Biomedical subjects

M F Otterson

Publications and source records attributed to M F Otterson.

8 recordsLinked to original sources

PubMed1992

Fractionated doses of ionizing radiation alter postprandial small intestinal motor activity.

We investigated the effects of total abdominal fractionated irradiation on postprandial small intestinal motor activity in five dogs. Five strain-gauge transducers were attached to the seromuscular layer of the duodenum, jejunum, and ileum of each dog to record circular muscle contractions. Radiation (250 cGy) was administered three times a week on alternate days for three successive weeks (total dose, 2250 cGy). Postprandial 4-hr recordings were made once each week during radiation and at one and three weeks following completion of radiation. Duodenal mean amplitude and area under contractions did not change during or following the radiation schedule, but the mean frequency and duration of duodenal contractions decreased during the radiation schedule. Both parameters returned to baseline values postirradiation. Jejunal mean duration, amplitude, area, and frequency of contractions decreased during radiation; mean amplitude and area returned to baseline values postirradiation but not the duration and frequency of contractions. All parameters of ileal contractions decreased during radiation, and all but area and amplitudes remained depressed postirradiation. Significantly decreased strength and frequency of contractions, particularly in the jejunum and ileum occur during and following irradiation. These changes may potentially alter transit time.

Animals↗

PubMed1992

Effects of fractionated doses of ionizing radiation on colonic motor activity.

The colonic motor effects of fractionated irradiation were studied in five conscious dogs. Seven colonic and two ileal strain gauge transducers were implanted. After control recordings, an abdominal dose of 250 cGy was administered three times a week on alternate days for three successive weeks (total dose 2,250 cGy). Recordings were then continued for 3 wk after the completion of radiation. Colonic giant migrating contractions (GMCs) occurred at a frequency of 0.15 +/- 0.05 contractions/h in the control state. Only one of these contractions (8.3%) originated in the small bowel and propagated into the colon. Abdominal field irradiation significantly increased the incidence of colonic GMCs to 0.51 +/- 0.11 contractions/h (P < 0.05). Fifty-four percent of GMCs originated in the small intestine. GMCs during the radiation schedule were associated with explosive diarrhea on seven occasions. Irradiation did not alter the frequency of colonic migrating motor complexes, but the mean duration of contractile states decreased in the middle and distal colon. Diarrhea occurred as early as the second dose of radiation. Pathological changes in the colon were correlated with motor activity. Both small intestinal and colonic GMCs reverted to control frequencies after cessation of radiation exposure. Abdominal irradiation significantly altered the contractile activity of the colon. These changes are associated with abdominal cramping and diarrhea.

Animals↗

PubMed1990

Small intestinal amyogenesia and dysmyogenesia induced by morphine and loperamide.

We studied the effects of morphine and loperamide on small bowel myoelectric and contractile activity in 12 conscious dogs. After initially producing premature migrating myoelectric complexes, both substances destabilized and obliterated electrical control activity (ECA). The obliteration of ECA occurred mainly in the proximal half of the small intestine. During ECA obliteration, the base line was almost flat at the usual amplification. At higher amplification, the base line exhibited irregular low level fluctuations that could not be related to electrical response activity (ERA) bursts or contractions. The mean time lag for obliteration of ECA in the proximal small intestine decreased at higher doses of morphine infusion. During the destabilization and obliteration of ECA, contractions and ERA bursts occurred in unusual patterns. The ERA bursts and contractions were generally discoordinated. However, in the proximal small intestine some contractions migrated rapidly and uninterrupted at 32 +/- 7 cm/s over long distances (124 +/- 24 cm). ECA destabilization and obliteration were reversed in approximately 15-30 min after the ingestion of a meal or intravenous administration of atropine, hexamethonium, or naloxone. We conclude that during the absence or destabilization of ECA, the ERA bursts and contractions occur in an uncontrolled manner. These two states were called "amyogenesia" and "dysmyogenesia," respectively. The unusual patterns of contractions during small intestinal amyogenesia and dysmyogenesia may be one of the factors in delayed intestinal transit produced by morphine and loperamide.

Animals↗

PubMed1990

Gastrointestinal motor effects of erythromycin.

We studied the small intestinal motor effects of oral and intravenous (iv) erythromycin in 10 conscious dogs. After control recordings with placebo, oral or iv erythromycin was given at 40% of the migrating motor complex (MMC) cycle. Recordings were made after administration until normal contractile activity had returned or 12 h postdrug administration. Low doses initiated a premature MMC. High doses, however, prolonged the MMC cycle length. Erythromycin reduced the MMC propagation velocity at all doses. Both oral and iv erythromycin induced amyogenesia. During this pattern, electrical control activity was obliterated in the proximal and destabilized in the distal small intestine. Erythromycin also increased the incidence of retrograde giant contractions (RGCs) and vomiting. These effects occurred within the first 2 h after oral and within the first 30 min after iv administration. The incidence of giant migrating contractions (GMCs) increased significantly from 5 to 12 h but not from 0 to 5 h after administration. The distance of origination of GMCs from the ileocolonic junction was significantly increased from 5 to 12 h. The amplitude ratio, duration, and velocity of migration of GMCs induced after erythromycin were similar to control values. Clusters of coordinated antral and duodenal contractions also occurred early after administration. Our findings suggest that erythromycin has multiple motor effects on the stomach and small intestine. Diarrhea, abdominal cramping, and vomiting associated with erythromycin may be related to increased incidence of GMCs and RGCs. Erythromycin has a biphasic effect on MMC cycle length, initiating premature MMCs at low doses and prolonging their cycle length at higher doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1989

Local effect of substance P on colonic motor activity in different experimental states.

We studied the effects of close intra-arterial injections of substance P on colonic motor activity in the conscious state, during anesthesia, and during acute laparotomy. In the conscious state, with enteric nerves intact, substance P stimulated postsynaptic cholinergic neurons to induce a large amplitude and long duration contraction. This response was blocked by prior close intra-arterial injection of atropine and tetrodotoxin (TTX) but not hexamethonium. Hexamethonium and TTX given alone, close intra-arterially, induced a series of short-duration contractions. Prior close intra-arterial administration of hexamethonium significantly enhanced the colonic motor response to substance P. After blockade of nerve conduction by TTX, substance P induced a series of short-duration contractions with characteristics different from those when the nerves were functioning. Anesthesia alone had little effect on the colonic motor response to substance P, but laparotomy inhibited it significantly. Laparotomy similarly inhibited the contractile response to bethanechol. Gut handling had no further effect on this inhibition. We conclude that in the conscious state substance P acts preferentially on postsynaptic cholinergic neurons to contract colonic circular muscle. When the intrinsic nerves are blocked, substance P may act directly on the smooth muscle to induce circular muscle contractions with characteristics different from those induced when nerves are intact. Substance P also has a weak inhibitory motor effect by its action on presynaptic neurons that synapse on postganglionic intrinsic inhibitory neurons. Anesthetic doses of barbiturates have no major effects on the neuromuscular response to substance P, but laparotomy significantly inhibits the smooth muscle response and selectively blocks some neurons.

Animals↗

PubMed1989

Small intestinal physiology and pathophysiology.

The small intestine, like the rest of the gastrointestinal tract, is an intelligent organ. It generates a wide variety of motor patterns to meet motility requirements in different situations. Its basic motor function after a meal is to mix the chyme with exocrine and intestinal secretions, agitate its contents to uniformly and evenly expose them to the mucosal surface, and to propel them distally at a rate that allows optimal absorption of food components, and reabsorption of bile. Most of these functions are performed by individual phasic contractions. In humans, the phasic contractions are largely disorganized in time and space. These contractions may cause mixing and agitation of luminal contents with slow distal propulsion. Occasionally, an individual contraction of large amplitude and long duration migrates over several centimeters and may rapidly propel the contents over this distance. In general, the spatial and temporal relationships of individual phasic contractions become less organized distally, resulting in a slower propulsion rate in the distal small intestine than in the proximal small intestine. The migrating clustered contractions generated after a meal may also be propulsive, but because of their unpredictable and irregular occurrence, their precise role in postprandial propulsion is incompletely understood. Rapidly migrating contractions may occur when the electrical control activity is obliterated by pharmacologic agents or during parasitic infections. Their effects on motility are not known yet. Between meals, when digestion is complete, the small intestine generates migrating motor complexes that help keep the small intestine clean by dislodging debris from the villi and dumping them into the colon. This may prevent decay of these materials in the small intestine and limit their contribution to bacterial overgrowth. Giant migrating contractions may perform a similar function in the distal small intestine as well as return any refluxed fecal material back to the colon. However, the major role of giant migrating contractions may be, in pathologic states, associated with abdominal cramping and diarrhea. Giant migrating contractions are associated with mass movements. Vomiting is preceded by a retrograde giant contraction. This contraction rapidly empties the contents of the proximal half of small intestine into the stomach in preparation for vomitus expulsion by contraction of abdominal and diaphragmatic muscles. The three basic mechanisms of control of spatial and temporal patterns of contractions are myogenic, neural, and chemical.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

Effects of fractionated doses of ionizing radiation on small intestinal motor activity.

The small intestinal motor effects of fractionated doses of ionizing radiation were studied in 6 conscious dogs. Eight strain-gauge transducers were implanted on the small intestine and a single gauge on the ascending colon, of each dog. After control recordings, an abdominal dose of 250 cGy was administered three times a week on alternate days for 3 successive weeks (total dose, 2250 cGy). Recordings were then made for 4 wk of follow-up. Giant migrating contractions occurred 11 times in 520 h of control recordings in the fasted and fed state, with a mean distance of origin of 55 +/- 16 cm from the ileocolonic junction. Abdominal field irradiation significantly increased the incidence and distance of origin of these giant contractions to 438 in 745 recording hours and 158 +/- 7 cm from the ileocolonic junction, respectively. The incidence of giant migrating contractions peaked after the second dose of radiation. The amplitude ratio of radiation-induced giant migrating contractions to phase III contractions, and their duration and velocity of migration, were similar to the control state. The dogs developed diarrhea and vomiting as early as the first fraction of radiation. Irradiation also increased the incidence of retrograde giant contractions from 8 in 520 h of control recording to 42 in 745 h of recording during the radiation schedule. The radiation-induced retrograde giant contractions peaked in incidence on the day of the first fraction of radiation and were more likely to be associated with a vomiting episode than those occurring in the control period. Migrating motor complex cycling persisted during radiation and its cycle length was not different from the control or postradiation values. Our findings suggest that some of the side effects of radiation such as diarrhea, abdominal cramping, and vomiting may be related to the dramatically increased incidence of giant migrating contractions and retrograde giant contractions.

Animals↗

PubMed1988

Gastrointestinal motility: some basic concepts.

The spatial and temporal patterns of phasic contractions in the gastrointestinal tract are regulated by a complex interplay between the myogenic, neural and chemical control mechanisms. These contractions are largely responsible for the mixing and propulsive movements of the gut after a meal. In the fasted state, organized groups of contractions called cyclic motor activity and migrating motor complex keep the upper digestive tract clean of residual food and debris. In addition, the small intestine and the colon generate giant migrating contractions which are several-fold stronger than the postprandial phasic contractions and migrate uninterrupted over long distances. The giant migrating contractions are effective in rapid propulsion. The upper small intestine and the antrum generate retrograde giant contractions that generally precede vomiting.

Animals↗