A. Pousse

Mesenteric vasomotor effects of vasoactive intestinal polypeptide study on perfused isolated canine jejunal loops

SummaryThe vasomotor effect of VIP on the mesenteric vascular bed was studied on isolated canine jejunal loops ex-vivo perfused at normothermia, under pulsatile flow with heparinized, oxygenated and non-recirculating whole blood. VIP has been administered intra-arterially either by 1 min injections or by long term infusions. The results showed that VIP dilates the mesenteric vascular bed. This effect appeared dose dependent up to concentrations of about 5 μg/ml of blood, value for which a maximal vasodepressor effect of 15 mm Hg±6 (S. D.) was reached. Long term infusions of VIP showed an “Escape” phenomenon: the arterial pressure — under constant flow — returned towards the resting level despite continued stimulation. During the vasodilating period induced by the polypeptide, the O2 consumption was increased. Such a response is not necessarily a result of a direct stimulation of specific metabolic processes, but might be related to an extension of the vascular bed by opening capillaries. Concerning the mode of action of the polypeptide, neither propanolol nor atropine were able to suppress the vasodepressor effect of VIP. A neuronal pathway therefore does not seem to be involved. Although, VIP acts directly on the mesenteric vascular bed, the present experimental procedures give no evidence for a significant physiological role of VIP in local regulation of mesenteric haemodynamics. This view is supported by the occurrence of an “Escape” phenomenon as well as by the high arterial concentrations needed for obtaining a significant vasodepressor effect.

Rat intestinal brush border enzymes release by deoxycholate in vivo.

The release of proteins, sucrase (SA), maltase (MA), leucine aminopeptidase (LA) and alkaline phosphatase (AP) activity from rat jejunum by sodium deoxycholate (DOC) was studied by an in vivo perfusion technique.In our experimental conditions, a 2 mmol/l DOC perfusion for 30 min induced a marked and reversible release of proteins and hydrolases. When specific activities were considered, each enzyme showed a distinct release pattern. Significantly, the SA release was largely increased, the AP release was decreased and there was no correlation between the releases of SA and AP. Furthermore, the various enzymes recovered into the lumen were solubilized at different extents. SA was chiefly present in a soluble and AP in a particular form.The microscopical appearances showed a slight exfoliation of the epithelial cells from the villous tips but no specific changes when compared to the control group.The results are discussed in terms of enzymic localization in the brush border membrane; SA would be located very superficially in the surface membrane and AP buried in the membrane and less accessible than the other enzymes.

Effects of Motility and Luminal Distension on Dog Small Intestine Hemodynamics

The effects of spontaneous intestinal motor activity and artificial luminal distension on mesenteric hemodynamics were studied on isolated canine jejunal loops perfused at normothermia under pulsatile

Computer program for intestinal spike bursts recognition

A FORTRAN program has been developed for locating intestinal spike bursts and for estimating their strength. Tested against human scanning, the reliability rate was 92% and the misrecognition rate was 2.5%.This program was applied to the automatisation of the Migrating Myoelectric Complex analysis. A first method computed the percentage of Basic Electrical Rhythm (BER) cycles with superimposed spike bursts. A second one was based on the evaluation of spike bursts strength.

Ex vivo Vascular Perfusion of the Isolated Canine Pancreas

Based on a previous experience of 130 ex vivo canine pancreatic perfusions, a new experimental procedure, dealing with 15 experiments, is reported. Viability and functional response

Computer program for intestinal basic electrical rhythm patterns analysis.

A FORTRAN program has been elaborated for computerized intestinal Basic Electrical Rhythm (BER) analysis. It is based on recognition of individual cycles limits. The reliability of the method was assessed by comparison between computer and visual cycle limits identification.The agreement is 98.2% for BER recorded from the frequency plateau. It is 91.4% for fluctuating BER patterns. For BER frequency computing, draw-backs due to misrecognitions were avoided by cancelling sequences in which they occur.

Effects of Resection on the Electrical Slow Wave in Canine Jejunum

The slow wave (SW) was studied in the dog intestine after a 15 cm long jejunal resection, by means of an automatic method which measures each individual SW cycle duration, the SW mean period and its standard deviation during 3 postoperative weeks. Distal to the site of anastomosis, the SW frequency dropped. 3 weeks after the resection, it was partially restored. The standard deviation increased as well caudad as orad to the anastomosis when compared to control dogs. The differences with the controls were even enhanced with time. These results suggest that the intestinal motility is altered at least during 3 weeks after a jejunal resection.

Do Low Doses of Deoxycholate Modify the Release of Rat Jejunal Brush Border Hydrolases

The in-vivo effects of sodium deoxycholate (DOC) at low concentrations on the release of protein and some brush border hydrolases, sucrease (SA), maltase (MA), leucine aminopeptidase (LA), alkaline phosphatase (AP), have been investigated in the rat by a jejunal perfusion technique. During perfusion with DOC (0.125 or 0.25 mmol/l), enzyme release was not enhanced. After removal of DOC from the perfusion solution with 0.125 mmol/l DOC, there was a steady release of SA, MA and AP although enzyme release was increased linearly in the control and the 0.25 mmo/l DOC groups. The results also confirm the deep localization of AP within the membrane.

A Simple Device to Obtain a Pulsatile Flow

A simple device allowing a pulsatile flow to be obtained in isolated organ perfusion has been developed and applied to the vascular perfusion of isolated canine jejunal segments. The principle of the device consists of superimposing on a constant pressure produced by a roller pump, a pulsatile pressure of which the amplitude, frequency, and shape of the pulses can be adjusted separately and independently of the mean pressure value. The role of the arterial pulse in intestinal vascular perfusion has been studied by comparing the hemodynamic and metabolic behavior during alternate periods of pulsatile and nonpulsatile pumping. While no striking change in vascular resistance was observed, the O2 consumption was significantly increased under pulsatile flow. These results testify to better metabolic conditions and enhanced organ functions under pulsatile pumping and also argue for improved intestinal microcirculation despite the constancy of the vascular resistance.

Simultaneous recording of circular and longitudinal muscle contractions of the canine jejunum.

SummaryA method has been developed for monitoring the mechanical activities of individual longitudinal and circular muscles in a 5 millimeters long segment of intact intestine in the anesthetized dog. The longitudinal contractions were recorded by means of a new movement transducer. The circular contractions were recorded simultaneously using a water-filled intraluminal balloon A precise separation of longitudinal and circular motor activities was obtained with this method. The two muscle layers manifested motor activity most of the time, but their contractions were out of phase. Phase locking was observed only during short periods of time. The contractions were then sequential, the circular one being first.