Neuropeptide Y and Y1-receptor agonists increase blood flow through arteriovenous anastomoses in rat tail

1998 ◽  
Vol 85 (1) ◽  
pp. 301-309 ◽  
Author(s):  
Martha E. Heath
Keyword(s):  
Blood Flow ◽  
Neuropeptide Y ◽  
Core Temperature ◽  
Skin Blood Flow ◽  
Arteriovenous Anastomoses ◽  
Total Blood ◽  
Y1 Receptor ◽  
Pentobarbital Sodium Anesthesia ◽  
Total Blood Flow ◽  
Rat Tail

The purpose of this study was to characterize neuropeptide Y (NPY)-induced vasodilation in the rat tail. Sterile surgical technique was used (with pentobarbital sodium anesthesia) to equip rats with a jugular catheter and a blind-ended thermocouple reentrant tube next to the carotid artery. Tail skin and core temperature were measured with thermocouples during experiments. Tail skin blood flow was monitored with a laser Doppler flowmeter, and tail total blood flow and volume were measured with plethysmography. After baseline data were collected, saline, NPY (16, 32, 64, and 128 μg/kg), [Leu31Pro34]NPY (63.25 μg/kg), or NPY[13–36] (44.7 μg/kg) was administered intravenously. Tail total blood flow, volume, and tail skin temperature increased, whereas tail skin blood flow and core temperature decreased in response to both NPY- and the Y1-receptor agonist [Leu31Pro34]NPY but not in response to saline or NPY[13–36]. Studies conducted with the use of color microspheres demonstrated that arteriovenous anastomoses are involved in this NPY-induced vasodilation.

Distribution of blood flow in the perfused tracheae of sheep: a search for arteriovenous anastomoses

1993 ◽  
Vol 74 (4) ◽  
pp. 1856-1861 ◽  
Author(s):  
D. R. Corfield ◽  
S. E. Webber ◽  
J. G. Widdicombe
Keyword(s):  
Blood Flow ◽  
Smooth Muscle ◽  
Venous Blood ◽  
Systemic Blood Pressure ◽  
Arteriovenous Anastomoses ◽  
Total Blood ◽  
Arterial Inflow ◽  
Wet Weight ◽  
Cervical Trachea ◽  
Total Blood Flow

The possible existence of arteriovenous anastomoses (AVAs) in the tracheobronchial circulation has been largely ignored; however, their presence would have many implications. Here we have searched for AVAs in the tracheal circulation of seven anesthetized sheep that were ventilated through a low cervical tracheostomy. Arteries to the midcervical trachea were isolated and perfused in situ at systemic blood pressure; blood flow was measured with an electromagnetic flow probe. A vein draining the perfused segment was cannulated. Radiolabeled microspheres (16 microns diam) injected into the arterial inflow of the perfusion indicated the distribution of blood flow (cervical trachea, 69.9 +/- 4.55% (SE); esophagus, 15.1 +/- 3.9%; connective tissue and blood vessels near trachea, 9.5 +/- 1.8%; lymph nodes, 4.0 +/- 2.2%; skeletal muscle, 0.17 +/- 0.07%; trachea below intubation, 0.00%; larynx, 0.00%; other tissues 0.81 +/- 0.32%). Less than 0.6% of the activity was detected in the tracheal venous blood and lungs, indicating little shunting via AVAs. Within the trachea, blood flow (per wet weight of tissue) to the mucosa overlying smooth muscle was approximately 25% of that to the mucosa overlying cartilage. Intra-arterial infusion of methacholine doubled perfusion blood flow without altering the proportion of shunted blood. Within the trachea, blood flow increased most to the mucosa overlying smooth muscle and to smooth muscle. In conclusion the contribution of AVAs to total blood flow in the cervical trachea is < 1%.

Acute Normovolemic Hemodilution Improves Oxygenation in Ischemic Flap Tissue

2002 ◽  
Vol 96 (6) ◽  
pp. 1478-1484 ◽  
Author(s):  
Sören Schramm ◽  
Reto Wettstein ◽  
Robert Wessendorf ◽  
Stephan M. Jakob ◽  
Andrej Banic ◽  
...  
Keyword(s):  
Blood Flow ◽  
Oxygen Tension ◽  
Base Excess ◽  
Hemoglobin Concentration ◽  
Linear Increase ◽  
Control Group ◽  
Total Blood ◽  
Normovolemic Hemodilution ◽  
Total Blood Flow ◽  
Ischemic Flap

Background The flaps used in reconstructive surgery are prone to ischemia and hypoxia, which imply a considerable risk of wound-healing complications. During normovolemic hemodilution, the oxygenation may further deteriorate because of the lack of erythrocytes or improve because of increased microcirculatory blood flow. The aim of this study was to investigate the net effect of normovolemic hemodilution of various degrees on the microcirculation and oxygenation in ischemic flap tissue in adult minipigs. Methods A rectangular flap was raised in the middle of the epigastrium, consisting of an adequately perfused portion and a partly ischemic portion. The animals were randomly assigned to either the control group (n = 10) or the experimental group (n = 10) receiving graded normovolemic hemodilution with 6% hydroxyethyl starch 200-0.5. Results Normovolemic hemodilution caused a significant linear increase in total blood flow to the flap (measured by transit time flowmetry). In the ischemic flap tissue, both oxygen tension (measured by polarographic cells) and venous base excess were transiently improved during hemodilution (F = 4.79 and P = 0.019 for the regression of tissue oxygen tension on hemoglobin and hemoglobin squared, and F = 4.18 and P = 0.029 for base excess). The expected values reached a peak at hemoglobin concentrations of 9.1 and 8.5 g/dl, respectively. The measured values at this level of hemodilution were 17 +/- 10.7 mmHg (mean +/- SD) versus 7.6 +/- 1.9 mmHg (baseline) for oxygen tension and -1.7 +/- 3.4 versus -5.6 +/- 4.1 mM for venous base excess. Conclusions Our results suggest that the oxygenation in ischemic and hypoxic flap tissue may be improved by normovolemic hemodilution. The maximal benefit may be expected at a hemoglobin concentration at or slightly less than 9 g/dl.

Differences in reactive hyperemia between the intestinal mucosa and muscularis

1984 ◽  
Vol 247 (6) ◽  
pp. G617-G622
Author(s):  
A. P. Shepherd ◽  
G. L. Riedel
Keyword(s):  
Blood Flow ◽  
Metabolic Rate ◽  
Laser Doppler Velocimetry ◽  
Reactive Hyperemia ◽  
Arterial Occlusion ◽  
Oxygen Demand ◽  
Laser Doppler ◽  
Doppler Velocimetry ◽  
Total Blood ◽  
Total Blood Flow

In a previous study of regional intestinal blood flow by laser-Doppler velocimetry, we noted that the mucosa displayed reactive hyperemia following arterial occlusion but that the muscularis did not. Therefore, to determine whether this observation is generally valid, we compared responses of the mucosa and muscularis externa to arterial occlusion. We measured total blood flow to isolated loops of canine small bowel with an electromagnetic flow probe on the supply artery; blood flow either in the mucosa or in the muscularis was measured by laser-Doppler velocimetry. Mucosal and total blood flow consistently showed reactive hyperemia in response to a 60-s occlusion, but the muscularis did not. To determine whether metabolic rate influenced reactive hyperemia, we increased enteric oxygen uptake by placing 5% bile and transportable solutes in the lumen; these agents increased oxygen consumption by 36%. After a 60-s occlusion, the durations of both total and mucosal reactive hyperemia were significantly prolonged by increased metabolic rate. Similarly, the payback-to-debt ratios in both total and mucosal blood flows were significantly increased at elevated metabolic rate. These data support the conclusions that reactive hyperemia occurs more frequently and has a greater magnitude in the mucosa compared with the muscularis and both total and mucosal reactive hyperemia are strongly influenced by the preocclusive oxygen demand. These findings therefore constitute further evidence that metabolic factors contribute to reactive hyperemia in the intestinal circulation.

Peripheral blood flow during rewarming from mild hypothermia in humans

1985 ◽  
Vol 58 (1) ◽  
pp. 4-13 ◽  
Author(s):  
G. K. Savard ◽  
K. E. Cooper ◽  
W. L. Veale ◽  
T. J. Malkinson
Keyword(s):  
Blood Flow ◽  
Core Temperature ◽  
Skin Blood Flow ◽  
Cold Water ◽  
Mild Hypothermia ◽  
Muscle Blood Flow ◽  
Venous Occlusion ◽  
Warm Bath ◽  
Peripheral Blood Flow ◽  
Deep Body Temperature

During the initial stages of rewarming from hypothermia, there is a continued cooling of the core, or after-drop in temperature, that has been attributed to the return of cold blood due to peripheral vasodilatation, thus causing a further decrease of deep body temperature. To examine this possibility more carefully, subjects were immersed in cold water (17 degrees C), and then rewarmed from a mildly hypothermic state in a warm bath (40 degrees C). Measurements of hand blood flow were made by calorimetry and of forearm, calf, and foot blood flows by straingauge venous occlusion plethysmography at rest (Ta = 22 degrees C) and during rewarming. There was a small increase in skin blood flow during the falling phase of core temperature upon rewarming in the warm bath, but none in foot blood flow upon rewarming at room air, suggesting that skin blood flow seems to contribute to the after-drop, but only minimally. Limb blood flow changes during this phase suggest that a small muscle blood flow could also have contributed to the after-drop. It was concluded that the after-drop of core temperature during rewarming from mild hypothermia does not result from a large vasodilatation in the superficial parts of the periphery, as postulated. The possible contribution of mechanisms of heat conduction, heat convection, and cessation of shivering thermogenesis were discussed.

Alterations of mature arterioles associated with chronically reduced blood flow

1993 ◽  
Vol 264 (1) ◽  
pp. H40-H44 ◽  
Author(s):  
D. H. Wang ◽  
R. L. Prewitt
Keyword(s):  
Blood Flow ◽  
Vascular Wall ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Adaptive Responses ◽  
Total Blood ◽  
Cross Sectional ◽  
Old Rats ◽  
Total Blood Flow ◽  
Autoregulatory Mechanism

Adaptive responses of mature arterioles were examined after a 38% reduction in total blood flow to the cremaster muscle produced by unilateral orchidectomy in 12-wk-old rats. Four weeks later, the muscle was smaller than the contralateral cremaster, which did not increase in size during this period. Measured by closed-circuit television microscopy, the internal diameters of first- through fourth-order arterioles (1A-4A) were smaller, but wall cross-sectional area was reduced only in 3As. The smaller diameter of the 1A in the orchidectomy muscle resulted in unchanged wall shear rate. As determined from the perfusion-fixed, microfilled cremaster muscles, the total length of the arcading arterioles and the number of 3As were not statistically different, but the total number of 4As was significantly reduced on the orchidectomy side. Therefore, chronic load reduction in a mature muscle resulted in reduced blood flow, decreased number of 4As, and smaller arteriolar internal diameters in the absence of net changes in vascular wall cross-sectional area. A local autoregulatory mechanism related to flow-induced shear stress is suggested as the mechanism mediating the changes.

Effects of hyperthermia on uterine blood flow and shunting through uterine arteriovenous anastomoses in the late-pregnant ewe

1999 ◽  
Vol 11 (5) ◽  
pp. 201 ◽  
Author(s):  
Suzanne L. Miller ◽  
Graham Jenkin ◽  
David W. Walker
Keyword(s):  
Blood Flow ◽  
Experimental Period ◽  
Respiratory Alkalosis ◽  
Uterine Horn ◽  
Arteriovenous Anastomoses ◽  
Uterine Blood Flow ◽  
Ambient Conditions ◽  
Total Blood ◽  
Uterine Arteries ◽  
Pregnant Sheep

The effect of maternal hyperthermia on uterine blood flow (UBF) through the two main uterine arteries and on the proportion of UBF shunted through uterine arteriovenous anastomoses (AVAs) was investigated. Eight late-pregnant ewes were exposed to normothermic (22–23˚C) or hyperthermic (approx-imately 39˚C) ambient conditions for 8 h. UBF was measured in the left and right uterine arteries using flow probes and microspheres were injected into the uterine artery before, during and after the experimental period. The distribution of microspheres between the uterus and lungs was determined to calculate changes in capillary and AVA blood flows. Hyperthermia produced a significant (P<0.05) increase in maternal core temperature (+1.5˚C), increase in maternal blood pH (+0.21; P<0.05) and decrease in maternal pCO 2 (–16.2 mmHg; P<0.05). Blood flow to the uterine horn ipsilateral to the corpus luteum (CL) remained unchanged during hyperthermia, whereas total UBF and blood flow to the contralateral uterine horn were significantly decreased (P<0.05), by 23.1% and 20.8%, respectively, of pre-heat control values. The proportion of UBF shunted through uterine AVAs during hyperthermia was not significantly different from values observed in normothermic ewes (21.9 0.7%). Mild to moderate hyperthermia in late-pregnant sheep induces respiratory alkalosis and decreases total blood flow to the uterus, brought about by a decrease in blood flow to the uterine horn contralateral, but not ipsilateral to the CL. Heat treatment does not alter the proportion of UBF traversing uterine AVAs.

Hemodynamic Effects of CCl4 in the Intact Liver of the Cat

1974 ◽  
Vol 52 (3) ◽  
pp. 727-735 ◽  
Author(s):  
W. W. Lautt ◽  
G. L. Plaa
Keyword(s):  
Blood Flow ◽  
Hepatic Blood Flow ◽  
Sympathetic Nerves ◽  
Causative Factor ◽  
Arterial Infusion ◽  
Total Blood ◽  
Arterial Blood ◽  
Reflex Activation ◽  
Total Blood Flow ◽  
Early Phases

Blood flow in the intact liver of anesthetized cats did not change significantly over a period of 4 h following intraduodenal injection of CCl4 (1 ml/kg). Hepatocellular disruption was well underway by 2 h after the injection. Twenty-four hours following an oral dose of CCl4, the hepatic arterial resistance to blood flow was reduced and total blood flow to the liver was at least as high as in control animals. At this time, the hepatic artery appeared fully dilated and was less responsive to humoral (intra-arterial infusion of noradrenaline) and neural (reflex activation of the sympathetic nerves) constrictor influences. Thus, alterations in hepatic blood flow do not occur during the early phases of CCl4-induced hepatic injury. These data indicate that diminished blood flow is not a causative factor in the initial phases of CCl4-induced liver injury. By 24 h, hepatic blood flow is altered in such a manner that the damaged liver receives a higher proportion of arterial blood and a total blood flow that is not reduced in spite of a generally depressed cardiovascular system.

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