Charles Henri Malbert

Diet-related adaptation of the small intestine at weaning in pigs is functional rather than structural.

Background Incidence of diarrhea at weaning in commercial pigs is an important problem, and diet is thought to be a predisposing factor. The aim of this study was to determine the impact of switching from milk-based to cereal-based diets on the morphology and function of the small intestine of piglets using a model of delayed weaning to isolate the influence of the diet from that of environmental and social factors. Methods Forty-five piglets received a milk-based diet for 5 weeks after weaning. Thirty piglets were then switched from milk-based to wheat- or barley-based diets, mimicking the dietary change that occurs at weaning. The last 15 piglets remained on the milk-based diet. Piglets were killed 4 days after the dietary switch. Jejunal mucosa morphometry and enzyme activities were measured. Ussing chambers were used to measure intestinal permeability to macromolecules, basal electrical properties, glucose absorption, and induced chloride-secretion. Results Alkaline phosphatase– and sucrase-specific activities were higher in both groups of cereal-fed piglets than in milk-fed piglets. Dipeptidylpeptidase IV activity was higher in wheat-fed piglets than in the other groups. Na+-dependent glucose absorption was 1.7-fold higher in cereals-fed piglets than in milk-fed piglets. Serotonin-induced and vasoactive intestinal polypeptide–induced chloride secretion was doubled in cereals-fed piglets. Dietary transition did not influence the other parameters. Conclusions These results indicate that switching from milk to cereals increased some mucosal enzyme activities, intestinal Na+–dependent glucose absorption, and response to secretagogues. This supports the hypothesis that dietary factors could initiate diarrhea in the presence of other aggravating factors, such as pathogens or environmental stress.

Effects of duodenal distention on fasting and postprandial antropyloroduodenal motility in humans

BACKGROUND/AIMS Mechanoreceptors in the proximal small intestine may play an important role in the regulation of gastric emptying. Balloon distention of the duodenum causes fundic relaxation. The purpose of the present study was to determine the effect of stimulation of duodenal mechanoreceptors on both fasting and postprandial antropyloroduodenal motility in humans. METHODS Antropyloroduodenal pressures were recorded in 12 healthy volunteers with a sleeve-sidehole assembly, incorporating two balloons 5 and 20 cm distal to the pylorus. Duplicate proximal and distal duodenal balloon distensions with 10, 20, and 30 mL of air for 2.5 minutes were performed separately and in randomized order both during fasting and after a meal. RESULTS During fasting, proximal and distal distention at all volumes increased the number of isolated pyloric pressure waves (P < 0.05) and basal pyloric pressure (P < 0.05), and the response to proximal distention was greater (P < 0.05). Postprandially, proximal and distal distention increased basal pyloric pressure (P < 0.05) with a greater response to proximal distention (P < 0.05), but had no effect on isolated pyloric pressure waves. Both during fasting and postprandially, there were more synchronous and less antegrade antral waves during distention (P < 0.05). The number of duodenal pressure waves increased during proximal (P < 0.05) but not distal distention. CONCLUSIONS Stimulation of duodenal mechanoreceptors by balloon distention has significant and region-dependent effects on antropyloroduodenal motility that vary between fasting and postprandial states.

Effect of an abrupt switch from a milk-based to a fibre-based diet on gastric emptying rates in pigs: difference between origins of fibre

A characteristic dietary feature at weaning is a switch from a milk-based to plant-based diet, i.e. from a non-fibrous to a fibrous diet. The present study aimed to evaluate the effects of such an abrupt dietary switch on gastric emptying rate in pigs maintained on a milk substitute after weaning. Eighteen piglets were kept on a milk substitute for 5 weeks after weaning and were then switched to wheat-based or barley-based diets or kept on the milk substitute (six piglets per group). All piglets were fasted for 1 d before the switch and daily food intake was then increased linearly to reach initial values within 3 d. The gastric emptying rate was measured by gamma-scintigraphy before and after the switch. Corpo-antral peristalsis was also evaluated by the use of high-frequency scintigraphic frames. The gastric emptying rate of the wheat-based diet was accelerated on days 1 to 3 after the switch, but was similar to that in the milk-substitute group thereafter. This acceleration was concomitant with an enhanced frequency of corpo-antral waves on days 2 and 3. Conversely, the gastric emptying rate of the barley-based diet tended to be enhanced on day 2, but was delayed on days 4 and 5, without any change in frequency of corpo-antral waves. We conclude that a switch from a non-fibrous to a fibrous diet alters the gastric emptying rate differently depending on the type of dietary fibre.

Exposures to Conditioned Flavours with Different Hedonic Values Induce Contrasted Behavioural and Brain Responses in Pigs

This study investigated the behavioural and brain responses towards conditioned flavours with different hedonic values in juvenile pigs. Twelve 30-kg pigs were given four three-day conditioning sessions: they received three different flavoured meals paired with intraduodenal (i.d.) infusions of 15% glucose (FGlu), lithium chloride (FLiCl), or saline (control treatment, FNaCl). One and five weeks later, the animals were subjected to three two-choice feeding tests without reinforcement to check the acquisition of a conditioned flavour preference or aversion. In between, the anaesthetised pigs were subjected to three 18FDG PET brain imaging coupled with an olfactogustatory stimulation with the conditioned flavours. During conditioning, the pigs spent more time lying inactive, and investigated their environment less after the FLiCl than the FNaCl or FGlu meals. During the two-choice tests performed one and five weeks later, the FNaCl and FGlu foods were significantly preferred over the FLICl food even in the absence of i.d. infusions. Surprisingly, the FNaCl food was also preferred over the FGlu food during the first test only, suggesting that, while LiCl i.d. infusions led to a strong flavour aversion, glucose infusions failed to induce flavour preference. As for brain imaging results, exposure to aversive or less preferred flavours triggered global deactivation of the prefrontal cortex, specific activation of the posterior cingulate cortex, as well as asymmetric brain responses in the basal nuclei and the temporal gyrus. In conclusion, postingestive visceral stimuli can modulate the flavour/food hedonism and further feeding choices. Exposure to flavours with different hedonic values induced metabolism differences in neural circuits known to be involved in humans in the characterization of food palatability, feeding motivation, reward expectation, and more generally in the regulation of food intake.

Functional Role of the Equine Ileocecal Sphincter

Recordings of intraluminal pressure at the equine ileocecal junction indicate the presence of a high‐pressure zone of about 6 mm Hg over a distance of 5 cm. Both cecal distention by air and acidification of cecal contents by short‐chain fatty acids elicited bursts of phasic pressure waves at the ileocecal junction. Phasic contractions contributed to the concomitant increase of tone at the ileocecal junction. Reflux of acidic cecal contents into the ileum was immediately counteracted by propagated phasic contractions. It appears that contractions propagated toward the cecum, rather than stationary contractions, contribute to the sphincteric properties at the ileocecal junction. The patterns of motor activity of the ileocecal region in species with a well‐developed cecum suggest the additional presence of numerous propagated contractions of cecal origin.

Vagal Influences on the Phasic and Tonic Components of the Motility of the Ovine Stomach and Gastroduodenal Area

Both the phasic and tonic components of gastric motility including the gastroduodenal junction were recorded after section or cooling blockade of the vagus nerves in conscious sheep. The phasic contractile activity was monitored using electromyography, strain gauges, and intraluminal manometry. The changes in the tone of the stomach (abomasum) were assessed by an electronic barostat. The cyclical contractions of the reticulorumen ceased immediately after bilateral vagotomy, whereas the activity of the antral part of the abomasum was strongly enhanced. Two weeks after vagotomy, the abomasal hypermotility persisted while reticuloruminal movements developed from a local nervous network. Vagal cooling at 5°C of one of the vagus nerves after section of the contralateral vagus similarly inhibited reticuloruminal contractions in contrast to the occurrence of abomasal hypermotility. During vagal cooling, both the abomasal and pyloric tone were lowered. We conclude that vagal cooling impairs excitatory input to the reticulorumen and inhibitory input to the gastroduodenal junction. The decreased smooth muscle tone at the abomasal and pylorus levels during vagal cooling suggests that vagal stimulatory influences are abated.

Duodenal pH dips as an index of transpyloric flow in conscious dogs

BACKGROUND To determine if duodenal pH fluctuations might be used as a valuable index of the occurrence of gastric chyme ejection, the transpyloric flow and pH in the duodenal bulb were monitored simultaneously in six dogs. METHODS Transpyloric flow, monitored by a chronically implanted electromagnetic flowmeter, was represented by individual pulses of flow. Relations between the volume of these flow pulses and changes in duodenal pH were assessed both postprandially and during the increased gastric outflow that followed gastric loading of buffered saline solutions at pH 2 and 4. RESULTS During fasting and gastric loading with buffered saline at pH 2, no consistent relationship between flow pulses and duodenal pH fluctuations was evident. After instillation of buffer solution at pH 4 and postprandially, the magnitude of duodenal pH fluctuations became proportional to the stroke volume of the flow pulses. The removal of bile from the proximal duodenum decreased the relationship. CONCLUSIONS It is concluded that duodenal pH measured at 2 cm from the pylorus might be used postprandially as an index of the transpyloric flow rate of chyme.

Antral compensation after proximal gastric vagotomy

Proximal gastric vagotomy (PGV) has little impact on the normal pattern of solid gastric emptying, despite denervation of the proximal two thirds of the stomach and loss of the proximal gastric pump. In four healthy volunteers and four patients with PGV, we investigated the possible compensatory mechanisms that may come into play after proximal denervation of the stomach. We measured antropyloroduodenal motility with a 10-lumen sleeve/side-hole catheter for 180 minutes after ingestion of a dual-isotope radiolabeled mixed liquid/solid meal. Patients with PGV exhibited faster liquid emptying, but the rate of solid emptying was similar to that in healthy volunteers. The frequency of propagated antropyloric pressure waves was similar between the two groups, but patients with PGV exhibited less isolated pressure waves in the proximal antrum. The amplitude and duration of pressure waves recorded in the distal antrum were significantly increased in the PGV patients as compared to healthy volunteers. Although the pattern of propagated antral contractions and solid gastric emptying remains unchanged after PGV, there is an increase in the amplitude and duration of distal antral contractions, which may compensate for loss of proximal gastric pumping mechanisms.