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Due to research on biochemistry and genetic engineering, mathematical models of microbial growth have become more complicated but Michaelis-Menten or Monod type expressions have still been used for conversion rates, uptake rates, etc. It is worth examining the error that can be caused by these quasi-steady-state-hypotheses. This paper presents a simple but very effective rationale function that describes the error of the quasi-steady-state hypothesis in enzyme kinetics. A simplified fermentation kinetic model was used for comparison of microbial growth but no analytical error function has been found for batch cultivation. In the case of continuous fermentation the error can be given in an analytical form. Many simulations, based on real SCP experiments, show a significant effect of the quasi-steady-state hypothesis. Since the rate constants of intracellular events are not really known, we have to be very careful when taking into account Michaelis-Menten type expressions in the building of complicated models.
Correspondence to: L. Szigeti 相似文献
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Silvia Penuela Alexander W Lohman Wesley Lai Laszlo Gyenis David W Litchfield Brant E Isakson Dale W Laird 《Channels (Austin, Tex.)》2014,8(2):124-130
The pannexin family of channel-forming proteins is composed of 3 distinct but related members called Panx1, Panx2, and Panx3. Pannexins have been implicated in many physiological processes as well as pathological conditions, primarily through their function as ATP release channels. However, it is currently unclear if all pannexins are subject to similar or different post-translational modifications as most studies have focused primarily on Panx1. Using in vitro biochemical assays performed on ectopically expressed pannexins in HEK-293T cells, we confirmed that all 3 pannexins are N-glycosylated to different degrees, but they are not modified by sialylation or O-linked glycosylation in a manner that changes their apparent molecular weight. Using cell-free caspase assays, we also discovered that similar to Panx1, the C-terminus of Panx2 is a substrate for caspase cleavage. Panx3, on the other hand, is not subject to caspase digestion but an in vitro biotin switch assay revealed that it was S-nitrosylated by nitric oxide donors. Taken together, our findings uncover novel and diverse pannexin post-translational modifications suggesting that they may be differentially regulated for distinct or overlapping cellular and physiological functions. 相似文献
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Judit Kapocsi George T. Somogyi Nandor Ludvig Peter Serfozo Laszlo G. Harsing Jr. Russell J. Woods E. Sylvester Vizi 《Neurochemical research》1987,12(2):141-147
Neurochemical and pharmacological evidence has been obtained that noradrenergic varicosities (in mouse and rat vas deferens) and cholinergic varicosities (in the Auerbach's plexus) contain heterogenous alpha2-adrenoceptors through which the release of [3H]noradrenaline and [3H]acetylcholine can be modulated. The quantitative data also support the hypothesis that different noradrenaline and xylazine sensitive alpha2-adrenoceptors are present prejunctionally in the vas deferens and Auerbach's plexus preparations. Prazosin, although it has a presynaptic inhibitory effect on alpha2-adrenoceptors of noradrenergic axon terminals, has no effect on cholinergic axon terminals. These data suggest that there are two different types of alpha2-adrenoceptors at the presynaptic axon terminals.Special Issue Dedicated to Dr. Abel Lajtha 相似文献
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Ubiquitin-protein conjugates accumulate in the lysosomal system of fibroblasts treated with cysteine proteinase inhibitors. 总被引:2,自引:0,他引:2 下载免费PDF全文
F J Doherty N U Osborn J A Wassell P E Heggie L Laszlo R J Mayer 《The Biochemical journal》1989,263(1):47-55
Mouse fibroblasts (3T3-L1 cells) accumulate detergent- and salt-insoluble aggregates of proteins conjugated to ubiquitin when incubated in the presence of inhibitors of lysosomal cysteine cathepsins, including E-64. These ubiquitin-protein conjugates co-fractionate with lysosomes on density gradients and are found in multivesicular dense bodies which by electron microscopy appear to be engaged in microautophagy. Both E-64 and ammonium chloride increase the intracellular concentration of free ubiquitin, but only E-64 leads to the formation of insoluble lysosomal ubiquitin-protein conjugates. The results are discussed in relation to the possible intracellular roles of ubiquitin conjugation. 相似文献
8.
Behavioral effects of somatostatin-14, and some of its fragments [somatostatin(3–8), somatostatin(9–14), somatostatin(7–10)] after intracerebroventricular (ICV) administration have been investigated in male rats. In a passive avoidance learning test, somatostatin-14 (0.6 nM) given immediately after the learning session increased the avoidance latency at 24 hr after the injection, when compared to a somatostatin(3–8) (0.6 nM)-treated group. However, compared to a saline-treated group, the peptides did not significantly influence the avoidance latency. Somatostatin-14 administered in higher dose (6.0 nM) decreased the avoidance latency compared to the saline-treated group, while its fragments did not influence it. In an open field behavioral test, immediately after the 24-hr passive avoidance test, 6 nM of somatostatin-14 decreased the rearing activity, while the fragments did not influence this behavior. Somatostatin-14 produced barrel rotation in a dose-related manner, but after the injection of a high dose of the peptide (12 nM) all of the animals died in cardiorespiratory failure (apnea, pulmonary oedema). The fragments did not produce barrel rotation. 相似文献
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BG-104 is a compound of Chinese herbs which were treated with infrared ray-heating and brewed with microorganisms resulting in activation of actual principles contained in the herbs, and its effectiveness has been reported on various inflammatory disorders such as Behcet's disease, rheumatoid arthritis, bacterial infections and so on. In addition, it is noted as an effective agent to retard cancer progress. This report shows a superoxide scavenging activity of BG-104 using an ESR spin trapping method. For the measurement of superoxide scavenging activity, recombinant human superoxide dismutase is used as a standard. Superoxide scavenging activity of BG-104 increases in a dose-dependent manner and activity is significantly augmented by its sonication. 相似文献
10.
Heat shock proteins within the mammalian cell cycle: relationship to thermal sensitivity, thermal tolerance, and cell cycle progression 总被引:1,自引:0,他引:1
We have measured endogenous and induced rates of 70-kD, 89-kD, and 110-kD heat shock proteins in highly pure G1-, S-, or G2-M phase fractions of Chinese hamster fibroblasts (CHO) separated by fluorescence-activated cell sorting (FACS). Relative rates of synthesis of all three polypeptides as measured by two-dimensional gel electrophoresis were similar throughout the cell cycle, and therefore, endogenous levels were unlikely to explain the thermal sensitivity of S-phase cells. Distinct heterogeneity in induced rates of these polypeptides was noted in all phase fractions. Enhanced rates of 70-kD polypeptide were measured in S and G2-M as compared to G1 following heat shock. Little increase in either the 89-kD or 110k-kD heat shock proteins was observed in heated G1 cells. This heterogeneity in induced rates of synthesis was in contrast to the similarity in thermal tolerance expression kinetics between each phase. Finally, enhanced synthesis of these polypeptides appeared unrelated to regulation of either heat-induced cell cycle delay or to the resumption of phase-specific progression after heat shock as measured by simultaneous flow cytometric measurement of incorporated BrdUrd and DNA content. 相似文献