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81.
The uptake of leucine through the tegument of Cotugnia digonopora, a cestode found in the fowl intestine, occurs by a process of active transport. The Kt of transport is 0.87 mM and the Vmax is 0.223 μmol/min/g. Uptake of the amino acid is competitively inhibited by valine (Kt = 1.30 mM). Potassium cyanide and 2,4-dinitrophenol do not completely block the entry of leucine into the parasite. 相似文献
82.
Some methods for measuring the uptake of sugars by yeasts were investigated critically. A study was made of the effects of starvation of Pichia pinus, Candida utilis, Saccharomyces cerevisiae and Rhodosporidium toruloides on their uptake of d-glucose and 2-deoxy-d-glucose. Marked changes in the rates of uptake of these sugars occurred during 10 h of starvation, including (a) an immediate increase of up to 75% above that for growing cells and (b) a continuous decline to as little as 4%. Each yeast behaved differently. The rates did not remain constant during the periods of starvation often used for studies on the transport of sugars into yeasts. For Pichia pinus, there were striking differences, associated with starvation, between the transport of 2-deoxy-d-glucose and d-glucose, despite evidence that the two sugars enter this yeast by means of the same carrier. Some physiological explanations for these findings are discussed. 相似文献
83.
The uptake of various amino acids into Streptomyces hydrogenans grown in chemostatically and turbidostatically controlled steady state cultures has been investigated. A close correlation between transport capacity and the growth rates of the cells was found. As shown by kinetic analysis, the increased transport is due to elevated maximum uptake rates, the apparent Michaelis constants remaining unchanged. Analysis of the unidirectional fluxes of cycloleucine revealed that not only the influx is raised as the growth rate is increased but also the efflux. Hence, the conclusion is drawn that the growth-rate dependent modulation of transport capacity is, at least, partially due to the variation of the concentration of active transport components. Since the cells were grown in the absence of external amino acids the results suggest that amino acid transport into S. hydrogenans is under the control of endogenous effectors.List of Abbreviations AIB
2-aminoisobutyric acid
- Cycloleucine
1-aminocyclopentane-1-carboxylic acid 相似文献
84.
85.
Effects of ethanol and other alkanols on passive proton influx in the yeast Saccharomyces cerevisiae
Ethanol, isopropanol, propanol and butanol enhanced the passive influx of protons into deenergized cells of Saccharomyces cerevisiae. The influx followed first-order kinetics with a rate constant that increased exponentially with the alkanol concentration. The exponential enhancement constants increased with the lipid solubility of the alkanols, which indicated hydrophobic membrane regions as the target sites. While the enhancement constants were independent of pH over the range tested (3.3–5.0), the rate constants decreased linearly with increasing extracellular proton concentration, indicating the presence of an additional surface barrier against proton penetration, the effectiveness of which increased with protonation. The alkanols affected the acidification curves of energized yeast suspensions in such a way that the final pH values were linear functions of the alkanol concentrations. These results were consistent with a balance between active and passive proton movements at the final pH, the exponential enhancement constants calculated from the slopes being nearly identical with those obtained with deenergized cells. It was concluded that passive proton influx contributes to the kinetics of acidification in S. cerevisiae and that uncoupling contributes to the overall kinetics of alkanol-inhibited secondary active transport across the yeast plasma membrane. 相似文献
86.
In the industrial l-glutamate production established on the use of Corynebacterium glutamicum, l-glutamate synthesized intracellularly is exported through mechanosensitive transmembrane channel proteins (MscCG and MscCG2) activated by the force-from-lipids. The involvement of MscCG2 in l-glutamate export by C. glutamicum was demonstrated in 2018; however, MscCG was previously found to be the major exporter of l-glutamate. Recent advances in research methods, such as development of the microbial patch clamp, revealed unique characteristics of MscCG, including its conductance, opening and closing thresholds, and gating hysteresis, as well as the significant effect of membrane lipids on the channel properties. In addition, the cryoelectron microscopic structure of Escherichia coli MscS, the canonical representative of the mechanosensitive channel family to which MscCG and MscCG2 belong, revealed its new membrane-interacting region, new position within the lipid bilayer, and hook lipids in a newly defined cavity between subunits. In this short review, the applications of bacterial mechanosensitive channels in the development of effective microbial cell factories, which will contribute to sustainable development, are discussed. 相似文献
87.
Xiaoqian Liu Yuanfeng Zhang Kaimin Li Yinghui Liu Junqing Xu Junjie Ma Licai An Hui Wang Xiaoxia Chu 《Translational oncology》2021,14(7):101085
Refractory/relapsed B cell lymphoma patients who received the available anti-CD19 chimeric antigen receptor (CAR) T cells may still experience a short duration of remission. Here in this study, we evaluated the safety and efficacy of a novel dominant-negative programmed cell death-1 (PD-1) armored anti-CD19 CAR T cells. A total of 9 patients (including 4 diffuse large B cell lymphomas, DLBCL, 2 transformed follicular lymphomas, TFL, and 3 follicular lymphomas, FL) received the novel CAR T cells infusion at a dose of more than 1 × 106/kg. Grade ≥ 3 cytokine release syndrome (CRS) and neurotoxicity were observed in 11.1% (n = 1/9) and 11.1% (n = 1/9) of patients, respectively. The overall response rate (ORR) was 77.8% (n = 7/9) and complete response (CR) rate was 55.6% (n = 5/9). Two patients have ongoing CR (all at 20+ months). CAR T cells expanded after infusion and continued to be detectable at 12+ months in patients with ongoing CR. This novel CD19-CAR T cell was safe and effective with durable remissions in patients with refractory/relapsed B cell lymphoma. 相似文献
88.
《Nucleosides, nucleotides & nucleic acids》2013,32(1-2):89-115
A conceptual extension of the cycloSal‐pronucleotide approach is presented. The characteristic feature of the new cycloSal‐derivatives of the anti‐HIV active nucleoside analogue d4T 1 is the incorporation of an enzymatically cleavable carboxylic ester moiety with the intention to trap the triesters inside cells (”lock‐in”‐concept). CycloSal‐triesters bearing different ester groups in the 3‐or 5‐position of the cycloSal‐moiety are described. Surprisingly, only acetyl‐and levulinyl esters are cleaved readily in CEM cell extracts while alkyl esters were found to be stable. Nevertheless, in in‐vitro anti‐HIV assays most of the compounds achieve the thymidine–kinase bypass, thus proving that they act at least as nucleotide delivery systems. 相似文献
89.
《Nucleosides, nucleotides & nucleic acids》2013,32(8):1209-1214
Novel racemic, d- and l-β-dioxolane N 4-hydroxycytosine nucleosides have been synthesized and evaluated for their activity against hepatitis B virus. None of the synthesized nucleosides demonstrated selective anti-HBV activity. 相似文献
90.
《Nucleosides, nucleotides & nucleic acids》2013,32(4-5):385-392
ABSTRACT Lead tetraacetate (LTA) oxidation of α-Phenyl-N-(4-biphenyl)nitrone (8) to give a new ultimate carcinogen, N-acetoxy-N-benzoyl-4-aminobiphenyl (9) which was reacted with deoxyguanosine (dG) at pH 6.9 to give nucleoside derivative, N-(benzoyl)-N-(deoxyguanosin-8-yl)-4-aminobiphenyl (10). Following debenzoylation with sodium carbonate-methanol leads to N-(2′-deoxyguanosin-8-yl)-4-aminobiphenyl (11). 相似文献