scholarly journals Modeling Airflow and Particle Deposition in a Human Acinar Region

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Arun V. Kolanjiyil ◽  
Clement Kleinstreuer
Keyword(s):  
Flow Pattern ◽  
Particle Deposition ◽  
Current Model ◽  
Particle Diameter ◽  
Particle Simulation ◽  
Present System ◽  
Alveolar Region ◽  
Recirculating Flow ◽  
Wall Deformation

The alveolar region, encompassing millions of alveoli, is the most vital part of the lung. However, airflow behavior and particle deposition in that region are not fully understood because of the complex geometrical structure and intricate wall movement. Although recent investigations using 3D computer simulations have provided some valuable information, a realistic analysis of the air-particle dynamics in the acinar region is still lacking. So, to gain better physical insight, a physiologically inspired whole acinar model has been developed. Specifically, air sacs (i.e., alveoli) were attached as partial spheroids to the bifurcating airway ducts, while breathing-related wall deformation was included to simulate actual alveolar expansion and contraction. Current model predictions confirm previous notions that the location of the alveoli greatly influences the alveolar flow pattern, with recirculating flow dominant in the proximal lung region. In the midalveolar lung generations, the intensity of the recirculating flow inside alveoli decreases while radial flow increases. In the distal alveolar region, the flow pattern is completely radial. The micron/submicron particle simulation results, employing the Euler–Lagrange modeling approach, indicate that deposition depends on the inhalation conditions and particle size. Specifically, the particle deposition rate in the alveolar region increases with higher inhalation tidal volume and particle diameter. Compared to previous acinar models, the present system takes into account the entire acinar region, including both partially alveolated respiratory bronchioles as well the fully alveolated distal airways and alveolar sacs. In addition, the alveolar expansion and contraction have been calculated based on physiological breathing conditions which make it easy to compare and validate model results with in vivo lung deposition measurements. Thus, the current work can be readily incorporated into human whole-lung airway models to simulate/predict the flow dynamics of toxic or therapeutic aerosols.

scholarly journals THE INFLUENCE OF CORTISONE ON EXPERIMENTAL VIRAL INFECTION

1966 ◽  
Vol 123 (2) ◽  
pp. 309-325 ◽  
Author(s):  
K. Marilyn Smart ◽  
Edwin D. Kilbourne
Keyword(s):  
Chick Embryo ◽  
Inflammatory Response ◽  
Chorioallantoic Membrane ◽  
Allantoic Fluid ◽  
Influenza Viruses ◽  
Present System ◽  
Interferon Production ◽  
Hydrocortisone Administration ◽  
Experimental Viral Infection

A comparative study was undertaken of the pathogenesis of infection of the allantoic sac of the chick embryo with three influenza viruses of differing virulence, and of the influence of hydrocortisone on the course of infection. Judged on the basis of earlier onset and greater degree of inflammatory response and diminished survival time of infected embryos, Mel. and Lee viruses were markedly more virulent than PR8, despite the earlier appearance of virus in PR8-infected embryos. Interferon appeared first and in greater quantity in the allantoic fluid of Lee-infected embryos and latest with PR8 infection. Thus, there was no correlation of avirulence and better interferon production with the viruses under study in the present system. Furthermore, evidence obtained suggested that Lee virus ("virulent") was most susceptible to interferon action, and also that viral synthesis in the chorioallantoic membrane with PR8 ("avirulent") persisted after the appearance of interferon. The injection of hydrocortisone within 2 hr of the initiation of infection delayed the synthesis of all three viruses; had no significant effect upon the inflammatory response; and transiently inhibited the synthesis of interferon, while prolonging the survival of Lee- and Mel.-infected embryos. Late administration of hydrocortisone suppresses both the inflammatory response and the production of interferon. Only in the case of Lee virus infection did hydrocortisone administration lead to augmentation of final yields of virus with the low infection multiplicity employed in the present experiments. It is postulated that Lee virus is a better inducer of interferon because its infectivity in vivo is more rapidly inactivated. As a consequence synthesis of Lee virus is more under the control of endogenous interferon than is the case with PR8 or Mel. virus. Therefore, inhibition of interferon synthesis with hydrocortisone has a greater influence on final yields of Lee virus.

scholarly journals SARS-CoV-2-Laden Respiratory Aerosol Deposition in the Lung Alveolar-Interstitial Region Is a Potential Risk Factor for Severe Disease: A Modeling Study

2021 ◽  
Vol 11 (5) ◽  
pp. 431
Author(s):  
Sabine Hofer ◽  
Norbert Hofstätter ◽  
Albert Duschl ◽  
Martin Himly
Keyword(s):  
Risk Factor ◽  
Particle Deposition ◽  
Early Stage ◽  
Severe Disease ◽  
Ambient Air ◽  
Aerosol Deposition ◽  
Pulmonary Involvement ◽  
Mild Disease ◽  
Disease Initiation

COVID-19, predominantly a mild disease, is associated with more severe clinical manifestation upon pulmonary involvement. Virion-laden aerosols and droplets target different anatomical sites for deposition. Compared to droplets, aerosols more readily advance into the peripheral lung. We performed in silico modeling to confirm the secondary pulmonary lobules as the primary site of disease initiation. By taking different anatomical aerosol origins into consideration and reflecting aerosols from exhalation maneuvers breathing and vocalization, the physicochemical properties of generated respiratory aerosol particles were defined upon conversion to droplet nuclei by evaporation at ambient air. To provide detailed, spatially-resolved information on particle deposition in the thoracic region of the lung, a top-down refinement approach was employed. Our study presents evidence for hot spots of aerosol deposition in lung generations beyond the terminal bronchiole, with a maximum in the secondary pulmonary lobules and a high preference to the lower lobes of both lungs. In vivo, initial chest CT anomalies, the ground glass opacities, resulting from partial alveolar filling and interstitial thickening in the secondary pulmonary lobules, are likewise localized in these lung generations, with the highest frequency in both lower lobes and in the early stage of disease. Hence, our results suggest a disease initiation right there upon inhalation of virion-laden respiratory aerosols, linking the aerosol transmission route to pathogenesis associated with higher disease burden and identifying aerosol transmission as a new independent risk factor for developing a pulmonary phase with a severe outcome.

scholarly journals Numerical Simulation of the Aerosol Particle Motion in Granular Filters with Solid and Porous Granules

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 268
Author(s):  
Olga V. Soloveva ◽  
Sergei A. Solovev ◽  
Ruzil R. Yafizov
Keyword(s):  
Numerical Simulation ◽  
Aerosol Particle ◽  
Particle Deposition ◽  
Particle Diameter ◽  
Deposition Efficiency ◽  
Hydrodynamic Resistance ◽  
Hydrodynamic Properties ◽  
Granular Filters ◽  
Limiting Value ◽  
Good Agreement

In this work, a study was carried out to compare the filtering and hydrodynamic properties of granular filters with solid spherical granules and spherical granules with modifications in the form of micropores. We used the discrete element method (DEM) to construct the geometry of the filters. Models of granular filters with spherical granules with diameters of 3, 4, and 5 mm, and with porosity values of 0.439, 0.466, and 0.477, respectively, were created. The results of the numerical simulation are in good agreement with the experimental data of other authors. We created models of granular filters containing micropores with different porosity values (0.158–0.366) in order to study the micropores’ effect on the aerosol motion. The study showed that micropores contribute to a decrease in hydrodynamic resistance and an increase in particle deposition efficiency. There is also a maximum limiting value of the granule microporosity for a given aerosol particle diameter when a further increase in microporosity leads to a decrease in the deposition efficiency.

scholarly journals Unstressing intemperate models: how cold stress undermines mouse modeling

2012 ◽  
Vol 209 (6) ◽  
pp. 1069-1074 ◽  
Author(s):  
Christopher L. Karp
Keyword(s):  
Cold Stress ◽  
Biomedical Research ◽  
Current Model ◽  
Environmental Variable ◽  
Model System ◽  
Laboratory Mice ◽  
Therapeutic Approaches ◽  
Mechanistic Analysis ◽  
Mouse Modeling

Mus musculus enjoys pride of place at the center of contemporary biomedical research. Despite being the current model system of choice for in vivo mechanistic analysis, mice have clear limitations. The literature is littered with examples of therapeutic approaches that showed promise in mouse models but failed in clinical trials. More generally, mice often provide poor mimics of the human diseases being modeled. Available data suggest that the cold stress to which laboratory mice are ubiquitously subjected profoundly affects mouse physiology in ways that impair the modeling of human homeostasis and disease. Experimental attention to this key, albeit largely ignored, environmental variable is likely to have a broad transformative effect on biomedical research.

A new in vitro system for studying secondary palate development

Development ◽  
1975 ◽  
Vol 34 (2) ◽  
pp. 485-495
Author(s):  
L. Brinkley ◽  
G. Basehoar ◽  
A. Branch ◽  
J. Avery
Keyword(s):  
Gas Permeation ◽  
Present System ◽  
Embryonic Mouse ◽  
Fluid Medium ◽  
In Vitro System ◽  
Palate Development ◽  
Fixed Orientation ◽  
The Brain

An in vitro system was devised which supports palate development in partially dissected embryonic mouse heads. The heads were suspended in the culture chamber so that they were not held in a fixed orientation and were constantly surrounded with a fluid medium. Under these circumstances the developing palate must effect closure without the aid of gravitational forces. The culture medium was constantly circulated, gassed with 95% O2, 5% CO2 using hollow fiber gas permeation devices, and kept at 34°C. Swiss-Webster mouse embryos of 12 days 12–18 h (ca. 48 h prior to expected in vivo closure) or 13 days 8–14 h (ca. 24 h prior to closure) were used to test the ability of the system to support palatal development. Embryonic heads were dissected in one of two ways before culture: brain and tongue removed, or brain, tongue and mandible removed. After 24 h in culture, preparations of either age with only the brain and tongue removed had made substantially greater progress than their counterparts with the brain, tongue and mandible removed. With only the brain and tongue removed, the palatal shelves were contacting, adhered or fused in 67 % of the older embryos, whereas most of the embryos of the same age cultured with the brain, tongue and mandible removed had shelves that were not fully elevated and still separated by a moderate gap. Thus for maximal progress in the present system, the oral cavity must be intact except for the tongue.

Multiphase flow experiment and simulation for cells-on-a-chip devices

2019 ◽  
Vol 233 (4) ◽  
pp. 432-443 ◽  
Author(s):  
Meihua Zhang ◽  
Amy Zheng ◽  
Zhongquan C Zheng ◽  
Michael Zhuo Wang
Keyword(s):  
Multiphase Flow ◽  
Soft Lithography ◽  
Particle Deposition ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Density Ratio ◽  
Simulation Method ◽  
Quantitative Agreement ◽  
Geometry Model

A microfluidic-based microscale cell-culture device, or a cells-on-a-chip device, provides a well-controlled environment with physiologically realistic factors that emulate the organ-to-organ network of human body. In the microsystem, the in vivo situation can be resembled closely by controlling the chip geometry model, medium flow behavior, medium-to-cell density ratio, and other fluid dynamic parameters. This study is to develop multiphase models to carry out experiments and simulate flow in such devices. A standard soft lithography method is used to build the three-dimensional microfluidic chips. A definitely good qualitative and reasonably good quantitative agreement is obtained between the experimental and simulation results for particle velocity in the microfluidic chip, which validates the numerical simulation method. The cell deposition rate influenced by the flow shear is studied. The influence of gravity, inlet velocity, and cell injection number on cell concentrations are also investigated. Comparisons of different designs of cells-on-a-chip devices are addressed in the study. The physics of flow dynamics and related cell particle motion due to each of the above-mentioned variables are discussed. The results show that the multiphase flow model is promising to be used for simulating cell particle deposition and concentration for the purpose of design of cells-on-a-chip devices.

scholarly journals Particle Deposition Characteristics and Efficiency in Duct Air Flow over a Backward-Facing Step: Analysis of Influencing Factors

2019 ◽  
Vol 11 (3) ◽  
pp. 751
Author(s):  
Hao Lu ◽  
Li-zhi Zhang
Keyword(s):  
Particle Deposition ◽  
Air Flow ◽  
Deposition Velocity ◽  
Particle Diameter ◽  
Deposition Efficiency ◽  
Reynolds Stress Model ◽  
Expansion Ratio ◽  
Particle Model ◽  
Duct Flow ◽  
Backward Facing Step

Dry deposition of airborne particles in duct air flow over a backward-facing step (BFS) is commonly encountered in built environments and energy engineering. However, the understanding of particle deposition characteristics in BFS flow remains insufficient. Thus, this study investigated particle deposition behaviors and efficiency in BFS flow by using the Reynolds stress model and the discrete particle model. The influences of flow velocities, particle diameters, and duct expansion ratios on particle deposition characteristics were examined and analyzed. After numerical validation, particle deposition velocities, deposition efficiency, and deposition mechanisms in BFS duct flow were investigated in detail. The results showed that deposition velocity in BFS duct flow monotonically increases when particle diameter increases. Moreover, deposition velocity falls with increasing expansion ratio but rises with increasing air velocity. Deposition efficiency, the ratio of deposition velocity, and flow drag in a BFS duct is higher for small particles but lower for large particles as compared with a uniform duct. A higher particle deposition efficiency can be achieved by BFS with a smaller expansion ratio. The peak deposition efficiency can reach 33.6 times higher for 1-μm particles when the BFS expansion ratio is 4:3. Moreover, the “particle free zone” occurs for 50-μm particles in the BFS duct and is enlarged when the duct expansion ratio increases.

Methodology for the measurement of mucociliary function in the mouse by scintigraphy

2001 ◽  
Vol 90 (3) ◽  
pp. 1111-1118 ◽  
Author(s):  
W. Michael Foster ◽  
Dianne M. Walters ◽  
Malinda Longphre ◽  
Kristin Macri ◽  
Laura M. Miller
Keyword(s):  
Respiratory Tract ◽  
Lower Respiratory Tract ◽  
Particle Deposition ◽  
Time Course ◽  
Colloidal Particles ◽  
Intratracheal Instillation ◽  
Aerosol Inhalation ◽  
Mucociliary Function

The objective of the study was to develop a scintigraphic method for measurement of airway mucociliary clearance in small laboratory rodents such as the mouse. Previous investigations have characterized the secretory cell types present in the mouse airway, but analysis of the mucus transport system has been limited to in vitro examination of tissue explants or invasive in vivo measures of a single airway, the trachea. Three methods were used to deposit insoluble, radioisotopic colloidal particles: oropharyngeal aspiration, intratracheal instillation, and nose-only aerosol inhalation. The initial distribution of particles within the lower respiratory tract was visualized by γ-camera, and clearance of particles was followed intermittently over 6 h and at the conclusion, 24 h postdelivery. Subsets of mice underwent lavage for evidence of tissue inflammation, and others were restudied for reproducibility of the methods. The aspiration and instillation methods of delivery led to greater distributions of deposited activity within the lungs, i.e., ∼60–80% of the total respiratory tract radioactivity, whereas the nose-only aerosol technique attained a distribution of 32% to the lungs. However, the aerosol technique maximized the fraction of particles that cleared the airway over a 24-h period, i.e, deposited onto airway epithelial surfaces and cleared by mucociliary function such that lung retention at 24 h averaged 57% for delivery by aerosol inhalation and ≥80% for the aspiration or intratracheal instillation techniques. Particle delivery methods did not cause lung inflammation/injury with use of inflammatory cells and chemoattractant cytokines as criteria. Scintigraphy can discern particle deposition and clearance from the lower respiratory tract in the mouse, is noninvasive and reproducible, and includes the capability for restudy and lung lavage when time course or chronic treatments are being considered.

Osseoinduction Evaluation of Hydroxyapatite and Zinc Containing Hydroxyapatite Granules in Rabbits

2011 ◽  
Vol 493-494 ◽  
pp. 252-257 ◽  
Author(s):  
L. Nascimento ◽  
M. Medeiros ◽  
J. Calasans-Maia ◽  
A. Alves ◽  
Antonella M. Rossi ◽  
...  
Keyword(s):  
Histological Analysis ◽  
Bone Matrix ◽  
Fibrous Tissue ◽  
Particle Diameter ◽  
Inflammatory Cells ◽  
Giant Cells ◽  
Multinucleated Giant Cells ◽  
Ethics Commission

This study investigated the osteoinductive potential of granules of stoichiometric hydroxyapatite (HA) and 0.5% zinc containing hydroxyapatite (ZnHA) in intramuscular (IM) site of rabbit’s abdomen. The biomaterials were both used in granular form, with 75% porosity and particle diameter between 450 and 500μm, sintered at 1100°C. Both materials performed adequately on a multiparametric in vitro cytocompatibility assay, indicating their suitability for in vivo testing. After approval by the Ethics Commission on Teaching and Research in Animals, fifteen rabbits were submitted to general anesthesia, incision and tissue dilatation, and a small site was created for HA (right incision) and ZnHA (left incision) intramuscular implantation. The animals were killed after 2, 4 and 12 weeks for biomaterials and surrounding tissues removal. Histological analysis after 2 weeks revealed the presence of granulation tissue surrounding biomaterials with multinucleated giant cells and no newly formed bone for both materials. After 4 weeks there was fibrous tissue involving the material and few inflammatory cells. Following 12 weeks it was observed the presence of connective tissue surrounding the biomaterial, cellularized enough for the two experimental groups, but it was not observed the presence of bone matrix associated with the biomaterials. We conclude that both biomaterials are cytocompatible and did not present the property of osseoinduction after 12 weeks of implantation.

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