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1.
The mechanism of 13C-methacetin breath test is set forth clearly with the analysis of pharmacokinetics mode, and the measuring method of 13C-methacetin breath test and its clinical applications in the diagnosis of liver diseases are reported in detail. On the basis of comprehensive analysis of the clinical test data, the advanced diagnostic parameter S is of important significance for the application and development of breath test.  相似文献   

2.
A differential kinetic study of 13CO2 enrichment of breath after the intake of specific 13C-labelled substrates and co-administration of a drug allows the drug's ability for enzyme induction to be evaluated in vivo. A method and a gas chromatograph—isotope ratio mass spectrometer device for on-line measurements of 13CO2 enrichment in the breath of small animals are described. This system allows on-line breath sample collection from a metabolic cage, purification by gas chromatography, determination of CO2 by thermal conductivity detection and measurement of 13CO2 enrichment by isotope ratio mass spectrometry. Two protocols for phenobarbital-inducible P450 and 3-methylcholanthrene-inducible P1-450 isoenzymes are described.  相似文献   

3.
Most heterotrophic bacteria assimilate CO2 in various carboxylation reactions during biosynthesis. In this study, assimilation of 14CO2 by heterotrophic bacteria was used for isotope labeling of active microorganisms in pure cultures and environmental samples. Labeled cells were visualized by microautoradiography (MAR) combined with fluorescence in situ hybridization (FISH) to obtain simultaneous information about activity and identity. Cultures of Escherichia coli and Pseudomonas putida assimilated sufficient 14CO2 during growth on various organic substrates to obtain positive MAR signals. The MAR signals were comparable with the traditional MAR approach based on uptake of 14C-labeled organic substrates. Experiments with E. coli showed that 14CO2 was assimilated during both fermentation and aerobic and anaerobic respiration. The new MAR approach, HetCO2-MAR, was evaluated by targeting metabolic active filamentous bacteria, including “Candidatus Microthrix parvicella” in activated sludge. “Ca. Microthrix parvicella” was able to take up oleic acid under anaerobic conditions, as shown by the traditional MAR approach with [14C]oleic acid. However, the new HetCO2-MAR approach indicated that “Ca. Microthrix parvicella,” did not significantly grow on oleic acid under anaerobic conditions with or without addition of NO2, whereas the addition of O2 or NO3 initiated growth, as indicated by detectable 14CO2 assimilation. This is a metabolic feature that has not been described previously for filamentous bacteria. Such information could not have been derived by using the traditional MAR procedure, whereas the new HetCO2-MAR approach differentiates better between substrate uptake and substrate metabolism that result in growth. The HetCO2-MAR results were supported by stable isotope analysis of 13C-labeled phospholipid fatty acids from activated sludge incubated under aerobic and anaerobic conditions in the presence of 13CO2. In conclusion, the novel HetCO2-MAR approach expands the possibility for studies of the ecophysiology of uncultivated microorganisms.  相似文献   

4.
Background: Endogenous CO2 production may be a possible explanation for higher false‐positive results reported for 13C‐urea breath test (UBT) in children below 6 years. In this study, we evaluated whether age affects the diagnostic accuracy of the 13C‐UBT even after the application of urea hydrolysis rate (UHR) in children. Methods: A total of 612 13C‐UBTs and endoscopic biopsies were performed on children divided into two groups; children under 6 years (n = 126) and children aged 6–18 years (n = 486). For 13C‐UBT, 75 mg 13C‐urea was ingested, and breath sample was collected 30 minutes later. Delta over baseline (DOB) was determined, and UHR was calculated to normalize the DOB values for endogenous CO2 production. Results: There was significant difference between the DOB values of children under 6 years and those of children over 6 years in H. pylori‐positive (p = .029) and ‐negative groups (p = .002). On applying the UHR, no significant difference was observed between the UHR values of children under 6 years and those of children over 6 years in H. pylori‐positive (p = .877) and ‐negative groups (p = .427). In 12.6% children under 6 years, false‐positive results were observed on applying the DOB, and in 9.0% on applying the UHR (p = .125). Conclusions: The 13C‐UBT is a noninvasive method exhibiting high diagnostic accuracy with both UHR as well as DOB. However, high false‐positive results for 13C‐UBT were noted in children below 6 years on applying both UHR as well as DOB. Thus, this may not only be due to the effects of endogenous CO2 production but also due to other factors.  相似文献   

5.
Ultrasound investigations (USI) of the liver, organs and vessels of the gastroduodenal area, as well as blood biochemistry, were performed in two groups of male volunteers on the 4th day of their stay in the conditions of “dry” immersion with and without the application of countermeasures, including the support load imitator (SLI) or high-frequency electromyostimulation. Using 13С-methacetin breath test (13C-MBT), two other groups were investigated for the effect of immersion on the detoxification activity and metabolic capacity of the liver and the efficacy of SLI. The performed USIs have identified deceleration in the hepatic venous flow and the signs of plethora in the abdominal venous system. Elevated blood levels were detected in pepsinogen, pancreatic amylase, bilirubin total, due to its unconjugated fraction, insulin, and C-peptide. The 13C-MBT has shown a slowdown in the rate of 13C-methacetin inactivation and a reduction in the hepatic metabolic capacity. The application of countermeasures during the immersion has not affected the ultrasound patterns of the hemodynamic rearrangement in both the liver and the abdomen. High frequency electromyostimulation during the immersion has neutralized the changes in all biochemical indicators except C-peptide, while the application of SLI has led to the restoration of only pepsinogen and amylase to the initial values. In addition, the use of SLI during the immersion counteracted the reduction in the 13C-methacetin inactivation rate and did not substantially affect the reduction in the metabolic capacity of the liver.  相似文献   

6.

Background

Pathogen-specific metabolic pathways may be detected by breath tests based on introduction of stable isotopically-labeled substrates and detection of labeled products in exhaled breath using portable infrared spectrometers.

Methodology/Principal Findings

We tested whether mycobacterial urease activity could be utilized in such a breath test format as the basis of a novel biomarker and diagnostic for pulmonary TB. Sensitized New-Zealand White Rabbits underwent bronchoscopic infection with either Mycobacterium bovis or Mycobacterium tuberculosis. Rabbits were treated with 25 mg/kg of isoniazid (INH) approximately 2 months after infection when significant cavitary lung pathology was present. [13C] urea was instilled directly into the lungs of intubated rabbits at selected time points, exhaled air samples analyzed, and the kinetics of δ13CO2 formation were determined. Samples obtained prior to inoculation served as control samples for background 13CO2 conversion in the rabbit model. 13CO2, from metabolic conversion of [13C]-urea by mycobacterial urease activity, was readily detectable in the exhaled breath of infected rabbits within 15 minutes of administration. Analyses showed a rapid increase in the rate of 13CO2 formation both early in disease and prior to treatment with INH. Following INH treatment, all evaluable rabbits showed a decrease in the rate of 13CO2 formation.

Conclusions/Significance

Urea breath testing may provide a useful diagnostic and biomarker assay for tuberculosis and for treatment response. Future work will test specificity for M. tuberculosis using lung-targeted dry powder inhalation formulations, combined with co-administering oral urease inhibitors together with a saturating oral dose of unlabeled urea, which would prevent the δ13CO2 signal from urease-positive gastrointestinal organisms.  相似文献   

7.
Wood-grown cultures of Daldinia concentrica oxidized a permethylated β-14C-labeled synthetic lignin to 14CO2 and also cleaved a permethylated α-13C-labeled synthetic lignin to give Cα-Cβ cleavage products that were detected by 13C nuclear magnetic resonance spectrometry. Therefore, this ascomycete resembles white-rot basidiomycetes in attacking the recalcitrant nonphenolic structures that predominate in lignin.  相似文献   

8.
Stemler A 《Plant physiology》1980,65(6):1160-1165
High concentrations of both bicarbonate and formate inhibit photosynthetic O2 evolution at pH 8.0. At this pH, only 2.4% of the total dissolved carbon dioxide exists as CO2. At pH 7.3, where 11% of the total dissolved carbon dioxide exists as CO2, HCO3 no longer inhibits. While formate still inhibits O2 evolution at pH 7.3, its effect can be partially overcome if CO2 is also present. The rate of binding of added 14C-labeled inorganic carbon is nearly 10-fold more rapid when the internal pH of thylakoid membranes is at 6.0 than when it is at 7.8. These observations suggest that CO2, not HCO3, is initially bound to the photosystem II reaction center and that the location of the binding site is on the inside thylakoid surface. However, additional data presented here suggest that, after binding, CO2 is hydrated to HCO3 + H+ in a pH-dependent reaction. Two possible explanations of the “bicarbonate effect” are presented.  相似文献   

9.
10.
Flooded rice fields are an important source of the greenhouse gas CH4. Possible carbon sources for CH4 and CO2 production in rice fields are soil organic matter (SOM), root organic carbon (ROC) and rice straw (RS), but partitioning of the flux between the different carbon sources is difficult. We conducted greenhouse experiments using soil microcosms planted with rice. The soil was amended with and without 13C-labeled RS, using two 13C-labeled RS treatments with equal RS (5 g kg−1 soil) but different δ13C of RS. This procedure allowed to determine the carbon flux from each of the three sources (SOM, ROC, RS) by determining the δ13C of CH4 and CO2 in the different incubations and from the δ13C of RS. Partitioning of carbon flux indicated that the contribution of ROC to CH4 production was 41% at tillering stage, increased with rice growth and was about 60% from the booting stage onwards. The contribution of ROC to CO2 was 43% at tillering stage, increased to around 70% at booting stage and stayed relatively constant afterwards. The contribution of RS was determined to be in a range of 12–24% for CH4 production and 11–31% for CO2 production; while the contribution of SOM was calculated to be 23–35% for CH4 production and 13–26% for CO2 production. The results indicate that ROC was the major source of CH4 though RS application greatly enhanced production and emission of CH4 in rice field soil. Our results also suggest that data of CH4 dissolved in rice field could be used as a proxy for the produced CH4 after tillering stage.  相似文献   

11.
Microalgae have the ability to convert inorganic compounds into organic compounds. When they are cultured in the presence of stable (non-radioactive) isotopes (i.e.13CO2,15NO 3 ,2H2O) their biomass becomes labeled with the stable isotopes, and a variety of stable isotopically-labeled compounds can be extracted and purified from that biomass.Two applications for stable isotopically-labeled compounds are as cell culture nutrients and as breath test diagnostics. Bacteria that are cultured with labeled nutrients will produce bacterial products that are labeled with stable isotopes. The presence of these isotopes in the bacterial products, along with recent developments in NMR technology, greatly reduces the time and effort required to determine the three-dimensional structure of macromolecules and the interaction of proteins with ligands. As breath test diagnostics, compounds labeled with13C are used to measure the metabolism of particular organs and thus diagnose various disease conditions. These tests are based on the principle that a particular compound is metabolized primarily by a single organ, and when that compound is labeled with13C, the appearance of13CO2 in exhaled breath provides information about the metabolic activity of the target organ. Tests of this type are simple to perform, non-invasive, and less expensive than many conventional diagnostic procedures.The commercialization of stable isotopically labeled compounds requires that these compounds be produced in a cost-effective manner. Our approach is to identify microalgal overproducers of the desired compounds, maximize the product content of those organisms, and purify the resulting products.  相似文献   

12.
A single-breath CO2 test of peripheral chemosensitivity has recently been described, and elaborated based on model simulations. This study was designed to measure the peripheral CO2 chemoreflex at rest and during heavy exercise to see if carotid chemosensitivity to CO2 increased. Ten healthy, adult males performed an incremental exercise test to determine their ventilatory anaerobic threshold (VAT), and 20 minutes of steady-state exercise at a pre-determined power output above VAT. Arterialized venous blood was obtained during each minute of incremental exercise to verify development of metabolic acidosis. Carotid chemosensitivity was tested repeatedly at rest and in steady-state exercise by the ventilatory response to a single breath of 13% CO2 in air. The peripheral chemoreflex for CO2 for the group of subjects doubled from rest to exercise (mean 0.0961 · s–1 · kPa–1) with all subjects showing an increase. We conclude that the gain of the carotid CO2 chemoreflex increases from rest to exercise at work above the VAT.  相似文献   

13.
The catabolism of propane by “Nocardia paraffinicum” (Rhodococcus rhodochrous) has been shown to involve CO2 fixation after its oxidation to propionic acid. “N. paraffinicum” failed to grow on either propane or 1-propanol in the absence of CO2. The rate of propane utilization was directly related to the initial CO2 concentration, and Warburg respirometry suggested that CO2 was required for the catabolism of 1-propanol, propionaldehyde, and propionate but not for 2-propanol. These data also suggested that the predominant pathway for the utilization of propane by “N. paraffinicum” was through 1-propanol. The use of [2-14C]propane and 14CO2 confirmed the catabolism of propane and the fixation of CO2. Through the use of these isotopes and the pyruvate carboxylase inhibitor sodium arsenite, the labeled 2,4-dinitrophenylhydrazine derivative of pyruvate was trapped and isolated via thin-layer chromatography. The trapping of [14C]pyruvate in this manner was considered to be indicative of the presence of the methylmalonyl coenzyme A pathway for CO2 fixation.  相似文献   

14.
Excised shoots and cell-free extracts prepared from Wedgwood iris (Iris hollandica Hoog. “Wedgwood”) shoots metabolized 14C-labeled mevalonic acid (MVA). By using cell-free extracts, the 14C from MVA-1-14C was recovered as 14CO2, while that from MVA-2-14C was recovered as neutral terpenes, acid-hydrolyzable terpenes, or 14CO2. Also, under optimal incubation conditions, 12.8 nanomoles R-MVA-2-14C was incorporated into neutral terpenes per milligram fresh weight per hour. In contrast, excised shoots incorporated only 0.58 nanomoles R-MVA-2-14C per mg fresh weight per hour. Labeled products identified from the cell-free system were squalene, farnesol, geranylgeraniol, and compounds that are converted to farnesol and geranylgeraniol after alkaline hydrolysis. Squalene and a 4,4-dimethylsterol were identified as products from excised shoots but not the terpene alcohols or the alkaline-hydrolyzable compounds.  相似文献   

15.
16.
Single attached leaves of sunflower (Helianthus annus L. “Mennonite”) were supplied 14CO2 of constant specific radioactivity in gas mixtures containing various CO2 and O2 concentrations. The 14CO2 and CO2 fluxes were measured concurrently in an open system using an ionization chamber and infrared gas analyzer.  相似文献   

17.
A dense population of the phototrophic consortium “Pelochromatium roseum” was investigated in the chemocline of a temperate holomictic lake (Lake Dagow, Brandenburg, Germany). Fluorescence in situ hybridization revealed that the brown epibionts of “P. roseum” constituted up to 37% of the total bacterial cell number and up to 88% of all green sulfur bacteria present in the chemocline. Specific amplification of 16S rRNA gene fragments of green sulfur bacteria and denaturing gradient gel electrophoresis fingerprinting yielded a maximum of four different DNA bands depending on the year of study, indicating that the diversity of green sulfur bacteria was low. The 465-bp 16S rRNA gene sequence of the epibiont of “P. roseum” was obtained after sorting of individual consortia by micromanipulation, followed by a highly sensitive PCR. The sequence obtained represents a new phylotype within the radiation of green sulfur bacteria. Maximum light-dependent H14CO3 fixation in the chemocline in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea suggested that there was anaerobic autotrophic growth of the green sulfur bacteria. The metabolism of the epibionts was further studied by determining stable carbon isotope ratios (δ13C) of their specific biomarkers. Analysis of photosynthetic pigments by high-performance liquid chromatography revealed the presence of high concentrations of bacteriochlorophyll (BChl) e and smaller amounts of BChl a and d and chlorophyll a in the chemocline. Unexpectedly, isorenieratene and β-isorenieratene, carotenoids typical of other brown members of the green sulfur bacteria, were absent. Instead, four different esterifying alcohols of BChl e were isolated as biomarkers of green sulfur bacterial epibionts, and their δ13C values were determined. Farnesol, tetradecanol, hexadecanol, and hexadecenol all were significantly enriched in 13C compared to bulk dissolved and particulate organic carbon and compared to the biomarkers of purple sulfur bacteria. The difference between the δ13C values of farnesol, the major esterifying alcohol of BChl e, and CO2 was −7.1%, which provides clear evidence that the mode of growth of the green sulfur bacterial epibionts of “P. roseum” in situ is photoautotrophic.  相似文献   

18.
The author modified a respiratory gas analyzer to analyze the respiratory 13CO2 of 12 small laboratory animals all at once. To investigate the practical use of this system, mice were orally (OR) or intravenously (IV) given glucose solutions containing three different amounts of 13C-labeled glucose. Expired 13CO2 derived from exogenous glucose was detected within 10 minutes after administration in OR mice, but about 30 minutes in IV mice. The height of the peak of 13CO2 expiration was correlated with the administered 13C-glucose mass.  相似文献   

19.
The nature of the inorganic carbon utilized during photosynthesis by Chlorella pyrenoidosa was investigated using three experimental techniques (open gas analysis system with “artificial leaf” or “aqueous” chambers and O2 electrode system) to measure carbon assimilation. Photosynthesis was studied as a function of pH and CO2 concentration. The CO2 concentration was inadequate to meet the requirements of photosynthesis only when HCO3 was added at high pH. Under all other conditions, the low and constant Km (CO2), in contrast to the highly variable Km (HCO3), suggested that CO2 was the major species utilized.  相似文献   

20.
Propionate is an important intermediate of the degradation of organic matter in many anoxic environments. In methanogenic environments, due to thermodynamic constraints, the oxidation of propionate requires syntrophic cooperation of propionate-fermenting proton-reducing bacteria and H2-consuming methanogens. We have identified here microorganisms that were active in syntrophic propionate oxidation in anoxic paddy soil by rRNA-based stable-isotope probing (SIP). After 7 weeks of incubation with [13C]propionate (<10 mM) and the oxidation of ~30 μmol of 13C-labeled substrate per g dry weight of soil, we found that archaeal nucleic acids were 13C labeled to a larger extent than those of the bacterial partners. Nevertheless, both terminal restriction fragment length polymorphism and cloning analyses revealed Syntrophobacter spp., Smithella spp., and the novel Pelotomaculum spp. to predominate in “heavy” 13C-labeled bacterial rRNA, clearly showing that these were active in situ in syntrophic propionate oxidation. Among the Archaea, mostly Methanobacterium and Methanosarcina spp. and also members of the yet-uncultured “rice cluster I” lineage had incorporated substantial amounts of 13C label, suggesting that these methanogens were directly involved in syntrophic associations and/or thriving on the [13C]acetate released by the syntrophs. With this first application of SIP in an anoxic soil environment, we were able to clearly demonstrate that even guilds of microorganisms growing under thermodynamic constraints, as well as phylogenetically diverse syntrophic associations, can be identified by using SIP. This approach holds great promise for determining the structure and function relationships of further syntrophic or other nutritional associations in natural environments and for defining metabolic functions of yet-uncultivated microorganisms.  相似文献   

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