Concentration of light hydrocarbons in exhaled air depending on metabolic syndrome risk factors

The effect of metabolic syndrome risk factors on the content of light hydrocarbons (C₂-C₃) in exhaled air has been studied with the participation of students of Novosibirsk State Medical University. Gas chromatography was performed in an EKHO-EW-FID chromatograph with a short multichannel column. The study revealed sex-related differences between the concentrations of light hydrocarbons in exhaled air. In addition, some factors, such as smoking and type 2 diabetes mellitus in relatives, affect the content of C₂-C₃ compounds in exhaled air of women only. However, overweight is correlated with the content of acetone (C₃) in exhaled air only in men. Thus, the metabolic changes caused by the presence of age-specific metabolic syndrome risk factors lead to the changes in the gas composition of exhaled air and can be detected and used for early diagnosis.     

Identification of Fatty Acids and Aliphatic Hydrocarbons in Sarcina lutea by Gas Chromatography and Combined Gas Chromatography-Mass Spectrometry

The composition and nature of the fatty acids and hydrocarbons of Sarcina lutea were elucidated by gas chromatography and by combined gas chromatography-mass spectrometry. The distribution of fatty acids found in S. lutea showed two families of pairs, or dyads, of saturated monocarboxylic acids (C12-C18) with and without methyl branching. These pairs of fatty acids showed a pattern of iso and anteiso structures for C13, C15, and C17, and iso and normal structures for C12, C14, and C16. Only the C18 showed unsaturation. The distribution of hydrocarbons in the range C22-C29 showed two families of tetrads of unsaturated aliphatic hydrocarbons all showing methyl branching. Each tetrad was composed of four isomers identified as two iso olefins and two anteiso olefins. The only difference between the tetrads pertaining to different families was found in the relative gas chromatographic retention times of the last two components of each group.     

In vivo lipid peroxidation in man as measured by the respiratory excretion of ethane, pentane, and other low-molecular-weight hydrocarbons

A method for the collection and measurement of low-molecular-weight volatile hydrocarbons exhaled in human breath as a result of lipid peroxidation in vivo is described. Subjects breathed in a closed-circuit rebreathe system and samples were taken over a 2-h period, extracted, and analyzed by gas-liquid chromatography isothermally on a 3-m column of n-octane/Porasil-C. Immediately, prior to rebreathing subjects were equilibrated with scrubbed air containing very low ambient levels of hydrocarbons to eliminate the effects of previous exposure to hydrocarbon-contaminated environments. Only under these conditions could hydrocarbon exhalation be measured. In the rebreathe system C3-C5 hydrocarbon concentrations increased linearly initially but reached a steady state after 1.5 h while ethane did not approach equilibrium even after 2 h. The steady-state equilibrium was demonstrated to be due to tissue uptake and metabolism of the hydrocarbon gases. Ethane metabolism was slow, allowing calculation of the endogenous production from the initial rate of change in concentration and an experimentally determined total body solubility coefficient. Similar calculations for pentane were not valid as metabolism was rapid; therefore production was estimated from the equilibrium value reached after 2 h. Ethane production in six healthy subjects was calculated to be 95.1 +/- 19.0 pmol/kg/h while equilibrium values for pentane were 120 +/- 50 pmol/liter. This method now allows the quantitation in man of lipid peroxidation in vivo.     

Development of a physiologically based toxicokinetic model for butadiene and four major metabolites in humans: global sensitivity analysis for experimental design issues

1,3-Butadiene (BD) is metabolized in humans and rodents to mutagenic and carcinogenic species. Our previous work has focused on developing a physiologically based toxicokinetic (PBTK) model for BD to estimate its metabolic rate to 1,2-epoxy-3-butene (EB), using exhaled breath BD concentrations in human volunteers exposed by inhalation. In this paper, we extend our BD model to describe the kinetics of its four major metabolites EB, 1,2:3,4-diepoxybutane (DEB), 3-butene-1,2-diol (BDD), and 3,4-epoxy-1,2-butanediol (EBD), and to test whether the extended model and experimental data (to be collected for BD and metabolites in humans) are together adequate to estimate the metabolic rate constants of each of the above chemicals. Global sensitivity analyses (GSA) were conducted to evaluate the relative importance of the model parameters on model outputs during the 20min of exposure and the 40min after exposure ended. All model parameters were studied together with various potentially measurable model outputs: concentrations of BD and EB in exhaled air, concentrations of BD and all metabolites in venous blood, and cumulated amounts of urinary metabolites excreted within 24h. Our results show that pulmonary absorption of BD and subsequent distribution and metabolism in the well-perfused tissues compartment are the critical processes in the toxicokinetics of BD and metabolites. In particular, three parameters influence numerous outputs: the blood:air partition coefficient for BD, the metabolic rate of BD to EB, and the volume of the well-perfused tissues. Other influential parameters include other metabolic rates, some partition coefficients, and parameters driving the gas exchanges (in particular, for BD outputs). GSA shows that the impact of the metabolic rate of BD to EB on the BD concentrations in exhaled air is greatly increased if a few of the model's important parameters (such as the blood:air partition coefficient for BD) are measured experimentally. GSA also shows that all the transformation pathways described in the PBTK model may not be estimable if only data on the studied outputs are collected, and that data on a specific output for a chemical may not inform all the transformations involving that chemical.     

Assessment of age-related glucose oxidation rates of broiler chickens by using stable isotopes

During their relatively short commercial lifespan of six weeks, broiler chickens undergo very pronounced age- or body weight-related changes in metabolic rate and body composition. The present study was aimed to assess the age-related changes in glucose oxidation rate of broiler chickens by using 13C-labeled glucose. The methodology for this breath test needed to be established first. Broiler chickens aged from two to six weeks were placed in open-circuit respiration cells and received a single intubation of U-13C6-glucose, followed by breath sampling for 4 hours and mass spectrometric analysis of 13C: 12C ratio in the exhaled air. Simultaneously, CO2 concentration in the respiration cell air was continuously monitored in order to calculate the cumulative percentage dose recovery (CPDR). With respect to the methodology, an oral dose of 2 mg U-13C6-glucose per kg body weight while maintaining a CO2 in the concentration of 0.4 to 0.5% was considered to be optimal. The three-parameter Gompertz curve fitted the CPDR values very well. Pronounced age-related changes in exogenous glucose oxidation rates in rapidly growing meat-type chickens were assessed. Young broiler chickens spend only a relatively low percentage of ingested glucose for immediate oxidation. In contrast, broiler chickens approaching the age of maximal absolute growth rate oxidize a greater proportion of the recently ingested glucose relative to the non-oxidative disposal pathways. This shift in the exogenous partitioning is discussed in relation to age-dependent changes in glucose turnover, lipid oxidation and deposition and metabolic heat production.     

Seasonal changes in mood and behavior are linked to metabolic syndrome

Background

Obesity is a major public health problem worldwide. Metabolic syndrome is a risk factor to the cardiovascular diseases. It has been reported that disruptions of the circadian clockwork are associated with and may predispose to metabolic syndrome.

Methodology and Principal Findings

8028 individuals attended a nationwide health examination survey in Finland. Data were collected with a face-to-face interview at home and during an individual health status examination. The waist circumference, height, weight and blood pressure were measured and samples were taken for laboratory tests. Participants were assessed using the ATP-III criteria for metabolic syndrome and with the Seasonal Pattern Assessment Questionnaire for their seasonal changes in mood and behavior. Seasonal changes in weight in particular were a risk factor of metabolic syndrome, after controlling for a number of known risk and potential confounding factors.

Conclusions and Significance

Metabolic syndrome is associated with high global scores on the seasonal changes in mood and behavior, and with those in weight in particular. Assessment of these changes may serve as a useful indicator of metabolic syndrome, because of easy assessment. Abnormalities in the circadian clockwork which links seasonal fluctuations to metabolic cycles may predispose to seasonal changes in weight and to metabolic syndrome.     

Saturated hydrocarbons in bovine liver

A homologous series of n-alkanes (C(14)-C(33)) and two isoprenoid hydrocarbons, 2,6,10,14-tetramethylhexadecane (phytane) and 2,6,10,14-tetramethylpentadecane (pristane) have been identified in bovine liver. Another branched but non-isoprenoid alkane and three isomers of molecular formula C(20)H(40) were partially identified. Phytane and the C(18)-C(22) and C(29)-C(33)n-alkanes were found to be the major components in liver, suggesting that at least the main hydrocarbon components were derived from various plants in the diet. The hydrocarbons were separated and identified by a series of steps involving solvent extraction, saponification, elution chromatography on alumina and silica gel columns, molecular sieving and by infrared and ultraviolet spectroscopy, followed by combined capillary gas chromatography-mass spectrometry.     

Sex differences in risk factors for cardiovascular disease: the PERU MIGRANT study

Introduction

Although men and women have similar risk factors for cardiovascular disease, many social behaviors in developing countries differ by sex. Rural-to-urban migrants have different cardiovascular risk profiles than rural or urban dwellers. The objective of this study was to evaluate the sex differences with specific cardiovascular risk factors in rural-to-urban migrants.

Methods and Results

We used the rural-to-urban migrant group of the PERU MIGRANT cross-sectional study to investigate the sex differences in specific cardiovascular risk factors: obesity, hypertension, metabolic syndrome, as well as exposures of socioeconomic status, acculturation surrogates and behavioral characteristics. Logistic regression analysis was used to characterize strength of association between sex and our outcomes adjusting for potential confounders. The sample of migrants was 589 (mean age 46.5 years) and 52.4% were female. In the adjusted models, women were more likely to be obese (OR=5.97; 95%CI: 3.21–11) and have metabolic syndrome (OR=2.22; 95%CI: 1.39–3.55) than men, explaining the greatest variability for obesity and metabolic syndrome but not for hypertension.

Conclusions

Our results suggest that interventions for CVD in Peru should be sex-specific and address the unique health needs of migrant populations living in urban shantytowns since the risk factors for obesity and metabolic syndrome differ between males and females.     

Female sex pheromone of Cystidia couaggaria couaggaria (Lepidoptera: Geometridae): identification and field attraction

The plum cankerworm moth, Cystidia couaggaria couaggaria (Geometridae: Ennominae), is a defoliator of Chinese plum trees (Prunus mume). The pheromone components of the female were analyzed by gas chromatography (GC) with an electro-antennographic (EAG) detector and GC coupled with mass spectrometry. The crude pheromone extract included several EAG-active components, i.e., trienyl, dienyl, and saturated hydrocarbons, with a C21-C25 straight chain. The characteristic mass spectra indicated the unsaturated hydrocarbons to be (3Z,6Z,9Z)-3,6,9-trienes and (6Z,9Z)-6,9-dienes. In the fields, mixtures of the synthetic C<21 and C<23 trienes in a ratio of 2:3 and 1:4 successfully attracted males of this diurnal species during daytime. While the male antennae responded to the C25 triene and saturated hydrocarbons, their synergistic effects were not observed on the male attraction in the fields. Addition of the C21 diene interestingly inhibited the activity of the triene mixture. Males of Cystidia truncangulata, a sympatric diurnal congener of C. c. couaggaria, showed similar EAG responses to the unsaturated hydrocarbons, but no C. truncangulata males were attracted by the lures tested for C. c. couaggaria males, indicating that the identified hydrocarbons comprised the species-specific pheromone of C. c. couaggaria females.     

Composition of the surface hydrocarbons from the vitelline membranes of dipteran embryos

Hydrocarbons were the major lipid class extracted by hexane from the vitelline membrane surface of dechorionated eggs of the house fly, Musca domestica, the New World screwworm, Cochliomyia hominivorax, the secondary screwworm, Cochliomyia macellaria, the green bottle fly, Phaenicia sericata, the sheep blow fly, Lucilia cuprina and the Mexican fruit fly, Anastrepha ludens. The length of time the embryos must be exposed to hexane with or without a small amount of alcohol in order to attain permeability was species-dependant. Long-chain n-alkanes comprised the major lipid class removed from vitelline membranes of all species except A. ludens where 2-methylalkanes were the major class. The range in size by the total number of carbon atoms in the hydrocarbons was: C23-C49 in C. hominivorax, C27-C33 in C. macellaria, C24-C35 in L. cuprina, C25-C36 in M. domestica, C25-C33 in P. sericata and C21-C51 in A. ludens. The major hydrocarbon component, expressed as percent of the total hydrocarbons, was n-nonacosane (C29) in C. hominivorax (40%), C. macellaria (43%), L. cuprina (38%), M. domestica (39%) and P. sericata (60%). However, in A. ludens, 2-methyloctacosane (32%) was the major hydrocarbon. Unsaturated hydrocarbons, monoenes (16%) and dienes (11%), were abundant only in A. ludens. Since prior studies indicated that the length of time the embryos must be exposed to hexane with or without a small amount of alcohol in order to attain permeability is species dependant, we suggest that the differences in hydrocarbon composition may contribute to this variation in lipid extractability.     

The relationship of body fat to metabolic disease: Influence of sex and ethnicity

Clinical investigations designed to determine risk profiles for the development of cardiovascular disease (CVD) and type 2 diabetes mellitus (DM) are usually performed in homogenous populations and often focus on body mass index (BMI), waist circumference (WC), and fasting triglyceride (TG) levels. However, there are major ethnic differences in the relationship of these risk factors to outcomes. For example, the BMI risk threshold may be higher in blacks than in whites and higher in women than in men. Furthermore, a WC that predicts an obese BMI in white women only predicts a BMI in the overweight category in black women. In addition, overweight black men have a greater risk of developing type 2 DM than do overweight black women. Although TG levels are excellent predictors of insulin resistance in whites, they are not effective markers of insulin resistance in blacks. Among the criteria sets currently available to predict the development of CVD and type 2 DM, the most well known is the metabolic syndrome. The metabolic syndrome has 5 criteria: central obesity, hypertriglyceridemia, low high-density lipoprotein (HDL) levels, fasting hyperglycemia, and hypertension. To make the diagnosis of the metabolic syndrome, 3 of the 5 factors must be present. For central obesity and low HDL, the metabolic syndrome guidelines are sex specific. Diagnostic guidelines should also take ethnic differences into account, particularly in the diagnosis of central obesity and hypertriglyceridemia.     

Phosphatidylserine binding alters the conformation and specifically enhances the cofactor activity of bovine factor Va

Factor V(a) is a cofactor for the serine protease factor X(a) that activates prothrombin to thrombin in the presence of Ca(2+) and a platelet membrane surface. A platelet membrane lipid, phosphatidylserine (PS), regulates the proteolytic activity of factor X(a) as well as the structure of prothrombin. Here we ask whether PS also regulates the structure and cofactor activity of factor V(a), which is a heterodimer composed of one heavy chain (A1-A2 domains) and one light chain (A3-C1-C2 domains). We use fluorescence, circular dichroism, equilibrium dialysis, and activity measurements to demonstrate the following: (1) Factor V(a) has four sites for dicaproyl-sn-glycero-3-phospho-L-serine (C(6)PS, a soluble form of PS); the heavy and light chains each bind two C(6)PS molecules. (2) In the absence of Ca(2+), only two sites remain, one in the heavy chain and another in the light chain. (3) Binding to these sites causes conformational changes evidenced by changes in intrinsic fluorescence and in CD spectra and changes in cofactor activity. (4) At least some of the four lipid binding sites are nonspecific with respect to soluble lipid species, but the site(s) that regulate(s) cofactor activity is (are) specific for C(6)PS, phosphatidic acid, or phosphatidyl(homo)serine and produce a response comparable to that seen with a PS-containing membrane. (5) Like Ca(2+), C(6)PS also mediates the interaction between factor V(a) heavy (V(a)-HC) and light (V(a)-LC) chains. We conclude that PS regulates both the cofactor and the enzyme of the prothrombin-activating complex.     

Discrimination of Health Risk by Combined Body Mass Index and Waist Circumference

Objective: NIH Clinical Guidelines (1998) recommend the measurement of waist circumference (WC, centimeters) within body mass index (BMI, kilograms per square meter) categories as a screening tool for increased health risk. Research Methods and Procedures: The Canada Heart Health Surveys (1986 through 1992) were used to describe the prevalence of the metabolic syndrome in Canada and to test the use of the NIH guidelines for predicting metabolic risk factors. The sample included 7981 participants ages 20 to 74 years who had complete data for WC, BMI, high‐density lipoprotein‐cholesterol, triglycerides, diabetic status, and systolic and diastolic blood pressures. National Cholesterol Education Program Adult Treatment Panel III risk categories were used to identify the metabolic syndrome and associated risk factors. Logistic regression was used to test the hypothesis that WC improves the prediction of the metabolic syndrome, within overweight (25 to 29.9 kg/m²) and obese I (30 to 34.9 kg/m²) BMI categories. Results: The prevalence of the metabolic syndrome was 17.0% in men and 13.2% in women. The odds ratios (OR) for the prediction of the metabolic syndrome were elevated in overweight [OR, 1.85; 95% confidence interval (95%CI), 1.02 to 3.35] and obese (OR, 2.35; 95%CI, 1.25 to 4.42) women with a high WC compared with overweight and obese women with a low WC, respectively. On the other hand, WC was not predictive of the metabolic syndrome or component risk factors in men, within BMI categories. Discussion: In women already at increased health risk because of an elevated BMI, the additional measurement of WC may help identify cardiovascular risk.     

Serum calcium levels are associated with novel cardiometabolic risk factors in the population-based CoLaus study

Background

Associations of serum calcium levels with the metabolic syndrome and other novel cardio-metabolic risk factors not classically included in the metabolic syndrome, such as those involved in oxidative stress, are largely unexplored. We analyzed the association of albumin-corrected serum calcium levels with conventional and non-conventional cardio-metabolic risk factors in a general adult population.

Methodology/Principal Findings

The CoLaus study is a population-based study including Caucasians from Lausanne, Switzerland. The metabolic syndrome was defined using the Adult Treatment Panel III criteria. Non-conventional cardio-metabolic risk factors considered included: fat mass, leptin, LDL particle size, apolipoprotein B, fasting insulin, adiponectin, ultrasensitive CRP, serum uric acid, homocysteine, and gamma-glutamyltransferase. We used adjusted standardized multivariable regression to compare the association of each cardio-metabolic risk factor with albumin-corrected serum calcium. We assessed associations of albumin-corrected serum calcium with the cumulative number of non-conventional cardio-metabolic risk factors.We analyzed 4,231 subjects aged 35 to 75 years. Corrected serum calcium increased with both the number of the metabolic syndrome components and the number of non-conventional cardio-metabolic risk factors, independently of the metabolic syndrome and BMI. Among conventional and non-conventional cardio-metabolic risk factors, the strongest positive associations were found for factors related to oxidative stress (uric acid, homocysteine and gamma-glutamyltransferase). Adiponectin had the strongest negative association with corrected serum calcium.

Conclusions/Significance

Serum calcium was associated with the metabolic syndrome and with non-conventional cardio-metabolic risk factors independently of the metabolic syndrome. Associations with uric acid, homocysteine and gamma-glutamyltransferase were the strongest. These novel findings suggest that serum calcium levels may be associated with cardiovascular risk via oxidative stress.     

Exhaled breath and fecal volatile organic biomarkers of chronic kidney disease

BackgroundWhile much is known about the effect of chronic kidney disease (CKD) on composition of body fluids little is known regarding its impact on the gases found in exhaled breath or produced by intestinal microbiome. We have recently shown significant changes in the composition of intestinal microbiome in humans and animals with CKD. This study tested the hypothesis that uremia-induced changes in cellular metabolism and intestinal microbiome may modify the volatile organic metabolites found in the exhaled breath or generated by intestinal flora.MethodsSD rats were randomized to CKD (5/6 nephrectomy) or control (sham operation) groups. Exhaled breath was collected by enclosing each animal in a glass chamber flushed with clean air, then sealed for 45 min and the trapped air collected. Feces were collected, dissolved in pure water, incubated at 37 °C in glass reactors for 24 h and the trapped air collected. Collected gases were analyzed by gas chromatography.ResultsOver 50 gases were detected in the exhaled breath and 36 in cultured feces. Four gases in exhaled breath and 4 generated by cultured feces were significantly different in the two groups. The exhaled breath in CKD rats showed an early rise in isoprene and a late fall in linear aldehydes. The CKD animals' cultured feces released larger amounts of dimethyldisulfide, dimethyltrisulfide, and two thioesters.ConclusionsCKD significantly changes the composition of exhaled breath and gaseous products of intestinal flora.General significanceAnalysis of breath and bowel gases may provide useful biomarkers for detection and progression of CKD and its complications.     

Toxicometabolomics: Identification of markers of chronic exposure to low doses of aliphatic hydrocarbons

The metabolic profile of plasma of white non-linear rats was investigated under normal conditions and after chronic inhalation exposure to low doses of aliphatic hydrocarbons (HC) with the number of carbon atoms from 6 to 10. The metabolic profile was determined by a combination of gas chromatography/mass spectrometry and high-performance liquid chromatography/high-resolution mass spectrometry with the subsequent use of chemometrical methods for data treatment and presentation. It was shown that continuous 90-day exposure to a mixture of C₆–C₁₀ saturated hydrocarbons at a concentration of 160 ± 20.5 mg/m³ leads to various metabolic impairments in the liver and kidneys. Exposure to hydrocarbon mixtures at doses of 31.4 ± 5.6 and 5.2 ± 1.8 mg/m³ evoked significantly smaller changes. Novel metabolic markers of the toxic effect of low concentrations of C6–C10 aliphatic hydrocarbons were revealed. The concentration ratio of pyrophosphoric and oxalic acids in rat blood plasma was found to be the most sensitive marker called a pyrophosphate index. A hypothesis was proposed about the disturbance of the redox balance as a leading pathogenetic mechanism of neuropathies and concomitant pathologies associated with chronic HC intoxication.     

Development of accurate classification method based on the analysis of volatile organic compounds from human exhaled air

Analysis of exhaled air leads to the development of fast accurate and non-invasive diagnostics. A comprehensive analysis of the entire range of volatile organic compounds (VOCs) in exhaled air samples will enable the identification of VOCs unique for certain patient groups. This study demonstrates proof of principle of our developed method tested on a smoking/non-smoking study population. Thermal desorption and gas chromatography coupled to time-of-flight mass spectrometry were used to analyse exhaled air samples. The VOC profiles obtained from each individual were combined into one final database based on similarity of mass spectra and retention indexes (RI), which offers the possibility for a reliable selection of compounds of interest. As proof of principle we correctly classified all subjects from population of smoking (N=11) and non-smoking (N=11) based on the VOC profiles available in their exhaled air. Support vector machine (SVM) analysis identified 4 VOCs as biomarkers of recent exposure to cigarette smoke: 2,5-dimethyl hexane, dodecane, 2,5-dimethylfuran and 2-methylfuran. This approach contributes to future development of fast, accurate and non-invasive diagnostics of inflammatory diseases including pulmonary diseases.     

Defining adult asthma endotypes by clinical features and patterns of volatile organic compounds in exhaled air

Background

Several classifications of adult asthma patients using cluster analyses based on clinical and demographic information has resulted in clinical phenotypic clusters that do not address molecular mechanisms. Volatile organic compounds (VOC) in exhaled air are released during inflammation in response to oxidative stress as a result of activated leukocytes. VOC profiles in exhaled air could distinguish between asthma patients and healthy subjects. In this study, we aimed to classify new asthma endotypes by combining inflammatory mechanisms investigated by VOC profiles in exhaled air and clinical information of asthma patients.

Methods

Breath samples were analyzed for VOC profiles by gas chromatography–mass spectrometry from asthma patients (n = 195) and healthy controls (n = 40). A total of 945 determined compounds were subjected to discriminant analysis to find those that could discriminate healthy from asthmatic subjects. 2-step cluster analysis based on clinical information and VOCs in exhaled air were used to form asthma endotypes.

Results

We identified 16 VOCs, which could distinguish between healthy and asthma subjects with a sensitivity of 100% and a specificity of 91.1%. Cluster analysis based on VOCs in exhaled air and the clinical parameters FEV1, FEV1 change after 3 weeks of hospitalization, allergic sensitization, Junipers symptoms score and asthma medications resulted in the formation of 7 different asthma endotype clusters. We identified asthma clusters with different VOC profiles but similar clinical characteristics and endotypes with similar VOC profiles, but distinct clinical characteristics.

Conclusion

This study demonstrates that both, clinical presentation of asthma and inflammatory mechanisms in the airways should be considered for classification of asthma subtypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0136-8) contains supplementary material, which is available to authorized users.     

呼出气温度的研究现状

呼出气温度是一种新的呼吸系统疾病监测手段。从被发现开始,呼出气温度就引起了众多学者的兴趣。人们发现在哮喘等呼吸系统疾病患者身上测出的呼出气温度较正常健康人的呼出气温度要高。大量的研究结果表明呼出气温度的变化与患者肺部的炎症改变有关,学者们研究推断肺部的炎症改变使得肺部病变部位局部血管增生及血流量增加因而导致了肺部气道热量交换和损失的改变,最终导致患者呼出气温度的改变。这一发现在呼吸系统疾病中有着重要意义,科学家们认为呼出气温度可以作为一种非侵入性的新监测手段。     

Panicum milioides (C(3)-C(4)) does not have improved water or nitrogen economies relative to C(3) and C(4) congeners exposed to industrial-age climate change

The physiological implications of C(3)-C(4) photosynthesis were investigated using closely related Panicum species exposed to industrial-age climate change. Panicum bisulcatum (C(3)), P. milioides (C(3)-C(4)), and P. coloratum (C(4)) were grown in a glasshouse at three CO(2) concentrations ([CO(2)]: 280, 400, and 650?μl l(-1)) and two air temperatures [ambient (27/19?°C day/night) and ambient + 4?°C] for 12 weeks. Under current ambient [CO(2)] and temperature, the C(3)-C(4) species had higher photosynthetic rates and lower stomatal limitation and electron cost of photosynthesis relative to the C(3) species. These photosynthetic advantages did not improve leaf- or plant-level water (WUE) or nitrogen (NUE) use efficiencies of the C(3)-C(4) relative to the C(3) Panicum species. In contrast, the C(4) species had higher photosynthetic rates and WUE but similar NUE to the C(3) species. Increasing [CO(2)] mainly stimulated photosynthesis of the C(3) and C(3)-C(4) species, while high temperature had no or negative effects on photosynthesis of the Panicum species. Under ambient temperature, increasing [CO(2)] enhanced the biomass of the C(3) species only. Under high temperature, increasing [CO(2)] enhanced the biomass of the C(3) and C(3)-C(4) species to the same extent, indicating increased CO(2) limitation in the C(3)-C(4) intermediate at high temperature. Growth [CO(2)] and temperature had complex interactive effects, but did not alter the ranking of key physiological parameters amongst the Panicum species. In conclusion, the ability of C(3)-C(4) intermediate species partially to recycle photorespired CO(2) did not improve WUE or NUE relative to congeneric C(3) or C(4) species grown under varying [CO(2)] and temperature conditions.