| Objective:To establish a successful rat model of experimental aganglionsis by the chemical ablation of colonic ganglion cells,and make good preparation for the second part of this experiment.Methods: Fifty Wistar rats, 8-9 weeks old, were randomly divided into two groups: experiment group (n=25) and control group(n=25). All animals were operated by laparotomy under anesthesia. In experiment group, 0.1% benzalkonium chloride (BAC) solution was applied to the serosal surface of the two-centimeter-long descending colon for 40 minutes. In control group, 0.9% normal saline was applied with as the same method as in experiment group. The observation of general presentations,morphological changes and histologic examination were performed at an interval of 1 week, 2week, 3week, 4week, 5week and 6week after operation by choosing two animals randomly from each group.Results: 1 week after BAC treatment, the rats showed mild abdominal distention. Histologic examinations appeared the degeneration of partial ganglion cells and the trend of reduction of ganglion cells. 2 weeks after BAC treatment, the rats showed moderate abdominal distention and the ganglion cells decreased further. A mildly narrow colonic segment at the segment of BAC treatment could be found. 3 weeks after BAC treatment, the rats showed obvious abdominal distention and the obvious reduction of ganglion cell. Also, a moderately narrow colonic segment and its distended proximal colon could be found. 4-5 weeks after BAC treatment, the rats showed serious abdominal distention, autopsy revealed a obviously narrow colonic segment accompanied by distended proximal colon filled with massive feces. A majority of ganglion cell disappeared. 6 weeks after BAC treatment, the rats showed more serious abdominal distention, autopsy revealed an extraordinary narrow colonic segment and marked dilation of the proximal segment. The ganglion cell disappeared completely.However, compared to experimental group, the control group showed no visible change in clinical symptom,morphological changes and histologic finding at every period of time.Conclusions: The animal model of experimental aganglionosis can be successfully produced in the rat by applying 0.1% BAC to the serosa of descending colon. This model may provide the appropriate animal model for the further study of this experiment in the prevention of Hirschsprung's associated enterocolitis. Also,it will provide the good animal model for further studies on the etiology, pathophysiology and treatment of congenital aganglionosis and its complications in the future. Objective:To study the probability of the preventive effect of bovine colostrums on the occurrence of enterocolitis in the rat model with aganglionic megcolon.Methods: Fifty-six rat models with experimental aganglionosis were established according to the method of the first part of this experiment. They were randomly divided into two groups: experimental group (n=28) and control group (n=28). The rats in experimental group were fed to the pure bovine colostrums solution 30ml each day from the first postoperative day in addition to normal food. The control group were not. The clinical manifestations of enterocolitis were observed after operation. All the rats were killed in order to observe the inflammation from both surface of bowel and histological changing of colon (including the contracted and the proximal dilated segment) at the 5th week of post-operation. The diagnosis of enterocolitis was made by combinating clinical manifestations with histological findings. The incidence of enterocolitis of two groups were summarized and statistical analyzed.Results: Seven rats in experimental group had enterocolitis with the incidence of 25%,15 rats in control group had enterocolitis with the incidence of 53.6%. There was significant difference of the incidence of enterocolitis between two groups (χ2=4.791, P<0.05).Conclusions: Oral taking pure bovine colostrums solution may effectively decrease the occurrence of enterocolitis of rat with experimental aganglionosis. |
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