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Biomedical subjects

J Dent

Publications and source records attributed to J Dent.

At least 181 records · Page 10Linked to original sources
PubMed1992

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↗
PubMed1992

Duodenal intramural nerves in control of pyloric motility and gastric emptying.

We have investigated the role of ascending duodenal intramural nerves in the control of isolated pyloric pressure waves (IPPW) and liquid gastric emptying. In six pigs, the proximal duodenum was transected to interrupt intramural nerves. A further six pigs had a sham operation. Four weeks after operation, motility of the antrum, pylorus, and duodenum was recorded by side holes and a sleeve sensor. Gastric emptying of a 1,000-ml test meal was significantly more rapid in duodenum-transected animals (P less than 0.0001) during intraduodenal infusion of each of isosmolar dextrose (424 ml emptied), fatty acid (335 ml), and amino acids (396 ml) than in duodenum-intact animals (dextrose: 128 ml; fatty acid: 57 ml; amino acids: 192 ml). Associated with this, in duodenum-transected animals infusion of each of isosmolar dextrose, fatty acid, amino acids, and hyperosmolar saline failed to produce the stimulation of IPPW seen in duodenum-intact animals. In both duodenum-intact and -transected animals, supramaximal stimulation by intraduodenal infusion of 25% dextrose slowed gastric emptying and stimulated IPPW. Ascending duodenal intramural nerves are a major physiological pathway for nutrient- and osmolar-stimulated feedback control of pyloric motility and gastric emptying.

Animals↗
PubMed1992

Changes in antroduodenal resistance induced by Cisapride in conscious dogs.

The effects of Cisapride on gastric outflow/pressure relationships have been examined in conscious dogs. In the digestive state, after inhibition of emptying in the first 10 min, Cisapride accelerated gastric emptying for 110 min by increasing the volume (7.3 +/- 1.2 vs. 2.3 +/- 0.3 ml) rather than by decreasing the interval between flow pulses (4.9 +/- 0.2 vs. 4.5 +/- 0.1s). After non-nutrient gastric loading, Cisapride also first inhibited and then accelerated gastric emptying as the consequence of both a larger stroke volume (8.0 +/- 1.7 vs. 3.2 +/- 0.5 ml) and more frequent pulses (3.9 +/- 0.1 vs. 4.9 +/- 0.1 s). In both situations, Cisapride increased the amplitude of the antral/pyloric pressure waves. Antropyloroduodenal resistance increased substantially in the first 10 min after Cisapride then recovered to its control value. We conclude that stimulation of antropyloroduodenal motility by Cisapride can both impede and increase gastric emptying by changes in antroduodenal resistance.

Animals↗
PubMed1992

Diaphragmatic contribution to gastroesophageal competence and reflux in dogs.

Events associated with gastroesophageal reflux have been determined by concurrent diaphragmatic and esophageal body electromyography, video radiography, and manometry in four conscious dogs. Three characteristic phenomena occurred in parallel immediately before and during gastroesophageal reflux: 1) transient lower esophageal sphincter relaxation, 2) profound (99.5%) and selective inhibition of crural diaphragmatic activity, and 3) a previously unrecognized dorsal movement of the gastroesophageal junction (mean 1.3 cm) demonstrated by implanted radiological markers. The patterns associated with spontaneous acid and gas reflux were indistinguishable from those induced by gastric distension. Costolumbar diaphragmatic activity was stable up until the instant of sphincter opening, when there was a single costolumbar contraction of short duration and high amplitude. Esophageal shortening did not occur before reflux. Reflux that occurred after atropine-induced inhibition of lower esophageal sphincter tone to < 2 mmHg was intermittent and coincided with selective crural inhibition. These studies demonstrated that selective crural inhibition is a prerequisite for gastroesophageal reflux and suggest that the crural diaphragm is an important factor for the maintenance of gastroesophageal competence.

Animals↗
PubMed1992

Long-term aims of treatment of reflux disease, and the role of non-drug measures.

Recent opinion about the long-term aims of treatment of reflux disease has been influenced substantially by the development of highly effective drugs that have minimal side-effects. The success of these drugs has emphasized the importance of gains in lifestyle resulting from relief of heartburn and other reflux-induced symptoms. Such relief is seldom achieved by traditional non-drug measures, which can also significantly impair lifestyle. In many patients with reflux disease, the effective relief of symptoms is a major aim. Oesophagitis, particularly when severe, carries a risk of developing peptic stricture or Barrett's oesophagus, but the risk factors associated with the development of these significant complications are not well identified. There is also no direct evidence that successful healing of oesophagitis by drug therapy is associated with prevention of local complications of oesophagitis, although many anecdotes regarding the resolution of peptic stricture by successful anti-reflux surgery support this possibility. Similarly, the linkage between development of Barrett's oesophagus and severe oesophagitis suggests that in some patients maintained healing of oesophagitis will prevent development or progression of Barrett's oesophagus. These considerations support the aim of healing of severe oesophagitis (i.e. more than patchy erosions), quite independently of the need to achieve effective symptom relief.

Beds↗
PubMed1992

On-line intraoperative quantitation of regional myocardial perfusion during coronary artery bypass graft operations with myocardial contrast two-dimensional echocardiography.

We hypothesized that the success of coronary artery bypass graft operations could be assessed by means of on-line quantitative myocardial contrast echocardiography. Accordingly, myocardial contrast echocardiography was performed at baseline and after each placement of venous graft in 21 patients undergoing coronary artery bypass graft operations. Time-intensity plots were generated on-line with the use of a dedicated computer system, and areas under the curve were assessed for each injection. Successful on-line quantitation of myocardial contrast echocardiography data was performed in 17 patients; this allowed comparison before and after coronary artery bypass graft operations for 21 grafts, with agreement between expert visual analysis and quantitative data in 91% of these cases. Three distinct perfusion patterns were noted on myocardial contrast echocardiography: (1) reduced contrast effect before coronary artery bypass graft operations with improvement after coronary artery bypass graft operations (n = 11); (2) adequate contrast effect before coronary artery bypass graft operations with no change after coronary artery bypass graft operations (n = 9) (for patients in group 2, the mean percentage of coronary stenosis was less than the mean for patients in group 1-67% +/- 25% vs. 88% +/- 20%, p = 0.05); and (3) no contrast effect either before or after coronary artery bypass graft operations in one patient with previous infarction. One third of the time (34 of 95 injections), on-line quantitation was unsuccessful. Failure was related three times more often to problems associated with myocardial contrast echocardiography, such as attenuation and inadequate quality of bubbles, than to computer failure. Despite its limitations, on-line quantitative myocardial contrast echocardiography is feasible in patients undergoing coronary artery bypass graft operations and provides important objective information regarding the success of revascularization.

Aged↗
PubMed1991

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↗
PubMed1991

Twitch potentiation during fatiguing exercise in the elderly: the effects of training.

Twitch potentiation was studied during a fatigue paradigm involving intermittent maximum voluntary contractions (MVCs) of the tibialis anterior muscle in the elderly and in young adults. Resting twitch torques were similar between groups, but twitch potentiation was significantly greater (241% vs 166%) in the young; the recovery of the twitch after fatigue was similar between groups. Contraction time, time to peak torque and half-relaxation time were all significantly slower in the elderly. Following 12 weeks of resistance training in the elderly, there was no significant change in the twitch contractile properties at rest, but there was a significant main effect of training on the degree of twitch potentiation during the same fatigue protocol (peak potentiation 192% post-training vs 165% pretraining). These data suggest that the mechanism(s) responsible for twitch potentiation following MVCs may be influenced by both aging and training.

Aged↗
PubMed1991

Provocation of transient lower esophageal sphincter relaxations by meals in patients with symptomatic gastroesophageal reflux.

The effect of a meal on the rate of transient lower esophageal sphincter (LES) relaxations and patterns of gastroesophageal reflux was investigated in 49 patients referred for evaluation of gastroesophageal reflux. Esophageal motility and pH were recorded concurrently before and after a standard meal. In the patients with symptomatic reflux, the meal induced a four- to sevenfold increase in the gastroesophageal reflux through two mechanisms: a four- to fivefold increase in the rate of transient LES relaxations and an increase in the proportion of transient LES relaxations accompanied by reflux from 47% to 68%. Overall the rate of reflux episodes that occurred by mechanisms other than transient LES relaxation did not increase significantly. An exception to these findings were those in six patients with chronically absent basal LES pressure in whom transient LES relaxations could not be scored. In these patients, reflux increased postprandially through mechanisms other than transient LES relaxation. These findings confirm the pivotal importance of transient LES relaxations in the pathogenesis of gastroesophageal reflux.

Esophagogastric Junction↗
PubMed1991

A prospective genetic study of complete and partial hydatidiform moles.

Two hundred two hydatidiform moles were classified by pathologic features and ploidy into partial or complete moles. Further classification was made by using genetic polymorphism, the diagnosis being refined by deoxyribonucleic acid technology. Among 51 partial hydatidiform moles, 44 triploids, two tetraploids, and one diploid were identified. Informative triploid partial hydatidiform moles had one maternal and two paternal sets of chromosomes, the likely origin being dispermy. Among 149 complete hydatidiform moles, one was haploid, one was triploid, and 105 were shown to be diploid or androgenetic; 39 of these were proved homozygous, indicating duplication of the male genome, whereas heterozygous origin by dispermy was likely in 13. The locus-specific minisatellite deoxyribonucleic acid probes were particularly useful for the identification of heterozygous complete hydatidiform moles. None of the patients with partial hydatidiform moles had development of a gestational trophoblastic tumor. No difference was detected in the frequency of requirement for chemotherapy between patients with homozygous or heterozygous complete hydatidiform moles.

Blotting, Southern↗
PubMed1991

Human anal motility while fasting, after feeding, and during sleep.

The aim of this study was to determine whether the human anal sphincter responds dynamically to changing physiological states. In 19 healthy human subjects, intraluminal anal canal pressure was measured with a 5-cm perfused sleeve sensor during the day while fasting (3 hours) and after feeding (3 hours) and at night during sleep (8 hours). Daytime mean anal canal pressures (+/- SEM) while fasting (50 +/- 3 mm Hg) were similar to those after feeding (49 +/- 3 mm Hg) and to those at night during sleep (49 +/- 3 mm Hg). Marked minute-to-minute variations in mean pressure occurred in all three periods, however, as did large phasic increases and decreases in pressure (greater than 20 mm Hg) and small phasic changes in pressure less than 20 mm Hg (anal slow waves). The minute-to-minute variations in mean pressure were greater during the awake fed state (4 +/- 1 mm Hg/min) than at night during sleep (2 +/- 1 mm Hg/min; P less than 0.03), as were the number of large phasic waves per minute (increases in pressure: awake, fed = 0.5 +/- 1 waves/min, night = 0.3 +/- 0.1 waves/min, P less than 0.05; decreases in pressure: awake, fed = 0.4 +/- 0.1 waves/min, night = 0.2 +/- 0.1 waves/min, P less than 0.05). Anal small waves had a similar frequency of about 17 waves/min in all three states. In conclusion, the anal sphincter maintains a continuous pressure barrier to rectal outflow both during the day and at night during sleep. However, marked minute-to-minute variations in mean pressure and large phasic increases and decreases in pressure do occur. Both are fewer at night during sleep.

Adult↗
PubMed1991

Effect of insulin-induced hypoglycaemia on antral, pyloric and duodenal motility in fasting subjects.

1. Hyperglycaemia alters gastric motility and delays gastric emptying. By contrast, there is little information regarding the effect of sub-normal blood glucose concentrations on gastric and, in particular, pyloric motility, although limited data suggest that hypoglycaemia is associated with accelerated gastric emptying despite an apparently increased basal pyloric pressure. 2. To determine the effects of hypoglycaemia on pyloric motility, we compared the effects of an intravenous injection of insulin (0.15 units/kg) with those of a placebo injection of saline in eight healthy human volunteers during phase I of the interdigestive migrating motor complex. 3. All subjects developed profound hypoglycaemia (mean blood glucose concentration 1.6 mmol/l compared with 4.0 mmol/l in the control group). 4. There was no significant difference in the number of antral (9 versus 7, P = 0.34), pyloric (3 versus 0, P = 0.31) or duodenal (21 versus 13, P = 0.42) pressure waves or in the basal pyloric pressure (0.3 mmHg versus 0.1 mmHg, P = 0.37) in the 45 min after insulin injection (hypoglycaemia) when compared with the 45 min after saline injection (euglycaemia). In both the euglycaemic and hypoglycaemic studies there was a time-dependent increase in the numbers of antral and duodenal waves consistent with the expected changes in the interdigestive migrating motor complex. 5. These results indicate that insulin-induced hypoglycaemia has no significant effect on pyloric motility during phase I of the interdigestive migrating motor complex.

Adolescent↗
PubMed1991

Hyperglycaemia stimulates pyloric motility in normal subjects.

The motor correlates of the delay in gastric emptying produced by hyperglycaemia were investigated in 11 healthy volunteers. Fasting gastroduodenal motility was measured during euglycaemia (blood glucose concentration 3-5 mmol/l) and during hyperglycaemia induced by intravenous dextrose (blood glucose concentration 12-16 mmol/l). Antral, pyloric, and proximal duodenal pressures were recorded by a sleeve/sidehole manometric assembly positioned across the pylorus, with the aid of measurements of transmucosal potential difference. During hyperglycaemia there was stimulation of isolated pyloric pressure waves when compared with the euglycaemia period (p less than 0.05). This was associated with inhibition of antral pressure waves (p less than 0.05). In nine of the 11 subjects an episode of duodenal 'phase III like' activity occurred within 15 minutes of the onset of hyperglycaemia. It is proposed that the stimulation of localised pyloric contractions and inhibition of antral contractions contribute to the delayed gastric emptying induced by hyperglycaemia. Abnormal gastric motility in patients with diabetes mellitus may be the result of hyperglycaemia itself, rather than irreversible autonomic neuropathy.

Adolescent↗
PubMed1991

Monitoring of upper oesophageal sphincter pressure in children.

In children technical limitations of upper oesophageal sphincter manometry have restricted investigation to the pull through technique under sedation. In this study we have used an adapted sleeve manometric technique for upper oesophageal sphincter monitoring in unsedated children and determined the influence of the state of arousal on upper oesophageal sphincter pressure. Twenty six children aged 3 to 42 months (median 17.5 months), who were referred for evaluation of oesophageal motor function, were studied with dual sleeve manometric assemblies which monitored upper and lower oesophageal sphincter pressures simultaneously. Pharyngeal, oesophageal body, and gastric pressures were also monitored with seven perfused side holes. Recordings were made for four hours after a meal and were technically successful in 24 children. The child's state of arousal was scored every 12th minute as follows: (A) resting, eyes closed, (B) resting, eyes open, (C) moving but comfortable, (D) restless and uncomfortable, (E) crying. In 67% of the 12 minute samples the children showed good adaptation to the procedure (arousal states A to C). There was a highly significant difference in upper oesophageal sphincter pressure between each of the arousal states (p less than 0.0001), being lowest in category A at (mean (SD) 18.1 (10.3) mmHg and highest in category D 55.7 (13.2) mm Hg. Abrupt changes in the state of arousal were associated with equally abrupt changes in upper oesophageal sphincter pressure. The state of arousal of unsedated children has an important influence on upper oesophageal sphincter pressure. It is essential that this factor is controlled for in any studies of upper oesophageal sphincter tone in children. The sleeve technique is capable of monitoring upper oesophageal sphincter motility for prolonged periods in unsedated children.

Arousal↗
PubMed1991

Role of the proximal and distal stomach in mixed solid and liquid meal emptying.

The role of the proximal and distal stomach in the emptying of solids and liquids from the stomach remains unclear. We have used a dual isotope technique to quantify proximal and distal stomach emptying of a solid (100 g of 99mTc labelled liver/ground beef) liquid (either 200 ml of normal saline (eight subjects) or 25% dextrose (seven subjects) labelled with 113mIn-diethylenetriaminepenta-acetic acid) mixed meal. A manometric catheter simultaneously measured antral, pyloric, and duodenal motor activity. The liquid component dispersed rapidly throughout the stomach and emptied after a minimal lag period. The emptying of the 25% dextrose was delayed compared with the saline. This delay was associated with increased retention of the liquid in the distal stomach, a significant increase in localised phasic pyloric contractions, and a suppression of antral contractions. The solid component initially resided wholly within a proximal stomach reservoir area. Solids then redistributed from proximal to distal stomach during the emptying of liquid from the stomach. Dextrose delayed gastric emptying of solids compared with saline by increasing the solid lag period and retention in the proximal stomach. There was no significant difference between saline and dextrose meals in the distal stomach retention of solid or in the linear rate of emptying after the lag period. We conclude that, contrary to general opinion, the proximal stomach plays an important role in the control of gastric emptying of solids while the distal stomach is important in the emptying of nutrient liquids.

Adolescent↗
PubMed1991

Comparative effects of duodenal and ileal intubation on gastric emptying and postprandial antral, pyloric, and duodenal motility.

The influence of gastric and small-intestinal intubation on fed patterns of antropyloroduodenal motility and gastric emptying of a solid meal has been investigated in normal volunteers. In 10 subjects a manometric assembly was passed as far as the fourth part of the duodenum; in 8 other subjects the terminal ileum was intubated; and a further 8 subjects were not intubated. The manometric assemblies were similar, apart from their length, and both incorporated a sleeve/side hole assembly located across the pylorus. All subjects ingested a meal of 100 g 99mTc-labelled liver/ground beef. There was no significant difference in either the lag phase or the linear emptying phase of gastric emptying between the control and duodenal intubation groups. The emptying phase of the test meal, but not the lag phase, was slower (p less than 0.01) in the ileal intubation group than in the non-intubated and duodenal intubation groups. There were fewer (p less than 0.01) antral pressure waves in the ileal than in the duodenal intubation group. We conclude that ileal but not duodenal intubation has an important inhibitory influence on gastric emptying and antral motility.

Adult↗
PubMed1990

Gestational trophoblastic tumours following initial diagnosis of partial hydatidiform mole.

11 patients registered with an initial diagnosis of partial hydatidiform mole (PHM) subsequently required chemotherapy for a gestational trophoblastic tumour. In a retrospective review by histopathological examination and measurement of DNA ploidy, the diagnosis was confirmed as PHM in 5 cases and revised to complete hydatidiform mole in 4; in 2 cases there was no evidence of a molar pregnancy. 4 of the patients with PHM had no other known pregnancy before the gestational trophoblastic tumour and in 2 of these patients the tumour was diagnosed histologically as choriocarcinoma. Not all patients in whom PHM was diagnosed at referring hospitals proved to have the condition. Although the risk of a patient with PHM requiring chemotherapy for gestational trophoblastic tumour is of the order of 1 in 200, compared with 1 in 12 after a complete mole, there is no justification for excluding a patient from follow-up after the evacuation of a PHM.

Adult↗