排序方式: 共有66条查询结果,搜索用时 15 毫秒
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David J Sewell Richard Turner Ray Field William Holmes Rahul Pradhan Christopher Spencer Stephen G Oliver Nigel KH Slater Duygu Dikicioglu 《Biotechnology and bioengineering》2019,116(6):1315-1325
Without a scale-down model for perfusion, high resource demand makes cell line screening or process development challenging, therefore, potentially successful cell lines or perfusion processes are unrealized and their ability untapped. We present here the refunctioning of a high-capacity microscale system that is typically used in fed-batch process development to allow perfusion operation utilizing in situ gravity settling and automated sampling. In this low resource setting, which involved routine perturbations in mixing, pH and dissolved oxygen concentrations, the specific productivity and the maximum cell concentration were higher than 3.0 × 106 mg/cell/day and 7 × 10 7 cells/ml, respectively, across replicate microscale perfusion runs conducted at one vessel volume exchange per day. A comparative analysis was conducted at bench scale with vessels operated in perfusion mode utilizing a cell retention device. Neither specific productivity nor product quality indicated by product aggregation (6%) was significantly different across scales 19 days after inoculation, thus demonstrating this setup to be a suitable and reliable platform for evaluating the performance of cell lines and the effect of process parameters, relevant to perfusion mode of culturing. 相似文献
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Seol CA Kim WT Ha JM Choe H Jang YJ Youm JB Earm YE Leem CH 《Progress in biophysics and molecular biology》2008,97(2-3):217-231
Evidence is growing of a relationship between atrial dilation and atrial fibrillation (AF), the most prevalent type of arrhythmia. Pulmonary veins, which are important ectopic foci for provoking AF, are of increasing interest in relation to the early development of AF. Here, using single cardiomyocytes isolated from rabbit pulmonary veins, we characterised the stretch-activated currents induced by swelling and axial mechanical stretching. Swelling induced both a stretch-activated nonselective cationic current (NSC) and a Cl(-) current. The swelling-induced Cl(-) current (I Cl,swell) was inhibited by DIDS, whereas the swelling-induced NSC (I NSC,swell) was inhibited by Gd3+. The cationic selectivity of the I NSC,swell was K+ >Cs+ >Na+ >Li+, whilst the PK/PNa, PCs/PNa, and PLi/PNa permeability ratios were 2.84, 1.86, and 0.85, respectively. Activation of the I NSC,swell was faster than that of the I Cl,swell. Given a high K+ concentration in the bath solution, the I NSC,swell showed limited amplitude (<-70 mV). Mechanical stretching induced an immediate Gd3+- and streptomycin-sensitive NSC (I NSC,stretch) that was permeable to Na+, K+, Cs+ and NMDG. Persistent stretching activated a DIDS-sensitive current (I Cl,stretch). The I NSC,stretch, but not the I NSC,swell, was completely blocked by 400 microM streptomycin; therefore, the two currents may not be associated with the same channel. In addition, the type of current induced may depend on the type of stretching. Thus, stretch-induced anionic and cationic currents are functionally present in the cardiomyocytes of the main pulmonary veins of rabbits, and they may have pathophysiological roles in the development of AF under stretched conditions. 相似文献
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To investigate the kinetics of the inward Na-Ca exchange tail current activated by internal calcium in rabbit atrial cells, the whole-cell patch-clamp technique with intracellular perfusion was used. We recorded the inward phase of this current during repolarizations following a brief 2-5 ms depolarizing pulse to +40 mV from a holding potential of -70 mV. Peak activation of the current occurs about 10 ms from the beginning of the depolarizing pulse, and it decays spontaneously with a slow timecourse. The voltage dependence of the process that activates the inward current from -40 mV to +40 mV has a very steep slope between -40 and -20 mV and then virtually saturates between -10 mV and +40 mV. The voltage dependence of the process that activates the inward current is steeper than that which activates the sarcolemmal calcium current, iCa.L, and the timecourse of the current relaxation is much slower at low-frequency stimulation and when using low concentrations of Ca-buffer. The magnitude and timecourse of the calcium transients estimated by the inward tail current are smaller and faster, and the slow component of decay was abolished by the presence of high intracellular concentrations of Ca-buffer or by high frequency stimulation. These observations suggest that calcium release from the sarcoplasmic reticulum may be triggered by only a small fraction of the sarcolemmal calcium current. 相似文献
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M. A. KH. MOUNLA 《Physiologia plantarum》1978,44(3):268-272
In husks, the activity of gibberellin-like substances extracted with aqueous methanol (M-“free” GAs) showed a maximum on the 9th day after pollination. In developing embryos, M-“free” GAs showed no biological activity, whereas biological active component(s) were obtained when the embryos were extracted with Tris buffer. The “free” GAs found in the buffer homogenates (B-“free” GAs) of developing embryos showed a maximum of activity on the 33rd day after pollination. Bound GAs recovered from the precipitated protein of the buffer homogenate (“Protein-bound” GAs) were found in embryo and endosperm. Developing endosperm generally contains the major amount of the extractable gibberellin-like substances. In this tissue, the amount of all examined fractions (M-“free” GAs, B-“free” GAs and “protein-bound” GAs) increased after pollination to reach a maximum on the 21st day, before decreasing to a minimum at grain maturity. Moreover, the curves for dry weight increase and gibberellin like substances follow a remarkably similar course, with the latter reaching its maximim slightly earlier than the former one. This result indicates that gibberellines may participate in the regulation of the accumulation process in the endosperm of barley grain. 相似文献
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We employed a genetic approach to study protein glycosylation in the
procyclic form of the parasite Trypanosoma brucei. Two different mutant
parasites, ConA 1-1 and ConA 4-1, were isolated from mutagenized cultures
by selecting cells which resisted killing or agglutination by concanavalin
A. Both mutant cells show reduced concanavalin A binding. However, the
mutants have different phenotypes, as indicated by the fact that ConA 1-1
binds to wheat germ agglutinin but ConA 4-1 and wild type do not. A blot
probed with concanavalin A revealed that many proteins in both mutants lost
the ability to bind this lectin, and the blots resembled one of wild type
membrane proteins treated with PNGase F. This finding suggested that the
mutants had altered asparagine- linked glycosylation. This conclusion was
confirmed by studies on a flagellar protein (Fla1) and procyclic acidic
repetitive protein (PARP). Structural analysis indicated that the N- glycan
of wild type PARP is exclusively Man5GlcNAc2 whereas that in both mutants
is predominantly a hybrid type with a terminal N- acetyllactosamine. The
occupancy of the PARP glycosylation site in ConA 4-1 was much lower than
that in ConA 1-1. These mutants will be useful for studying trypanosome
glycosylation mechanisms and function.
相似文献
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Sun Park W Kyoung Son Y Kim N Boum Youm J Joo H Warda M Ko JH Earm YE Han J 《Biochemical and biophysical research communications》2006,340(4):1104-1110
The effects of the protein kinase A (PKA) inhibitor H-89 on ATP-sensitive K+ (KATP) and inward rectifier K+ (Kir) currents were examined in rabbit coronary arterial smooth muscle cells using the patch clamp technique. The H-89, in a dose-dependent manner, inhibited KATP and Kir currents with apparent Kd values of 1.19+/-0.18 and 3.78+/-0.37 microM, respectively. H-85, which is considered as an inactive form of H-89, inhibited KATP and Kir currents, similar to the result of H-89. KATP and Kir currents were not affected by either Rp-8-CPT-cAMPs, which is a membrane-permeable selective PKA inhibitor, or KT 5720, which is also known as a PKA inhibitor. Also, these two drugs did not significantly alter the effects of H-89 on the KATP and Kir currents. These results suggest that H-89 directly inhibits the KATP and Kir currents of rabbit coronary arterial smooth muscle cells independently of PKA inhibition. 相似文献
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Son YK Park WS Kim SJ Earm YE Kim N Youm JB Warda M Kim E Han J 《Biochemical and biophysical research communications》2006,341(4):931-937
We examined the effects of the protein kinase A (PKA) inhibitor H-89 on voltage-dependent K(+) (K(V)) currents in freshly isolated rabbit coronary arterial smooth muscle cells, using a whole-cell patch clamp technique. H-89 inhibited the K(V) current in a concentration-dependent manner, with a K(d) value of 1.02 microM. However, the PKA inhibitors KT 5720 and Rp-8-CPT-cAMPS did not significantly alter the K(V) current or the inhibitory effects of H-89 on the K(V) current. Moreover, H-85, a structurally similar but inactive analog of H-89, showed similar inhibitory effects on the K(V) channel. H-89 had no effect on the voltage-dependency of activation or inactivation, or on recovery kinetics. These results suggest that in rabbit coronary arterial smooth muscle cells, H-89 inhibits the K(V) current directly by blocking the pore cavity, an effect independent of PKA inhibition. 相似文献