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Biomedical subjects

J H Bond

Publications and source records attributed to J H Bond.

At least 19 recordsLinked to original sources
PubMed1992

The National Polyp Study. Design, methods, and characteristics of patients with newly diagnosed polyps. The National Polyp Study Workgroup.

The National Polyp Study (NPS) is a multicenter prospective randomized trial designed to evaluate follow-up surveillance strategies in patients who have undergone polypectomy for the control of large bowel cancer. The study design was developed by a joint research committee from American Gastroenterological Association, the American Society for Gastrointestinal Endoscopy, and the American College of Gastroenterology. Subjects who met the eligibility criteria were randomized into two different treatment arms. Eligibility criteria included: removal of one or more adenomas; complete colonoscopy; no prior polypectomy, inflammatory bowel disease, or familial polyposis; and no history of colon cancer. The treatment arms consisted of a frequent follow-up (1 and 3 years after initial polypectomy) and a less frequent follow-up (3 years). Follow-up examinations included fecal occult blood tests, air-contrast barium enema, and colonoscopy. The latter was done on 9112 referred patients at the seven participating centers from November 1980 until February 1990 who had no history of polypectomy, colon cancer, familial polyposis, or inflammatory bowel disease. Of these patients, 4763 (52.3%) had no polyps; 549 (6.0%) had an invasive cancer; 776 (8.5%) had nonadenomatous polyps; 208 (2.3%) had incomplete examinations; 184 (2.0%) had other findings; and 2632 (28.9%) had one or more adenomas, of which 1418 (53.9%) were randomized to one of the two treatment arms. This article reports the background, rationale, objectives, methods, and organization of this study and includes patient characteristics on initial presentation. Future data provided by the NPS may help in the development of recommendations for surveillance guidelines for such patients. This study also provides a framework to address questions regarding the natural history of adenomas and their relationship with colorectal cancer.

Adenoma↗
PubMed1989

Sensitivity, specificity, and positive predictivity of the Hemoccult test in screening for colorectal cancers. The University of Minnesota's Colon Cancer Control Study.

Data are presented on the sensitivity, specificity, and positive predictivity of the Hemoccult test based on the experience of the Minnesota Colon Cancer Control Study, a randomized clinical trial to determine whether the use of the Hemoccult test can reduce mortality from colorectal cancer. Rehydrating the slides with a drop of water before processing resulted in an increase in positivity (2.4% to 9.8%), and sensitivity (80.8% to 92.2%) but a decrease in specificity (97.7% to 90.4%) and positive predictivity (5.6% to 2.2%). The effects of age and sex were also evaluated. The test was less specific for men than women (p = 0.03). Specificity was highest for those less than 60 yr of age and decreased with increasing age (p = 0.05). The positive predictivity increased with age from 1.6% for those under 60 yr to 3.6% for those over 70 yr (p = 0.0004).

Age Factors↗
PubMed1987

Quantitative assessment of luminal stirring in the perfused small intestine of the rat.

We measured the resistance (RL) to CO absorption that resulted from poor luminal stirring in the constantly perfused rat jejunum. RL or calculated unstirred layer thickness was greater for 30-cm than 10-cm long segments, indicating lack of a uniform thickness of unstirred layer. The possibility that laminar flow existed in the gut was first tested by calculating expected CO absorptions from fluid moving with laminar flow. These values agreed closely with observed absorption rates. Laminar flow also was supported by the observation that CO absorption was independent of perfusate viscosity. Lastly, after sudden addition of phenolsulfonphthalein (PSP) to the perfusate, PSP outflow concentration was similar in tygon tubing (which has laminar flow) and a gut segment of comparable dimension. We conclude that flow in the perfused gut is laminar and that this laminar flow has many implications for studies carried out with the constant-perfusion technique.

Animals↗
PubMed1986

Pills in the colon.

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Administration, Oral↗
PubMed1984

Use of carbon monoxide to measure luminal stirring in the rat gut.

We used carbon monoxide (CO) as a probe to quantitatively measure intestinal unstirred water layers in vivo. CO has several features that make it uniquely well suited to measure the unstirred layer in that its tight binding to hemoglobin makes uptake diffusion limited, and its relatively high lipid solubility renders membrane resistance negligible relative to the water barriers of the unstirred layer and epithelial cell. The unique application of CO was the measurement of the absorption rate of CO both from the gas phase as well as a solute dissolved in saline. Several lines of evidence showed that a gut stripped free of saline and then filled with gas contained a negligible unstirred layer. Thus, absorption of CO from the gas phase measured resistance of just the epithelial cell. Subtraction of this value from the resistance of CO absorption from saline provided a direct measure of unstirred layer resistance. Studies in the rat showed for a 3-min absorption period that the conventionally calculated apparent unstirred layer for the jejunum was 411 micron and for the colon was 240 micron. However, this conventionally calculated unstirred layer resistance did not truly depict the situation in the rat gut, since there was a continuing depletion of CO from outer surfaces of luminal contents throughout the experiment period. This produced a continually increasing diffusion barrier with time. Calculation of expected absorption rate from unstirred cylinders with the dimensions of the rat gut indicated that there was virtually no stirring in the small intestine and minimal stirring in the colon. The technique described in this paper appears to be simpler and to require fewer assumptions for validity than other techniques previously used to measure unstirred layers in vivo.

Animals↗
PubMed1984

Gastrointestinal transit in thyroid disease.

Diarrhea and malabsorption are common manifestations of hyperthyroidism, whereas constipation or obstipation frequently occur in hypothyroidism. Abnormalities of gastrointestinal motility have been proposed as the primary cause of these complaints, but documentation has been conflicting and largely limited to observations of the transit time of a barium meal. We studied gastrointestinal transit time in fasting patients with thyroid dysfunction using the pulmonary excretion of H2 after the ingestion of a nonabsorbable carbohydrate, lactulose, as an indicator of the rate of transit to the colon. Mean transit time of 10 hyperthyroid patients (29 +/- 4.0 min) was significantly less than that of 42 healthy controls (72 +/- 3.7 min, p less than 0.001), and of 6 hyperthyroid patients when they became hypothyroid after treatment (80 +/- 11.0 min, p less than 0.05). Transit time decreased significantly when hypothyroid patients were given thyroid replacement (p less than 0.01). These findings support the hypothesis that abnormal gut motility may be the primary cause of the diarrhea and malabsorption of hyperthyroidism, and the constipation and obstipation commonly seen in hypothyroidism.

Adult↗
PubMed1982

Office-based management of diarrhea.

Diarrhea of unknown cause is a particularly challenging diagnostic problem as it may be trivial and self-limiting or the presenting symptom of a life-threatening disorder. Antibiotic-associated diarrhea is a frequent complication of antimicrobial therapy, especially in the elderly. The more severe form, pseudomembranous colitis, is now known to be caused by a toxin produced in the colon by Clostridium difficile.

Acute Disease↗
PubMed1982

Effects of liver congestion on hepatic drug metabolism in the rat.

Pharmacokinetic alterations in drug disposition have been demonstrated for a variety of hepatic disease states, but there is little information concerning the effects of elevated hepatic venous pressure on hepatic drug metabolism. A rat model of hepatic congestion which was characterized by significantly elevated hepatic venous pressure, marked prolongation of prothrombin time, reduced total hepatic blood flow and histological changes of marked pericentral fibrosis and central vein dilation was used to study the effects of liver congestion on hepatic microsomal biotransformation and in vivo disposition of morphine and pentobarbital. No significant differences in levels of microsomal cytochrome P-450 or NADPH-dependent cytochrome c reductase were seen between the two groups. Total hepatic microsomal capacity for glucuronidation of morphine and hydroxylation of pentobarbital was not altered by elevated hepatic vein pressure and no change in in vivo systemic clearance was seen for either drug in response to hepatic venous congestion. These animal data demonstrate that hepatic congestion produces minimal alterations in hepatic metabolism of morphine and pentobarbital and may not have the severe detrimental effects on drug biotransformation and disposition which would be predicted.

Animals↗
PubMed1982

Metabolism of carbon monoxide by the colonic flora of humans.

The metabolism of carbon monoxide by the colonic flora was investigated using human fecal homogenates. During anaerobic incubation, these homogenates rapidly consumed added carbon monoxide reducing the PCO level to a minimum of about 0.2 ppm. In the presence of glucose, carbon monoxide consumption averaged about 0.7 ml/h . g feces and without glucose about 0.2 ml/h . g feces. This consumption was not observed if the homogenates were autoclaved, passed through a bacterial filter, or cultured aerobically, indicating that the carbon monoxide was removed by the metabolism of fecal anaerobes. Aerobic incubation of fecal homogenates resulted in slow but definite release of carbon monoxide. While bacterial carbon monoxide consumption probably does not play an appreciable role in the turnover of carbon monoxide that is inhaled or exogenously produced, it is possible that carbon monoxide uptake by colonic flora protects other fecal organisms and possibly the host from carbon monoxide liberated in the gut.

Aerobiosis↗
PubMed1980

Milk intolerance in Manitoba Indian school children.

The breath H2 test was used to determine the prevalence of milk intolerance in Indian schoolchildren, 5 to 19 years old. One hundred four children were randomly assigned to one of six groups: 1) reconstituted skimmed milk powder (SMP); 2) SMP and sandwich; 3) SMP and lactase; 4) diluted (1:1) evaporated whole milk (EM); 5) EM and sandwich; and 6) EM and lactase. Samples of expired air were collected 2 hr after ingestion of 245 ml of milk. Five children had H2 levels suggestive of appreciable lactose malabsorption; two had symptoms. The mean H2 excretion levels of the subjects on SMP were significantly higher than those on EM. The group on SMP alone excreted significantly more H2 than any other group except those receiving SMP and a sandwich. The relatively low prevalence of milk intolerance in this populatin group should not preclude continuation and promotion of milk programs in their schools. However, preference should be given to the use of EM rather than SMP. The needs of children who cannot hydrolyze lactose must also be considered in the planning of food supplement programs.

Adolescent↗
PubMed1980

Flatulence.

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Carbon Dioxide↗
PubMed1980

Use of a model of small bowel mucosa to predict passive absorption.

The purpose of this study was to determine if the observed rate of passive absorption of inert gases from the canine small bowel could be predicted by the use of an anatomical model of the mucosa and measurements of villus blood flow and the diffusive barrier to absorption. Villus blood flow was measured with microspheres and the diffusive barrier separating bulk luminal contents and blood was estimated from CO absorption. The model predicts initial uptake of the inert gases (H2, He, CH4, and 133Xe) in blood at the villus tip, subsequent countercurrent exchange in the villus, and longitudinal diffusion of the gases down the villus to a subvillus blood flow. Observed absorption rates for each of these four gases were reasonably accurately predicted by the model at both basal villus blood flow and at low villus blood flow induced by hypotension. We suggest that this model can be used to predict passive absorption kinetics over a range of villus blood flows and to predict the influence of a variety of parameters on the rate of passive absorption of diffusible substances.

Animals↗