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Considerations of Design and Data When Developing Physiologically Based Pharmacokinetic Models
Published in John C. Lipscomb, Edward V. Ohanian, Toxicokinetics and Risk Assessment, 2016
Peter J. Robinson, Jeffery M. Gearhart, Deirdre A. Mahle, Elaine A. Merrill, Teresa R. Sterner, Kyung O. Yu, John C. Lipscomb
To measure blood:air or tissue:air PCs, blood or minced tissue is smeared onto the sides of a 20 mL headspace vial [based on modifications by Gearhart et al. (22)]. Saline homogenization is unnecessary if tissues are finely minced and eliminates the need to measure saline:air PCs. The vial is sealed with a crimp cap. Reference vials receive no tissue and are crimp sealed, as well. One milliliter of headspace from a Tedlar® bag of the volatile chemical of interest at 10,000 ppm is drawn out with a gastight syringe and injected into each headspace vial (preparation of gas bag is described later). Vials are incubated at 37°C until the chemical is at equilibrium. One milliliter of headspace from each vial is drawn off and injected onto a gas chromatograph (GC). Peak areas of the chemical of interest are recorded for reference and sample vials. The PC value can be calculated using the equation: where Aref is the peak area of the reference vial as determined by GC, Vref is the volume of the reference vial, As is the peak area of the sample vial as determined by GC, and Vs is the volume of headspace in the sample vial. This equation gives the blood:air or tissue:air PC. The tissue:blood PC is mathematically derived using the equation:
Volatile organic compounds from exhaled breath in schizophrenia
Published in The World Journal of Biological Psychiatry, 2022
Carina Jiang, Henrik Dobrowolny, Dorothee Maria Gescher, Gabriela Meyer-Lotz, Johann Steiner, Christoph Hoeschen, Thomas Frodl
The breath gas analysis was performed by measuring the VOC concentrations in the breath gas of the participants via PTR-MS. Breath probes were taken from the subjects thrice, directly after awakening in the morning, after 30 and after 60 min, as awakening is a dynamic change from rest to activity. This period is chosen to investigate stability over several time points and secondly to investigate physiological dynamic changes in accordance to the cortisol awakening response, which was found to be blunted in patients with schizophrenia (Berger et al. 2016). The breath sampling was explained to participants and written instructions were handed out to them. All patients and healthy controls were capable of providing breath samples by themselves after awakening. The patients in the hospital were able to ask nurses for assistance if necessary. Participants used three Tedlar bags with special tubes to collect the breathing air. Tedlar bags can also be used at home and thus allowed measurement directly after awakening in all participants. During the hour after awakening, subjects were asked not to drink anything besides clear water, not to smoke, eat or brush their teeth. The participants stayed inside and refrained from any physical activity.
Noninvasive detection of COPD and Lung Cancer through breath analysis using MOS Sensor array based e-nose
Published in Expert Review of Molecular Diagnostics, 2021
Binson V A, M. Subramoniam, Luke Mathew
The participants selected for the study were advised to fast for a period of two hours prior to breath sampling. Tobacco smoking, mouthwashes, toothpastes, and medications were not allowed. They were asked to wait for 2 hours in a closed room to ensure that there is no interaction with exogenous VOCs and all the exhaled breath VOCs are a result of endogenous processes. The temperature inside the room is regulated at 23°C and relative humidity is also maintained between 30% and 50%. A constant heater voltage of 5 V was used to preheat MOS sensors and the repetition of this procedure was performed before each sample detection. Breath samples were collected in a 1 L Tedlar bag made of Polyvinyl fluoride (PVF). To eliminate the dead space air and collect the alveolar breath, the first collected breath was discarded [41,42]. The expelled breath samples of volunteers under study were collected in the Tedlar bag through a tube attached to it. The samples were collected from the subjects for few seconds in such a way the entire disease biomarker VOCs was collected in the sample holder. After each measurement, the sensor chamber is cleaned by applying pure nitrogen to it. The sampling circumstances were uncontrolled, ie., the impact of breath-hold, expiratory flow rate, and dead space inclusion were not considered [43].
DMTS is an effective treatment in both inhalation and injection models for cyanide poisoning using unanesthetized mice
Published in Clinical Toxicology, 2018
Susan M. DeLeon, Jason D. Downey, Diane M. Hildenberger, Melissa O. Rhoomes, Lamont Booker, Gary A. Rockwood, Kelly A. Basi
Exposures were operated by the custom-built LabVIEW program. This software controlled the timing of the exposure stages, volumetric flow rates through mass flow controllers, and switching of solenoids. Three mass flow controllers were operated by LabVIEW through a four-channel control panel (0154, Brooks Instruments, Hatfield, PA). These units controlled the flow of compressed air into the Tedlar bar, the flow of test atmospheres through the exposure system, and the purging of HCN from the system after an exposure was completed. Once an exposure was complete, flow from the Tedlar bag was sealed and ambient air was pulled through the exposure system for 60 seconds to remove any residual HCN. Once the animals were removed from the exposure system, the Tedlar bag was purged and rinsed with air before the next test atmosphere was generated. Mouse restraint tubes were airtight, to prevent dilution of test atmospheres with ambient air in the hood. Test atmospheres were pulled through the exposure system at 0.5 L/min. For these inhalation studies, toxicity was expressed as the LC50, the product of the concentration (C; ppm) of the cyanide and the length of exposure (time; min) at which 50% of the animals die.