Contributions of pressure and flow sensitivity to autoregulation in mesenteric arterioles

1976 ◽  
Vol 231 (6) ◽  
pp. 1686-1698 ◽  
Author(s):  
PC Johnson ◽  
M Intaglietta
Keyword(s):  
Arterial Pressure ◽  
Static Pressure ◽  
Volume Flow ◽  
Relative Influence ◽  
Pressure Reduction ◽  
Flow Sensitivity ◽  
Stepwise Reduction ◽  
Fourth Series ◽  
Series Of Experiments ◽  
Intravascular Pressure

The relative influence of presence and flow on dilation of arterioles with pressure reduction was examined in preparations of cat mesentery. Erythrocyte velocity and diameter were measured in individual arterioles during stepwise reduction in mesenteric arterial pressure. Volume flow was calculated from velocity and diameter data. Approximately half of the arterioles which dilated with pressure reduction also showed an increase in volume flow. In a second series of experiments, a graded reduction of flow in single arterioles was produced by local downstream occlusion. Graded occlusion caused dilation. In a third series, flow in single arterioles was completely stopped by downstream occlusion, and arterial pressure was then lowered. Most arterioles dilated with pressure reduction. In a fourth series, flow in the total preparation was completely stopped and static intravascular pressure set by a reservoir. Elevation of static pressure typically produced arteriolar constriction. We conclude from these studies that the mesenteric arteriole is sensitive both to intravascular pressure and flow, with the former probably more important than the latter in the phenomenon of autoregulation.

Diameter, wall tension, and flow in mesenteric arterioles during autoregulation

1981 ◽  
Vol 241 (6) ◽  
pp. H829-H837 ◽  
Author(s):  
M. E. Burrows ◽  
P. C. Johnson
Keyword(s):  
Arterial Pressure ◽  
Average Diameter ◽  
Vessel Diameter ◽  
Flow Regulation ◽  
Blood Velocity ◽  
Volume Flow ◽  
Wall Tension ◽  
Pressure Data ◽  
Dependent Mechanism ◽  
Intravascular Pressure

The effect of arterial pressure on vessel diameter, blood velocity, and intravascular pressure was examined in cat mesenteric arterioles in the arterial pressure range of 120—40 mmHg. Circumferential wall tension and volume flow in individual vessels were calculated. Twenty-nine arterioles with an average diameter of 25.1 micrometers were studied. Twenty-six reactive vessels dilated by an average of 6.5 micrometers with arterial pressure reduction, whereas three nonreactive arterioles narrowed by an average of 5.9 micrometers. When pressure was reduced, circumferential wall tension in reactive arterioles tended to be maintained, whereas in nonreactive vessels tension decreased more than pressure. Data from 25 of 26 reactive arterioles were consistent with the hypothesis that regulation of wall tension accounts for the autoregulatory response; however, in 18 of these vessels a flow-dependent mechanism could also account for the response. Thus the hypothesis that wall tension is a controlled variable responsible for autoregulation is supported, but an important role for flow regulation in local control is also supported.

L-arginine analogues inhibit aldosterone secretion in rats

1995 ◽  
Vol 268 (5) ◽  
pp. R1137-R1142 ◽  
Author(s):  
J. C. Simmons ◽  
R. H. Freeman
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Methyl Ester ◽  
Arterial Pressure ◽  
Plasma Renin Activity ◽  
Plasma Renin ◽  
Renin Activity ◽  
Bilateral Nephrectomy ◽  
Aldosterone Secretion ◽  
Series Of Experiments

L-Arginine analogues, e.g., NG-nitro-L-arginine methyl ester (L-NAME), increase arterial pressure and suppress renin release in the rat. On the basis of these observations, it was hypothesized that L-arginine analogues also would attenuate aldosterone secretion. This hypothesis was tested in anesthetized rats treated with L-NAME or NG-nitro-L-arginine (L-NNA, 185 mumol/kg ip). The aldosterone secretion rate, plasma renin activity, and adrenal blood flow were attenuated in rats treated with L-NAME and L-NNA compared with control animals. Similar experiments were performed in anephric rats to examine the effects of L-NAME on aldosterone secretion independent of the circulating reninangiotensin system. The administration of L-NAME reduced adrenal blood flow but failed to reduce aldosterone secretion in these anephric rats. Bilateral nephrectomy reduced plasma renin activity essentially to undetectable levels in these animals. In a third series of experiments, two groups of anephric rats were infused with angiotensin II (3 micrograms/kg body wt iv) to provide a stimulus for aldosterone secretion. Aldosterone secretion and adrenal blood flow were markedly reduced in angiotensin II-infused rats pretreated with L-NAME compared with the control anephric animals infused with angiotensin II. Overall these results suggest that L-arginine analogues attenuate aldosterone secretion by inhibiting the adrenal steroidogenic effects of endogenous or exogenous angiotensin II and/or by reducing plasma levels of renin/angiotensin.

scholarly journals AN EXPERIMENTAL STUDY INTO THE CAUSE OF THE INCREASED PORTAL PRESSURE IN PORTAL CIRRHOSIS

1907 ◽  
Vol 9 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Frederick C. Herrick
Keyword(s):  
Arterial Pressure ◽  
Portal Pressure ◽  
Normal Liver ◽  
Volume Flow ◽  
Cirrhotic Liver ◽  
Return Flow ◽  
Hepatic Veins ◽  
Portal Cirrhosis ◽  
Arterial Inflow ◽  
Flow Through

1. In the liver of portal cirrhosis there is a far freer communication between the arterial and portal currents than in the normal liver. 2. Factors contributing to the increased portal pressure in portal cirrhosis are (1) the direct communication of the arterial pressure to the portal vessels through dilated capillaries, (2) the larger volume-flow of the hepatic artery in proportion to the portal flow in cirrhosis as compared to that in the normal liver. 3. A portal cirrhotic liver gives passage to an amount of portal fluid proportionate to .its weight. There is no obstruction to the portal vessels from fibrosis in the large portal cirrhotic liver. 4. From an arterial inflow there is a free return flow through the portal as well as through the hepatic veins in both normal and cirrhotic livers. 5. From a portal inflow the return is through the hepatic vein only. The Gad's theory of valves and the arterial capillary network account for this fact. 6. The portal pressure has a decided influence on the arterial volume-flow and vice versa. This influence is more marked in the cirrhotic than in the normal liver. 7. The communication of the arterial pressure to the portal pressure is an important factor in an explanation of the increased portal pressure in portal cirrhosis.

Microvascular pressure in venules of skeletal muscle during arterial pressure reduction

1986 ◽  
Vol 250 (5) ◽  
pp. H838-H845 ◽  
Author(s):  
S. D. House ◽  
P. C. Johnson
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Arterial Pressure ◽  
Pressure Gradient ◽  
Pressure Difference ◽  
Reactive Hyperemia ◽  
Sartorius Muscle ◽  
Pressure Reduction ◽  
Large Vein ◽  
The Difference

It has been suggested from whole organ studies that the viscosity of blood in skeletal muscle venules varies inversely with flow over physiological flow ranges. If this is the case, the hydrostatic pressure gradient in venules should change less than flow as flow is altered. To test this hypothesis, pressure in venules of cat sartorius muscle was measured during stepwise arterial pressure reduction to 20 mmHg. Large vein pressure remained constant at about 5 mmHg. Average pressures in the large venules (40–185 microns) ranged from 13.6 to 10.0 mmHg. The difference between pressure in these venules and large vein pressure fell in proportion to the reduction in blood pressure and blood flow. Pressures in the smallest venules studied (25 microns) averaged 19.7 +/- 6.2 (SD) mmHg. The pressure difference between the smallest venules and the large vein fell less than the arteriovenous pressure difference or blood flow when arterial pressure was reduced. During reactive hyperemia the pressure gradient between the smallest venules and the large vein rose proportionately less than blood flow. The stability of pressure in the smallest venules is consistent with the hypothesis that blood viscosity varies inversely with flow rate.

scholarly journals Effective blood pressure reduction: results of the regional program “DOVERIE”

2018 ◽  
pp. 57-63 ◽  
Author(s):  
N. V. Dobryninа ◽  
S. S. Yakushin
Keyword(s):  
Blood Pressure ◽  
Clinical Practice ◽  
Arterial Pressure ◽  
Arterial Hypertension ◽  
Generic Drugs ◽  
Blood Pressure Reduction ◽  
Pressure Reduction ◽  
Regional Study

In clinical practice, quite often the practitioner faces difficulties in correcting arterial pressure in patients with arterial hypertension. Patients mostly for various reasons prefer to be treated with generic drugs, sometimes to the detriment of the effectiveness of treatment. The regional study conducted by us clearly showed the presence of additional possibilities of the original drug Prestans (Servier, France) in reducing blood pressure compared to equivalent dosages of generic fixed combinations.

Diuretic herb Gomphrena celosioides Mart. (Amaranthaceae) promotes sustained arterial pressure reduction and protection from cardiac remodeling on rats with renovascular hypertension

2018 ◽  
Vol 224 ◽  
pp. 126-133
Author(s):  
Paulo César de Paula Vasconcelos ◽  
Cleide Adriani Signor Tirloni ◽  
Rhanany Alan Calloi Palozi ◽  
Maicon Matos Leitão ◽  
Maria Tainara Soares Carneiro ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Renovascular Hypertension ◽  
Cardiac Remodeling ◽  
Pressure Reduction ◽  
Gomphrena Celosioides

Comparison of carotid sinus baroreceptors in dogs, cats, monkeys, and rabbits

1984 ◽  
Vol 247 (1) ◽  
pp. R52-R56
Author(s):  
J. P. Gilmore ◽  
E. Tomomatsu
Keyword(s):  
Arterial Pressure ◽  
Single Unit ◽  
Static Pressure ◽  
Carotid Sinus ◽  
Lower Threshold ◽  
Threshold Pressure ◽  
Experimental Conditions ◽  
Single Unit Recordings ◽  
Sinus Pressure

Single-unit recordings were obtained from the vascularly isolated Krebs-Henseleit-perfused carotid sinus of the rabbit and cat, and the results were compared with those obtained previously from the monkey and dog. Carotid sinus pressure was altered using static pressure steps. There was a highly significant correlation between resting arterial pressure and carotid sinus baroreceptor threshold pressure. The baroreceptors of the monkey and rabbit had a significantly lower threshold than those of the dog and cat. The baroreceptors of the monkey had a significantly lower gain than those of the three nonprimates. This is the first study in which baroreceptor activity has been studied under the same experimental conditions in four different species.

Compensation to exsanguination hypotension in healthy conscious dogs

1963 ◽  
Vol 205 (5) ◽  
pp. 1000-1004 ◽  
Author(s):  
Robert F. Rushmer ◽  
Nolan Watson ◽  
Donald Harding ◽  
Donald Baker
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Human Subjects ◽  
Peripheral Resistance ◽  
Cardiovascular Responses ◽  
Systemic Arterial Pressure ◽  
Conscious Dogs ◽  
Series Of Experiments ◽  
The Mean ◽  
The Right

In some earlier studies on exsanguination hypotension in conscious dogs, reduction in systemic arterial pressure to shock levels was accompanied by a transient tachycardia during the removal of blood, but the heart rate returned to level, at or near control values during extended periods with the mean arterial pressure between 40 and 60 mm Hg. This observation stimulated a series of experiments on five healthy conscious dogs in which transient hypotension was induced by withdrawing blood from the region of the right atrium to determine which mechanisms were dominant in the compensatory reaction. A surprising degree of variability in response was encountered, such that tachycardia was the main response on some occasions, increased peripheral resistance on others, and in still others, several mechanisms appeared to play a role. Similar variability in the response to exsanguination have been reported in human subjects. These observations suggest that the baroceptor reflexes are not simple servo controls and their role in everyday cardiovascular responses should be re-examined.

Lack of time-dependent augmentation of carotid sinus baroreflex system after vagotomy

1982 ◽  
Vol 242 (4) ◽  
pp. H580-H584
Author(s):  
H. Hosomi ◽  
K. Yokoyama
Keyword(s):  
Control System ◽  
Arterial Pressure ◽  
Carotid Sinus ◽  
Pressure Control ◽  
Open Loop ◽  
Carotid Sinus Baroreflex ◽  
Stepwise Reduction ◽  
Intact Condition ◽  
Pressure Control System ◽  
Arterial Pressure Control System

The purpose of this experiment was to study whether the carotid sinus baroreflex system (CS system) increases its gain with time after vagotomy in compensation for the loss of the vagally mediated arterial pressure control system (V system). In 7 dogs anesthetized with pentobarbital sodium we determined the responsiveness of the V system by repeatedly measuring the overall open-loop gain (G) of the negative feedback control system. G was assessed as (delta API/delta APS) -- 1, where delta API and delta APS are, respectively, the immediate and steady-state falls in arterial pressure at the aortic arch following a stepwise reduction in blood volume. delta API, delta APS, and G in intact condition were -12.0 +/- 1.8 mmHg, -1.1 +/- 0.2 mmHg, and 10.1 +/- 0.7 (SD), respectively. delta API, delta APS, and G after vagotomy, i.e., G of the CS system (GCS), were -15.6 +/- 3.6 mmHg, -6.4 +/- 1.9 mmHg, and 1.6 +/- 0.4 GCS did not change with time over 4 h after vagotomy. We conclude that the CS system cannot augment its ability to restore arterial pressure in compensation for the lost function of the V system within 4 h after vagotomy in the anesthetized dog.

On Boundary Conditions for Cavitation CFD and System Dynamics of Closed Loop Channel

2011 ◽  
Author(s):  
Motohiko Nohmi ◽  
Toshiaki Ikohagi ◽  
Yuka Iga
Keyword(s):  
Boundary Conditions ◽  
System Dynamics ◽  
Flow Rate ◽  
Closed Loop ◽  
Static Pressure ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Cavitation Flow ◽  
Periodic Fluctuation ◽  
Loop Channel

The unsteady two dimensional CFD for the cavitation in a orifice passage were carried out by using a commercial software ANSYS-CFX. The mass flow rate and the static pressure were controlled at the inlet and the outlet boundaries respectively. The CFD result showed periodic fluctuation of the cavitation flow. The time derivative of the cavitation volume showed relatively good agreement with the difference of the inlet and the outlet volume flow rate. The periodic fluctuation was ceased by the extension of the passage length downstream of the cavitation. The periodic fluctuation of cavitation flow was also induced by the fluctuation of the inlet volume flow rate or the fluctuation of the outlet static pressure. The dynamic flow behavior of the closed loop system including the orifice were analyzed by using the orifice cavitation CFD with the inlet and the outlet boundary conditions derived from the lumped parameter system dynamics for the tank, the pump and the pipes in the loop.

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