Objective To investigate the specific pathogenesis of O-antigen polysaccharide(OPS) which is a subunit component of lipopolysaccharide(LPS) from enteroinvasive Escherichia coli. Methods The OPS was extracted and purified from Escherichia coli O29(enteroinvasive E.coli) strain. Effects of OPS, contrasted with the whole LPS molecule, were observed by in vitro experiments (HeLa cell culture) and in vivo experiments (rabbit ileal loop assay). Results It was revealed that the purified EIEC OPS alone cause cytopathic effect to HeLa cell, and that the OPS caused mucosal hemorrhage, but no fluid accumulation in ileal loop of rabbits. The scanning electron microscope and transmission electron microscope demonstrated the fine structures of cytopathic HeLa cell were damaged. Conclusion Escherichia coli O29 OPS might be one of the factors causing diarrhea and its mechanism was different from endotoxin reaction of LPS. Escherichia coli O29(pathogen) OPS showed a marked serious toxicity as compared with Escherichia coli HB101(nonpathogen) OPS.

Objective To explore the distribution of the liquid food in the stomach of patients with postprandial distress syndrome (PDS)-predominated functional dyspepsia (FD)and the mechanism of its gastric dynamic dysfunction.Methods Fifty-two patients with PDS and 18 healthy volunteers underwent gastric emptying examination with ultrasound scanner provided.The proximal and distal gastric area and volume,area and volume ratio of proximal and distal gastric as well as emptying rate of proximal and distal gastric were calculated at fasting,maximum satiety,30 min,60 min,90 min and 120 min after meal. Student′s t test andχ2 test were performed for statistical analysis.Results Proximal gastric volume of PDS group at the time of fasting and 120 min after meal were (9.06±7.88)and (24.72±24.02)cm3 ,which were larger than those of healthy control group ((5 .96 ± 2.13 )cm3 ,(19.48 ± 12.32 )cm3 ),and the differences were statistically significant (t=-1 .637 and -0.875 ,both P <0.05).Ratio of proximal and distal gastric area at maximum satiety in PDS group was 1 .63±0.42 and that in healthy control group was 2.33±0.63,and the difference was statistically significant (t =5 .044,P <0.05 ).Ratio of proximal and
distal gastric volume in PDS group and healthy group at fasting was 0.60 ± 0.38 and 0.46 ± 0.19, respectively,that at maximum satiety was in PDS group and healthy group 0.91 ±0.27,1 .30 ±0.48, respectively,and the differences were statistically significant (t = - 1 .505 and 3.970,both P <0.05). The emptying rates of proximal stomach of PDS group at 30 min and 90 min postprandial were (28.10 ± 25 .03)% and (68.80±16.14)%,respectively,those of healthy control group were (34.97 ±14.41 )%and (75 .86 ±9.86)%,and the differences were statistically significant (t =1 .087 and 1 .718,both P <0.05).There was no statistically significant difference in emptying rate of distal stomach between two groups (all P > 0.05 ).Conclusions The volume of distal stomach was larger than that of proximal stomach in PDS patients at maximum satiety in liquid food distribution,which may be the cause of decreasing emptying rate of proximal stomach.And proximal stomach dominated gastric motility in PDS patients.