Different cell kinetic changes in rat stomach cancer after treatment with celecoxib or indomethacin: Implications on chemoprevention

AIM: Mechanisms underlying the chemopreventive effects of cyclooxygenase (COX) inhibitors remain elusive. We have previously shown that celecoxib but not indomethacin could prevent carcinogen-induced gastric cancer development in Wistar rats. This chemopreventive effect appeared to be independent of COX-2 and prostaglandin (PG) E2 suppression since the lowest PGE2 was obtained in indomethacin group.This study compared the cell kinetic changes in stomachs of rats after treatment with celecoxib (5, 10, 20 mg/(kg·d)) or indomethacin (3 mg/(kg·d)) to gain more insights into the chemopreventive mechanism.METHODS: The apoptosis and proliferation indexes in gastric tumor, adjacent non-cancer tissues and normal gastric tissues were determined. Apoptosis was quantified by apoptotic nuclei counting and TUNEL, whereas proliferation was determined by Ki67 immunostaining.RESULTS: Treatment with either celecoxib or indomethacin inhibited gastric tumor proliferation by more than 65% (P＜0.02). However, celecoxib caused a dose-dependent increase in apoptosis (P＜0.05) which was not seen in indomethacin-treated tumors (P = 0.54). The highest apoptosis to proliferation ratio was seen in tumors treated with celecoxib at 10 mg/(kg·d). Treatment with this dose of celecoxib was associated with the lowest incidence of gastric cancer development.CONCLUSION: Our findings suggest that the difference in chemopreventive effects of indomethacin and celecoxib in this animal model of gastric carcinogenesis is largely due to the differential cell kinetic changes, which does not correlate with the degree of COX-2 and PG suppression.

Combined modeling of cell aggregation and adhesion mediated by receptor–ligand interactions under shear flow

Blood cell aggregation and adhesion to endothelial cells under shear flow are crucial to many biological processes such as thrombi formation, inflammatory cascade, and tumor metastasis, in which these cellular interactions are mainly mediated by the underlying receptor-ligand bindings. While theoretical modeling of aggregation dynamics and adhesion kinetics of interacting cells have been well studied separately, how to couple these two processes remains unclear. Here we develop a combined model that couples cellular aggregation dynamics and adhesion kinetics under shear flow. The impacts of shear rate （or shear stress） and molecular binding affinity were elucidated. This study provides a unified model where the action of a fluid flow drives cell aggregation and adhesion under the modulations of the mechanical shear flow and receptor-ligand interaction kinetics. It offers an insight into understanding the relevant biological processes and functions.

Electrochemical Properties of Electrodes with Different Shapes and Diffusion Kinetic Analysis of Microbial Fuel Cells on Ocean Floor

Microbial fuel cell(MFC) on the ocean floor is a kind of novel energy-harvesting device that can be developed to drive small instruments to work continuously.The shape of electrode has a great effect on the performance of the MFC.In this paper,several shapes of electrode and cell structure were designed,and their performance in MFC were compared in pairs:Mesh(cell-1) vs.flat plate(cell-2),branch(cell-3) vs.cylinder(cell-4),and forest(cell-5) vs.disk(cell-6) FC.Our results showed that the maximum power densities were 16.50,14.20,19.30,15.00,14.64,and 9.95 mWm-2 for cell-1,2,3,4,5 and 6 respectively.And the corre-sponding diffusion-limited currents were 7.16,2.80,18.86,10.50,18.00,and 6.900 mA.The mesh and branch anodes showed higher power densities and much higher diffusion-limited currents than the flat plate and the cylinder anodes respectively due to the low diffusion hindrance with the former anodes.The forest cathode improved by 47% of the power density and by 161% of diffusion-limited current than the disk cathode due to the former's extended solid/liquid/gas three-phase boundary.These results indicated that the shape of electrode is a major parameter that determining the diffusion-limited current of an MFC,and the differences in the elec-trode shape lead to the differences in cell performance.These results would be useful for MFC structure design in practical applica-tions.

KINETICS OF ALUMINUM EXTRACTION WITH DI—2-ETHYLHEXYL PHOSPHORIC ACID

The kinetics of solvent.extraction of aluminum with di-2-ethylhexyl phosphoric acid(DEHPA)in n-heptane have been studied in a constant interfacial area cell.A HC1-KHC8H404(potassium biphthalate.KHL)buffer solution was used to maintain a constant pH during extraction.The effects of the concentration of aluminum,pH,the concentration of the extractant,the interfacial area and the temperature on the extraction rate were investigated.A method has been invented to determine amont of the extracted aluminum in the organic phase with 8-hydroxyquinoline.Based on calculation of the coordination states of the aluminum ions and their contribution to the reaction rate,a raaction mechanism which includes two main reaction paths,has been proposed to describe the process.One path starts from Al(H_(2)O)6^(+).and the other starts from Al(H_(2)O)6^(+).The reaction could take place both in the aqueous phase and at the interface.The main reaction region could be changed as the conditions of extraction were changed.When[HA]<0.03 mol/L the process was controlled by the interfacial reaction,and when[HA]>0.03 mol/L it was shifted to a homogeneous aqueous solution reaction.

CHRONOABSORPTOMETRY FOR THE DETERMINATION OF KINETIC PARAMETERS OF ELECTRON TRANSFER REACTIONS USING LONG-OPTICAL-PATH ELECTROCHEMICAL CELL

A single potential step chronoabsorptometric method for the determination of ki- netic parameters of simple quasi-reversible reactions is described.It is verified by determining the kinetic parameters for the electroreduction of ferricyanide.A long-optical-path electro- chemical cell with a plug-in electrode is used.The thickness of solution layer is 0.55 mm