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M Karaus

Publications and source records attributed to M Karaus.

27 records · Page 2Linked to original sources
PubMed1988

Effect of sennosides on colon motility in cats.

The actions of sennosides on colonic motility are incompletely understood. We therefore studied the effects of sennosides A + B on colonic myoelectric activity and transit of a radio-opaque meal in 7 conscious cats. Intraduodenal application of sennosides (2 mg/kg body weight) accelerated the half colon transit time from 60 +/- 10 (SEM) to 43 +/- 7 min. At the same time the ratio of long-spike bursts to short-spike bursts was changed from 0.22 to 10.1. Loperamide, an antidiarrheal agent, had the opposite effect. The overall spike activity was not altered by sennosides, but increased by loperamide. It is concluded that the propulsive action of sennosides in the colon is reflected by myoelectric patterns and not by the total number of spikes.

Animals↗
PubMed1988

Computer analysis of pressure tracings from the sphincter of Oddi.

Since the sphincter of Oddi exhibits very regular phasic motor activity it offers itself to the design of a simple computer program in the analysis of gastrointesinal motility. This investigation is the first attempt of a practical application of such a computer program. The signals coming out of the pressure preamplifier are submitted to active filtering in order to prevent aliasing and then to analog to digital conversion. After being fed into a computer they are precessed in a number of controllable and adaptable steps before the final analysis. Computer analysis then yields a detailed quantitative print out of a large variety of variables which compares very favourably with the visual analysis. It speeds up the time of analysis and allows for a study of long-term recording. Computer analysis of pressure tracings from the sphincter of Oddi may serve as a model for a study of motor activity of all parts of the digestive tract with this modern method of data handling.

Ampulla of Vater↗
PubMed1987

Giant migrating contractions during defecation in the dog colon.

The colonic motor correlates of defecation were studied in 5 conscious dogs. A set of six strain-gauge transducers were implanted on the colon of each dog. An implanted cannula gave access to the terminal ileum. During a total control recording period of 230 h we observed 12 large-amplitude contractions that occurred spontaneously in the proximal colon and migrated caudad. We called them giant migrating contractions. The mean amplitude of these contractions was 2.8 times larger than the mean peak amplitude of phasic contractions during colonic motor complexes. The following stimuli were applied to induce defecation: 2 mg/kg guanethidine (i.v.), 30 micrograms/kg neostigmine (i.v.), 1-4 ml/kg castor oil (p.o.), 200 ml of 25% glucose (into ileum), and rectal distention by a balloon (120 ml). In 85% of experiments with guanethidine, neostigmine, glucose, and castor oil, giant migrating contractions occurred before defecation. The giant migrating contractions migrated over the entire colon or a part of its length. The migration velocity varied from 0.2 to 3.2 cm/s (mean +/- SE, 0.82 +/- 0.1 cm/s). In 11% of the experiments, giant contractions occurred almost simultaneously at different recording sites at the time of defecation. In 4% of the experiments giant contractions occurred only at a single site. Balloon expulsion was only rarely accompanied by giant contractions in the colon, and then occurred only at a distal site and did not migrate. We conclude that the colon has spontaneous but infrequent large-amplitude caudad-migrating contractions. These contractions may be the motor equivalent of mass movements. Defecation is usually preceded by colonic giant migrating contractions. The giant migrating contractions may provide a major force for defecation and be partially responsible for the evacuation of the colon during defecation. However, evacuation of contents such as a balloon seems to be possible without giant migrating contractions.

Animals↗
PubMed1987

Effects of oral laxatives on colonic motor complexes in dogs.

The effect of oral laxatives on the organisation of colonic motor complexes was investigated in four conscious dogs. Six strain gauge transducers were implanted on the colon of each dog. After a control period of two to three hours, dogs were orally dosed with 1, 2, or 4 ml/kg of castor oil, or 0.5 g/kg magnesium citrate. Oral olive oil, 4 ml/kg, was used as control. The recording was continued for another 10 hours or until defecation occurred. Each dog showed spontaneous cyclic bursts of contractions (contractile states) at all recording sites during the control period. Contractile states migrating orad or caudad over at least half the length of the colon were called colonic migrating motor complexes (CMMC). Castor oil and magnesium citrate significantly increased the period of colonic motor complexes, but olive oil had no significant effect. None of the above substances changed the percentage of orad migrating motor complexes, as compared with the control values. Periods in which colonic motor activity was completely absent for at least 60 min over at least three consecutive recording sites occurred more frequently after all of the substances. The occurrence of these periods of inhibition, however, was not a consistent feature and there seemed to be no relationship between the occurrence of inhibitory periods and defecation during the recording period. The dogs defecated within 10 hours after administration of magnesium citrate, 1, 2, and 4 ml/kg of castor oil in 12.5, 25, 37.5, and 88.8% of experiments respectively, but never with olive oil. Defecation was generally accompanied by giant migrating contractions in the colon. We conclude that oral laxatives, magnesium citrate and castor oil have a profound effect on colonic motor complexes and colonic motor activity. The period of CMMC is significantly prolonged after their oral administration because of an increased number of non-migrating motor complexes or periods of inhibition of motor activity.

Animals↗
PubMed1987

Differential effects of [Gln4]neurotensin on circular and longitudinal muscle of dog ileum in vitro.

We studied the effects of neurotensin analogue [Gln4]-neurotensin on isolated dog ileal longitudinal and circular muscle strips. [Gln4]neurotensin stimulated the spontaneous contractile activity of the circular muscle but inhibited that of the longitudinal muscle in a dose-dependent fashion. Hexamethonium had no effect on the spontaneous longitudinal or circular muscle contractile activity. Atropine and tetrodotoxin (TTX) both inhibited the longitudinal muscle. Atropine had no effect on the circular muscle, but TTX stimulated it. The effects of [Gln4]neurotensin on the circular muscle were reduced but not completely abolished by atropine. The inhibition of the longitudinal muscle by [Gln4]neurotensin was not reduced by any of the above antagonists but was enhanced by atropine. Electrical field stimulation (10 Hz, 100 mA) stimulated the longitudinal muscle and inhibited or stimulated the circular muscle depending on the pulse width of the stimulus. These effects were unaffected by [Gln4]neurotensin. We conclude that [Gln4]neurotensin has differential effects on isolated muscle strips of the two muscle layers in the dog ileum. It stimulates the circular muscle partially through cholinergic nerves at preganglionic sites and partially through a direct myogenic effect. [Gln4]neurotensin inhibits the spontaneous activity of the longitudinal muscle presumably by reducing the excitability of cholinergic nerves at postganglionic sites.

Animals↗
PubMed1987

[Neural regulation of the secretion of the small and large intestines].

The small bowel and the colon are supplied by a dense network of nerves. Nervous control of secretion is influenced by peripheral and central nerves. The small and large intestine are tonically inhibited by the enteric nervous system, in particular by the submucous plexus, to maximally absorb fluid and electrolytes. Choleratoxin induced intestinal secretion may be suppressed by central opiate receptors, and central gamma-aminobutyric acid receptors may inhibit intestinal absorption. Besides the classical neurotransmitters acetylcholine and noradrenalin, which stimulate and inhibit, respectively, secretion, a large number of regulatory peptides and other substances which mainly act as cotransmitters and neuromodulators affect mucosal transport in the small and large intestine. Secretion induced by nerves appears to play a major role in diabetic and infectious diarrhea. The nervous control of secretion in the small and large intestine is an interesting area of current research in intestinal transport. So far already, the results shed new light in a better understanding of intestinal pathophysiology, and they point towards new therapeutic modalities in diarrhea and constipation.

Animals↗
PubMed1983

The effects of deoxycholic and ricinoleic acid on the isolated circular muscle of the cat colon are modified by leucine-enkephalin.

The mechanism of the diarrheogenic effect of bile acids and fatty acids is incompletely understood. In order to study their effects on motility we tested sodium deoxycholate and sodium ricinoleate in their actions on the spontaneous mechanical and myoelectrical activity of the isolated circular muscle of the cat colon in a perfusion apparatus. Sodium deoxycholate activated the muscle in concentrations from 10(-9) to 10(-5) M. ED50 was 6.3 X 10(-9) M, ED100 10(-6) M. Sodium ricinoleate similarly stimulated muscle contractions. ED50 was 2.3 X 10(-7) M, ED100 5.1 X 10(-6) M. Both agents increased the occurrence of oscillating potentials in the myoelectrical records. Oscillations probably correspond to the migrating electrical complexes in diarrhea. The addition of leucine-enkephalin augmented primarily the number of brief spike potentials which may correspond to segmenting contractions. Thus, bile acids and fatty acids cause profound changes in colonic motility which by themselves may promote diarrhea. The endogenous opiate leucine-enkephalin could possibly counteract these effects.

Animals↗