Myogenic basis of motility in the pyloric region of human and canine stomachs.

In vitro gastric motility was investigated in 48 human and 16 canine stomachs by measuring the mechanical activity of isolated muscle strips under auxotonic conditions. For a precise regional differentiation, we recorded the mechanical activity of longitudinal and circular strips from fundus, corpus and antrum, as well as from circular preparations of the inner and outer layer of the pyloric sphincter and from the duodenum. The analysis showed that the anatomical division of the stomach into three distinct regions resulted physiologically in different patterns of contraction in vitro for each region. The fundus exhibited purely tonic spontaneous activity and a tonic contraction pattern after application of acetylcholine whereas the activity in the circular antrum was purely phasic. A combination of tonic and phasic contractions was found in the corpus and longitudinal antrum. A major difference in the basic spontaneous activity pattern was evident between man and dog. A gradient of intrinsic frequency in the stomach from proximal to distal was seen in the dog but not in man. A physiologically distinct area exists in the pyloric region of both species adjacent to the antrum and duodenum. The pyloric ring has its own spontaneous activity (minute-rhythm), reacts to the application of acetylcholine with relatively weak contractions and, unique to the dog, was delineated by histamine-induced maximal contractions. The results provide evidence that the pyloric ring is a distinct organ with specific functional characteristics in its cellular-myogenic structure.     

Diameter and wall thickness recording of canine pylorus with implantable miniature ultrasonic transducers.

Outer diameter and thickness of the muscular wall of canine pylorus were measured simultaneously by determining the distance between pairs of implanted ultrasonic transducers, evaluating the sonic transit time with a digital sonometer. For the study of the motility in the gastroduodenal transit zone, the ultrasonically determined pyloric responses were compared with signals from conventional strain-gauge transducers sutured to the neighboring duodenum and gastric antrum. After stimulation of the gastrointestinal motility by an intravenous bolus injection of cholecystokinin octapeptide, pyloric contractions with a frequency of 5.2 min-1 could be recorded for some minutes; those contractions were independent of the more rapid antral and duodenal motility. Together with the observed tonic constriction of the pyloric ring, which could be inhibited by intravenous injection of adrenaline, an autonomous role of the gastroduodenal junction as a true sphincter is supported.     

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.     

Dynamic imaging of the stomach by real-time ultrasound--a method for the study of gastric motility.

The use of real-time ultrasonic imaging of the stomach for the study of gastric contractions in response to a liquid test meal is described. Gastric contractions in the pyloric antrum and distal body of the stomach were observed on closed circuit television, recorded on to cassette tape and also imaged on polaroid and ciné film. Gastric contractions were recorded from the pyloric antrum by longitudinal scanning in the lower epigastrium and reproducible motility tracings were obtained on a fibreoptic chart recorded. Intravenous metoclopramide enhanced the magnitude and frequency of antral movement, which was abolished by intravenous propantheline. Real-time ultrasonic imaging permits the non-invasive study of gastric contractions. It is safe, may be repeated as required, and provides a method for the study of the effect of drugs and disease states on gastric motility.     

Motor activity of the gastric antrum, pylorus, and duodenum under fasted conditions and after a liquid meal

Because the mechanisms that control the movement of food and digestive juices across the human pylorus are not completely understood, the aim of this study was to document the normal patterns of pressure activity in the antrum, pylorus, and duodenum and the associated pH changes in 9 healthy volunteers. Studies were carried out under fasting conditions and after ingestion of 300 ml of chocolate milk, using a unique 11-channel intraluminal probe that incorporated 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 coordinated contractions, most of which (a) involved the antrum and duodenum, (b) showed evidence of propagation through two or more adjacent channels, and (c) were associated with transient reductions in duodenal pH and transient elevations in antral pH. Ingestion of milk changed 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 antroduodenal contractions, which eventually occurred at a regular frequency that was higher than that observed under fasting conditions. After ingestion of milk, only the coordinated contractions were associated with transient reductions in duodenal pH. Isolated pyloric pressure waves were also observed under fasting conditions just before or just after phase III of the migrating motor complex, and 17% of these were accompanied by episodes of duodenal acidification.     

Pyloric motility

Intraduodenal infusion of nutrients has been shown by intraluminal sleeve-sidehole manometry to suppress antral contractions and stimulate isolated pyloric pressure waves (IPPWs) in humans. It is still unresolved, whether these pyloric contractions occur within an otherwise quiescent zone of motor and electrical activity and whether the presence of the sleeve sensor itself affects this nutrient-associated response. In four conscious dogs, comparisons were made between paired recordings of myoelectrical and motor activities of the antropyloroduodenal region with serosal strain gauge transducers and extracellular bipolar electrodes in the presence and absence of an intraluminal manometric sleeve-sidehole assembly during intraduodenal infusions of saline and a triglyceride emulsion (Intralipid 10%, 0.5 kcal/min). Of 287 isolated pyloric pressure waves, detected by the manometric sleeve sensor, 75% were detected as isolated pyloric contractions by the strain gauge transducers and 72% occurred in the absence of electrical spike activity in the distal antrum or proximal duodenum. The lower incidence of isolated pyloric contractions (strain gauges) was related to: (1) insensitivity of the pyloric strain gauge transducer in comparison to the manometric sleeve sensor (10%), and (2) inability of the manometric sleeve-sidehole assembly to detect pressure waves in the distal antrum (7%) or proximal duodenum (8%) during antral or duodenal wall motion. The presence of the sleeve sensor itself did not affect the number of lipid-induced isolated pyloric contractions but increased their amplitude [median 9 (7–15) mN vs 4 (2–6) mN;P<0.05]. We conclude that: (1) most isolated pyloric pressure waves recorded by the manometric sleeve sensor represent contractions truly isolated to the pylorus, and (2) the presence of a sleeve sensor does not influence the number of isolated pyloric contractions.     

食管、贲门切除术中附加幽门气囊扩张预防术后早期胃潴留

设计并进行了食管、贲门切除术中应用耐压气囊行幽门扩张的实验和临床研究。结果表明,此法将幽门环形肌纤维拉长,幽门内径增大,减少了胃排空时阻力,有效防止了术后早期胃潴留;且扩张造成的肌纤维损伤能逐渐修复,使幽门功能得到保存。对幽门扩张内径进行了讨论。认为幽门扩张法简便易行,安全可靠,值得推广。     

Intravenous erythromycin overcomes small intestinal feedback on antral, pyloric, and duodenal motility.

The retardation of gastric emptying caused by intraduodenal lipid is associated with suppression of antral contractions and stimulation of localized pyloric contractions. Similar patterns of motility have been described in patients with gastroparesis. The effect of erythromycin on the antropyloroduodenal motor responses to intraduodenal lipid was investigated. In 17 volunteers an intraduodenal lipid infusion (10% Intralipid) was given at 1 mL/min for 50 minutes. Either erythromycin (3 mg/kg) or saline was administered IV for 15 minutes, beginning 20 minutes after the start of the intraduodenal lipid infusion. Antral, pyloric, and duodenal motility were measured with a sleeve/sidehole manometric assembly. Intraduodenal lipid stimulated localized pyloric contractions. Erythromycin suppressed localized phasic (P less than 0.003) and tonic (P less than 0.002) pyloric pressure waves and stimulated antral (P less than 0.003) and duodenal pressure waves (P less than 0.02). After erythromycin antral pressure waves were usually of high amplitude (greater than 50 mm Hg) and often associated with duodenal pressure waves. It was concluded that erythromycin overcomes the effects of intraduodenal lipid on antral, pyloric, and duodenal motility. These effects probably contribute to the gastrokinetic properties of erythromycin.     

Coordinated motor activity of the human gastroduodenal region

Using real-time ultrasonic imaging, and a test meal of 500 ml of dilute orange juice, we have studied the temporal relationships among contractions of the terminal antrum, pylorus, and proximal duodenum of 22 normal subjects. A total of 259 cyclical periods of motor activity were observed. Individual mean gastroduodenal cycle times ranged from 17.9 to 29.6 seconds (2.0–3.3 cycles/min). Terminal antral contractions (TACs) were observed 98% of cycles and pyloric closure invariably occurred at the midpoint of these contractions. The pylorus then opened as the terminal antrum relaxed and remained open until the next TAC. Only 67% of TACs were associated with contractions of the proximal duodenum (DC), but 94% of these occurred about 1 sec (range 1 sec before to 2 sec after) after pyloric closure. Only 6% of DCs were ectopic, in that their occurrence was apparently uncoordinated with the TACs. Our observations demonstrate that after ingestion of a test meal, the human terminal antrum, pylorus, and proximal duodenum usually contract in sequential coordinated manner, presumably under the control of the gastric slow wave. No evidence of independent pyloric closure was obtained.This work was supported by Scottish Home and Health Department grant K/MRS/50/C423.     

Comparative studies on epithelial lesions at gastric cardia and pyloric antrum in subjects from a high incidence area for esophageal cancer in Henan, China

AIM To investigate the pathogenesis of gastric cardia and the distal part of stomach cancer and to further characterize the histopathogenesis model for gastric cardia cancer from the high-risk population for esophageal cancer.METHODS Mass survey with endoscopic mucosa biopsy and histopathological examination were carried out on 226 subjects aged above 30 years. Three biopsies were collected one each from the middle part of the esophagus, the gastric cardia and the pyloric antrum. The biopsy tissue was fixed with 85% alcohol and paraffin-embedded.RESULTS The incidence of intestinal metaplasia and dysplasia at gastric cardia epithelium was higher than that at the pyloric antrum from the subjects in the same area. And there were high incidences of both esophageal and gastric cardia cancer, but a low incidence of gastric cancer at the distal part of the stomach.CONCLUSION There might be different etiology and pathogenesis of gastric cardia and pyloric cancer at the distal part of the stomach.     

Nitric oxide mediates mechano- and chemoreceptor-activated intestinal feedback control of gastric emptying

The effect of nitric oxide (NO) synthase inhibition on the gastric emptying of nutrient and nonnutrient meals was investigated in nine dogs. The inhibition of NO synthase delayed the gastric emptying time of both nutrient and nonnutrient meals, but the percentage delay of nutrient meals was significantly greater than that of nonnutrient meals. The inhibition of NO synthase during the emptying of nonnutrient meals enhanced mainly the amplitude of antral, pyloric, and distal duodenal contractions. However, NO synthase inhibition during the emptying of nutrient meals stimulated several spatial and temporal parameters of gastropyloroduodenal contractions. We conclude that NO is one of the neurotransmitters of intestinal feedback that regulates the gastric emptying of both nutrient and nonnutrient meals. The nature and intensity of intestinal feedback by the stimulation of both chemo- and mechanoreceptors by nutrient meals is different from that by the stimulation of mechanoreceptors only by the nonnutrient meals.Supported in part by grants from the Department of Veterans Affairs Research Service and National Institutes of Diabetes, Digestive and Kidney Diseases, DK32346.     

Comparative studies on epithelial lesions at gastric cardia and pyloric antrum in subjects from a high incidence area for esophageal cancer in Henan, China

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Gastric pacemakers.

Gastric electrical control activity (ECA) controls the sequence of occurrence of contractions in the gastric wall. Normally, the direction of phase lag among control waves is aborad, and hence a ring of contraction originates in the corpus and moves distally. This study was undertaken to determine if a reversal in the direction of phase lag among control waves by an electronic pacemaker surgically implanted near the pylorus in dogs would reverse the sequence of contractions and hence delay gastric emptying. Electrical stimulation was applied at 5.8 to 6.0 pulses per min, 50 to 80-msec pulse width, and 10 to 14-v pulse amplitude. Liquid gastric emptying was measured by introducing 400 to 600 ml of phenol red or phenol red plus barium sulfate by a nasogastric tube through an esophagostomy into the stomach and withdrawing the remainder after 5- and 15-min periods. Solid emptying was measured by means of radiological image intensifier observation of the gastric emptying of small barium-filled balls. The study shows that an electronic pacemaker implanted in the antrum reverses the normal aborad direction of movement of contractions and delays the gastric emptying of both liquid and solid meals.     

Pyloric injection of botulinum toxin for treatment of diabetic gastroparesis

BACKGROUND: Diabetic gastroparesis is a common clinical problem. The pathophysiology includes prolonged pyloric contractions that may cause functional resistance to gastric outflow. Botulinum toxin was injected into the pyloric sphincter in an attempt to decrease pyloric resistance and improve gastric emptying. METHODS: Six patients with diabetic gastroparesis and an abnormal solid phase gastric emptying study underwent upper endoscopy during which 100 units of botulinum toxin were injected into the pyloric sphincter. Gastric emptying studies were obtained at 48 hours and 6 weeks after injection. Patients were questioned about symptoms of gastroparesis, and a symptom score was obtained at baseline and at 2 weeks and 6 weeks after injection. OBSERVATIONS: There was a mean improvement in the subjective symptom score at 2 weeks of 55% (range 14% to 80%). This improvement was maintained at 6 weeks. There was a 52% improvement in gastric emptying at 2 and 6 weeks. CONCLUSION: Pyloric injection of botulinum toxin can improve symptoms and gastric emptying in patients with diabetic gastroparesis. Further evaluation of pyloric injection of botulinum toxin as a treatment for diabetic gastroparesis is warranted.     

Effect of barium meals on gastric electromechanical activity in man

The relationship between the cutaneously recorded electrogastrogram (EGG) and gastric contractions in man is unclear. We investigated: (1) the relationship between the electrogastrogram (EGG) signals and gastric contractions elicited by barium meals and (2) the effects of barium meals on frequency and amplitude of EGG signals. As documented by fluoroscopy in four healthy subjects, barium meals stimulated three per minute gastric peristalsis which corresponded with simultaneously recorded three cycle per minute (cpm) EGG waves. Eighteen other healthy volunteers ingested 45% (w/v) or 60% barium suspensions. As determined by Fourier analysis, the dominant EGG frequency before barium was 3 cpm in 16 subjects; two subjects had no distinct frequency peaks. After barium ingestion, the mean amplitude or power at 3 cpm and 1 cpm increased, but the increase was significant only after 45% barium. In conclusion: (1) individual EGG waves after barium reflect gastric peristaltic sequences, which are reflected in increases in amplitude or power of 3 cpm EGG activity; (2) density or viscosity of the barium meal affects the gastric myoelectric response; and (3) mechanical correlates of 1 cpm EEG activity are unknown.     

Properties of the feline pyloric sphincter in vitro

The purpose of this study was to determine the intrinsic functions of the feline pylorus in vitro. The myoelectric and pressure characteristics of the intact pylorus, antrum, and duodenum, free of extrinsic hormonal or neural influences, were studied in an in vitro bath that allowed separation of the bathing medium surrounding the different bowel segments. Basal recordings revealed a zone of tonic high pressure of 28.4 +/- 3.5 mmHg (mean +/- SEM) at the pylorus. The basal slow wave frequencies in the pylorus and duodenum were 2.8 +/- 1.4 and 12.6 +/- 0.6 cycles/min, respectively. Spontaneous action potential-associated phasic contractions of the pylorus were noted in 38% of preparations. Enteric nerve stimulation with direct electric current (10 Hz, 1 ms, 10-50 V) applied proximal to the pylorus gave relaxation of the pylorus at the lower voltages and rebound excitation at higher voltages. Electrical stimulation distal to the pylorus yielded phasic contractile pyloric response during the entire stimulus. The duodenal instillation of 0.5 N HCl produced action potential-associated phasic contractions of the pylorus and duodenum but not the antrum. Pyloric responses to electrical stimulation or acidification were abolished by tetrodotoxin (10(-5) M). Bethanechol (10(-6) M) or substance P (10(-7) M) produced a contractile response at the site of stimulation but this response was not transmitted to include adjacent bowel segments. These studies suggest that the pyloric sphincter with its intrinsic reflex properties can be studied in vitro.     

Determinants of Occurrence and Volume of Transpyloric Flow During Gastric Emptying of Liquids in Dogs

The precise factors and their relative contributions that lead to individual flow pulses across the pylorus during liquid gastric emptying remain unclear. Our objective was to determine the factors leading to individual flow pulses, their relative contributions and the role of the vagus nerve in their modulation. Proximal gastric tone had a strong positive correlation with the volume of the corresponding transpyloric flow pulse whereas pyloric tone had an inverse correlation. Antral contractions were associated with the presence but not the volume of the pulse. Acute vagal blockade retarded emptying via loss of proximal gastric tone and increased outflow resistance and loss of propagating antral pressure waves. In conclusion, the major determinants of the volume of pulsatile transpyloric flow are proximal gastric and pyloric tone. The vagus nerve plays a key role in regulating both proximal gastric and pyloric tone as well as moderating propagating antral contractions.     

Reversibility of pyloric sphincter dysfunction in gastric ulcer.

To investigate both the cause and reversibility of pyloric sphincter dysfunction in patients with gastric ulcer, pyloric sphincter pressures were measured in 10 normal subjects and 13 patients with gastric ulcer before and during gastric acidification. Fasting serum gastrin concentration was significantly higher in patients with gastric ulcer than in normal subjects. Compared to normals, patients with gastric ulcer had significantly lower pyloric pressures in response to intraduodenal amino acids and sodium oleate. However, during gastric acidification, these same patients demonstrated normal pyloric responses to these stimuli. Serum gastrin concentrations did not change during gastric acidification. These studies show that: (1) in patients with gastric ulcer the pyloric sphincter does not respond normally to intraduodenal stimulation; (2) fasting serum gastrin concentration is elevated in patients with gastric ulcer; and (3) in these patients, pyloric sphincter dysfunction can be reversed by gastric acidification. The mechanism of pyloric dysfunction in patients with gastric ulcer remains unknown.     

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.     

Cholecystokinin octapeptide stimulates phasic and tonic pyloric motility in healthy humans.

Stimulation of localised pyloric contractions may be an important mechanism in the slowing of gastric emptying by cholecystokinin infusion. The effect of cholecystokinin octapeptide on fasting pyloric motility was investigated in 14 healthy volunteers. Antral, pyloric, and duodenal pressure responses to normal saline and graded injections of cholecystokinin octapeptide (5, 10, and 20 ng/kg) were measured. Injections were given double blind and in randomised order. All doses of cholecystokinin octapeptide initially stimulated (p < 0.05 cf saline) phasic pressure waves localised to the pylorus--the median number of pyloric pressure waves in the 5 minutes after injection being 0, 3.5, 6, and 7 for the saline and the 5, 10, 20 ng/kg cholecystokinin octapeptide injections respectively. The phasic pyloric motor response to 20 ng/kg cholecystokinin octapeptide injection was greater than that to 5 ng/kg (p < 0.05). Basal pyloric pressure increased after 20 ng/kg (1.0 v 0.2 mm Hg, p < 0.05 cf saline). Antral and duodenal pressure waves were suppressed initially by all doses of cholecystokinin (p < 0.05 cf saline). Subsequently, 20 of the 42 cholecystokinin octapeptide, injections but none of the saline injections, were followed by antropyloric pressure waves. Atropine, 15 micrograms/kg iv as a bolus, and then 4 micrograms/kg/hour iv as an infusion, had no effect on the stimulation of localised phasic pyloric pressure waves by cholecystokinin octapeptide 10 ng/kg. It is concluded that stimulation of pyloric contractions and suppression of antral and proximal duodenal motility may contribute to the slowing of gastric emptying produced by cholecystokinin.