In Vitro Fluid Dynamics of the St Jude Valve Prosthesis in Steady and Pulsatile Flow

1988 ◽  
Vol 17 (4) ◽  
pp. 181-187 ◽  
Author(s):  
Daniel D Hanle ◽  
Earl C Harrison ◽  
Ajit P Yoganathan ◽  
William H Corcoran
Keyword(s):  
Pulsatile Flow ◽  
Laser Doppler Anemometry ◽  
Axial Direction ◽  
Valve Prosthesis ◽  
Flow Mapping ◽  
Measurement Methodology ◽  
Instantaneous Point ◽  
Flow Through

The flow downstream from the St Jude valve prosthesis is studied in vitro in both steady and pulsatile flow. Conditions for the pulsatile flow studies approximate the in vivo resting state. Laser-Doppler anemometry (LDA) is used to measure instantaneous point velocities at numerous locations pre-selected to conform to a systematic, flow-mapping measurement methodology. Overall, the results for the St Jude valve indicate a relatively undisturbed forward flow through the prosthesis. The acceleration ratios, defined as the maximum mean axial velocity for the St Jude valve divided by that for no valve obstructing the flow, are small, being 1.2 and 1.4 for steady and pulsatile flow, respectively. Both the secondary flow structure and the flow disturbance produced by this valve are minimal. Maximum mean velocities in the radial and azimuthal directions are only about 5–10 per cent of that in the axial direction. There is, however, notable evidence of flow wakes generated by the valve's opened leaflets. Velocity defects caused by these wakes are found to be as much as 50 per cent. The bulk flow through this valve is in this sense quite unlike that reported by others for the natural aortic valve studied in vitro.

scholarly journals Design, development, testing at ISO standards and in vivo feasibility study of a novel polymeric heart valve prosthesis

2020 ◽  
Vol 8 (16) ◽  
pp. 4467-4480
Author(s):  
Joanna R. Stasiak ◽  
Marta Serrani ◽  
Eugenia Biral ◽  
James V. Taylor ◽  
Azfar G. Zaman ◽  
...  
Keyword(s):  
Heart Valve ◽  
Feasibility Study ◽  
Heart Valve Prosthesis ◽  
Valve Prosthesis ◽  
Design Development ◽  
Iso Standards ◽  
Bench Testing ◽  
Bioprosthetic Valves

A novel polymeric heart valve shows durability equivalent to 25 years in accelerated bench testing, in vitro hydrodynamics equivalent to existing bioprosthetic valves; and good performance in a small acute feasibility study in sheep.

Quantification of in vitro and in vivo energy metabolism of the gastrointestinal tract of fed or fasted sheep

1993 ◽  
Vol 73 (4) ◽  
pp. 855-868 ◽  
Author(s):  
J. M. Kelly ◽  
B. G. Southorn ◽  
C. E. Kelly ◽  
L. P. Milligan ◽  
B. W. McBride
Keyword(s):  
Blood Flow ◽  
Gastrointestinal Tract ◽  
Portal Blood Flow ◽  
Whole Body ◽  
Hepatic Portal Vein ◽  
Flow Through ◽  
Hepatic Portal ◽  
Ouabain Inhibition

The effect of level of nutrition on in vitro and in vivo O2 consumption by the gastrointestinal tract in four nonlactating, nonpregnant ewes catheterized in the anterior mesenteric vein, hepatic portal vein and mesenteric artery with duodenal cannulae was investigated. Animals were fed a pelleted ration at maintenance (M) or twice maintenance (2M) or fasted (F) subsequent to the M measurement. Duodenal in vitro O2, ouabain-sensitive O2 (OSO2) and cycloheximide-sensitive O2 (CSO2) consumption was determined polarographically using a YSI O2 monitor; whole-gut O2 consumption was determined as (arterio-venous difference of O2 concentration) × (blood flow through the PV). Whole-body O2 consumption was determined using indirect calorimetry. Ewes fed 2M exhibited higher (P < 0.10) whole-body O2 consumption than either M or F ewes. Ewes fed M and 2M had higher (P < 0.10) duodenal in vitro O2 and ouabain-insensitive O2 (OIO2) consumption than F ewes. Hepatic portal blood flow was directly proportional to level of intake (P < 0.10): it was lowest for F ewes (81.0 L h−1), intermediate for M ewes (97.7 L h−1) and highest for 2M ewes (122.5 L h−1). Ouabain inhibition of O2 consumption by portal-drained viscera (PDV) was highest in M ewes and lowest in 2M ewes (P < 0.10). CSO2 consumption by the entire PDV was not affected by level of intake, corresponding to no change in OIO2 consumption by the PDV. As a proportion of whole-body O2 consumption, total O2, OSO2 and cycloheximide-insensitive O2 consumption by the PDV was higher in F ewes than in 2M ewes (P < 0.10). Fasted ewes expended a greater proportion of whole-body O2 consumption on gastrointestinal energetics than did 2M ewes. Key words: Sheep, gastrointestinal oxygen consumption, sodium–potassium ATPase, protein synthesis

Correlation Among Shear Rate Measures in Vascular Flows

1987 ◽  
Vol 109 (1) ◽  
pp. 25-26 ◽  
Author(s):  
Morton H. Friedman ◽  
Owen J. Deters
Keyword(s):  
Shear Rate ◽  
Vessel Wall ◽  
Maximum Rate ◽  
Laser Doppler Anemometry ◽  
Rate Of Change ◽  
Flow Reversal ◽  
Flow Through ◽  
The Mean ◽  
Highly Correlated

A variety of shear rate measures have been calculated from hemodynamic data obtained by laser Doppler anemometry in flow-through casts of human aortic bifurcations. Included are measures sensitive to the mean and amplitude of the shear rate, its maximum rate of change, the duration of stasis and flow reversal near the wall, and the unidirectionality of the flow. Many of these measures are highly correlated with one another. This suggests that that it will be difficult to identify from in vivo measurements those aspects of the flow field to which the vessel wall is most sensitive. It may be possible to separate the effects of purely temporal factors (e.g., the duration of flow reversal) from those related to wall shear stress.

scholarly journals Interactions between Babesia microti merozoites and rat kidney cells in a short-term in vitro culture and animal model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marta Albertyńska ◽  
Hubert Okła ◽  
Krzysztof Jasik ◽  
Danuta Urbańska-Jasik ◽  
Przemysław Pol
Keyword(s):  
Epithelial Cells ◽  
Cross Sections ◽  
Rat Kidney ◽  
Babesia Microti ◽  
Renal Tubules ◽  
Renal Epithelial Cells ◽  
Transmission Electron ◽  
Flow Through

AbstractBabesiosis is one of the most common infections in free-living animals and is rapidly becoming significant among human zoonoses. Cases of acute renal failure in humans caused by Babesia spp. have been described in the literature. The kidneys are characterised by intense blood flow through the blood vessels, which increases the likelihood of contact with the intra-erythrocyte parasite. The aim of this study was to observe the influence of B. microti (ATCC 30221) on renal epithelial cells in vitro cultured (NRK-52E line) and Wistar rats’ kidney. Both NRK-52E cells and rats’ kidney sections were analysed by light microscopy, transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH). Necrotic changes in renal epithelial cells have been observed in vitro and in vivo. In many cross-sections through the rats’ kidney, adhesion of blood cells to the vascular endothelium, accumulation of erythrocytes and emboli were demonstrated. In NRK-52E culture, elements with a distinctly doubled cell membrane resembling B. microti were found inside the cytoplasm and adjacent to the cell layer. The study indicates a chemotactic tendency for B. microti to adhere to the renal tubules' epithelium, a possibility of piroplasms entering the renal epithelial cells, their proliferation within the cytoplasm and emboli formation.

Nonquasi-Steady Character of Pulsatile Flow in Human Coronary Arteries

1985 ◽  
Vol 107 (1) ◽  
pp. 24-28 ◽  
Author(s):  
F. F. Mark ◽  
C. B. Bargeron ◽  
O. J. Deters ◽  
M. H. Friedman
Keyword(s):  
Coronary Arteries ◽  
Pulsatile Flow ◽  
Laser Doppler Anemometry ◽  
Main Channel ◽  
Left Main ◽  
Vascular Cast ◽  
Pulsatile Flows ◽  
Flow Through ◽  
The Mean ◽  
Flow Experiments

This experiment was conducted to determine if the pulsatile flow through the proximal portion of the left coronary artery system in man exhibits quasi-steady characteristics. Steady and pulsatile flows were passed through an idealized model whose dimensions were based on a vascular cast. The mean Reynolds number was 180 and the unsteadiness number was 2.7. Velocity profiles were measured by laser Doppler anemometry at several locations along diameters in the parent and both daughter channels in the neighborhood of the “left main” bifurcation. Analysis of the results along one diameter in the “left main” channel shows that unsteady flow in the larger coronary arteries may not be simulated by a series of steady flow experiments.

scholarly journals Exosomal tau with seeding activity is released from Alzheimer’s disease synapses, and seeding potential is associated with amyloid beta

2021 ◽  
Author(s):  
Emily Miyoshi ◽  
Tina Bilousova ◽  
Mikhail Melnik ◽  
Danyl Fakhrutdinov ◽  
Wayne W. Poon ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Size Exclusion ◽  
Human Pathology ◽  
Exclusion Chromatography ◽  
Flow Through ◽  
Aggregation Size ◽  
Synaptic Vesicle Release ◽  
Induced Aggregation

AbstractSynaptic transfer of tau has long been hypothesized from the human pathology pattern and has been demonstrated in vitro and in vivo, but the precise mechanisms remain unclear. Extracellular vesicles such as exosomes have been suggested as a mechanism, but not all tau is exosomal. The present experiments use a novel flow cytometry assay to quantify depolarization of synaptosomes by KCl after loading with FM2–10, which induces a fluorescence reduction associated with synaptic vesicle release; the degree of reduction in cryopreserved human samples equaled that seen in fresh mouse synaptosomes. Depolarization induced the release of vesicles in the size range of exosomes, along with tetraspanin markers of extracellular vesicles. A number of tau peptides were released, including tau oligomers; released tau was primarily unphosphorylated and C-terminal truncated, with Aβ release just above background. When exosomes were immunopurified from release supernatants, a prominent tau band showed a dark smeared appearance of SDS-stable oligomers along with the exosomal marker syntenin-1, and these exosomes induced aggregation in the HEK tau biosensor assay. However, the flow-through did not seed aggregation. Size exclusion chromatography of purified released exosomes shows faint signals from tau in the same fractions that show a CD63 band, an exosomal size signal, and seeding activity. Crude synaptosomes from control, tauopathy, and AD cases demonstrated lower seeding in tauopathy compared to AD that is correlated with the measured Aβ42 level. These results show that AD synapses release exosomal tau that is C-terminal-truncated, oligomeric, and with seeding activity that is enhanced by Aβ. Taken together with previous findings, these results are consistent with a direct prion-like heterotypic seeding of tau by Aβ within synaptic terminals, with subsequent loading of aggregated tau onto exosomes that are released and competent for tau seeding activity.

scholarly journals One and Two-Step In Vitro-In Vivo Correlations Based on USP IV Dynamic Dissolution Applied to Four Sodium Montelukast Products

Pharmaceutics ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 690
Author(s):  
Mercedes Prieto-Escolar ◽  
Juan J. Torrado ◽  
Covadonga Álvarez ◽  
Alejandro Ruiz-Picazo ◽  
Marta Simón-Vázquez ◽  
...  
Keyword(s):  
Test Procedure ◽  
Sodium Dodecyl ◽  
Weak Acid ◽  
Added Value ◽  
Time Scaling ◽  
One Step ◽  
Flow Through ◽  
Low Solubility

Montelukast is a weak acid drug characterized by its low solubility in the range of pH 1.2 to 4.5, which may lead to dissolution-limited absorption. The aim of this paper is to develop an in vivo predictive dissolution method for montelukast and to check its performance by establishing a level-A in vitro-in vivo correlation (IVIVC). During the development of a generic film-coated tablet formulation, two clinical trials were done with three different experimental formulations to achieve a similar formulation to the reference one. A dissolution test procedure with a flow-through cell (USP IV) was used to predict the in vivo absorption behavior. The method proposed is based on a flow rate of 5 mL/min and changes of pH mediums from 1.2 to 4.5 and then to 6.8 with standard pharmacopoeia buffers. In order to improve the dissolution of montelukast, sodium dodecyl sulfate was added to the 4.5 and 6.8 pH mediums. Dissolution profiles in from the new method were used to develop a level-A IVIVC. One-step level-A IVIVC was developed from dissolution profiles and fractions absorbed obtained by the Loo–Riegelman method. Time scaling with Levy’s plot was necessary to achieve a linear IVIVC. One-step differential equation-based IVIVC was also developed with a time-scaling function. The developed method showed similar results to a previously proposed biopredictive method for montelukast, and the added value showed the ability to discriminate among different release rates in vitro, matching the in vivo clinical bioequivalence results.

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