Differential CI^-and HCO_3^- mediated anion secretion by different colonic cell types in response to tetromethylpyrazine

AIM: Colonic epithelium is known to secrete both CI- and HCO3, but the secretory mechanisms of different colonic cell types are not fully understood. The present study aimed to investigate the differential activation of Cl-and HCO3 secretion by tetramethylpyrazine (TMP) in human crypt-like cell line, T84, and villus-like cell line, Caco-2, in comparison to the TMP-induced secretory response in freshly isolated rat colonic mucosa. METHODS: Colonic epithelial anion secretion was studied by using the short circuit current (Isc) technique. RT-PCR was used to examine the expression of Na^+-HCO3-cotranspoter in different epithelial cell types. RESULTS: TMP produced a concentration-dependent Isc which was increase in both T84 and Caco-2 cells. When extracellular CI was removed, TMP-induced Isc was abolished by 76.6% in T84 cells, but not in Caco-2 cells. However, after both CI and HCO3- were removed, TMP-induced Isc in Caco-2 cells was reduced to 10%. Bumetanide, an inhibitor of Na^+-K^+-Cl-cotranspoter, inhibited the TMP-induced Isc by 96.7% in T84 cells, but only 47.9% in Caco-2 cells. In the presence of bumetanide and 4, 4'-diisothiocyanostilbene-2, 2'-disulfonic acid, an inhibitor of Na^+-HCO3- cotransporter, inhibited the TMP-induced current in Caco-2 cells by 93.3% .In freshly isolated rat colonic mucosa, TMP stimulated distinct Isc responses similar to that observed in T84 and Caco-2 cells depending on the concentration used. RT-PCR revealed that the expression of Na^+-HCO3- cotransporter in Caco-2 cells was 4-fold more greater than that in T84 cells. CONCLUSION: TMP exerts concentration-dependent differential effects on different colonic cell types with stimulation of predominant Cl- secretion by crypt cells at a lower concentration, but predominant HCO3- secretion by villus cells at a higher concentration, suggesting different roles of these cells in colonic Cl and HCO3 secretion.

Improvement of barrier function and stimulation of colonic epithelial anion secretion by Menoease Pills

AIM: Menoease Pills(MP)1 a Chinese medicine-based new formula for postmenopausal women, has been shown to modulate the endocrine and immune systems. The present study investigated the effects of MP and one of its active ingredients, ligustrazine, on epithelial barrier and ion transport function in a human colonic cell line, T84.METHODS: Colonic transepithelial electrophysiological characteristics and colonic anion secretion were studied using the short circuit current (Isc) technique. RT-PCR was used to examine the expression of cytoplasmic proteins associated with the tight junctions, ZO-l(zonula occludens-1) and ZO-2 (zonula occludens-2).RESULTS: Pretreatment of T84 cells with MP (15 μg/mL) for 72 h significantly increased basal potential difference,transepithelial resistance and basal ISC. RT-PCR results showed that the expressions of ZO-land ZO-2 were significantly increased after MP treatment, consistent with improved epithelial barrier function. Results of acute stimulation showed that apical addition of MP produced a concentrationdependent (10-5 000 μg/mL, EC50 = 293.9 μg/mL) increase in ISC. MP-induced ISC was inhibited by basolateral treatment with bumetanide (100 μmol/L), an inhibitor of the Na^+-K^+-2Cl^- cotransporter, apical addition of Cl^- channel blockers, diphenylamine-2, 2'-dicarboxylic acid (1mmol/L) or glibenclamide (1 retool/L), but not 4, 4'-diisothiocyanostilbene-2, 2'-disulfonic acid or epithelial Na+ channel blocker,amiloride. The effect of MP on ZOo1 and ZO-2was mimicked by Ligustrazine and the ligustrazine-induced ISC was also blocked by basolateral application of bumetanide and apical addition of diphenylamine-2, 2'-dicarboxylic acid or glibenclamide, and reduced by a removal of extracellular Cl^-.CONCLUSION: The results of the present study suggest that MP and lligustrazine may improve epithelial barrier function and exert a stimulatory effect on colonic anion secretion, indicating the potential use of MP and its active ingredients for improvement of GI tract host defense and alleviation of constipation often seen in the elderly.

CpG ODN Enhances Immunization Effects of Hepatitis B Vaccine in Aged Mice

Oligodeoxynucleotides(ODN)containing unmethylated CpG dinucleotides in contexts of unique sequence (CpG motifs)is active as adjuvant in induction of cellular and humoral immune responses in young mice.To date,there are only limited reports about effect of CpG ODN on immune responses against hepatitis B(HB) infection in aged mice.Our studies demonstrated there were significant increases in secreting of total anti-HB IgG,IgG1 and IgG2a,as well as of IL-12 and IFN-γ,when CpG ODNs were injected together with hepatitis B antigen in aged mice.Moreover,CpG ODN could stimulate proliferation of spleen lymphocytes in a dose-dependent manner.Taken together,the results we obtained indicate that the adding of CpG ODN into the vaccine antigen might be useful in development of more effective vaccination for inducing anti-HB virus responses in the elderly.Cellular & Molecular Immunology.2004;1(2):148-152.

CHOOSING STRUCTURE-DEPENDENT DRAG COEFFICIENT IN MODELING GAS-SOLID TWO-PHASE FLOW

IntroductionGas-solid two-phase flow is often encountered in chemical reactors for the process industry. For industrial users, design, scale-up, control and optimization for these reactors require a good understanding of the hydrodynamics of gas-solid two-phase flow. For researchers, exploration and prediction of the complex phenomena call for a good comprehension of the heterogeneous structure and of the dominant mechanisms of gas-solid and solid-solid interactions.

Study of material agglomeration during nozzle injection of multiviscosity liquid into a fluidized bed reactor by the electric conductance method

Fluidized bed agglomeration is an important and challenging problem for thermal cracking in fluid cokers. A low coker temperature can be problematic because the bitumen is injected into the fluidized bed with a different viscosity, resulting in formation of agglomerates of varying sizes, which slows the cracking reactions. In the present study, the bed material agglomeration process during nozzle injection of multi- viscosity liquid was investigated in a fluidized bed operated at different mass ratios of the atomization gas to the liquid jets （GLR= 1%-3.5%） and gas velocities （3.9Umf and 5,9Umf） based on a conductance method using a water-sand system to simulate the hot bitumen-coke system at room temperature. During the tests of liquid-jet dispersion throughout the bed, different agglomeration stages are observed at both gas velocities. The critical amount oftert-butanol in the liquid jets that could lead to severe agglomeration of the bed materials （poor fluidization） at GLR = 1% is about 10 wt% at the low fluidizing gas velocity （3.9Umf） and 18wt% at the high gas velocity （5,9Umf）. This study provides a new approach for on-line monitoring of bed agglomeration during liquid injection to guarantee perfect contact between the atomized liquid and the bed particles.