Factors that influence the volatile organic compound content in human breath

BACKGROUND

Thousands of endogenous and exogenous volatile organic compounds (VOCs) are excreted in each breath. Inflammatory and deviant metabolic processes affect the level of endogeneous VOCs, which can serve as specific biomarkers for clinical diagnosis and disease monitoring. Important issues that still need to be tackled are related to potential confounding factors like gender and age and endogenous and exogenous factors, like f.i. smoking.

METHODS

The aim of this study was to systematically access the effect of endogenous and exogenous factors on VOC composition of exhaled breath. In the current study breath samples from 1417 adult participants from the LifeLines cohort, a general population cohort in the Netherlands, were collected and the total content of VOCs was measured using gas chromatography-time-of-flight-mass spectrometry. Breath samples were collected in Groningen and transferred to carbon tubes immediately. These samples were then shipped to Maastricht and measured in batches. VOCs profiles were correlated to 14 relevant characteristics of all participants including age, BMI, smoking and blood cell counts and metabolic parameters as well as to 16 classes of medications.

RESULTS

VOCs profiles were shown to be significantly influenced by smoking behavior and to a lesser extent by age, BMI and gender. These factors need to be controlled for in breath analysis studies. We found no evidence whatsoever in this 1417 subjects' cohort that white blood cell counts, cholesterol or triglycerides levels have an influence on the VOC profile. Thus they may not have to be controlled for in exhaled breath studies.

CONCLUSION

The large cohort of volunteers used here represents a unique opportunity to gauge the factors influencing VOCs profiles in a general population i.e. the most clinically relevant population. Classical clinical parameters and smoking habits clearly influence breath content and should therefore be accounted for in future clinical studies involving breath analysis.

Regularized MANOVA (rMANOVA) in untargeted metabolomics

Many advanced metabolomics experiments currently lead to data where a large number of response variables were measured while one or several factors were changed. Often the number of response variables vastly exceeds the sample size and well-established techniques such as multivariate analysis of variance (MANOVA) cannot be used to analyze the data. ANOVA simultaneous component analysis (ASCA) is an alternative to MANOVA for analysis of metabolomics data from an experimental design. In this paper, we show that ASCA assumes that none of the metabolites are correlated and that they all have the same variance. Because of these assumptions, ASCA may relate the wrong variables to a factor. This reduces the power of the method and hampers interpretation. We propose an improved model that is essentially a weighted average of the ASCA and MANOVA models. The optimal weight is determined in a data-driven fashion. Compared to ASCA, this method assumes that variables can correlate, leading to a more realistic view of the data. Compared to MANOVA, the model is also applicable when the number of samples is (much) smaller than the number of variables. These advantages are demonstrated by means of simulated and real data examples. The source code of the method is available from the first author upon request, and at the following github repository: https://github.com/JasperE/regularized-MANOVA.

Multivariate curve resolution: a review of advanced and tailored applications and challenges

Multivariate curve resolution (MCR) is a widespread methodology for the analysis of process data in many different application fields. This article intends to propose a critical review of the recently published works. Particular attention will be paid to situations requiring advanced and tailored applications of multivariate curve resolution, dealing with improvements in preprocessing methods, multi-set data arrangements, tailored constraints, issues related to non-ideal noise structure and deviation to linearity. These analytical issues are tackling the limits of applicability of MCR methods and, therefore, they can be considered as the most challenging ones.

Screening for emphysema via exhaled volatile organic compounds

Chronic obstructive pulmonary disease (COPD)/emphysema risk groups are well defined and screening allows for early identification of disease. The capability of exhaled volatile organic compounds (VOCs) to detect emphysema, as found by computed tomography (CT) in current and former heavy smokers participating in a lung cancer screening trial, was investigated. CT scans, pulmonary function tests and breath sample collections were obtained from 204 subjects. Breath samples were analyzed with a proton-transfer reaction mass spectrometer (PTR-MS) to obtain VOC profiles listed as ions at various mass-to-charge ratios (m/z). Using bootstrapped stepwise forward logistic regression, we identified specific breath profiles as a potential tool for the diagnosis of emphysema, of airflow limitation or gas-exchange impairment. A marker for emphysema was found at m/z 87 (tentatively attributed to 2-methylbutanal). The area under the receiver operating characteristic curve (ROC) of this marker to diagnose emphysema was 0.588 (95% CI 0.453-0.662). Mass-to-charge ratios m/z 52 (most likely chloramine) and m/z 135 (alkyl benzene) were linked to obstructive disease and m/z 122 (most probably alkyl homologs) to an impaired diffusion capacity. ROC areas were 0.646 (95% CI 0.562-0.730) and 0.671 (95% CI 0.524-0.710), respectively. In the screening setting, exhaled VOCs measured by PTR-MS constitute weak markers for emphysema, pulmonary obstruction and impaired diffusion capacity.

Discrimination between metastasis and glioblastoma multiforme based on morphometric analysis of MR images

BACKGROUND AND PURPOSE

Solitary MET and GBM are difficult to distinguish by using MR imaging. Differentiation is useful before any metastatic work-up or biopsy. Our hypothesis was that MET and GBM tumors differ in morphology. Shape analysis was proposed as an indicator for discriminating these 2 types of brain pathologies. The purpose of this study was to evaluate the accuracy of this approach in the discrimination of GBMs and brain METs.

MATERIALS AND METHODS

The dataset consisted of 33 brain MR imaging sets of untreated patients, of which 18 patients were diagnosed as having a GBM and 15 patients, as having solitary metastatic brain tumor. The MR imaging was segmented by using the K-means algorithm. The resulting set of classes (also called "clusters") represented the variety of tissues observed. A morphology-based approach allowed discrimination of the 2 types of tumors. This approach was validated by a leave-1-patient-out procedure.

RESULTS

A method was developed for the discrimination of GBMs and solitary METs. Two masses out of 33 were wrongly classified; the overall results were accurate in 93.9% of the observed cases.

CONCLUSIONS

A semiautomated method based on a morphologic analysis was developed. Its application was found to be useful in the discrimination of GBM from solitary MET.

Multivariate curve resolution of rapid-scan FTIR difference spectra of quinone photoreduction in bacterial photosynthetic membranes

Photosynthetic reaction centres and membranes are systems of particular interest and are often taken as models to investigate the molecular mechanisms of selected bioenergetic reactions. In this work, a multivariate curve resolution by alternating least squares procedure is detailed for resolution of time-resolved difference FTIR spectra probing the evolution of quinone reduction in photosynthetic membranes from Rhodobacter sphaeroides under photoexcitation. For this purpose, different data sets were acquired in the same time range and spectroscopic domain under slightly different experimental conditions. To enable resolution and provide meaningful results the different data sets were arranged in an augmented matrix. This strategy enabled recovery of three different species despite rank-deficiency conditions. It also results in better definition (identity and evolution) of the contributions. From the resolved spectra, the species have been attributed to: 1. the formation of ubiquinol, more precisely the disappearance of Q/appearance of QH(2); 2. conformational change of the protein in the surrounding biological medium; 3. oxidation of diaminodurene, a redox mediator. Because, moreover, results obtained from augmented data sets strategies enable quantitative and qualitative interpretation of concentration profiles, other effects, for example the consequence of repeated light excitation of the same sample, choice of illumination power, or the number of spectra accumulated could be compared and discussed.

[Loneliness among young people: collation of writings]

Contrary to the popular belief that loneliness is typically associated with adults, and especially with older persons, this state can occur early in life. In fact, an increasing number of studies indicate that an important proportion of adolescents experience an intense episode of loneliness. This literature review describes loneliness among younger persons. We discuss the ampleness of the problem, the definition of the phenomenon, the feeling associated with loneliness, precipitating and predisposating factors and, finally, coping strategies to deal with this experience.

Effect of two models of portal hypertension on splanchnic organ blood flow in the rat

Splanchnic organ blood flow and cardiac output were measured by the microsphere method in fasted rats with prehepatic portal hypertension due to portal vein stenosis, in rats with intrahepatic portal hypertension due to bile duct ligation, and in unoperated normal rats. Portal venous pressure was higher in both groups of portal hypertensive rats than in normal rats. Cardiac output was significantly higher in portal hypertensive rats than in normal rats. In rats with portal vein stenosis, splanchnic blood flow was higher than in controls. This increase was caused by increased perfusion of all organs drained by the portal vein, and by increased hepatic arterial blood flow. In rats with bile duct ligation, splanchnic blood flow was not significantly higher than in normal rats: haemoperfusion of all organs contributing to the portal circulation decreased, whereas hepatic arterial blood flow increased. As cardiac output rose similarly, the differences observed between the two types of portal hypertension depend mainly on the difference in distribution of flow within the splanchnic bed.

Changes in splanchnic blood flow in portal hypertensive rats

This study was undertaken to assess splanchnic blood flow in rats with portal hypertension induced by portal vein stenosis. Splanchnic blood flow, estimated by the microsphere method, was significantly higher in portal hypertensive rats than in sham-operated rats: 26.5 +/- 3.9 (mean +/- SD) and 17.5 +/- 3.3 ml/min, respectively (P less than 0.001). Hepatic blood flow, estimated by the clearance method, was significantly lower in portal hypertensive rats than in sham-operated rats: 12.7 +/- 1.1 and 17.3 +/- 2.8 ml/min, respectively (P less than 0.001). It is concluded that splanchnic blood flow is increased in rats with portal hypertension and that hepatic blood flow is different from splanchnic blood flow in these portal hypertensive rats. It is hypothesized that splanchnic blood flow may also be increased in patients with portal hypertension.

Effect of propranolol on hepatic blood flow in normal and portal hypertensive rats

1. The effects of propranolol on heart rate, arterial pressure, portal venous pressure and fractional hepatic blood flow were studied in rats with hepatic artery ligature or with portal vein stenosis, and in sham-operated rats. The effect of propranolol on cardiac output was also studied in normal rats. 2. In rats with hepatic artery ligature or with portal vein stenosis, and in sham-operated rats, propranolol decreased heart rate and portal venous pressure significantly and did not alter arterial pressure. Propranolol decreased fractional hepatic blood flow significantly in rats with hepatic artery ligature, but did not change hepatic blood flow in rats with portal vein stenosis or in sham-operated rats. 3. We conclude therefore that: (a) propranolol decreases portal venous pressure in rats; (b) this decrease in portal venous pressure results in a reduction in portal blood flow which is related, in part, to a reduction in cardiac output; (c) propranolol does not alter hepatic blood flow in normal rats or in rats with portal hypertension.

Measurement of hepatic blood flow in the rat using fractional clearance of indocyanine green and colloidal radiogold

Two new methods are described to measure hepatic blood flow in the anaesthetized rat. These methods are based on the fractional clearance and extraction of indocyanine green, which is removed by hepatocytes, and of colloidal radiogold, which is removed by Kupffer cells. Hepatic blood flow was found to be 2.11 +/- 0.35 ml . min-1 . g liver-1 (mean +/- SD) and 2.01 +/- 0.31 ml . min-1 . g liver-1, respectively, with these two substances (P greater than 0.80).

[Networking, an alternative model of community empowerment.]

After a brief critical analysis of some of the limitations of community psychiatry, the authors give an historical review of the social psychiatric network and its characteristics. They then describe their manner of applying the network concept, an approach whose originality consists in asking the patient to reunite his primary network (family, friends, neighbours, etc.) in order to identify the problems and to determine how (the network) can help. They develop a different approach from that of community psychiatry, by emphasizing the role of primary networks as emotional support structures and as a non-psychiatric solution. However, the network intervention is not presented as a cure-all and the authors conclude by describing the limitations of their approach.

[Mental health : costs and social factors.]

The author gives a brief history of psychiatry in Quebec and attempts to show that economic factors influence social evolution. After having shown that the costs of mental health reach $ 500 millions, he makes an appeal for the rationalization of services in this time of economic austerity.

[Mental health in Pointe-St-Charles : towards collective responsibility.]

The Pointe St-Charles Community Clinic is a popular, user-run clinic, where psychiatric treatment is integrated into the services of the medical-social teams, and where, more globally, an attitude of a collective responsability for mental health is beginning to develop as a result of the active involvement, on the part of both clinic workers and users, in the social change process and the optimal use of the natural community ressource network.