Compact Mock Loops of the Systemic and Pulmonary Circulation for Blood Pump Testing

Mock loops are an important tool for in vitro investigations of artificial blood pumps. The simple windkessel, throttle, and atrium principle was used for the mock loop design presented. The components of the systemic and the pulmonary mock loop were designed according to calculated numerical simulation parameters. The loops offer a compact design and simple handling. For simulating biventricular assist or total artificial heart (TAH), both loops can be coupled correspondingly. The numerical simulation and the first results with the loops show very good similarity to physiological data of systemic and pulmonary circulation. The measurements of pump characteristics are significant for quantitative comparison of different pump sizes and types, or driving systems.

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Numerical Simulation of Steady Flow in a Two-Dimensional Total Artificial Heart Model

Journal of Biomechanical Engineering ◽

10.1115/1.2894101 ◽

1992 ◽

Vol 114 (4) ◽

pp. 497-503 ◽

Cited By ~ 13

Author(s):

S. H. Kim ◽

K. B. Chandran ◽

C. J. Chen

Keyword(s):

Numerical Simulation ◽

Artificial Heart ◽

Numerical Solutions ◽

Total Artificial Heart ◽

Reynolds Stresses ◽

Heart Chamber ◽

Simpler Algorithm ◽

Artificial Hearts ◽

Flap Valve

In this paper, a numerical simulation of steady laminar and turbulent flow in a twodimensional model for the total artificial heart is presented. A trileaflet polyurethane valve was simulated at the outflow orifice while the inflow orifice had a trileaflet or a flap valve. The finite analytic numerical method was employed to obtain solutions to the governing equations in the Cartesian coordinates. The closure for turbulence model was achieved by employing the k-ε-E model. The SIMPLER algorithm was used to solve the problem in primitive variables. The numerical solutions of the simulated model show that regions of relative stasis and trapped vortices were smaller within the ventricular chamber with the flap valve at the inflow orifice than that with the trileaflet valve. The predicted Reynolds stresses distal to the inflow valve within the ventricular chamber were also found to be smaller with the flap valve than with the trileaflet valve. These results also suggest a correlation between high turbulent stresses and the presence of thrombus in the vicinity of the valves in the total artificial hearts. The computed velocity vectors and turbulent stresses were comparable with previously reported in vitro measurements in artificial heart chambers. Analysis of the numerical solutions suggests that geometries similar to the flap valve (or a tilting disk valve) results in a better flow dynamics within the total artificial heart chamber compared to a trileaflet valve.

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Oxygen-Sensitivity and Pulmonary Selectivity of Vasodilators as Potential Drugs for Pulmonary Hypertension

Antioxidants ◽

10.3390/antiox10020155 ◽

2021 ◽

Vol 10 (2) ◽

pp. 155

Author(s):

Daniel Morales-Cano ◽

Bianca Barreira ◽

Beatriz De Olaiz Navarro ◽

María Callejo ◽

Gema Mondejar-Parreño ◽

...

Keyword(s):

Pulmonary Hypertension ◽

Gas Exchange ◽

Pulmonary Circulation ◽

Pulmonary Arteries ◽

Blood Perfusion ◽

Mesenteric Arteries ◽

Oxygen Sensitivity ◽

Low Oxygen ◽

Oxygen Selectivity

Current approved therapies for pulmonary hypertension (PH) aim to restore the balance between endothelial mediators in the pulmonary circulation. These drugs may exert vasodilator effects on poorly oxygenated vessels. This may lead to the derivation of blood perfusion towards low ventilated alveoli, i.e., producing ventilation-perfusion mismatch, with detrimental effects on gas exchange. The aim of this study is to analyze the oxygen-sensitivity in vitro of 25 drugs currently used or potentially useful for PH. Additionally, the study analyses the effectiveness of these vasodilators in the pulmonary vs. the systemic vessels. Vasodilator responses were recorded in pulmonary arteries (PA) and mesenteric arteries (MA) from rats and in human PA in a wire myograph under different oxygen concentrations. None of the studied drugs showed oxygen selectivity, being equally or more effective as vasodilators under conditions of low oxygen as compared to high oxygen levels. The drugs studied showed low pulmonary selectivity, being equally or more effective as vasodilators in systemic than in PA. A similar behavior was observed for the members within each drug family. In conclusion, none of the drugs showed optimal vasodilator profile, which may limit their therapeutic efficacy in PH.

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Optimization of numerical simulation parameters for kenaf fiber reinforced polypropylene composite by using Box-Behnken method

10.1063/5.0047550 ◽

2021 ◽

Author(s):

Dulina Tholibon ◽

Nurul Hayati Jamil ◽

Duratul Ain Tholibon

Keyword(s):

Numerical Simulation ◽

Fiber Reinforced ◽

Polypropylene Composite ◽

Kenaf Fiber ◽

Simulation Parameters

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EXTRAHEPATIC AND EXTRARENAL RENIN INACTIVATION IN THE DOG

Journal of Endocrinology ◽

10.1677/joe.0.0600217 ◽

1974 ◽

Vol 60 (2) ◽

pp. 217-222

Author(s):

R. FAGARD ◽

E. FOSSION ◽

M. CAMPFORTS ◽

A. AMERY

Keyword(s):

Blood Vessels ◽

Pulmonary Circulation ◽

Plasma Renin ◽

Glass Container ◽

Plasma Renin Concentration ◽

Vascular Beds ◽

Extrarenal Renin

SUMMARY It was demonstrated previously that renin disappears quickly from the circulation after nephrectomy in the hepatectomized dog. In the present study the plasma renin concentration (PRC) was measured in the efferent and afferent blood vessels of several vascular beds (pulmonary circulation, splanchnic region, spleen, both inferior limbs and pelvis, head) in the anhepatic and in the anhepatic and anephric dog in order to investigate extrarenal and extrahepatic renin inactivation. However, no significant arteriovenous differences in PRC could be traced. The blood of these dogs kept in vitro at 37 °C in a glass container showed no decline in PRC within 3 h of removal. Therefore no specific extrahepatic and extrarenal renin-inactivating mechanism was found which could explain the rapid disappearance of renin from the blood in vivo in the anhepatic and anephric dog.

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Numerical Simulation of Impinging Cooling on the Leading Edge of a Turbine Blade

Volume 10: Heat and Mass Transport Processes, Parts A and B ◽

10.1115/imece2011-63649 ◽

2011 ◽

Author(s):

Keyong Cheng ◽

Xiulan Huai ◽

Jun Cai ◽

Zhixiong Guo

Keyword(s):

Numerical Simulation ◽

Turbine Blade ◽

Leading Edge ◽

Critical Factor ◽

Main Stream ◽

Experimental Conditions ◽

Cooling Effectiveness ◽

Blowing Ratio ◽

Lower Temperature ◽

Simulation Parameters

In the present study, numerical simulation is carried out for impingement/effusion cooling on the leading edge of a turbine blade similar to an experimental model tested previously. The k-ε turbulence model is used, and simulation parameters are set in accordance with the experimental conditions, including temperature ratio, blowing ratio, and Reynolds number of the main stream. The accuracy and reliability of the simulation is verified by the experimental data, and the influence of various factors on fluid flow and heat transfer is analyzed in detail. The results indicate that the blowing ratio is one critical factor which affects the cooling effectiveness. The greater the blowing ratio is, the higher the cooling effectiveness is. In addition, a staggered-holes arrangement is numerically studied and compared with a line-holes arrangement. The results show that the staggered-holes arrangement has a lower temperature on the outer surface of the leading edge and has improved the cooling effectiveness.

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Potential for geothermal heat mining by analysis of the numerical simulation parameters in proposing enhanced geothermal system at bongor basin, chad

Simulation Modelling Practice and Theory ◽

10.1016/j.simpat.2020.102218 ◽

2021 ◽

Vol 107 ◽

pp. 102218

Author(s):

Kelvin Bongole ◽

Zhixue Sun ◽

Jun Yao

Keyword(s):

Numerical Simulation ◽

Geothermal System ◽

Enhanced Geothermal System ◽

Geothermal Heat ◽

Simulation Parameters

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Pulmonary circulation demonstration using an isolated rat lung model.

AJP Advances in Physiology Education ◽

10.1152/advances.1998.275.6.s85 ◽

1998 ◽

Vol 275 (6) ◽

pp. S85

Author(s):

T C Resta ◽

L M Eichinger ◽

R D Russ ◽

B R Walker

Keyword(s):

Pulmonary Circulation ◽

Lung Model ◽

Physiological Data ◽

Teaching Tool ◽

Rat Lung ◽

Laboratory Exercise ◽

Vascular Physiology ◽

Basic Concepts ◽

Isolated Rat Lung ◽

Experimental Preparation

We have developed a pulmonary circulation laboratory exercise that effectively illustrates basic concepts typically taught in a graduate physiology curriculum. The demonstration uses an isolated, perfused rat lung model to delineate the mechanisms by which pulmonary vascular resistance can be altered either passively or in an active manner by contraction or relaxation of vascular smooth muscle. The exercise further offers an opportunity to closely observe an experimental preparation commonly used to study the pulmonary circulation and allows students the opportunity to interpret the resulting physiological data. Student evaluations indicate that the demonstration was received with enthusiasm and provides an effective teaching tool for reinforcing concepts in pulmonary vascular physiology.

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By Binding CD80 and CD86, the Vaccinia Virus M2 Protein Blocks Their Interactions with both CD28 and CTLA4 and Potentiates CD80 Binding to PD-L1

Journal of Virology ◽

10.1128/jvi.00207-19 ◽

2019 ◽

Vol 93 (11) ◽

Cited By ~ 4

Author(s):

Patricia Kleinpeter ◽

Christelle Remy-Ziller ◽

Eline Winter ◽

Murielle Gantzer ◽

Virginie Nourtier ◽

...

Keyword(s):

Immune Response ◽

Vaccinia Virus ◽

Cytotoxic T Lymphocyte ◽

Myxoma Virus ◽

Parental Virus ◽

M2 Protein ◽

First Results ◽

Infected Cells

ABSTRACTIn this article we report that the M2 protein encoded by the vaccinia virus is secreted as a homo-oligomer by infected cells and binds two central costimulation molecules, CD80 (B7-1) and CD86 (B7-2). These interactions block the ligation of the two B7 proteins to both soluble CD28 and soluble cytotoxic T-lymphocyte associated protein 4 (CTLA4) but favor the binding of soluble PD-L1 to soluble CD80. M2L gene orthologues are found in several other poxviruses, and the B7-CD28/CTLA4 blocking activity has been identified for several culture supernatants of orthopoxvirus-infected cells and for a recombinant myxoma virus M2 protein homolog (i.e., Gp120-like protein, or Gp120LP). Overall, these data indicate that the M2 poxvirus family of proteins may be involved in immunosuppressive activities broader than the NF-κB inhibition already reported (R. Gedey, X. L. Jin, O. Hinthong, and J. L. Shisler, J Virol 80:8676–8685, 2006, https://doi.org/10.1128/JVI.00935-06). A Copenhagen vaccinia virus with a deletion of the nonessential M2L locus was generated and compared with its parental virus. This M2L-deleted vaccinia virus, unlike the parental virus, does not generate interference with the B7-CD28/CTLA4/PD-L1 interactions. Moreover, this deletion did not affect any key features of the virus (in vitroreplication, oncolytic activitiesin vitroandin vivo,and intratumoral expression of a transgene in an immunocompetent murine model). Altogether, these first results suggest that the M2 protein has the potential to be used as a new immunosuppressive biotherapeutic and that the M2L-deleted vaccinia virus represents an attractive new oncolytic platform with an improved immunological profile.IMPORTANCEThe vaccinia virus harbors in its genome several genes dedicated to the inhibition of the host immune response. Among them, M2L was reported to inhibit the intracellular NF-κB pathway. We report here several new putative immunosuppressive activities of M2 protein. M2 protein is secreted and binds cornerstone costimulatory molecules (CD80/CD86). M2 binding to CD80/CD86 blocks their interaction with soluble CD28/CTLA4 but also favors the soluble PD-L1-CD80 association. These findings open the way for new investigations deciphering the immune system effects of soluble M2 protein. Moreover, a vaccinia virus with a deletion of its M2L has been generated and characterized as a new oncolytic platform. The replication and oncolytic activities of the M2L-deleted vaccinia virus are indistinguishable from those of the parental virus. More investigations are needed to characterize in detail the immune response triggered against both the tumor and the virus by this M2-defective vaccinia virus.

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Glucose homeostasis and hypothalamic-pituitary-adrenocortical axis during development in rats

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1990.259.5.e601 ◽

1990 ◽

Vol 259 (5) ◽

pp. E601-E613 ◽

Cited By ~ 3

Author(s):

E. P. Widmaier

Keyword(s):

Stress Responses ◽

Adrenocorticotropic Hormone ◽

Glucose Sensor ◽

Adult Life ◽

Glucose Sensing ◽

Physiological Data ◽

Compensatory Mechanisms ◽

Definition Of

Glucoprivation represents a model stress in which activation of different stress responses at different ages can be monitored both in vivo and in vitro. Physiological data indicate rat brain contains a liver/pancreas-type glucose sensor, yet no biochemical or immunocytochemical evidence exists for such a sensor. Young rats appear to lack normal hypothalamic glucose-sensing ability and do not show typical secretory patterns of corticotropin-releasing factor, adrenocorticotropic hormone, or corticosterone after experimentally induced glucoprivation. However, they hypersecrete catecholamines and glucagon (compared with adults) and thrive on fuel sources other than glucose that are abundant after birth. High steroid levels during the first 24 h after birth may be critical for inducing gluconeogenic enzymes and promoting differentiation of tissues like pancreas. Neonatal rats also have unique control systems to combat the damaging effects of other stresses like hypoxia; these systems may disappear in adults. Thus the definition of stress may change during development, and the compensatory mechanisms employed to combat stress change from neonatal to adult life and are intricately related to the metabolic needs of the animal.

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