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Biomedical subjects

N W Read

Publications and source records attributed to N W Read.

At least 181 records · Page 10Linked to original sources
PubMed1988

Symptoms and stool patterns in patients with ulcerative colitis.

The prevalence of symptoms and stool patterns was assessed prospectively in 96 patients with ulcerative colitis subdivided according to the extent and activity of the disease. Increased frequency of defecation (83%), urgency (85%), a feeling of incomplete evacuation (78%) and tenesmus (63%) were the most frequent symptoms experienced by patients with active colitis. All were significantly more common (p less than 0.001) in patients with active than quiescent colitis and their prevalence was similar in those with total and distal colitis, indicating that these symptoms are related to an inflamed and irritable distal colon. Twenty seven per cent of patients with active colitis voided hard stools indicative of constipation, however, and this was more common in active, than quiescent colitis (p less than 0.05). This feature is probably secondary to faecal stasis in the proximal colon, and an apt description of the bowel disturbance in ulcerative colitis, irrespective of the extent of disease is that the colon suffers from proximal constipation and distal irritability.

Adult↗
PubMed1988

Anorectal contractility under basal conditions and during rectal infusion of saline in ulcerative colitis.

Pressure activity in the rectum and anal canal was measured with a multilumen probe in 29 patients with ulcerative colitis (12 active, 11 quiescent, six studied during both phases) and 18 normal controls under resting conditions and during rectal infusion of saline. Resting motor activity was significantly decreased in patients with active colitis compared with quiescent colitis (p less than 0.005) and normal controls (p less than 0.001). Forty per cent of active colitics showed a featureless record compared with only one patient with quiescent colitis and one normal subject. The volume of saline infused before leakage occurred, and the total volume retained were significantly lower (p less than 0.001) in patients with active and quiescent colitis compared with normal controls. Rectal infusion of saline provoked regular rectal contractions, of significantly higher (p less than 0.05) amplitude in patients with active colitis, than in quiescent colitis or controls. These rectal contractions were associated with simultaneous anal relaxations. During saline infusion, peak and pressures were lower in patients with ulcerative colitis than in normal subjects, but there were no significant differences in relaxation pressures. In normal subjects, the rectal pressures remained below the anal pressures throughout the saline infusion. Peak rectal pressures exceeded the anal relaxation pressures during the last five minutes of saline infusion in patients with ulcerative colitis and throughout the infusion in those patients who complained of incontinence. Results suggest that although the resting rectal motor activity is diminished in patients with ulcerative colitis, luminal distension causes the inflamed rectum to generate abnormally strong contractions that may threaten continence.

Adult↗
PubMed1988

Antropyloroduodenal motor responses to intraduodenal lipid infusion in healthy volunteers.

The delivery of lipid to the duodenum has been shown to slow gastric emptying and to increase the resistance to gastric outflow. To investigate mechanisms responsible for these effects, we have recorded antropyloroduodenal motility in nine healthy volunteers during alternate intraduodenal infusions of normal saline and triglyceride emulsion (Intralipid 10%). During the lipid infusions there were reproducible, major changes in the patterns of motility. Pressure waves, apparently isolated to the pylorus, usually started within 10 min of initiation of the lipid infusion. After 20-25 min of lipid infusion these waves occurred at median rates of 2.4 and 2.8/min (1st and 2nd lipid infusions, respectively); these rates were significantly greater (P less than 0.05) than the median rates (all less than or equal to 0.4/min) observed during the equivalent period of the succeeding saline infusions. During 10 of 22 lipid infusions, isolated pyloric pressure waves were associated with sustained pyloric tone. Infusion of lipid into the duodenum suppressed antral pressure waves in all subjects and initiated brief periods of regular duodenal contractions during 11 of 22 infusions. These studies have demonstrated alterations of antropyloroduodenal motor patterns in response to changes in the duodenal luminal content. The effects on antral and pyloric motility are probably of importance in the regulation of transpyloric flow by nutrients in the duodenal lumen.

Adult↗
PubMed1988

Topography and measurement of pyloric pressure waves and tone in humans.

The topography of human pyloric pressure is ill defined, and previous studies of pyloric motility in humans have given conflicting results. A detailed profile of pyloric pressure has been recorded in seven healthy volunteers using a manometric assembly with 13 side holes spaced at 3-mm intervals on reverse aspect of a 3.5-cm long sleeve sensor. After a fasting control period of 40 min, recordings were made for 40 min during intraduodenal infusion of a lipid emulsion. Two major patterns of pressure waves were seen during the fasting control period, namely pressure waves confined to a narrow pyloric zone (isolated pyloric pressure waves) and pressure waves that were less localized and involved the antrum and/or duodenum. During lipid infusion the motility pattern was dominated by isolated pyloric pressure waves and localized pyloric tone. Ninety-two percent of the isolated pyloric pressure waves recorded by the sleeve were recorded by only one or two side holes, consistent with a phasically active zone less than 9 mm in length. Pyloric tone was confined to an even narrower zone and was most often recorded by only one side hole. When both tone and isolated pyloric pressure waves occurred together, they were recorded by the same side holes. By comparison with the side holes, the sleeve recorded 89% of isolated pyloric pressure waves and 98% of nonlocalized waves and recorded pyloric tone with a moderate sensitivity but high specificity. The technical challenge of recording localized pyloric contraction is considerable, and much of the conflict between previous studies of the human pylorus is explicable on methodological grounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Effect of ileal infusion of lipid on jejunal motor patterns after a nutrient and nonnutrient meal.

To investigate how ileal lipid delays small bowel transit, pressure activity was recorded at multiple sites in the human small intestine during ileal infusion of either lipid or saline. Initial studies showed that ileal lipid reduced the contraction rate in the jejunum but not in the duodenum or ileum. The effect of ileal lipid was further investigated by recording pressures at seven sites in the jejunum after ingestion of either a nutrient or a nonnutrient meal. The nutrient meal induced an irregular motility pattern; ileal lipid significantly reduced the contraction rate, the percentage of contractions involved in propagated events, the mean length of propagation, and the propagation index. The nonnutrient meal induced a pattern containing discrete clusters of contractions. Ileal lipid significantly reduced the occurrence of contraction clusters and the mean length of propagation. Thus, although the delay in small bowel transit observed during ileal infusion of lipid can be explained by reductions in the rate and the degree of propagation of jejunal contractions, the mechanism varies according to the type of meal.

Adult↗
PubMed1988

Colon: relationship between epithelial transport and motility.

Although our knowledge of colonic function is still incomplete, the available data support the concept that for most of the time colonic motor activity is adapted to promote absorption and bacterial metabolism. The possibility that this mode of activity may be enhanced and promoted by the products of fermentation is intriguing and needs to be established. Substances that irritate or stimulate the colon, such as unabsorbed fat, bile acids, bacterial enterotoxins and laxatives and excessive delivery of fluid from the small intestine, flush out colonic contents by causing secretion and colonic propulsion.

Biological Transport, Active↗
PubMed1988

Do viscous polysaccharides slow absorption by inhibiting diffusion or convection?

Viscous polysaccharides such as guar gum delay absorption probably by impairing the access of luminal contents to the absorptive epithelium. Measurements of the electrical resistivity of saline solutions were carried out to determine if guar gum (0.5, 0.75 and 1 per cent w/v), in concentrations which impaired absorption in vitro, delayed diffusion of solutes or inhibited convection of luminal contents. Our results indicated that guar had no effect on the mobility of ions in a completely unstirred solution but delayed the time taken for saline solutions of different resistivity to achieve complete mixing, when they were brought into contact inside a vessel, which was rotated at a constant speed. The time taken to achieve complete mixing was directly related to the viscosity of the guar solutions. The effect of intestinal contraction on the absorption of glucose was simulated in an in vitro model, consisting of a length of dialysis tubing, alternately contracted at each end. Movement of glucose out of the dialysis tubing was increased by increasing the rate of contraction. The incorporation of guar gum into the solution prevented the rise in glucose uptake produced by increasing the rate of contraction. These effects suggest that guar probably reduces absorption by resisting the convective effects of intestinal contractions.

Dietary Fiber↗
PubMed1988

Comparison of the effects on colonic function caused by feeding rice bran and wheat bran.

A study was designed to investigate the effects of a new fibre source, rice bran, on colonic function, and to compare it with wheat bran. The diet of eight normal male volunteers was supplemented with similar amounts of indigestible residue from rice (17.1 g/d) and wheat bran (15.0 g/d) for periods of 10 d each. During the last 7 d of each of these periods, and also of a 10-d control period when no supplement was taken, the volunteers collected their stools into plastic bags. This allowed calculation of stool mass and frequency, and gastrointestinal transit time by a continuous radio-opaque marker technique. Rice bran increased the mass of faeces produced and the stool frequency by more than the wheat bran, but both had a similar accelerating effect on the transit time. The mechanism of the efficient stool bulking caused by the rice bran may be due to a high content of retrograded starch.

Adult↗
PubMed1988

Gastrointestinal dynamics and pharmacology for the optimum design of controlled-release oral dosage forms.

This article encompasses a brief discussion of the principles of pharmacodynamics of different types of drugs and the mechanisms of absorption at different sites in the gastrointestinal tract. The importance of factors such as the pH, the unstirred layer or microclimate, gastric emptying, intestinal contact time, metabolism in the gut wall, and bacterial degradation in the colon is discussed. Methods that can be used to alter the absorption of drugs such as formulation in a viscous form, a form that floats in the stomach, position release forms, combination with other drugs that may influence absorption, etc. are examined in detail.

Administration, Oral↗
PubMed1987

Anorectal sensitivity and responses to rectal distention in patients with ulcerative colitis.

Anorectal function in ulcerative colitis was assessed by measuring pressures at multiple sites in the anus and rectum under basal conditions and during balloon distention of the rectum in 29 patients with ulcerative colitis (12 active, 11 quiescent, and 6 during both phases) and in 12 normal controls. Resting and squeeze sphincter pressures were similar in the three groups. The lowest rectal volume that could be perceived, the volume required to induce a desire to defecate, and the maximum tolerable rectal volume were all lower in patients with active colitis than in patients with quiescent colitis (p less than 0.001) and controls (p less than 0.001). The rectal volume required to cause a sustained anal relaxation was lower in patients with active colitis (p less than 0.05) than in controls. Both peak and steady state rectal pressures in response to rectal distention were significantly higher in patients with active colitis than in patients with quiescent colitis (p less than 0.05) and controls (p less than 0.02). Paired studies showed that during remission of disease there was a decrease in rectal sensitivity (p less than 0.05) and an increase in rectal compliance (p less than 0.05). These results suggest that the frequent and urgent defecation, i.e., the predominant feature of active colitis, is related to a hypersensitive and poorly compliant rectum, which, upon distention, is more reactive and is more likely to induce prolonged sphincter relaxation.

Adult↗
PubMed1987

Studies on the mechanism of bowel disturbance in ulcerative colitis.

The transit of a radiolabeled meal through the gastrointestinal tract and stool output were measured in 62 patients with ulcerative colitis, subdivided according to the activity and extent of their disease. The results were compared with those from 20 sex-matched normal subjects. Mouth-to-cecum transit was significantly slower than normal in all patient groups although gastric emptying was normal. Whole gut transit was not accelerated in any group of patients. An abdominal x-ray taken 48 h after ingesting the meal showed that patients with active colitis had proximal colonic stasis, whereas transit through the rectosigmoid region was rapid. Stool weights and frequencies were higher in patients with active colitis than in patients with quiescent disease. Patients with active colitis also passed smaller amounts of stool during each bowel movement, suggesting that they experienced a desire to defecate at lower rectal volumes. These results indicate that (a) diarrhea in ulcerative colitis is associated with rectosigmoid irritability rather than rapid transit and (b) caution should be used when treating active colitis with antidiarrheal drugs that could further retard proximal colonic transit.

Colitis, Ulcerative↗
PubMed1987

Duodenal and ileal lipid suppresses postprandial blood glucose and insulin responses in man: possible implications for the dietary management of diabetes mellitus.

Infusion of lipid into the ileum delays the transit of a meal through the stomach and small intestine and could therefore influence the rate and degree of nutrient absorption. Experiments were carried out on human volunteers to investigate the effect of infusion of lipid into either the duodenum or ileum on blood glucose, insulin and gastric emptying after ingestion of a mashed potato meal. Infusions of lipid into either the duodenum or the ileum significantly reduced or abolished the immediate postprandial rises in blood glucose and insulin and significantly delayed gastric emptying. Blood glucose and insulin rose shortly after the lipid infusion terminated. Addition of corn oil to a meal of mashed potato also reduced blood glucose and insulin and delayed gastric emptying. Intestinal lipid can thus modify the glycaemic and insulinaemic responses to a meal, and this modulation probably explains the reduced metabolic responses to a meal containing fat compared with a fat free meal. This principle could be of value in the dietary control of diabetes mellitus.

Adolescent↗
PubMed1987

Applied potential tomography: a new non-invasive technique for assessing gastric function.

Applied potential tomography is a new, non-invasive technique that yields sequential images of the resistivity of gastric contents after subjects have ingested a liquid or semi-solid meal. This study validates the technique as a means of measuring gastric emptying. Experiments in vitro showed an excellent correlation between measurements of resistivity and either the square of the radius of a glass rod or the volume of water in a spherical balloon when both were placed in an oval tank containing saline. Altering the lateral position of the rod in the tank did not alter the values obtained. Images of abdominal resistivity were also directly correlated with the volume of air in a gastric balloon. Profiles of gastric emptying of liquid meals obtained using APT were very similar to those obtained using scintigraphy or dye dilution techniques provided that acid secretion was inhibited by cimetidine. Profiles of emptying of a mashed potato meal using APT were also very similar to those obtained by scintigraphy. Measurements of the emptying of a liquid meal from the stomach were reproducible if acid secretion was inhibited by cimetidine. Thus, APT is an accurate and reproducible method of measuring gastric emptying of liquids and particulate food. It is inexpensive, well tolerated, easy to use and ideally suited for multiple studies in patients, even those who are pregnant. A preliminary study is also presented that assesses the technique as a means of measuring gastric acid secretion. Comparison of resistivity changes with measured acid secretion following the injection of pentagastrin shows good correlations. APT might offer a non-invasive alternative to the use of a nasogastric tube and acid collection.

Duodenal Ulcer↗
PubMed1987

Viscosity of food gums determined in vitro related to their hypoglycemic actions.

Experiments were carried out in vitro and in normal human subjects to evaluate alternative food-grade viscous polysaccharides as agents for reducing postprandial hyperglycemia and to assess the relationship between the in vitro and in vivo performance of the polysaccharides. A 1:1 mixture of xanthan and locust bean gum (X/LBG) had the greatest viscosity at equivalent concentrations and shear rates and was more effective than guar gum, xanthan, or locust-bean gum at inhibiting glucose movement in vitro. It was not, however, more efficient in lowering postprandial blood glucose and plasma insulin in human subjects when incorporated in a drink containing 50 g glucose. When the different gums were acidified and reneutralized to mimic conditions in the gut, there was a better correlation between viscosity and blood glucose and plasma insulin levels. This effect may explain why X/LBG was no more effective than the other gums in reducing postprandial hyperglycemia in man.

Adolescent↗
PubMed1987

A comparative study of the effect of cimetidine and ranitidine on the rate of gastric emptying of liquid and solid test meals in man.

Paired studies were carried out on 18 healthy male volunteers (20.9 +/- 1.9 years; mean +/- S.D.) to compare the effect of oral doses of the H2-receptor antagonists, ranitidine and cimetidine, on the rate of gastric emptying of radiolabelled solid and liquid test meals. Oral administration of ranitidine 300 mg accelerated the emptying of a liquid meal from the stomach, but it had no significant effect on the rate of emptying of a solid meal. Oral administration of either 400 or 800 mg cimetidine did not alter the rate of emptying of either the liquid or the solid meals from the stomach.

Adolescent↗
PubMed1987

Effect of naloxone, domperidone and idazoxan on the delay in gastric emptying induced by ileal lipid.

Studies were carried out on 22 healthy male volunteers to investigate whether intravenous administration of either the opiate antagonist, naloxone, or the dopamine antagonist, domperidone, or the alpha 2-adrenoreceptor antagonist, idazoxan, could reverse the delay in gastric emptying induced by ileal infusion of lipid emulsion. Ileal infusion of 50% lipid emulsion significantly delayed the rate of gastric emptying compared with ileal infusion of isotonic saline (P less than 0.01). Intravenous infusion of naloxone (20 micrograms kg-1 hour-1) or prior administration of either intravenous domperidone (20 mg) or idazoxan (0.2 mg kg-1) did not inhibit the delay in gastric emptying induced by ileal infusion of lipid emulsion. These observations indicate that feedback regulation of gastric emptying by ileal lipid does not appear to be mediated by either dopaminergic or enkephalinergic neurons, nor by alpha 2-adrenoreceptors.

Adolescent↗
PubMed1987

The effect of two alpha 2-adrenoreceptor agonists and an antagonist on gastric emptying and mouth to caecum transit time in humans.

Experiments were performed to investigate the effect of two alpha 2-adrenoreceptor agonists, clonidine and lidamidine, and a specific alpha 2-adrenoreceptor antagonist, idazoxan, on gastric emptying and mouth to caecum transit time (MCTT) of a radiolabelled meal in 27 healthy male subjects. Lidamidine (20 mg p.o.) and clonidine (0.3 mg p.o.), given alone had no significant effect on gastric emptying or MCTT suggesting that the anti-diarrhoeal action of clonidine and lidamidine are unlikely to be explained by a slowing of small intestinal transit. Idazoxan (20 mg p.o.) reversed the effect of clonidine in 10 subjects, who showed a delay in MCTT after taking clonidine, but did not alter MCTT under basal conditions. These results suggest that although the sympathetic nervous system can influence upper gastrointestinal motility by an action on alpha 2-adrenoreceptors, this action does not exert a tonic influence on upper gastrointestinal motility under basal conditions.

Adolescent↗