Showing papers by "James P. Butler published in 2013"

Particle Transport and Deposition: Basic Physics of Particle Kinetics

Abstract: The human body interacts with the environment in many different ways. The lungs interact with the external environment through breathing. The enormously large surface area of the lung with its extremely thin air-blood barrier is exposed to particles suspended in the inhaled air. The particle-lung interaction may cause deleterious effects on health if the inhaled pollutant aerosols are toxic. Conversely, this interaction can be beneficial for disease treatment if the inhaled particles are therapeutic aerosolized drugs. In either case, an accurate estimation of dose and sites of deposition in the respiratory tract is fundamental to understanding subsequent biological response, and the basic physics of particle motion and engineering knowledge needed to understand these subjects is the topic of this article. A large portion of this article deals with three fundamental areas necessary to the understanding of particle transport and deposition in the respiratory tract. These are: (i) the physical characteristics of particles, (ii) particle behavior in gas flow, and (iii) gas-flow patterns in the respiratory tract. Other areas, such as particle transport in the developing lung and in the diseased lung are also considered. The article concludes with a summary and a brief discussion of areas of future research.

Propulsion and navigation within the advancing monolayer sheet

Abstract: As a wound heals, or a body plan forms, or a tumour invades, observed cellular motions within the advancing cell swarm are thought to stem from yet to be observed physical stresses that act in some direct and causal mechanical fashion. Here we show that such a relationship between motion and stress is far from direct. Using monolayer stress microscopy, we probed migration velocities, cellular tractions and intercellular stresses in an epithelial cell sheet advancing towards an island on which cells cannot adhere. We found that cells located near the island exert tractions that pull systematically towards this island regardless of whether the cells approach the island, migrate tangentially along its edge, or paradoxically, recede from it. This unanticipated cell-patterning motif, which we call kenotaxis, represents the robust and systematic mechanical drive of the cellular collective to fill unfilled space.

Monolayer Stress Microscopy: Limitations, Artifacts, and Accuracy of Recovered Intercellular Stresses

Abstract: In wound healing, tissue growth, and certain cancers, the epithelial or the endothelial monolayer sheet expands. Within the expanding monolayer sheet, migration of the individual cell is strongly guided by physical forces imposed by adjacent cells. This process is called plithotaxis and was discovered using Monolayer Stress Microscopy (MSM). MSM rests upon certain simplifying assumptions, however, concerning boundary conditions, cell material properties and system dimensionality. To assess the validity of these assumptions and to quantify associated errors, here we report new analytical, numerical, and experimental investigations. For several commonly used experimental monolayer systems, the simplifying assumptions used previously lead to errors that are shown to be quite small. Out-of-plane components of displacement and traction fields can be safely neglected, and characteristic features of intercellular stresses that underlie plithotaxis remain largely unaffected. Taken together, these findings validate Monolayer Stress Microscopy within broad but well-defined limits of applicability.

A simplified method for determining phenotypic traits in patients with obstructive sleep apnea

Abstract: We previously published a method for measuring several physiological traits causing obstructive sleep apnea (OSA). The method, however, had a relatively low success rate (76%) and required mathemat...

Single-breath xenon polarization transfer contrast (SB-XTC): Implementation and initial results in healthy humans

Abstract: Purpose: To implement and characterize a single-breath xenon transfer contrast (SB-XTC) method to assess the fractional diffusive gas transport F in the lung: to study the dependence of F and its uniformity as a function of lung volume; to estimate local alveolar surface area per unit gas volume SA/VGas from multiple diffusion time measurements of F; to evaluate the reproducibility of the measurements and the necessity of B1 correction in cases of centric and sequential encoding. Materials and Methods: In SB-XTC three or four gradient echo images separated by inversion/saturation pulses were collected during a breath-hold in eight healthy volunteers, allowing the mapping of F (thus SA/VGas) and correction for other contributions such as T1 relaxation, RF depletion and B1 inhomogeneity from inherently registered data. Results: Regional values of F and its distribution were obtained; both the mean value and heterogeneity of F increased with the decrease of lung volume. Higher values of F in the bases of the lungs in supine position were observed at lower volumes in all volunteers. Local SA/VGas (with a mean ± standard deviation of SA/VGas = 89±30 cm−1) was estimated in vivo near functional residual capacity. Calibration of SB-XTC on phantoms highlighted the necessity for B1 corrections when k-space is traversed sequentially; with centric ordering B1 distribution correction is dispensable. Conclusion: The SB-XTC technique is implemented and validated for in vivo measurements of local SA/VGas. J. Magn. Reson. Imaging 2013;37:457–470. © 2012 Wiley Periodicals, Inc.

Physiology-Based MR Imaging Assessment of CSF Flow at the Foramen Magnum with a Valsalva Maneuver

Abstract: BACKGROUND AND PURPOSE: MR imaging is currently not used to evaluate CSF flow changes due to short-lasting physiological maneuvers. The purpose of this study was to evaluate the ability of MR imaging to assess the CSF flow response to a Valsalva maneuver in healthy participants. MATERIALS AND METHODS: A cardiac-gated fast cine-PC sequence with 15-second acquisition time was used to assess CSF flow in 8 healthy participants at the foramen magnum at rest, during, and immediately after a controlled Valsalva maneuver. CSF mean displacement volume V CSF during the cardiac cycle and CSF flow waveform App were determined. A work-in-progress real-time pencil-beam imaging method with temporal resolution56 ms was used to scan 2 participants for 90 seconds during which resting, Valsalva, and post-Valsalva CSF flow, respiration, and HR were continuously recorded. Results were qualitatively compared with invasive craniospinal differential pressure measurements from the literature. RESULTS: Both methods showed 1) a decrease from baseline in V CSF and App during Valsalva and 2) an increase in V CSF and App immediately after Valsalva compared with values measured both at rest and during Valsalva. Whereas fast cine-PC produced a single CSF flow waveform that is an average over many cardiac cycles, pencil-beam imaging depicted waveforms for each heartbeat and was able to capture many dynamic features of CSF flow, including transients synchronized with the Valsalva maneuver. CONCLUSIONS: Both fast cine-PC and pencil-beam imaging demonstrated expected changes in CSF flow with Valsalva maneuver in healthy participants. The real-time capability of pencil-beam imaging may be necessary to detect Valsalva-related transient CSF flow obstruction in patients with pathologic conditions such as Chiari I malformation.

Acoustic Pharyngometry Measurement of Minimal Cross-Sectional Airway Area Is a Significant Independent Predictor of Moderate-To-Severe Obstructive Sleep Apnea

Abstract: Study Objectives:The current gold-standard method of diagnosing obstructive sleep apnea (OSA) is polysomnography, which can be inefficient. We therefore sought to determine a method to triage patie...

Glassy Dynamics, Cell Mechanics and Endothelial Permeability

Abstract: A key feature of all inflammatory processes is disruption of the vascular endothelial barrier. Such disruption is initiated in part through active contraction of the cytoskeleton of the endothelial cell (EC). Because contractile forces are propagated from cell to cell across a great many cell-cell junctions, this contractile process is strongly cooperative and highly nonlocal. We show here that the characteristic length scale of propagation is modulated by agonists and antagonists that impact permeability of the endothelial barrier. In the presence of agonists including thrombin, histamine, and H2O2, force correlation length increases, whereas in the presence of antagonists including sphingosine-1-phosphate, hepatocyte growth factor, and the rho kinase inhibitor, Y27632, force correlation length decreases. Intercellular force chains and force clusters are also evident, both of which are reminiscent of soft glassy materials approaching a glass transition.

Cumulative Risk Assessment Toolbox: Methods and Approaches for the Practitioner

Abstract: The historical approach to assessing health risks of environmental chemicals has been to evaluate them one at a time In fact, we are exposed every day to a wide variety of chemicals and are increasingly aware of potential health implications Although considerable progress has been made in the science underlying risk assessments for real-world exposures, implementation has lagged because many practitioners are unaware of methods and tools available to support these analyses To address this issue, the US Environmental Protection Agency developed a toolbox of cumulative risk resources for contaminated sites, as part of a resource document that was published in 2007 This paper highlights information for nearly 80 resources from the toolbox and provides selected updates, with practical notes for cumulative risk applications Resources are organized according to the main elements of the assessment process: (1) planning, scoping, and problem formulation; (2) environmental fate and transport; (3) exposure analysis extending to human factors; (4) toxicity analysis; and (5) risk and uncertainty characterization, including presentation of results In addition to providing online access, plans for the toolbox include addressing nonchemical stressors and applications beyond contaminated sites and further strengthening resource accessibility to support evolving analyses for cumulative risk and sustainable communities

CrossTalk opposing view: The human upper airway during sleep does not behave like a Starling resistor

Abstract: 1988).Initssimplestform,a Starling resistor is a compliant tube; theinlet and outlet pressures are specified, as isthepressureexteriortothetube.Becausetheexteriorpressureandtheupstreampressureare coupled (e.g. through lung recoil) suchasystemtypicallydisplaysthephenomenonof flow limitation. Increases in drivingand exterior pressure lead to increasesin flow, but only up to a point beyondwhich flow is constant: the system is flowlimited.Thisphenomenonhasbeenexplainedandinterpreted on a number of grounds: theequalpressurepointconceptofMead(Mead

Efficacy of white noise therapy for dementia patients with schizophrenia

Abstract: 1 Cattoir V. Actinobaculum schaalii: review of an emerging uropathogen. J Infect 2012; 4: 260–267. 2 Nielsen HL, Søby KM, Christensen JJ, Prag J. Actinobaculum schaalii: a common cause of urinary tract infection in the elderly population. Bacteriological and clinical characteristics. Scand J Infect Dis 2010; 42: 43–47. 3 Tschdin-Sutter S, Frei R, Weiser M, Goldenberger D, Widmer AF. Actinobaculum schaalii-invasive pathogen or innocent bystander? A retrospective observational study. BMC Infect Dis 2011; 11: 289. 4 Beguelin C, Genne D, Varca A et al. Actinobaculum schaalii: clinical observation of 20 cases. Clin Microbiol Infect 2011; 17: 1027–1031. 5 Álvarez-Paredes L, López-García P, Ruiz-García M, RoyoGarcía G. Infección por Actinobaculum schaalii. Enferm Infecc Microbiol Clin 2012; 30: 505–512. 6 Salvadó M, Plasencia V, Segura C et al. Infection due to Actinobaculum spp: report of 12 patients in Spain. J Infect 2013; 66: 107–109. 7 Gupta A, Gupta P, Khaira A. Actinobaculum schaalii pyelonephritis in a kidney allograft recipient. Iran J Kidney Dis 2012; 6: 386–388. 8 Gómez E, Gustafson DR, Rosenblatt JE, Patel R. Actinobaculum bacteremia: a report of 12 cases. J Clin Microbiol 2011; 49: 4311–4313. 9 Cattoir V, Varca A, Greub G, Prod’hom G, Legrand P, Lienhard R. In vitro susceptibility of Actinobaculum schaalii to 12 antimicrobial agents and molecular analysis of fluoroquinolone resistance. J Antimicrob Chemother 2010; 65: 2514– 2517.

Potential hydrodynamic origin of frictional transients in sliding mesothelial tissues

Abstract: Steady-state and transient variations in frictional force observed in tribological experiments of mesothelial tissues sliding in lubricant were analyzed with a mathematical model to test the hypothesis that such phenomena are manifestations of elastohydrodynamic lubrication and, importantly, do not require physical contact between the sliding surfaces. The model incorporates three phenomena characteristic of elastohydrodynamic lubrication: thinning of the liquid layer between sliding surfaces under a normal load (“squeeze-out”), thickening of the liquid layer due to hydrodynamic pumping, and smoothing of the elastic surfaces caused by hydrodynamic pressure gradients. Observations in soft mesothelial tissues sliding in lubricant showed variations in steady state friction with velocity, load, and lubricant viscosity. In non-steady sliding, the decay rate of frictional transients at the start of rotation varied with velocity, the amplitudes of these transients varied with the preceding periods without rotation, and frictional force varied during sinusoidal sliding. Model simulations were qualitatively similar to experimental results, supporting these mechanisms. Higher lubricant viscosity increased lubricating layer thickness and lowered friction at low speeds and increased friction at high speeds, supporting hydrodynamic pumping. We conclude that the frictional variations seen with sliding mesothelial tissues are consistent with elastohydrodynamic lubrication without contact between the sliding surfaces.

Diets of obese and non-obese older subjects

Abstract: Aim: To compare diets between obese and non-obese in healthy older subjects. Methods: Forty-five obese and eighty-seven non-obese older subjects were recruited and their habitual factors that may contribute to obesity were assessed. Intakes of food by food-group in the obesity and non-obesity groups were checked using a visual type presentation of model nutriational balance chart (MNBC). Results: Average intake ratio of food relative to ideal food intake was significantly higher in the obesity group than the non-obesity group. The relationship of obesity and exercise or habitual activities was not significant. Conclusion: Food intake is a primary factor of obesity but regular exercise or habitual activities is not a key factor for obesity in older subjects. Since exercise habit is difficult to achieve in older subjects, particularly those who are obese, food control using the present visualtype MNBC would be one strategy forthe management of obesity.

deformability in adherent endothelial cells? Is cytoskeletal tension a major determinant of cell

Abstract: You might find this additional info useful...This article cites€30 articles, 14 of which you can access for free at: http://ajpcell.physiology.org/content/274/5/C1283.full#ref-list-1This article has been cited by€20 other HighWire-hosted articles: http://ajpcell.physiology.org/content/274/5/C1283#cited-by Updated information and services including high resolution figures, can be found at: http://ajpcell.physiology.org/content/274/5/C1283.fullfound at: Additional material and information about American Journal of Physiology - Cell Physiology can behttp://www.the-aps.org/publications/ajpcellThis information is current as of February 22, 2013.

Rebuttal from James P. Butler, Robert L. Owens, Atul Malhotra and Andrew Wellman.

Abstract: We challenge the arguments presented in the ‘PRO’ side of this debate by our friends and colleagues, Schwartz & Smith (2013), in two important areas. (1) They claim that the effective peripharyngeal pressure is Pcrit. We dispute this on several grounds. Pcrit itself is a construct, most often measured by extrapolation to the intraluminal pressure that would be required to effect near or complete obstruction (Gleadhill et al. 1991). The appropriate peripharyngeal pressure for a Starling resistor would be analogous to peribronchial pressure in intrathoracic airways, which is a relatively well defined concept (Mead et al. 1970). But absent a significant stress jump across the air/tissue interface in the pharynx, there is a continuous pressure variation in the tissues from intraluminal pressure to atmospheric pressure at the body surface (Strohl et al. 2012). Thus, the very concept of an extraluminal (or tissue) pressure is vague and Fig. 1 in Schwartz & Smith (2013) is potentially misleading. (2) For infinitely compliant conduits, their claim is that, as downstream pressure decreases, flow increases up to a point of flow limitation; beyond this, flow remains constant at a plateau (Elliott & Dawson, 1977). This is true in some individuals. In others, increasingly negative downstream pressures do cause the flows to decrease, often substantially, and even, in some, to complete or near occlusion (Schwartz et al. 1988; Owens et al. 2012). This behaviour is inconsistent with the properties of a Starling resistor. When negative effort dependence (NED) is marked, their interpretation is that somehow nasal or upstream pressure (Pus) must have decreased below Pcrit. While Pus Pcrit. These ideas may suffice for a simple floppy tube, but are unable to explain the profound reductions in inspiratory airflow observed frequently in sleep apnoea patients. Finally, we remark that clinical Pcrit features (pressure gradients determining severity of obstruction, efficacy of CPAP, decreases in neuromuscular tone leading to obstruction, phenotypic factors of age, weight, sex, etc.) do not constitute evidence for Starling resistor behaviour, insofar as other models (e.g. the distributed tippy tongue model) also fits these variations as well. For us, the important features are these: (a) the simple Starling resistor does not explain the flow/pressure relationship of the upper airways in individuals with marked NED, and (b) NED is important clinically and woefully underappreciated.