static and in perfused micro-carrier cultures. At slightly different growth rates of 0.0120/h and 0.0106/h,
respectively, static cultures in serum-containing (SCM) and serum-free (SFM) medium produced titers of 106.75 and 106.67 TCID50 per 50 μl; signifying a specific productivity of 0.89 and 1.07 TCID50/c.
Serum-free bioreactor cultures of Vero cells on DEAE-dextran microcarriers at 6.25 g/l produced cell densities of about 1.5×106c/ml. After infection with virus (multiplicity of infection (MOI) 0.1–0.3) titers of about 6.3×108 TCID50/ml were obtained, signifying an average specific productivity of 7.1 TCID50/c.h. Although these values were 4 and
2 fold, respectively, higher than in classical resum-based production processes (Montagnon et al. Dev. biol. Stand. 1981,
47, 55), a reference culture, for which cell growth was done in SCM and only virus production was done in SFM, produced 2×109 TCID/ml with an average specific virus production rate of 18.9 TCID50/c.h. The differences between the fully serum-free and
our reference process were mainly due to physiological differences of cells grown in SCM and SFM and also due to strongly
modified consumption kinetics after virus infection leading to limitations of one or several essential medium compounds, like
glucose and amino acids. Avoiding these limitations by increasing the residual concentration of glucose, glutamine, histidine,
and SH-amino acids, led to specific virus production rates (of about 17.9 TCID59/c.h.) comparable to those found in the reference
virus production process. The optimisation of the production of the poliovirus (Sabin 1) will be described with respect to
the modification of the medium composition.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
63.
Marc Lecouvey Céline Frochot Laurent Miclo Piotr Orlewski Michel Marraud Jean-Luc Gaillard Manh Thong Cung Régis Vanderesse 《Letters in Peptide Science》1997,4(4-6):359-364
The conformation of a benzodiazepine-like decapeptide corresponding tothe YLGYLEQLLR fragment of a casein has been examined in a sodium dodecylsulfate micellar medium using circular dichroism, two-dimensional1H NMR spectroscopy and restrained molecular dynamicssimulation. The decapeptide adopts an amphipathic 310-helicoidstructure in which theE6···R10 ionic bridgestabilizes the C-terminus. 相似文献
64.
Shinji Hosoi Mitsuo Satoh Hiromasa Miyaji Tatsunari Nishi Tamio Mizukami Mamoru Hasegawa Seiga Itoh Tatsuya tamaoki 《Cytotechnology》1995,19(1):1-10
Pro-UKS1 was designed as a thrombin-resistant derivative of pro-urokinase (pro-UK) by introducing a glycosylation site using site-directed mutagenesis. An expression plasmid for pro-UKS1, pMo1UKS1SEd1-5, was constructed and introduced into Namalwa KJM-1 cells (Hosoiet al., 1988), and cells resistant to G418 and Methotrexate (MTX) were obtained. Amongst them, the highest pro-UKS1 producer (resistant to 500 nM of MTX), clone 41-8, was selected and further characterized. Clone 41-8 was cultured in serum-free ITPSGF medium (Hosoiet al., 1988). Under the conventional conditions, the concentration of pro-UKS1 reached 26 g ml–1. Addition of glucose and tri-iodothyronine (T3) improved productivity, and the maximal productivity of pro-UKS1 was 67 g ml–1 day–1. In this conditioned medium, content of pro-UKS1 was above 80% of total proteins.Abbreviations BSA
bovine serum albumin
- dhfr
dihydrofolate reductase
- HEPES
4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- kb
kilobase pairs
- kDa
kilodaltons
- MTX
Methotrexate
- PBS
phosphate buffered saline
- pro-UK
pro-urokinase
- SDS-PAGE
sodium dodecyl sulfate-polyacrylamide gel electrophoresis
- T3
tri-iodothyronine
- Tween-PBS
phosphate buffered saline containing 0.05% Tween 80 相似文献
65.
R. Van Potter Theresa Ruh Evanson Debra P. Gayda James A. Gurr 《In vitro cellular & developmental biology. Plant》1984,20(9):723-731
Summary The induction and decay of ornithine decarboxylase (ODC) by insulin and asparagine in cultures of H4-II-EC3 (H35) hepatoma
cells was studied in a modified Waymouth medium in the presence of fetal bovine serum (FBS) and in serum-free media. The insulin
response was enhanced by the presence of asparagine although the effect of asparagine was not so much on the initial increase
as it was on a slowing of the decline after the maximum was reached at 6 to 8 h after the supplements were added together
with fresh medium. In all cases the initial ODC activity was zero at zero time for addition of media and supplements, and,
after reaching the maximum, activity declined to near zero by 24 h. Fetal bovine serum gave induction that followed a similar
time course but was inferior to the combintion, of insulin plus asparagine and, in fact, FBS inhibited the latter response.
Putrescine (the product formed from ornithine by ODC), at 10−5
M, markedly inhibited the induction of ODC by insulin or FBS, but the inhibition was less when asparagine was present.
This work was supported in part by Grants CA-07175, CA-22484, and CA-17334 from the National Cancer Institute. D. P. G. is
a Predoctoral Fellow at the Food Research Institute, supported by a fellowship from the Monsanto Fund and by NIH Grant R01-AI
15693 to Prof. Michael W. Pariza, Food Research Institute, University of Wisconsin, Madison. 相似文献
66.
Summary The Mishell-Dutton culture system for in vitro primary antibody response of mouse spleen cells was used to optimize the amino
acid composition of RPMI 1640 media. Each of the 20 amino acids was tested over a broad range of concentrations always leaving
the remaining 19 amino acids unaltered (i.e. at the formula recommended concentration). In several instances, higher plaque-forming
cell responses were obtained with an amino acid concentration that was either higher or lower than that recommended: (a) the
optimum concentration for valine, glutamine, and lysine lies considerably above the recommended one, (b) the optimum concentration
for leucine as well as for several other amino acids lies below the recommended concentration, and (c) the optimum concentration
for arginine corresponds exactly to the recommended concentration. The second round of optimization, i.e. combining of two
conditions that individually yielded an improved response often caused a decrease of response. The possibility is discussed
that for an optimal response a ratio of two or several amino acids rather than the absolute concentration of any one amino
acid is of importance.
The Basel Institute for Immunology was founded and is supported by F. Hoffman-La Roche & Co., Ltd. 相似文献
67.
Electron transport, phosphorylation and internal proton concentration were measured in illuminated spinach chloroplast thylakoid membranes under a number of conditions. Regardless of the procedure used to vary these parameters, the data fit a simple chemiosmotic model. Protons from Photosystem II did not appear to be utilized differently from those derived from Photosystem I. The maximal phosphorylation efficiency () for photophosphorylation in washed thylakoids under oxidizing conditions is likely to be . This value is consistent with a proton-to-electron-pair ratio of 4 for electron flow through both photosystems and a proton-to-ATP ratio of 3 for the chloroplast proton-ATPase. 相似文献
68.
F Zeytin C Mougin P Brazeau N Ling 《Biochemical and biophysical research communications》1984,120(2):540-547
The effects of forskolin and cholera toxin on the regulation of cAMP release were studied in a neurotensin-secreting rat C-cell line. The interaction of these agents with norepinephrine, a potent neurotensin secretagogue, was also investigated. Forskolin stimulated cAMP release 10(2)-10(3) fold while it increased neurotensin release 2-3 fold. Cholera toxin caused a 10(2)-10(3) fold increase in cAMP release and had no effect on neurotensin release. We conclude that the 44-2 C-cells provide a new model for studying the regulation of the concomitant (via forskolin) or independent (via cholera toxin) secretion of cyclic AMP and/or neurotensin. 相似文献
69.
70.
Modification of oligosaccharide-lipid synthesis and protein glycosylation in glucose-deprived cells 总被引:9,自引:0,他引:9
S J Turco 《Archives of biochemistry and biophysics》1980,205(2):330-339
Incubation of vesicular stomatitis virus-infected glucose-starved baby hamster kidney cells with [35S]methionine results in the synthesis of all viral proteins. However, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and tryptic peptide mapping, the G protein is abnormally glycosylated. Metabolic labeling of the oligosaccharide-lipid precursors with [3H]mannose for 15 min, followed by Chromatographic and enzymatic analysis, indicates that the radiolabeled lipid-linked oligosaccharides are devoid of glucose in contrast to the glucosylated oligosaccharide-lipids synthesized by cells grown in the presence of glucose. Also, in contrast to control cells, examination of the glycopeptide fraction reveals the presence of [3H]mannose-labeled glycopeptides which are resistant to erado-β-N-acetylglucos-aminidase H and are smaller in size than glycopeptides from mature vesicular stomatitis virus. In order to observe these effects, a minimum time of 5 h of glucose deprivation is necessary and the addition of 55 μm glucose or mannose to the medium reverses these effects. These results indicate that vesicular stomatitis virus-infected BHK cells deprived of glucose are unable to glucosylate the oligosaccharide-lipid intermediates and, consequently, are unable to glycosylate the G protein normally. 相似文献