Claude C. Grigsby

Differential binding between volatile ligands and major urinary proteins due to genetic variation in mice

Two different structural classes of chemical signals in mouse urine, i.e., volatile organic compounds (VOCs) and the major urinary proteins (MUPs), interact closely because MUPs sequester VOCs. Although qualitative and/or quantitative differences in each chemical class have been reported, previous studies have examined only one of the classes at a time. No study has analyzed these two sets simultaneously, and consequently binding interactions between volatile ligands and proteins in urines of different strains have not been compared. Here, we compared the release of VOCs in male urines of three different inbred strains (C57BL/6J, BALB/b and AKR) before and after denaturation of urinary proteins, mainly MUPs. Both MUP and VOC profiles were distinctive in the intact urine of each strain. Upon denaturation, each of the VOC profiles changed due to the release of ligands previously bound to MUPs. The results indicate that large amounts of numerous ligands are bound to MUPs and that these ligands represent a variety of different structural classes of VOCs. Furthermore, the degree of release in each ligand was different in each strain, indicating that different ligands are differentially bound to proteins in the urines of different strains. Therefore, these data suggest that binding interactions in ligands and MUPs differ between strains, adding yet another layer of complexity to chemical communication in mice.

Age-Dependent Partition Coefficients for a Mixture of Volatile Organic Solvents in Sprague-Dawley Rats and Humans

The absorption, distribution, metabolism, and excretion of volatile organic compounds (VOCs) are critically determined by a few chemical-specific factors, notably their blood and tissue partition coefficients (PC) and metabolism. Age-specific values for PCs in rats have rarely been reported or utilized in pharmacokinetic modeling for predicting dosimetry in toxicity studies with rats progressing through their lifestages. A mixture of six VOCs (benzene, chloroform, methyl ethyl ketone, methylene chloride, trichloroethylene, and perchloroethylene) was used to determine blood:air and tissue:air PCs in rats at three different ages (postnatal d 10, 60 d, and 2 yr) and blood:air PCs in pediatric and adult human blood. No differences with age in human blood:air PCs for the six compounds were observed. Rat blood:air PCs increased with age varying with compound. Tissue:air PCs showed tissue-specific changes with age. Water-soluble methyl ethyl ketone showed no age-dependent differences. Partition coefficients, particularly the blood:air PC, are key determinants of the rodent and human blood concentrations; age-appropriate values improve the accuracy of pharmacokinetic model predictions of population variability and age-specific exposures.

Changes in volatile compounds of mouse urine as it ages: Their interactions with water and urinary proteins

Mice release a variety of chemical signals, particularly through urine, which mediate social interactions and endocrine function. Studies have been conducted to investigate the stability of urinary chemosignals in mice. Neuroendocrine and behavioral responses of mice to urine samples of male and female conspecifics which have aged for different amounts of time have been examined, demonstrating that the quality and intensity of signaling molecules in urine change over time. In this study, we monitored changes in volatile organic compounds (VOCs) released from male and female mouse urine following aging the urine samples. Substantial amounts of some VOCs were lost during the aging process of urine, whereas other VOCs increased. Considerable portions of the VOCs which exhibited the increased release were shown to have previously been dissolved in water and subsequently released as the urine dried. We also demonstrated that some VOCs decreased slightly due to their binding with the major urinary proteins (MUPs) and identified MUP ligands whose headspace concentrations increased as the urine aged. Our results underscore the important role of MUPs and the hydration status in the release of VOCs in urine, which may largely account for the changes in the quality and intensity of urinary signals over time.

Metabolite Differentiation and Discovery Lab (MeDDL): A New Tool for Biomarker Discovery and Mass Spectral Visualization

The goal of this work was to design and implement a prototype software tool for the visualization and analysis of small molecule metabolite GC-MS and LC-MS data for biomarker discovery. The key features of the Metabolite Differentiation and Discovery Lab (MeDDL) software platform include support for the manipulation of large data sets, tools to provide a multifaceted view of the individual experimental results, and a software architecture amenable to modification and addition of new algorithms and software components. The MeDDL tool, through its emphasis on visualization, provides unique opportunities by combining the following: easy use of both GC-MS and LC-MS data; use of both manufacturer specific data files as well as netCDF (network Common Data Form); preprocessing (peak registration and alignment in both time and mass); powerful visualization tools; and built in data analysis functionality.

Evaluation of Bio-VOC Sampler for Analysis of Volatile Organic Compounds in Exhaled Breath

Monitoring volatile organic compounds (VOCs) from exhaled breath has been used to determine exposures of humans to chemicals. Prior to analysis of VOCs, breath samples are often collected with canisters or bags and concentrated. The Bio-VOC breath sampler, a commercial sampling device, has been recently introduced to the market with growing use. The main advantage for this sampler is to collect the last portion of exhaled breath, which is more likely to represent the air deep in the lungs. However, information about the Bio-VOC sampler is somewhat limited. Therefore, we have thoroughly evaluated the sampler here. We determined the volume of the breath air collected in the sampler was approximately 88 mL. When sampling was repeated multiple times, with the succeeding exhalations applied to a single sorbent tube, we observed linear relationships between the normalized peak intensity and the number of repeated collections with the sampler in many of the breath VOCs detected. No moisture effect was observed on the Tenax sorbent tubes used. However, due to the limitation in the collection volume, the use of the Bio-VOC sampler is recommended only for detection of VOCs present at high concentrations unless repeated collections of breath samples on the sampler are conducted.

The identification of hypoxia biomarkers from exhaled breath under normobaric conditions

Pilots have reported experiencing in-flight hypoxic-like symptoms since the inception of high-altitude aviation. As a result, the need to monitor pilots, in-flight, for the onset of hypoxic conditions is of great interest to the aviation community. We propose that exhaled breath is an appropriate non-invasive medium for monitoring pilot hypoxic risk through volatile organic compound (VOC) analysis. To identify changes in the exhaled breath VOCs produced during periods of reduced O2 levels, volunteers were exposed to simulated flight profiles, i.e. sea level for 5 min, O2 levels found at elevated altitudes for 5 min or placebo and 5 min at 100% O2 recovery gas, using a modified flight mask interfaced with a reduced O2 breathing device. During the course of these test events, time series breath samples from the flight mask and pre/post bag samples were collected and analyzed by gas chromatography/mass spectrometry (GC/MS). Seven compounds (pentanal, 4-butyrolactone, 2-pentanone, 2-hexanone, 2-cyclopenten-1-one, 3-methylheptane and 2-heptanone) were found to significantly change in response to hypoxic conditions. Additionally, the isoprene, 2-methyl-1,3-butadiene, was found to increase following the overall exposure profile. This study establishes an experimental means for monitoring changes in VOCs in response to hypoxic conditions, a computational workflow for compound analysis via the Metabolite Differentiation and Discovery Lab and MatLab(©) software and identifies potential volatile organic compound biomarkers of hypoxia exposure.

Changes in volatile compounds of human urine as it ages: Their interaction with water

The urinary odors are commonly perceived as unpleasant. While numerous studies have identified the volatile organic compounds (VOCs) released from urine, the odorants responsible for the urine odor are not well characterized. Furthermore, anecdotal reports suggest that the odor of aged urine is different from that of fresh urine. However, no study has yet to investigate the specific VOCs released from aged urine. In this study, we analyzed and compared the VOCs released from fresh and aged urine samples, investigating the changes in the urinary VOCs as urine aged. We found an overall decrease in concentration of many urinary VOCs, and concluded this was due to the urine evaporating as it aged. On the contrary, some highly water-soluble compounds such as short and branched-chain organic acids and trimethylamine, increased. Their increased release is most likely due to the loss of water and the subsequent release of water-soluble VOCs as urine ages. We suggest that these VOCs may contribute to the odor of the aged urine.

The stability of Tenax TA thermal desorption tubes in simulated field conditions on the HAPSITE® ER

Due to the growing need to monitor aircraft cabin, cockpit and breathing-line air quality, functional assessment of sampling equipment for the specialised field conditions of flight need to be established for both in-flight and ground safety. In this article, we assess the reliability of Tenax TA thermal desorption tubes to perform under various relevant field sampling conditions, such as storage temperature, loading temperature, vibrational velocity, gravitational force (G Force) and altitude pressure with semi-real-time gas chromatograph-mass spectrometer (GC-MS) analysis on the field portable HAPSITE® ER (Hazardous Air Pollutants on Site Extended Range) instrument. First, we show that Tenax TA thermal desorption tubes can handle storage under extreme environmental conditions, 4–77°C, over numerous analytical test cycles. Next, we confirm that extreme loading temperature, both hot (77°C) and cold (4°C), does not affect the analytical reliability of Tenax TA thermal desorption tubes. Then, we illustrate that G Force may have a significant (p ≤ 0.0364) effect on Tenax TA performance while vibrational velocity (p ≤ 0.7265) and low ambient air pressure (p ≤ 0.1753), such as that found at high altitude, do not. Finally, several Tenax TA thermal desorption tubes were flight-tested, demonstrating that the durability of these tubes maybe insufficient for use on military cargo aircraft (p = 0.0107). The results presented here provide a rationale for additional testing of Tenax TA thermal desorption tubes for flight suitability.

Storage stability of exhaled breath on Tenax TA

Exhaled breath is coming to the forefront of non-invasive biomarker discovery efforts. Concentration of exhaled breath volatile organic compounds (VOCs) on thermal desorption (TD) tubes with subsequent analysis by gas chromatography-mass spectrometry (GC-MS) has dominated this field. As discovery experimentation increases in frequency, the need to evaluate the long-term storage stability of exhaled breath VOCs on thermal desorption adsorbent material is critical. To address this gap, exhaled breath was loaded on Tenax TA thermal desorption tubes and stored at various temperature conditions. 74 VOCs, 56 of which have been previously uncharacterized, were monitored using GC-MS over a period of 31 d. The results suggest that storage of exhaled breath at cold temperatures (4 °C) provides the most consistent retention of exhaled breath VOCs temporally. Samples were determined to be stable up to 14 d across storage conditions prior to gaining or losing 1-2 standard deviations in abundance. Through gene set enrichment analysis (GSEA), certain chemical classes were found to be positively (acids) or negatively (sulfur-containing) enriched temporally. By means of field sample collections, the effect of storage and shipping was found to be similar to those studies preformed in the laboratory at 4 °C. Collectively this study not only provides recommendations for proper storage conditions and storage length, but also illustrates the use of GSEA to exhaled breath based GC-MS data.

Super-Absorbent Polymer Valves and Colorimetric Chemistries for Time-Sequenced Discrete Sampling and Chloride Analysis of Sweat via Skin-Mounted Soft Microfluidics

This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin-mounted microfluidic devices designed to capture, store, and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well-defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances.