Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session G30: Biological Fluid Dynamics : Lymphatic and CSF Flows |
Hide Abstracts |
Chair: Juan C. Lasheras, Universidad of California, San Diego Room: 612 |
Sunday, November 24, 2019 3:48PM - 4:01PM |
G30.00001: The Dynamics of Vesicles Driven through Closed Constrictions by Molecular Motors Youngmin Park, Thomas Fai Dendritic spines are postsynaptic processes that often appear in excitatory synaptic connections of principle neurons throughout the brain. Normal function depends on regular replenishment of various membrane proteins, which are transported on vesicles that squeeze through the spine constriction. In the present study, we explore the dynamics of that emerge in a reduced model of vesicle transport. The model predicts vesicle movement given motor transport parameters such as the ratio of competing motor forces and constriction geometry. We find that for moderately equal motor ratios and moderate constrictions, the movement may be bidirectional, and velocities gain or lose stability through sets of saddle-node bifurcations. For sufficiently tight constrictions, stable velocities vanish through a cusp bifurcation, resulting in one globally stable velocity. We explore the effects of noise on this system, and establish preliminary conditions for general force-velocity curves for vesicle trafficking. [Preview Abstract] |
Sunday, November 24, 2019 4:01PM - 4:14PM |
G30.00002: Cerebrospinal fluid influx is the earliest contributor to brain edema following stroke Jeffrey Tithof, Humberto Mestre, Ting Du, Amanda Sweeney, Guojun Liu, Logan Bashford, Edna Toro, Douglas Kelley, Maiken Nedergaard Stroke is one of the leading causes of death worldwide, affecting 10 million people annually. The most detrimental complication is cerebral edema, which is the abnormal accumulation of fluid, thought to enter the brain from the blood. However, we demonstrate that rapid influx of cerebrospinal fluid (CSF) is the principal mechanism for brain edema in the first several minutes following stroke. Specifically, we block a large artery in the brain of a living mouse and then image fluorescent CSF tracers (infused prior to the stroke). By performing particle tracking velocimetry and front tracking velocimetry, we quantify CSF influx at both microscopic and brain-wide scales, respectively. Rapid influx of CSF occurs along the glymphatic pathway, which includes periarterial spaces (annular channels surrounding arteries). Our measurements demonstrate that constriction of arteries following stroke increases the effective size of the periarterial spaces and drives influx of CSF. Our results may lead to novel treatment strategies for stroke and suggest that glymphatic edema may be an important contributor to other acute brain pathologies, such as traumatic brain injury. [Preview Abstract] |
Sunday, November 24, 2019 4:14PM - 4:27PM |
G30.00003: Hydraulic resistance of periarterial spaces in the brain John H. Thomas, Jeffrey Tithof, Douglas H. Kelley, Humberto Mestre, Maiken Nedergaard Periarterial spaces (PASs) are annular channels around arteries that carry a flow of cerebrospinal fluid (CSF) into the brain, bringing in nutrients and sweeping away metabolic waste. In vivo observations reveal that PASs are not concentric circular annuli, as often assumed, but instead are oblate and eccentric. We model the PAS cross-section as a circle (artery) surrounded by an ellipse (outer wall), and vary the area, oblateness of the ellipse, and eccentricity of the circle relative to the ellipse. This model can match observed shapes of PASs quite well. For each shape, we determine the velocity profile for steady, laminar flow and compute the corresponding hydraulic resistance. The minimum hydraulic resistance (maximum flow rate) for a given cross-sectional area occurs when the ellipse is elongated and intersects the circle, dividing the PAS into two lobes, as is common around pial arteries. If both boundaries are circular, the minimum hydraulic resistance occurs when the eccentricity is large, as is common around penetrating arteries. We show that the actual shapes of PASs are nearly optimal, offering the least hydraulic resistance for their size: this may well represent an evolutionary adaptation that maximizes the clearance of metabolic waste from the brain. [Preview Abstract] |
Sunday, November 24, 2019 4:27PM - 4:40PM |
G30.00004: Peristaltic Pumping in an Elliptical-Annulus Model of a Perivascular Space J. Brennen Carr, John H. Thomas, Jessica K. Shang Cerebrospinal fluid enters the brain parenchyma through a network of perivascular spaces (PVSs). The flow removes metabolic waste and its disruption is associated with stroke and neurodegenerative diseases. Recent in vivo experiments show that the flow is peristaltically pumped by traveling waves along the arterial wall. We simulate this “perivascular pumping” in three-dimensional models of the PVS using a finite element solver. The PVS is idealized as an annulus with a circular inner wall and an elliptical outer wall; a sine-wave displacement is propagated along the inner wall. We examine the effects of shape and eccentricity of the annulus and the amplitude and wavelength of the wave on velocity profiles and net flow rates. In contrast to the concentric circular annulus, in which the flow is axisymmetric, the velocity fields in an elliptical or eccentric annulus have an azimuthal velocity component. The net flow is in the direction of the propagated wave and is greater in elliptical and eccentric annuli than in a concentric circular annulus with the same cross-sectional area. [Preview Abstract] |
Sunday, November 24, 2019 4:40PM - 4:53PM |
G30.00005: Strain accumulation visco-elastic ventriculomegaly hypothesis for the onset of idiopathic Normal Pressure Hydrocephalus (iNPH) Stephanie Sincomb, Victor Haughton, Antonio Sanchez, Ernesto Criado-Hidalgo, Juan C Lasheras Idiopathic Normal Pressure Hydrocephalus (iNPH) also known as Chronic Adult Hydrocephalus is a syndrome characterized by ventriculomegaly, an enlargement of the brain ventricles containing cerebrospinal fluid (CSF), in the absence of elevated intracranial pressure (ICP). Symptoms of iNPH include urinary incontinence, disturbed gait, and dementia. It is most prevalent in the elderly population while extremely underdiagnosed. This condition has been subject of considerable studies, but the question remains of why while the ICP remains normal the ventricles continue to dilate despite free communication between the ventricles and the subarachnoid space. Understanding the mechanisms leading to iNPH is fundamental for its early detection and treatment. This is clinically significant as iNPH is the only potentially reversible neurodegenerative disease. Through Magnetic Resonance Elastography (MRE) measurements of the viscoelastic properties of the brain parenchyma and analytical modeling, we investigate the hypothesis that the reduction in the stiffness of the periventricular white matter and/or a decrease in its permeability leads to a gradual accumulation of the CSF in the brain ventricles and its subsequent enlargement. [Preview Abstract] |
Sunday, November 24, 2019 4:53PM - 5:06PM |
G30.00006: Numerical simulations and experiments of CSF flow in the spinal canal Candido Gutierrez-Montes, Wilfried Coenen, Jenna J Lawrence, Carlos Martinez-Bazan, Antonio L Sanchez, Juan C Lasheras Besides the oscillatory velocity driven by the cardiac and respiratory cycles, CSF flow in the spinal canal exhibits a slow steady Lagrangian motion comprising steady-streaming and Stokes-drift contributions, described in recent analytical work. Associated subject-specific descriptions of this bulk flow have revealed the existence of closed Lagrangian recirculating vortices in the lumbar, thoracic, and cervical regions. The structure of these vortices and their relevance in connection with intrathecal drug delivery (ITDD) applications are further investigated in the present study by transient numerical simulations employing a dynamic-mesh fluid-structure interaction method to account for the deformation of the dura membrane. The results show excellent agreement with the previous analytical predictions, which are further corroborated by accompanying in-vitro experiments. The description is extended to account for the buoyancy-driven motion emerging in ITDD procedures as a result of the density mismatch between the drug and the CSF. [Preview Abstract] |
Sunday, November 24, 2019 5:06PM - 5:19PM |
G30.00007: Modeling Filarial Worm Migration in Lymphatic System Ki Wolf, J. Brandon Dixon, Alexander Alexeev Lymphatic filariasis is a prevalent condition in tropical countries and is caused by intrusion of parasitic worms such as \textit{W. bancrofti}, which co-parasite between humans and mosquitoes. These parasites can leave debilitating lifelong damage to the lymphatic system. The biophysical traits that enable filarial survival within their lymphatic niche is unknown. To address this problem, we develop a fully coupled, three-dimensional fluid-solid computational model of parasite movement inside the lymphatic vessel. The model is employed to probe parasite movement under various lymph flow conditions. Worm and lymphatic valve parameters are varied to examine the parasite interactions with lymphatic valves. We compare our simulations with recent experiments on filarial movement inside the lymphatic system (Kilarski 2019). Our results provide insights into the mechanisms behind intralymphatic migration of parasitic worms during the onset and persistence of infection in filariasis. [Preview Abstract] |
Sunday, November 24, 2019 5:19PM - 5:32PM |
G30.00008: Cavitation and brain concussion Juliette Amauger, Thibault Guillet, Philippe Decq, David Quere, Christophe Clanet, Caroline Cohen A classical physics experiment consists in accelerating a closed container filled with water to form cavitation bubbles. Those bubbles nucleate in the area opposite to the point of impact and eventually, when they collapse, shatter the container. This situation mimics, to a certain end, a shock on the head of a sport player. We investigate the possibility that the collapse of cavitation bubbles in the cerebro-spinal fluid (CSF) is the underlying mechanism of mild Traumatic Brain Injury (mTBI). The occurrence of mTBI is dependent on the head acceleration $a$ and the duration of the shock $\tau $, as expressed by the empirical Wayne State Tolerance Curve (WSTC). We first observe the formation of cavitation bubbles in the contrecoup area following a shock on a water tank as a function of ($a$, $\tau )$ and show that Rayleigh-Plesset equation accurately predicts the time evolution of the bubble radius. We then explore the specificities of the system skull-CSF-brain (flow of the CSF in and out of the skull through the spinal cord, confinement of the CSF\textellipsis ). From there, we show that the energy stored in one bubble only depends on ($a$, $\tau )$ and build a phase diagram of the damaging capacity of the bubbles on the brain as a function of $a$, $\tau )$, in good agreement with the prediction of the WSTC. [Preview Abstract] |
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