Vasodilation or altered perfusion pressure moves 15-micrometers spheres trapped in the gut wall

To determine whether the microsphere method for measuring the intramural distribution of intestinal blood flow is affected by perfusion pressure or vasodilation, we infused radioactive 9- and 15-micrometers spheres into adjacent segments of isolated canine small bowel. After sphere infusion the blood supply of the control loop was occluded, and the vasculature of the experimental loop was either dilated by infusing isoproterenol or was subjected to increased perfusion pressure. Intestinal segments were dissected into mucosal, submucosal, and muscularis samples. Venous blood was collected during sphere infusions and experimental perturbations. Accumulations of spheres in tissue samples and venous blood were assessed in a gamma radioactivity counter. Isoproterenol caused previously infused spheres to leave submucosa and redistributed them primarily to mucosa with few additional spheres reaching venous blood. An increase in perfusion pressure also dislodged spheres from submucosa, but these did reach venous blood. The combined estimate of mucosal plus submucosal blood flow was relatively unaffected by isoproterenol infusion but was significantly altered by increased perfusion pressure. These results have the following implications for microsphere studies of the intramural distribution of intestinal blood flow: 1) tissue must be sampled after each sphere infusion unless the possibility of sphere migration has been experimentally eliminated and 2) even a two-compartment fractionation of blood flow into muscularis and mucosal-plus-submucosal compartments is not valid under some experimental conditions.

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Clearance of 9-micron spheres and rubidium in the intestinal circulation

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1984.247.1.g13 ◽

1984 ◽

Vol 247 (1) ◽

pp. G13-G18

Author(s):

S. Gelman ◽

D. N. Granger ◽

K. Fowler ◽

L. R. Smith

Keyword(s):

Blood Flow ◽

Normal Saline ◽

Venous Pressure ◽

Venous Blood ◽

Intestinal Lumen ◽

Intestinal Loop ◽

Intestinal Segment ◽

Experimental Conditions ◽

Blood Flows ◽

Constant Rate

Rubidium clearance and 9-micron-sphere entrapment were studied and compared in isolated intestinal preparations under various physiological conditions in 10 dogs anesthetized with intravenous pentobarbital sodium. The chosen intestinal segment was pumped with aortic blood at a constant rate and pressure of about 90-100 mmHg. The temperature of the isolated loop was maintained at 37-38 degrees C with an electrical pad. A mixture of 86Rb and 9-micron-spheres labeled with 141Ce was injected into the arterial cannula supplying the intestinal loop while mesenteric venous blood was collected for activity counting. Three to four intestinal segments were used from each dog. The following three experimental conditions were randomly used for each intestinal segment preparation: 1) a mesenteric venous pressure (MVP) equaling 0 cmH2O and warmed normal saline infused into the lumen of segment; 2) an MVP equaling 0 cmH2O and 5% glucose in saline infused into the intestinal lumen; and 3) the reservoir with venous blood elevated to provide an MVP equaling 17 cmH2O and warmed normal saline infused into the intestinal lumen. A very strong and significant correlation was found between rubidium and microsphere clearances (r = 0.99, P less than 0.0001). Rubidium extraction was inversely associated with blood flow through the intestinal segment (r = 0.49, P = 0.02), while microsphere entrapment (extraction) was independent from intestinal blood flow (r = 0.16). The data suggest that the shunting of 9-micron spheres through tissue reflects the arteriovenous shunting of blood and, therefore, can be used as a tool to study the nutritive and nonnutritive blood flows in tissues.

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A nonocclusive cannula for sampling venous blood from the interscapular brown fat of conscious rats

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y86-242 ◽

1986 ◽

Vol 64 (11) ◽

pp. 1434-1439 ◽

Cited By ~ 3

Author(s):

Stephanie W. Y. Ma ◽

Brita E. NaDeau ◽

David O. Foster

Keyword(s):

Blood Flow ◽

Venous Blood ◽

Blood Flows ◽

Brown Adipose ◽

Microsphere Method ◽

Diet Induced Thermogenesis ◽

Conscious Animals ◽

Special Cannula ◽

Main Vein

Lack of an adequate method for sampling venous blood from the brown adipose tissue (BAT) of conscious animals has impeded study of the in vivo metabolism of this tissue during physiological activation of its thermogenic function. This paper describes a technique for cannulating the main vein (Sulzer's) of the interscapular BAT (IBAT) of rats in a manner that does not impair blood flow and allows multiple venous sampling over several hours in conscious animals. The technique was tested over the widest possible range of IBAT blood flows by applying it to measurements of IBAT arteriovenous O2 differences in barbital-anesthetized, cold-acclimated rats infused with vehicle or with various doses of noradrenaline. Comparison was made with controls in which samples of IBAT venous blood were obtained by cutting Sulzer's vein. Blood flow was measured by the microsphere method. These tests showed that the presence of the special cannula in Sulzer's vein had no significant effect on the blood flow, arteriovenous O2 difference, or O2 consumption of the IBAT at any level of noradrenaline-induced thermogenesis. The new technique will permit examination of the functioning of BAT in nonshivering thermogenesis and diet-induced thermogenesis under much more physiological conditions than hitherto possible. It should also significantly reduce the number of animals required for such studies.

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Gradients in fiber shortening and metabolism across ischemic left ventricular wall

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1986.250.2.h255 ◽

1986 ◽

Vol 250 (2) ◽

pp. H255-H264 ◽

Cited By ~ 5

Author(s):

F. W. Prinzen ◽

T. Arts ◽

G. J. van der Vusse ◽

W. A. Coumans ◽

R. S. Reneman

Keyword(s):

Blood Flow ◽

Perfusion Pressure ◽

Venous Blood ◽

Creatine Phosphate ◽

Left Ventricular ◽

Left Ventricular Wall ◽

Arterial Stenosis ◽

Ventricular Wall ◽

Metabolic Disturbances ◽

Ejection Phase

Blood flow, metabolism, and fiber shortening in various layers of left ventricular wall were studied during the initial 5 min of ischemia. In open-chest dogs (n = 51) ischemia was induced by coronary arterial stenosis (median value of mean perfusion pressure distal to stenosis 3.3 kPa). Epicardial deformation measurements with an inductive technique allowed estimation of fiber shortening in inner (eendo,est) and outer layers (eepi) of left ventricular free wall during the ejection phase. The decrease of eendo,est occurred within a few seconds after onset of stenosis, whereas eepi started to decrease 30 s later. After 1 min, eendo,est diminished to zero concomitantly with a reduction of blood flow and creatine phosphate content in the inner layers by 68 and 46%, respectively. In contrast a 60% reduction of eepi was associated with a decrease in blood flow of only 32% and no significant decrease in creatine phosphate in the outer layers. H+ and inorganic phosphate were released simultaneously into the local venous blood starting within 1 min of ischemia. During the initial 5 min of ischemia the content of ATP and glycogen remained unchanged across the ischemic wall. Present results indicate that the decrease of fiber shortening in the inner layers is associated with severe metabolic dearrangements, as reflected by the depletion of creatine phosphate. They also indicate that, during coronary arterial stenosis, impaired fiber shortening in the outer layers may result from the impairment of mechanical function in the inner layers, rather than from metabolic disturbances in the outer layers themselves.

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Evaluation of intestinal intramucosal pH, arterial and portal venous blood gas values, and intestinal blood flow during small intestinal ischemia and reperfusion in dogs

American Journal of Veterinary Research ◽

10.2460/ajvr.2002.63.804 ◽

2002 ◽

Vol 63 (6) ◽

pp. 804-810 ◽

Cited By ~ 5

Author(s):

Yoshinori Nezu ◽

Yoko Sakaue ◽

Yasushi Hara ◽

Shuichi Tsuchida ◽

Fumiyo Yokota ◽

...

Keyword(s):

Blood Flow ◽

Intestinal Ischemia ◽

Venous Blood ◽

Intestinal Blood Flow ◽

Ischemia And Reperfusion ◽

Blood Gas ◽

Intramucosal Ph ◽

Portal Venous Blood ◽

Small Intestinal ◽

Venous Blood Gas

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Progressively heterogeneous mismatch of regional oxygen delivery to consumption during graded coronary stenosis in pig left ventricle

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00657.2014 ◽

2015 ◽

Vol 309 (10) ◽

pp. H1708-H1719 ◽

Cited By ~ 3

Author(s):

David J. C. Alders ◽

A. B. Johan Groeneveld ◽

Thomas W. Binsl ◽

Johannes H. G. M. van Beek

Keyword(s):

Blood Flow ◽

Coronary Stenosis ◽

Oxygen Supply ◽

Perfusion Pressure ◽

Oxygen Extraction ◽

Adenosine Infusion ◽

Coronary Perfusion ◽

Metabolic Demand ◽

Tissue Samples ◽

Group I

In normal hearts, myocardial perfusion is fairly well matched to regional metabolic demand, although both are distributed heterogeneously. Nonuniform regional metabolic vulnerability during coronary stenosis would help to explain nonuniform necrosis during myocardial infarction. In the present study, we investigated whether metabolism-perfusion correlation diminishes during coronary stenosis, indicating increasing mismatch of regional oxygen supply to demand. Thirty anesthetized male pigs were studied: controls without coronary stenosis ( n = 11); group I, left anterior descending (LAD) coronary stenosis leading to coronary perfusion pressure reduction to 70 mmHg ( n = 6); group II, stenosis with perfusion pressure of about 35 mmHg ( n = 6); and group III, stenosis with perfusion pressure of 45 mmHg combined with adenosine infusion ( n = 7). [2-13C]- and [1,2-13C]acetate infusion was used to calculate regional O2 consumption from glutamate NMR spectra measured for multiple tissue samples of about 100 mg dry mass in the LAD region. Blood flow was measured with microspheres in the same regions. In control hearts without stenosis, regional oxygen extraction did not correlate with basal blood flow. Average myocardial O2 delivery and consumption decreased during coronary stenosis, but vasodilation with adenosine counteracted this. Regional oxygen extraction was on average decreased during stenosis, suggesting adaptation of metabolism to lower oxygen supply after half an hour of ischemia. Whereas regional O2 delivery correlated with O2 consumption in controls, this relation was progressively lost with graded coronary hypotension but partially reestablished by adenosine infusion. Therefore, coronary stenosis leads to heterogeneous metabolic stress indicated by decreasing regional O2 supply to demand matching in myocardium during partial coronary obstruction.

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Intestinal blood flow and oxygen uptake in the neonatal piglet during reduced perfusion pressure

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1987.252.2.g190 ◽

1987 ◽

Vol 252 (2) ◽

pp. G190-G194

Author(s):

P. T. Nowicki ◽

N. B. Hansen ◽

J. A. Menke

Keyword(s):

Blood Flow ◽

Oxygen Uptake ◽

Vascular Resistance ◽

Perfusion Pressure ◽

Intestinal Blood Flow ◽

Base Line ◽

Pressure Reduction ◽

Tissue Oxygen ◽

Newborn Piglets ◽

Severe Reduction

The effect of reduced perfusion pressure on neonatal intestinal blood flow, vascular resistance, arterio-venous oxygen content (a-v O2), and oxygen uptake was studied in nine fasted newborn piglets, aged 5-6 days. Successive reductions of intestinal perfusion pressure were achieved by a clamp on the thoracic aorta. Intestinal blood flow decreased after each reduction of perfusion pressure. Intestinal vascular resistance increased and Gf, a measure of flow control, was negative after all but the final, most severe reduction of perfusion pressure. However, intestinal a-v O2 increased after each pressure reduction and intestinal oxygen uptake was thus maintained at greater than or equal to 95% of its baseline value until perfusion pressure was reduced to less than or equal to 70% of its base-line value. The neonatal intestine maintains tissue oxygen uptake during moderate hypotension, and this is accomplished by regulation of a-v O2, rather than by regulation of blood flow.

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A venous outflow method for continuously monitoring cerebral blood flow in the rat

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1986.250.2.h304 ◽

1986 ◽

Vol 250 (2) ◽

pp. H304-H312

Author(s):

S. Morii ◽

A. C. Ngai ◽

K. R. Ko ◽

H. R. Winn

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Mean Arterial Pressure ◽

Venous Blood ◽

Tracer Technique ◽

Excellent Correlation ◽

Venous Outflow ◽

Sagittal Sinus ◽

Wide Range ◽

Microsphere Method

We analyzed the retroglenoid venous outflow (VOF) technique in the rat to document the validity of this method of measuring cerebral blood flow (CBF). Stereotypic changes in CBF were obtained with VOF during hypercarbia and hypotension. O2 content of retroglenoid venous blood did not differ significantly from O2 content of blood obtained from the sagittal sinus, suggesting minimal extracerebral contamination of the retroglenoid venous blood. This lack of extracerebral contamination was further analyzed using a double tracer technique (125I-labeled serum albumin, 22Na) that quantitated minimal extracerebral contamination in the retroglenoid vein. CBF measurements were made simultaneously using microsphere and VOF methods, and excellent correlation was found between the two techniques over a wide range of CBF during normoxia, hypoxia, and normoxic hypocarbia and hypercarbia. However, a decrease in the ratio of VOF to microsphere CBF was observed during severe normoxic hypotension (mean arterial pressure = 41 +/- 4 mmHg). VOF represented 18% of total CBF as measured by microsphere method. This study indicates that the retroglenoid outflow technique in rats is a valid method of measuring CBF.

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INTESTINAL BLOOD FLOW IN THE DOG MEASURED BY INDICATOR FRACTIONATION WITHOUT TISSUE SAMPLES

Clinical and Experimental Pharmacology and Physiology ◽

10.1111/j.1440-1681.1977.tb02620.x ◽

1977 ◽

Vol 4 (2) ◽

pp. 235-245 ◽

Cited By ~ 3

Author(s):

M. N. Eade ◽

I. R. Reid ◽

J. P. Quinn

Keyword(s):

Blood Flow ◽

Intestinal Blood Flow ◽

Tissue Samples

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Microvascular features that suggest effectors of blood-flow regulation in the brain: Evidence by SEM of corrosion casts of intracerebral vessels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100158923 ◽

1990 ◽

Vol 48 (3) ◽

pp. 274-275

Author(s):

Enrico D.F. Motti ◽

Hans-Georg Imhof ◽

Gazi M. Yasargil

Keyword(s):

Blood Flow ◽

Perfusion Pressure ◽

Corrosion Casts ◽

Cerebral Microcirculation ◽

Pial Arteries ◽

Random Occurrence ◽

Brain Arteries ◽

Homogeneous Network ◽

The Brain

Physiologists have devoted most attention in the cerebrovascular tree to the arterial side of the circulation which has been subdivided in three levels: 1) major brain arteries which keep microcirculation constant despite changes in perfusion pressure; 2) pial arteries supposed to be effectors regulating microcirculation; 3) intracerebral arteries supposed to be deprived of active cerebral blood flow regulating devices.The morphological search for microvascular effectors in the cerebrovascular bed has been elusive. The opaque substance of the brain confines in vivo investigation to the superficial pial arteries. Most morphologists had to limit their observation to the random occurrence of a favorable site in the practically two-dimensional thickness of diaphanized histological sections. It is then not surprising most investigators of the cerebral microcirculation refer to an homogeneous network of microvessels interposed between arterioles and venules.We have taken advantage of the excellent depth of focus afforded by the scanning electron microscope (SEM) to investigate corrosion casts obtained injecting a range of experimental animals with a modified Batson's acrylic mixture.

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