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Biomedical subjects

J H Bond

Publications and source records attributed to J H Bond.

At least 91 records · Page 5Linked to original sources
PubMed1980

Effect of glucagon on gastrointestinal blood flow of dogs in hypovolemic shock.

A microsphere technique was used to study the effect of glucagon on blood flow to the different tissue layers of the stomach, small bowel, and colon of the dog in hypovolemic shock. In normal dogs, glucagon caused a twofold rise in flow to all layers of the stomach and colon, and a threefold increase to all layers of the small bowel. After administration of glucagon, a larger fraction of cardiac output was diverted to the gut microcirculation. In acute hypovolemic shock, intestinal perfusion was preserved relative to cardiac output inasmuch as cardiac output and gastric blood flow fell 75% and flow to the small bowel and colon fell by only about 50%. Glucagon markedly increased the fraction of cardiac output passing to the gut circulation in hypovolemic shock and, most importantly, sustained flow to the areas most prone to ischemic necrosis; gastric mucosa, colonic mucosa, and small intestinal villi. In more prolonged shock, however, glucagon precipitated fatal cardiovascular collapse unless part of the lost blood volume first was replaced. Glucagon, therefore, should not be used in patients in hypovolemic shock without prior replacement of at least part of the lost blood volume.

Animals↗
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↗
PubMed1980

Colonic conservation of malabsorbed carbohydrate.

[14C]Sucrose absorption was studied in 4 healthy controls and 4 patients after jejunoileal bypass using an ileal perfusion technique which made it possible to distinguish 14C-absorption in the small bowel from that occurring in the colon. Healthy controls failed to absorb 2--4% of a 50-g dose of [14C]sucrose in the small bowel; however, virtually none of the [14C] appeared in feces in a dialyzable form with appreciable osmotic activity. In bypass patients, the small bowel failed to absorb 29--84% of the 50-g dose of [14C]sucrose. Approximately two-thirds of the nonabsorbed [14C] was in the form of sucrose and the remainder was nearly all present as monosaccharides. A mean of only 42% of the [14C] Not absorbed in the small bowel appeared in the feces and only about one-third of this fecal [14C] was in a dialyzable form with appreciable osmotic activity. Thus, the colon plays an important role in carbohydrate malabsorption by salvaging carbohydrate and reducing osmotic activity of the nonabsorbed sugar. This conlonic function appears to depend upon bacterial metabolism of the carbohydrate, and individual variations in diarrhea and weight loss associated with carbohydrate malabsorption could reflect individual differences in the bacterial flora of the colon.

Adult↗
PubMed1980

The effect of anesthesia and laparotomy on blood flow to the stomach, small bowel, and colon of the dog.

The effect of anesthesia and laparotomy on the distribution of blood flow to the different tissue layers of the stomach, small bowel, and colon of the dog was studied using a double-isotope, microsphere technique. In conscious dogs total jejunal flow significantly exceeded both ileal and colonic flow. Mucosal flow comprised about two thirds of total gastric and small bowel flow, but less than half of colonic flow. Fifteen minutes after induction of anesthesia, there was a marked increase in flow to all levels of the alimentary tract, as well as to each tissue layer. This increase was transient, since by 1 hour flow to all gut levels had decreased nearly to baseline levels. Laparotomy per se did not significantly alter blood flow to the full thickness or mucosal layer of either stomach, small bowel, or colon. These findings indicate that future studies of gut function or blood flow should be performed in conscious animals or in anesthetized animals only after complete cardiovascular stabilization. Neither laparotomy nor anesthesia caused a redistrubtion of flow away from the mucosal layers, and hence the observation that patients have often stopped bleeding at the time of operation for uncontrolled hemorrhage is unexplained.

Anesthesia, General↗
PubMed1979

Use of microspheres to measure small intestinal villus blood flow in the dog.

The accuracy of using 7- to 10-micron microspheres to measure blood flow to dog small intestinal villi was studied. These spheres appear to pass unimpeded through the afferent arterioles of the villus and lodge at the villus tip because 1) virtually all villus spheres were located at the tip, 2) flow determined by visually counting spheres did not differ significantly from flow determined from radioactivity of the sheared-off villus layer, 3) the size distribution of spheres in the villus and subvillus layers was virtually identical to that administered, indicating no premature impaction of the larger spheres, and 4) spheres lodging in the submucosa during vasoconstriction did not subsequently migrate to the villi during vasodilatation. Studies with 25-micron spheres indicated that 28% of the 7- to 10-micron spheres shunted through vessels greater than 10 micron. Double isotope studies showed that lodges spheres do not migrate and that the injection of 2--4 X 10(6) spheres does not alter villus flow. Thus, 7- to 10-micron microspheres pass to and lodge in villus vessels in proportion to capillary flow and should provide an accurate estimate of villus nutrient blood flow.

Animals↗
PubMed1978

Effect of dietary fiber on intestinal gas production and small bowel transit time in man.

The influence of dietary fiber on intestinal gas production and on small bowel transit time was studied in eight healthy subjects using breath H2 excretion as an indicator of colonic gas production. Hydrogen excretion following ingestion of bran was substantially less than that following ingestion of lactulose, a nonabsorbable fermentable sugar. Likewise, human fecal homogenates produced only about 10% as much H2 and CO2 during incubation with bran as with glucose or lactulose. Thus, the polysaccharides in bran appear to be relatively poor substrate for colonic bacterial gas production, and reported gas-related symptoms after bran ingestion may be due to some other mechanism. The small bowel transit time of bran was greater than that of lactulose; however, addition of bran to lactulose did not slow lactulose transit.

Breath Tests↗
PubMed1978

Influence of high luminal PO2 on the anaerobic bacteria of the rat colon.

The influence of high luminal PO2 on colonic anaerobes was investigated by chronically perfusing the colon of unrestrained rats with O2 or N2. A luminal PO2 of approximately 700 mm Hg did not significantly influence the fecal concentration of total anaerobes recovered on rabbit blood agar or of Bifidobacterium sp. and Bacteroides sp. recovered on selective media. However, the O2 infusion reduced the rat's excretion of CH4 (a metabolic product of anaerobic bacteria) to about 5% of the control value, although the feces of O2-treated rats produced CH4 normally. This study suggests that the production of metabolites by the colonic bacteria may sometimes be more accurately studied in situ rather than in culture. Measurement of volatile bacterial metabolites in breath may provide a simple means of studying the in situ metabolism of a variety of colonic bacteria in man.

Actinomycetales↗
PubMed1977

Quantitation of countercurrent exchange during passive absorption from the dog small intestine: evidence for marked species differences in the efficiency of exchange.

The present investigation was designed to quantitatively assess the possible influence of countercurrent exchange on passive absorption from the small intestine of the dog. Villus blood flow was measured with a modification of the microsphere method. Simultaneously, the absorption from the gut lumen of five diffusible gases (H2, He, CH4, 133Xe, and CO) was determined. Villus blood flow averaged 0.247 +/- 0.03 (SEM) ml/min per g. The observed absorption of H2, He, CH4, and 133Xe was only 16.2 +/- 1.8, 12.8 +/- 2.3, 12.0 +/- 1.8, and 15.8 +/- 1.4 %, respectively, of what this villus blood flow could carry away if it reached perfect equilibrium with the luminal gases. This low absorption rate could result from diffusion limitation to absorption or countercurrent exchange. The diffusive permeability of the barrier seperating the luminal gases and villus blood flow was assessed by measuring the absorption rate of CO. Because absorbed CO binds tightly to hemoglobin, it cannot exchange, and when present in low concentrations its uptake is entirely diffusion limited. Knowledge of the diffusion rate through tissue of the unbound gases relative to that of CO made it possible to calculate the degree to which each of the unbound gases should equilibrate with villus tip blood. The percentage equilibration between lumen and blood at the villus tip for H2, He, CH4, and 133Xe was 99.7, 99.9, 75.6, and 36.0% , respectively. Each of these values greatly exceeded the percentage equilibration of blood leaving the villus (calculated from the observed absorption rate and villus blood flow) and indicated an exchange of 83.8, 87.2, 84.1, and 56.1% of initially absorbed H2, He, CH4, and 133Xe. This result is in accord with theoretical calculations which suggest that countercurrent exchange should be exceedingly efficient in the dog. The striking effect of countercurrent exchange on passive absorption in the dog differs from our previous studies in the rabbit where no exchange was demonstrated. This marked species difference may result from anatomical differences in villus architecture. The dog has long, densely packed villi while the rabbit has broad, widely spaced villi. In the dog, only the villus tips may equilibrate with the lumen, hence a countercurrent gradient may be established in the villus. The entire villus of the rabbit may equilibrate with the lumen and no gradient for countercurrent exchange can therefore be established.

Animals↗
PubMed1977

Use of breath hydrogen (H2) to quantitate small bowel transit time following partial gastrectomy.

The relation between small intestinal transit time and postgastrectomy diarrhea was investigated with a technique which employs the measurement of pulmonary H2 excretion after ingestion of the nonabsorbable sugar, lactulose. Ten postgastrectomy patients with persistent diarrhea had an average small bowel transit time of 35.2 +/- 3 min (S.E.M.), which was significantly (p less than 0.05) shorter than either that of 10 patients without diarrhea (74.6 +/- 5 min) or 40 healthy controls (72.6 +/- 5 min). These decreased transit times appeared to be due to rapid gastric emptying rather than to a primary intestinal abnormality, since the transit of lactulose instilled directly into the jejunum was equally rapid in patients and controls. All postgastrectomy patients with diarrhea failed to absorb a portion of a 100 gm dose of glucose (quantitated by pulmonary H2 measurements), but all patients without diarrhea and 10 healthy control subjects absorbed the entire dose. Constant perfusion studies of the terminal ileum in two patients indicated that glucose absorption was least efficient from the most rapidly moving front of the ingested bolus of glucose. These studies suggest that the diarrhea observed in some postgastrectomy patients is, in part, the result of malabsorption of carbohydrate due to excessively rapid small bowel transit which is secondary to rapid gastric emptying.

Breath Tests↗
PubMed1976

Multiple antibiotic resistance in clinical strains of Neisseria gonorrhoeae isolated in South Carolina.

Minimal inhibitory concentration (MIC) values for penicillin G, tetracycline, amoxicillin, and actinomycin D were determined for 81 strains of Neisseria gonorrhoeae isolated from patients attending public health clinics in the Piedmont region of South Carolina. Gonococcal isolates were also screened for highlevel resistance to streptomycin. Significant positive correlations (r >/= 0.45, P </= 0.01) were found between all possible pairs of the antibiotics penicillin G, tetracycline, and amoxicillin. The MIC values of actinomycin D showed no significant positive correlations with the MIC values of the other antibiotics. Gonococcal strains that were resistant to streptomycin tended to be resistant to penicillin G, tetracycline, and amoxicillin. Of the 81 isolates, 18.5% were multiply resistant to penicillin G, tetracycline, amoxicillin, and streptomycin. Spontaneous mutants with reduced antibiotic susceptibility, selected for decreased susceptibility to penicillin G, displayed small decreases in susceptibility to tetracycline, amoxicillin, and actinomycin D. Spontaneous mutants selected for decreased susceptibility to actinomycin D displayed small losses in susceptibility to penicillin G. The results show that multiple antibiotic resistance occurs in clinically isolated gonococcal strains in South Carolina. The results further suggest the presence of a common genetic mechanism determining antibiotic resistance in N. gonorrhoeae.

Anti-Bacterial Agents↗
PubMed1976

Intestinal villus blood flow measured with carbon monoxide and microspheres.

The purpose of the present study was to compare the small intestinal blood flow that equilibrates with luminal CO (FLco) with simultaneous determinations of villus blood flow measured by a recent modification of the microsphere technique. These studies, carried out in rabbits, showed that FLco closely correlated (r = 0.83) with villus flow measured with microspheres over a three-fold range of flows, and the mean rate of flow to the villi by both techniques was about 0.08 ml/min X g of intestine. Thus, FLco appears to be a measure of villus blood flow. Based on previous studies of inert gas uptake from the rabbit small intestine, it appears that absorption of readily diffusible substances in the rabbit can be represented by a simple two-component model: a flow-limited component in which substances equilibrate with villus blood flow and are carried away without subsequent countercurrent exchange, and a diffusion-limited component which presumably represents uptake by the blood flow of the crypt region or submucosa.

Animals↗