RESUMO
Succinic acid is an important C4 platform chemical that is widely used in food, chemical, medicine sectors. The bottleneck of fermentative production of succinic acid by engineered Escherichia coli is the imbalance of intracellular cofactors, which often leads to accumulation of by-products, lower yield and low productivity. Stoichiometric analysis indicated that an efficient production of succinic acid by E. coli FMME-N-26 under micro-aeration conditions might be achieved when the TCA cycle provides enough ATP and NADH for the r-TCA pathway. In order to promote succinic acid production, a serial of metabolic engineering strategies include reducing ATP consumption, strengthening ATP synthesis, blocking NADH competitive pathway and constructing NADH complementary pathway were developed. As result, an engineered E. coli FW-17 capable of producing 139.52 g/L succinic acid and 1.40 g/L acetic acid in 5 L fermenter, which were 17.81% higher and 67.59% lower than that of the control strain, was developed. Further scale-up experiments were carried out in a 1 000 L fermenter, and the titer of succinic acid and acetic acid were 140.2 g/L and 1.38 g/L, respectively.
Assuntos
Escherichia coli/genética , NAD , Ácido Succínico , Ácido Acético , Trifosfato de AdenosinaRESUMO
AIM:To investigate myosin heavy chain(MHC)gene expression and the effects of captopril and betaloc at an early stage of hypertension. METHODS:Model of hypertension was made by partly narrowing two bilateral renal arteries(2K2C). The rats were divided into four groups at random. (1) control group; (2)2K2C group;(3)captopril group;(4)betaloc group.Levels of ?-MHC and ?-MHC mRNA were determined by dot-blot. RESULTS:?-MHC mRNA expression were gradual1y reduced in 2K2C group,while ?-MHC mRNA expression were increased,and the marked changes were observed at 72h postoperation. Captopril could inhibit the changes in MHC gene expression; but betaloc could not. CONCLUSION: The expression of MHC gene has changed at an early stage of renal hypertensive rat,and renin-angiotensin system may play an important role in this change.
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AIM: To investigate the expression of B lymphocyte stimulator(BLyS) and CD38 molecules on peripheral blood lymphocytes of patients with systemic lupus erythematosus(SLE). METHODS: Twenty-two patients with SLE and fourteen healthy subjects entered the study. Isolated peripheral blood lymphocyte were stained for the lymphocyte surface markers BLyS, CD19, and CD38, and then was measured by flow cytometry(FACS). RESULTS: BLyS + lymphocytes, CD19 + lymphocytes, and CD19 +CD38 + lymphocytes were increased significantly in patients with SLE( P
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AIM: To study the roles and mechanisms of ERKs and intracellular free calcium in cardiomyocyte hypertrophic response induced by endothelin-1(ET-1). METHODS: (1) Neonatal rat cardiomyocyte hypertrophic response was assayed by measuring cell surface area and protein content; (2) ERKs activity was determined by Whatman Paper Filter method; (3) Intracellular free calcium concentration ([Ca 2+ ]i) was measured using Fura-2/AM as a fluorescent indicator. RESULTS: (1) ET-1 could increase total protein production, surface area, ERKs activity and [Ca 2+ ]i in cultured cardiomyocyte in dose-dependent manner at concentrations ranging from 10 -9 to 10 -7 mol/L. And this effect could be abolished by BQ123, an antagonist of ET A receptor, partly inhibited by PTX, but not by BQ788, an antagonist of ET B receptor.(2)The activation of ERKs and the increase of [Ca 2+ ]i induced by ET-1 were obviously inhibited by PD98059, a selective ERKs kinase inhibitor, and nifedipine, a calcium channel blocker, respectively. Both antagonists partially inhibited ET-1-stimulated cardiomyocyte hypertrophic response. (3) Staurosporine, a selective PKC inhibitor, could inhibit ET-1-stimulated cardiomyocyte hypertrophic response and increase of [Ca 2+ ]i, but not affect the activation of ERKs. CONCLUSION: Cardiomyocyte hypertrophic response induced by ET-1 is mediated by ET A receptor coupled to PTX-sensitive G-protein, which involves at least two signalling pathways: PKC-mediated increase of [Ca 2+ ]i , and PKC-independent activation of ERKs. [
