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1.
Biochemical and genetic characterization of three hamster cell mutants resistant to diphtheria toxin 总被引:2,自引:0,他引:2
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RK Draper D Chin D Eurey-Owens IE Scheffler MI Simon 《The Journal of cell biology》1979,83(1):116-125
We describe here three different hamster cell mutants which are resistant to diphtheria toxin and which provide models for investigating some of the functions required by the toxin inactivates elongation factor 2 (EF-2). Cell-free extracts from mutants Dtx(r)-3 was codominant. The evidence suggests that the codominant phenotype is the result of a mutation in a gene coding for EF-2. The recessive phenotype might arise by alteration of an enzyme which modifies the structure of EF-2 so that it becomes a substrate for reaction with the toxin. Another mutant, Dtx(r)-2, contained EF-2 that was sensitive to the toxin and this phenotype was recessive. Pseudomonas aeruginosa exotoxin is known to inactivate EF-2 as does diphtheria toxin and we tested the mutants for cross-resistance to pseudomonas exotoxin. Dtx(r)-1 and Dtx(r)-3 were cross-resistant while Dtx(r)-2 was not. It is known that diphtheria toxin does not penetrate to the cytoplasm of mouse cells and that these cell have a naturally occurring phenotype of diphtheria toxin resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance of the hybrid cells to diphtheria toxin. Intraspecies hybrids containing the genome of mutants Dtx(r)-1 and Dtx(r)-3 had some resistance while those formed with Dtx(r)-2 were as sensitive as hybrids derived from fusions between wild-type hamster cells and mouse 3T3 cells. 相似文献
2.
Hilal Taymaz‐Nikerel Amin Espah Borujeni Peter J.T. Verheijen Joseph J. Heijnen Walter M. van Gulik 《Biotechnology and bioengineering》2010,107(2):369-381
Metabolic network models describing growth of Escherichia coli on glucose, glycerol and acetate were derived from a genome scale model of E. coli. One of the uncertainties in the metabolic networks is the exact stoichiometry of energy generating and consuming processes. Accurate estimation of biomass and product yields requires correct information on the ATP stoichiometry. The unknown ATP stoichiometry parameters of the constructed E. coli network were estimated from experimental data of eight different aerobic chemostat experiments carried out with E. coli MG1655, grown at different dilution rates (0.025, 0.05, 0.1, and 0.3 h?1) and on different carbon substrates (glucose, glycerol, and acetate). Proper estimation of the ATP stoichiometry requires proper information on the biomass composition of the organism as well as accurate assessment of net conversion rates under well‐defined conditions. For this purpose a growth rate dependent biomass composition was derived, based on measurements and literature data. After incorporation of the growth rate dependent biomass composition in a metabolic network model, an effective P/O ratio of 1.49 ± 0.26 mol of ATP/mol of O, KX (growth dependent maintenance) of 0.46 ± 0.27 mol of ATP/C‐mol of biomass and mATP (growth independent maintenance) of 0.075 ± 0.015 mol of ATP/C‐mol of biomass/h were estimated using a newly developed Comprehensive Data Reconciliation (CDR) method, assuming that the three energetic parameters were independent of the growth rate and the used substrate. The resulting metabolic network model only requires the specific rate of growth, µ, as an input in order to accurately predict all other fluxes and yields. Biotechnol. Bioeng. 2010;107: 369–381. © 2010 Wiley Periodicals, Inc. 相似文献
3.
本文用脑室灌注和Fura2测定细胞内游离钙技术观察了地塞米松(dexamethasone,DEX)对家兔乙二醇双(2氨基乙醚)四乙酸性发热效应和下丘脑细胞内游离钙浓度([Ca2+]i)的影响,借此深入探讨地塞米松解热作用的中枢机制。结果发现:脑室灌注乙二醇双(2氨基乙醚)四乙酸(06nmol)引起家兔结肠温度明显升高,静脉注射地塞米松(5mg/kg)显著抑制家兔乙二醇双(2氨基乙醚)四乙酸性发热,地塞米松(60~120μmol/L)并不影响下丘脑细胞内[Ca2+]i,而事先脑室灌注抑制基因转录的放线菌素D(3nmol)则完全取消了地塞米松对乙二醇双(2氨基乙醚)四乙酸性发热的解热作用。这些结果提示:地塞米松显著抑制家兔乙二醇双(2氨基乙醚)四乙酸性发热,其机制与地塞米松激活脑内某些基因的表达有关,而与下丘脑神经细胞跨膜钙离子流无关。 相似文献
4.
IE Hughes 《BioEssays : news and reviews in molecular, cellular and developmental biology》1999,21(11):980-981
Instant Pharmacology (1999). Saeb-Parsy K, Assomull RG, Kahn FZ, Saeb-Parsy K, and Kelly E. John Wiley and Sons 349 pp. £19.99 pbk; ISBN 0471976393 © 1999 John Wiley & Sons, Inc. 相似文献
5.
本文利用激光散斑屈光测试系统详细探讨了夜近视(night myopia)的产生机制。夜近视在环境亮度降低到产生暗视觉时出现,并随亮度继续降低而增大,平均值为1.35D。实验证明眼睛球差和色差不是造成夜近视的主要因素。夜近视数值在暗适应过程中呈增大的趋势。在暗视觉时,由于视野中缺少适宜的刺激,眼睛处于暗焦(dark focus)休止状态,这是造成夜近视的主要原因。 相似文献
6.
7.
Comparative fluxome and metabolome analysis for overproduction of succinate in Escherichia coli
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8.
The distribution of the Golgi enzyme beta1, 6-N-
acetylglucosaminyltransferase (core 2 GlcNAc-T for short) has been
investigated in several tissue and cell systems by combining the potentials
of a polyclonal antibody and a novel, sensitive fluorescent enzyme assay.
In normal rat tissues, levels of the protein were found to vary and as a
general trend did not correlate with enzyme activities. Additionally, we
observed tissue-specific core 2 GlcNAc-T forms of various size: 75 kDa
(liver), 70 kDa (spleen), 60 kDA (heart), and 50 kDa (heart and lung).
These forms might arise from differential protein modifications;
alternatively, the smaller form may be a product of proteolytic cleavage,
given the presence of a catalytically inactive 50 kDa species in rat serum.
Chinese hamster ovary (CHO), MDAY-D2, PSA- 5E, and PYS-2 cell lines
consistently displayed a 70 kDa enzyme. When induced to retrodifferentiate
in the presence of butyrate + cholera toxin, CHO cells exhibited a 21-fold
increase in enzyme activity, while protein levels remained constant. A
similar trend was observed in the embryonal endoderm cell lines PSA-5E and
PYS-2, where an approximately 100-fold difference in core 2 GlcNAc-T
activity was found notwithstanding unchanged amounts of the protein and
identical mRNA levels, as evidenced by RT-PCR. In contrast, levels of core
2 GlcNAc-T activity in MDAY-D2 cells correlated well with protein
expression. Taken together, these observations demonstrate that core 2
GlcNAc-T expression may be subjected to multiple mechanisms of regulation
and suggest that in at least some instances (i.e., PSA-5E and PYS-2 cells)
expression may be regulated exclusively via posttranslational mechanism(s)
of control.
相似文献
9.
The effect of bioprocess conditions (pH and temperature) on the growth and alkaline protease production of halotolerant Bacillus licheniformis BA17 bioreactor cultures have been systematically analyzed using response surface methodology in order to assess the importance
of these generally disregarded parameters. Two models were proposed differing by the choice of response variable. Under optimized
bioprocess conditions, whole alkaline protease activity was about 3 fold higher than the activities obtained in the preliminary
studies. Results of this study not only highlight the importance of pH and temperature for further engineering purposes but
also serve as basis for understanding the true mechanism lying under the relation between these process parameters and growth
and whole alkaline protease production.
Published in Russian Prikladnaya Biokhimiya i Mikrobiologiya, 2008, Vol. 44, No. 5, pp. 539–544.
The text was submitted by the autors in English. 相似文献
10.
I Emrah Nikerel Wouter A van Winden Walter M van Gulik Joseph J Heijnen 《BMC bioinformatics》2006,7(1):540-23