[Experimental study of the influence of the segmental transverse colic reversion on the intestinal transit time]. / Etude experimentale de l'impact de l'inversion d'un segment colique transverse sur le transit intestinal.

OBJECTIVE: to study the feasibility of the transverse segment colic reversion and to evaluate its impact on the intestinal transit time in the rat Wistar. METHOD: On a test group of the rats Wistar males anaesthetized, we isolated a segment from the transverse colon vascularized by a feeder pedicle. This segment colic was reversed and anastomosed into antiperistaltic out of termino-terminal on its site with polyglactine 6/0. Into post-operative, we studied, the weight, the volume of the ingestats, the intestinal transit time, the survival and the histological lesions of the reversed segment colic. On the group controls, we carried out the anastomosis of a segment of the transverse colon isolated and anastomosed into isoperisaltic. RESULTS: Thirty rats males of 231.5 +/- 8.3g had been operated, 15 for the test group and 15 for the control group. The average weight of the ingestats of the rats of the test group was of 21.87 +/- 3g and of 21.75 +/- 4.8g in the control group without significant difference. The intestinal transit occured at 3 +/- 1 post-operatives days in the test group and at 2 postoperative days in the control group. A mechanical obstruction of the bowels before the 15th post-operative day involved a mortality of 87% in the test group. Thirteen percent of the rats of the test group survived, with a regular catch of weight. The histological analysis showed inflammatory lesions on the proximal portion of the reversed segment and a normal wall without ischaemic injury on its distal portion. No death was observed in the group controls. CONCLUSION: The antiperistaltic anastomosis of a transverse segment colic within the colic in the rat Wistar, causes a stop of the intestinal transit time by mechanical occlusion without ischaemic lesion of the segment colic reversed.

Microfiltration and ultrafiltration of polysaccharides produced by fermentation using a rotating disk dynamic filtration system.

The recovery of exopolysaccharides (EPS) produced by Sinorhizobium meliloti bacteria by dynamic microfiltration was investigated using a rotating disk device designed in our laboratory, equipped with a 0.2 microm nylon membrane. This system differs from commercially available systems by the presence of vanes on the disk which produce a very important increase in permeate flux while yielding excellent EPS transmission. For polymers produced under standard fermentation conditions (70 h at 30 degrees C), the mass flux rose to 650 g h(-1) m(-2) using a disk equipped with 2 mm vanes rotating at 2000 rpm against 380 g h(-1) m(-2) with a smooth disk at the same speed. The maximum flux observed was 1560 g h(-1) m(-2) with a 6-mm vanes disk rotating at 3000 rpm and a 36 degrees C broth. An interesting finding was that the permeate flux J(f) for various disks can be correlated by the same function of the mean shear stress at the membrane tau(wm) according to J(f) = 4.6 tau(wm) (0.717) for a 30 degrees C broth, showing that the effect of vanes is merely to increase the shear stress by raising the fluid core velocity between the membrane and the disk. With 6-mm vanes the core angular velocity was found to be 84% of disk velocity vs. 45% for a smooth disk. When the fermentation temperature was increased to 36 degrees C to produce a lower molecular weight polymer, the permeate flux rose by about 250%, much more than what could be expected from the reduction in permeate viscosity and followed the same power law with membrane shear stress as for 30 degrees C. The same device was equipped with a PES 50 kDa membrane to concentrate EPS by ultrafiltration. Permeate fluxes were of the order of 160 L h(-1) m(-2) at 2000 rpm and 30 degrees C with nearly complete EPS rejection. Finally, the net electrical power consumed by the disk was measured by subtracting the power consumed without fluid from the power during filtration at the same speed. This power increases with speed and with the presence of vanes, but since the gain provided by the vanes is very high, the specific energy per m(3) of permeate is minimal with the highest vanes tested (6 mm) and maximal for smooth disks.