Changes In Intraluminal Pressure Research Articles

Effect of substance P on colonic mechanoreceptors, motility, and sympathetic neurons

Intracellular recording techniques were used in vitro to analyze the effects of substance P (SP) on synaptic transmission and electrical properties of sympathetic neurons in the inferior mesenteric ganglion (IMG) of the guinea pig. Intraluminal pressure-recording techniques were used to study the effects of SP on colonic motility. Superfusion of the ganglia with SP (10(-7) to 10(-6) M) depolarized the cell soma (2--12 mV) and increased cell input resistance (8--11 M omega). These effects converted synchronous excitatory postsynaptic potentials, in response to electrical stimulation of preganglionic nerves, and asynchronous excitatory postsynaptic potentials, in response to activation of colonic mechanoreceptors, to action potentials. Administration of SP to only the colon increased basal intraluminal pressure and the frequency and amplitude of phasic changes in intraluminal pressure. These changes increased mechanoreceptor synaptic input to neurons in the IMG. We conclude that SP facilitates synaptic transmission along noradrenergic pathways and increases colonic motility.

Etude in vitro de l'activité motrice des deux couches musculaires de l'oviducte chez la Lapine

Electrical and mechanical activities in the circular layer in the longitudinal peritoneal muscle were recorded in vitro in the oviducts of untreated and estrogen-treated ovariectomized rabbits. The duration and frequency of the bursts were not significantly changed in either muscle layer by the hormonal treatment. Estradiol increased the propagation of electrical activity in the isthmus and the amplitude of the contractions as well as the synchronization between the mechanical and electrical activities in the two muscle layers. Recordings of both electrical and mechanical activities were necessary to estimate the effects of the estrogen on the muscular layers. Removal of the longitudinal fiber bundles modifying the pattern of electrical and mechanical activities in the circular layer of the isthmus only increased the frequency of circular bursts and the frequency and amplitude of intraluminal pressure changes in both groups of animals. It is supposed that removal of the longitudinal fiber bundles could have damaged the inhibitory isthmic innervation of the circular layer. The EMG activity of the longitudinal layer was generally independent from that of the circular layer in the oviducts of estrogen-treated rabbits. In 24 p. 100 of records which showed a synchronization of the electrical and mechanical activities of both muscle layers in the isthmus, the times between the contractions of the two muscle layers varied from 0.1 to 3.2 sec, suggesting that they were mechanically coupled.

P-148 - Action of adenosine onperistalsis in guinea pig isolated ileum (2): The relation of adenosine related compounds to the intraluminal pressure changes

P-148 - Action of adenosine onperistalsis in guinea pig isolated ileum (2): The relation of adenosine related compounds to the intraluminal pressure changes

Cerebral autoregulation: an in vitro study.

Cerebral autoregulation can be duplicated in vitro using the large middle cerebral arteries from a calf. The limits of autoregulation were between 50 and 150 mm Hg. Excessively high pressures may lead to the appearance of the "sausage- or bead-string" response followed by forced dilation. These results suggest the existence of an intrinsic myogenic mechanism responsive to intraluminal pressure changes.

Effects of methionine-enkephalin on intestinal circulation and oxygen consumption.

AbstractThe effects of intra-arterial administration of Met-enkephalin upon intestinal blood flow, oxygen consumption, intestinal motor activity, and distribution of blood flow to the compartments of the gut wall were measured in anesthetized dogs before and after blockade of opiate receptors with naloxone. Blood flow to a segment of distal ileum was measured with an electromagnetic blood flow meter and intestinal oxygen extraction was measured spectrophotometrically. Oxygen uptake was calculated as the product of oxygen extraction and total blood flow. Changes in blood flow distribution were estimated from the distribution of radiolabeled microspheres. Motor activity was monitored from changes in intraluminal pressure. In dogs prior to blockade of opiate receptors, Met-enkephalin induced a dose-related increase in mesenteric blood flow, oxygen extraction and consumption, and intestinal motor activity. A significant increase in blood flow to the muscularis was also observed. The intestinal vasodilator, me...

Radiographic evaluation of spastic colon disease, diverticulosis, and diverticulitis

Spastic colon disease is a syndrome consisting of abdominal pain and abnormal bowel function associated with thickening of the circular muscle layer of the colon. The condition may be related to changes in intraluminal pressure associated with a lifelong low residue diet. Radiologic features include thickening, crowding, irregularity, and distortion of the interhaustral folds of the sigmoid colon, which in the past have been incorrectly considered to be manifestations of acute diverticulitis. Spastic colon disease leads to diverticulosis which develops because of mucosal herniations through the weakened colonic wall. When a diverticulum perforates, acute diverticulitis ensues. Depending on how the subsequent inflammatory response is contained, a mural abscess, colonic narrowing or obstruction, an intra-abdominal abscess, or a fistula may occur and be demonstrated on barium enema examination.

Intraoperative and postoperative esophageal manometric findings with Collis gastroplasty and Belsey hiatal hernia repair for gastroesophageal reflux

The combination of a Collis gastroplasty with a Belsey Mark IV fundoplication has proved clinically effective in the management of certain patients with complications of gastroesophageal reflux. The present study measured the effect of gastroplasty and Belsey repair on intraluminal pressure changes in the gastroplasty and lower esophagus. Manometric studies were performed preoperatively, intraoperatively, and postoperatively. In each case the gastroplasty segment of the esophagus was found to function as a high pressure zone (HPZ). The pressure in this zone further increased following the fundoplication. It could be diminished with intravenous administration of Buscopan and augmented with intravenously given pentagastrin. The original lower esophageal sphincter in most instances was included in the upper segment of the gastroplasty tube, but the entire length of the gastroplasty tube functioned as an HPZ, and pressures in the tube were considerably higher than those originally present in the lower esophageal sphincter. These studies provide a physiological rationale for the effectiveness of gastroplasty and fundoplication.

Effects of glucagon and secretin on food- or morphine-induced motor activity of the distal colon, rectum, and anal sphincter.

The effects of glucagon and secretin on food- or morphine-induced motor activity of the distal colon, rectum, and internal anal sphincter were investigated in 12 healthy subjects. Intraluminal pressure changes were measured using a triple-lumen polyvinyl tube assembly with 3 side orifices. Glucagon, administered intravenously, caused significant inhibition of food- or morphine-induced motor activity of both the distal colon and rectum. In contrast, secretin did not suppress morphine-induced motor activity but did significantly inhibit food-stimulated motor activity of the distal colon. The inhibitory effect of secretin on motor activity of the rectum was insignificant. Morphine, but not food, elevated the pressure of the anal sphincter which was not effected by glucagon or secretin. Hyperglycemia, produced by the infusion of 5% glucose, had no effect on motor activity. These studies demonstrate that glucagon but not secretin, in the doses employed, inhibits morphine-induced motor wave activity of both the distal colon and rectum and that this inhibitory effect is not secondary to hyperglycemia. Furthermore, the rise in anal sphincter pressure is not affected by glucagon or secretin.

Brain water alterations after unilateral nephrectomy. A study of regional circulatory factors in squirrel monkeys.

White and regional gray matter distributions of water, blood flow, and the protein tracer pertechnetate were measured in five normal squirrel monkeys. A second group of five monkeys, which had undergone unilateral nephrectomy six months previously, were found at the time of study to have blood pressures similar to those of the control animals but increased brain water and altered distribution of blood flow which was increased in white matter. No alteration of capillary permeability to the protein traces attended these changes, which appeared to be influenced by blood pressure. Nephrectomy without hypertension influences brain water content, perhaps because of an effect on cerebral resistance vessels. In hypertensive encephalopathy renal lesions, as well as intraluminal pressure changes, may be related to cerebral edema.

Thyrotropin-Releasing Hormone: Stimulation of Colonic Activity Following Intracerebroventricular Administration

Intraventricularly administered thyrotropin-releasing hormone in rabbits elicited an increase in intraluminal pressure changes, a response commonly associated with muscular activity of the colon. The response appears to be central in origin with peripheral expression relying primarily on cholinergic receptors.

Vagotomy impairs pentagastrin-induced relaxation of canine gastric fundus.

In eight dogs, a separated, vagally innervated pouch was made from the gastric fundus. Electrodes were implanted on the pouch, and an antral gastric fistula was created through which gastric juice was drained externally during all tests. After recovery, the fasted, conscious dogs received intravenous infusions of 154 mM NaCl to which randomly selected doses of pentagastrin were intermittently added while intraluminal pressure and electric activity of the distended pouch were recorded. Transthoracic vagotomy was then performed, and the dogs were restudied. Before vagotomy, pentagastrin decreased the amplitude of the phasic changes in intraluminal pressure and of the bursts of spiking potentials of the pouch. The D50 for inhibition of mean intrapouch pressure was 4.2 ng/kg per min. After vagotomy, pentagastrin still decreased intrapouch pressure and inhibited fundal spikes, but larger doses were required to produce equivalent decreases in pressure. The D50 was 41.4 ng/kg per min after vagotomy. Our conclusion is that pentagastrin-induced relaxation of the canine gastric fundus is impaired, but not abolished, by vagotomy.

Relationship between changes in intraluminal pressure and transmural potential difference in the human and canine jejunum in vivo.

Recordings of transmural potential difference (PD) across the jejunum of conscious man in situ are characterised by spontaneous fluctuations of up to 10 mV. In 25 of 31 subjects (comprising seven normal controls and 24 patients under investigation for malabsorption, six of whom had coeliac disease) we observed a clear association between these fluctuations and changes in intraluminal pressure recorded at the same site. The most frequent PD changes were associated with type III pressure waves. These consisted predominantly of large waver (3-1 +/- 0-1 mV; mean +/- SEM, n = 317) which reached maximal amplitude approximately 45 seconds after the pressure peak and had a duration of 120 +/- 3 s, but also included less frequent spikes (0-5 +/- 0-1 mV; n = 110) concurrent with the pressure wave with a duration of 5 +/- 1 s. Although by recording at two sites in the jejunum 10 cm apart we were able to demonstrate that type III pressure waves appeared to be propagated aborally at a median rate of 60 cm per minute, the apparent rates of propagation of the corresponding PD waves were much more variable. The largest PD changes (7-8 +/- 0-4 mV; n = 19), lasting several minutes, were found in association with runs of type I waves (basic rhythm) superimposed on a type III wave. Both pressure and PD activities were suppressed by intramuscular propantheline bromide. Intraluminal pilocarpine caused a transient rise in PD not always accompanied by a change in pressure. Distention of the jejunum by rapid injection of a bolus of isotonic sodium chloride produced a delayed rise in the PD which could be prevented by prior administration of propantheline bromide. Experiments using Thirty-Vella loops of proximal jejunum in conscious dogs confirmed the effect of jejunal distension on the PD and also demonstrated that spontaneous retching is preceded by an increase in the PD. Consideration of these results in conjunction with data from other workers suggests the hypothesis that the larger spontaneous fluctuations in transmural PD in the jejunum of conscious man are caused by changes in electrogenic secretion associated with intestinal motility and mediated by cholinergic mechanisms. The possible association of increased secretory activity with motility may have functions of lubrication as well as diluting and mixing the chyme for easier digestion and absorption.

Why Do Radial Artery Grafts for Aortocoronary Bypass Fail? A Reappraisal

The reasons for the high failure rate of radial artery grafts for aortocoronary bypass (ACB) are appraised. Each of 11 dogs received four types of grafts: femoral arteries were grafted to carotid arteries, and jugular veins were grafted to femoral arteries bilaterally. One of each pair of grafts was wrapped in a plastic sheet in order to interfere with the regeneration of vasa vasorum. The grafts were examined 2 months later. The results suggest that although operative trauma and intraluminal pressure change play important roles, the thick-walled artery appears to depend more on vasa vasorum for its integrity than does the thin-walled vein. A free radial artery graft, with vasa vasorum disrupted at both ends, cannot regenerate readily from the adjacent tissue, as is the case at the ACB position, and is therefore more vulnerable to subintimal hyperplasia and occlusion than either the vein graft or the internal mammary artery graft; both of these grafts are thinner, and the internal mammary artery graft remains undisrupted at one end.

Gallbladder pressure-volume response to gastrointestinal hormones

The pressure-volume (PV) response of the opossum gallbladder was studied under basal conditions and after the continuous intravenous infusion of gastrin I, secretin, and cholecystokinin (CCK). The hormone effects were examined individually and in combination. The unstimulated gallbladder was capable of accommodating increases in intraluminal volume with only slight changes in intraluminal pressure. Cholecystokinin significantly increased the pressure recorded from the gallbladder. The pressure generated depended on the concentration of CCK and the intraluminal volume. Gastrin I had no independent effect on the PV response of the gallbladder but reduced the stimulatory affect of CCK. Secretin, alone, decreased the PV response of the gallbladder. Secretin also antagonized the stimulatory response to CCK. These findings suggest that the regulation of gallbaldder motor function and pressure generation exclusive of neural input, may depend on the interaction of CCK with gastrin and secretin and the intraluminal volume of the organ at the time of stimulation.

Longitudinal tension of anterior tibial artery segments during constrictor responses.

Longitudinal tensions were recorded from in situ isolated segments of dog anterior tibial arteries during vasoconstrictor responses. Two factors appeared to be responsible for longitudinal tensions occurring during vasoconstrictor responses. One was due to changes in intraluminal pressure and appeared to be the dominant factor. Increases in intraluminal pressures produced decreases in longitudinal tensions, indicating that the vessel segments were elongated. Thus, increases in intraluminal pressure passively stretched the blood vessel walls so that increases in both the circumferential and longitudinal axes of the vessel segment occurred. These findings agree with similar findings reported earlier (4, 7, 8). The other factor was apparently due to changes in longitudinal tension produced by vascular smooth muscle contraction. In some cases longitudinal tension changes were positive, in others they were negative. Increases in longitudinal tension were probably the result of contractions of helical smooth muscle elements. Decreases in tension may have been due to displacement of tissue parallel to the long axis of the vessel as smooth muscle elements contracted.

A noncontact method for three-dimensional analysis of vascular elasticity in vivo and in vitro

A new method is described to measure the deformation of the blood vessel wall simultaneously in longitudinal and circumferential directions. This information is of paramount importance for further characterization of the elastic properties of the arterial wall. The new method consists of a closed-circuit TV system in conjunction with a video dimension analyzer (VDA). The VDA utilizes the video signal from the TV camera and forms a DC voltage proportional to the distance between two selected points in the scene. The resulting analog voltage, calibrated in dimensional units, is recorded. Dimensional changes in two directions, due to intraluminal pressure oscillations, are tracked continuously. The measurement can be performed in vivo on exposed vessels as well as in vitro on excised specimens. Distortion caused by the end effects is completely eliminated. For further data analysis, the wall thickness of the artery is determined microscopically. Stress and strain relationship in longitudinal and circumferential directions is calculated for every intraluminal pressure change. This approach yields data on mechanical properties of the vessel wall in a far more physiological way than the hitherto used direct-contact techniques.

The physiology and pathophysiology of the ureter.

A review is given of the theories concerning the transport of urine from the calyces to the bladder. The application of hydrodynamic laws on the propulsion of urine, the visco-elastic characteristics of the ureter wall, the myogenic versus the neurogenic origin of spontaneous activity of the ureter and the presence of pacemaker areas, are discussed. The changes of peristaltic activity and intraluminal pressure during obstruction, infection and reflux are summarized.

Gastroduodenal electrical activity in turkeys.

Bipolar Ag/AgCl electrodes were implanted in the stomach and duodenum of 21 turkeys to study electrical activity in those organs. Intraluminal pressure changes were also monitored. For comparative purposes, electric slow waves were recorded from the stomach of turkeys. Although slow waves were recorded from the duodenum of turkeys, the waves were observed to wax and wane and were possibly not the major regulators of duodenal contractile activity. Several bursts of action potentials and several contractions usually occurred in the duodenum during one slow-wave cycle. Duodenal motility appeared to be totally coordinated with the gastric cycle. Impulses conducted over intrinsic nerves from a gastric pacemaker (15) were proposed as a possible mechanism for initiating and coordinating gastroduodenal motor activity.

Role of luminal hydrostatic pressure in proximal tubular fluid reabsorption in the rat.

The effect of small changes in intraluminal hydrostatic pressure (P) on the tubular radius (r) and the net fluid reabsorption per unit of surface area of the tubular wall (Js) has been studied in the proximal tubule of the rat kidney. The split-drop method was used to simultaneously determine Js and r. Two standardized split-drop techniques A and B allow selective change in P. P was 31.6 +/- 1.3 mmHg in technique A and 15.5 +/- 1.5 in technique B. The pressure difference significantly affected the tubular radius; r was 21.9 +/- 0.4 and 18.6 +/- 0.5 mum in the split drop A and B, respectively. In contrast, net transepithelial fluid reabsorption Js was unchanged. Js amounted to 2.72 +/- 0.20, and 2.78 +/- 0.33 10(-5) cm3 cm-2 s-1 in split drop A and B. The absence of variations in Js could result from two opposite effects of pressure. P might enhance Js by increased ultrafiltration. However, the rise in r might decrease the density of the intraepithelial transport paths per unit area of tubular wall and therefore might decrease Js.

Potency and selectivity of methyl analogues of prostaglandin E2 on rat gastrointestinal function.

1 The potency and selectivity of action of prostaglandin E2 and its (15S)- or (15R)-15 methyl and 16, 16 dimethyl analogues on gastrointestinal function have been studied in the rat. 2 The (15S)-15 methyl and 16, 16 dimethyl analogues were 40 times as active as prostaglandin E2 in inhibiting pentagastrin-stimulated acid secretion on intravenous administration to the anaesthetized rat, and 100 times as active on subcutaneous injection to the chronic fistula rat. 3 In antisecretory doses, the analogues, like prostaglandin E2, caused bile reflux and, in higher doses, profuse diarrhoea. 4 The (15S)-15 methyl and 16, 16 dimethyl analogues were at least 30 times as active as prostaglandin E2 in causing changes in intestinal intraluminal pressure in vivo, but were equipotent on isolated smooth muscle. 5 In equivalent antisecretory doses, the methyl analogues had little effect on systemic arterial blood pressure and resting mucosal blood flow compared with prostaglandin E2. 6 The (15R) methyl epimer administered parenterally had little effect on gastrointestinal function but brief acid incubation greatly increased its activity.