动物造模,药效评价,溃疡性结肠炎 z-bio 2024-08-26 464

　　(1) Adult rats were immunized four times on the 1st, 10th, 17th, and 24th days using the replication method. The immune substance is a suspension of Escherichia coli cells killed by formaldehyde, with a concentration of 1.2 × 100000000/ml. Preparation method: Take one rat, euthanize it, perform aseptic surgery, streak the colon contents on an eosin methylene blue plate, culture at 37 ℃ for 24 hours, amplify typical bacterial colonies, and perform numerical identification to confirm Escherichia coli. Store in the refrigerator. During the first immunization, 0.2ml of bacterial suspension was subcutaneously injected into the posterior plantar area. For the second and third doses, 0.4ml and 0.6ml were injected subcutaneously at multiple points on the abdomen and back, respectively. For the fourth dose, 1.2ml was injected intraperitoneally. Alternatively, 1.5ml of live Escherichia coli vaccine (same concentration as before) could be administered orally before the second immunization. During the process of immunization with E. coli cell suspension, fecal occult blood was examined every 3 days using conventional methods, lymphocyte transformation rate was measured using morphological methods, and immune circulating complexes were measured using turbidimetric methods. At different time points, appropriate amounts of animal hearts were collected for blood collection, and then euthanized. About 1.0cm long intestinal segments were taken from the middle of the colon, and pathological sections were routinely made and observed under light microscopy.

　　(2) The model features showed that rats immunized with E. coli cell suspension began to exhibit soft stools and mild fecal occult blood positivity in the second week. By the fourth week, all immunized animals showed fecal occult blood positivity. During the continued feeding process, there is a tendency for occult blood to worsen. If live bacteria are added, the model animals will exhibit more severe occult blood. Immune animals began to develop mucous stools from the third week, accompanied by symptoms such as decreased appetite, fatigue, and vertical hair, but no deaths were reported due to colitis. At different times, the lymphocyte transformation rate of model animals was measured, and a significant decrease was found, especially in the group treated with live bacteria, while the circulating immune complex showed an increasing trend with the progression of immunity. Pathological examination showed edema in the mucosa and submucosa of the model animal, infiltration of inflammatory cells, and changes in vasculitis; Multiple crypt abscesses and ulcer formation can be seen within the mucosa; Ulcers can extend deep into the submucosa or serosa, and even form submucosal or subserosal abscesses; As time goes on, the rate of ulcer formation increases; Among them, lesions are more common in the transverse colon and descending colon.

     (3) Comparative medicine currently believes that ulcerative colitis is caused by the interaction of multiple factors, mainly including immune, environmental, dietary, or infectious factors, among which immune factors play an important role in the etiology of ulcerative colitis. Using immunological methods to replicate ulcerative colitis models, the most common immunogens currently include embryonic intestinal tissue, normal colonic mucosa, colonic parasitic strains (Escherichia coli), carrageenan, etc. The antigen used in this experimental method is Escherichia coli, which is a bacterium that normally exists in the intestine. The clinical significance of replicating animal ulcerative colitis using E. coli immunization method lies in demonstrating the correlation between the occurrence and development of ulcerative colitis and the repeated entry of small amounts of bacterial components into the bloodstream due to certain reasons. After immunization with Escherichia coli, ulcers or diffuse inflammation gradually appeared on the colon wall of the model animals, and a decrease in cellular immune function and an increase in circulating immune complexes were observed. The expression of immune function status and the formation of circulating immune complexes are very meaningful as evaluation indicators for immune ulcerative colitis. This model has good application value in the study of the etiology, pathogenesis, and therapeutic drugs of ulcerative colitis due to its simple replication method, convenient antigen source, and modeling mechanism that is closer to the natural pathogenesis process.