Hans-Jörg Ehrlein

Postprandial patterns of canine jejunal motility and transit of luminal content

The effects of different nutrient meals and a noncaloric viscous cellulose meal (control) on the motor activity of the canine jejunum were studied. Contraction patterns were detected through six closely spaced, strain-gauge transducers and were analyzed by a computer. Luminal transit was assessed videofluoroscopically. Control meals moved rapidly (1.9 cm/s) along the jejunum. This was achieved by contractions that occurred at a high frequency (12.8 cpm) and propagated over long distances (9.9 cm). In contrast, the transit rates of the nutrient meals were considerably slower (0.5-1.0 cm/s), the frequency of contractions (5.0-8.9 cpm) and the length of spread of contraction waves (2.6-4.8 cm) were decreased, and the incidence of stationary contractions occurring individually or in clusters was increased. A mathematical model incorporating frequency of contractions and the length of their propagation was used to predict the transit of jejunal contents. The results of correlation tests and of the mathematical model revealed that the length of spread of contraction waves was the most important factor that influenced transit.

Effects of enteral feedback inhibition on motility, luminal flow, and absorption of nutrients in proximal gut of minipigs.

We wanted to clarify whether the postprandial intestinal feedback control activated by nutrients in the distal gut exerts different effects on motility, transit of digesta, and absorption of nutrients in the proximal gut. Additionally, interrelationships among motility, transit, and absorption were to be elucidated because these relationships have only been investigated in the fasted state. In five minipigs, a 150-cm segment of the proximal jejunum was isolated by two cannulas. Motility of the jejunal segment was recorded by multiple strain gauges and analyzed by computerized methods. Markers (Cr- and Cu-EDTA) were used for the measurement of the flow rate, transit time, and absorption of nutrients. After a meal, the test segment was perfused with 2 kcal/min of an elemental diet over a period of 90 min. A feedback inhibition was activated by infusion of nutrients into the midgut at rates of 1–4 kcal/min. Saline was infused as control. With increasing energy loads infused into the midgut, the motility index and the length of contraction waves decreased, whereas the incidence of stationary contractions increased, ie, the motility changed from a propulsive to a segmenting pattern. These modulations of motility were associated with a linear decrease in the flow rate and a linear increase in transit time. Flow and transit were linearly correlated with each other. Additionally, the reduction in flow rate and the delay in luminal transit were associated with a linear increase in the absorption of nutrients. However, the increase in absorption induced by the feedback mechanism was small (7.3–13.4%) compared to the marked inhibition of the motility parameters (54–64%), the flow rate (59%), and the delay of transit (5.8-fold). Feedback control primarily modulated motor patterns and luminal flow, whereas the small increase in absorption was only a side effect due to the longer contact time of the nutrients with the mucosa.

Characteristics of postprandial duodenal motor patterns in dogs

In this study special attention was paid to the characteristics of duodenal motility under the influence of various test meals. Closely spaced strain gauge transducers and a computerized method were used to analyze motor patterns of the duodenum and the adjacent jejunum. Compared with an acaloric meal, nutrients shortened the length of contraction spread in the duodenum from 5.2±1.0 to 3.8±0.5−2.8±0.6 cm and in the jejunum from 10.5±3.0 to 7.4±1.3−5.2±0.8 cm. Additionally, contraction frequency was reduced. Basic differences were found between duodenal and jejunal motility. They were most marked in absence of nutrients. The duodenal motor pattern was characterized by a lower contraction frequency (8.0±2.2 vs 11.1±1.8/min), a shorter length of contraction spread (5.2±1.0 vs 10.5±3.0 cm), and a higher incidence of stationary contractions (50% vs 34%). On the duodenal bulb 72% of contractions represented contraction waves, whereas in the mid-duodenum the predominant feature was stationary contractions (57%) promoting the mixing of chyme with secretions. The characteristic duodenal motor patterns might be related to special functions of the duodenum for transport and digestion.

Relationships between gastric emptying and intestinal absorption of nutrients and energy in mini pigs

Little is known about the relationship betweengastric emptying of nutrients regulated by feedbackmechanisms and the absorptive capacity of the gut.Therefore, we wanted to elucidate theseinterrelationships. A 150-cm jejunal segment was perfused (1-8kcal/min) with three different nutrient solutions(either 60% of energy as carbohydrate, or 60% asprotein, or 33.3% of each nutrient). In separateexperiments, gastric emptying was measured afteradministration of three different meals with the samenutrient composition as the perfusion solutions. Thejejunal absorption of carbohydrate, protein, fat, andenergy demonstrated saturation kinetics. The kineticsdiffered among the three nutrients; carbohydrates wereabsorbed at higher rates than fat and protein.Interactions among the nutrients altered the kinetics providing a constant absorption of energy.After meals, the stomach emptied equal amounts of energydespite large variations in meal composition. Theavailable intestinal absorptive capacity for protein was utilized by 96%, whereas that forcarbohydrate, fat and energy were utilized only by46-62%. Besides reserves in the absorptive capacity, theintestine provided reserves in total length available for absorption. The results indicate a closerelationship between the energy-dependent absorption ofnutrients and the energy-dependent feedback inhibitionof gastric emptying.

Gastric emptying after roux-y and billroth-I gastrectomy depends on viscosity of meal and contractile patterns of small intestine in dogs

The aim of the study was to examine gastrointestinal motility after distal gastrectomy and the influence of meal viscosity on gastric emptying. Gastrointestinal motility and gastric emptying of acaloric meals with different viscosities were measured in normal dogs and after a two-thirds gastrectomy with Billroth-I or Roux-Y gastroenterostomy. After distal gastrectomy, gastric emptying depended on the viscosity of the meal, as in normal dogs. Acaloric viscous meals emptied significantly faster in the Billroth-I than in the Roux-Y group due to different contractile patterns of the duodenum and jejunum. In comparison to normal dogs, gastric emptying of viscous meals was accelerated in the Billroth-I and delayed in the Roux-Y group. Several motility parameters of the stomach and intestine differed between the normal and gastrectomized dogs. Thus, after distal gastrectomy, the viscosity of the meal and the contractile patterns of the small intestine are important determinants of gastric emptying.

Computerised method for pattern recognition of intestinal motility: Functional significance of the spread of contractions

The intestinal motility consists of local and propagative contractions. A system for determining the length of spread of intestinal contractions has been developed. The technique used for waveform recognition was based on the principle of peak detection. A computer program analysed the length of spread of contractile waves, their mean contractile force and their mean propagation velocity. The computer identified each waveform on the basis of pre-established threshold and timing criteria. A technique for fitting theoretical equations to experimental data (measured transit rate of ingesta against evaluated parameters) was used to prove the functional significance of the contractile patterns. The method provides a more detailed representation of contractile patterns than other studies based on the conventional methods of analysis.

Mechanical characteristics of phase II and phase III of the interdigestive migrating motor complex in dogs

In conscious dogs certain parameters of the jejunal interdigestive phase II and phase III activity were studied by means of closely spaced strain gauges and videofluoroscopy. During phase III the frequency, force, and rise time of contractions and the contraction spread were increased, whereas the intercontractile intervals and the propagation velocity of contractions were diminished in comparison to phase II. The contraction waves of phase III were variable with regard to their length of spread and their rate of caudad migration. These two parameters adjusted the duration, the propagation velocity, and the length of the activity front. Propagation of contractions was sometimes interrupted by periods of uncoupling. Propagation velocities within contraction waves varied according to the pattern slow-fast-slow-fast, producing the videofluoroscopically observed roller coaster movements of the luminal contents. It is concluded that phase II and phase III are characterized not only by the occurrence of irregular and regular activity but by a significant change of a number of contraction parameters.

Effects of enteral infusion of hypertonic saline and nutrients on canine jejunal motor patterns.

The aim of the study was to clarify the effects of hypertonic solutions on jejunal motility. The study focused on differential effects of hypertonic saline and nutrients. Motility of the canine proximal jejunum was recorded with closely spaced strain-gauge transducers. During fasting, hyperosmotic solutions (up to 1520 mosmol/liter) of saline or nutrients (1 kcal/ml) were infused into the proximal jejunum (0.5–1.5 ml/min) up to 6 hr. The hyperosmotic solutions stimulated jejunal motility. With both increasing osmolarity of saline or increasing energy load of nutrients, jejunal motility linearly declined. The reduction of motility was associated with a change in motor pattern from a propulsive to a more segmenting one. Hypertonic glucose evoked a significantly smaller level of motor activity compared with both saline (at given osmolarities) and an elemental diet (at given energy loads). Motility parameters were not different between glucose and maltose, although osmolarity of maltose was less than half (760 vs 1520 mosmol/liter). In contrast, a mixture of glucose-fructose exerted a smaller inhibition of jejunal motility than glucose. The hypertonic solutions of saline or nutrients were tolerated over 2 hr; with hypertonic saline retrograde power contractions with or without vomiting occurred, whereas with hypertonic nutrients vomiting was preceded by strong inhibition of jejunal motility. Three conclusions can be derived from the present results: (1) The behavior of jejunal motility suggested that the motor activity was the result of both a local stimulation and an inhibitory feedback mechanism. (2) The different degree of inhibition between glucose and saline indicated that the nutrient itself played a major role in the inhibitory feedback regulation, whereas osmolarity was of minor importance. (3) Comparisons between different nutrients suggested a linkage between inhibitory control of motility and the absorptive capacity of the gut for the single nutrient.

Effects of neurohormonal agents on jejunal contraction spread and transit in the fed dog

The jejunal contraction patterns of dogs in response to intravenous infusion of neurotensin, somatostatin, secretin, and met-enkephalin were analyzed. The peptides were given after administration of a noncaloric viscous cellulose meal. A computer was used to determine the length of spread of contraction waves, their contraction force, the contraction frequency, and the motility index. Transit rates of luminal content were assessed videofluoroscopically. During saline infusion the cellulose meal was propelled aborally at a transit rate of 3.1 +/- 1.1 cm/s; the corresponding length of spread of contraction waves was 10.3 +/- 1.5 cm. All peptides decreased both the transit rate (0.45-1.81 cm/s) and the contraction spread (3.7-6.2 cm). Neurotensin increased the contraction force, but had no effect on contraction frequency and motility index. The other peptides reduced the motility index and the frequency and force of contractions. It was shown that the peptides influenced intestinal contraction patterns and the transit rate of luminal content. The length of spread of contraction waves was found to be most important in the regulation of transit.

Effects of nutrients on gastrointestinal motility and gastric emptying after distal gastrectomy with Roux-Y gastrojejunostomy in dogs

The aim of the study was to clarify whether nutrients are still capable of slowing gastric emptying following Roux-Y gastrectomy, as in normal dogs. Gastrointestinal motility and gastric emptying of acaloric and nutritive meals with different viscosities were measured in normal dogs and after a two-thirds Roux-Y gastrectomy. In gastrectomized dogs low-viscosity nutritive meals emptied unduly rapidly in an initial phase, although the frequency and spread of contractions, ie, the propulsive activity of the jejunal Roux limb were diminished. A slow emptying rate during the following period was due to a long-lasting inhibition of gastric and jejunal motility. Medium-viscosity nutritive meals emptied in gastrectomized dogs as slowly as in normal animals, but this effect was primarily caused by the meal viscosity and only secondarily by the nutrients. It is concluded that following Roux-Y gastrectomy a regulation of gastric emptying is preserved; however, the onset of an effective control is delayed, resulting in a rapid initial emptying of low-viscosity meals.