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Biomedical subjects

J B Wyman

Publications and source records attributed to J B Wyman.

17 recordsLinked to original sources
PubMed1990

Control of belching by the lower oesophageal sphincter.

The mechanism that controls venting of gas from the stomach into the oesophagus was studied manometrically in 14 healthy subjects. The stomach was distended abruptly with one litre of carbon dioxide. Gas reflux was characterised by an abrupt increase in basal oesophageal body pressure to intragastric pressure. Reflux of gas from the stomach into the oesophagus occurred during transient lower oesophageal sphincter relaxations that generally had a pattern distinctly different from swallow-induced lower oesophageal sphincter relaxation. Thus, at the onset of an episode of gas reflux lower oesophageal sphincter pressure had relaxed to 3 mmHg, or less, in 96% of instances. After gas loading of the stomach the prevalence of gas reflux was significantly less when the subjects were supine (1.2/10 min) than when they were sitting (6.8/10 min) (p less than 0.001). The lower oesophageal sphincter relaxations associated with most episodes of gas reflux had a distinctive pattern that resembled those of the lower oesophageal sphincter relaxations associated with acid gastro-oesophageal reflux.

Adult↗
PubMed1989

Failure of transient lower oesophageal sphincter relaxation in response to gastric distension in patients with achalasia: evidence for neural mediation of transient lower oesophageal sphincter relaxations.

Transient lower oesophageal sphincter relaxation (LOSR) is the major mechanism underlying gastro-oesophageal reflux. The mediation and control of LOSRs are incompletely understood but evidence suggests a neural inhibitory mechanism. In this study we have evaluated the effect of gastric distension on LOS function in 16 patients with untreated idiopathic achalasia and compared it with that in 10 healthy controls. With the subjects sitting, the stomach was distended with a liquid mixture that generated 750 ml CO2. Oesophageal pH and motility were monitored for 10 minutes before and after distension. In normal controls, gastric distension induced a four-fold increase in the rate of LOSRs and gas reflux episodes (as evidenced by oesophageal common cavities), whereas this response was absent in the achalasia patients. Basal LOS pressure did not change in either group. These findings are consistent with the notion that transient LOSRs induced by gastric distension are neurally mediated, probably by the same inhibitory nerves that govern swallow mediated LOS relaxation.

Adolescent↗
PubMed1988

Adenomatous and hyperplastic polyps cannot be reliably distinguished by their appearance through the fiberoptic sigmoidoscope.

This prospective study is designed to determine if experienced sigmoidoscopists can, from gross appearance, differentiate adenomas and hyperplastic polyps. Six hundred eleven polyps discovered at fiberoptic sigmoidoscopy were removed completely or biopsied for histologic examination. The polyp's size, distance from the anal verge, color, and the endoscopist's diagnosis were analyzed. Hyperplastic polyps were significantly smaller, of lighter color, and located closer to the anus than adenomas. The sensitivity of the endoscopic diagnosis for adenomas is 0.80 and the specificity 0.71. We conclude the endoscopic diagnosis of polyps 1.0 cm and smaller is not accurate enough for decision making, and these should be biopsied to guide management. Since 97% of polyps larger than 1.0 cm are adenomas, their removal can be advised without biopsy.

Adenoma↗
PubMed1986

Upper esophageal sphincter function during belching.

We studied the mechanism of belching with specific attention to the upper esophageal sphincter (UES) in 14 normal volunteers. Belching occurred by the following sequence of events: lower esophageal sphincter relaxation; gastroesophageal gas reflux, recorded manometrically as a gastroesophageal common cavity phenomenon; UES relaxation; esophagopharyngeal gas reflux; and restoration of intraesophageal pressure to baseline by a peristaltic contraction. Upper esophageal sphincter relaxations comparable to those associated with belches were induced by abrupt esophageal distention with air boluses. In contrast, fluid boluses injected into the midesophageal body either had no effect on UES pressure or increased UES pressure. Thus, the UES responded to esophageal body distention in two distinct ways: abrupt relaxation in response to air boluses and pressure augmentation in response to fluid boluses. Mucosal anesthesia did not alter the UES response to esophageal boluses of gas or liquid thereby making it unlikely that these substances are differentiated by a mucosal receptor. Rapid distention of the proximal esophagus with a cylindrical balloon (15 cm long) elicited UES relaxation. These findings suggest that the rapidity and spatial pattern of esophageal distention, rather than discrimination of the type of material causing the distention, determines whether or not UES relaxation occurs.

Adult↗
PubMed1980

The vomiting patient.

The causes of vomiting can be grouped into two categories, corresponding to the neural sites of emetogenesis--the emesis center (EC) and the chemoreceptor trigger zone (CTZ). Anatomic disorders induce vomiting via the EC, whereas toxic and metabolic problems do so via activity of the CTZ. Antihistamines have antiemetic effects at the EC; phenothiazines and related compounds block vomiting mediated by the CTZ. Thus, a pharmacologic approach to this problem can be logically constructed.

Antiemetics↗
PubMed1978

Variability of colonic function in healthy subjects.

Twenty healthy subjects eating normal diets made repeated five-day stool collections, the 10 females making their collections in four to six successive weeks. In most subjects there were striking variations in transit time, measured by Hinton's method. The variability of average faecal wet and dry weight, faecal volume, and the frequency of defaecation was equally great, suggesting that the transit time variations were genuine. The size of individual stools varied even more, often tenfold or more. Faecal water content was relatively constant. There were no significant differences between males and females, and in the females there were no obvious changes related to the phases of the menstrual cycle. The normal variability of colonic function should be taken into account in planning experiments and in interpreting existing data.

Adolescent↗
PubMed1976

How trustworthy are bowel histories? Comparison of recalled and recorded information.

One hundred and fifty hospital outpatients were questioned about their bowel habits and then asked to record these in diary booklets for two weeks. Overall, recalled and recorded figures for frequency of defecation agreed fairly closely, but in 16% of patients there was a discrepancy of three or more bowel actions per week. This was usually an exaggeration of the difference from the norm of one a day. Patients were bad at predicting episodes of changed bowel frequency. These findings cast doubt on the value of population surveys of bowel habit based solely on questionnaires. They also suggest that the irritable bowel syndrome might be correctly diagnosed more often if patients were routinely asked to record their bowel actions.

Adult↗
PubMed1976

The effect on intestinal transit and the feces of raw and cooked bran in different doses.

Ten healthy male subjects on a low fiber diet were given two doses of raw wheat bran (12 and 20 g/day) and two doses of cooked bran (13.2 and 22 g/day). Both doses of raw bran increased fecal dry weight but only the higher dose decreased transit time and increased stool volume. Individual stool size was increased only by raw bran 12g/day. Neither bran influenced fecal wet weight or stool frequency. This study suggests that the cereal manufacturing process alters wheat bran so that cooked bran has less effect on the intestine than does a comparable amount of raw bran.

Adult↗
PubMedDate not supplied

The significance of diminutive colonic polyps found at flexible sigmoidoscopy.

In order to determine the importance of identification and follow-up of diminutive colonic polyps (DCPs) (i.e., those less than or equal to 5 mm in diameter), we studied 3006 patients undergoing flexible sigmoidoscopy. DCPs were found in 315 patients (10.5%). Biopsy of these lesions showed them to be nonneoplastic in 187 patients (59.4%) and neoplastic in 128 (40.6%). Overall, 35% of all DCPs found were neoplastic. Gross appearance of the lesions was found to be an unreliable means of predicting their histologic makeup. Of the 128 patients with neoplastic DCPs, 73 underwent further examination with barium enema and colonoscopy. Synchronous lesions were found in 57.5%. In 10 patients, synchronous lesions were of significance, including carcinomas, adenomas greater than or equal to 8 mm in diameter, or severely dysplastic adenomas. We conclude that all DCPs discovered at sigmoidoscopy should be biopsied and in patients in whom DCPs are found to be neoplastic, colonoscopy should be undertaken to search for proximal synchronous lesions.

Adenoma↗
PubMedDate not supplied

Barium enema versus colonoscopy for patients with polyps found during flexible sigmoidoscopy.

This prospective study compares the accuracy of barium enema examination performed by experienced radiologists to colonoscopy performed by experienced gastroenterologists blinded to the radiographic findings to detect proximal, synchronous lesions in patients with polyps detected during fiberoptic sigmoidoscopy. Three thousand six patients were examined, of whom 147 (5%) had polyps larger than 0.5 cm in diameter. Of 114 patients who completed the protocol, 46 patients (40%) had synchronous, proximal colonic lesions. There were no radiographic false positives, but the single-contrast barium enema missed polyps in 13 while detecting polyps in 2 patients (sensitivity = 13%). The double-contrast barium enema missed proximal polyps in 23 patients while detecting them in 8 (sensitivity = 26%). We conclude that patients with neoplastic polyps found during fiberoptic sigmoidoscopy should have colonoscopy without barium enema. If the entire colon cannot be examined at colonoscopy, we advise double-contrast barium enema.

Adenocarcinoma↗