Significant Increase In Flow Research Articles

Preservation of endothelial cell structure and function by intracoronary perfluorochemical in a canine preparation of reperfusion.

To determine the effect of intracoronary perfluorochemical on endothelial cell structure and function, 16 dogs were randomized to receive either low-dose (15 ml/kg) intracoronary perfluorochemical (Fluosol-DA) or saline after 90 min of proximal occlusion of the left anterior descending coronary artery (LAD). The animals underwent reperfusion for 60 min with the introduction of perfluorochemical or saline 5 to 10 min after the onset of reperfusion. Endothelium-dependent coronary vasodilatory reserve was determined in vivo both at baseline and 1 hr after reperfusion by infusion of acetylcholine and then serotonin into the distal LAD bed in 12 animals (six in each group). Both agonists significantly increased regional flow measured by 133Xe washout in the two groups before occlusion, but at 1 hr after reperfusion only animals given perfluorochemical demonstrated a significant increase in flow. Vasodilatory reserve was assessed in vitro with cumulative dose-response curves to acetylcholine on LAD rings proximal and distal to the snare in all animals. These studies demonstrated a significant reduction in endothelial cell-mediated relaxation of epicardial arterial segments in the ischemic segment of control but not treated animals. Light microscopy revealed the presence of neutrophils within vessels in the ischemic zones in control animals only. Electron microscopy showed capillary obstruction by endothelial cell protrusions and neutrophil and red cell plugging in control animals in the ischemic region but an intact endothelium and predominantly unobstructed capillaries in treated animals. These findings suggest that the structural and functional endothelial damage after reperfusion may be prevented by the administration of intracoronary perfluorochemical after the onset of reperfusion.

The rabbit ear pedicle flap. A new model for evaluating factors affecting the circulation in flaps.

Laser Doppler flowmetry and transcutaneous oximetry were compared regarding their speed and accuracy in detecting occlusion of the artery of an experimental rabbit ear pedicle flap. The laser Doppler flowmeter showed a significant decrease in flow and the transcutaneous oximeter showed a significant decrease in oxygen tension within one minute after occlusion of the artery. A significant increase in flow was observed within one minute, and a significant increase in oxygen tension readings was observed one minute after the artery was opened. A steady state after opening the artery was reached sooner for the laser Doppler flowmeter readings. This study suggests that laser Doppler flowmetry and transcutaneous oximetry are equally fast and accurate in detecting changes in blood flow to a pedicle graft. These methods also have equally good reproducibility. Repeated clampings within a 30 min period did not affect the measured parameters.

The microvascular response of the neonatal mesentery to hypertonic feedings.

Using intravital microscopy we studied the responses of the jejunal and ileal mesenteric microcirculation to hypertonic meals in neonatal piglets. Test meals were infused through a cannulated segment of proximal jejunum. The intestinal segments were observed under conditions of controlled temperature and humidity, and the velocity of red blood cells through mesenteric arterioles was measured and blood flow calculated. Jejunal flow was not altered from baseline by saline or hypertonic mannitol infusion, while significant increases in flow were observed during hypertonic glucose infusion (3.8 X 10(-6) versus 10.7 X 10(-6) ml/s, p less than 0.01). Jejunal glucose infusion did not cause shunting from the ileal microcirculatory bed. We conclude that the infusion of hypertonic glucose causes an increase in jejunal blood flow, but does not result in a change in ileal flow. The increase in flow is a local phenomenon related to glucose absorption in neonatal piglets.

Changes in flow resistance in kidney vessels of dogs by hypothermic hyperosmotic perfusion.

Dog kidneys have been cold perfused by gravity and by nonpulsatile pressure after 24 h preservation time at 5 degrees C with normotonic Ringer's solution without drugs, Ringer's solution containing furosemide (10 mg/l), acetylcholine (100 mg/l), phentolamine (10 mg/l) or dopamine (0.2, 2 and 20 mg/l), and Ringer's solution made hypertonic (400 and 500 mosm/l) with glucose, mannitol, choline chloride or urea. Addition of the described drugs to normotonic Ringer's produced no detectable change in the perfusion rate. In contrast, a significant flow increase was constantly observed when perfusion was made with hypertonic Ringer's solutions. Flow increase was found to be dependent on the osmolarity of the perfusate but not on the kind of solute used to raise it.

On the contribution of prostaglandin-like substances to the action of bradykinin on intestinal motility and blood flow in canine jejunal loop in situ.

Blood flow and motility were studied in a canine jejunal loop in situ with intact innervation. Bradykinin was administered into a side branch of the supplying artery and indomethacin was infused intravenously 1 h before experiments. In the control group without indomethacin infusion, bradykinin 1-10 nmol/l gradually increased blood flow without significantly altering motility. Higher concentrations of bradykinin (20-100 nmol/l) augmented rhythmic contractions of the intestine. Phasic blood flow decreased during contraction and increased after relaxation, and mean blood flow increased. Bradykinin (0.2-1.0 mumol/l) caused tonic intestinal contractions. Blood flow initially increased but was soon impeded in proportion to the amplitude and duration of the tonic contractions. With intestinal muscle relaxation, blood flow increased to values markedly higher than control. In the group pretreated with indomethacin, blood flow did not increase after bradykinin administration. However, administration of PGE2 produced significant increase in flow, similar to that observed after bradykinin. Acetylcholine or isoprenaline also markedly increased blood flow. Increased intestinal motility caused by bradykinin mechanically impeded blood flow through the intestine, thus masking its direct vasodilating action. The action of bradykinin on the intestinal vascular bed is probably mediated or modulated by endogenous prostaglandin-like substances.

Effects of increasing arterial pressure on cerebral blood flow in the baboon: Influence of the sympathetic nervous system

The influence of stimulation of the cervical sympathetic chain on the response of cerebral blood flow to hypertension induced by the intravenous infusion of angiotensin was studied in anaesthetised baboons. Cerebral blood flow was measured by the intracarotid 133Xenon injection technique. Possible lesions of the blood-brain barrier were studied by injecting Evans blue towards the end of the experiment and ischaemic brain damage was assessed following perfusion fixation. In a control group of five baboons blood flow increased by 53 +/- 9% (mean +/- S.E.) from the base line values in the arterial pressure range 130-159 mm Hg. In four baboons subjected to unilateral sympathetic stimulation flow increased by 16 +/- 4% in the same pressure range. In three baboons subjected to bilateral sympathetic stimulation there were no significant increases in flow until the arterial pressure had increased above 159 mm Hg. Disruption of the blood-brain barrier in the parietooccipital regions was only seen in the control animals but not in the stimulated baboons. Ischaemic brain damage was not observed with the exception of one small lesion in a single stimulated baboon. These findings provide strong support for the observations of Bill and Linder (1976) that activation of the cervical sympathetic can modify the level at which breakthrough of cerebral blood flow occurs in association with systemic hypertension.

The Significance of Volume-Adjusting the Maximal Midexpiratory Flow in Assessing the Response to a Bronchodilator Drug

Forced expiratory spirograms were obtained before and for six hours after 25 subjects ingested ephedrine and placebo in a double-blind crossover study. Significant changes in the forced vital capacity (FVC) and the forced expiratory volume in one second (FEV1.0) were noted on days when ephedrine was administrated, while the mean forced expiratory flow during the middle half of the FVC (FEF25-75%) failed to indicate significant bronchodilation. When FVC increases after therapy with a bronchodilator drug, one is no longer measuring flow during the same volume segment and driving pressure (static transpulmonary pressure [Pst]) as before administration of the bronchodilator drug. Volume-adjusting the FEF25-75% after therapy to the same volume and Pst over which flow is being measured in the tracings before bronchodilator therapy yielded highly significant increases in flow after administration of the bronchodilator drug.

THE EFFECT OF SECRETIN AND CHOLECYSTOKININ‐PANCREOZYMIN ON THE SECRETION OF BILE IN THE ANAESTHETIZED RABBIT

Effects of secretin and Cholecystokinin-Pancreozymin (CCK-PZ) on the secretion of bile in anaesthetized rabbits have been studied. Single injections of secretin (5.0 u.kg(-1) significantly increased the flow of bile irrespectively of whether the cystic duct was free or had been tied. A sustained increase in bile flow could be obtained by the continuous infusion of secretin. Cholecystokinin-Pancreozymin was effective in increasing the bile flow in doses of 1.0 u.kg(-1). Much of the effect could be attributed to contraction of the gallbladder but a significant increase in flow could still be elicited after ligation of the cystic duct. Our findings strongly suggest that the biliary secretion in rabbits is not as different from the general pattern as has previously been suggested.

Transmural differences in myocardial blood flow and in coronary dilatory capacity in hemodiluted conscious dogs.

In 16 conscious resting dogs regional myocardial blood flow and the local coronary dilatory capacity were studied with the particle distribution technique during isovolemic hemodilution (hct = 13%). Postischemic peak coronary hyperemia following release of temporary circumflex coronary artery occlusion was used for quantification of regional coronary dilatory capacity. In hemodilution (arterial blood oxygen content less than one third of normal) left ventricular blood flow (LVBF) was 460 +/- 36 ml/100 g - min, subendocardial/subepicardial flow amounted to 1.3 +/- 0.1. During postischemic peak hyperemia LVBF increased by 33% up to 606 +/- 63 ml/100 g - min. This 33% increase in LVBF was distributed mainly to the subepicardial layer, while in the subendocardial layer there was no significant flow increase. It is concluded that the increase in heart rate and systolic coronary vascular compression in addition to the lowered arterial oxygen content lead to exhaustion of the dilatory reserve in the subendocardium during hemodilution. Therefore the remaining overall dilatory capacity is without functional significance.

The Parotid Saliva of the Alpaca (Lama pacos)

The flow rate and composition of the parotid secretion was studied in 5 alpacas at 3 different periods; prefeediug, feeding and postfeeding. Prefeeding saliva was secreted at a rate of 140 ml/h, this saliva showed a pH of 8.6, 121 mEq/l of HCO3−, 33.5 mEq/l of HPO4−, 164.8 mEq/l of Na+ and 13.7 mEq/l of K+. Postfeeding saliva had similar composition and flow. Feeding resulted in a significant increase in flow and HCO3− concentration. The pH obtained was somewhat raised by the loss of CO2.

Effects of glucagon on the splanchnic and the systemic circulation

1. 1. Dogs were treated with an intravenous injection of 2 mg of glucagon. Hepatic, celiac, and superior mesenteric arterial blood flows and concomitant cardiac output rates were measured. Local and total peripheral resistance was calculated. Heart rate, systemic arterial pressure, central venous pressure, and portal venous pressure were measured. Also, blood sugar, potassium, and blood gases were determined. 2. 2. Hepatic, celiac, and superior mesenteric arterial flows increased 41, 69 and 85 per cent, respectively, whereas concomitant cardiac output rates increased 36, 51 and 42 per cent, respectively. Local and total peripheral resistance significantly decreased. Heart rate increased and systemic arterial pressure declined. 3. 3. Although flows in the hepatic, celiac, and superior mesenteric beds were increased at a rate greater than that of cardiac output, the main effect of the hormone in increasing flow was secondary to its myocardial stimulatory effects. Only the superior mesenteric arterial bed had significant increase of flow out of proportion to the rise in cardiac output. 4. 4. Blood sugar increased sharply. The serum potassium showed an initial sharp rise after glucagon injection that was followed by a sharp fall which correlated with the appearance of hyperglycemia.

Changes in bile secretion produced by hippocampal and hypothalamic stimulation

The influence of conditioning electrical stimuli applied to the anterior hypothalamus or hippocampus on the effect exerted by the posterior hypothalamus on bile secretion was studied in anesthetized cats. Electrical stimulation of the posterior hypothalamus alone caused a significant increase in flow from the isolated common bile duct during 4 hours. A significant increase in average potassium concentration was found in bile samples collected during this period. Electrical stimuli applied to the anterior hypothalamus or dorsal hippocampus prior to the posterior hypothalamic stimulation.abolished the expected increase in bile flow and potassium concentration. The present experiments indicate that interactions within the hypothalamo-hippocampal system may affect the rate of bile secretion and its electrolyte composition. It seems that there exists a central nervous system regulation modifying potassium efflux.

The effect of slow wave sleep and REM sleep on regional cerebral blood flow in cats.

Abstract Regional cerebral blood flow was measured by means of an autoradiographic technique in unanaesthetized, unrestrained cats during wakefulness, slow wave sleep (S‐SW), and rapid eye movement sleep (S‐REM). The electrocorticogram, electro‐oculogram, and electromyogram from the posterior neck muscles were continuously recorded. All operative procedures were completed at least four days prior to the experiment. Arterial blood samples were obtained immediately prior to the regional cerebral blood flow determination and analysed for PCO2, PO2, pH, and haematocrit. There were no significant differences in these parameters among the three groups.During S‐REM there was a significant increase in flow in all twenty‐five regions measured which varied from 62 per cent in the cerebellar white matter and sensory‐motor cortex to 173 per cent in the cochlear nuclei. During S‐SW a significant increase in flow occurred in only ten of the twenty‐five regions, and these changes were smaller in magnitude, varying from 26 per cent in the association cortex to 68 per cent in the superior olive. It is postulated that local changes in cerebral metabolism account for the regional cerebral blood flow changes demonstrated.

Effects of alterations of total muscular blood flow on local tissue clearance of radio-iodide in the cat.

Abstract.Simultaneous measurement was made of isotope clearance and of venous outflow or arterial inflow in the gastrocnemius muscle of anesthetized cats. The purpose was to explore if vasomotor nerves to the skeletal muscles might innervate different types of blood vessels. Restriction of the arterial inflow resulted in approximately proportionate decreases in flow and clearance. Stimulation of the sympathetic supply to the area caused a somewhat greater decrease in total flow than in clearance. Intra‐arterial infusion of compound 48/80 or of methacholine, stimulation of the sciatic nerve or of the appropriate anterior roots, all increased flow and clearance proportionately. In contrast, stimulation of vasodilator pathway in the hypothalamus caused significant increase in flow with no consistent change in tissue clearance. With sympathetic stimulation, clearance of intra‐arterially injected isotope showed a drop more nearly proportional to the drop in blood flow. None of the vasodilating procedures, however, increased the rate of clearance of intra‐arterially administered isotope. It is concluded that most procedures influence the shunt and nutritional blood flow in a proportionate manner, but the active vasodilation resulting from hypothalamic stimulation is restricted to the shunt flow.

Effect of insulin on hepatic blood flow in the unanesthetized dog.

The immediate and direct effect of intravenously or intra-arterially administered insulin upon hepatic blood flow was studied in unanesthetized dogs whose hepatic vessels had been previously catheterized. Comparison was made between two dose levels, 0.1 or 0.2 u/kg and 1.0 u/kg, the latter being infused over a 30-minute period. At the 0.1 or 0.2 u/g range there was no immediate statistically significant flow increase. Sporadic flow increases occurred in about half the series during the recovery phase of the hypoglycemia (20–45 min. after insulin). At the 1.0 u/kg level insulin produced a definite increase in HBF which reached its maximum at 15 minutes. These flow changes were interpreted as secondary effects to the insulin induced hypoglycemia.

AN INQUIRY INTO THE STRUCTURAL CONDITIONS AFFECTING FLUID TRANSPORT IN THE INTERSTITIAL TISSUE OF THE SKIN

With the aim of determining the structural conditions which affect fluid movement in the cutaneous connective tissue of mice, various test fluids were brought into contact with it under conditions such that neither blood vessels nor lymphatics were directly entered. Locke's solution, mouse serum, and a mixture of Locke's solution with a dye which causes edema were all employed. At atmospheric pressure, Locke's solution entered the tissues intermittently. When subjected to very low pressures it continued to enter the skin intermittently and at approximately the same rate. At pressures above 4.5 cm. of water, however, the flow became continuous but it did not increase in rate significantly until pressures of about 8.5 cm. were employed. There was no relationship between the rate of flow and the pressure employed. At a pressure of about 8.5 cm. the resistance of the tissues seemed to give way abruptly as if the formed elements had been separated. This has been termed the "breaking point." After it had been reached each further increase of pressure produced a proportionately greater inflow. Under the conditions of our experiments, the dye-Locke"s solution and also the homologous serum failed to enter the tissues at atmospheric pressure. It was necessary to subject these fluids to pressure to force them into the skin at the same rate at which the Locke's solution entered it spontaneously. Under these circumstances the dye-Locke's solution and the serum entered the skin continuously, not intermittently like the plain Locke's solution. As the pressure was gradually raised, no significant increase of flow into the tissues occurred until a point was reached, on the average 8.5 cm. of water, at which fluid suddenly began to enter very rapidly. This point, the "breaking point" already mentioned, was reached at the same pressure irrespective of the character of the fluid employed, showing that the phenomenon was produced by the fluid bulk. Once it had been attained, further increases in pressure caused proportionately greater inflow of fluid. The circulation had nothing to do with the phenomenon, for it occurred in the skin of dead mice." The findings indicate that under normal circumstances the movement of fluid in the interstitial tissue does not take place as though in preexisting channels. The experiments confirm previous observations from this laboratory (13, 14) that in normal skin tissue the state of affairs is such that fluid cannot flow freely. However, when fluid is introduced into the skin under pressure spaces are forcibly opened up. Inflammatory edema in the skin changed the phenomena of fluid entrance into it under pressure. The reason is that there then occurred a separation of the formed elements and the interstitial fluid moved as in preformed channels. Even when very low pressures were employed (3.0 to 7.0 cm. of water), there appeared usually a linear relationship between the pressure and the rate of flow.