Hemodynamic Aspects of Obliterative Processes in Peripheral Blood Vessels—Rigid and Soft Narrowing

1992 ◽  
Vol 114 (2) ◽  
pp. 263-267 ◽  
Author(s):  
S. Einav ◽  
A. Sternberg ◽  
Z. Millo
Keyword(s):  
Blood Vessels ◽  
Peripheral Blood ◽  
Mechanical Model ◽  
Peripheral Resistance ◽  
Flow Characteristics ◽  
Energy Losses ◽  
Pulsed Flow ◽  
Flow Through ◽  
Focal Stenosis

Hemodynamic aspects of obliterative processes in peripheral blood vessels were studied on a mechanical model built of distensible tubing, with a fixed peripheral resistance, through which citrated blood was circulated by pulsatile flow. Hemodynamics of progressive focal stenosis, elongated soft stenosis, and elongated rigid stenosis were assessed. By the use of a hydrodynamic model and a series of in vitro experiments, we have measured the pressure and flow characteristics, and calculated the pressure and energy losses for the various stenotic sites. The critical stricture was found to be larger for a rigid stenosis than a soft stenosis. The length of the stenosis was also an important factor. Increasing the length of a rigid stenosis, for example, by 50 percent resulted in an increase of 25 percent in the flow through the stenosis. The energy dissipation was determined as a preferred indication for several parameters such as: pressure drop, pulsed flow, pulse rate, and the geometry and mechanical properties of the stenosis.

Flow Characteristics Inside a Transpatent Flexible Left Ventricle With Anatomical and Antianatomical Valve Orientation

2001 ◽  
Author(s):  
Olga Pierrakos ◽  
Pavlos P. Vlachos ◽  
Demetri P. Telionis
Keyword(s):  
Heart Valves ◽  
Particle Image ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Pathological Conditions ◽  
Image Velocimetry ◽  
Flow Through ◽  
Blood Elements ◽  
The Ideal

Abstract Mechanical heart valves (MHV) and the operation of heart valve replacement have evolved to a level of universal acceptance and yet, MHV implantation is not always the ideal solution. Apparently the flow through pivoted leaflets of MHVs induces a combination of flow characteristics, which are clearly conducive to clot formation and can initiate many other pathological conditions. Most in vitro studies of the flow downstream of a MHV have been conducted with the valve in the aortic position (i.e. Reul et al., 1986). Bluestein et al., (2000) used a numerical simulation and Digital Particle-Image Velocimetry (DPIV) to reveal intricate patterns of interacting shed vortices downstream of the aortic valve and demonstrated that blood elements exposed to the highest shear stresses in the immediate proximity of the MHV could be trapped within the vortices that form in the wake of the valve.

Clinical Significance of Aspirin on Blood Flow through Stenotic Blood Vessels

2011 ◽  
Vol 10 ◽  
pp. 17-24 ◽  
Author(s):  
Sapna Ratan Shah
Keyword(s):  
Blood Flow ◽  
Blood Vessels ◽  
Shape Parameter ◽  
Fluid Model ◽  
Flow Characteristics ◽  
Diabetic Patients ◽  
Two Phase ◽  
Peripheral Layer ◽  
Stenosis Severity ◽  
Flow Through

In this present study a two-phase model for the influence of aspirin on peripheral layer viscosity for physiological characteristics of blood flow through stenosed blood vessels using Casson’s fluid model has been obtained. Flow of blood with axially non-symmetric but radially symmetric stenosis geometry is considered. The non-linear pressure equations have been solved with help of boundary conditions and the results are displayed graphically for different flow characteristics. It was found that the resistance to flow decreases as stenosis shape parameter increases whereas the resistance to flow increases with increasing values of stenosis length, stenosis size and peripheral layer viscosity. The effects of stenosis severity and wall shear stress are discussed in the present computational analysis. Comparisons between the measured and computed peripheral layer viscosity profiles are favourable to the solutions. As a result it can be concluded that a regular dose of Asprin decreases the blood viscosity by diluting the blood of diabetic patients which ultimately decreases the blood pressure. For the validation of the numerical model, the computation results are compared with the experimental data and results from published literature.

Persistence of Fibrinolytic Activity in Fragments of Human Veins Cultured in Vitro

1970 ◽  
Vol 24 (01/02) ◽  
pp. 043-047 ◽  
Author(s):  
M Pandolfi
Keyword(s):  
Blood Vessels ◽  
Plasminogen Activator ◽  
Fibrinolytic Activity ◽  
Vasa Vasorum ◽  
Adult Human ◽  
Slide Technique

SummaryExplants from 5 adult human veins were cultured in a fibrinolytically inactive medium for 3 weeks and assayed for the presence of plasminogen activator by the fibrin slide technique. The explants from 3 veins showed fibrinolytic activity confined to their vasa vasorum for the whole duration of the culture; no decrease of activity was seen. The finding suggests that small blood vessels are able to synthesize plasminogen activator.

Apoptosis and proliferation ofperipheral blood T-cells as alternative processes in pathogenesis of diabetes mellitus type 1

2019 ◽  
Vol 1 (4) ◽  
pp. 16-20 ◽  
Author(s):  
A. V. Lugovaya ◽  
N. M. Kalinina ◽  
V. Ph. Mitreikin ◽  
Yu. P. Kovaltchuk ◽  
A. V. Artyomova ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
T Cells ◽  
High Risk ◽  
Peripheral Blood ◽  
Cellular Response ◽  
Proliferative Potential ◽  
Autoreactive T Cells ◽  
Alternative Processes

Apoptosis, along with proliferation, is a form of lymphocyte response to activating stimuli. In the early stages of cell differentiation, the apoptotic response prevails and it results to the formation of tolerance to inductor antigen. Mature lymphocytes proliferate in response to stimulation and it means the initial stage in the development of the immune response. Since in this case apoptosis and proliferation acts as alternative processes, their ratio can serve as a measure of the effectiveness of the cellular response to activating signals. The resistance of autoreactive T-cells to apoptosis is the main key point in the development of type 1 diabetes mellitus (T1DM). Autoreactive T-cells migrates from the bloodstream to the islet tissue of the pancreas and take an active part in b cells destruction. The resistance of autoreactive effector T-cells to apoptosis may suggest their high proliferative potential. Therefore, the comparative evaluation of apoptosis and proliferation of peripheral blood lymphocytes can give a more complete picture of their functional state and thus will help to reveal the causes of ineffective peripheral blood T-ceiis apoptosis in patients with T1DM and will help to understand more deeply the pathogenesis of the disease. in this article, the features of proliferative response of peripheral blood T-cells in patients with T1DM and in individuals with high risk of developing T1DM have been studied. Apoptosis of T-cell subpopulations has been investigated. The correlation between the apoptotic markers and the intensity of spontaneous and activation- induced in vitro T-cells proliferation of was revealed. it was determined, that autoreactive peripheral blood T-cells were resistant to apoptosis and demonstrated the increased proliferative potential in patients with T1DM and in individuals with high risk of developing T1DM.

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