Search PubMed⌕ Search

Biomedical subjects

R W Summers

Publications and source records attributed to R W Summers.

At least 55 records · Page 3Linked to original sources
PubMed1990

Early results of combined electrohydraulic shock-wave lithotripsy and oral litholytic therapy of gallbladder stones at the University of Iowa.

One hundred thirty-three patients were entered into a randomized, double-blind, placebo-controlled trial of extracorporeal shock-wave lithotripsy for symptomatic gallstones versus extracorporeal shock-wave lithotripsy plus adjuvant litholytic therapy with ursodeoxycholic acid (UDCA). Six months after lithotripsy, patients receiving placebo were crossed over to UDCA therapy without unblinding the study. One hundred sixteen patients have completed 6 months of follow-up. Five patients were dropped from the study. Nine percent have required cholecystectomy (11 patients with biliary colic and 1 with acute cholecystitis). Ninety-one patients had a solitary stone (64 patients had stones less than or equal to 20 mm and 27 patients had stones greater than 20 mm in diameter), and 25 patients had two to three stones. Fifty percent were retreated. Cumulative stone-free rates at 6, 12, and 18 months were 26%, 39%, and 41%, respectively. At 6 months there was a significant advantage for patients treated with UDCA versus placebo (36% vs 17% were stone free) that had disappeared by 12 months (placebo-treated patients had received 6 months of UDCA). Patients with solitary stones equal to or less than 20 mm in diameter treated with UDCA had stone-free rates at 6, 12, and 18 months of 58%, 58%, and 62%, respectively, versus 27%, 56%, and 50%. The difference was significant only at the 6- month follow-up. Stone-free rates for patients with large solitary stones and multiple stones were very low. Extracorporeal shock-wave lithotripsy is both safe and effective therapy for treatment of symptomatic gallstones in patients with a solitary stone equal to or less than 20 mm in diameter. UDCA markedly improves the efficiency of the procedure and results in a stone-free gallbladder sooner.

Administration, Oral↗
PubMed1989

Irradiation increases superoxide dismutase in rat intestinal smooth muscle.

We investigated whether X-irradiation could induce the enzyme superoxide dismutase (SOD) in intestinal muscle. Groups of rats received abdominal irradiation and the time course and dose response for SOD activity determined. Jejunal smooth muscle homogenates were analyzed for the activities of copper/zinc (CuZn) and manganese (Mn) SOD activity and for a mitochondrial marker enzyme, citrate synthase. A progressive rise in Mn SOD activity occurred at 20, 46, and 72 h after 1500 R. No significant changes in Cu-Zn SOD activity occurred at any time after 1500 R. At 20 h after 250 R of X-irradiation, Mn SOD activity increased but no further increase occurred at higher irradiation exposures. At the same time, CuZn SOD activity at 20 h after irradiation was greater than controls only at an exposure of 1000 R (p less than 0.05). Using Western blotting, we were able to clearly demonstrate an increase in immunoreactive Mn SOD protein in muscle samples 20 h after 1500 R. The rise in Mn SOD is not simply due to increase in mitochondrial numbers or increase in all mitochondrial enzyme activities because activity of the mitochondrial marker enzyme citrate synthase was decreased after X-irradiation. Transmission electron microscopic studies demonstrated damage to mitochondria after a dose of 3000 R. The data yield evidence that free radicals play a role in irradiation-induced intestinal smooth muscle injury.

Animals↗
PubMed1989

The pathophysiology, evaluation and management of motility disorders of the biliary tract.

Significant advances in the understanding of biliary tract physiology have occurred during the past 20 years. Through careful studies in animals, the fluid mechanics and normal regulatory mechanisms involved in sphincter of Oddi function have been partially elucidated. Many of the basic concepts have been validated in human studies by newly developed testing methods. Endoscopic retrograde cholangiopancreatography is crucial in demonstrating both normal anatomy and mechanical or structural abnormalities of the duct system. Fat-meal--or CCK-stimulated ultrasonography and quantitative hepatobiliary scintigraphy offer reliable and noninvasive screening methods to evaluate patients with suspected sphincter of Oddi dysfunction. Biliary manometry is key in defining normal and abnormal motility patterns of the sphincter of Oddi region. The existence of the problem is being solidly established, but the optimal therapy is still somewhat unclear. The use of endoscopic balloon dilatation is not encouraging; drug therapy holds promise, but must be subjected to careful clinical trials. Sphincter surgery is fading from use and is being replaced by endoscopic sphincterotomy. Unfortunately the long-term results of sphincterotomy and the overall safety of the procedure are not known. Biliary motility problems do exist, but both diagnostic studies and therapeutic maneuvers require judgement and skill in their application. Use of potentially harmful treatments must be employed only after careful and thorough testing.

Biliary Tract↗
PubMed1988

Intraoperative irradiation in a rat model: histopathological changes in irradiated segments of duodenum.

During intraoperative radiation therapy for carcinoma of the head of the pancreas in humans, a portion of duodenum is often at risk for radiation-induced complications because of its fixed anatomical position within the treatment field. This study was undertaken to determine the feasibility of using the rat as a model to determine the radiotolerance of normal mammalian duodenum. The procedures used to exteriorize and irradiate a selected segment of duodenum are described. Histopathologic changes in 5-cm segments of midduodenum were studied 14 and 28 days after 0, 30, 40, or 50 Gy X-radiation. Complete denudation of the epithelium and thickening of the muscularis and serosal layers occurred in all irradiated segments by day 14. By day 28, even though crypt and villus architectures were atypical, large areas of epithelial regeneration were seen in rats receiving 30 Gy. In contrast, complete denudation of the epithelium were still evident along most of the length of the irradiated segments in rats receiving 40 or 50 Gy. Serosal fibrosis was prominent in all irradiated animals, regardless of dose. These results indicate that radiation doses above 30 Gy carry high risks of complications. The rat is considered a suitable animal model.

Animals↗
PubMed1988

Changes in jejunal myoelectrical activity during exercise in fed untrained dogs.

Seven female dogs (15-20 kg) were instrumented with seven bipolar electrodes sutured at 3-cm intervals to the serosal surface of the proximal jejunum and were exercised at different intensities and durations on a motor-driven treadmill. Slow-wave frequency increased (P less than 0.05) from preexercise control during prolonged (90 min) exercise and during recovery after short-term exercise (30 min) at 70% heart rate reserve (HRR). These changes were associated with an increase in core temperature. Spike-burst frequency (SBF) increased (P less than 0.05) with moderate exercise (50% HRR), but the magnitude was small. When exercise was extended beyond 30 min and during all recovery periods, SBF decreased significantly. Exercise produced migrating myoelectrical complexes in three experiments and less dramatic pattern changes characterized as "clustered contractions" (regular spike bursts preceded and followed by the absence of spike bursts) in at least nine other experiments. We conclude that exercise does alter jejunal myoelectrical activity, but myoelectrical patterns may be more important in explaining exercise-induced gastrointestinal symptoms than changes in spike-burst frequency or duration.

Animals↗
PubMed1988

A comparative study of the effects of four motor-stimulating agents on canine jejunal spike bursts. The use of a computer program to analyze spike burst spread.

The intestinal myoelectric effects of four motor-stimulating drugs were compared in conscious dogs. Dogs were fed a standardized 400-kcal meal, and the myoelectric activity was monitored before and after drug administration. Graded doses of metoclopramide, cisapride, bethanechol, and cholecystokinin (CCK) were compared by means of a computer program to identify spike bursts and determine their frequency, duration, and length of migration. Bethanechol and CCK produced the greatest increase in myoelectric activity in terms of spike burst frequency and duration but the least in terms of length of spike burst spread. Metoclopramide had minimal measurable myoelectric effects. Cisapride had the greatest effect on the length of spike burst migration but little effect on spike burst frequency and duration. The results suggest that cisapride is a more efficient prokinetic agent than bethanechol, CCK, or metoclopramide. The greater length of spike burst spread caused by cisapride was associated with a more rapid rate of transit along the monitored segment of bowel when compared with control. This confirms the correlation between length of spike burst spread and propulsive efficiency.

Animals↗
PubMed1988

Electrohydraulic shock wave lithotripsy (ESWL) fragmentation of retained common duct stones.

Retained or recurrent stones in the common bile duct remain a clinical problem in 2% to 5% of patients undergoing cholecystectomy. Nonoperative extraction via the T tube tract or endoscopic sphincterotomy is successful in 85% to 95% of patients; however, the remainder require reoperation. This study evaluates the efficacy of electrohydraulic shock wave lithotripsy therapy of common duct stones too large to be extracted endoscopically or by T tube. Six patients were entered into the study. Ages ranged from 62 to 93 years. All patients either had severe preexisting systemic disorders or were of an advanced age. Stones ranged in size from 10 to 41 mm, with a mean largest dimension of 22 mm. In all patients either extraction by traditional nonoperative means failed or there was a stone that was considered to be too large to be extracted successfully. Patients were treated with 1200 to 2400 shocks at 16 to 20 kV. Five of six patients were treated with local anesthesia and sedation. Stones were successfully fragmented in all but one patient. Five patients required extraction of the remaining fragments either through the T tube tract (one patient) or via endoscopic sphincterotomy. All patients were free of stones at discharge, with the exception of one patient with severe cirrhosis who had an intrahepatic stone behind a right hepatic duct stricture. This stone had been successfully fragmented but an endoscopic retrograde cholangio-pancreatogram revealed some residual fragments despite normal alkaline phosphatase and bilirubin values. There were no hospital deaths, although the patient with the intrahepatic stone died of bleeding varices several months later. Electrohydraulic shock wave lithotripsy seems to be an effective adjuvant treatment in clearing the bile duct of stones that would otherwise require reoperation.

Aged↗
PubMed1987

Effect of irradiation on morphology and motility of canine small intestine.

In addition to severe damage to the intestinal mucosa, there is evidence based on altered transit that irradiation affects intestinal motor function. A single dose of 938 cGy to the intestine of dogs consistently produced an acute intestinal radiation syndrome consisting of vomiting and diarrhea but was not lethal. In the fasting state, the migrating myoelectric complex was uniformly interrupted. After a meal, jejunal myoelectric activity analyzed by a computer program showed a progressive decline in the number, duration, and length of migration of spike bursts. There were occasionally bizarre motility patterns consisting of clusters of migrating spike bursts. Slow waves demonstrated irregular rhythm and nonuniform morphology. They occasionally migrated in an orad direction and at times were totally uncoupled. At 24 hr and four days after irradiation, the muscle and the neural plexus were nearly normal by light microscopy, but the mucosa exhibited severe necrosis. Therefore, irradiation produces profound functional abnormalities in intestinal muscle even though the morphology is minimally altered.

Animals↗
PubMed1984

Mechanisms of motility changes during acute intestinal obstruction in the dog.

We investigated the effects of autonomic drugs and the role of intestinal contents on the motility changes that occur during acute obstruction. Myoelectric activity was recorded from seven electrodes spaced at 3-cm intervals along the midjejunum of nine conscious dogs. Another animal had electrodes evenly placed throughout the small bowel. Obstruction was created by inflation of an intraluminal balloon. Systemic arterial blood pressure and pulse rate were monitored. Initially, motor activity of the small intestine increased proximal to an acute intestinal obstruction and decreased distally. Recordings from the entire small intestine revealed that these effects occurred almost immediately in the region of the obstruction but not at more distant sites. Within 2-3 h, however, proximal hypermotility had extended to the duodenum and distal inhibition had progressed to the terminal ileum. Diversion of intestinal contents without obstruction reduced myoelectric activity distal to the site of drainage. However, reinfusion of chyme distal to the site of obstruction failed to restore inhibited motor activity to control levels. Atropine sulfate (50 micrograms/kg) decreased and neostigmine (5 micrograms X kg-1 X min-1) potentiated the hyperactivity proximal to the obstruction, but neither agent significantly affected the distal inhibition. Phentolamine (1 mg/kg) and propranolol (1 mg/kg) had no effect on proximal or distal motor activity during obstruction; these were doses that blocked cardiovascular responses to adrenergic agonists. These results suggest that changes in luminal contents and in nervous activity both contribute to the intestinal motility changes that accompany obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Desensitization for sulfasalazine skin rash.

Thirteen patients with inflammatory bowel disease and a documented allergy to sulfasalazine, manifested by skin rash with or without fever, were enrolled in a sulfasalazine-desensitization protocol. Twelve patients were successfully desensitized by using two concentrations of a liquid suspension of sulfasalazine. Four of thirteen patients developed a rash during the protocol. Although one patient refused further attempts at desensitization, the remainder completed the regimen successfully, despite recurrence of the rash on two occasions in one patient. No predilection to either fast or slow acetylator phenotype was found. This simple and convenient tolerance induction regimen may be used safely to desensitize most patients with sulfasalazine allergy manifested by skin rash with or without fever, despite recurrence of the rash during tolerance induction. Patients with serious reactions to sulfasalazine, such as agranulocytosis, toxic epidermal necrolysis, or fibrosing alveolitis, are not candidates for desensitization.

Acetylation↗
PubMed1984

Isoproterenol induces activity fronts in fed dogs through somatostatin release.

We confirmed previous studies by others that intravenous somatostatin infusions (1.4 and 2.5 micrograms/kg X h) induced jejunal activity fronts in fed dogs. This finding, coupled with earlier demonstrations that somatostatin is released from the stomach and pancreas in vitro by isoproterenol, led us to investigate the possible role of somatostatin in mediating isoproterenol-induced activity fronts. Plasma somatostatin and motilin concentrations were determined after a meat-base meal, before and after isoproterenol infusions (0.5 micrograms/kg X min). Jejunal activity fronts were initiated in 15 of 17 experiments an average of 25 min after the start of the isoproterenol infusion. The concentration of motilin did not change, but somatostatin concentrations increased progressively beginning 15 min after starting the isoproterenol infusion. Thus, isoproterenol released somatostatin in vivo and this release was associated with jejunal activity fronts. The rise in plasma somatostatin concentration was similar to that obtained after somatostatin infusions, although in the latter experiments the activity fronts began soon after initiation of the somatostatin infusion. The results suggest that isoproterenol-induced activity fronts are mediated by somatostatin. We speculate that beta-adrenergic nerves may induce activity fronts through somatostatin release, possibly in situations such as extreme stress.

Action Potentials↗
PubMed1983

Activity fronts in fed dogs: effect of a beta-adrenergic agonist.

The effect of the beta-adrenergic agonist isoproterenol on intestinal myoelectric activities was studied in fed dogs. A 15-min isoproterenol infusion (0.5 micrograms X kg-1 X min-1) initiated activity fronts after a meal in 14 of 16 experiments. The phase III motor activity was of similar duration and migrated aborally at the same rate as spontaneous fronts occurring in the interdigestive period; however, the activity fronts usually originated in the midjejunum and seldom migrated to the terminal ileum. The isoproterenol-induced fronts were blocked by pretreatment with propranolol (1 mg/kg). Activity fronts were not induced by sodium nitroprusside (10 micrograms X kg-1 X min-1), even though it inhibited myoelectric activity and induced hypotension and tachycardia to a degree similar to that caused by isoproterenol. The effects of isoproterenol were not blocked by vagotomy. Longer isoproterenol infusions of 2 h produced one but not more activity fronts and infusions in the fasted state did not induce premature fronts. These results do not support the hypothesis that the effect of isoproterenol is due to a neural reflex, and further studies are necessary to determine which of several potential mechanisms is responsible for this effect.

Animals↗
PubMed1983

Acute intestinal obstruction: an electromyographic study in dogs.

We have investigated the motility effects of acute experimental canine intestinal obstruction. A 30-min midjejunal obstruction was produced by clamping a Biebl loop or by inflating an intraluminal balloon. Spike bursts from serosal electrodes proximal to the site of obstruction increased markedly, while those from distal electrodes decreased. When the obstruction from an intraluminal Foley catheter was continued for 5.5 h, the inhibition persisted distally but the proximal contractile activity gradually fell to control levels. The reduced proximal activity after prolonged obstruction was largely due to clusters of regular intense spike bursts preceded and followed by lengthening periods of absent motor activity. Similar clustered contractions obliterated the lumen when the passage of barium through a Thiry-Vella loop was monitored fluoroscopically. Significant motility changes occur in intestinal obstruction, but an increased understanding of the mechanisms involved awaits future studies.

Animals↗
PubMed1983

Jejunal manometry patterns in health, partial intestinal obstruction, and pseudoobstruction.

The purpose of this study was to determine the utility of jejunal manometry in evaluating patients having partial small intestinal obstruction or the pseudoobstruction syndrome. We studied 10 healthy volunteers, 9 patients with documented mechanical obstruction, and 3 patients with chronic intestinal pseudoobstruction during fasting and for 2 h after a 650-kcal meal. Contractile activity, especially during phase 2, was extremely variable in all individuals studied. After the meal, the most striking finding in mechanical obstruction was the regular occurrence of clustered contractions. These were defined as 3-10 regular contractions, occurring 1 per 5 s, preceded and followed by at least 1 min of absent motor activity. The associated periods of quiescent motor activity may account for the unexpectedly reduced frequency and motility index in obstructed patients compared with normal subjects after the meal. Two different contractile patterns occurred in patients with pseudoobstruction. Before and after the meal, infrequent and low-amplitude contractions occurred in 2 patients, and multiple, aborally migrating, clustered contractions occurred in the other patient with pseudoobstruction. Manometric abnormalities occur in both mechanical obstruction and pseudoobstruction. However, the technique is probably not more sensitive than radiologic procedures, and the abnormalities that are detected by manometry are not specific. Some of the same motility changes occurred in both disorders.

Adult↗
PubMed1982

Ulcerative colitis and sensorineural hearing loss: is there a relationship?

A number of systemic complications are recognized in patients with ulcerative colitis. We describe a patient with this disease who developed severe bilateral sensorineural hearing loss and vestibular dysfunction. Her hearing deficit improved dramatically with corticosteroids and cyclophosphamide therapy. The association between these two conditions has not previously been reported.

Adult↗