Investigation of the capillary flow through open surface microfluidic structures

2017 ◽  
Author(s):  
Ahmed Taher ◽  
Benjamin Jones ◽  
Paolo Fiorini ◽  
Liesbet Lagae
Keyword(s):  
Capillary Flow ◽  
Open Surface ◽  
Flow Through

Vital microscopy of islet blood flow: catecholamine effects in normal and ob/ob mice

1987 ◽  
Vol 252 (1) ◽  
pp. E130-E135 ◽  
Author(s):  
P. Rooth ◽  
I. B. Taljedal
Keyword(s):  
Blood Flow ◽  
Capillary Flow ◽  
Inhibitory Influence ◽  
Video Recordings ◽  
Islet Blood Flow ◽  
Visible Effect ◽  
Flow Through ◽  
Vital Microscopy ◽  
Semiquantitative Method ◽  
Normal Controls

The pancreatic microcirculation in noninbred ob/ob mice and normal controls was visualized in a fluorescence microscope and examined for responses to intravenous infusions of epinephrine or norepinephrine. Evaluations of coded video recordings revealed a smooth dose-response relationship and validated a semiquantitative method of analysis. In ob/ob mice the islet microcirculation was markedly and reversibly inhibited by 0.14–4 micrograms of epinephrine X min-1 X kg body wt-1; the flow was almost totally stopped at the highest infusion rates. Capillary flow in the exocrine pancreas appeared unaffected, except for some inhibition at 4.0 micrograms X min-1 X kg-1. Norepinephrine was less potent an inhibitor of islet blood flow. Normal lean mice exhibited minor responses to 1–11.3 micrograms of epinephrine X min-1 X kg-1; in most cases there was no visible effect. It is concluded that there is a selective regulation of blood flow through the endocrine portion of the pancreas and that the islet microcirculation is hypersensitive to catecholamines in noninbred ob/ob mice. A defective inhibitory influence from the brain may play a role in the development of excessive hyperinsulinemia in ob/ob mice.

Vasomotion in chicken foot: dual innervation of arteriovenous anastomoses

1982 ◽  
Vol 242 (5) ◽  
pp. R582-R590 ◽  
Author(s):  
P. E. Hillman ◽  
N. R. Scott ◽  
A. van Tienhoven
Keyword(s):  
Capillary Flow ◽  
Arteriovenous Anastomoses ◽  
Adrenergic Agonists ◽  
Beta Adrenergic ◽  
Beta Adrenergic Agonists ◽  
Collateral Vein ◽  
Flow Through ◽  
Purinergic Nerves ◽  
Counter Current ◽  
Stimulation Of

Blood exits the foot of the domestic chicken via two major venous routes: a counter-current network surrounding the major incoming artery and a large collateral vein. Between these two routes are numerous large collateral vein. Between these two routes are numerous anastomotic veins. Both venous routes drain capillaries and arteriovenous anastomoses (AVAs). Blood flow through the foot was measured on unanesthetized hens. Flow varies with ambient temperature: 0.2 ml/min at 5 degrees C, 2.2 ml/min at thermoneutrality, and 5.4 ml/min at 36 degrees C; the AVAs contribute 8, 26, and 63% to this flow, respectively. Flow through capillaries is reduced by alpha-adrenergic agonists and is increased by beta-adrenergic agonists. Blocking nerve conduction to the foot at thermoneutrality releases alpha-adrenergic tone and increase AVA flow. Faradic stimulation of foot nerves after adrenergic blockage increases AVA flow, but not capillary flow, suggesting active vasodilation of the AVAs. Such AVA vasodilation normally occurs during body heating, since AVA flow decreases after denervation. Dopaminergic or beta-adrenergic nerves are not involved in active vasodilatation, however, purinergic nerves may play a role. Thus AVAs have a functional dual innervation.

A fractal model for capillary flow through a single tortuous capillary with roughened surfaces in fibrous porous media

Fractals ◽  
2020 ◽  
Author(s):  
Boqi Xiao ◽  
Qiwen Huang ◽  
Yan Wang ◽  
Hanxin Chen ◽  
Xubing Chen ◽  
...  
Keyword(s):  
Porous Media ◽  
Capillary Flow ◽  
Fractal Model ◽  
Fibrous Porous Media ◽  
Flow Through

Electroosmotic Flow Through Porous Materials

2014 ◽  
Author(s):  
Rakesh Saini ◽  
Matthew Kenny ◽  
Dominik P. J. Barz
Keyword(s):  
Porous Materials ◽  
Electroosmotic Flow ◽  
Capillary Flow ◽  
Cost Effective ◽  
Packed Bed ◽  
Flow Rates ◽  
Bed Porosity ◽  
Flow Through ◽  
Set Up ◽  
Air Liquid Interface

Electroosmotic flow can be employed in many microfluidic systems. Especially, highly porous materials are suitable since they generate significant flow rates and pressures. In the current research, we employ electroosmosis experiments using a relatively simple and cost-effective set-up including different sets of sintered packed beds of borosilicate micro spheres having a wider range of porosities. Various experiments are performed with varying applied electric field, and packed bed porosity. The flow rates are measured by tracking the air/liquid interface in a capillary which is connected to the packed bed. A mathematical model of the setup reveals the influence of the capillary flow on the flow rate of the electroosmotic flow.

Effects of invariant sympathetic activity on cutaneous circulatory responses to heat stress

1991 ◽  
Vol 71 (2) ◽  
pp. 521-529 ◽  
Author(s):  
D. Richardson ◽  
Q. F. Hu ◽  
S. Shepherd
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Sympathetic Activity ◽  
Capillary Flow ◽  
Local Heating ◽  
Doppler Flowmetry ◽  
Cell Velocity ◽  
Flow Through ◽  
Unanesthetized Animals ◽  
Indirect Heating

This study investigated the role of sympathetic withdrawal on blood flow responses in cutaneous arteriovenous anastomoses (AVAs) and capillaries to direct and indirect heat stress. This was achieved by clamping sympathetic activity (SC) to the tail of anesthetized rats so that constrictor tone remained invariant during exposure of either the animal's tail (direct heating) or body (indirect heating) to a 35 degrees C environment. Flow through the AVAs in the tail was evaluated by laser-Doppler flowmetry (LDF), while capillary flow was investigated by videodensitometry measurements of blood cell velocity (CBV) in single capillaries within the subepidermal vascular plexus. Both direct and indirect heating significantly increased LDF and CBV. In comparison to blood flow responses in sham-operated control rats, the SC procedure resulted in significantly lower LDF responses to both direct and indirect heat stress. By contrast, the response of CBV was not significantly affected by SC during either mode of heating. These results indicate that the withdrawal of sympathetic constrictor tone plays a role in the response of cutaneous AVAs, but not precapillary arterioles, to direct as well as indirect heat stress. Additional studies on unanesthetized animals showed that superimposing body heating on a base of local heating elicited a further increase in LDF, suggesting that local heating does not deplete neural mediated dilatory reserve.

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