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Biomedical subjects

N W Read

Publications and source records attributed to N W Read.

At least 145 records · Page 8Linked to original sources
PubMed1990

Effect of prefeeding lipid on food intake and satiety in man.

Experiments were carried out in normal volunteers to investigate whether preingestion of lipid reduces food intake. In the first set of experiments, 300 ml beef consomme soup with or without 60 g margarine was fed to each of six volunteers, followed 20 minutes later by either a low fat solid meal or a preselected appetising meal. Subjects were allowed to eat as much of the meal as they wished. Preingestion of the high fat soup had no significant effect on the consumption of either of the solid meals and did not influence sensations of hunger or fullness. As we have previously shown that prefeeding a fatty soup delays gastric emptying of a subsequent meal, this suggests that gastric distension may play a relatively minor role in regulating food intake. In the second set of experiments, we studied the effect of ingesting either a high fat breakfast (65 g fat, 927 kcal) or a similar low fat breakfast (8-1 g fat, 418 kcal) on the consumption of a preselected appetising lunch in six healthy volunteers. The high fat breakfast significantly reduced the amount of the meal eaten at lunchtime (p less than 0.02), the total energy intake from the meal (p less than 0.05) and the rate of eating (p less than 0.05) compared with the low fat breakfast. When the subjects were presented with their lunchtime meal they felt significantly less hungry after the high fat breakfast (p less than 0.05). Only a small proportion of either meal (15% of the high fat meal v 12% of the low fat meal) remained in the stomach and plasma glucose concentrations had returned to fasting levels. Plasma triglyceride concentrations were much higher at lunchtime after ingestion of the high fat breakfast (p<0.001). The energy intake from the breakfast and lunch combined was not significantly different on the high fat breakfast day, indicating that the energy consumption at lunch compensates for the amount eaten at breakfast. These results are compatible with the concept that the interaction of nutrients with small intestinal receptors may play a part in limiting food intake.

Blood Glucose↗
PubMed1990

Effect of ingestion of fat on ileostomy effluent.

Infusion of fat into the ileum slows small bowel transit and increases absorption of a carbohydrate meal. Paired studies were undertaken to investigate the effect of adding fat to the diet on gastrointestinal transit and absorption in eight people with terminal ileostomies. Each subject ate a daily diet that contained either low or high levels of fat but equivalent amounts of carbohydrate, protein, and fibre. Solid and liquid markers were added to the food to measure transit times. The ileostomy outputs after the meals were analysed for protein, fat, carbohydrate, polyethylene glycol, and the delivery of solid markers. All subjects produced more ileal effluent while taking the high fat diet compared with the low fat diet. Fat and protein outputs were significantly higher on the high fat days, but a greater proportion of the fat was absorbed during the high fat diet compared with the low fat diet. The output of carbohydrate on the two diets was not significantly different. The incorporation of fat in the diet produced no significant differences in the transit times of the first marker, but a slight prolongation of the transit time of the second marker. Increasing the fat content of the diet did not slow small bowel transit or increase nutrient absorption. The increase in protein and water output could be explained by an increased secretion of pancreatic enzymes.

Dietary Fats↗
PubMed1990

Effect of coffee on distal colon function.

Ninety nine healthy young volunteers (58 men, 34 women, aged 17-27 years) answered a questionnaire concerning their bowel habit with particular reference to the effects of beverages. Twenty nine per cent (63% women) claimed that coffee induced a desire to defecate. The rectosigmoid motor responses to black, unsweetened coffee were then investigated by multiport manometry in 14 healthy-subjects (12 men, two women, eight of whom claimed coffee caused a desire to defecate (responders). Results revealed an increase in motility index within four minutes after ingestion of both regular and decaffeinated coffee (p less than 0.05) in the eight responders, but not in the six non-responders. The increase in rectosigmoid motility induced by coffee lasted at least 30 minutes. There was no increase in the motility index in any subject after a drink of hot water. These results suggest that drinking coffee can stimulate a motor response of the distal colon in some normal people.

Adolescent↗
PubMed1990

Relation between rectal sensation and anal function in normal subjects and patients with faecal incontinence.

The relation between sensory perception of rapid balloon distension of the rectum and the motor responses of the rectum and external and internal anal sphincters in 27 normal subjects and 16 patients with faecal incontinence who had impaired rectal sensation but normal sphincter pressures was studied. In both patients and normal subjects, the onset and duration of rectal sensation correlated closely with the external anal sphincter electrical activity (r = 0.8, p less than 0.0001) and with rectal contraction (r = 0.51, p less than 0.001), but not with internal sphincter relaxation. All normal subjects perceived a rectal sensation within one second of rapid inflation of a rectal balloon with volumes of 20 ml or less air. Six patients did not perceive any rectal sensation until 60 ml had been introduced, while in the remaining nine patients the sensation was delayed by at least two seconds. Internal sphincter relaxation occurred before the sensation was perceived in three of 27 normal subjects and 11 of 16 patients (p less than 0.001), and could be associated with anal leakage, which stopped as soon as sensation was perceived. The lowest rectal volumes required to induce anal relaxation, to cause sustained relaxation, or to elicit sensations of a desire to defecate or pain were similar in patients and normal subjects. In conclusion, these results show the close association between rectal sensation and external anal sphincter contraction, and show that faecal incontinence may occur as a result of delayed or absent external anal sphincter contraction when the internal anal sphincter is relaxed.

Adult↗
PubMed1990

Relationship between fluctuations of pH and pressure in the human stomach and duodenum.

The normal patterns of pressure activity in the antrum, pylorus and duodenum and associated pH changes were monitored in 9 healthy volunteers under fasted conditions and after ingestion of 300 ml of chocolate milk. The manometric assembly incorporated three side holes in the antrum, four side holes in the duodenum, a sleeve sensor positioned across the pylorus, and pH electrodes situated in the terminal antrum and proximal duodenum. The most common motor pattern recorded under fasting conditions consisted of regular co-ordinated contractions, most of which involved the antrum and duodenum, showed evidence of propagation and was associated with transient decreases in duodenal pH and transient increases in antral pH. Ingestion of milk changes the motor pattern to one that was composed of pressure waves which were confined to the pylorus with few or no pressure waves in the terminal antrum or proximal duodenum. Isolated pyloric pressure waves were gradually replaced by propagated antropyloroduodenal contractions which were associated with transient decreases in duodenal pH. Isolated pyloric pressure waves were not associated with episodes of duodenal acidification under fed conditions.

Adult↗
PubMed1990

Gastrointestinal motility in patients with ulcerative colitis.

In the first study 62 patients with ulcerative colitis and 20 healthy controls were fed a test meal of mashed potatoes and baked beans containing transit markers. Mouth-to-caecum transit was significantly slower in the patients than in controls; gastric emptying, however, was similar. Patients with active colitis had proximal colonic stasis, with rapid transit through the rectosigmoid region. In the patients with quiescent colitis the colonic distribution of markers was normal. Stool weight and frequency were significantly higher in the patients with active colitis. In the second study anorectal function was assessed in 29 patients with ulcerative colitis and in 12 healthy controls by measuring interluminal pressures at multiple sites in the anus and rectum before and during serial distention of a rectal balloon. Overall, resting and maximum squeeze sphincter pressures did not differ in patients with active or quiescent colitis and controls; however, in six patients with moderately severe colitis and incontinence, maximum squeeze pressure was significantly lower than in controls. The rectal volumes required to induce sensations of wind, a desire to defaecate, and pain were significantly lower in the patients with active colitis than patients with quiescent colitis and controls. Rectal pressures in response to rectal distention were higher in patients with active colitis. During disease remission rectal sensitivity decreased and rectal compliance increased. In the third study integrated pressure activity of the sigmoid colon, rectum, and anus was studied in patients with ulcerative colitis and healthy controls before and during provocation by rectal infusion of 1500 ml of warm saline.(ABSTRACT TRUNCATED AT 250 WORDS)

Colitis, Ulcerative↗
PubMed1989

Duodenal bulb acidity and the natural history of duodenal ulceration.

Fasting and post-prandial duodenal bulb pH was recorded in 10 subjects with untreated duodenal ulcers (DU), 10 subjects with healed DU, and 15 healthy volunteers. During fasting, pH was less than 4 for a greater percentage of time in healed than in active DU. Ingestion of a solid test meal accentuated this difference: subjects with active DU and controls both showed less bulb acidification than subjects with healed ulcers. Bulb pH was similar in patients with active ulceration and controls. The finding of neutral bulb pH with active ulceration and low bulb pH with healing may explain the typical cycle of spontaneous healing and relapse in duodenal ulcer disease.

Adult↗
PubMed1989

Abnormal jejunal potential difference in cystic fibrosis.

Transmucosal potential difference (PD) and intraluminal pressure were recorded from the same jejunal site in 15 healthy adult controls and 4 adults with cystic fibrosis. In the controls, runs of contractions were associated with wave-like changes in PD with, during phase III-like activity, a mean peak amplitude of -9.7 mV. Although there were no obvious differences in motor patterns, wave-like changes in PD were absent in patients with cystic fibrosis. Intraluminal boluses of 4 mg pilocarpine, or 0.1 mg prostaglandin E2, caused changes of -4.6 mV and -4.5 mV, respectively, in controls; these responses were not seen in patients with cystic fibrosis. There were no significant differences in basal PD and PD changes caused by altered concentrations of infused saline or glucose between patients and controls.

Action Potentials↗
PubMed1989

A common pathophysiology for full thickness rectal prolapse, anterior mucosal prolapse and solitary rectal ulcer.

Anorectal pressures at rest, during conscious contraction of the external sphincter, during serial distension of the rectum and during straining to inflate a balloon were measured in 56 patients (21 patients with full thickness rectal prolapse, 24 patients with anterior mucosal prolapse, 11 patients with solitary rectal ulcer) and in 30 normal subjects. Both basal and squeeze pressures were significantly lower in the three groups of patients compared with matched normal controls (P less than 0.05). During increases in intra-abdominal pressure, anal pressure remained above maximum rectal pressure (P less than 0.05) in normal controls, with the highest anal pressures being recorded in the most caudal anal channels. In contrast, anal pressures tended to be lower than rectal pressures during this manoeuvre in patients with rectal prolapse, anterior mucosal prolapse and solitary rectal ulcer, and the highest pressures were recorded in the channels nearest the rectum. During serial distension of the rectum, 64 per cent of patients with solitary rectal ulcer, 75 per cent with anterior mucosal prolapse and 76 per cent with rectal prolapse, but only 10 per cent of controls, showed repetitive rectal contractions. The highest anal pressure always remained higher than rectal pressure during rectal distension in normal subjects (P less than 0.05) but not in patients. The threshold rectal volume required to cause a desire to defaecate and the maximum tolerable volume were significantly lower (P less than 0.05) in each of the patient groups, compared with normal subjects. The similarity in the results from patients with rectal prolapse, anterior mucosal prolapse and solitary rectal ulcer support the hypothesis that they share a common pathophysiology. In each of the groups, the rectum is hypersensitive and hyper-reactive, and weakness of the anal sphincter creates the conditions for prolapse of the rectum to occur into or through the anal canal.

Adult↗
PubMed1989

External and internal anal sphincter responses to rectal distension in normal subjects and in patients with idiopathic faecal incontinence.

The responses of the external anal sphincter and the internal anal sphincter to rectal distension were studied in 18 female patients who had idiopathic faecal incontinence with perineal descent and 11 female control subjects, by measuring pressures at six sites within the anal canal and the electrical activity of the external sphincter. The pressure profile in the normal anal canal, at rest, was asymmetric with the highest pressure recorded in the outermost channels. Rectal distension caused a transient increase in the activity of the external sphincter, which was associated with an increase in anal pressure, particularly in the outermost two channels. This was followed by a symmetrical reduction in anal pressure throughout the anal canal, caused by relaxation of the internal sphincter and shortening of the high-pressure zone. Two patterns of response were observed in the patients with idiopathic incontinence. Twelve patients (group 1) showed normal anal relaxation, but the maximum anal pressures recorded during rectal distension or a conscious squeeze were abnormally low, suggesting weakness of the external anal sphincter. The remaining six subjects (group 2), who were older than the group 1 patients, had much lower resting pressures and showed only external sphincter contraction in response to rectal distension, with no obvious internal sphincter relaxation. However, the maximum pressures recorded during a conscious contraction of the external sphincter were lower in this group than in the normal control subjects. These results suggest that group 2 patients have impaired internal anal sphincter tone, as well as external anal sphincter weakness. This may explain why all except one of the group 2 patients, compared with only 17 per cent of group 1 patients, reported incontinence to both solids and liquids.

Adult↗
PubMed1989

Idiopathic constipation associated with impaired urethrovesical and sacral reflex function.

Sixteen chronically constipated women (age range 20-66 years) and 29 healthy control subjects (age range 22-53 years) underwent neurophysiological assessment of the integrity of pelvic spinal reflexes. The results were compared with videourodynamic studies and multiport anorectal manometry combined with external anal sphincter electromyography. The neurophysiological assessment consisted of electrical stimulation of the dorsogenital nerve, while recording any evoked reflex activity in the external anal and urethral sphincters with concentric needle and surface electrodes. Of these constipated women, 75 per cent had absence of one or more evoked sacral reflexes (compared with 20 per cent of healthy controls, P less than 0.05). Sensory thresholds and motor unit potentials in the external anal sphincter were similar in healthy and constipated women. Nine (56 per cent) constipated women displayed urodynamic abnormalities (increased bladder capacity, acontractile bladder and genuine stress incontinence). Only 38 per cent of constipated women perceived a desire to defaecate during rectal distension with up to 100 ml, compared with 95 per cent of normal subjects (P less than 0.0005). Moreover, 73 per cent of constipated women did not relax the external anal sphincter during defaecation, compared with 12 per cent of controls (P = 0.001). Taking into account the possible significance of our data in relation to previous findings it is suggested that the integration of sensory information within the sacral cord may be impaired in chronic idiopathic constipation.

Adult↗
PubMed1989

Anorectal function in normal human subjects: effect of gender.

Multiport anorectal manometry and external anal sphincter (EAS) and internal anal sphincter (IAS) electromyography were conducted in 15 males (41 +/- 3 years) and 20 females (43 +/- 2 years; 5 nulliparous) during rest, maximum conscious sphincter contraction, rectal distension and increases in intra-abdominal pressure. The basal pressure declined within 15 minutes of insertion of the manometric probe to a stable plateau, 55 +/- 4% of the initial value. The maximum basal (91 +/- 5 vs 61 +/- 6 cm water; mean +/- SEM), minimum basal (43 +/- 7 vs 27 +/- 3 cm water) and the maximum squeeze pressures (257 +/- 20 vs 107 +/- 13 cm water) were higher (p less than 0.05) in males than females. Distension of a rectal balloon caused a reduction in pressure in all anal channels, that increased in depth and duration as the distending volume was increased. These anal relaxations were associated with rectal contractions and transient increases in the electrical activity of the EAS. Upon deflating the balloon, the anal pressure increased to values that exceeded the pre-inflation values. The pre-inflation (89 +/- 4 vs 49 +/- 4 cm water), post-inflation (104 +/- 9 vs 62 +/- 7 cm water) and residual (47 +/- 4 vs 30 +/- 2 cm water) pressures during rectal distension were significantly higher in males than in females (p less than 0.05). The higher residual pressure in males was associated with a higher EAS index during rectal distension (0.94 +/- 0.10 vs 0.65 +/- 0.10 mv s; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Pyloric motor response to intraduodenal dextrose involves muscarinic mechanisms.

The delivery of dextrose solutions to the duodenum is associated with the stimulation of phasic and tonic pyloric contraction. In this study, the effects of intravenous atropine on the antropyloroduodenal motor responses to intraduodenal infusions of 25% dextrose were assessed in 10 normal volunteers. Antropyloroduodenal pressures were recorded with a manometric assembly incorporating a sleeve sensor spanning the pylorus, and sideholes in the antrum and duodenum. In each experiment, three intraduodenal infusions of 25% dextrose were given at a rate of 4 ml/min, for a median duration of 19 min (range 17-20). During the second dextrose infusion, intravenous atropine was given as a bolus (15 micrograms/kg) followed by an infusion (4 micrograms/kg.min), which was continued until the end of each experiment. Before atropine was given, the pyloric motor response to the second dextrose infusion was not significantly different from the response to the first infusion, but after administration of atropine there was a rapid decrease in the rate of isolated pyloric pressure waves, from 0.8 to 0.1 per minute (p less than 0.05). The isolated pyloric pressure wave response to the third dextrose infusion was completely blocked, and there was a much smaller maximum increase in basal pyloric pressure compared with the first infusion (p less than 0.01). This study indicates that intraduodenal dextrose reproducibly stimulates isolated pyloric pressure waves and increases basal pyloric pressure by mechanisms that involve muscarinic receptors.

Adult↗
PubMed1989

Impaired internal anal sphincter in a subgroup of patients with idiopathic fecal incontinence.

During multiport manometric recordings of the anorectum, 35 of 140 patients with idiopathic fecal incontinence had abnormally weak sphincters that did not relax during rectal distention, suggesting impaired function of the internal anal sphincter. This study documents this finding and compares anorectal function in these 35 patients with 25 matched normal subjects and the remaining 105 incontinent patients. Basal and squeeze pressures were significantly lower in the incontinent study group than in the other two groups. During rectal distention, 25 of 35 patients showed no anal relaxation at any volume, whereas 10 patients showed some relaxation after 60-ml distention because of the postinflation rebound in internal anal sphincter tone. The electrical responses of the external anal sphincter to rectal distention and to increases in intraabdominal pressure were greater in patients than in normal subjects, but the anal pressures were lower and anal leakage was common. Rectal sensations were not significantly different from normal subjects. These results indicate that 25% of patients with idiopathic fecal incontinence have markedly impaired function of the internal anal sphincter, but these patients also have extremely weak external sphincters.

Adult↗
PubMed1989

Gastrointestinal correlates of the development of hunger in man.

Experiments were carried out on ten healthy male volunteers to investigate the relationship between the return of hunger after a meal and gastric emptying, blood glucose levels and small intestinal motor patterns. There was a significant correlation between the postprandial increase in hunger ratings and the time for 90% of the meal to empty (r = 0.75, p less than 0.02): hunger ratings started to increase in three subjects when over 40% of the food still remained in the stomach, and they continued to increase in all subjects even when the meal had ceased to empty from the stomach. These results suggest the reduction of gastric distension may have a permissive role in the development of hunger after a meal. The increase in hunger was not related to any consistent change in plasma glucose concentration. Finally, the postprandial onset of a fasting motor pattern (phase-III-like activity) always occurred when the stomach had emptied more than 80% of its contents and after hunger had increased. Our data are compatible with the hypothesis that the return of hunger is directly related to a decline in the exposure of the upper small intestine to nutrient stimuli, but could be modulated by gastric distension.

Adult↗
PubMed1989

The effect of incorporating fat into different components of a meal on gastric emptying and postprandial blood glucose and insulin responses.

1. Three studies were carried out in each of six normal volunteers to investigate how lipid, when given at different stages during the course of a meal, affects gastric emptying and postprandial blood glucose and insulin concentrations. 2. The control meal consisted of 300 ml beef consommé (50 kJ, 12 kcal), followed 20 min later by 300 g mashed potato (908 kJ, 217 kcal). In the two test meals, 60 g margarine were incorporated into either the soup or the mashed potato. 3. The addition of margarine to either component of the meal delayed gastric emptying of the mashed potato (P less than 0.05), but the pattern varied according to the component to which the fat was added. 4. Incorporation of fat into the soup increased the lag phase (P less than 0.05) but did not influence the slope of emptying of the mashed potato, while incorporation of fat into the mashed potato reduced the slope of emptying of the mashed potato (P less than 0.05) but did not influence the lag phase. 5. Addition of fat to either component of the meal reduced postprandial blood glucose (P less than 0.05) and insulin responses, but when the fat was incorporated in the soup, peak glucose and insulin responses were delayed as well (P less than 0.05). 6. The results show that the effect of fat on gastric emptying and absorption of nutrients depends on when, in relation to the other components of the meal, the fat is consumed.

Adult↗
PubMed1989

Effect of bile acid on anorectal function in man.

The effects of rectal infusions (500 ml) of deoxycholic acid (1 mmol/l, 3 mmol/l) or normal saline on basal anorectal motility and responses to rectal distension were studied in 11 normal volunteers. Deoxycholic acid (1 mmol/l) did not alter anorectal motor patterns under basal conditions but reduced the rectal volumes required to induce a desire to defecate (deoxycholic acid 76 (12) ml v saline 123 (12) ml; mean (SEM) p less than 0.01), and to produce anal relaxation (deoxycholic acid 83 (14) ml v saline 152 (24) ml; p less than 0.05) and perception of the rectal balloon (deoxycholic acid 56 (10) ml v saline 104 (17) ml; p less than 0.01) that were sustained for the period of distension (1 min). Seven of 10 subjects could not tolerate an infusion of 3 mmol/l deoxycholic acid. Between two and 30 minutes after the start of the infusion they experienced an extreme urge to defecate which was associated with large amplitude pressure waves in the rectal channels (amplitude 30 (5) mmHg, duration 0.7 (0.1) min, frequency 1.7 (0.4)/min). Such contractions were never seen during saline infusion. Thus, rectal infusion of deoxycholic acid at physiological concentrations increases the sensitivity of the rectum to distension, and promotes an urgent desire to defecate in normal subjects.

Adolescent↗