Hypercholesteremia was induced by cholesterol feeding of rabbits for 10 weeks. Gross examination of aorta of these animals showed an evidence of atheromatous lesions. The endogenous catecholamines in heart, adrenal gland, spleen, brain, liver and kidney of these hypercholesteremic rabbits were markedly reduced as compared to those of normal animals, respectively. There may exist some correleration between the serum cholesterol and tissue catecholamines.
Animal ; Arteriosclerosis/etiology* ; Arteriosclerosis/metabolism ; Carbon Isotopes ; Catecholamines/metabolism* ; Cholesterol/blood* ; Female ; Rabbits

Intracellular metabolic fluxes are important to understand metabolic characteristics of cells and to direct metabolic engineering strategies. Because intracellular fluxes cannot be directly assessed, isotope experiments are usually conducted to trace metabolic fluxes. The flux-ratio analysis can reflect high biochemical veracity, be employed to identify the topology of the networks, and offer greatly reduced computational expense for flux determination. In order to apply this metabolic analysis method to better elucidate more cell systems, we discussed in this study the principles, experiments and assays, data interpretation, and other issues that should be considered in flux ratio determination, metabolic flux quantification and its metabolic engineering applications.
Carbon Isotopes ; Cells ; metabolism ; Genetic Engineering ; Humans ; Isotope Labeling ; Metabolic Networks and Pathways ; Metabolism ; Spectrum Analysis

The aim of this study is to develop a synthetic medium suitable for 13C metabolic flux analysis (13C-MFA) of Streptomyces rimosus. The cell growth rate and oxytetracycline production by S. rimosus M4018 were compared when M4018 cells were growth on the optimized chemically defined media with organic nitrogen sources or inorganic nitrogen sources. First, a synthetic medium contained KNO3 as the main nitrogen source was screened, then optimized by a response surface method. Using this new medium, the oxytetracycline yield was increased from 75.2 to 145.6 mg/L. Furthermore, based on the 13C-MFA, we identified that Entner-Doudoroff pathway does not exist in S. rimosus cells cultured in a chemically defined medium with feed of 100% 1-13C labeled glucose. This study is helpful for subsequent 13C-MFA application of S. rimosus.
Carbon Isotopes ; analysis ; Culture Media ; chemistry ; Metabolic Flux Analysis ; Nitrogen ; chemistry ; Oxytetracycline ; biosynthesis ; Streptomyces rimosus ; metabolism

Stable isotope ¹³C labeling is an important tool to analyze cellular metabolic flux. The ¹³C distribution in intracellular metabolites can be detected via mass spectrometry and used as a constraint in intracellular metabolic flux calculations. Then, metabolic flux analysis algorithms can be employed to obtain the flux distribution in the corresponding metabolic reaction network. However, in addition to carbon, other elements such as oxygen in the nature also have natural stable isotopes (e.g., ¹⁷O, ¹⁸O). This makes the isotopic information of elements other than the ¹³C marker interspersed in the isotopic distribution measured by the mass spectrometry, especially that of the molecules containing many other elements, which leads to large errors. Therefore, it is essential to correct the mass spectrometry data before performing metabolic flux calculations. In this paper, we proposed a method for construction of correction matrix based on Python language for correcting the measurement errors due to natural isotope distribution. The method employed a basic power method for constructing the correction matrix with simple structure and easy coding implementation, which can be directly applied to data pre-processing in ¹³C metabolic flux analysis. The correction method was then applied to the intracellular metabolic flux analysis of ¹³C-labeled Aspergillus niger. The results showed that the proposed method was accurate and effective, which can serve as a reliable data correction method for accurate microbial intracellular metabolic flux analysis.
Metabolic Flux Analysis ; Isotope Labeling/methods* ; Carbon Isotopes/metabolism* ; Mass Spectrometry/methods* ; Metabolic Networks and Pathways

Gene expression is regulated by different transcriptional regulators. The transcriptional regulator isocitrate lyase regulator (IclR) of Escherichia coli represses the expression of the aceBAK operon that codes for the glyoxylate pathway enzymes. In this study, physiological and metabolic responses of the deletion of the ic1R gene in E. coli BW25113 were investigated based on the quantification and analysis of intracellular metabolic fluxes. The knockout of the iclR gene resulted in a decrease in the growth rate, glucose uptake rate and the acetate secretion rate, but a slight increase in biomass yield. The latter could be attributed to the lowered metabolic fluxes through several CO2 generating pathways, including the redirection of 33% of isocitrate directly to succinate and malate without CO2 production as well as the reduced flux through the pentose phosphate pathway. Furthermore, although the glyoxylate shunt was activated in the iclR mutant, the flux through phosphoenolpyruvate (PEP) carboxykinase kept almost unchanged, implying an inactive PEP-glyoxylate cycle and no extra loss of carbon atoms in the mutant strain. Both the reduced glucose uptake rate and the active glyoxylate shunt were responsible for the minor decrease in acetate secretion in the ic1R knockout strain compared to that in the wild-type E. coli strain.
Carbon Isotopes ; metabolism ; Escherichia coli ; enzymology ; genetics ; Escherichia coli Proteins ; genetics ; metabolism ; Gene Knockout Techniques ; Isocitrate Lyase ; genetics ; metabolism ; Metabolic Networks and Pathways ; genetics ; Repressor Proteins ; genetics ; metabolism

Acetamides ; pharmacokinetics ; Adult ; Aged ; Breath Tests ; methods ; Carbon Isotopes ; pharmacokinetics ; Female ; Humans ; Liver Cirrhosis ; blood ; diagnosis ; physiopathology ; Liver Function Tests ; methods ; Male ; Middle Aged ; Reproducibility of Results ; Serum Albumin ; metabolism