Mediators and enteric nerve pathways controlling gastric emptying.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
G Tougas
Publications and source records attributed to G Tougas.
Reliability and interobserver variability of ultrasonographic measurement of gastric emptying rate.
Scintigraphy and real-time ultrasound are valid techniques to measure parameters of gastric emptying. However, scintigraphy involves exposure to ionizing radiation, while the precision of real-time ultrasound has not been previously evaluated. The objectives of the present study were to determine the inter observer and day-to-day variability of liquid gastric emptying rate measured by real-time ultrasonography in healthy volunteers and to compare the gastric emptying rate of males and females. Twenty healthy volunteers had ultrasonographic measurement of gastric emptying rate after ingestion of 300 ml beef broth. Nine subjects had a concurrent assessment by a second observer. Nine subjects had two studies performed on different days by the same sonographer. The T1/2 for 20 subjects was 24.77 +/- 6.84 min with no difference between the half-emptying time for males (25.89 +/- 6.99 min) and females (24.02 +/- 6.94 min). The Pearson and intraclass correlation coefficients for observations made by two observers were 0.83 and 0.625, with a difference due to observer of 2.37 min +/- 5.26 (NS). The test-retest reliability across successive days was 0.136, representing considerable day-to-day variability within subjects. The variability between subjects was also large, explaining up to 79% of the total variance. We conclude that ultrasound is a useful method to evaluate gastric emptying with good interobserver agreement. Due to substantial day-to-day variability, sample sizes larger than previously suggested are required to demonstrate clinically important changes in gastric emptying rate in clinical trials.
Adult↗
Norepinephrine release in rat vas deferens. Effect of rauwolscine and BHT 920.
Norepinephrine (NE) overflow from field-stimulated rat was deferens preparations was quantified directly by electrochemical detection using high performance liquid chromatography. The effect of agonist (BHT 920) and antagonist (rauwolscine) of prejunctional alpha 2-adrenoceptors on NE overflow was assessed and compared with their effect on the smooth muscle mechanical response to field stimulation. Increasing the stimulation frequency from 2 to 30 Hz resulted in an increase in muscle tension together with an increase in NE overflow. Addition of 1 microM rauwolscine to the medium resulted in a significant increase in muscle contraction to field stimulation which reached a maximum at 5 Hz. On the other hand, NE overflow increased linearly with the frequency of stimulation within the range studied. Addition of 0.1 microM BHT 920 to the medium significantly decreased the amplitude of contractions at lower stimulation frequencies (2 to 10 Hz) but elicited no significant changes at high frequencies. BHT 920 did not significantly affect NE overflow for all range of stimulation frequency. The simultaneous recording of field-stimulation induced contractions and NE overflow indicates that in the rat vas deferens, rauwolscine acts like a pure alpha 2 adrenoceptor antagonist at a prejunctional level. BHT 920 did not appear to affect selectively prejunctional alpha 2 adrenoceptors but also may activate postjunctional alpha 1 adrenoceptors.
Adrenergic alpha-Agonists↗
Cerebral-evoked potential responses following direct vagal and esophageal electrical stimulation in humans.
Cerebral evoked responses following direct electrical stimulation of the vagus and esophagus were compared in 8 epileptic subjects and with those recorded after esophageal stimulation in 12 healthy nonepileptic controls. Direct vagal stimulation was performed using a left cervical vagal pacemaker, which is used in the treatment of epilepsy. Esophageal stimulation was obtained with the use of an esophageal assembly incorporating two electrodes positioned 5 and 20 cm orad to the lower esophageal sphincter. Evoked potential responses were recorded with the use of 20 scalp electrodes. The evoked potential responses consisted of three distinct negative peaks and were similar with the use of either vagal or esophageal stimulation. The measured conduction velocity of the afferent response was 7.5 m/s in epileptic subjects and 10 m/s in healthy controls, suggesting that afferent conduction is through A delta-fibers rather than slower C afferent fibers. We conclude that the cortical-evoked potential responses following esophageal electrical stimulation are comparable to direct electrical stimulation of the vagus nerve and involve mostly A delta-fibers. This approach provides a method for the assessment of vagal afferent gastrointestinal sensory pathways in health and disease.
Adult↗
Effect of acupuncture on gastric acid secretion in healthy male volunteers.
Six randomized, placebo controlled studies were performed to investigate the effect of electroacupuncture on gastric acid output in 38 healthy males. Electroacupuncture decreased basal acid output when compared to placebo acupuncture [from 3.50 +/- 0.59 mmol/hr to 2.54 +/- 0.56 mmol/hr (P < 0.05)] as well as sham feeding-stimulated acid output [from 18.52 +/- 2.25 mmol/hr to 5.38 +/- 2.11 mmol/hr (P < 0.005)], but had no effect on the pentagastrin stimulated acid output. The inhibitory effect of acupuncture on sham feeding-stimulated acid output was not affected by local anesthesia of the acupoint, but was prevented by a prior intravenous naloxone injection. Acupuncture did not alter plasma gastrin levels (20.7 +/- 7.6 micrograms/liter, vs control 21.2 +/- 7.2 micrograms/liter) but naloxone increased it (26.1 +/- 14.5 micrograms/liter) (P < 0.05). We conclude that the antisecretory effects of electroacupuncture do not result from decreased gastrin release or decreased parietal cell sensitivity to gastrin, but are mediated through naloxone-sensitive opioid neural pathways and vagal efferent pathways.
Acupuncture Points↗
Effects of chronic left vagal stimulation on visceral vagal function in man.
We examined the effects of chronic left vagal electrostimulation on afferent and efferent gastrointestinal vagal function in eight patients. Afferent function was assessed using cortical evoked responses to electrical stimulation of the esophagus and to direct vagal stimulation using the implanted left vagal electrode. Efferent gastrointestinal vagal function was measured by examining the basal, maximal, and sham fed stimulated gastric acid output prior to and with chronic left vagal electrostimulation. Esophageal electrostimulation produced a cortical evoked response consisting of three negative and three positive peaks within 400 msec after stimulation. Prior to vagal electrostimulation the mean conduction velocity of the afferent signal was measured at 8.72 +/- 3.39 m/sec, compatible with A-delta fibers involvement. Basal, maximal, and sham fed acid output were 1.11, 21.87, and 9.37 mmol/hour, respectively. The evoked response to esophageal electrical stimulation was not changed with chronic left vagal electrostimulation. Direct vagal stimulation also produced evoked potentials that were comparable to those obtained with esophageal stimulation. The mean conduction velocity was 6.26 +/- 2.72 m/sec (NS) so that there was no evidence of loss of myelinated fibers with chronic stimulation. No differences were detected in basal (1.29 mmol/h), maximal (21.64 mmol/h), or sham fed stimulated (8.03 mmol/h) acid output, showing that vagal electrostimulation has no effect on either total or vagally mediated acid output, an efferent vagal function. In conclusion, chronic left vagal electrostimulation has no significant adverse effect on gastrointestinal vagal function.
Adult↗
Evidence of impaired afferent vagal function in patients with diabetes gastroparesis.
Two patients, a 28-year-old male and a 70-year-old female, with chronic insulin dependent diabetes mellitus and evidence of autonomic neuropathy were studied using cortical evoked responses following esophageal balloon and electrical stimulation. Both patients had symptomatic gastroparesis, poor gastric emptying, and reduced gastroduodenal motility including abnormal results of scintigraphy and manometry. There was slowing of afferent vagal conduction but good evoked potential responses were recorded even though one patient could not feel electrical stimulation of either the proximal or distal esophagus. It is improbable that the gastric symptoms are due to an afferent autonomic neuropathy, but symptoms may well be related to impairment of motor vagal pathways. Nevertheless, afferent vagal pathways are involved in severe diabetes mellitus. The clinical significance of this delay in conduction velocity of afferent pathways remains to be established.
Adult↗
Relation of pyloric motility to pyloric opening and closure in healthy subjects.
The relation between pyloric motor activity, opening, and closure was examined in eight healthy men. Manometry was performed with an assembly combining 13 side holes and a sleeve sensor positioned astride the pylorus. Simultaneous with manometry, pyloric opening and closure and antroduodenal contractions were observed fluoroscopically with the antrum filled with barium. During intraduodenal normal saline infusion, coordinated antral pressure waves swept over the pylorus and ejected barium into the duodenum. No localised pyloric motor pattern was observed under these conditions. In contrast, the intraduodenal triglyceride infusion was associated with the absence of antral pressure waves and virtual absence of antral wall movement. At the pylorus, there was a zone of luminal occlusion less than 1 cm long that persisted for the period of observation. This zone of luminal occlusion corresponded precisely with manometric recordings of a narrow zone of pyloric phasic and tonic activity. During the duodenal triglyceride infusion, the pylorus was closed for 98.5% of the measurement period when basal pyloric pressure was 4 mm Hg or more, and during this motor pattern, barium did not traverse the pylorus. Localised pyloric contractions cause sustained pyloric closure, whether these contractions are phasic or tonic. These contractions occur independently of antral or duodenal contractions and may interrupt gastric emptying.
Adult↗
Nitric oxide as a putative nonadrenergic noncholinergic inhibitory transmitter in the canine pylorus in vivo.
Antropyloroduodenal motility was recorded in seven anesthetized dogs to assess the role of nitric oxide and L-arginine metabolites in nonadrenergic noncholinergic (NANC) mediation of pyloric relaxation. Pyloric activity induced by duodenal field stimulation was inhibited by antral field stimulation and electrical vagal stimulation. Intra-arterial NG-L-arginine-methyl-ester (L-NAME) reduced the inhibition from antral or vagal stimulation (P less than 0.05). Intravenous infusion of L-NAME also blocked the inhibitory effect of vagal and antral stimulation but left the tetrodotoxin-insensitive action of intra-arterial vasoactive intestinal peptide (VIP) and sodium nitroprusside unchanged. L-Arginine reversed the effect of L-NAME whereas D-arginine did not. L-NAME enhanced pyloric contractions to intra-arterial acetylcholine. The NANC inhibition of the substance P-stimulated pyloric response in vitro was blocked by L-NAME and reversed by addition of L-arginine. Sodium nitroprusside was effective as a relaxant in vitro but VIP was not. These data suggest that metabolites of L-arginine mediate neural inhibition of canine pyloric motor activity.
Animals↗
The effect of acupuncture on gastrointestinal function and disorders.
Acupuncture has been used empirically in clinical practice in China for several millenia and has recently drawn interest as a mode of anesthesia. Despite extensive investigation, the exact mechanisms of its analgesic action are unknown, but are thought to involve endogenous opioid peptides. Only recently have studies attempted to evaluate the effect of acupuncture on gastrointestinal function and disease. A review of studies from both the Chinese and Western literature supports the efficacy of acupuncture in the regulation of gastrointestinal motor activity and secretion through opioid and other neural pathways. However, no firm conclusion can be drawn about the effectiveness of acupuncture in the treatment of specific gastrointestinal disorders because of the lack of properly randomized controlled trials.
Acupuncture Points↗
Sensory nerves of the intestines: role in control of pyloric region of dogs.
The canine pylorus is the target for a large array of extrinsic and intrinsic nerve-produced effects. Some of them have intermediate nicotinic synapses. In all cases observed so far the final nerve terminals mediating excitation are cholinergic, but those mediating inhibition are both adrenergic and non-adrenergic non-cholinergic. The role of the dense peptidergic innervation is unclear especially in view of the observation that this muscle and its nerves contain receptors to all of those studied (VIP, PHI, GAL, SP, NKA, NKB, CCK, and others. The pylorus is also the target of an important reflex initiated by acid in the duodenal lumen. Our preliminary work suggests that this reflex is initiated by acid induced release of 5HT from the EC cells to act on 5HT receptors on sensory nerves which activate the ascending chain of cholinergic nerves in the myenteric plexus. This same stimulus may also activate other vagal sensory nerves.
Animals↗
Neurophysiological effects of left vagal stimulation in man.
Explore the source record for details and available documents.
Adult↗
Distribution of vasoactive intestinal polypeptide (VIP) binding in circular muscle and characterization of VIP binding in canine small intestinal mucosa.
The present study examined the localization and characterization of [125I]vasoactive intestinal polypeptide (VIP) binding to synaptosomes and enterocyte membranes using preparations made from homogenized canine intestinal mucosa and compared it to [3H]saxitoxin binding and VIP-immunoreactive content (markers for synaptosomes). The highest [125I]VIP binding was located in the P2 fraction and was correlated with the locations of maximal [3H]saxitoxin binding and VIP-immunoreactive content. This correlation indicates that VIP receptors are present on synaptosomes of canine small intestinal mucosa. A fraction enriched in synaptosomes contained a high density of saturable VIP receptors (352 +/- 26.40 fmol/mg) having high affinity (Kd, 0.23 nM) for [125I]VIP. Studies of association and dissociation of [125I]VIP to this site revealed that binding was fully reversible and yielded a Kd value similar to that from equilibrium binding. Competition binding experiments suggested the presence of two binding sites, a high and a low affinity binding site. The order of competition potency was VIP greater than peptide histidine isoleucine greater than secretin greater than peptide histidine methionine greater than or equal to [D-Ala4]VIP greater than or equal to [Phe1]VIP greater than VIP10-28 greater than [4-Cl-D-Phe6-Leu17]VIP. All these competitors displaced all specifically bound VIP. VIP, peptide histidine isoleucine and secretin interacted differentially with each of the two binding sites. Peptide histidine methionine, [D-Ala4]VIP, [Phe1]VIP, VIP10-28 and [4-Cl-D-Phe6-Leu17]VIP interacted with a single low affinity at all binding sites. Other VIP binding sites were sought in circular muscle and submucosa.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The effect of naloxone on lipid-induced pyloric motor response in humans.
This study examines whether opioid receptors are involved in the mediation of the pyloric motor response to intraduodenal lipid infusion. Antral, pyloric, and duodenal manometry was performed in seven healthy volunteers with a sleeve/multiple side-hole manometric assembly. Triglyceride emulsion and normal saline were infused alternately into the duodenum through the manometric assembly for two 30-minute periods each. Naloxone was then administered as an IV bolus, 40 micrograms/kg, followed by an infusion of 60 micrograms.kg-1.h-1 that was continued during testing of the duodenal infusates. Before naloxone administration, intraduodenal lipid produced significant increases in the rate of isolated pyloric pressure waves and basal pyloric tone when compared with saline (P = 0.009 and 0.027, respectively). The pyloric motor responses were unchanged after administration of naloxone, indicating that in humans, naloxone-sensitive opioid mechanisms are not involved in the mediation of lipid-induced pyloric motor responses.
Adult↗
Seat features recommendations for workstations.
This paper makes general recommendations for workstation design. To prevent back problems, a chair should maintain a 105 degrees angle between the trunk and the thighs. For bent-forward work, a seat pan that can tilt forward allows the critical angle to be maintained.
Journal Article↗
Work organization and low back pain in nursing personnel.
Explore the source record for details and available documents.
Adult↗
Interaction of 70 S ribosomes from Escherichia coli with spin-labeled N-Cbz-Phe-tRNAPhe. An electron paramagnetic resonance study.
Two selectively spin-labeled Cbz-Phe-tRNAsPhe, one at position s4U8 and the other at position U33, have been used to study the dynamics of tRNA-ribosome interaction in the presence of poly(U) and factors washable from ribosomes. Upon binding to the ribosome, the correlation time of the spin label at position s4U8 decreases markedly while the same parameter for the label in the anticodon increases. The presence of poly(U) is not a prerequisite condition for the EPR spectral changes observed but larger variation occurs in the presence of factors washable from ribosomes. No variation in the correlation time is observed if uncharged spin-labeled tRNAPhe (on the s4U8 residue) is used in these experiments. Most of the ribosome-bound spin-labeled Cbz-Phe-tRNAPhe are puromycin-reactive, and consequently, the observed effect is manifested mainly at the ribosomal P site. These observations seem to suggest that the interaction between the N-blocked aminoacyl residue on the tRNA and the ribosome results in a conformational change on the tRNA, possibly involving tertiary interactions in a region close to s4U8. The role that the amino acid at the 3'-end can possibly play on this structural change is discussed.
Electron Spin Resonance Spectroscopy↗
The actions of neurokinins and substance P in canine pylorus, antrum and duodenum.
Analogues highly selective for receptors for substance P [beta-Ala4,Sar9,Met(02)11]-SP(4-11), for neurokinin A, [Nle10]-NKA(4-10), and for neurokinin B, [beta-Asp4,MePhe7]-NKB(4-10), were administered intraarterially before and after atropine or tetrodotoxin, to characterize the locations on nerve and muscle of the different receptor subtypes in the canine antrum, pylorus and duodenum. Circular muscle strips from each region were also studied in vitro. The NK-2 receptors in the antrum and the pylorus were located postsynaptically on smooth muscle. The NK-3 receptors, on the other hand, were located on neuronal sites in the antrum and duodenum. NK-1 receptors were located on neuronal and nonneuronal sites in the antrum, pylorus and duodenum. Only nonneural receptors could be activated in vitro.
Animals↗