[Substances used in animal production].
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Animal Husbandry↗
Biomedical subjects
Y Ruckebusch
Publications and source records attributed to Y Ruckebusch.
[The gastroduodenal junction: functional significance].
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Animals↗
Babesia major: abomasal transmural potential difference, and antroduodenal motility changes associated with experimental infection in calf.
Transmural potential difference, pH and ionic concentrations of the abomasal contents were measured in three calves. Antroduodenal motor patterns were recorded using electrodes and strain-gauge transducers fixed on the antrum and the duodenum. The calves were infected with 8 x 10(9) Babesia major intravenously and a significant drop in transmural potential difference, concomitant with a steady increase in Na+ and K+ concentrations of the abomasal contents occurred within 2 days. The onset of fever on the 5th day after infection was associated with an increased frequency of duodenal migrating myoelectric complexes and episodes of bradygastria on the distal antrum. These changes disappeared at the end of fever. We conclude that transmural potential difference changes and Na+-K+ concentrations in the abomasal fluid could reflect changes in the ionic permeability of the gastric wall. These effects may represent early signs of Babesia infection.
Abomasum↗
[Masticatory cycles of the rumination type in vagotomized lambs].
Contractions of the fluid-filled RR dependent upon the activity of the myenteric plexus were observed within 2 weeks after vagotomy in sheep maintained on a liquid diet. Spontaneous but not adrenergic evoked rumination was recorded beyond the 5th week after vagotomy. The observation of ruminating-like activity during 120 to 200 min per day in chronically-vagotomized sheep indicates that the onset of rumination does not require a gastric afferent pathway.
Animals↗
Hexamethonium: a probe to assess autonomic nervous system involvement in upper gastrointestinal functions in conscious sheep.
Hexamethonium, which inhibits cholinergic transmission by preventing acetylcholine release, has been considered an ideal reference drug for the blockade of autonomic ganglia, Auerbach plexus and reflex gastrointestinal secretions. The degree of inhibition of ruminant gastrointestinal functions with this reference drug were as follows: cyclical contractions of the reticulo-rumen and abomasal motility greater than gastric acid secretion and duodenal migrating myoelectrical complexes. Although reduced at high dosages, the initiation of migrating myoelectric complexes was enhanced at clinically used dosages. The duration of the inhibition of reticular contractions was dose-related varying from 0.5 to 5 h for 1.25 to 20 mg/kg subcutaneously. Abomasal motility and acid secretion were similarly reduced but exhibited strong and long-lasting rebound effects. Inhibition of the reticulum by the blockade of muscarinic receptors by atropine was also dose-related lasting from 0.5 to 3 h for 0.5 to 2 mg/kg, whereas inhibition of the abomasal motor and secretory functions lasted from 1 to 6 h. These results suggest a higher degree of impingement of the parasympathetic pathways on abomasal acid secretion and motility than on the cyclical activity of the reticulum and only a modulatory role of the extrinsic neural activity on the cyclical motor events of the duodenum.
Abomasum↗
Early myoelectrical activity changes during gastric or duodenal ulceration in dogs.
Antroduodenal myoelectric activity and gastric transmural potential difference were recorded before and during fundic, antral, or duodenal ulceration in dogs. Gastric injury was obtained by electrocoagulation of the fundic or antral mucosa. Duodenal ulceration was induced by cysteamine injection which was accompanied by nausea or vomiting. Both antral electrocoagulation and cysteamine injection were also accompanied by antral dysrhythmia and a transient decrease of the gastric transmural potential difference. Effects of antral electrocoagulation were prevented by selective vagotomy. Since antral dysrhythmia disappeared as soon as the antral or duodenal ulcers became active, ie, within three days and 24 hr respectively, it is suggested that antral dysrhythmia is the result of antroduodenal stimulation and could thus not be assessed as a criterion of active ulceration.
Animals↗
Role of pylorus in the control of the canine migrating motor complex.
The cyclic myoelectric activity of the gastroduodenal area and the antral mucosal ionic permeability, measured by the transmural potential difference, were simultaneously evaluated in the dog. These parameters were recorded before and after section of the omental attachments to the pyloric area, section of the terminal antrum, and excision of a 2-cm segment at the pylorus. None of the surgical procedures modified the duration of the postprandial disruption of the migrating motor complexes, whereas the potential difference was increased. In fasted dogs resection of the omentum increased the migrating motor complex intervals and the duration of the phase of regular spiking activity; however, the regular spiking activities still occurred in a sequential manner. Transection of the terminal antrum was associated with a decrease in duration of the regular spiking activity phases that started simultaneously on the antrum and duodenum, without changes in the migrating motor complex intervals, and prevented the occurrence of the increase in potential difference associated with feeding. After pylorectomy, the migrating motor complex intervals were reduced by 46% on both antrum and duodenum. Our observation that only pylorectomy was able to consistently increase the frequency of migrating motor complexes suggests a pyloric inhibition of the normal pacing of the cyclic motor events at both antral and duodenal levels.
Animals↗
Measurement of gastric emptying rate.
Gastric emptying rate was measured chronically using an electromagnetic probe inserted into the proximal duodenum via a duodenal cannula. Each duodenal gush was identified and its value calculated on the basis of pre-established threshold and timing criteria which eliminate shifts in the baseline and artefacts due to the presence of particles. The net flow of digestive contents and the aboral cumulative flow were displayed online. This system has been used in sheep for continuous measurement of duodenal flow over periods of 3-5 weeks.
Animals↗
Peripheral opioid receptors mediate gastrointestinal secretory and motor effects of dermorphin N-terminal tetrapeptide (NTT) in the dog.
Dermorphin N-terminal-tetrapeptide-amide (NTT) increased both basal and pentagastrin- or histamine-induced secretion in conscious dogs chronically implanted with both gastric fistulae and Heidenhain pouches. These excitatory effects were significantly prevented by the opioid receptor antagonists naloxone and N-methyl-levallorphan-methanesulphonate. In conscious dogs fitted with electrodes and strain-gauges in different parts of gastrointestinal tract, a premature phase III of the migrating myoelectric complex (MMC) in the duodeno-jejunum was triggered by NTT, while the activity of the antrum was not significantly modified. Further, the peptide enhanced the contractile activity of both proximal and distal portions of the colon, including a long-lasting period of increased muscle tone on the distal colon. Either naloxone or N-methyl-levallorphan-methanesulphonate completely prevented motor effects of NTT on gastrointestinal tract. It is concluded that NTT displays significant opiate-like activity on gastric acid secretion and intestinal motility of the dog by activating peripheral mu opioid receptors.
Animals↗
Depression of reticulo-ruminal motor functions through the stimulation of alpha 2-adrenoceptors.
Inhibition of the cyclical contractions of the reticulum and the rumen by detomidine (10-40 micrograms/kg, i.v.), xylazine (20-80 micrograms/kg, i.v.) and clonidine (2.5-10 micrograms/kg, i.v.) were compared in sheep and cattle housed individually in box stalls. Two alpha 2-adrenergic receptor blocking agents, tolazoline and yohimbine, were administered intravenously for prevention (0.1-0.4 mg/kg) or reversal (0.4-1.2 mg/kg) of these effects. Continuous recording of the reticuloruminal contractions and measurement of the volume of ruminal gas eliminated through the upper respiratory tract indicated that the three alpha 2-agonists inhibited the primary ruminal contractions associated with the reticular contractions. The occurrence of secondary ruminal contractions was also blocked in sheep, but only suppressed in cattle. The inhibition of reticulo-ruminal contractions was prevented or reversed competitively by the two alpha 2-blocking agents, suggesting an alpha 2-adrenoceptor mediation of the inhibition of cyclical motor activity of the reticulo-rumen. In contrast with tolazoline, yohimbine was unable to alleviate the accumulation of gas resulting from inhibition of the secondary ruminal contractions.
Adrenergic alpha-Agonists↗
Pharmacological modulation of postprandial colonic motor activity in the pony.
The contractile activity of the equine large intestine exhibited a biphasic response to feeding: enhancement of migrating complexes passing along the colon and an increase of 50% in cyclic variations in smooth muscle at intervals of 20 min on the left ventral colon for a period of 5 to 7 h postfeeding. The cholinergic agonist, bethanechol (50 micrograms/kg subcutaneously), induced both the migrating complexes and the cyclic variations at intervals of 10-15 min. In contrast, the intra-arterial infusion of PGF2 alpha (3 micrograms/kg/min) increased the contractile activity during infusion, but without inducing distinct patterns of activity. Atropine but not indomethacin or flunixin pre-treatment prevented the effects of postprandial, cholinergic and PGF2 alpha stimulation of colonic motility, suggesting that the gastrocolonic reflex involved mainly cholinergic stimulation of the caecum and replicated colon, including the prostaglandin F2 alpha excitatory effects.
Animals↗
Colonic alpha 2-adrenoceptor-mediated responses in the pony.
The motor responses of the caecum and colon to stimulation of alpha 2-adrenoceptors by xylazine and detomidine at the recommended dose levels of 0.6 and 0.1 mg/kg were investigated in three ponies. The motor changes of the left ventral colon induced by continuous intra-arterial infusion of a prostaglandin (PGF2 alpha) were used to assess the relative inhibitory effects of xylazine and detomidine in a colic model. The administration of alpha 2-agonists inhibited the spiking activity on the whole of the large intestine for 20-30 min (xylazine) or 2-3 h (detomidine). However, the detomidine-induced inhibition was preceded by a short period of increased smooth muscle basal tone as indicated by strain-gauge force transducer measurements. This pattern of activity was neither reversed nor prevented by the administration of tolazoline (10 micrograms/kg/min) intra-arterially. In contrast, inhibition of the colonic phasic and tonic motor activity by alpha 2-adrenoceptor stimulation was reversed competitively by tolazoline. The intra-arterial infusion of prostaglandin F2 alpha (10 micrograms/kg/min) induced prolonged and sustained spiking activity that might be related to signs of mild colic. Detomidine, and to a lesser extent xylazine, relaxed the whole of the large intestine and this was accompanied by alleviation of the signs of visceral pain.
Adrenergic alpha-Agonists↗
Origin of the low pH values along the proximal duodenum in sheep.
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Animals↗
Spinal cord influences on the colonic myoelectrical activity of fed and fasted rats.
1. The myoelectrical activity of the large intestine of fed and fasted rats was recorded with chronically implanted nichrome wire electrodes after destruction of the spinal cord, after spinal cord transection, and after spinal anaesthesia. 2. After spinal cord ablation, the cyclical organization of the colonic electrical spiking activity, as well as the gastrocolic reflex and accompanying postprandial enhancement of the cyclical pattern of activity, persisted on the proximal and distal colon. On the transverse colon, however, the spiking activity was considerably increased. This latter effect obliterated the gastrocolic response due to feeding but not the subsequent postprandial enhancement of the cyclical pattern of activity. 3. After spinal cord transection, the level of spiking activity also increased on both the transverse and distal colon, but no major changes in cyclical activity or in postprandial responses were recorded. 4. Spinal anaesthesia produced by intrathecal lidocaine increased the motility of the transverse colon to a level which masked the gastrocolic reflex. 5. These results suggest a prevertebral ganglia and/or a local control mechanism for the cyclical organization of the spiking activity of the colon. The central control mechanisms involve mostly spinal inhibitory influences on the transverse colon and supraspinal inhibitory influences on the distal colon.
Action Potentials↗
[Diet type, grinding size and anatomo-functional characteristics of the proximal digestive tract in the rabbit].
Two diets containing either dehydrated lucerne (40%) or dehydrated beet pulp (50%) both being coarsely (4 mm) of finely (1 mm) ground before pelleting, were fed to 120 rabbits after weaning. Feed intake and weight gain were estimated. After 79 days, 11 rabbits in each group were slaughtered between 14.00 and 17.00 h. The parameters measured were stomach and ileal weights, dry matter, fibre and nitrogen contents, volatile fatty acid concentrations. Gastric emptying and intestinal transit time were estimated in each group. Rabbits fed the beet pulp diet had a better feed conversion ratio associated with a higher solid matter gastric retention and also a longer jejuno-ileal transit time. Finely ground diet further increased the transit time, particularly in the ileum, which was also associated with a higher concentration of fermentation by-products.
Animal Feed↗
Stimulation and inhibition of food intake in sheep by centrally-administered hypothalamic releasing factors.
Short-term effects of hypothalamic releasing factors on feeding behavior and digestive motility patterns were assessed in hay-fed sheep trained to eat more than half the total amount eaten over 8 h within the first 3 h after food presentation. Thyrotropin-releasing hormone (TRH) given intracerebroventricularly (ICV, 30 ng/kg) or intravenously at higher doses (IV, 3 micrograms/kg) reduced food consumption by 20 p. cent. The ICV or IV TRH-induced reduction was associated with behavioral excitation and stimulation of antroduodenal motor activity without changes in water intake. The ovine corticotropin releasing factor (oCRF 41) decreased food and water intake by 30-50% when administered ICV (60 ng/kg) but was not active when given systemically at doses up to 6 micrograms/kg. The synthetic human growth hormone releasing factor (hGRF 44) administered centrally (60 ng/kg) increased the amount of food intake and the antral motor activity without behavioral excitation. The results indicate a centrally-mediated facilitation of food intake by GRF and its inhibition by CRF which also affect water consumption. The presence of digestive motor effects suggests that extrapituitary pathways may be involved, as for TRH, in the action of both GRF and CRF.
Animals↗
Effect of diet on intestinal xylose absorption in dogs.
The absorption of xylose at different levels of the intestine was compared in five dogs receiving diets containing either wheat bran, polyethylene particles (PE), or horse-bean hulls. The absorption was determined by serial collection of the interstitial fluid (ISF) in different parts of the small intestine and colon, and blood concentration after the administration of D-xylose as a solution (0.5 g/kg body weight) into the duodenal bulb. Xylose was mostly absorbed from the duodenum, and its concentration in the duodenal ISF and in plasma was reduced on a diet containing fiber, irrespective of the nature of fiber. In contrast, a negative linear relation between the mean retention time of digesta in the small intestine and the amount of xylose absorbed by duodenum was evidenced (r = -0.843). The results indicate that changes in transit linked to the presence of fiber in a diet are a major operative factor in the rate of carbohydrate absorption. They suggest that the absorption can be affected by a relatively minor change in the intestinal transit of digesta.
Animals↗
Circadian variation in the propagation velocity of the migrating motor complex.
Using twin intraluminal pressure-sensitive radiotelemetric capsules for prolonged monitoring of proximal small bowel motility in healthy volunteers, we observed a significant (p less than 0.001) variation between daytime (6.44 +/- 0.74 cm/min, mean +/- SD) and nocturnal (2.90 +/- 0.35 cm/min) propagation velocities of the migrating motor complex. An identical variation in propagation velocity was observed in patients suffering from the irritable bowel syndrome. These data suggested a circadian variation, but did not exclude alternative hypotheses. Data were therefore compiled from healthy sheep and pigs supplied with ad libitum rations each morning and adapted to a 12 h light, 12 h dark schedule. Recording from implanted electrodes showed a significant (p less than 0.01) reduction in migrating motor complex velocity from 27.8 +/- 5.1 cm/min by day to 16.7 +/- 3.1 cm/min at night in sheep, and from 20.6 +/- 2.4 to 13.4 +/- 1.9 cm/min in pigs. The nocturnal reduction remained when the animals were fed in the evening. These observations suggest a circadian variation in mammalian migrating motor complex propagation velocity that is not merely a function of variation in intraluminal content.
Animals↗