Objective:To establish the multidrug resistant animal model of CT26 colon cancercells in mice with the use of chemotherapy. Methods:CT26 colon cancer cells were injected subcutaneously into the right oxters of the mice.Fluorouracil and doxorubicin were combined into chemotherapy.Drown growth curve and calculate doubling generation time,chemotherapeutics drug sensitivity and drug fast index number of the tumor cells before and after chemotherapy were evaluated by MTT method.Levels of MDR1b mRNA were measured by RT-PCR.Eliminate function of P-gp were measured by flow cytometer.Results:Doubling generation time of the persister was higher than the parent cells.Drug resistance indexes were 29.3,26.4,10.9,7.0,5.8,3.0、and 2.8 respectively to ACT,ADM,VCR,HCPT,5-Fu,DAM,and VP16 after chemotherapy and the drug sensitivity were lower.The levels of MDR1b mRNA increased after chemotherapy and P-gp excretive ability was higher than that of no chemotherapy group.Conclusion:The multidrug resistant animal model has established successfully,which provided animal model for our study and research in the acquired multidrug resistance,and established groundwork for the research in increasing the chemotherapy effect.

Objective To investigate the clinical significance of serum citrulline levels in evaluating the remnant bowel absorptive function with enterostomy in the neonatal period by means of tandem mass spectrum so as to guide clinical treatment with parenteral nutrition(PN) or not.Methods The serum amino acid profiles of 30 enterostomy infants including small intestinal enterostomy 17 cases of enterostomy and 13 cases of colon enterostomy and 20 cases of control infants in Wuhan Children's Hospital,Tongji Medical College University of Science & Technology from January 2016 to June 2018 were performed by using tandem mass spectrum,and the related amino acid with the bowel absorbing ability-citrulline was screened out.The Pearson correlation of the serum citrulline levels with the gain weight of the infants was studied.Results The weight of small intestinal enterostomy was significantly lower than colon enterostomy and control infants [(3.22 ± 1.00) kg vs.(5.63 ± 0.66) kg and (6.09 ± 0.85) kg],and there was statistical significance (F =57.23,P ＜ 0.05).Serum citrulline levels were significantly lower in small intestinal enterostomy compared with colon enterostomy and controls [(10.65 ± 5.82) μmol/L vs.(16.57 ± 4.33) μmol/L and (16.52 ± 4.20) μmol/L],and there was statistical significance (F =8.29,P ＜ 0.05).In enterostomy infants serum citrulline was positively correlated with gain weight everyday(r =0.65,P ＜ 0.05).Serum citrulline level ＜ 12 μmol/L had 81.3％ sensitivity and 71.4％ specificity for underweight.Conclusions Serum citrulline is a simple and accurate biomarker for evaluation of the absorptive function and adaptation of the enterostomy infants.Serum citrulline level ＜ 12 μmol/L is a strong predictor of PN-dependence in infants with temporary enterostomy.