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Biomedical subjects

C H Malbert

Publications and source records attributed to C H Malbert.

51 records · Page 3Linked to original sources
PubMed1989

[Measurement of changes in parietal tonus of the abomasum in sheep].

An inflatable bag of 250 ml at the pressure of 2 mm Hg inside the abomasal lumen was used to identify the abomasal smooth muscle tone. Reduced tone of the ovine abomasum was assessed, like for the fundic part of the canine stomach, in relation with the cyclic motor activity of the proximal duodenum. Opposite effects were obtained following parasympathomimetic drug injection versus peptides of the gastrin group, suggesting a high responsiveness of the abomasal smooth muscle tone to both neural and hormonal influences.

Abomasum↗
PubMed1988

Gastroduodenal motor activity associated with gastric emptying rate in sheep.

1. Gastric emptying rate was calculated from dye dilution and was measured as the net flow over periods of 5 days through an electromagnetic probe inserted into a T-cannula, 5 cm beyond the pylorus in conscious hay-fed sheep. The net aboral flow was related to the motor activity of the antrum and duodenal bulb which was recorded via chronically fixed strain-gauge transducers. Nichrome wire electrodes were also implanted in order to quantify the electrical activity of the musculature associated with the abomasal outflow in sheep sustained on a liquid diet infused at fixed rates. 2. The abomasal outflow occurred as gushes of 2.1-9.2 ml associated with antroduodenal contractions during 90-95% of the recording time. In the sheep eating 0.7 kg/day hay, the daily outflow of chyme was 5.1 l which increased to 7.5 l of less viscous chyme when the sheep was fed 1 kg/day lucerne hay. During gastric infusion of 3.9 and 7.9 l of the liquid diet, the outflow was 5.7 and 8.3 l/day respectively of low-viscosity chyme propelled as gushes of 5.9-6.9 ml during 95% of the recording time. 3. Increasing the viscosity of the liquid diet with guar-gum caused a reduction in both antroduodenal motility and flow. Dilution of the liquid diet with saline doubled the flow as a result of an increase in the amplitude of the antral contractions. Circadian variations in outflow were also related to concomitant variations in antral motility. 4. It is concluded that the minute-to-minute flow rate of chyme through the pylorus could be satisfactorily measured at the duodenal bulb level and related to the motor activity of the antrum and duodenum. The rate of abomasal outflow depended primarily upon the strength of antral contractions, while the viscosity of the chyme also appeared capable of exerting a major influence on the outflow rate.

Abomasum↗
PubMed1988

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↗
PubMed1988

[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↗
PubMed1987

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↗
PubMed1987

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↗
PubMed1987

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↗
PubMed1987

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↗
PubMed1986

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↗
PubMed1986

Physiological characteristics of ovine pyloric sphincter.

A special probe was validated to record in situ pyloric sphincter activity by changes in fiber-optic light transmission and sleeve pressure associated with the propagation of antroduodenal contractions, the onset of the phase of regular spiking activity (RSA) of the migrating myoelectric complex, the RSA-like events elicited by duodenal acidification, and the pharmacological stimulation of the gastroduodenal junction. Rapid changes in light transmission associated with antroduodenal contractions were super-imposed on slow variations, suggesting the existence of both phasic and tonic components in pyloric sphincter activity. The phasic activity coincided with isolated closures of the pyloric orifice, closures associated with antral or duodenal bulb contractions, and with long-lasting rhythmic closures during the development of the RSA phase. The resting tone increased during antral and/or duodenal stimulation and by feeding "appetizers" but decreased during antroduodenal quiescence and at the onset of general anesthesia. It is concluded that the ovine pylorus predominantly exists in a state of low resting tone but can act as a true sphincter with both inherent tonic and phasic activity.

Animals↗
PubMed1985

[Measurement of transmucosal potential difference before and after gastric mucosal injury in dogs].

Three mongrel dogs (12-14 kg BW) were used to measure the transmucosal gastric potential difference (PD) after gastric injury by electric thermocautery under endoscopic control. The parameters obtained after mathematical fitting of the experimental data to the inverse Batemen function reflected the characteristics, surface and depth of the mucosa injury. These results suggest that a calculated gastric response (GR) is appropriate to evaluate the intensity of gastric mucosal injury.

Animals↗
PubMedDate not supplied

Influence of jejunal nutrients on transpyloric flow and pyloric resistance in pigs.

The effects of small intestinal infusion of nutrients on the transpyloric flow and pyloric resistance were evaluated in anaesthetized pigs. Saline versus isocaloric solutions of dextrose, triglycerides and casein were infused into a jejunal loop during saline gastric loading. Antropyloroduodenal pressures were measured with a sleeve/side-hole manometric assembly and the transpyloric flow with an electromagnetic flowmeter probe. Fundic pressure was maintained constant. Although the overall gastric emptying rate was not affected by nutrients, the stroke volume of the transpyloric flow pulses was significantly increased as a consequence of larger peak flow (dextrose) or longer duration of flow pulses (triglycerides and casein). Pyloric resistance was reduced by all nutrients owing to a change in the temporal relationship between the onset of pyloric pressure events and flow pulses so that flow pulses occurred after pyloric pressure events. In conclusion, under controlled fundic pressure, nutrient infusions decrease pyloric resistance.

Animals↗
PubMedDate not supplied

Proximal gastric distension modifies ingestion rate in pigs.

Control of food ingestion related to proximal gastric distension has never been demonstrated in pigs. The aim of this study was to demonstrate its existence. Meal duration, food intake rate and characteristics of non-ingestion periods were evaluated during the ingestion of a 500 g meal with simultaneous balloon distension of the proximal stomach. Distensions were performed either at fixed pressure levels or at fixed volume levels. Five pressure levels and five volume levels were tested in duplicate experiments in random order and on different days in each animal. Pressures equal or above 11 mmHg increased meal duration (656 +/- 12 vs 562 +/- 30 s, 11 mmHg vs control) because of a lower rate of food intake and longer period of non-ingestion. On the contrary, irrespective of the gastric bag volume, isovolumic distensions did not alter feeding behaviour. We concluded that a short term control of food intake exists in pigs.

Animals↗