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Biomedical subjects

R W Summers

Publications and source records attributed to R W Summers.

At least 73 records · Page 4Linked to original sources

Effects of intestinal secretagogues and distension on small bowel myoelectric activity in fasted and fed conscious dogs.

1. Defined jejunal segments were perfused with solutions of bile salts and of ricinoleic acid during fasting and after feeding in two groups of conscious dogs, one with the segment in continuity, and the other with a Thirty-Vella loop. Myoelectric activity was recorded from chronically implanted electrodes on the jejunal segment and also from the proximal and distal in situ bowel.2. The results in both groups were identical. During fasting, migrating complexes were present in the segment, but were replaced by intermittent spike activity during chenodeoxycholate without and with ricinoleic acid perfusion. After food, when migrating complexes were replaced by intermittent spike activity, none of the solutions produced any consistent effect.3. In fasted animals, low levels of distension (15 mmHg) interrupted the migrating complexes in the segment and induced intermittent spike activity which was similar to that seen with the secretagogues. The migrating complexes in the main bowel continued during distension. In fed animals, spike activity increased in the segment during distension at 25 mmHg and decreased in the main bowel. In both groups, distension of the segment to pressures between 37.5 and 50 mmHg abolished spike activity both in the distended segment and the main bowel in fasted and fed states, and, in fasted dogs, migrating complexes were also abolished.4. These results demonstrate that the inhibitory intestino-intestinal reflex is mediated through extrinsic nerves and does not require an intact myenteric plexus, whereas the altered myoelectric activity induced by secretagogues is a local effect and does not spread to adjacent bowel through either intrinsic or extrinsic neural pathways. It seems likely that the local motor effect of secretagogues is a result of net secretion, producing distension to pressures below the threshold required to activate the intestino-intestinal reflex.

Action Potentials↗

Patterns of spike burst spread and flow in the canine small intestine.

We are describing a new method to illustrate the spread of spike bursts along the small intestine. Spike bursts migrate aborally in the longitudinal axis (from distances up to 30 to 40 cm at the same rate as slow waves). These were detected through the use of multiple closely and evenly spaced serosal electrodes in conscious dogs. Their occurrence is plotted with respect to electrode and time using a computer and printer. Patterns of contractile activity after fasting and feeding are illustrated. Outflow from an intraluminal cannula occurs in pulses preceded by spike burst activity in electrodes proximal to the cannula. This lends support to the concept that intestinal flow is accomplished by migrating ring contractions.

Animals↗

Modulation of jejunal flow by solutions of varying osmolality and acidity in the intact canine jejunum.

Because gastric emptying is modulated by the osmolality or hydrogen ion concentration of intraduodenal solutions, we hypothesized that similar mechanisms exist to regulate flow within the small intestine and that the altered flow is associated with changes in intestinal motility. Sodium chloride solutions with higher and lower osmolality than plasma and both isotonic and hypotonic hydrochloric acid solutions flowed more slowly into segments of jejunum in conscious dogs than isotonic neutral salt solutions. The altered flow was associated with increased frequency of spike bursts in the segment with the salt solutions of varied osmolality, but with only increased force of contractions with both isotonic and hypotonic acid solutions. Some evidence exists to suggest that the changes in motility are mediated by a neural mechanism. If similar mechanisms exist in the duodenum, they may play a role in the regulation of gastric emptying.

Action Potentials↗

Severe abdominal vasculitis with hepatitis B antigenemia.

Two cases of necrotizing abdominal vasculitis associated with hepatitis B are reported. The diagnosis of mesenteric vasculitis is often delayed, and intestinal perforation is common. Early recognition of the disease and early treatment with corticosteroid and immunosuppressive drugs may alter the course of the disease. Preoperative diagnosis is best made by mesenteric arteriography and rectal biopsy.

Abdomen↗

Longitudinal and circumferential spread of spike bursts in canine jejunum in vivo.

This study demonstrates a new method for quantitatively analyzing individual intestinal spike bursts and establishes the distribution of spike burst spread under conditions of fasting and feeding in conscious healthy dogs. The dimensions and propagation lengths of individual jejunal spike bursts were determined by studying spike burst spread within slow-wave cycles. Electromyograms were recorded simultaneously from multiple closely spaced serosal electrodes in the jejunum (4 equally distant around the circumference and 16 along the long axis at 3-cm intervals). At least 75% of the time, spike bursts involved the entire cross-sectional circumference simultaneously. Greater than 50% of spike bursts during fasting or feeding spread distally 3-30 cm. The remainder were isolated or segmental spike bursts involving < 3 cm of jejunum. The lengths of propagative spike bursts increased with the time during phase II and reached a maximum of 30-40 cm during phase III. Fed activity showed a mixture of segmental and longer propagative spike bursts that varied little with time after feeding. Propagative spike bursts > 3 cm in length produced at least 85% of the total myoelectric burst activity regardless of the state of fasting or feeding and constitute the major form of intestinal motility in the canine jejunum.

Animals↗

Cephalosporin-associated colitis and Clostridium difficile.

A case of cephalosporin-associated colitis occurred in which a tissue-cultured morphologic-altering activity was demonstrated in the patient's feces during the active episode. Neutralization of the tissue culture activity by antiserum directed against a partially purified toxin of Clostridium difficile provided a more suggestive link between the colitis and this clostridial species.

Aged↗

Long-term cimetidine and anticholinergic therapy in patients with gastrinoma.

Two patients with gastrinomas were treated with cimetidine and an anticholinergic drug for greater than 20 months after exploratory laparotomy disclosed no solitary resectable tumor. Both have done well, and thus this therapy is recommended as a safe and effective alternative to total gastrectomy in reliable patients. Additional therapeutic methods are needed to control tumor growth.

Administration, Oral↗

National Cooperative Crohn's Disease Study: study design and conduct of the study.

The design and execution of the National Cooperative Crohn's Disease Study are described in this paper. The Study incorporated several noteworthy features developed to meet specific demands of the disease and its therapy. A standard clinical grading system, the Crohn's Disease Activity Index (CDAI) was developed to allow uniform decentralized clinical evaluation and decision-making throughout the 5 yr of the study. All three drugs in widespread clinical use in Crohn's disease were studied both for suppressive and prophylactic efficacy and for toxicity. The study employed a scheme for double-blind evaluation of patient progress which allowed adjustment of prednisone dose according to the degree of illness and ensured continuous monitoring for serious toxicity of any study drug. Results were analyzed primarily by ranking the clinical outcome of every patient according to a uniform and detailed scheme and applying Wilcoxon nonparametric statistics. Outcome was also analyzed by life-table methods. Eleven hundred nineteen patients were entered and 604 patients were randomized at 14 study centers during the 5-yr duration of the study. Twenty patients were eliminated from analysis as not meeting diagnostic criteria for Crohn's disease, and another 15 patients were eliminated as not meeting other preestablished criteria for analysis. Nine percent of randomized patients, equally distributed in the four treatment groups, withdrew as noncompliant. Ninety percent of patients completed all or all but one protocol-specified visits, and 95% completed the final radiologic and sigmoidoscopic evaluation.

Azathioprine↗

National Cooperative Crohn's Disease Study: results of drug treatment.

The response of active and quiescent Crohn's disease to prednisone, sulfasalazine, or azathioprine has been studied in 569 patients in a placebo-controlled, randomized, multicenter cooperative trial. The response of active symptomatic disease to prednisone or sulfasalazine was significantly better than to placebo. Response to azathioprine was better than to placebo, but the difference did not reach conventional levels of statistical significance. Patients with colonic involvement were especially responsive to sulfasalazine, and those with small bowel involvement were especially responsive to prednisone. Patients' drug therapy immediately before entry to the study significantly affected subsequent response. For patients with quiescent disease, none of the drugs was superior to placebo in prophylaxis against flare-up or recurrence. There is less than a 5% risk that a clinically significant prophylactic effect of any of the drug regimens was missed.

Adult↗

A trial of sulfasalazine as adjunctive therapy in Crohn's disease.

The effect of the combination of sulfasalazine and prednisone has been compared with that of prednisone and placebo in 89 actively symptomatic patients with Crohn's disease in a double-blind, randomized, multicenter controlled trial. The combination was less effective than prednisone alone in treatment of active symptomatic disease. The probability of obtaining this result, if sulfasalazine truly has a clinically useful effect equal to or greater than that specified in the calculation, is less than 1%. Patients who were in remission at the end of 8 wk were rerandomized to receive either the two drugs together or prednisone plus placebo while repeated systematic attempts to withdraw prednisone were made over the next 6 mo. Sulfasalazine showed no prednisone-sparing effect as judged either by outcome ranking or total dose of prednisone consmed by the two treatment groups. However, in this comparison the probability is greater than 5% that, given the results observed, a clinically useful effect of sulfasalazine of specified minimum degree truly exists. It was possible to withdraw prednisone from 25% of patients at the first attempt and ultimately in 37%.

Adult↗

A familial visceral myopathy.

A kindred contained at least 18 members with visceral myopathy. Sixteen had symptoms of chronic obstruction of the gastrointestinal or urinary tracts. Of six patients with megaduodenum on contrast roentgenograms, two were asymptomatic. Four patients had redundant colon on barium enema, and four had megacystis. Specimens from duodenum, jejunum, ileum, colon, or urinary bladder from five patients showed thinning and extensive collagen replacement of the longitudinal muscle layer; ganglion cells were normal by light and electron microscopy. Esophageal manometry in three patients showed decreased gastroesophageal sphincter pressures and no contractions in the smooth muscle segment of the esophagus; duodenal manometry showed a low frequency and amplitude of contractions. Three patients developed fever and signs of peritonitis after operations to bypass dilated segments. This seems to be a generalized smooth muscle disease with variable clinical manifestations and with an autosomal dominant or sex-linked dominant mode of inheritance.

Adolescent↗

Effect of sulfasalazine on digoxin bioavailability.

Low levels of digoxin were noted in a patient receiving digoxin and sulfasalazine (SSA). Discontinuation of SSA resulted in a significant increase in serum digoxin levels. To determine whether or not SSA consistently interfered with the therapeutic effect of digoxin, both drugs were administered to 10 normal subjects in a crossover study. Each received 2 doses of digoxin (0.5 mg, elixir): one dose given alone, and a second dose after 6 days of treatment with SSA. When digoxin was given with SSA, the average area under the serum digoxin curve fell from the control value of 8.79 ng-hr-ml(-1) to 6.66 ng-hr-ml(-1) (p less than 0.05), fell and total urinary excretion decreased from 278 mcg/10 days to 228 mcg/10 days (p less than 0.025). These changes suggest interference with the bioavailability of digoxin by SSA. Studies were conducted to determine whether SSA inhibited digoxin absorption by physically absorbing the glycoside from solution. In vitro tests failed to reveal any significant adsorptive properties for SSA.

Absorption↗

Correlation of contractions and transit in rat small intestine.

A single strain gauge was implanted chronically in the proximal jejunum of the rat to record contractions. FAsted pentobarbital-anesthetized animals received glucagon, caerulein, or isotonic saline control infusions intravenously while contractions were recorded. In control animals, the distribution of contractions in time showed clusters, with peaks at intervals of 14.24 +/-5.6 (SD) min. Glucagon produced dose-related inhibition of contractions. Caerulein at two lower doses produced a more uniform distribution of contractions in time; a higher dose caused inhibition. In other fasted rats, an isotopically labeled bolus was given through a chronically implanted duodenal cathether, and its distribution along the small intestine was examined in animals receiving the same doses of glucagon, caerulein, and saline. Glucagon caused a dose-related delay in transit. Those doses of caerulein that produced a uniform distribution of contractions accelerated transit; the dose that inhibited contractions delayed transit. Doses of glucagon and caerulein known to affect both motility and transit did not significantly affect water movement. The fasted rat resembles the fasted go in respect to the temporal distributions of jejunal contractions at a single point. Both quantitative and qualitative changes in contractions induce changes in transit.

Animals↗

Intestinal propulsion in the dog. Its relation to food intake and the migratory myoelectric complex.

We studied electrical events and flow in the canine small intestine in vivo. The transit of a small radioactive bolus injected into the jejunum was monitored by counting from a Biebl loop. After feeding, the rate of propulsion of the bolus varied within a narrow range. When food and water were withheld for more than 12 hr, transit of the bolus hecame highly variable. The variability increased at about the same time as the onset of the migratory myoelectric complex associated with fasting. Electrical recordings from the intestinal muscle demonstrated that the bolus was propelled into the loop in advance of the band of intense spike potentials which travels along the small intestine in the fasted state. The bolus was cleared from the loop when the spike potentials reached this segment. Variability of transit after prolonged fasting can be explained by (1) variability in the rate of migration of the phase of intense spike potentials, and (2) the timing of the injection of the bolus in relation to the component phases of the electrical complex. Flow is highly dependent upon the electrical activity and the resulting contraction patterns of the small intestine, which are themselves dependent upon feeding.

Animals↗

Juvenile polyposis and gastrointestinal carcinoma. A study of a kindred.

A kindred contained at least 10 members with single or multiple juvenile polyps of the stomach and large intestine. Several additional polyps had both adenomatous and juvenile features. Eleven members of the kindred have had gastrointestinal carcinoma of the stomach, duodenum, pancreas, or proximal colon. The pattern of inheritance in this kindred suggests either a single or two closely linked autosomal dominant determinants for gastrointestinal carcinoma and polyposis. Management of this kindred is complicated due to the occurrence of gastrointestinal carcinoma without polyposis.

Adenocarcinoma↗