Biomedical subjects

V E Cowles

Publications and source records attributed to V E Cowles.

30 records · Page 2Linked to original sources

PubMed1990

Effect of T. spiralis infection on intestinal motor activity in the fasted state.

We sought to determine the effects of Trichinella spiralis infection on small intestinal motor activity in the fasted state in dogs and relate it to clinical symptoms during the intestinal phase of trichinosis. Motor activity was recorded by strain gauge force transducers. Infection with T. spiralis resulted in a significant increase in the incidence and proximal origination of giant migrating contractions (GMCs) during the first 5 days postinfection. This was also the time when the dogs had diarrhea. The dogs were often restless and showed signs of discomfort during proximally originating GMCs. The incidence of retrograde giant contractions (RGCs) increased significantly on the 2nd and 3rd day postinfection. RGCs were followed by vomiting 71% of the time during infection. The migrating motor complex cycle length increased significantly, and this was due to intestinal "amyogenesia" and "dysmyogenesia". During these phenomena, electrical control activity was almost completely obliterated in the proximal half of the small intestine (amyogenesia) and became irregular and unstable in the distal half (dysmyogenesia). Intestinal amyogenesia and dysmyogenesia lasted up to 4 h and were terminated by a GMC. We conclude that diarrhea induced by T. spiralis infection is closely associated with an increase in the incidence and proximal origin of GMCs. These GMCs may also be the motor correlates of abdominal cramping and pain during the intestinal phase of trichinosis.

Animals↗

PubMed1989

Effects of vagal cryo-interruption on colon contractions in monkeys.

The influence of the vagus nerve on normal colon contractions, and the distal extent of this influence along the colon, is unknown. It is generally thought that the vagus nerve has little, if any, influence on normal colon contractions, and if there is any effect, it is limited to the proximal colon. The technique of reversible truncal vagotomy by cooling (vagal cryo-interruption) was used to explore the influence, and extent of any influence, of the vagus nerve on contractions of the colon in unanesthetized monkeys. Each monkey was subjected to vagal cryo-interruption in the fasted and fed states. In both states this caused a significant decrease in contractions in the proximal, middle, and distal portions of the colon, compared with baseline control and recovery periods. These studies indicate that the vagus nerve plays a role in normal contractions of the intra-abdominal colon in both the fasted and the fed states and that it also plays a role in the gastrocolic response.

Animals↗

PubMed1987

Effects of adrenergic agents on colonic motility.

Sympathetic hyperactivity has been implicated as an etiologic factor in postoperative ileus. The effects of methoxamine (alpha-agonist) and isoproterenol (beta-agonist) on colon contractions and blood flow were studied in nine monkeys. Phentolamine (alpha-antagonist) and propranolol (beta-antagonist) were used to block the effects of the appropriate agonist. Methoxamine caused a dose-related inhibition of colon contractions and a decrease in inferior mesenteric artery (IMA) blood flow. Isoproterenol caused a dose-related inhibition of colon contractions and an increase in IMA blood flow. The contractile and blood flow effects of methoxamine were blocked by phentolamine and those of isoproterenol by propranolol. Mechanical reduction of IMA blood flow by an amount equivalent to that observed with the highest dose of methoxamine caused no change in contractions in the segment of colon supplied by the IMA. Both alpha- and beta-agonists inhibit colon contractions and have the expected effects on IMA blood flow. The contractile and blood flow responses of the agonists can be blocked by appropriate antagonists. The blood flow changes are not responsible for the contractile changes. These results indicate that sympathetic hyperactivity may play a role in postoperative ileus.

Animals↗

PubMed1986

Differential sensitivities of morphine and motilin to initiate migrating motor complex in isolated intestinal segments. Regeneration of intrinsic nerves.

The effect of morphine and motilin on surgically isolated segments of small intestine was studied in 8 dogs. In 4 dogs, the small intestine was divided into four segments by simple transection and reanastomosis (group 1); in 4 others, a 2-4-cm colonic segment was interposed at each of the transection sites (group 2). The migrating motor complex initially cycled independently in each segment in group 1 dogs; after that the migration of the migrating motor complex across transection and reanastomosis began to recover and the recovery was complete 100 days after surgery. In contrast, in group 2 dogs the migration of the migrating motor complex from one segment to the next did not recover even 180 days after surgery. Morphine bolus or infusion initiated premature phase III activity in all segments but the sensitivity to morphine decreased distally. Motilin bolus or infusion initiated premature phase III activity only in the first three segments. The sensitivity to motilin also decreased distally. We concluded that (a) the interposition of a foreign segment severely impedes or prevents the regeneration of enteric nerves; (b) the sensitivity of morphine and motilin in initiating premature phase III activity decreases distally in small intestine; and (c) motilin does not initiate premature phase III activity in the ileum, but morphine may initiate premature phase III activity at all sites in the small intestine.

Animals↗

PubMed1986

Resolution of postoperative ileus in humans.

Bipolar electrodes were placed in the ascending and descending colon of 13 patients during laparotomy. The magnitude of their operations varied from exploratory laparotomy to total gastrectomy. The magnitude and length of the operations performed did not correlate positively with the duration of postoperative ileus. Signals were recorded for up to 4 hours daily for up to 8 days after operation during periods of rest and, in some patients, after administration of epidural or parenteral morphine sulfate. Power spectrum analyses of electrical control activity (ECA) showed dominant frequencies in both lower (2-9 cpm) and higher (9-14 cpm) ranges. During postoperative recovery, the mean ECA frequencies in right and left colon were relatively constant, but a variety of dominant ECA frequency relationships were observed. The modal pattern in the right colon was a shift in the dominant frequency from the higher to the lower range as recovery progressed, while the modal pattern in the left colon was persistent dominance of ECA in the higher frequency range. Electrical response activity (ERA) initially was comprised of only random, disorganized single bursts but became progressively more complex through the initial 3 postoperative days with the appearance of more organized bursts and clusters, some of which propagated very slowly (about 5 cm/min) both orad and aborad. ERA recovery culminated, typically on the third or fourth postoperative day, with the return of long bursts of continuous ERA, some of which propagated at a higher velocity (about 80 cm/min) and exclusively in the aborad direction and which were accompanied by passage of flatus or by defecation.

Adolescent↗

PubMed1982

Relationship of duration of postoperative ileus to extent and site of operative dissection.

Postoperative ileus has been thought to be related to intraoperative manipulation of the intestines and to the duration of operative procedures. In order to study the effect of these variables on the postoperative myoelectrical activity of the intestine, six stumptailed monkeys had strain-gauge force transducers and bipolar electrodes placed on gastric antrum, mid-small bowel, right colon, and sigmoid colon. The animals were then subjected to three operations in random order varying in extent and site of dissection: (1) midline incisions, mobilization of right colon and kidney, clamping of renal pedicle, and extensive blunt dissection of right retroperitoneum; (2) the same operation but done on the left side; and (3) midline incision and gentle digital manipulation of the intestines. The first two procedures involved much more intestinal handling and dissection and took five to six times longer than the minimal laparotomy procedure. Postoperative inhibition of bowel motility was most profound and persistent in the colon. The duration and pattern of postoperative ileus in these experiments were independent of the extent, site, and duration of the operative procedure.

Abdomen↗

PubMed1981

Longitudinal muscle of muscularis externa in human and nonhuman primate colon.

The idea that the longitudinal muscle of the muscularis externa of the colon is confined to the colonic teniae in the monkey and human is a common conceptual error. Forty-six colon specimens taken from human and nonhuman primates were reviewed histologically and the distribution and structure of the longitudinal muscle were evaluated. We found that the longitudinal muscle forms a complete coat around the colon although it is considerably thicker in the region of the teniae coli. In addition to its anatomic importance, this observation has implications for the physiology of colon muscle and for certain current hypotheses concerning the etiology of diverticulitis.

Animals↗

PubMed1981

A device to stimulate the mechanical component of malignant bowel obstruction.

A predictable and progressive experimental intestinal obstruction, simulating a malignancy but without neoplastic change has been produced by application of a silicone rubber ring around the bowel of 20 rats, seven dogs, and five monkeys. Serosal reaction produced fibrous tissue that resulted in an "apple core" obstruction. An easily assembled extraluminal balloon device of silicone rubber can be used to produce acute and progressive experimental obstruction, especially of the large bowel.

Acute Disease↗

PubMed1981

Bowel motility after primary resection for colonic obstruction.

The duration of postoperative ileus and changes in contractile frequency of circular muscle were recorded in the colon of monkeys before and after primary resection for distal large bowel obstruction. Obstruction was induced gradually by an implanted device. Resection and primary anastomosis resulted in reduced contractile frequency (postoperative ileus) lasting less than 48 h, significantly shorter than the period of ileus after a control laparotomy.

Animals↗

PubMed1980

Intestinal motility changes in experimental large bowel obstruction.

Bipolar electrodes for recording electrical discharges of colon smooth muscle and strain gages for recording associated contractions of circular muscle were implanted in six rhesus monkeys. After recovery, baseline records were made. The animals then had an obstruction device implanted in sigmoid colon which resulted in progressive compromise of the lumen terminating in complete obstruction after 13 +/- 2 days. Recording were made daily during development of obstruction. As obstruction became more complete, contraction frequency decreased in right colon, increased in left colon proximal to the obstruction, and was unchanged in left colon distal to the obstruction. The frequency of distentions increased in colon proximal to the obstruction but was unchanged distally. Simultaneous mass actions, a complex of nonperistaltic high amplitude contractions and distentions occurring nearly simultaneously throughout the colon which is not seen in normal colon, appeared in colon both proximal and distal to the obstruction and became more frequent as the degree of obstruction progressed. Colon obstruction results in abnormal motility complexes, but not in hyperperistalsis. Mass actions probably are the basis for colic and rushing bowel sounds noted clinically in colon obstruction.

Action Potentials↗

PubMed1979

Electromotor feeding responses of primate ileum and colon.

Serosal bipolar electrodes to record spike discharges and strain gauge force transducers to record circular muscle contractions were placed in pairs on the terminal ileum, cecum, right colon at the ileocecal valve, ascending colon, and proximal transverse colon of sixteen primates. After an overnight fast, electromotor responses to continued fasting or to ingestion of a meal (randomized order) were recorded in awake animals. Feeding led to increased spike discharges and increased frequency of muscle contractions at all sites. The onset of these responses usually was within 6 minutes after feeding; the responses increased progressively during 30 to 45 minutes and then remained more or less at a constant plateau of increased activity. Atropine completely blocked the postcibal responses of ileum and proximal colon for up to 30 minutes. Transit time data of labeled meals excluded direct stimulation by a food bolus as the mechanism of the observed postcibal colonic response. The pattern of response was consistent with humoral mediation.

Animals↗

PubMed1978

A quarter Wheatstone bridge strain gage force transducer for recording gut motility.

Quarter and half Wheatstone bridge extraluminal force transducers for recording of gastrointestinal motility are compared. Modification of the transducer to a quarter bridge is economical, simplifies construction, and improves longevity by eliminating the crossover wire which frequently short circuits. The quarter bridge transducer was found to be as accurate and sensitive as the half bridge transducer.

Animals↗