Gastric emptying in soldiers during and after field exercise in the heat measured with the [13C]acetate breath test method

The effects of exercise on gastric emptying remain controversial, with some workers reporting that heavy exercise inhibits it to varying degrees whereas others report no effects up to an intensity of 70% maximal oxygen consumption (O_2max). The state of hydration of the subjects and the environmental conditions may influence the rate of gastric emptying during exercise. To understand further the effects of a 3-h, 16-km walk/run carrying 30 kg of equipment under field conditions at 39°C, we estimated gastric emptying using a [¹³C]acetate breath test method. Breath samples were collected at intervals after giving 150 mg of [¹³C]acetate. The effects of giving a standard volume (530 ml) of water or dextrose (7.5 g · 100 ml⁻¹) with electrolytes or fructose/corn solids (7.5 g · 100 ml⁻¹) at rest before exercise were compared with those of exercise and of recovery after exercise with or without extra fluids (400 ml each 20 min). At rest, after a standard 530-ml load, gastric emptying times [mean (SE)] were: 37 (2) min (water), 46 (3) min (dextrose/electrolytes) and 47 (5) min (fructose/corn solids) and were significantly slower (P < 0.05) than those occurring after extra fluid ingestion, i.e. 32 (3), 39 (2) and 41 (3) min respectively. After a standard 530-ml load, emptying times during exercise were almost identical to those at rest but, during exercise, extra fluid speeded up gastric emptying more than at rest to 24 (2), 26 (1) and 27 (5) min (P < 0.05) respectively. During resting recovery without extra fluids, gastric emptying was significantly slowed to 60 (2), 71 (5) and 78 (3) min, respectively. Although emptying times during recovery from exercise with extra fluid were faster [49 (6), 55 (2) and 58 (4) min, respectively], they were still slower than before exercise. The results suggest that: (1) extra fluid increases gastric emptying more during exercise than at rest, and (2) gastric emptying during resting recovery from exercise is slower than at rest before exercise whether or not fluid has previously been taken. Accepted: 17 June 1996     

Faster gastric emptying for glucose-polymer and fructose solutions than for glucose in humans

This study examined the rates of gastric emptying for water and 13 different carbohydrate-containing solutions in seven subjects, using conventional gastric intubation techniques. The rates of gastric emptying for water and a 10% glucose-polymer solution were also measured during 90 min of treadmill running at 75% of each subject's maximum oxygen consumption (VO2max). At rest, 15% glucose-polymer (P) and fructose (F) solutions emptied more rapidly from the stomach and provided a faster rate of carbohydrate delivery than did a 15% glucose (G) solution (p less than 0.05). The G solutions showed a constant energy delivery rate of 3.3 kcal.min-1; energy delivery from P and F solutions rose with increasing solution concentrations. The osmolality of the gastric aspirate predicted the rate of gastric emptying for all solutions (p less than 0.05) but overestimated rates of emptying for 10% and 15% P solutions and underestimated emptying rates for 10% and 15% F solutions. Exercise at 75% VO2max decreased the rate of gastric emptying of water but not of 10% P solutions. Thus the different rates of gastric emptying for different carbohydrate-containing solutions were not entirely explained by differences in osmolality. Furthermore, exercise may have different effects on the gastric emptying rates of water and carbohydrate solutions.     

Biosynthesis of Pr toxin from [1,2-13C]acetate: occurrence of induced 13C13C coupling

The biosynthesis of PR toxin was studied by incorporation of [1,2-¹³C]acetate. The biosynthesis of the eremophilane skeleton of PR toxin follows th     

Exogenous 13C glucose oxidation during exercise: North American vs Western European studies

The purpose of this study was to test the hypothesis that the well-documented changes in background ¹³C enrichment of expired CO₂ observed in response to exercise and carbohydrate ingestion, in subjects living on a North American diet, are not present in subjects living on a Western European diet. The experimental protocol used by Pirnay et al. in 1977 and by Krzentowski et al. in 1984 in subjects living on a Western European diet (4 h of exercise on a treadmill at 50% VO_2max with ingestion of 100 g of glucose in 400 ml of water) was duplicated as closely as possible in six subjects living on a North American diet. The actual amounts of exogenous glucose oxidized, computed with a high artificial ¹³C enrichment of glucose (+189.7 ¹³C PDB-1) which allows one to neglect the 1–2 changes in ¹³C background, were [mean (SEM)] 54.7 (5.4) and 84.2 (3.4) g over 2 h and 4 h of exercise, respectively. These values compare well with data computed by Pirnay et al. [56.6 (13.1) and 94.9 (4.2) g] and by Krzentowski et al. [55.0 (6.2) and 88.0 (4.5) g] using a natural enrichment of glucose (–11.21 and –10.63 ¹³C PDB-1, respectively) assuming no change in ¹³C background in their Western European subjects. Under the same assumption and using a natural enrichment of glucose (–11.30 ¹³C PDB-1) the oxidation of exogenous glucose was overestimated by 30–40% in our North American subjects. This result indicates that because of a lower input of ¹³C in their diet, the difference between the isotopic composition of carbohydrate and fat stores are smaller, and changes in ¹³C background are small or absent in response to moderate workload in Western European subjects, when compared to their North American counterparts.     

13C-methacetin breath test parameter S for liver diseases diagnosis

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.     

13C NMR analysis of aporphine alkaloids

The ¹³C NMR spectra of some tertiary and quaternary aporphine alkaloids are recorded and the signals assigned. The substituent shielding effects together with the effects of N- and O-methylation, and the twisting of the biphenyl system, are analysed and utilized in the spectral interpretation.     

用天然13C丰度法评估贵州茂兰喀斯特森林区玉米地土壤中有机碳的来源

当森林生态系统转变成农田生态系统时,会把C4植物有机质导入到曾在C3植被下发育的土训中去,使土壤中含有来源不同的土壤有机质,引起碳同位素组成变化。因此,可以利用碳同位素来区分土壤有机质来源,实验结果表明,耕作几十年后原森林土壤有机质的含量仍占有主要地位,来源于原始C3植被的有机碳的比例为66.7％,但容易矿化的、对植物营养有效的有机质含量较低,这与当地的耕作方式有关,需要加强对植物残留物返回土壤工作的管理。     

Effect of centrally administered apelin-13 on gastric emptying and gastrointestinal transit in mice

Apelin, as the endogenous ligand for the APJ, regulates many biological functions, including blood pressure, neuroendocrine, drinking behavior, food intake and colonic motility. The present study was designed to investigate the effect of central apelin-13 on gastric emptying and gastrointestinal transit in mice. Intracerebroventricular (i.c.v.) injection of apelin-13 (3 and 10 μg/mouse) decreased gastric emptying rate by 10.9% and 17.1%. This effect was significantly antagonized by the APJ receptor antagonist apelin-13(F13A) and the opioid receptor antagonist naloxone, respectively. However, intraperitoneal (i.p.) injection of apelin-13 (10-100 μg/mouse) did not affect gastric emptying. Apelin-13 (0.3, 1 and 3 μg/mouse, i.c.v.) inhibited gastrointestinal transit by 16.8%, 23.4% and 19.2%. Apelin-13(F13A) and naloxone could also reverse this antitransit effect induced by apelin-13. Taken together, these results suggest that i.c.v. injected apelin-13 inhibits gastric emptying and gastrointestinal transit and it seems that APJ receptor and opioid receptor might be involved in these processes.     

亚热带人工林松树13C/12C比率和水分利用效率

The ¹³C/¹²Cratio, photosynthetic rate and stomatie conductivity of leaves of Pinus massoniana, Schima superba,Psychotria rubra, Evodia lepta and Rhodomyrtus tomentasa are measured. No significant deviation (at 5% level) is observed between water use efficiencies calculated by these items. The¹³C/¹²Cis 25.41±0.61‰. In average for treerings of Pinus massoniana from 1971 to 1983(n=6), with the maximum in1977 when the lowest precipitation was recorded. The average water use efficiency of Pinus massoniana is 8.28±0.38 in1977—1983, which is higher than that of trees in natural site and might be caused by the changes of solar radiation and water condition. ¹³C/¹²Cratio ana lysis could provide usefull informations for studying water use efficiency of artificial forest.     

13C NMR spectroscopy of Pyrrolizidine alkaloids

The ¹³C NMR spectra of nine pyrrolizidine alkaloids of the macrocyclic diester type, seven of the corresponding N-oxides and of the parent base retronecine have been recorded and the signals assigned. The 13C NMR signals were found to be sensitive to structural variation in both the diester moiety and the heterocyclic ring system, providing useful information for structural elucidation, particularly when the ¹H NMR spectra may be difficult to interpret.     

Chemical characterization of pigment gallstones using 13C nuclear magnetic resonance analysis

The unique ability of Carbon-13 nuclear magnetic resonance analysis with cross polarization/magic angle spinning techniques to investigate chemical structures of solids is used to probe the chemical characteristics of several gallstone types. New pulse program techniques are used to distinguish various carbon atoms in studying the polymeric nature of the black bilirubinoid pigment of pigment gallstones. Evidence for the involvement of the carboxyl group and noninvolvement of vinyl groups of bilirubinoids in the polymeric bond formation is presented. Conjugated bilirubin structures are found to be present in some solid residues from pigment stones extracted with acidic methanol/chloroform.     

13C NMR spectra of olean-18-ene derivatives

The ¹³C NMR signals of sixteen derivatives of olean-18-ene-triterpenes have been assigned.     

13C NMR spectral analysis of some isoquinoline alkaloids

The ¹³C NMR spectra of some isoquinoline and tetrahydroisoquinoline alkaloids and their corresponding N-methosalts and of the bisbenzylisoquinoline alkaloid isochondodendrine were recorded and the signals assigned. The substituent shielding effects and the ¹³C¹H long range couplings were analysed and utilized in the spectral interpretation.     

13C NMR spectral analysis of grindelane diterpenoid acids

The ¹³C NMR spectra of methyl grindelate and some of its derivatives were recorded and the signals assigned. Based on these assignments and on a comparison with previously reported data, information regarding the structures and stereochemistry of the products under study was obtained.     

亚热带季风常绿阔叶林树木年轮的13C/12C和空气CO2浓度变化

测定了亚热带季风常绿阔叶林的几种树木年轮的¹³C/¹²C比率(δ¹³C)。云南银柴的1962-1983年年轮δ¹³C平均为-28.53±0.84（n=5）,华润楠的1951-1984年年轮的δ¹³C为-28.46±0.53（n=6）。黄果厚壳桂的1951-1984年年轮的δ¹³C为-29.19±0.80（n=6）,木荷的1975-1984年年轮δ¹³C为-28.42±0.41（n=4）,δ¹³C数值偏离平均值逐年增大。计算空气CO₂浓度每年递增1.21μ1/L。     

三峡库区小江库湾鱼类食物网的稳定C、N同位素分析

应用稳定碳(δ₁₃C)、氮(δ₁₅N)同位素探讨了三峡库区一级支流小江库湾枯水期(2010.7)和丰水期间(2010.12)鱼类食物网结构。研究结果显示：初级生产者颗粒有机物(POM)和固着藻类δ₁₃C、δ₁₅N值范围分别为-23.33‰～-21.05‰、-25.13‰～-24.54‰,3.99‰～6.25‰、4.64‰～4.79‰。POM和固着藻类构成了小江库湾食物网能量的主要来源,其中丰水期间陆生营养物质输入是其食物网能量来源的一种重要补充途径。小江库湾常见鱼类食性可分为杂食偏植物食性、杂食偏动物食性及动物食性3种营养类群。在不同时期(枯水期和丰水期)小江库湾鱼类食物网营养级长度均有三级并且存在4种主要营养路径,表明了在三峡工程运行初期小江库湾已经形成了相对稳定的食物网结构。研究为小江库湾鱼类资源管理及生态系统恢复提供了一定的指导意义。     

13C NMR analysis of alkaloids from peschiera fuchsiaefolia

Fractionation of an ethereal extract of Peschiera fuchsiaefolia resulted in the isolation of decarbomethoxyvoacamine, demethylvoacamine, voacamidine, perivine, 16-epiaffinine and voacanginehydroxyindolenine, together with the previously reported alkaloids voacamine, voacangine, voachalotine and affinisine. Analysis of the ¹³C NMR spectra of the bisindole alkaloids and of 16-epiaffinine is reported.     

Deuterium and carbon-13 tracer studies of ethanol metabolism in the rat by 2H, 1H-decoupled 13C nuclear magnetic resonance

[1-¹³C, 1,1-²H₂] ethanol and [2,2,2-²H₃] ethanol were administered to bile fistula rats. A new technique, ²H, ¹H-decoupled ¹³C nuclear magnetic resonance, was used in attempting to account for the distribution of the isotopic species along the steroid skeleton of 3–45 mg of isolated bile acids. The technique revealed ²H incorporation at many carbon sites unambiguously, but has limitations as a quantitative ²H assay at these levels of sample availability.     

13C NMR spectral analysis of lignans from Araucaria angustifolia

Pinoresinol dimethyl ether, secoisolariciresinol, lariciresinol, isolariciresinol and isolariciresinol-4′-methyl ether were isolated from the knots of dead trees of Araucaria angustifolia. The ¹³C NMR spectra of these compounds, their methyl and acetyl derivatives, and the corresponding one of matairesinol, have been recorded and the signals assigned. On the basis of these assignments, the structure of the new monomethyl ether of isolariciresinol has been established.