Imaging of Pressure- and Electrokinetically Driven Flows through Open Capillaries

1998 ◽  
Vol 70 (13) ◽  
pp. 2459-2467 ◽  
Author(s):  
P. H. Paul ◽  
M. G. Garguilo ◽  
D. J. Rakestraw
Keyword(s):  
Open Capillaries

Adenosine release during early and sustained exercise of canine skeletal muscle

1980 ◽  
Vol 238 (2) ◽  
pp. H156-H163 ◽  
Author(s):  
S. Tominaga ◽  
R. R. Curnish ◽  
L. Belardinelli ◽  
R. Rubio ◽  
R. M. Berne
Keyword(s):  
Skeletal Muscle ◽  
Specific Activity ◽  
Constant Flow ◽  
Arterial Oxygenation ◽  
Apparent Absence ◽  
Adenosine Release ◽  
Vascular Bed ◽  
Flow Perfusion ◽  
Open Capillaries ◽  
Exercise Induced

During contraction of skeletal muscle in the isolated dog hindlimb under constant-flow perfusion, the specific activity of infused [8- 14C]adenosine (nonvasoactive concn) in venous effluents decreased to 7% of the resting level in 1.25 min and was associated with a concomitant decrease in vascular resistance to 39% of the resting value. Since this decrease in specific activity of labeled adenosine could have been due to 1) an enhanced adenosine release by parenchymal tissue, 2) an exercise-induced increase in the number of open capillaries (greater surface area) in the absence of increased adenosine production 3) some degree of tissue hypoxia, or 4) a combination of these factors, experiments with maximally dilated vessels were performed. Acetylcholine and a nonvasoactive concentration of [8- 14C]adenosine were continuously infused into an isolated dog hindlimb which was perfused at constant flow during periods of rest, contraction, and recovery while arterial oxygenation was maintained at normoxic levels. Approximately 2.75 min after the onset of contraction with the vascular bed maximally dilated, the specific activity of [8- 14C]adenosine in venous effluents decreased to 38% of the resting level while the venous Po2 decreased from 78 to 42 mmHg; the value of 42 mmHg indicates apparent absence of hypoxia in the muscle. These observations are consistent with the concept that adenosine release is involved in the vasodilation observed in contraction of skeletal muscle.

Dynamics in closed and open capillaries

2019 ◽  
Vol 872 ◽  
pp. 5-38 ◽  
Author(s):  
T. S. Ramakrishnan ◽  
P. Wu ◽  
H. Zhang ◽  
D. T. Wasan
Keyword(s):  
Single Phase ◽  
Moving Boundary ◽  
Large Range ◽  
Capillary Rise ◽  
Perturbation Expansion ◽  
Viscous Drag ◽  
Experimental Conditions ◽  
Dimensionless Groups ◽  
Small Parameters ◽  
Open Capillaries

Capillary rise of a liquid displacing gas is analysed for both open and closed capillaries. We include menisci mass and hysteresis, and show that oscillations due to inertia are muted by friction at the advancing meniscus. From single-phase numerical computations in a no-slip/slip capillary, we quantify losses due to entry, flow development, meniscus slip, exit and acceleration of fluid within the reservoir. For closed capillaries, determining viscous drag due to gas requires inclusion of compressibility, and solving a moving boundary problem. This solution is derived through perturbation expansion with respect to two different small parameters for obtaining pressure above the liquid meniscus. Our rise predictions spanning a large range of experimental conditions and fluids for both open and closed capillaries match the data. The experimental data confirm the adequacy of the theoretically constructed dimensionless groups for predicting oscillatory behaviour.

Induced Response to Hypercapnia in the Two-Compartment Total Cerebral Blood Volume: Influence on Brain Vascular Reserve and Flow Efficiency

1995 ◽  
Vol 15 (6) ◽  
pp. 1121-1131 ◽  
Author(s):  
André Keyeux ◽  
Danielle Ochrymowicz-Bemelmans ◽  
André A. Charlier
Keyword(s):  
Blood Volume ◽  
Cerebral Blood Volume ◽  
Great Increase ◽  
Induced Response ◽  
Dilution Method ◽  
Main Site ◽  
Capillary Recruitment ◽  
Vascular Reserve ◽  
Blood Dilution ◽  
Open Capillaries

This study was undertaken to investigate the mechanisms of CBF increase as induced by hypercapnia. It was achieved in anesthetized rats by determining total cerebral blood volume (TCBV), parenchymal blood (CBV), plasma (CPV), erythrocyte (CEV) volumes and cerebral hematocrit (CHct) as well as CBF at about 40, 60, and 80 mm Hg Paco2. TCBV was measured by a noninvasive blood dilution method using [99mTc]pertechnetate. CBV, CPV, and CEV were measured on isolated brain by 125I-serum albumin and 51Cr-erythrocytes. CBF was measured by both [131I/14C]iodoantipyrine and 57Comicrosphere extractions. The extraparenchymal blood volume (ECBV) was evaluated by subtracting CBV from TCBV. Under normocapnia, ECBV was 2.8 times larger than CBV. Under moderate hypercapnia; ECBV increased by 44%, CBV was not modified, and CBF increased by 52%. These results demonstrate that the main site of vasodilation is located in the extraparenchymal vasculature, which thus acts as a vascular reserve. By contrast, under severe hypercapnia, ECBV remained unchanged, whereas CBV then increased by 17%; CBF simultaneously showed an additional augmentation of either 52 or 309% when diffusible tracer or microspheres were used. This important increase in CBF cannot be explained either by capillary recruitment of closed capillaries or by active diameter lengthening of already open capillaries. The concomitant and great increase in capillary blood velocity was also shown to reduce cerebral flow efficiency, a situation consistent with a “luxury perfusion.”

Number and distribution of capillaries as determinants of myocardial oxygen tension

1964 ◽  
Vol 207 (3) ◽  
pp. 653-660 ◽  
Author(s):  
Wayne W. Myers ◽  
Carl R. Honig
Keyword(s):  
Oxygen Tension ◽  
Left Ventricular ◽  
Red Cells ◽  
Tissue Oxygen ◽  
Blood Content ◽  
Left Ventricular Apex ◽  
Plasma Skimming ◽  
Oxygen Tensions ◽  
Open Capillaries ◽  
Transmural Gradient

Blood content per gram of tissue was measured in various regions of the myocardium of the dog, by use of I131-labeled albumin and Cr51O4-labeled red cells. The ratio of I131 to Cr51O4 distributions was uniform, indicating that plasma skimming does not increase O2 delivery to the inner layers. Gradients in blood content were observed from epicardium to endocardium, and in the base-apex dimension of the heart. Both the transmural gradient and the amount of blood per gram of tissue were greatest at the left ventricular apex. In this region the deeper layers contained 1.5 times as much blood as superficial ones. The data permitted estimates of the number of open capillaries, and of intercapillary distances. These estimates indicate that only a fraction of the available capillaries are perfused at rest. Mean tissue oxygen tensions were computed for various conditions of flow, capillarity, and metabolism by use of the Kety modification of the Krogh equation. Results are discussed in relation to the regulation of tissue PO2.

Fabrication of PDMS micro through-holes using micromolding in open capillaries

RSC Advances ◽  
2014 ◽  
Vol 4 (60) ◽  
pp. 31988-31993 ◽  
Author(s):  
K. Zhou ◽  
X. G. Zhu ◽  
Y. Li ◽  
J. Liu
Keyword(s):  
Open Capillaries ◽  
Simpler Method

Micromolding in open capillaries, a simpler method for PDMS through-holes fabrication, whose procedures are easy to handle and observe.

scholarly journals Transcapillary Exchange in Relation to Capillary Circulation

1968 ◽  
Vol 52 (1) ◽  
pp. 96-108 ◽  
Author(s):  
Eugene M. Renkin
Keyword(s):  
Blood Flow ◽  
Surface Area ◽  
Capillary Permeability ◽  
Flow Distribution ◽  
Effective Control ◽  
Capillary Surface ◽  
Transcapillary Exchange ◽  
Wide Range ◽  
Open Capillaries ◽  
Capillary Circulation

Transcapillary exchange of diffusible solutes depends on capillary blood flow, Q; capillary permeability, P; and capillary surface area, S. In a single capillary, the extent of equilibration of a given solute depends on the ratio of Q, to the product of P and S. In a microvascular bed consisting of many capillaries, equilibration depends on the fraction of them which are open to blood flow at any time and on the distribution of Q/PS ratios in the open capillaries. Both these characteristics are subject to control by vascular smooth muscle, particularly by the precapillary sphincters. Vasomotor mechanisms have been shown experimentally to exert a wide range of effective control over blood-tissue transport. In skeletal muscle, effective PS measured with 42K or 86Rb may be increased 8-fold from maximum nervous vasoconstriction to optimum metabolic vasodilatation. Most probably, these changes are due to differences in functional capillary surface area and of blood flow distribution relative to permeability and surface area. The extent to which variations in permeability itself can contribute to control of transcapillary exchange is not known.

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